Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bwmitc9285 on August 23, 2017, 01:53:57 pm
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This is my first post on the forum (though I've been visiting this site for years) so I apologize if this has been asked/answered elsewhere. I am looking to build a Stout TMB but would rather it have 6v6's instead of the standard EL84. If anyone has a schematic with 6v6 values or specific component changes I would greatly appreciate it.
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In general, from EL84 to 6V6 only needs a bigger cathode resistor under the 6V6es. Steal a value from any 6V6 plan of similar voltage.
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another option is to take 6v6 plexi phase inverter, output stage, & power supply plan and graft stout TMB pre-amp to that. 6V6 plexi is fixed bias, still will work fine.
stout TMB schema:
http://el34world.com/Hoffman/files/Hoffman_Stout.pdf (http://el34world.com/Hoffman/files/Hoffman_Stout.pdf)
6v6 plexi:
http://el34world.com/Hoffman/files/Hoffman_Plexi_6V6-V2.pdf (http://el34world.com/Hoffman/files/Hoffman_Plexi_6V6-V2.pdf)
--pete
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This is my first post on the forum (though I've been visiting this site for years) so I apologize if this has been asked/answered elsewhere. I am looking to build a Stout TMB but would rather it have 6v6's instead of the standard EL84. If anyone has a schematic with 6v6 values or specific component changes I would greatly appreciate it.
I am just finishing up that exact modification and it is really nice.
I struggled with it for a while, but it is getting closer to where I want it.
I am actually going to work on it tonight and try a different rectifier as one experiment.
I built the amp as a back up but it is becoming a player.
I can assist with any component values if you need. BTW, my bass response is huge, I am going to try and tighten it up a bit as well.
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Thanks for the suggestions everyone. After comparing a few different schematics I think I am going to change the cathode resistor to a 250r and the PI tail resistor to a 22k. Other than changing out the sockets I think these are the only two things that need changing?
This is my first post on the forum (though I've been visiting this site for years) so I apologize if this has been asked/answered elsewhere. I am looking to build a Stout TMB but would rather it have 6v6's instead of the standard EL84. If anyone has a schematic with 6v6 values or specific component changes I would greatly appreciate it.
I am just finishing up that exact modification and it is really nice.
I struggled with it for a while, but it is getting closer to where I want it.
I am actually going to work on it tonight and try a different rectifier as one experiment.
I built the amp as a back up but it is becoming a player.
I can assist with any component values if you need. BTW, my bass response is huge, I am going to try and tighten it up a bit as well.
Purpletele are there any other changes you made?
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I changed everything I could.
However, I am not as clever as Doug and the boys.
I recently changed everything bac to stock.
I think I have a 12AT7 in v2 for more headroom.9
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tweedy stout...
see attached.
--pete
edit: updated schematic notes, etc.
edit: corrected C9 / R11 node.
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Is R11 for the negative feedback drawn correctly?
With respect, Tubenit
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R11 is correct but C9 is wrong. C9 should connect to the junction of R11 and R12, not ground.
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R11 is correct but C9 is wrong. C9 should connect to the junction of R11 and R12, not ground.
That's what I was hinting at. :icon_biggrin: :thumbsup:
With respect, Tubenit
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> C9 is wrong.
Either/or.
C9 is drawn "right" for basic operation.
C9 the other way is Fender-style.
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Thanks for the schematic Pete. That definitely helped clarify some values. It looks like these are the components that need updating on the standard EL84 TMB board.
| EL84 Stout | 6V6 Stout |
| R18: 47K | 33K |
| R13: 100K | 91k |
| R21: 470K | 100K |
| R22: 470K | 100K |
| R25: 130R | 270R |
| C10: 47UF | 33UF |
| R23: 8.2K | 1k5 |
| R24: 8.2K | 1k5 |
| R26: 1K | 470R |
| R27: 1K | 470R |
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This is the critical change.
EL84 Stout 6V6 Stout
R25: 130R 270R
All the others are minor differences. EL84 and 6V6 are more alike than different, and same values in the preamp and driver will work for either. Differences above are more a matter of taste or fine-tweak than essential.
The killer difference is the 6V6 cathode resistor *must* be almost double what works for EL84. If you use '84 value under 6V6, they will melt.
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corrected schema and attached revisions to reply #6.
apologies for any confusion.
as stated - cathode resistor is the major change. i tuned the LTPI for a bit more drive and balance, otherwise use doug's plan.
--pete
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No confusion at all. I appreciate the suggestions. I just placed an order for parts using the updated values and I'll post some pictures once I get everything up and running. Thanks for the help everyone!
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I have Sherman the former EL 84 Hoffman Stout up and running as a really smooth 6 v 6 amp. I am planning on a nice video soon.
It's smoother/cleaner than my 18 watt Plexi. I had a 5Y3 GT Rectifier in it and I switched to a 5AR4. It has quite a bit of sag, much different that the SS rectifier on my Plexi and Dr. Z Remedy.
I installed an EQ by pass which is quite useful for natural light OD.
This amp platform could benefit from an FX Loop. I haven't searched but maybe there is a schematic for the loop on something similar.
I have that on my list to develop a plan but I have two other projects in front of that. It might be something that interests a lot of folks.
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I have updated the Hoffman provided Stout TMB schematic to match the suggestions listed above in case anyone else is looking to build one of these.
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I found that my amp had a really strong bass response with a .022 cap and the 6 v 6 tubes. I changed it to .047 the other night and that seemed to help it but I haven't fully tested it.
Also, the amp felt like it had a lot of sag so I changed the 5y3 to a 5ar4 and that had a positive affect.
My amp has gone through a metamorphous state and has come out as a really sweet sounding and powerful clean amp platform and it responds well with pedals.
I keep threatening to make a video, it will be soon.
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I found that my amp had a really strong bass response with a .022 cap and the 6 v 6 tubes. I changed it to .047 the other night and that seemed to help it but I haven't fully tested it.
Also, the amp felt like it had a lot of sag so I changed the 5y3 to a 5ar4 and that had a positive affect.
SSR & larger plate and screen filter will tighten it up significantly... some like a little sag though so 5AR4 is a good compromise.
--pete
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I found that my amp had a really strong bass response with a .022 cap and the 6 v 6 tubes. I changed it to .047 the other night and that seemed to help it but I haven't fully tested it.
Also, the amp felt like it had a lot of sag so I changed the 5y3 to a 5ar4 and that had a positive affect.
SSR & larger plate and screen filter will tighten it up significantly... some like a little sag though so 5AR4 is a good compromise.
--pete
Pete, thank you,
I think it is really nice right now, but I would like to try a larger filter. Can you point me to the correct Plate and Screen filter? I am reviewing the schematic now.
I have two Plexi amps with SSR which I really like but this amp is a great rhythm guitar amp.
Thanks,
BV
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I found that my amp had a really strong bass response with a .022 cap and the 6 v 6 tubes. I changed it to .047 the other night and that seemed to help it but I haven't fully tested it.
Also, the amp felt like it had a lot of sag so I changed the 5y3 to a 5ar4 and that had a positive affect.
SSR & larger plate and screen filter will tighten it up significantly... some like a little sag though so 5AR4 is a good compromise.
--pete
Pete,
I reviewed your schematic and your notes make sense, thank you. I really like the creative use of the two Cap Cans.
I think I am going to leave Sherman as is for a while. I like the SAG for now and it sure has a nice slightly Marshally tone.
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Just got the amp finished up. The only other change I made is I used a deluxe reverb output transformer since the amp now has 6v6s. I don't have tubes yet but I'm going to test it out tonight without them and see what the voltages are. The cab was my first attempt at woodworking/ tolexing and it's not perfect but it will do. Thanks again for everyone's help so far!
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Very nice work!
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I got the tubes in last night and it fired right up and sounded great. The voltages look a little low to me though. These values are without a current limiter. I used the values listed in the most recent schematic above. Do these look abnormal to anyone?
A: 315
B: 308
C: 274
D: 265
V3 (JJ6v6S)
Plate: 305
V4 (JJ6v6S
Plate: 305
Voltage drop across cathode resistor: 18v
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my math shows about 9.4w a tube, your values do seem low compared to the schematic
but;
it fired right up and sounded great.