Page 2 of 3 FirstFirst 123 LastLast
Results 36 to 70 of 85

Thread: Choosing power tubes?

  1. #36
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Some of that definitely does sound good, especially the "more girth at low volumes" thing... Plus, it's a chance to learn some more! I did try the higher value pF cap, and didn't like it as much as what's there now... But the rest sounds good! Thanks, Chuck!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  2. #37
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Quick update:

    Chuck, I raised the cap to the PI to a .02 & the Volume to a 250pF. I like it, adds some Fendery bottom to it; I'll see if the intended buyer likes it, it's an easy enough swap if he likes it brighter. The Tone control is a BIT less interactive, which is nice.

    So, here's the fun part, and a caution to builders: in the process of swapping the caps, I nicked one of the other caps (a Mallory 150) on the underside with my iron and exposed some innards. But I didn't see it, cuz it was upside down. So after doing my cap swaps, I turn it on. It's humming as I raise the master, and the pot is scratchy. One of my 6V6s begins to redplate. Huh. DC on it, but how? I didn't mess with THOSE caps! So I check for DC on the grids of the tubes - 120VDC! Wow!

    Looking at the schem, I figure it's only a limited number of ways for DC to get THERE so I started checking for leaky coupling caps - the 2 feeding the power tubes. Both of them with 120V on the grid end, though with one of them, the voltage drops as I turn the pot. So of course, the last cap I look at, I turn it over and see the gaping hole in the side and the aluminum foil showing... replaced and all is good. Also dropped SOMEthing in the Volume pot to make it act up; a simple swap and we rock again!

    New filter can (525V) is on order, along with rubber feet & more pF caps. I appreciate the lessons I learned in diagnostics, putting some of Jack Darr's book into practice.

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  3. #38
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    And there's still the tone cap to play with... .015uf or .01uf will trim it's effect and add a little low mids to the overall tone (for better or worse). If you like the affected frequencies now you could also use a smaller tone pot and fixed resistors to trim it's range. Like a 100k pot with a 4.7k resistor to the ground. Lot's of options to trim up the performance to idealize intuitive use.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  4. #39
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Just wanted to say "Thank You All!"
    I think this design is a real keeper. The intended buyer described it as "Ferocious!" and my audience of reviewers for a scholarship audition remarked "you MADE that? Wow!" Now I just hope the intended buyer actually goes through with it and keeps his word; 8 weeks is NOT so long a wait for a custom-built amp that you forget your commitment and decide to buy a Kemper instead... > And I don't need another amp, I need cash!

    Anyway, great amp, thanks for all the help & tweaking ideas! I just drew out the schem with updates & voltages this morning for reference!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  5. #40
    "Thermionic Apocalypse" -JT nickb's Avatar
    Join Date
    Dec 2009
    Location
    Devon, UK
    Posts
    3,685
    Thumbs Up/Down
    Received: 849/1
    Given: 651/1
    Rep Power
    14
    Quote Originally Posted by Justin Thomas View Post
    Just wanted to say "Thank You All!"
    I think this design is a real keeper. The intended buyer described it as "Ferocious!" and my audience of reviewers for a scholarship audition remarked "you MADE that? Wow!" Now I just hope the intended buyer actually goes through with it and keeps his word; 8 weeks is NOT so long a wait for a custom-built amp that you forget your commitment and decide to buy a Kemper instead... > And I don't need another amp, I need cash!

    Anyway, great amp, thanks for all the help & tweaking ideas! I just drew out the schem with updates & voltages this morning for reference!

    Justin
    Do take & post some pics before you wave it a fond farewell

    0 Not allowed! Not allowed!
    Experience is something you get, just after you really needed it.

  6. #41
    Senior Member
    Join Date
    May 2006
    Location
    Cheshire, UK
    Posts
    2,305
    Thumbs Up/Down
    Received: 605/4
    Given: 313/0
    Rep Power
    16
    Quote Originally Posted by Justin Thomas View Post
    I wouldn't mind figuring out how to make the Tone control a bit less interactive
    It's interactive with the vol pot because it's connected to the vol pot wiper and the impedance from the wiper depends on vol pot setting. You could try connecting the tone pot to the cw end of the vol pot where it will be working with a constant impedance and therefor not be interactive.

    0 Not allowed! Not allowed!

  7. #42
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Hey Dave,

    Aww, dammit! You used the "I" word, which seems to be the main concept in electronics that causes me more "reason to experiment" than just about any other!

    I'm happy with it as is, and so is the intended buyer, but I'll try it out anyway just so I know WHAT the effect is, even if I still don't know WHY the effect is... But I think I can mentally get it. An experiment will help.

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  8. #43
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Hi again,

    So, the intended buyer has backed out (saving for a Kemper "amp") and I am still looking for a buyer. In the meantime, I'm enjoying playing it myself and am taking it to school Saturday to make glorious noise for all my classmates for the next 9 months. There's one guy there who wants a Maz 18; I think he might like THIS one too, and maybe willing to sell his AC30 to do it.

    Anyway, the reason for this post? The original intended buyer said it sounds "as good as my Matchless (Phoenix 35)" and when I let him try it out, he asked what power tubes were in it. I made him guess. He guessed EL34s first, and didn't believe 6V6s could sound that good. Then, I asked him to put it up against his 65Amps Ventura. My amp tore it up, and I told him, "I built my amp using the exact same tubes as your 65, because you said you didn't like 6V6s."

    Whad'ya know, maybe circuit DOES matter more than tubes!

    Another guy in the band said "don't tell him, but your amp sounds BETTER than his Matchless..." Sorry to brag, but I'm just pretty damn proud to hear those compliments, and to know for sure that I can do this! I can say I am the best amp builder in my town, for people who don't play Jazz. Yes, now I'm just gloating!

    Thanks to everyone for your help, I could not have done it without you all!

    Justin

    0 Not allowed! Not allowed!
    Last edited by Justin Thomas; 08-31-2016 at 11:15 PM.
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  9. #44
    Master Destroyer nosaj's Avatar
    Join Date
    Sep 2011
    Location
    Pace, FL
    Posts
    3,395
    Thumbs Up/Down
    Received: 1,206/102
    Given: 172/36
    Rep Power
    12
    Quote Originally Posted by Justin Thomas View Post
    Hi again,

    So, the intended buyer has backed out (saving for a Kemper "amp"... needless to say, I'm a little mad) and I am still looking for a buyer. In the meantime, I'm enjoying playing it myself and am taking it to school Saturday to make glorious noise for all my classmates for the next 9 months. There's one guy there who wants a Maz 18; I think he might like THIS one too, and maybe willing to sell his AC30 to do it.

    Anyway, the reason for this post? The original intended buyer said it sounds "as good as my Matchless (Phoenix 35)" and when I let him try it out, he asked what power tubes were in it. I made him guess. He guessed EL34s first, and didn't believe 6V6s could sound that good. Then, I asked him to put it up against his 65Amps Ventura. My amp tore it up, and I told him, "I built my amp using the exact same tubes as your 65, because you said you didn't like 6V6s."

    Whad'ya know, maybe circuit DOES matter more than tubes!

    Another guy in the band said "don't tell him, but your amp sounds BETTER than his $3000 Matchless..." Sorry to brag, but I'm just pretty damn proud to hear those compliments, and to know for sure that I can do this! I can say I am the best amp builder in my town, for people who don't play Jazz. Yes, now I'm just gloating!

    Thanks to everyone for your help, I could not have done it without you all!

    Justin
    With all of the positive help around how can any of us go wrong. This is one Heck of a community here.

    nosaj

    0 Not allowed! Not allowed!

  10. #45
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Quote Originally Posted by nosaj View Post
    With all of the positive help around how can any of us go wrong. This is one Heck of a community here.

    nosaj
    You know, THIS needs to be the banner for this site, and an open declaration at the top of the FAQs.

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  11. #46
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    Quote Originally Posted by Justin Thomas View Post
    You know, THIS needs to be the banner for this site, and an open declaration at the top of the FAQs.

    Justin
    Agreed

    Incidentally, one of my FAVORITE things is to be at a gig where a good player is using one of my amps. That's when you REALLY get to hear it.

    0 Not allowed! Not allowed!
    Last edited by Chuck H; 09-01-2016 at 02:39 PM.
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  12. #47
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Update! I still have the amp, I love playing with it, and what I'm going to do (slowly and as time allows) is try out some of the various options in this thread, to learn for myself the various impacts of changes, etc. Maybe in the process, the amp will become more "mainstream" and sound good to a wider audience. And on multiple hearings, it is a little bright. Or, the tone control seems to only have effect between 0-4; more useful range, yay. So for now I'll still call it a work in progress. Will post if anything dramatic happens!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  13. #48
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    Fine tuning for a more gen pop/commercial aspect is one of the most frustrating things I've had to face. It's also rewarding when it works out that you still like the amp after any redesign. I've never had an amp design make it to market (on a commercial level), but I've dialed one in for that purpose. The things that you begin to consider once your head is in that place will invariably be things you need to learn more about. That's not all bad. It's good to obsess a little in the spirit of perfection. Pride can be hard earned and a just pleasure or presumed and an ugly sin. You don't seem presumptuous

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  14. #49
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    I'm not "producing" anything more than once, so... yeah, each one has been a request - "hey, can you build me an amp?" Erm, okay... the first was for me without intent to sell, but I sold it anyway. So each of these was for the individual, 3 of them loosely Spitfires, and one "Voxange." This last one was a response to "Here's what I don't like about my boutiqe amp," and partially an "I'll show you!" move on my part.

    I saw a comment in another thread about crossover distortion due to cold bias sounding "reedy," and I thought, that could be good, too... I don't know - maybe we measure all the fun out of the amps we build, because it's not "right."

    Always room for improvement... the last comment I received was, "it makes my guitar sound tinny..." Well, MY guitar, the only one I have to test with, is not your average Telecaster, and, did you even move the knobs from where I left them, Beavis? But I guess nobody likes to turn the knobs to an extreme appoint, nonmatter how it sounds. But as Enzo says, don't worry about the position of the knob... oh, if only it were that easy!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  15. #50
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    Getting cut is the $h!ts. The first design I presented to Dean Markley was a TrainWreck-ish type thing that I DESIGNED BEFORE ANYONE KNEW THE TW SCHEM. Anyway... The tone controls work as distortion modulation controls and have very little effect on the final EQ. Dean fricken Markley said it was "lacking" because the EQ controls didn't adjust the final listener image. For us, here in guitar amp land this is common and expected. For Dean it was a flaw. And that's an accurate assessment for the average bone head, bedroom guitar kid. He wasn't looking for "the" amp. He was looking for an amp he could sell. THERE IS A DIFFERENCE !!! Coming to terms with that, and being willing to send and police designs overseas !@#$* has proven to be troublesome for me

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  16. #51
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Spent some time on this this weekend; main changes were changing the 500K tone control to a 250K and dumping the bright cap on the Volume, and made both of the caps on the PI .02uF. I didn't realize the one in the actual signal chain already was, but the one to ground on the other side was still a .01. I may revisit that EF86 preamp and twiddle the voltages there, mainly that the screen is pretty high, and I may tweak the 6V6 screens too.
    Chuck, wasn't quite sure what you meant in post #38 by "100K pot with a 4.7K to ground." Is that basically wired like a Fender's "Bass" knob, and the 4.7K is the "Mid Control?"
    There's a lot of gain here, and it can get kind of ratty at the extremes (as in, everything on 10), but I'll have more chances later to really dial in sounds and see if I like it. But moving in the right direction. Thanks again for all the help!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  17. #52
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    Without going back and re reading the whole thread...

    I was probably outlining a possible way to make the tone control more concise. IIRC you mentioned something about not being able to use it beyond some low setting and not being good for much all the way down. So changing to a smaller pot and adding a resistor to the ground connection should put the useful range of the control across a wider range of motion without the useless extremes at either end.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  18. #53
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Chuck,

    Okay, that makes sense. I don't think that's quite what I was going for, because I do like the interaction between the knobs at the extreme settings. I may tweak some tube parameters a bit; it just seems a little thinner than I would like, maybe brittle? . But pulling the Bright cap on the Volume helped quite a bit. I know nothing will blow up, so it's all good. It definitely sounds better with the Master up high, and the Volume up. But, that's why I only build small amps!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  19. #54
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    No. Nothing will blow up. That's one of the fun things about preamp voicing. You can sort of fly with the "WTF, I'll try it and see." attitude :thumbsup"

    As for brittle and bright caps, etc... Keep in mind that it's always possible to "remove" too much top end later in the circuit. Sometimes something that sounds "ugly" voiced early in the amp sounds fine if you mitigate HF in a later circuit and the advantage is that clipped harmonics are being generated, and then "EQ'd" to a more pleasant final tonality. Keeping the HF in early in the clipping stages is usually desirable. Taking too far isn't, but that's where some of the mojo and mind numbing tweaking come in. You could try to keep the HF in the early stages and voice later stages to balance the final EQ and find that you get to keep your harmonics without the harshness.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  20. #55
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    The nice thing about tube tech in general is that it's a lot harder to blow up, period. And there's usually a warning sign. The "silent and sudden death" syndrome isn't quite so bad. And I like to actually "see" my guitar going through the tubes, watching glowing screens, changing fluorescence, etc. One of my favorite things I watched was the tube voltage regulator in an old Leslie cabinet, powered with 2 metal-based KT88s... that was pretty damn sweet... lookedlikesomekind of Martian technology! I should go back to that church & leave my number!

    Chuck, I like the way you give "non-answers" and generalities, without doing a paint-by-numbers approach. You state the goal, and just say, "try these three things..." I learn a lot by trial and error, especially the error part, and learn something in the process. And the worst thing I've sacrificed so far is an E-cap that I over-voltaged. Well, that and an EH-6V6...

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  21. #56
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Hey again all,

    I've done some good bit of reworking on this amp, after another friend tried it and said "it makes my guitar sound brittle." So after much fiddling:

    1. Dr. Z style Treble & Bass controls.
    2. Ditched the Master Volume. For 15W? Really?
    3. Many cap changes, too many to detail. But I took the Bright cap out completely. I may decrease the coupling caps from PI to power tubes...
    4. I put in a big fat sag resistor, 250R/20W. Also changed the 6V6 bias R to 500R.

    Much better. Using JJ 6V6s, I have the BFR dropping about 20V, and the plates are at a nicer 420V or so. I didn't check other stuff, figuring all dropped accordingly. By my math I think I could get away with a 5W BFR, but even a 10W 500R got too hot to touch, so the big guy stays. The 6V6 plates seem to be throwing about 12.5W, I know some of that is screens too, but I didn't notice any redplating, so... I'll keep a eye on it. No, it WOULD be nice to use a 5W or 3W cathode resistor, but this thing sounds a serious treat with 6L6s, so I think even 5W might be a bit low there, too! Oh well.

    In my trials and tribulations, I DID bust my PI tube's socket, so that gets replaced, too (PTP - the horror!). Also need to buy better octal sockets than what I had - with 6L6s, the sockets allow a lot of sideways motion, and due to existing chassis layout, it may be way to easy for the tubes to hit the OT. I <AM> going to try some EL34s in it, too, monitoring the heaters, of course.

    Again, thanks to all who've helped on this adventure!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  22. #57
    Senior Member
    Join Date
    Jul 2011
    Location
    Adelaide, South Oz
    Posts
    751
    Thumbs Up/Down
    Received: 85/0
    Given: 4/0
    Rep Power
    9
    Justin,
    Good work, if I could suggest a couple of minor changes for possible reliability improvements:
    1) 1K5 grid stops are not enough for a 6V6. I suggest 10K.
    2) The JJ 6V6 are fairly tolerant of runing at higher voltages but you may run into problems with other 6V6. I would suggest doubling the 6V6 screen resistors to 1K and using 5W resistors. Actually if you have time/inclination to try an experiment I would add 2 x 1K in series on each 6V6 screen and see if you like the amp better that way or with a short across on of the 1K on each tube (that is do you like it better with 1K rather than 2K), if so then fit 2K2 5W as final value.
    Cheers,
    Ian

    0 Not allowed! Not allowed!

  23. #58
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Hey Ian,

    Wow, it's kind of an honor... I'm open to trying stuff until it's JUUUUUUUUUST right, honestly. No buyer yet, so I'll tweak it. I have no inclination to run other than JJs in it, knowing the operating conditions. Right now it has reissue TS5881, and takes 6L6 too. I tried some JJ (GT-branded) EL34, but they were noisy - the internal arcing kind of noisy, so they got pulled out fast.

    I really like the Z-style tone stack, and it was funny. The first thing I did before that conversion was to simply disconnect the MV, leaving only the V & T controls. And sure enough, volume would drop out in certain spots - parasitics! Which may explain the thin brittle sound ot the first iteration. Yet that didn't happen with the MV (crossline) installed... oh well, no scope, so it's always an adventure. I've got it running through a Rocket 50 (Celestion) now, in a gutted GU12 cab. So it sounds good, but through the intended buyer's Matchless & my buddy's AC30 reissue, it sounds amazeballs. So, SPEAKERS REALLY MATTER!!!

    I'll try your suggestions out when I can & report back, but for the next 10 weeks, I'll be going to Canadia & Ireland, so... Yay? First international travel ever. Amp goes to Canadia with me. Maybe it'll sell.

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  24. #59
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Hi all again,

    Foreign travels are currently over (for now), so I'd like to follow up on this...

    Currently the amp is as it was in post #56 above, and then I made the changes Ian proposed in post #57. The current power tubes are TS RI 5881s, a JJ 12AX7, & a Seimens EF86. I like this one pretty well now, and this amp teaches me that speakers are also VERY important.

    I think it sounds great, but it's not quite MY sound. Which makes sense as I built it for someone else... I've got another potential buyer looking at (and my Prosonic), so here's to crossing fingers. I guess my only remaining question is,

    Do we think this thing is safe for use with JJ 6V6s, 5881 reissues, and 6L6GC-styles? I'm not thinking KT66/EL34 in that mix, just "American" tubes... was just wondering if the changes Ian proposed would make any of my proposed tubes explode. I don't see them as that radical of a change, and I also don't feel like or have the luxury of torture-testing the amp, tubes, or my ears right now...

    Off to the attic for my next project!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  25. #60
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    I think you're going to have to plug the different proposed tubes in to see how they all bias with the existing cathode resistance. You may need to add a "big bottle/small bottle" switch so the 5881's (modern?) and 6L6's can be run hotter and avoid excess crossover distortion? 750R is certainly higher (cooler) than I've used with 6L6 types at 420ish volts. That doesn't mean it's a problem. It just means I'd prefer a measurement to know if it were me.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  26. #61
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Doh, should add - I've got a 500R shared cathode resistor for both power tubes, so it'd be 1K per. Right now it's got RI TS 5881s in it, which promptly cooked when I put them in my Prosonic with a shared 220R. But I guess I'll suck it up & do the work...
    Any issues with the grid stops being 10K & screen droppers @ 1K with all types? That is venturing into territory I won't pretend to grasp!

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  27. #62
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    16,026
    Thumbs Up/Down
    Received: 2,836/4
    Given: 3,322/0
    Rep Power
    31
    The 10k stoppers and 1k screen resistors are fine. In fact I had a project once with 10k stoppers, 1k screen grid resistors and 470Vp that ate three pairs of el34's. Two were new, but I suspect defective and the other was old/used though. I was out of el34's so I dropped in some 6L6's I had and was able to finish the project. Complete with extreme, sustained heavily clipped torture testing. The final tubes for that amp ended up being Ruby branded Suguang el34b's that sounded terrific (if a little too microphonic).

    I've used 500(+?)R resistance for a pair of 6L6's at 420V. That amp went through many changes and one version had one of the better cranked up tones I've ever achieved. So clearly odd distortion artifacts like crossover distortion weren't a problem.

    DO plug in the other tubes anyway for your own satisfaction. If 500R presents an acceptable bias for the JJ6V6's it should be plug and play for the different tube types. If your sockets are wired correctly and your heater winding is up to it you might even be ok with el34's or other Euro tubes.?.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  28. #63
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Okay, measurements:

    JJ6V6Ses: running about 12.25W per tube, or about 87%. No problem there...
    TS 5881RI: running about 13.62W per tube, or about 60%. No problem there, assuming they're true 23W tubes as the originals were.
    JJ6L6GCs: running about 13.2W per tube, or about 44%. Cold for sure, but I doubt we'd need any more power, given all the griping about "you're too loud!" we get as guitar players.

    I think there's enough wiggle room with the first two to not worry too much, though I guess I'd stick with the 5881s most of the time. The other nice thing about that 500R cathode resistor? It makes the math really easy!

    Granted, all of these are not "Listened To and Took Detailed Notes" or anything, just quick plug-&-chug.

    Now, as an aside:
    I've got a set of GT-branded "GTE34LS" (aka: 6CA7) [That's exactly what's printed on them] that are rebranded JJs, which I'm thinking are really JJ E34Ls, which I believe are supposed to bias using something more like 6L6 voltages, instead of standard EL34 voltages? I tried them for about 30 seconds, but given the funny noises that came out of my speaker I wasn't inclined to leave them in very long. Not even long enough to check the heater voltages, which I'm sure would be okay - this thing has a really beefy Schumacher tranny set. I don't have any other EL34s laying around, and plenty of "American" style tubes, so I'll blow through those first before buying more variety. Next few amps may be 6W6, 6AQ5, 6BK5, 7591, etc - I picked up a slew of oddballs over the years, super cheap.

    Justin

    0 Not allowed! Not allowed!
    Last edited by Justin Thomas; 05-12-2017 at 08:10 PM.
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  29. #64
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Another update:

    After a few more months and continued readings from others with the same problems, I dug up some old Rivera schema, the ones where there's a cap from cathode to (I forget which). Anyway, I tacked a 500oF on the EF86, and plugged it into my Bassman 2x15" and it sounded amazeballs.

    When I got home I plugged it back into my cheapie Celestions Rocket 12, and it's better, but still a bit harsh in the high end. So I either need to seriously break in that speaker (hasn't seen more than 10 hours of low-volume playing yet) or just get another old Fender cab... I don't know why those old CTS speakers get such a bad rap!

    There are a few bad connections in the preamp that'll need chopsticking, but on the whole, I'm making good (if slow) progress, and this one is becoming something more like what I would personally play out. I'll have to put up pictures of the shell, too... I unwittingly matched the colors of an Irish sunset without being aware of it...

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  30. #65
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Still tinkering with this thing, usually after being inspired by other threads I see here, and trying out the ideas. Latest is messing with the 220k (I'm guessing) grid leaks on the 6V6s. Also, trying to track down some mechanical noises. What did I learn? Seems that tube sockets are not something to cheap out on...

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  31. #66
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    After much enjoyment and frustration, I have elected to go a more "conventional" route - partly due to EF86 issues. I reworked it over today, with a regular 12AX7 preamp. I left the Dr. Z tone controls, but am going to swap them out for something a little more "lossy." This thing has super gain, too much. But I think at the end of the day (or month, or whenever) I'll have something more "me." I learned a lot here, and thanks again to all. I'll check in periodically here with updates.

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  32. #67
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    And, my first iteration (BF Deluxe Normal preamp) results in nothing but a loud BUZZZZZZZZ when the Volume control is advanced, with no trace of a guitar signal... So, once again, we learn, don't work on your amp when you're tired! Wiring check tomorrow...

    Justin

    0 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  33. #68
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    3,331
    Thumbs Up/Down
    Received: 785/6
    Given: 1,578/10
    Rep Power
    18
    Second iteration squeals! Garsh, I love point-to-point! But the buzz is gone. So, now to futz with layout. Knobs work properly, at least.

    Edit: found broken ground in my Tele. Standby...
    Edit Edit: some hum to track down, but LOTS of loud. Sounds like a 2x6L6 Fender should. Probably will have to dump some gain; time to look at some high-gain amps schematics for voltage dividers...

    Justin

    0 Not allowed! Not allowed!
    Last edited by Justin Thomas; 01-09-2018 at 03:07 AM.
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  34. #69
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,909
    Thumbs Up/Down
    Received: 77/0
    Given: 0/0
    Rep Power
    18
    I haven't been following this thread from the beginning, just looked at it today. I was going to ask what you've been using for the preamp pentode and how reliable it's been. Since you're converting over to a twin triode preamp I thought I'd ask -- why did you end up bagging the pentode?

    0 Not allowed! Not allowed!
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

  35. #70
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,909
    Thumbs Up/Down
    Received: 77/0
    Given: 0/0
    Rep Power
    18
    Quote Originally Posted by Justin Thomas View Post
    Sounds like a 2x6L6 Fender should. Probably will have to dump some gain; time to look at some high-gain amps schematics for voltage dividers...
    got and updated schem?

    0 Not allowed! Not allowed!
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Choosing power transformer.
    By Danelectron in forum Theory & Design
    Replies: 19
    Last Post: 12-21-2012, 08:51 AM
  2. One power tube socket is not sending power to tubes in my Mesa Express 5:50
    By Freckles in forum Maintenance, Troubleshooting & Repair
    Replies: 17
    Last Post: 02-11-2012, 02:02 AM
  3. Power tubes glowing and loss of power
    By Bluefinger in forum Maintenance, Troubleshooting & Repair
    Replies: 16
    Last Post: 06-20-2011, 10:25 AM
  4. Choosing a power amplifier
    By frosty55 in forum Music Electronics
    Replies: 0
    Last Post: 06-16-2010, 05:47 PM
  5. choosing tubes help?
    By jaypaul in forum Tubes (Valves)
    Replies: 2
    Last Post: 09-20-2006, 12:39 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •