Cheers all,
I have read all the threads I could find on 6c33c implementations, most of which are SE. I found a couple of semi-interesting PP designs, but I was hoping for a bit more inspiration on what people have done if they have done such a design.
I really like reading about modern designs like what George of tubelabs, Olson/Pimm did with the Karna, Thoersten with his universal SE (legacy?) design and Allen Wright did with his PP300b design. But, alas I am still a relative newbie. I haven't built a tube amp to date, only SS/'switching' amps.
I have some ideas, some inspiration and a small collection of tubes, but I'd like to see other's ideas. I am a mathematician by training, so I am not one to like to take others' work, I like to 'make it mine', that is my nature, but studying from the best brings about the best ideas.
In case it matters, the small collection of tubes I currently have, but I am not against buying more...since I will use them sooner or later...include, 6922/6n1p, 6sn7, 6n6p/5687/7044, 6em8, 26, 45, 6c33c, c3g, c3m, not including rectifiers, regulators, etc. I probably forgot some, but this may help you gain inspiration, to give me insipiration. Again though, I am not set on using any of these tubes, except for the 6c33c's for my first project.
I am cool with buying expensive interstages as long as I can reuse them on future projects, so they have to be adaptable enough, if not then I'd rather do the sand thing with FETs.
I emailed George @ tubelabs about how the general concept of adapting his powerdrive design would work for PP but haven't received a reply. It is possible I fell into his spam bin, or he was too busy. So if anyone want to chime in on how things need to be adapted from going from a SE design concept to PP concept, I'd be appreciative. Not looking for total design, but conceptual hints would be welcome.
I have read all the threads I could find on 6c33c implementations, most of which are SE. I found a couple of semi-interesting PP designs, but I was hoping for a bit more inspiration on what people have done if they have done such a design.
I really like reading about modern designs like what George of tubelabs, Olson/Pimm did with the Karna, Thoersten with his universal SE (legacy?) design and Allen Wright did with his PP300b design. But, alas I am still a relative newbie. I haven't built a tube amp to date, only SS/'switching' amps.
I have some ideas, some inspiration and a small collection of tubes, but I'd like to see other's ideas. I am a mathematician by training, so I am not one to like to take others' work, I like to 'make it mine', that is my nature, but studying from the best brings about the best ideas.
In case it matters, the small collection of tubes I currently have, but I am not against buying more...since I will use them sooner or later...include, 6922/6n1p, 6sn7, 6n6p/5687/7044, 6em8, 26, 45, 6c33c, c3g, c3m, not including rectifiers, regulators, etc. I probably forgot some, but this may help you gain inspiration, to give me insipiration. Again though, I am not set on using any of these tubes, except for the 6c33c's for my first project.
I am cool with buying expensive interstages as long as I can reuse them on future projects, so they have to be adaptable enough, if not then I'd rather do the sand thing with FETs.
I emailed George @ tubelabs about how the general concept of adapting his powerdrive design would work for PP but haven't received a reply. It is possible I fell into his spam bin, or he was too busy. So if anyone want to chime in on how things need to be adapted from going from a SE design concept to PP concept, I'd be appreciative. Not looking for total design, but conceptual hints would be welcome.
Sorry, I got the e-mail, but I received a "warning" about answering e-mail "related to secondary employment" at work. People are getting laid off every week, so I must behave. I can only answer e-mail from home. I give priority to e-mail from customers, and since I have recently been selling TubelabSE boards on a limited basis, I have been rather busy with that. I am in between projects at work (for about 1 more week) so I have been on the forums from work (for now).
There are a few different ways to do push - pull. Some of them are easy to adapt to PowerDrive, and some can not use the PowerDrive concept.
My push - pull amps typically use a differential amplifier as a phase splitter in the first stage. I then use two seperate driver stages, one for each output tube. It is usually the two halves of a dual triode. In a case like this PowerDrive is easy, just use two identical circuits similar to the one in the SE design.
Many push - pull amplifiers use a split load phase splitter that directly drives the output stage. A split load circuit requires (mostly) equal RESISTORS on the plate and cathode of the tube. A ccs can not be used. You can however still use the mosfets to drive the output tubes.
There are other possibilities, and each must be considered on a case by case basis. There is no easy answer that works in all cases.
It is also worth noting that most DHT's remain linear when their grid is driven positive, and more power can be gained by using PowerDrive. Many (but not all) typical audio pentodes become nonlinear when driven into the positive grid region. These do not benefit as much from PowerDrive. PowerDrive will still give distortion reducing benefits, but may not provide any additional output power. I have no experience with 6C33's, so I can't tell you how much PowerDrive can help.
As you can see there are lots of possibilities, It would be impossible to describe adapting PowerDrive to push - pull without more information.
PowerDrive has been the subject of a lot of e-mail. I can not possibly design a PowerDrive circuit for everyone who asks me for one, since some of the parameters are dependent on the rest of the circuit, so I started writing a "cookbook approach to PowerDrive" web page last year. When I realized all of the possibilities, one page became 4 and none of them ever got finished. I have been too busy to work on them at all this year.
No problem George, I know how those things go. I appreciate your response here, and you have given me some food for though already.
I wanted to start this thread to get some thoughts and ideas and eventually some feedback with some sketches of my ideas. I may build up a bench amp based on a done design so that I can makes sure I can get everything to work and then start adapting to my own concept. I could also try a SE design first, for simpicity, it is just that my speakers are all around 90db and I like to play loud hard rock.
I wanted to start this thread to get some thoughts and ideas and eventually some feedback with some sketches of my ideas. I may build up a bench amp based on a done design so that I can makes sure I can get everything to work and then start adapting to my own concept. I could also try a SE design first, for simpicity, it is just that my speakers are all around 90db and I like to play loud hard rock.
My current thinking is to build this amp to stand alone on its own feet in terms of drive and gain, so that no line stage is needed and a simpler magnetic or passive 'preamp' can be used. I am thinking of using a tranformer as phase splitter followed by an input stages followed by a driver stage (possibly 45's) followed by the output stage.
You might look here for some ideas on 6C33C PPs:
http://www.jogis-roehrenbude.de/Leserbriefe/Klaus-6C33C-PP-Monoblock/Push.htm
It is in german though - but schematics are international...
http://www.jogis-roehrenbude.de/Leserbriefe/Klaus-6C33C-PP-Monoblock/Push.htm
It is in german though - but schematics are international...
I'm also looking for a good 6c33c schematic.
Some time ago I bought a pair of Plitron 6c33c Output toroids from a fellow diyaudio member. But I can't find any schematic using this OPT or a similar OPT with 150 Ohm.
Jogis Roehrenbude has some very nice looking schematics, but all the OPT's used are 600 Ohm.
Can I use my Plitron 150 Ohm OPT's in those schematics? Or what things should be changed. I have never build a tube amplifier before, so any advice would be very welcome.
Some time ago I bought a pair of Plitron 6c33c Output toroids from a fellow diyaudio member. But I can't find any schematic using this OPT or a similar OPT with 150 Ohm.
Jogis Roehrenbude has some very nice looking schematics, but all the OPT's used are 600 Ohm.
Can I use my Plitron 150 Ohm OPT's in those schematics? Or what things should be changed. I have never build a tube amplifier before, so any advice would be very welcome.
Hi dr. Strangelove
Can you give more details about this OPT (identification number)? I find it very strange it is rated just 150R...I have seen people using 600R or 1k2...
The phase splitter and drive stage developed through Morgan Jones is a truly irreproachable approach: there is no blocking problem, the swing (about 100VRMS) is enough to drive a pair 845 tube. It uses differential pairs with CCS for perfect balance and cathode followers to drive any miller capacitance. I would say this driver stage can be implemented in a 6C33C PP amplifier without any modification (ie just buy the book and build it) but I am newbee, maybe we should ask SY to give an opionion!
Erik
Can you give more details about this OPT (identification number)? I find it very strange it is rated just 150R...I have seen people using 600R or 1k2...
The phase splitter and drive stage developed through Morgan Jones is a truly irreproachable approach: there is no blocking problem, the swing (about 100VRMS) is enough to drive a pair 845 tube. It uses differential pairs with CCS for perfect balance and cathode followers to drive any miller capacitance. I would say this driver stage can be implemented in a 6C33C PP amplifier without any modification (ie just buy the book and build it) but I am newbee, maybe we should ask SY to give an opionion!
Erik
[Hello Erik,
The Opt is the PAT4144-00 from plitron (under special designs).
http://www.plitron.com/PDF/PB/specs/pat4144-00.pdf
I also found the 150R strangely low. All the other designs use higher. I googled for schematics using these OPT's but nothing. It seems BAT uses these toroids too.
The Opt is the PAT4144-00 from plitron (under special designs).
http://www.plitron.com/PDF/PB/specs/pat4144-00.pdf
I also found the 150R strangely low. All the other designs use higher. I googled for schematics using these OPT's but nothing. It seems BAT uses these toroids too.
Indeed, this is low - even if you would "mismatch" the secondary to get an RAA of, say, 300R (8R Speaker on 4R tap...). Didn't do the math, but guess this either leaves you with no power or pretty bad linearity... Even worse with these high gm tubes is to achieve dc balance - critical with a torrodial OPT. Doesn't really work without constant current sources, imho. Love them SE though - and think about PP myself, but not with a torrodial OPT.
I am using toroidals in PP with 6080's, a similar type of tube. DC balance is critical, but a simple variable cathode resistor takes care of that. I run a pot in parallel with the main cathode resistor to get the variability.
I would think that the only way of getting your 150R outputs to work, would be by using parallel output tubes. I think you would need 4 output 6c33c per channel to get it to work. Would be a meaty but very juice hungry beast. The OTL crowd do it so shouldn't be that difficult.
Shoog
I would think that the only way of getting your 150R outputs to work, would be by using parallel output tubes. I think you would need 4 output 6c33c per channel to get it to work. Would be a meaty but very juice hungry beast. The OTL crowd do it so shouldn't be that difficult.
Shoog
I just looked at the 6c33c datasheet and it gives as a suggested operating point 120V, cathode resistor of 35R, with 550mA (with a staggering variability +/-80mA) of anode current. This gives a plate load requirement of 181R, so at that operating point the transformers would work.
I would think also that since these toroidals are designed for use with these valves so they should be engineered to toloerate slightly above average DC current (though I could be wrong of course).
Shoog
I would think also that since these toroidals are designed for use with these valves so they should be engineered to toloerate slightly above average DC current (though I could be wrong of course).
Shoog
All good points well taken, but the transformers are designed to use with the 6c33c so there must be a usable configuration. Maybe a pair in parallel with something like 120V +B and half the current of 270mA per tube.
I know from my experience with the 6080 that very few people have used them at 135V anode voltage and 100mA per triode - but they work very well at low voltage and high current. I would guess that the same would apply to the 6c33c.
Shoog
I know from my experience with the 6080 that very few people have used them at 135V anode voltage and 100mA per triode - but they work very well at low voltage and high current. I would guess that the same would apply to the 6c33c.
Shoog
Thanks for your replies.
So lowering the voltage and using more (4) tubes would make a reasonlable match?
Hmm.... 4 tubes, I like the idea, but thats a bit more then I had planned... And the toroids are only rated for 80Watts.
Isn't there a way to use only two tubes?
Most OTL's use something like 150V. Would that be a good starting poit using only two tubes?
So lowering the voltage and using more (4) tubes would make a reasonlable match?
Hmm.... 4 tubes, I like the idea, but thats a bit more then I had planned... And the toroids are only rated for 80Watts.
Isn't there a way to use only two tubes?
Most OTL's use something like 150V. Would that be a good starting poit using only two tubes?
Why don't you just call Plitron (or Amplimo in Holland) to find out how this one is supposed to be used? Looking at the parameters, it might be usable in a cathode-follower configuration. According to PPC2, 180V plate, 240mA ea tube would give you about 20W@150R at ~3% distortion. Mismatch to 300R primary impedance would improve the numbers even more. But beware, this will be a pretty challenging project...
Marcus
Marcus
My idea/question was always if Allen Wright's design
http://www.vacuumstate.com/various/dpa300B_brochure_lo-rez.pdf
can be modified to work with the 6c33?
The tube power amp cookbook unfortunately is not (yet) available, which might give more details on the design. Wonder if it ever will be?
http://www.vacuumstate.com/various/dpa300B_brochure_lo-rez.pdf
can be modified to work with the 6c33?
The tube power amp cookbook unfortunately is not (yet) available, which might give more details on the design. Wonder if it ever will be?
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