I have here a output transformer with ul taps and lots of 6v6 tubes.
I don't like 6v6 in a harmonica amp, too bright. but looking at building a guitar amp to use some of the parts I have on hand.
if anyone has tryed ul on the 6v6's push pull how did they sound.
preamp will probably be 5e5 but using Russian 6h9c
This is all just an idea @ the moment
I don't like 6v6 in a harmonica amp, too bright. but looking at building a guitar amp to use some of the parts I have on hand.
if anyone has tryed ul on the 6v6's push pull how did they sound.
preamp will probably be 5e5 but using Russian 6h9c
This is all just an idea @ the moment
Just because the ultra-linear taps are on the transformer doesn't mean they have to be used; you can wire up the output stage like a normal "pentode" guitar amp, which is what I would recommend.
Wiring a guitar amp as ultra-linear will clean up the output stage's sound. I built a 100 watt marshall clone amp several years ago and wired the output stage as ultra-linear. After a few years, the output transformer blew out; it's the only OT that blew in an amp I built. I don't know if the UL configuration had anything to do with the OT blowing, but I never wired another output stage again as UL.
When an UL output stage is overdriven, the OT tries to correct the distortion produced which means that some really high voltage harmonic spikes get produced in the UL OT of a guitar amp.
Wiring a guitar amp as ultra-linear will clean up the output stage's sound. I built a 100 watt marshall clone amp several years ago and wired the output stage as ultra-linear. After a few years, the output transformer blew out; it's the only OT that blew in an amp I built. I don't know if the UL configuration had anything to do with the OT blowing, but I never wired another output stage again as UL.
When an UL output stage is overdriven, the OT tries to correct the distortion produced which means that some really high voltage harmonic spikes get produced in the UL OT of a guitar amp.
Ultra Linear was widely used in many old PA and guitar amplifiers until the dawn of solid state and now Class D.
Selmar, HiWatt and Orange, to name just three, used UL in their designs with no adverse effects on the transformers.
Messa use switched Pentode to Triode wiring. Triode gives lower power but almost as smooth as UL.
A pair of 6V6 should get about 12W in UL mode with quite low distortion, if there is enough negative feedback. The only draw back with UL is the screen grids run at a similar potential as the anodes, so watch out for your HT supply!
Selmar, HiWatt and Orange, to name just three, used UL in their designs with no adverse effects on the transformers.
Messa use switched Pentode to Triode wiring. Triode gives lower power but almost as smooth as UL.
A pair of 6V6 should get about 12W in UL mode with quite low distortion, if there is enough negative feedback. The only draw back with UL is the screen grids run at a similar potential as the anodes, so watch out for your HT supply!
Yes,
My own design and build amp is a push pull 6V6 Guitar Amp using a 6SL7 Cathodyne (Concertina) splitter.
Ultralinear is switchable.
I used this output tranny.
86PP output transformer
Note tranny is 10K Raa and UL taps are 23% which suits 6V6 better than the usual 43% UL taps.
Local Guitar Gods opinion was divided:
- The guitarist from a Led Zep tribute band liked it in Ultralinear Mode.
- The local shreader god liked it in Pentode Mode which is "looser".
If using UL moder then drop or eliminate any global feedback.
I'm a far better amp tech than a player but I prefer the UL mode (for classic rock and blues and a bit of folk).
Cheers,
Ian
My own design and build amp is a push pull 6V6 Guitar Amp using a 6SL7 Cathodyne (Concertina) splitter.
Ultralinear is switchable.
I used this output tranny.
86PP output transformer
Note tranny is 10K Raa and UL taps are 23% which suits 6V6 better than the usual 43% UL taps.
Local Guitar Gods opinion was divided:
- The guitarist from a Led Zep tribute band liked it in Ultralinear Mode.
- The local shreader god liked it in Pentode Mode which is "looser".
If using UL moder then drop or eliminate any global feedback.
I'm a far better amp tech than a player but I prefer the UL mode (for classic rock and blues and a bit of folk).
Cheers,
Ian
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Lol, thats the exact same transformer Ian, was going to buy some el84's but have so many 6v6's just collecting dust. sounds like I'm going to rebuild YOUR amp lol
I've used that tranny in several Git Amps now and am VERY happy with them.
For the PP 6V6 I built see Post #14 for some scratchy schematics with some discussion above that.
http://www.diyaudio.com/forums/instruments-amps/251971-power-scaling-2.html
Ignore the current source biasing links shown - I ended up with it fixed bias. The CCS biasing worked but had crap overdrive recovery.
Cheers,
Ian
For the PP 6V6 I built see Post #14 for some scratchy schematics with some discussion above that.
http://www.diyaudio.com/forums/instruments-amps/251971-power-scaling-2.html
Ignore the current source biasing links shown - I ended up with it fixed bias. The CCS biasing worked but had crap overdrive recovery.
Cheers,
Ian
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I don't think you should blame 6V6 tubes for that brightness. It was probably the output transformer. Many of the classic tube guitar amps had super-cheap output transformers with severely limited bandwidth. That can sound really nice for electric guitar, and amplified harmonica too.
OPT's made with 'ultralinear' taps are most likely aimed at the hi-fi DIY market, so will be made to be 'good' -- with at least decent high frequency bandwidth. That means they'll probably sound 'glassy', 'brittle', and/or 'harsh' in a guitar amp.
Guitar amps are tone-making machines, not anything like 'accurate reproducers' of sound.
Does anyone know of a source for really 'bad' OPT's with severely limited high frequency response? Those would probably be great for guitar amps, and should be cheap too!
--
The 86PP tranny from Mable Audio listed above is Medium Fi. I've used it in 6V6 and ECL86 (6GW8) Guitar Amps.
For sort of quality guidance, I had a pair in a Baby Huey HiFi Amp. Changing to Hammond 1609 was a definite step up. So 86PP maybe good enough but not too good. I liked them enough to buy 5 more and put them on the shelf for future projects. The Tiny Terror Clone I did with 6GW8 was stunning.
Cheers,
Ian
For sort of quality guidance, I had a pair in a Baby Huey HiFi Amp. Changing to Hammond 1609 was a definite step up. So 86PP maybe good enough but not too good. I liked them enough to buy 5 more and put them on the shelf for future projects. The Tiny Terror Clone I did with 6GW8 was stunning.
Cheers,
Ian
well this may be true, I can say when replaced with 6L6's (admittedly bios'd pretty cold, about 30watts for the pair) the same output transformer sounds real good (although sooner or latter somethings gona blow, 20 watt ot and 20watt speaker) but hay it sounds great😀
Maybe try running pentode mode with the 6V6's but add a cap from plate to grid for some local degeneration at higher frequencies.
Another option is to add a cap from plate to OPT center tap.
These methods should help tame the highs without the rest of the frequency range being affected which will happen with UL mode.
I tried UL mode for guitar use with 6V6 and EL34 and I don't like it, too Mich like a triode. I am not too sure about the harp but all the harp players I know like dirty amps which leads me to think pentode. Triode or UL could be suitable for big box guitars and jazzy clean tone.
Another option is to add a cap from plate to OPT center tap.
These methods should help tame the highs without the rest of the frequency range being affected which will happen with UL mode.
I tried UL mode for guitar use with 6V6 and EL34 and I don't like it, too Mich like a triode. I am not too sure about the harp but all the harp players I know like dirty amps which leads me to think pentode. Triode or UL could be suitable for big box guitars and jazzy clean tone.
I'm going to populate a pair of pcbs for a two channel amp, and I want the power tubes to be 6V6s.
My choice is to have 23% UL taps and no gnfb, but I have some questions.
I've seen that Fender goes up to 400 Vdc on both plates and screens in pentode mode. They declare to use a primary inductance of 6k6, but from the schematic it's 8k.
On the Fender, with 8k g1=0 is with plates at 35V. That's alot of secondary emission. With 6k6 g1=0 is with plates at 70V. Not much of a difference, so screens stoppers do they work and I can apply the same value to my amp too.
With 23% UL I would like to use the same voltage but with higher Raa: 10 or even 12k (that I'd prefer).
Has anyone ever used a guitar amp with this configuration? How do you expect it to sound?
Thanks
My choice is to have 23% UL taps and no gnfb, but I have some questions.
I've seen that Fender goes up to 400 Vdc on both plates and screens in pentode mode. They declare to use a primary inductance of 6k6, but from the schematic it's 8k.
On the Fender, with 8k g1=0 is with plates at 35V. That's alot of secondary emission. With 6k6 g1=0 is with plates at 70V. Not much of a difference, so screens stoppers do they work and I can apply the same value to my amp too.
With 23% UL I would like to use the same voltage but with higher Raa: 10 or even 12k (that I'd prefer).
Has anyone ever used a guitar amp with this configuration? How do you expect it to sound?
Thanks
Thank you for your reply Ian!gingertube said:
This is one of the two options I have, the other one is 12k with same UL taps. I just would like to know if and how I'll feel the difference between the two Raa.gingertube said:
I remember I played years ago an amp with switchable UL (it was triode-pentode-UL) and it sounded good in UL disconnecting the gnfb, like you suggested. Unfortunately that was not possible with the amp stock.gingertube said:
Good to know, in this case it will be a 3 stage Fender clean and a 4 stager lead without CF. Mosfet loop.gingertube said:
May I ask you at what voltager you run your amp? I would like to go to 400V like with the Fender 65 Reverb (but that one is in pentode). This would also give the possibility to switch from 6V6 to EL34 without too many variations.gingertube said:
I will check if it can be done through cathode bias, without changing anything.
I do not run my amp at 400V.
I can give you some results of two builds.
My own amp runs 340v Va. Fixed bias, 6V6G pair, switchable pentode /Ultralinear Mode , Fixed Bias. 10K Raa (20% UL Taps)
My buddy Neale for whom I built a full bells and whistles amp (Based largely on a London Power Standard) with power scaling and fixed/cathode bias switching runs 350V at 100% power scaling.
For his amp I used a quad of those Sydney AWV Factory 6V6G driving a 3k4 Raa (Marshall) Output Tranny. It delivers around 28 Watts at the onset of clipping with power scale set at 100%. Probably close to 40 Watts in full overdrive.
The 3K4 Raa tranny (equivalent to 6K8 for a pair of output tubes) was just what I had on the shelf and a 4K5 to 5k Raa Output Tranny MAY have been better.
It has Triode/Pentode switching for each of the 2 output tube pairs. (No Ultralinear option) and Fixed Cathode bias option for each output tube pair.
He mostly runs it with one output pair in Cathode Bias, Triode mode and the other pair in Pentode Mode, Fixed bias AND the Power Scaling turned well down such that he is probably getting around 10 Watts max. Also runs the "Limit" Control, which is a post PI Master, down a bit so that he balances a bit of preamp distortion with power tube overdrive.
I can only offer an opinion based upon experience. For 6V6 I suggest you do not want to go above about 350/360 Volts.
6V6 were used in TV sets at up to 1200V peak (15% duty cycle) so they are not fussed by high voltages. Just remember to reduce the current so that anode power dissipation is kept within the 12 Watt Limit.
BUT
You need to consider that for best sound (Gingertubes Opinion ONLY):
I also prefer EL34 at 380V rather than 420 to 450V used to squeeze the last few watts out. This (380V) gives effortless dynamics without strain at 38 to 40 Watts instead of the 50 to 55 Watts of most Cranked Marshalls.
Ditto 6L6 at no more than 400V. So take my recommendations with a grain of salt.
My opinion is that at these slightly lower voltages, you will be 10 to 15 % low on power but 150 to 200% on dynamics and sound.
That is just my opinion and others may well disagree.
My HiFI Amp runs the same Sydney AWV Factory 6V6G into Hammond 1608 Output Trannies (43% UL and 8K Raa) at 340V Va. (Baby Huey design). It does grunge up nicely when pushed hard and a rewire of my Git Amp to the Baby Huey Output scheme is on my TODO list (as a trial).
There have been more than 300 Baby Hueys built since I perhaps foolishly published the design here (could have made some cash by building/selling amps to that design), folk seem to like it for HiFi. I have a sneaking suspicion that it will work well for Guitar too.
Cheers,
Ian
I can give you some results of two builds.
My own amp runs 340v Va. Fixed bias, 6V6G pair, switchable pentode /Ultralinear Mode , Fixed Bias. 10K Raa (20% UL Taps)
My buddy Neale for whom I built a full bells and whistles amp (Based largely on a London Power Standard) with power scaling and fixed/cathode bias switching runs 350V at 100% power scaling.
For his amp I used a quad of those Sydney AWV Factory 6V6G driving a 3k4 Raa (Marshall) Output Tranny. It delivers around 28 Watts at the onset of clipping with power scale set at 100%. Probably close to 40 Watts in full overdrive.
The 3K4 Raa tranny (equivalent to 6K8 for a pair of output tubes) was just what I had on the shelf and a 4K5 to 5k Raa Output Tranny MAY have been better.
It has Triode/Pentode switching for each of the 2 output tube pairs. (No Ultralinear option) and Fixed Cathode bias option for each output tube pair.
He mostly runs it with one output pair in Cathode Bias, Triode mode and the other pair in Pentode Mode, Fixed bias AND the Power Scaling turned well down such that he is probably getting around 10 Watts max. Also runs the "Limit" Control, which is a post PI Master, down a bit so that he balances a bit of preamp distortion with power tube overdrive.
I can only offer an opinion based upon experience. For 6V6 I suggest you do not want to go above about 350/360 Volts.
6V6 were used in TV sets at up to 1200V peak (15% duty cycle) so they are not fussed by high voltages. Just remember to reduce the current so that anode power dissipation is kept within the 12 Watt Limit.
BUT
You need to consider that for best sound (Gingertubes Opinion ONLY):
I also prefer EL34 at 380V rather than 420 to 450V used to squeeze the last few watts out. This (380V) gives effortless dynamics without strain at 38 to 40 Watts instead of the 50 to 55 Watts of most Cranked Marshalls.
Ditto 6L6 at no more than 400V. So take my recommendations with a grain of salt.
My opinion is that at these slightly lower voltages, you will be 10 to 15 % low on power but 150 to 200% on dynamics and sound.
That is just my opinion and others may well disagree.
My HiFI Amp runs the same Sydney AWV Factory 6V6G into Hammond 1608 Output Trannies (43% UL and 8K Raa) at 340V Va. (Baby Huey design). It does grunge up nicely when pushed hard and a rewire of my Git Amp to the Baby Huey Output scheme is on my TODO list (as a trial).
There have been more than 300 Baby Hueys built since I perhaps foolishly published the design here (could have made some cash by building/selling amps to that design), folk seem to like it for HiFi. I have a sneaking suspicion that it will work well for Guitar too.
Cheers,
Ian
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Thank you Ian,
looking at some curves of 6V6 with that amount of DL I was looking indeed between 10 and 12 kOhm Raa, but I was looking at higher voltages. I will definitely try also the lower voltages as you suggest.
Nice, so it's like a Mesa Simulclass. Years ago I thought about a lower power 6V6&EL84 version of it, but.. I still don't know how to chose the best Raa for two different tubes working in different configurations.
Thanks, well receipt!
At the end that's a power that almost no one will use normally, even with the band. It is just how you can use the amp on the spectrum of volumes and, as you were saying, dynamics.
Easiest way: I'll connect 8 Ohm speakers on 4 Ohm amp output of some of my amps and experiment on their sound.
You mean UL plus shunt feedback, or just shunt feedback à la Yves?
I'm sure it will sound perfect for bass amplification (I opened a thread about it), and I'm also sure it will sound well with pentodes instead of gnfb. Indeed one of the projects (that probably will remain on paper for a long time) is build a Mesa-Rectifier-like amp with UL/shunt feedback to improve damping while keeping the PI's raw sound without feedback through it.