Question about 6V6 Bassman build.

[Mike Simpson]

Here is the description from a Reverb ad, shows 5Y3 rectifier, bias pot and multi tap OT.

https://reverb.com/item/116473-rich...an-inspired-classic-narrow-panel-1-x-12-combo

Richter RS-22 Signature Series

22 watt 5F6-A Tweed Bassman Inspired Classic Narrow Panel Combo

This is a modernized lower powered version of the 5F6-A Tweed Narrow Panel designed with reduced output in mind. Built around 6V6 output tubes this unit produces the classic signature vintage tweed tone at a much more manageable power level. Reduced cabinet size and single 12" speaker offer better grab & go convenience and weight for today's professional musician. This is not a tossed together kit or modded original.

100% Custom Hand Wired
In Stock & 100% Plug & Play Ready

• The amp is rated at 22Watts using 6V6 outputs tubes only, (can not use 6L6 family tubes)
• Features include the standard Bassman 5F6-A control complement.
• 4 inputs (high-low normal & high-low bright)
• 2 volumes (normal channel & bright channel)
• 1 Treble
• 1 Midrange
• 1 Bass
• 1 Presence
• Power Switch
• Standby Switch
• Pilot Lamp
• Jensen Jet Series Electric Lightning
  
• (1)- JJ 12AX7 / ECC83
• (2)-TAD 7025-WA High-grade, Premium Selected
• (1)- Matched Pair TAD 6V6GT-STR
• (1) JJ 5Y3S Rectifier
• Re-sized 1 X 12 Tweed Cab, about 39 lbs total weight
• Impedance selector (4,8,&16ohm) with parallel output jacks
• On-board bias adjustment pot & external bias pot and test jack access

 

[Mike Simpson]

Note: the RS22 used a 5Y3 rectifier.

Info on running 6V6 in a 5F6A from Rob's page.

https://robrobinette.com/5F6A_Modifications.htm#Run_6V6

Run 6V6 Power Tubes
Pairing the Bassman's preamp and long tail pair phase inverter with 6V6 power tubes will give you small bottle tone but lots more power tube overdrive because the LTP's output can fully overdrive the little 6V6 power tubes.

But to get the most out of a 6L6 it needs higher B+ voltage than a 6V6 and more current output from the power transformer. But if you build the amp with a bigger 6L6 power tranny then the 6V6 loses a lot of voltage sag so it sounds stiffer and punchier with a noticeably tighter low end (sounds more solid state and less tubey). This effect can be overcome in the 5F6A by using a 5Y3 rectifier tube which will still cause voltage sag with 6V6 tubes.

Same problem with the output transformer. The 6L6 needs a higher current rating tranny than a 6V6 so it won't just saturate at 6V6 levels (more 6L6 output current = more saturation and compression with no more volume). But then a 6V6 using a bigger tranny loses it's compression and sounds more dynamic and solid state.

If the amp has a multi-tap output transformer (and all amps designed to run 6V6 and 6L6 should have them) most of the output tranny impedance mismatch can be handled by using a one step higher speaker impedance setting -- if the amp is designed for 6L6 then set the impedance selector to 8 ohms with a 16 ohm speaker or set to 4 ohms with an 8 ohm speaker.

You also need to lower the amp's B+ voltage so you don't burn up the 6V6 tubes. You can do this by simply installing a 5Y3 rectifier tube.

 

[Wyatt]

Note: the RS22 used a 5Y3 rectifier.

That would drop the B+ to ~360 with a stock 5F6a PT, which would eliminate it from list of changes.

 

[ES330]

BF Bassman has always been my favorite Bassman era !!!
Using 6v6 instead could noticeably lower the weight due to smaller transformer.

 

[bigguy12321]

Between the 5F6-a and variants, the 6G3, the AB763 non-reverb amps, to say nothing of designs that are topologically similar but with different brands/pedigrees and power tubes (Vox, Dr. Z, Matchless), you seem to have seen that you can do whatever you want. An input stage, a cathode follower, a tone stack, a long-tailed pair phase inverter, a pair of 6V6GTAs. It will all fit together fine.

The rest of your work is going to be more concerned with figuring out what you actually want, and how to describe it. Some folks will hear '5F6-a' and think anything vaguely plexi-like will fit. Some folks will say if the B+3 and B+4 voltage supplies aren't within ±20% of the Bassman schematic, your amp isn't really anything like a Bassman. Or if it doesn't run 5881 tubes in the first place. I say this without judgment; it's a communication thing, and concerned with a difficult subject matter.

Lots of different factors contribute to what an amp sounds like, and they can't all be dissected and rearranged in perfectly clear predictable ways.

My favorite little snippet of online culture I picked up from EL34 world is this: someone inevitably posts something like 'hey, I want to build an XYZ with ABC and 123, what will it sound like?'

And the comeback I saw one of the mods use was: 'Build it and tell us.'

I built this this summer. It's rad. My most Bassman-like amp so far. (It's not a flexible as you say you want, but I share it to give an example of how the known circuit blocks can be arranged and tweaked to good effect by an amateur). Good luck!
View attachment 543642

@Snfoilhat That looks great, I will save that one! The quote is spot on, and I agree completely, it will have to be built to know for sure. I've heard that the Tweed Bassman is great because of what it is and anything else isn't a T.B. (much like the 5E3) The note about the B+ 3&4 are noted.

You may have a wrong interpretation of the meaning of power.

Not needing "50 watts" doesn't really mean anything. Power is a poor indicator of loudness (as Sound Pressure Level), if that's your concern. It's not difficult to build a 50 watt amp and 20 watt amp that's louder. To cut the loudness in half takes a 4x to 10x reduction in output power, all else being equal.

Switching power tubes to 6V6's - even if everything else is equal - will only result in a slight reduction of loudness and headroom (I prefer that term to "volume" as volume can be confused with the control on the amp and ho it operates). Speaker sensitivity and total cone square inches, cabinet type and construction and overall amp design mean far more in regards to loudness that output power.

There are some pieces of information missing in order to make qualified recommendations -

What style of music do you play; do you only play at home, jam with friends or play gigs (and if the latter in what types of places - small clubs, halls, churches, places with or without stages, ceiling heights and type, are the amps mic'd) and in any band/jam situation how many other players and - if possible - what are they using? Do you play clean, and f you use distortion do you prefer a smooth transition into output stage saturation or an instantaneous pedal-type change?

Seriously, all this stuff makes a difference - in my case I've played a variety of styles and places, so I have several gig amps. I use whichever one can be run close to the limit of its headroom with guitar controls rolled back a bit. Then I have some guitar control over the level for solos and a bit more to push the amp into mild saturation. Most gigging players I know use a similar "array" or gear. That way they have the best chance of optimizing their tone in just about any situation.

Hope that helps - if nothing else it'll give you some things to think about and possible future goals.

@Silverface My uses are at home, mostly, recording sporadically, gigging emen more sporadically. Of all the amps I've built what I find I like least of them is my playing... No matter what I plug into, I sound like me playing guitar. My favorite so far was the Tweed Princeton SS rectifier in a Deluxe sized cab with a 10" speaker. Simple and effective.

I have been planning to build the same basic amp.
The Richter RS22 (no longer made) was a bassman with 6v6 output (and some other changes no doubt). As far as I can tell Sara stopped building amps and the website is gone.

Here are some internet pics of the Richter RS22

View attachment 543658 View attachment 543659 View attachment 543660

@Mike Simpson Thank you for this. I had forgotten about Sara's RS22. Any more detail you can share would be appreciated! Thanks for the pics!

I see no reason for any deviation from the 5F6a schematic as far as the caps, resistors, and layout are concerned. Preamp, tone stack, PI could remain unchanged.

All the changes would be in the power supply and output...

• PT swap for lower power tube plate voltage
  
• Dropping resistor changed to offset the lower B+ voltage to maintain the correct PI and preamp plate voltages
• 25-watt OT with a 6.6K-8K primary and the desired secondary
• Change the NFB loop values to compensate for new OT secondary

That's all it would take. DR iron may be ideal.

@Wyatt So if I'm pickin up what yer layin down, If I change B+1 and 2 and keep 3&4 up I may stand a chance. (along with proper OT and NFB.

This is why I come here.

Thanks all.

a

 

[stinga11]

Greetings to all. I am interested in recreating the layout of the Richter RS-22 amplifier but I can not identify the colors of dropping resistor. someone I observed in the photos and can see what values they are. because with the 6v6 are not the same values. I thought use a two 10K but I prefer use the Richter values.

 

[Teleguy61]

You may have a wrong interpretation of the meaning of power.

Not needing "50 watts" doesn't really mean anything. Power is a poor indicator of loudness (as Sound Pressure Level), if that's your concern. It's not difficult to build a 50 watt amp and 20 watt amp that's louder. To cut the loudness in half takes a 4x to 10x reduction in output power, all else being equal.

Switching power tubes to 6V6's - even if everything else is equal - will only result in a slight reduction of loudness and headroom (I prefer that term to "volume" as volume can be confused with the control on the amp and ho it operates). Speaker sensitivity and total cone square inches, cabinet type and construction and overall amp design mean far more in regards to loudness that output power.

There are some pieces of information missing in order to make qualified recommendations -

What style of music do you play; do you only play at home, jam with friends or play gigs (and if the latter in what types of places - small clubs, halls, churches, places with or without stages, ceiling heights and type, are the amps mic'd) and in any band/jam situation how many other players and - if possible - what are they using? Do you play clean, and f you use distortion do you prefer a smooth transition into output stage saturation or an instantaneous pedal-type change?

Seriously, all this stuff makes a difference - in my case I've played a variety of styles and places, so I have several gig amps. I use whichever one can be run close to the limit of its headroom with guitar controls rolled back a bit. Then I have some guitar control over the level for solos and a bit more to push the amp into mild saturation. Most gigging players I know use a similar "array" or gear. That way they have the best chance of optimizing their tone in just about any situation.

Hope that helps - if nothing else it'll give you some things to think about and possible future goals.

This.

Building an amp designed for 6L6 variants, but built with 6V6s, will not provide an equivalency.
6V6 amps sound very different from 6L6 amps.