Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 18 2023 05:23 PM
It may sound crazy or stupid but for money reasons I do it, I really wanted that beautiful sound of the 6G7-A and recently finished finding out how tube amps work and something that came to mind was, "Well I don't have the money to do the whole thing so, goodbye vibrato" , I will upload the 'schematic' of what it would be like, any help will be welcome. It may be a little bad edit I know.
The principal things I would need would be tranaformers, and parts in general.
Last edited: Dec 20, 2023 20:50:23
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Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 18 2023 05:24 PM
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ldk
Joined: Nov 08, 2017
Posts: 367
San Francisco Bay Area
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Posted on Dec 18 2023 06:37 PM
I've found https://robrobinette.com/Amp_Stuff.htm to be very helpful.
Some might say to start with a simple amp, like a single-ended Champ. That's how I started and have since made more complicated amps. I'm not sure it was a necessary route. If you're careful and do good soldering, you should have no trouble with your 6G7 project.
— If I'd stop buying old guitars to fix, I might actually learn to play.
Bringing instruments back to life since 2013.
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Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 18 2023 07:39 PM
ldk wrote:
I've found https://robrobinette.com/Amp_Stuff.htm to be very helpful.
Some might say to start with a simple amp, like a single-ended Champ. That's how I started and have since made more complicated amps. I'm not sure it was a necessary route. If you're careful and do good soldering, you should have no trouble with your 6G7 project.
I could consider, I have been working with sound equipment for a long time and understanding how they work, this is a somewhat more ambitious project, I like to have things well calculated, have a good base, work in a Champ, sure, why not, thank you.
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terma_reverb
Joined: Apr 17, 2012
Posts: 47
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Posted on Dec 19 2023 07:53 AM
Hello @Surf_fan63, some months ago I finished a similar project for an 6G14A Showman without the vibrato channel here.
I suggest to check Rob Robinette's Blackvibe, it is a similar build but for a Vibroverb.
I also based the design for my amp on the Blackvibe, you can use the layouts as a starting point and I think they are already pretty close to the 6G7-A. Without the vibrato you can easily fit it into a Princeton chassis which is also the one suggested for Vibroverb.
I also suggest to add a middle control, master volume, and NFB pot. These mods turned to be extremely useful for my build. You can find details at the mod section of Rob Robinette's site.
There is an OT for 6G7-A selled by Tube Amp Doctor here.
As far as I know, the output transformer for the bandmaster was not totally aligned with the amp design (primary impedance of 6K instead of 4K), and that contributed to the characteristic sound of the bandmaster. One common upgrade is to swap the output transformer to a bassman's for a fuller, bigger sound.
There is also a 6G7-A suitable PT here, but as a cheaper alternative you could order a PT with the same specs from a local store (it was about 1/4 of the price for mine).
Have fun and good luck on this new project! Keep us up-to-date!
Last edited: Dec 19, 2023 07:54:35
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edwardsand
Joined: Jun 29, 2018
Posts: 755
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Posted on Dec 19 2023 10:04 AM
Yes, Rob Robinette's site is chock full of great info.
Also I suggest running your plans by the people on the EL34World tube amp forum (Doug Hoffman's site) - they give tons of great feedback and help. Any questions you have about the schematic and how to build the amp without tremolo will be quickly answered there.
Building a Champ to start can be good, but with your plan, you've already got things down to 4 tubes (since there's solid state rectification rather than tube), it may not be too big of a challenge as a first amp build. A lot of people build the 5E3 Deluxe, and that is around the same level of complexity.
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Tqi
Joined: Dec 07, 2014
Posts: 1222
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Posted on Dec 19 2023 04:38 PM
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Last edited: Jan 31, 2024 15:31:58
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edwardsand
Joined: Jun 29, 2018
Posts: 755
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Posted on Dec 19 2023 09:47 PM
Before going too far down this road, you should let us know what it is specifically about the Bandmaster 6G7-A you really like. And also, what are you looking for in an amp? These are important questions, because we could maybe point you to an amp design that really fits what you are looking for. Is it the loudness of the two 6L6 tubes? The tone stack? Or just the general sound of the brown panel era Fender amps? Is this for playing at home or for playing live?
All those things matter and can help you build an amp that you would really be happy with. And then we could help you with finding sources for parts, etc.
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Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 20 2023 02:27 PM
edwardsand wrote:
Before going too far down this road, you should let us know what it is specifically about the Bandmaster 6G7-A you really like. And also, what are you looking for in an amp? These are important questions, because we could maybe point you to an amp design that really fits what you are looking for. Is it the loudness of the two 6L6 tubes? The tone stack? Or just the general sound of the brown panel era Fender amps? Is this for playing at home or for playing live?
All those things matter and can help you build an amp that you would really be happy with. And then we could help you with finding sources for parts, etc.
Well, about that specific circuit and amplifier I like the sound in general, everything about the amplifier itself is planned to be used both at home and live, what I look for in an amp and in this amp is its power and versatility, I decided on this model since my father calls me crazy for wanting to build a 100w power amplifier like the showman (besides of wanting to use such power at home), but other than that I do like the 6G7A and of course I love the sound of brownface amps.
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Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 20 2023 02:34 PM
terma_reverb wrote:
Hello @Surf_fan63, some months ago I finished a similar project for an 6G14A Showman without the vibrato channel here.
I suggest to check Rob Robinette's Blackvibe, it is a similar build but for a Vibroverb.
I also based the design for my amp on the Blackvibe, you can use the layouts as a starting point and I think they are already pretty close to the 6G7-A. Without the vibrato you can easily fit it into a Princeton chassis which is also the one suggested for Vibroverb.
I also suggest to add a middle control, master volume, and NFB pot. These mods turned to be extremely useful for my build. You can find details at the mod section of Rob Robinette's site.
There is an OT for 6G7-A selled by Tube Amp Doctor here.
As far as I know, the output transformer for the bandmaster was not totally aligned with the amp design (primary impedance of 6K instead of 4K), and that contributed to the characteristic sound of the bandmaster. One common upgrade is to swap the output transformer to a bassman's for a fuller, bigger sound.
There is also a 6G7-A suitable PT here, but as a cheaper alternative you could order a PT with the same specs from a local store (it was about 1/4 of the price for mine).
Have fun and good luck on this new project! Keep us up-to-date!
Thanks @terma_verb I really appreciate the contribution 
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Surf_fan63
Joined: Jan 09, 2021
Posts: 34
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Posted on Dec 20 2023 07:51 PM
Tqi wrote:
You're gonna run into the same problems you did when you looked at doing a 6G14 - component availability in Chile. One advantage is - Hammond do all the transformers you need, and Hammond stuff is one of the cheaper brands. You need:
PT: 290EEX
OT: 1760J
Choke: 194B
These are the most expensive and most model-specific components, other than the chassis and cabinet - which are just basic metal and wood working and can be done by local craftspeople. Once you've bought these, everything else should be relatively easy.
Well, with one exception. You need a 350K tapped pot, which are hard to find and you will have to import. Same issue with making the Showman actually.
Here's three sources:
https://www.mojotone.com/350KA-70K-Tap-Brownface-Treble-Pot
https://www.tedweber.com/wp354at/
https://www.banzaimusic.com/350k-log-tapped.html
Buy the pots. Then buy the transformers. Once you have all that, you're committed and have to make it. 
Thanks for telling me the PT model that works here, it would have been a headache to search on my own
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