Hi!
I would like to buid a simple and good PP amp for reference and to listen and demonstrate the sound of the PP tube amps.
I found a couple (or 3-4-5
) of interesting circuits, but I don't know which one is the best....
Here are the competitors:
- Mullard 7W classic amp
- Audio Innovation 300 Mk2
- Svetlana 6BM8 (from Sansui)
- No name (suggested by Sjef)
- Rainer zur Linde amp
Has somebody experiences with these amps?
Which one can operated in Ultra Linear mode and is it worth it?
For the output transformator I thought on the Hammond 1620.
Greets:
Tyimo
Here is the Mullard:
I would like to buid a simple and good PP amp for reference and to listen and demonstrate the sound of the PP tube amps.
I found a couple (or 3-4-5
) of interesting circuits, but I don't know which one is the best....Here are the competitors:
- Mullard 7W classic amp
- Audio Innovation 300 Mk2
- Svetlana 6BM8 (from Sansui)
- No name (suggested by Sjef)
- Rainer zur Linde amp
Has somebody experiences with these amps?
Which one can operated in Ultra Linear mode and is it worth it?
For the output transformator I thought on the Hammond 1620.
Greets:
Tyimo
Here is the Mullard:
Attachments
None of the above (really onlt variations on 2 topologies).
Yves & Gingertube worked out an ECL86 PP with a Long Tail Pair loaded by a CCS and RH style (plate-to-plate) feedback.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53969
dave
Yves & Gingertube worked out an ECL86 PP with a Long Tail Pair loaded by a CCS and RH style (plate-to-plate) feedback.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53969
dave
I'm having really good result with the attached schematic of my own design. I'm using it as a headphone amp, but by choosing the correct output transformer you should hget good performance with speakers.
Fully differential from input to output. No cathode bypass on the input LTP. Differential output stage with self balancing bias circuit.
Based on Gary Pimms Tabor circuit. I love listening to it.
PS. R11 should be 800R.
Shoog
Fully differential from input to output. No cathode bypass on the input LTP. Differential output stage with self balancing bias circuit.
Based on Gary Pimms Tabor circuit. I love listening to it.
PS. R11 should be 800R.
Shoog
Attachments
Hi Tyimo,
I would suggest to add the German Klein+Hummel Telewatt VS55 circuit to your list. Klein+Hummel (still) is a producer of broadcasting & studio gear and back in the old times also had a line of amps for demanding private customers.
I once had such a VS55 on my bench for restauration, which thaugth me a *lot* on professional circuit design; it has some very interesting aspects almost nobody cares about nowadays for some unknown reasons.
But you can find pictures, description and schematic here at this link.
Sound is outstanding for an amp using "sh*tty TV tubes" like ECL82/6BM8, I can asure you.
A problem for your project will be that the Hammond OPTs you have in mind quite likely don´t come anywhere close to the quality of the OPTs like being used in a K+H VS55 amp or comparable gear. In this regard, you should use really good OPTs in the first place when heading for a "reference" class project
Regards,
Tom
I would suggest to add the German Klein+Hummel Telewatt VS55 circuit to your list. Klein+Hummel (still) is a producer of broadcasting & studio gear and back in the old times also had a line of amps for demanding private customers.
I once had such a VS55 on my bench for restauration, which thaugth me a *lot* on professional circuit design; it has some very interesting aspects almost nobody cares about nowadays for some unknown reasons.
But you can find pictures, description and schematic here at this link.
Sound is outstanding for an amp using "sh*tty TV tubes" like ECL82/6BM8, I can asure you.
A problem for your project will be that the Hammond OPTs you have in mind quite likely don´t come anywhere close to the quality of the OPTs like being used in a K+H VS55 amp or comparable gear. In this regard, you should use really good OPTs in the first place when heading for a "reference" class project
Regards,
Tom
All my previous experience with the ECL82 produced a harsh quality which suggested oscillation or overload. This is a difficult tube to get to sound nice, and I have read variously of people having to try many different configurations before they got something they could live with.
I think one secret is to drive the triode well within its comfort zone, rather than trying to kill gain by application of feedback later on. This always runs something of a risk of swamping the anode current with feedback current such that the quality of the triode becomes lost. This is why I came up with the idea of a step down input transformer. Seems to work very well.
i almost gave up on this valve before i came up with my current circuit. Also I found that Russian made valves sounded a lot smoother than the NOS Mullards which I tried.
Shoog
I think one secret is to drive the triode well within its comfort zone, rather than trying to kill gain by application of feedback later on. This always runs something of a risk of swamping the anode current with feedback current such that the quality of the triode becomes lost. This is why I came up with the idea of a step down input transformer. Seems to work very well.
i almost gave up on this valve before i came up with my current circuit. Also I found that Russian made valves sounded a lot smoother than the NOS Mullards which I tried.
Shoog
Tyimo said:
One thing i have to mention now that i've noticed the title is ECL82 not ECL86, is that with the ECL86 you need a bit more gain off the LTP than the triode section of the ECL82 can give.
With ECL82 you'd need to change the feedback (easiest is to just eliminate it and triode the output stage, but you are now down to 3-5W (probably glorious thou) or as suggested by gingertube in a thread on using the RH topology on a SE RHECL82, you cascode the front end either withanother tube or FETs. The cascode does give huge gain, and high output impedance, which gives lots of flexibility for the RH-style feedback scheme.
dave
Shoog said:
Very good idea... what kind of ratio do you think? It would also reduce (or eliminate the need for the CCS in the LTP tail.
Do you think any of the trafos here could be pressed into service?
http://www.edcorusa.com/products/transformers/wsm/index.html
http://www.edcorusa.com/products/transformers/xs/xs1100.html
dave
Its an extremely undemanding job for a transformer so the range is probably quite wide. I used a microphone transformer with a step down of 9:1. This works very well, and helps to keep the triode from any chance of overloading. Anything greater than 4:1 would be ideal.
None of the first linked transformers seem ideal, but I would say that the second one would definately make a good candidate.
Haven't you got any suitable microphone input transformers from pulled amps. These are extremely good quality and if their like the ones I have, they come in round cans which mount well on the case.
I have used grid leak bias with a single 10Meg resistor on the centre tap. I only have a relatively small resistor below that to finish off the tail as their are no cathode resistors.
Shoog
None of the first linked transformers seem ideal, but I would say that the second one would definately make a good candidate.
Haven't you got any suitable microphone input transformers from pulled amps. These are extremely good quality and if their like the ones I have, they come in round cans which mount well on the case.
I have used grid leak bias with a single 10Meg resistor on the centre tap. I only have a relatively small resistor below that to finish off the tail as their are no cathode resistors.
Shoog
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