Page 1 of 2 12 LastLast
Results 1 to 35 of 53
Like Tree1Likes

Thread: Single Ended 6V6/EL34/KT66/6550/KT88 Amp

  1. #1
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54

    New Build: Single Ended 6V6/EL34/KT66/6550/KT88 Amp

    Finished my second "PriestyAMP" project, a single ended amp based on a Blackface Champ aa764. It has the following design features I incorporated:
    - Adjustable Cathode Bias
    - Fan Cooling
    - Foot-switchable "Turbo Knob" feedback lift boost

    Sounds:
    - Sounds best for Rock and Blueswith American sounding 6V6 (JJ 6V6s operating on its limits) or British sounding EL34 (Groove Tubes)
    - Preamp tube Groove tubes ECC83S (Great for Blues to Metal depending on volume setting) or 12AU7 for Jazz/Country (with 6V6).
    - Brutally distorted with ECC83S/KT88 combination
    - "Turbo Knob" gives noticable bite and mid-boost when engaged

    I've probably made tons of errors, which will no doubt be pointed out forthwith by the experts, but I think the Amp plays good, so I'm putting this out there to help any other people looking to try a single ended amp with more than 5 watts.
    Attached Thumbnails Attached Thumbnails schematic-gazeyfier-small.jpg   front.jpg   back.jpg   bias.jpg   internals.jpg   amp-cover.jpg  
    Last edited by priesty; 06-07-2010 at 12:07 AM.

  2. #2
    Member
    Join Date
    Oct 2009
    Location
    Concord, CA USA
    Posts
    23
    That came out really nice, did you build and paint the chassis too?

  3. #3
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Posts
    2,580
    It looks like you started with a hammond chassis and painted it and lettered it yourself. The paint and the lettering looks very good.

    I have a few comments and questions for you.

    1. I like your schematic. Its well drawn, clear to read, and the objects are well proportioned in size. Can you tell me what software you used to draw it?

    2. I like the footswitchable NFB loop. Do you get any pops when you use the footswitch?

    3. Since you're using such a wide variety of tubes, I was wondering if you've given any thought to using a selectable switch for the primary OT impedance.

    4. The lettering looks nice. Am I correct in assuming taht its a peel and stick sheet that you put through a laser printer? I'm interested in hearing about it.

    Looks like a nice build. Congrats!

  4. #4
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by bob p View Post
    It looks like you started with a hammond chassis and painted it and lettered it yourself. The paint and the lettering looks very good.

    I have a few comments and questions for you.

    1. I like your schematic. Its well drawn, clear to read, and the objects are well proportioned in size. Can you tell me what software you used to draw it?

    2. I like the footswitchable NFB loop. Do you get any pops when you use the footswitch?

    3. Since you're using such a wide variety of tubes, I was wondering if you've given any thought to using a selectable switch for the primary OT impedance.

    4. The lettering looks nice. Am I correct in assuming taht its a peel and stick sheet that you put through a laser printer? I'm interested in hearing about it.

    Looks like a nice build. Congrats!
    Hi Bob in answer to your questions:

    1. Schematic drawn at great length on MS Word. If you make a few standard components and copy and paste, you can make it look good, but it does take time!!

    2. The foot-switchable NFB boost has no pops at all, I put this down to the fact the stock NFB resistor (2700ohm) is always in series with the switch. There is no "opening" of the NFB loop, just switching in the high value pot. The foot switch is actually closed for the non-boost option, shorting out the "Turbo knob". With no footswitch, the "Turbo knob" is active for use for say, practice or recording. Important to use a stereo insulated jack for this!

    3. Impedance - the Hammond 125FSE has multiple tappings on the seondary, I use a 3 position marshall style impendnace selector to alter impedance as required.

    4. As you noticed, used a Hammond blank chassis and cage, cut holes to suit. It was powder coated by a friend who does it professionally. Lettering was waterslide decals printed on laser printer, like old Airfix kits!

    Thanks again for your comments!!!
    Last edited by priesty; 06-09-2010 at 12:18 AM.

  5. #5
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by maxwedge View Post
    That came out really nice, did you build and paint the chassis too?
    Maxwedge, thanks for the comments! As mentioned above, the good people at Hammond made the chassis and cover (Hammond Aluminium 1444-22 12x8 chassis, steel cover of same 12x8 size). George at Shetland Powder Coating did the painting after I'd cut all the chassis holes. He used a flexible epoxy as it is a more forgiving finish, less brittle/flaky.

  6. #6
    Senior Member
    Join Date
    Jan 2009
    Location
    Los Angeles
    Posts
    294
    Great looking amp! Thanks for all the good ideas.

  7. #7
    Supporting Member overtone's Avatar
    Join Date
    Jul 2009
    Location
    frankfurt + london
    Posts
    67

    airfix

    thanks for sharing that with us. I did not know that there are more elastic types of powder coating out there.

    Having just given up using MS Word for texts and after twenty-five years of using CAD and I can tell you that I am totally amazed that you drew that schematic on MS Word. Hats off to you Sir!

    "Airfix" decals = Lasertrans, am I right?

  8. #8
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by overtone View Post
    "Airfix" decals = Lasertrans, am I right?
    Overtone - Airfix was/is a type of scale model plane company here in UK, the insignia were always on waterslide decals, hence why I mentioned Airfix! Here is the place I got the paper from: Inkjet Papers and Fabrics, Window Stickers and Other Arts and Craft Materials

    Glad to share my "research", especially on this forum seeing I got lots of help from here with my first amp!

  9. #9
    Supporting Member jmaf's Avatar
    Join Date
    Apr 2009
    Location
    Earth
    Posts
    1,174
    priesty, very kind of you sharing all this with us. not to mention your build, superb.

    the decal paper tip just gave one of those eureka moments...i've been using silk screening and it's such a cumbersome process.

    do you or anyone else know if one can safely apply automotive polyurethane varnish on top of the decal to protect it? or will it destroy the decal?
    "Tell them I said something." - Pancho Villa's last words
    For Portuguese speakers: Compreenda seu Amplificador Valvulado

  10. #10
    Supporting Member tubeswell's Avatar
    Join Date
    Feb 2007
    Location
    Wellington NZ
    Posts
    3,903
    Very cool looking amp there priesty 8-)
    Building a better world (one tube amp at a time)

  11. #11
    Supporting Member overtone's Avatar
    Join Date
    Jul 2009
    Location
    frankfurt + london
    Posts
    67
    Quote Originally Posted by jmaf View Post
    will it destroy the decal?
    jmaf,
    I have used "CLOU" nitro-cellulose, which is intended for joiners and cabinet makers in Germany, over "Lasertrans" decals on a guitar headstock with acceptable results ...well it was perfect for the low-tech, "warts and all" feel that I was going for!
    It was before I had an air compressor, so I used a brush with some care. It did smudge a little in places where I became careless. It has been fine sitting on there a year now and has seen some temperature change abuse too.
    The edges of these kind of decals will show up in certain light conditions, so the brush was really useful to build up a few layers around the decal first helping to feather-the-edge-in a little. You will still see the edge if you are looking for it.
    Take a look at the images to see if the smudging is acceptable for you and bear in mind that an air gun should give a much better result.
    Attached Thumbnails Attached Thumbnails overtone-tele-.jpg   overtone-tele-backside.jpg  

  12. #12
    Member Hurricane's Avatar
    Join Date
    Apr 2010
    Location
    Coachella ( Coachella Fest anyone ? )
    Posts
    34

    Question Output ?

    Excerpt :

    Quote Originally Posted by priesty View Post

    I've probably made tons of errors, which will no doubt be pointed out forthwith by the experts, but I think the Amp plays good, so I'm putting this out there to help any other people looking to try a single ended amp with more than 5 watts.
    ================


    So - - What is the out put per tube choice ?

    Thanks and wow what a nice job I'm inspired to make one now

    Hurricane Ramon

  13. #13
    Alf
    Alf is offline
    Senior Member
    Join Date
    May 2006
    Location
    Netherlands
    Posts
    206
    That's a fantastic looking amp Priesty !! And does it sound like you hoped for as well ?

    I'm getting very curious to hear what it actually sounds like. Could you do a clip ?
    I'm planning to do a SE amp myself, I have already all the hardware including a Heyboer OT but haven't got the time right now.

  14. #14
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by Alf View Post
    That's a fantastic looking amp Priesty !! And does it sound like you hoped for as well ?

    I'm getting very curious to hear what it actually sounds like. Could you do a clip ?
    I'm planning to do a SE amp myself, I have already all the hardware including a Heyboer OT but haven't got the time right now.
    Alf - Amp is with a friend who I built it for, I will get a clip next time I visit him.

    Hurricane - I havn't been able to borrow a scope to check output, but it was so loud when trying it through a Marshall 4x10" cab that you couldn't be heard when shouting to the guitarist! Amp runs with B+ of 440V at anode load of 5K and withEL34, about 30mA idle current.

  15. #15
    Alf
    Alf is offline
    Senior Member
    Join Date
    May 2006
    Location
    Netherlands
    Posts
    206
    I will get a clip next time I visit him.
    Looking forward to it .

  16. #16
    Member Hurricane's Avatar
    Join Date
    Apr 2010
    Location
    Coachella ( Coachella Fest anyone ? )
    Posts
    34

    Output ?

    Quote Originally Posted by priesty View Post
    Hurricane - I havn't been able to borrow a scope to check output, but it was so loud when trying it through a Marshall 4x10" cab that you couldn't be heard when shouting to the guitarist! Amp runs with B+ of 440V at anode load of 5K and withEL34, about 30mA idle current.

    =======================

    Looks like a really ball buster of an amp and you made it rip up on a 4X12 cab - - I am interested

    Hope you can scope it even if its' only academic at this point

    easy man :

    Hurricane Ramon

  17. #17
    Junior Member
    Join Date
    Feb 2009
    Location
    France
    Posts
    3
    I like the adjustable cathode bias , i bet its sweet , you've put your own stamp on the looks too , well done mate .
    BTW , I put the hammond 125fse in a 600 champ at the end of changing to a weber alnico speaker and various cap make tries and changes . That OT really opened the whole amp up , its nice isn't it ?
    My father said " don't let the world change who you are" i was surprised as i felt it was probably a very good idea

  18. #18
    Supporting Member jmaf's Avatar
    Join Date
    Apr 2009
    Location
    Earth
    Posts
    1,174
    priesty, one question please, if I may, about the decal work.

    The decal paper is opaque on the back. How do you align the decal over the chassis so it's perfectly aligned horizontally and with the pots, etc? If you don't mind sharing that little secret, of course.
    "Tell them I said something." - Pancho Villa's last words
    For Portuguese speakers: Compreenda seu Amplificador Valvulado

  19. #19
    Supporting Member jmaf's Avatar
    Join Date
    Apr 2009
    Location
    Earth
    Posts
    1,174
    Thanks for sharing, overtone. I'll try some experiments, hopefully soon if my day job allows me, and will share the results as well.
    "Tell them I said something." - Pancho Villa's last words
    For Portuguese speakers: Compreenda seu Amplificador Valvulado

  20. #20
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by jmaf View Post
    priesty, one question please, if I may, about the decal work.

    The decal paper is opaque on the back. How do you align the decal over the chassis so it's perfectly aligned horizontally and with the pots, etc? If you don't mind sharing that little secret, of course.
    Jmaf - I call it my "Laser Eye"! Seriously though, the beauty of water slide decals is they don't stick instantly, and so can be repositioned (literally slid about) until you are happy with the positioning.

  21. #21
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by spark_right View Post
    I like the adjustable cathode bias , i bet its sweet , you've put your own stamp on the looks too , well done mate .
    BTW , I put the hammond 125fse in a 600 champ at the end of changing to a weber alnico speaker and various cap make tries and changes . That OT really opened the whole amp up , its nice isn't it ?
    Spark_right, you are right, the 125FSE is a great unit, I'd use it again. It goes to show that Big Iron = Big Tone!

  22. #22
    Supporting Member jmaf's Avatar
    Join Date
    Apr 2009
    Location
    Earth
    Posts
    1,174
    Hi priesty, you can slide them around after you've removed the backing paper? I've never used decals and would like to try it, I'm sorry for the newbie questions.
    "Tell them I said something." - Pancho Villa's last words
    For Portuguese speakers: Compreenda seu Amplificador Valvulado

  23. #23
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by jmaf View Post
    Hi priesty, you can slide them around after you've removed the backing paper? I've never used decals and would like to try it, I'm sorry for the newbie questions.
    Yes, slide off the backing paper onto the surface you want to put them onto and then slide around to get precise location. You might need to leave it a coupel of hours to dry, depending how warm/cold it is. Using tepid water helps too.

  24. #24
    Senior Member RWood's Avatar
    Join Date
    Apr 2009
    Location
    Richmond, VA
    Posts
    294
    Thanks for all the useful info and great pics - really interesting.

    Could I ask where you sourced the 1K 3W bias pot? I have been looking around and all I see are very expensive ($30 and up) choices.

    I like how you made the bias meter switchable, too.

  25. #25
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Quote Originally Posted by RWood View Post
    Thanks for all the useful info and great pics - really interesting.

    Could I ask where you sourced the 1K 3W bias pot? I have been looking around and all I see are very expensive ($30 and up) choices.

    I like how you made the bias meter switchable, too.
    I use Farnells for my components, you can use their website to select the exact specs you need for the components. I'm in the UK, but I think they have US stock too. Of the top of my head, the bias pot was about 7 (circa. $10).

  26. #26
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Hi all,

    I've finally got some video footage of the Gazeyfier in action, enjoy!

    YouTube - gazeyfier

    Priesty

  27. #27
    Senior Member
    Join Date
    May 2007
    Location
    Silicon Valley ; USA
    Posts
    1,093
    I have a couple of comments.. I like the fact you put your fuses on the A/C primary.. If you could find a power switch that was double-pole for both A/C hot and A/C return, that would be spot-on for handling primary power.. Otherwise, looks and sounds very good....

    -g
    ______________________________________
    Gary Moore
    Moore Amplifiication
    mooreamps@hotmail.com

  28. #28
    Lifetime Member
    Join Date
    May 2006
    Posts
    3,452
    Quote Originally Posted by mooreamps View Post
    I have a couple of comments.. I like the fact you put your fuses on the A/C primary.
    ????
    As opposed to putting them on top of the cabinet or in the volume pot wiper circuit?? Or what?

    OF COURSE at least one fuse goes in the AC power primary. It's a matter of safe AC power wiring to always use a primary fuse, unless you have tested and type-certified the power transformer to have limited fault currents and heating. Not putting at least one fuse in the primary is a huge safety/fire hazard.

    Saying "I like the fact that you put your fuses on the A/C primary." is like saying " I like the way that you keep your rifle muzzle pointed away from other people and yourself." This is one of those little IQ tests that Mother Nature sets out for us. The punishment for failing the test is often removal from the gene pool.

    Two fuses is more problematical. One of these primary fuses will always blow before the other, as there is no good source I can think of for matched fuses. So if and when one blows, you now have to examine both to find out which one blew, and to find out of the second one was damaged by the overcurrent. If you have a line/neutral power line setup, the fuses always go in the hot/line side of the AC power.

    If one is going to put in more than one fuse, it would be smart to put one fuse in each secondary winding. This protects the power transformer, the single costliest item in most amps, from secondary overloads, as no primary fuse can do. Don't you agree?

    If you could find a power switch that was double-pole for both A/C hot and A/C return, that would be spot-on for handling primary power.
    Yes, breaking both line and neutral is a good idea for any power setup, but it's practically mandatory where the AC power line has only floating lines on both side, neither being a neutral. If you have only two wire power, a blown fuse can still leave the amp insides hot to the remaining power wire. It's important to know WHY you do things too.

  29. #29
    Senior Member
    Join Date
    May 2007
    Location
    Silicon Valley ; USA
    Posts
    1,093
    Quote Originally Posted by R.G. View Post
    ????


    If one is going to put in more than one fuse, it would be smart to put one fuse in each secondary winding. This protects the power transformer, the single costliest item in most amps, from secondary overloads, as no primary fuse can do. Don't you agree?
    Ahmmmmmm, no.. It's actually a great source of entertainment for my colleges at work ; when they hear things like ; when the short circuit current is higher on the primary winding than the secondary winding, yet some people choose to put fuses on the secondary winding..

    -g

  30. #30
    Member Hurricane's Avatar
    Join Date
    Apr 2010
    Location
    Coachella ( Coachella Fest anyone ? )
    Posts
    34

    Thumbs up Some Crunch !

    Quote Originally Posted by priesty View Post
    Hi all,

    I've finally got some video footage of the Gazeyfier in action, enjoy!

    YouTube - gazeyfier

    Priesty
    ================================

    Simply put .........Wow a seriously piece of work with an impressive sound .

    Lets see and here more

    HR

  31. #31
    Senior Member ThermionicScott's Avatar
    Join Date
    Dec 2009
    Location
    SW CR IA US NA PE
    Posts
    463
    Looks very nice, and although the microphone clipped a lot, you can hear that it's a good-sounding amp.

    I couldn't help but notice the 1M grid resistor on the output tube. While cathode bias is more forgiving than fixed bias, that's a lot higher than the 220k recommended for KT88, or the 500k recommended for 6L6/KT66. It might be a good idea to reduce that value in case you encounter an unstable or gassy new-production tube.

    - Scott

  32. #32
    Supporting Member
    Join Date
    May 2006
    Location
    Staffordshire UK
    Posts
    2,166
    For anyone in the EU who's inspired to try a similar project, Ampmaker has a tempting kit that's along the same lines, see
    Double Six 1W/6W/12W amp

  33. #33
    Supporting Member
    Join Date
    Nov 2009
    Posts
    54
    Gents,

    Thanks for your comments, nice to get some feedback.

    If I can clear up my rationale for the Fuses and Mains Switching:
    Fuses: To save space on the build, I used an IEC mains socket with integral fuses on live and Neutral. These are located in a fuser "Drawer" included in the socket body. SCHURTER 4301.0501 from Farnell.
    Switch: I don't know about other countries, but in the UK supply feed Neutral is tied to Earth and is always identifiable from Live. Morgan Jones book "Building Valve Amplifiers" he does mention that two pole mains switch could be fitted across Live and Neutral, but draws atttention that in such an arrangement, the shorting of the live contact due to mechanical failure would appear to be OK, as item would be still switched on and off by the Neutral half of the switch, but in both "Off" and "On" states the Live supply is still present. Morgan Jones reccomended switching the live circuit only as this was the safest and most reliable if the live/neutral polarity is known.

  34. #34
    Lifetime Member
    Join Date
    May 2006
    Posts
    3,452
    Quote Originally Posted by mooreamps View Post
    Ahmmmmmm, no.. It's actually a great source of entertainment for my colleges at work ; when they hear things like ; when the short circuit current is higher on the primary winding than the secondary winding, yet some people choose to put fuses on the secondary winding..


    I think that says more about you and possibly your colleagues (look it up: colleague not colleges) than it does about the electronics.

    OK. Shall we delve into this technically again? I did the math and pulled up the tech references for you. But I can do it again.

    Did you not get that primary fuses are for protecting (a) the box and electrical system against fires and electrical safety issues and (b) only secondarily protecting the power transformer?. And did you not get that fuses **also** on the secondaries are to protect the power transformer? These are two different purposes, as I explained to you at some length.

    The size of the short circuit current on one winding versus the other is not an issue. The objectives in the use of the fuses is an issue. You really do need to be able to embrace more than one idea at a time, Gary.

    Did your colleges [sic] think about both uses of fuses? I'm guessing that if your colleges [sic] are as good as you think they are, they'd be able to follow the two different uses. And how to size them. If you presented the issue that way, and not in a way that begged the question.

    Do you need me to copy the write up from the earlier set of posts that you just decide not to talk about any more. I can do that if that would help you understand.

    Or would you rather not talk about this issue at all?

  35. #35
    Lifetime Member
    Join Date
    May 2006
    Posts
    3,452
    Quote Originally Posted by priesty View Post
    If I can clear up my rationale for the Fuses and Mains Switching:
    Fuses: To save space on the build, I used an IEC mains socket with integral fuses on live and Neutral. These are located in a fuser "Drawer" included in the socket body. SCHURTER 4301.0501 from Farnell.
    That's cool. If you're using hardware that has a dual-fuse setup, there's no reason to go trying to defeat it. However, the fuse in the line/hot side is the one that's critical. I have no issue with that at all.

    Switch: I don't know about other countries, but in the UK supply feed Neutral is tied to Earth and is always identifiable from Live.
    Yes, it's that way in the USA as well. However, we also have to worry about the electricians that wired the buildings getting live and neutral mixed up in the sockets, and so I always treat live and neutral as though they may be flipflopped in power switching. I recommend breaking both of them with the power switch. I think your decision to do so is good practice.

    Morgan Jones book "Building Valve Amplifiers" he does mention that two pole mains switch could be fitted across Live and Neutral, but draws atttention that in such an arrangement, the shorting of the live contact due to mechanical failure would appear to be OK, as item would be still switched on and off by the Neutral half of the switch, but in both "Off" and "On" states the Live supply is still present. Morgan Jones reccomended switching the live circuit only as this was the safest and most reliable if the live/neutral polarity is known.
    Yeah, I'd agree with that - with the caveat that "if the live/neutral polarity is known" is a big issue. I have come to not trust electrical power wiring. In my experience, about 5-10% of new construction outlets are wired with line and neutral switched. I carry one of the plug-in outlet testers with me for just this issue when I'm setting up. I highly recommend it for everyone.

    Also, the two-pole switch failing with one side shorted is possible, although I think that one pole fail open is more likely. That is just my opinion and experience and is not by any means definitive.

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. ideas about single ended amp design - new to amps
    By black_labb in forum Theory & Design
    Replies: 10
    Last Post: 11-21-2012, 04:11 AM
  2. 6x 6550/kt88 bass amp build
    By black_labb in forum Build Your Amp
    Replies: 22
    Last Post: 02-02-2010, 10:59 PM
  3. single ended tube amp help
    By duffy878 in forum Maintenance, Troubleshooting & Repair
    Replies: 3
    Last Post: 08-12-2009, 04:09 PM
  4. Single ended 2 x 6V6 in parallel schematic ideas?
    By tubeswell in forum Theory & Design
    Replies: 16
    Last Post: 07-20-2008, 12:08 AM
  5. 6J7, 6F6, 5W4 single ended amp
    By hearforever in forum Theory & Design
    Replies: 6
    Last Post: 07-08-2008, 11:19 PM

Tags for this Thread

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
  •