Results 1 to 23 of 23

Thread: Tone stack effect on volume

  1. #1
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5

    Tone stack effect on volume

    I just finished my second 5f10 Harvard build, but I made some changes. I replaced the tone stack from the 5f10 with the Blackface tone stack. The new amp is considerably quieter than the first one that I built. The first one I built starts to breakup at about 8, the new one is clean all the way to 10. Could the difference be in the tone stack? Tonight I was planning on wiring in the original tone stack and seeing what it does before I look for a problem somewhere else, but I was curious to see what people think.

    The way I have it is a lot like a blackface Princeton, minus one amplification stage. Was that put in there because of the gain reduction from the blackface style tone stack?

    https://guitarscanada.com/index.php?...hem-gif.21061/

    https://tubeamplifierparts.com/schem..._schematic.gif

    Thanks,

    Eric

    0 Not allowed! Not allowed!
    Last edited by E biddy; 02-11-2019 at 09:47 PM. Reason: Added links to schematics and changed one to a 5f10

  2. #2
    Supporting Member eschertron's Avatar
    Join Date
    Aug 2012
    Location
    Great Black Swamp
    Posts
    2,215
    Thumbs Up/Down
    Received: 395/0
    Given: 1,033/1
    Rep Power
    11
    Does the 5f10 have a tone stack similar to the 5e3 single tone knob? That design is considerably less lossy that a FMV 2 or 3 knob design.

    1 Not allowed! Not allowed!
    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


  3. #3
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by eschertron View Post
    Does the 5f10 have a tone stack similar to the 5e3 single tone knob? That design is considerably less lossy that a FMV 2 or 3 knob design.
    Yes, I think it is the same one.

    0 Not allowed! Not allowed!

  4. #4
    Supporting Member eschertron's Avatar
    Join Date
    Aug 2012
    Location
    Great Black Swamp
    Posts
    2,215
    Thumbs Up/Down
    Received: 395/0
    Given: 1,033/1
    Rep Power
    11
    Are you familiar with Duncan's TSC (tone stack calculator)? I use it often to compare the loss between different stack designs. A BF stack may lose 20-30dB, while a single-knob maybe only 6dB. Quite a difference to make up!

    If you turn the mid knob to max, how close to breaking up can you get?

    1 Not allowed! Not allowed!
    Last edited by eschertron; 02-11-2019 at 09:02 PM. Reason: typo
    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


  5. #5
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,717
    Thumbs Up/Down
    Received: 1,848/22
    Given: 1,446/35
    Rep Power
    26
    If set close to "flat" (which requires a wonky knob setup, it is not simply 5 5 5) loss is almost 20 dB.
    When set by ear to more usual values, some moderate boost , itīs still some 10 dB down.

    So you lost that much gain and the reason youīd actually need an extra triode.

    Many old designs used little or no NFB; so if you use it now you need even higher raw gain factored in, to make up for losses.

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  6. #6
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by eschertron View Post
    Are you familiar with Duncan's TSC (tone stack calculator)? I use it often to compare the loss between different stack designs. A BF stack may lose 20-30dB, while a single-know maybe only 6dB. Quite a difference to make up!

    If you turn the mid knob to max, how close to breaking up can you get?
    The AB763 doesn't have a mid pot, it is a fixed 6.8K resistor.

    Unfortunately Duncan's TSC doesn't have a model for the single knob tone control to compare.

    0 Not allowed! Not allowed!

  7. #7
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by J M Fahey View Post
    If set close to "flat" (which requires a wonky knob setup, it is not simply 5 5 5) loss is almost 20 dB.
    When set by ear to more usual values, some moderate boost , itīs still some 10 dB down.

    So you lost that much gain and the reason youīd actually need an extra triode.

    Many old designs used little or no NFB; so if you use it now you need even higher raw gain factored in, to make up for losses.
    I built this with switchable NFB and switchable cathode/fixed bias. When I take off the NFB it does get a bit louder and I get some breakup at 10.

    The other thing I was wondering about is the second triode stage isn't bypassed. How much gain could I pick up by bypassing it like the 3rd stage of the AB763 Princeton?

    0 Not allowed! Not allowed!

  8. #8
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by E biddy View Post
    The other thing I was wondering about is the second triode stage isn't bypassed. How much gain could I pick up by bypassing it like the 3rd stage of the AB763 Princeton?
    OK, I just figured it out and it should be about 6dB, so that should get me about part way there.

    1 Not allowed! Not allowed!

  9. #9
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,717
    Thumbs Up/Down
    Received: 1,848/22
    Given: 1,446/35
    Rep Power
    26
    If you want to play "clean" you are already there, since you get light crunch on 10.

    If you want to play somewhat dirty or adding sustain (daīBloozī setting) you can add clean gain between input jack and first triode, adding a single FET stage or even an .... Op Amp !!!!

    No, you will NOT turn it into a "soulless clinical buzzy abomination" by any means, that first stage will add little gain (say 3X to 10X), will not distort or colour sound at all , just make the first triode think you have real hot pickups in your guitar.

    Far simpler easier cheaper than adding an extra triode which by the way can be too much.
    Even $50k-a-head Dumble does that!!!!

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  10. #10
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by J M Fahey View Post
    Far simpler easier cheaper than adding an extra triode which by the way can be too much.
    Even $50k-a-head Dumble does that!!!!

    0 Not allowed! Not allowed!

  11. #11
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by J M Fahey View Post
    If you want to play "clean" you are already there, since you get light crunch on 10.

    If you want to play somewhat dirty or adding sustain (daīBloozī setting) you can add clean gain between input jack and first triode, adding a single FET stage or even an .... Op Amp !!!!

    No, you will NOT turn it into a "soulless clinical buzzy abomination" by any means, that first stage will add little gain (say 3X to 10X), will not distort or colour sound at all , just make the first triode think you have real hot pickups in your guitar.

    Far simpler easier cheaper than adding an extra triode which by the way can be too much.
    Even $50k-a-head Dumble does that!!!!
    Is it as simple as something like this? Op amp gain stage.pdf

    Edit: I just saw you said in front of the first stage.

    0 Not allowed! Not allowed!

  12. #12
    Senior Member
    Join Date
    Mar 2018
    Location
    Germany
    Posts
    1,903
    Thumbs Up/Down
    Received: 1,430/1
    Given: 834/2
    Rep Power
    4
    Not quite. Tube amps are typically high impedance, meaning that each stage should have high input impedance (often around 1M) to not load down the preceding one (or when used as first stage the guitar PUs). Your example shows an inverting circuit having an input impedance of only 1k. You should use a non-inverting op amp circuit or a Fet.

    1 Not allowed! Not allowed!
    - Own Opinions Only -

  13. #13
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,717
    Thumbs Up/Down
    Received: 1,848/22
    Given: 1,446/35
    Rep Power
    26
    Agree.
    You found a very low impedance Op Amp gain stage.
    Too busy now but later Iīll draw a single Op Amp gain stage , non inverting, High Z input (1M) and fed from existing tube +V (200 something volts) so you donīt need an extra supply.

    1 Not allowed! Not allowed!
    Last edited by J M Fahey; 02-12-2019 at 02:33 AM.
    Juan Manuel Fahey

  14. #14
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    I found a wiring mistake in the tone stack, and it added some gain to the amp. It is still quieter than the 5f10, but sounds good. The negative feedback and bias switch work great.

    Quote Originally Posted by J M Fahey View Post
    Agree.
    You found a very low impedance Op Amp gain stage.
    Too busy now but later Iīll draw a single Op Amp gain stage , non inverting, High Z input (1M) and fed from existing tube +V (200 something volts) so you donīt need an extra supply.
    I'm pretty happy with the sound now, but I would still like to see this. Also, this amp does have a 50V tap. Would that make something like this easier?

    Click image for larger version. 

Name:	swich bias.jpg 
Views:	20 
Size:	25.3 KB 
ID:	52535

    0 Not allowed! Not allowed!

  15. #15
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,717
    Thumbs Up/Down
    Received: 1,848/22
    Given: 1,446/35
    Rep Power
    26
    Yes, but checking the amp schematic I found input stage is built out of a single triode.

    So **in this particular case** you might replace that single triode with a 12AX7 and have a "real" extra triode gain stage with little investment.

    I bet transformer can feed extra 150mA filament, and you might enlarge the current 7 pin socket hole to accomodate a 9 pin one.

    In fact, they might *already* have a noval compatible hole there (since chassis are often built for various models) ; the FET suggestion was to avoid punching a new hole and taxing the transformer, but it looks like "here" itīs not the case.

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  16. #16
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by J M Fahey View Post
    Yes, but checking the amp schematic I found input stage is built out of a single triode.

    So **in this particular case** you might replace that single triode with a 12AX7 and have a "real" extra triode gain stage with little investment.

    I bet transformer can feed extra 150mA filament, and you might enlarge the current 7 pin socket hole to accomodate a 9 pin one.

    In fact, they might *already* have a noval compatible hole there (since chassis are often built for various models) ; the FET suggestion was to avoid punching a new hole and taxing the transformer, but it looks like "here" itīs not the case.
    I made the chassis, so enlarging it wouldn't be any problem and the transformer is oversized for this application, so that wouldn't be any problem. Thanks.

    0 Not allowed! Not allowed!

  17. #17
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Location
    Buenos Aires, Argentina
    Posts
    11,717
    Thumbs Up/Down
    Received: 1,848/22
    Given: 1,446/35
    Rep Power
    26
    Cool.
    Fets (or Op Amps) are used to substitute tubes where space or filament power is a premium but here , not that a big deal.

    1 Not allowed! Not allowed!
    Juan Manuel Fahey

  18. #18
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    15,066
    Thumbs Up/Down
    Received: 2,104/4
    Given: 2,398/0
    Rep Power
    30
    Adding a front end boost via a FET behind a BF tone stack sounds like a fun idea (at least Dumble thought so ). So absolutely do that if you're interested and like the idea. You'll get no argument from me against experimenting. But...

    You could skip it and just add a tone stack bypass switch for getting dirty. Since the amp will get to the edge of breakup now you do have full clean power/watts. With the addition of the second stage cathode bypass cap you'll have a little more gain for the basic, clean tone. That, and a tone stack bypass option would have a good bit more gain than a stock 5f10 for getting dirty. Of course this means no tone stack when the switch is flipped. But once you're clipping much the tone stack is really only used for mitigating LF to avoid flatulence. This could be built in to the switched circuit. And no extra "shtuff" in the amp.

    2 Not allowed! Not allowed!
    "Never bet your life on somebody else doing their job." SoulFetish's good friend

    "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

    "Back to the amp. It makes horrible sounds when I play my guitar thru it... because I suck at playing guitar." Mike6158

  19. #19
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Quote Originally Posted by Chuck H View Post
    Adding a front end boost via a FET behind a BF tone stack sounds like a fun idea (at least Dumble thought so ). So absolutely do that if you're interested and like the idea. You'll get no argument from me against experimenting. But...
    What would this look like? Something like this?

    Click image for larger version. 

Name:	Fet stage.PNG 
Views:	22 
Size:	37.2 KB 
ID:	52558

    Or would that be a buffer? I don't really know these circuits.

    0 Not allowed! Not allowed!

  20. #20
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    15,066
    Thumbs Up/Down
    Received: 2,104/4
    Given: 2,398/0
    Rep Power
    30
    I've seen it demonstrated a couple of ways. But the circuit is typically indicated as an "input" switched system. So I'm going to guess it's an input boost/buffer. That is, the first stage the guitar sees and before the first tube stage of the amp. Sorry, I'm not a Dumble enthusiast or expert. I just know they included a FET circuit near the input of their BF-ish styled amps. And Dumble never did anything that didn't sound good. Circuit references on line are EXTREAMLY ambiguous.

    2 Not allowed! Not allowed!
    "Never bet your life on somebody else doing their job." SoulFetish's good friend

    "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

    "Back to the amp. It makes horrible sounds when I play my guitar thru it... because I suck at playing guitar." Mike6158

  21. #21
    Senior Member
    Join Date
    Mar 2018
    Location
    Germany
    Posts
    1,903
    Thumbs Up/Down
    Received: 1,430/1
    Given: 834/2
    Rep Power
    4
    That's what I collected from the internet:

    dods100.pdf

    dprefet.pdf

    3 Not allowed! Not allowed!
    - Own Opinions Only -

  22. #22
    Member E biddy's Avatar
    Join Date
    May 2015
    Location
    Lansing, Michigan
    Posts
    81
    Thumbs Up/Down
    Received: 6/0
    Given: 30/0
    Rep Power
    5
    Would something like this work?

    Fet stage in harvard.pdf

    0 Not allowed! Not allowed!

  23. #23
    Supporting Member eschertron's Avatar
    Join Date
    Aug 2012
    Location
    Great Black Swamp
    Posts
    2,215
    Thumbs Up/Down
    Received: 395/0
    Given: 1,033/1
    Rep Power
    11
    Notice the two designs Helmholtz offered both have the fet right at the input. Anywhere later in the signal path and you run out of the fet's input headroom.

    0 Not allowed! Not allowed!
    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Replies: 7
    Last Post: 08-08-2018, 01:24 PM
  2. Tone control to tone stack...
    By SteveJones in forum Build Your Amp
    Replies: 4
    Last Post: 02-04-2013, 02:28 AM
  3. About the VOX tone stack
    By JohnnyMcFly in forum Theory & Design
    Replies: 16
    Last Post: 06-16-2010, 05:43 AM
  4. Tone knob has no effect on tone.
    By srvprodigy in forum Guitar Tech
    Replies: 3
    Last Post: 09-07-2008, 05:34 PM
  5. 5E3 Tone Stack / Volume Control Theory
    By jakejoseph in forum Theory & Design
    Replies: 16
    Last Post: 08-06-2008, 02:57 PM

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
  •