I'm in the process of building a little parallel SE guitar amp and came across the Victoria Regal 2 amp (SE parallel cathode bias) , which says it uses an "adaptive transformer" to allow the user to use any of the octal output tubes . 6V6 up to EL34 in any combination without switching or re-biasing. It says it uses a Bi-filar transformer , which means each output tube has it's own winding , and I understand that bit , but how do they manage with the different impedances required by different tubes and the different cathode bias resistors? By all accounts the amp has a very good reputation sonically , but I can't find a schematic or any description of the circuitry involved , or the transformer.
Any amplifier that automatically works with parallel single ended 6V6, 6L6, 5881, KT66, and KT88; and also with KT77 and EL34 (Pin 1 and Pin 8 must be connected together for these 2 tube types) . . .
Is either going to be far from optimum performance for all these tubes; or is going to make some of the tubes die prematurely from too much voltage, too much current, too much screen dissipation, and plate dissipation; or is going to be extremely low power, especially relative to the more powerful tubes.
Warning: the amplifier in question will not possibly work with 7591 tubes (different pin-out connections, they will short out the amplifier circuitry, perhaps destroying the amplifier, and/or the tubes too).
Just because beam power tubes and pentode power tubes are Octal, does not make them all the same pin-out.
Welcome to the Tubes / Valves threads (mostly Hi FI and Stereo vacuum tube amplifiers).
Perhaps the Instruments & Amps threads might have someone who knows the Victoria Regal 2 guitar amplifier; and perhaps has a schematic.
Just saying!
Is either going to be far from optimum performance for all these tubes; or is going to make some of the tubes die prematurely from too much voltage, too much current, too much screen dissipation, and plate dissipation; or is going to be extremely low power, especially relative to the more powerful tubes.
Warning: the amplifier in question will not possibly work with 7591 tubes (different pin-out connections, they will short out the amplifier circuitry, perhaps destroying the amplifier, and/or the tubes too).
Just because beam power tubes and pentode power tubes are Octal, does not make them all the same pin-out.
Welcome to the Tubes / Valves threads (mostly Hi FI and Stereo vacuum tube amplifiers).
Perhaps the Instruments & Amps threads might have someone who knows the Victoria Regal 2 guitar amplifier; and perhaps has a schematic.
Just saying!
That's about treble. Not loading.
All the usual tubes will run SE at 250V 50mA 5K load, or P-P with similar conditions, all making about the same power. Even the ones with G2 where K usually is will work with 470k pull-up on that pin (the ones that are internally jumpered will pull-down harmlessly.
Victoria seems to go a little further, perhaps transformer taps. Or perhaps well-compensated review writers susceptible to suggestion.
PRR,
I did make a mistake about the KT77, the beam formers are internally connected to the cathode, just like the 6V6, 6L6, 5881, KT66, and KT88.
But in your Post # 3, did you mean G2 or G3?
G2 screen needs to be pulled up, like you said, and it does need some current.
I think that a 470k pull-up to 250V B+ is too high of a resistance from G2 to any of the following connections of 3 modes:
B+ for pentode/beam power mode, plate for triode mode, and UL tap for Ultra Linear mode.
G2:
If the G2 resistor is high, for pentode or beam power mode, it also needs a bypass cap to either the cathode or to ground;
a G2 bypass cap can not be used for triode mode and UL mode.
G3:
G3 suppressor grid or beam formers, are normally internally connected to the cathode (6V6, 6L6, 5881, KT66, KT77, and KT88).
But for the EL34 and 6CA7 they are not internally connected to the cathode.
The EL34 and 6CA7 need a connection from pin 1, suppressor grid or beam formers; to pin 8, cathode.
I did make a mistake about the KT77, the beam formers are internally connected to the cathode, just like the 6V6, 6L6, 5881, KT66, and KT88.
But in your Post # 3, did you mean G2 or G3?
G2 screen needs to be pulled up, like you said, and it does need some current.
I think that a 470k pull-up to 250V B+ is too high of a resistance from G2 to any of the following connections of 3 modes:
B+ for pentode/beam power mode, plate for triode mode, and UL tap for Ultra Linear mode.
G2:
If the G2 resistor is high, for pentode or beam power mode, it also needs a bypass cap to either the cathode or to ground;
a G2 bypass cap can not be used for triode mode and UL mode.
G3:
G3 suppressor grid or beam formers, are normally internally connected to the cathode (6V6, 6L6, 5881, KT66, KT77, and KT88).
But for the EL34 and 6CA7 they are not internally connected to the cathode.
The EL34 and 6CA7 need a connection from pin 1, suppressor grid or beam formers; to pin 8, cathode.
Still unable to find any more info on the Regal2. The advertising /review bumph is all the same , talks of the ease of tube-swapping due to an "adaptive transformer" that is "bi-filar" , each output tube having dedicated winding , just stuff to impress buyers. But searching the forums reveals quite a lot of happy users , some of them people with large amp collections and long experience . I know all amps will have users who think they're the bees knees , but I couldn't find many negative remarks , and those were mostly that it had a high noise floor and was a bit dark for some people's taste. And that like all amps with many options , most people just use one setting and sometimes decide to swap the amp for an one that is built for that specific character . Most valve amps at some point come into the hands of people who are interested in the circuit and trace it out , but it seems this one has avoided that.
Hello!
New member here (actually conviced to register by this thread).
I own a Victoria Regal II and I confirm it's a very nice amp. Of course, all that flexibility in the power section has its cost, and several tubes might not be working in their best operational range. Anyway, the overall performance of the amp is really good. It's a perfect tool for the gigging musician who has to adapt to different venues. Just carry a small case of tubes with you to get rid of the typical guitarist's frustration for not having the proper amp to match the room.
So, in terms of design it's something else. Definitely not rocket science, but in any case it's something that's never been offered by any amps manufacturer.
I was also wondering why there's so little interest in the broad audio communities about that unique technical solution. We all know it's just a sort of two parallel single-ended amps sharing same power supply, preamp section and speaker. Several parts of the circuit are not that different from vintage Fender amps, but that OT design has to be investigated.
Amp's topology is quite simple: input preamp stage (12AX7), fenderish reverb circuit, tremolo driven by a single 12AT7 tube (maybe 12AX7? Cannot check now) not using any optoisolator and not affecting power tubes bias (i.e. Fender Princeton), no phase inverter and two cathobe biased power tubes. Tube rectified.
I've tried almost everything from single 6K6GT to a pair of EL34. Some configurations are stellar, many are very good, some just not too bad. Nothing disappointing. It all depends on your needs. A single 6G6 can be perfect for studio recording and completely useless for live performance with a band.
Speakers do affect tone as well, but I don't want to go that far from topic right now.
I started tracing out the circuit for maintenance's sake but it's still in progress because of little spare time for that. I'm willing to complete the job, also including all relevant voltages.
Plate voltage on output tubes is quite low as one may expect. I've measured 290V (plate to cathode) for a single Sovtek 5881, with 73mA plate current. Quite conservative for class-A, I guess. Plate voltage tend to be even lower when using two power tubes. But it was a very quick test I've done in a hurry to troubleshoot the amp quite a long time ago. It has to be done from scratch, with a more scientific approach, for serious documentation purposes.
I have the 112V US version. I've been told that Mark Baier at Victoria designed a sligthly different filter section when using 230V PT for export models. But it's still not confirmed by any amp's owner.
Transformers are made in the US according to the EIA code printed on PT, OT, Rev.T and choke.
As usual, all capacitors but electrolytics are Victoria-branded Orange-Drop looking. Honestly, that's where some marketing hype might be nested.
I will share any further update.
New member here (actually conviced to register by this thread).
I own a Victoria Regal II and I confirm it's a very nice amp. Of course, all that flexibility in the power section has its cost, and several tubes might not be working in their best operational range. Anyway, the overall performance of the amp is really good. It's a perfect tool for the gigging musician who has to adapt to different venues. Just carry a small case of tubes with you to get rid of the typical guitarist's frustration for not having the proper amp to match the room.
So, in terms of design it's something else. Definitely not rocket science, but in any case it's something that's never been offered by any amps manufacturer.
I was also wondering why there's so little interest in the broad audio communities about that unique technical solution. We all know it's just a sort of two parallel single-ended amps sharing same power supply, preamp section and speaker. Several parts of the circuit are not that different from vintage Fender amps, but that OT design has to be investigated.
Amp's topology is quite simple: input preamp stage (12AX7), fenderish reverb circuit, tremolo driven by a single 12AT7 tube (maybe 12AX7? Cannot check now) not using any optoisolator and not affecting power tubes bias (i.e. Fender Princeton), no phase inverter and two cathobe biased power tubes. Tube rectified.
I've tried almost everything from single 6K6GT to a pair of EL34. Some configurations are stellar, many are very good, some just not too bad. Nothing disappointing. It all depends on your needs. A single 6G6 can be perfect for studio recording and completely useless for live performance with a band.
Speakers do affect tone as well, but I don't want to go that far from topic right now.
I started tracing out the circuit for maintenance's sake but it's still in progress because of little spare time for that. I'm willing to complete the job, also including all relevant voltages.
Plate voltage on output tubes is quite low as one may expect. I've measured 290V (plate to cathode) for a single Sovtek 5881, with 73mA plate current. Quite conservative for class-A, I guess. Plate voltage tend to be even lower when using two power tubes. But it was a very quick test I've done in a hurry to troubleshoot the amp quite a long time ago. It has to be done from scratch, with a more scientific approach, for serious documentation purposes.
I have the 112V US version. I've been told that Mark Baier at Victoria designed a sligthly different filter section when using 230V PT for export models. But it's still not confirmed by any amp's owner.
Transformers are made in the US according to the EIA code printed on PT, OT, Rev.T and choke.
As usual, all capacitors but electrolytics are Victoria-branded Orange-Drop looking. Honestly, that's where some marketing hype might be nested.
I will share any further update.
Hi VacuumAid , nice to hear your thoughts ! I had almost given up on finding out more about this amp. Just last night I was talking to someone who has experience of transformers and his thought was that the bi-filar , double primary winding arrangement meant that if two valves with very different outputs were plugged in , the one with the higher output would effectively drive the other output winding alongside it towards the same level ,so the valves would kind of merge their outputs at the primary winding level before they got around to driving the secondary. But that still leaves a bit of a mystery about the biasing. Look forward to seeing a schematic if and when you get around to it.
Hi Allears, each of the two output tubes has its own cathode resistor (rated 10W at least) so as far as I know biasing shouldn't be a problem. They just auto-bias according to collateral conditions, I guess. It's not a fixed-biased amp.
The guy you talked with's assumption seems correct to me. It must be something like that, even though I'm absolutely not an expert of bi-filar transformers.
The guy you talked with's assumption seems correct to me. It must be something like that, even though I'm absolutely not an expert of bi-filar transformers.