I guess this is well known from people talking about ECC81 ? The circuit is working as a V to I converter between valves and I to V output. This gives a third version of triode not often thought of. That is pentode with shunt local feedback as in phono stages. The high Rp allowing RH amps local shunt feedback to work. RH 2A3 is already triode, maybe it's Rp can be lowered this way? Kitic claimed Rp usually 1K2 of a pentode strapped as a triode became 900R as a shunt pentode ? SE amps often work well with small pentode in and power triode out. The EF184 in triode works very much like a ECC81. In some form of pentode it suggests ideal distortion and better gain. That would also free one to look at other cathode followers. 12BH7A ?
RH Amplifiers: RH2A3 – An Amplifier With a Twist!
RH Amplifiers: RH2A3 – An Amplifier With a Twist!
I tried ECC83's in all kinds of positions, with transistor aid and pure. Reason is: I have quite a lot of NOS ECC83's here (Telefunken, Siemens and some glorious sounding US variations) but I can't use them cos the ECC83 implements it's thin sound on everything, even the worst 6SL7 is better IMO.
A Yamaha amplifier from the 80's measures extremely well in every category and it sounds just horrible. The ECC81 was desigend in first place for VHF. It sounds mechanical with untextured cold mids
Interesting, cos I just tried the EF184 as a 300B driver, yes it sounds even worse than the ECC81 but with the same sound character.
Depends on use. I had an Ultralinear (UL seems somewhat out of favor on the forum) ppEL34 amp with 12AT7 input, 12BH7 splitter driver. Measured and sounded very nice - low, predominate 2nd order, declining higher order.
Of course, that's a feedback implementation. AT7 not such a good candidate for non-feedback single ended.
Sheldon
I tried ECC83's in all kinds of positions, with transistor aid and pure. Reason is: I have quite a lot of NOS ECC83's here (Telefunken, Siemens and some glorious sounding US variations) but I can't use them cos the ECC83 implements it's thin sound on everything, even the worst 6SL7 is better IMO.
A Yamaha amplifier from the 80's measures extremely well in every category and it sounds just horrible. The ECC81 was desigend in first place for VHF. It sounds mechanical with untextured cold mids
Seeing as the ECC81 and ECC83 have high gain can shunt feedback help them ? Alas the tests I did of this seem to be lost. They were interesting. The gain might still be higher than a ECC82. That being so can the balance between cathode degeneration and the shunt feedback be sweet-spotted? That is can the shunt feedabck offset the reduced cathode feedback? When transistors we are happy to think local feedback is the answer to all problems. The fact the ECC81 will work at VHF seems no bad thing ? ECC82 in cascode is interesting. 12BH7 seems to work very well in it's place. No idea if it should? It is tempting to think that an ECC81 with the same gain as an ECC82 should be similar?
The Yamaha amp might drive the grid of EL 34 ( 100 watts rms 8R is about 28 Vrms ). I should sound great? The Yamaha possibly is useless with speakers ? As an op amp it should be fine? The Radford HD 250 sounded very odd. It was called a zero distortion amp ( below what they could measure at the time ). Looking at it's circuit it is hard to see why it was so odd sounding. If I see one cheap enough I will try to cure it. A Sony amp of 170 watts produced 2 watts into 2R on bursts, A NAD 3020 about 92 watts. Unsurprisingly the NAD sounded better. The Quad 303 has current limiting, somehow it sounds very good. It has a very primitive current limiter, it seems good enough to stop damage and work OK. When on my Magneplanars it just gives up when too loud. It is gentle in action, a bit like an over driven triode.
Interesting! I sold all my transistor high-end stuff like Accuphase (OK I admit I still have a P-300 - the first Accuphase from 1974 - still by far the best sounding Accuphase amp ever built). But I always refused to sell my Quad 303, it is broken but new PCB's were ordered from china. Could you tell me which new power transis I could use without much hassle?
One thing, I heard the Radford, a friend of mine bought one, yes indeed, we both found that the sound was odd and kinda uninviting.
Just my 3 pennies: ECC82/12AU7/6SN7/6GC7 sound better than 12BH7.
6L6, EL84, 6550, KT88 all sound much better than the slow and muddy EL34 (bah).
And ALL small triodes sounding better than ECC81, only pentodes sound worse, IMO.
The EL34 is great as a tube regulator, this is the only acceptable position for the EL34 in my rig.
6L6, EL84, 6550, KT88 all sound much better than the slow and muddy EL34 (bah).
And ALL small triodes sounding better than ECC81, only pentodes sound worse, IMO.
The EL34 is great as a tube regulator, this is the only acceptable position for the EL34 in my rig.
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MJ15015G - ON SEMICONDUCTOR - TRANSISTOR, NPN, TO-3 | CPC UK
MJ15015 might be worth trying in the 303. BDY56 was highly thought of, MJ15015 looks similar ( Cricklewood Electronics UK claim to have BDY56 ?!?!? ) . I have a small doubt about ultra fast devices, JLH also. I am sure his advice holds true for 303 as there are some similarities. If you wade through the JLH PDF I think you will be pleased, it covers the same ground. I suspect the 2N3055 from On are fall out 15015 as they are on the same spec sheet ( Non destructive voltage test ? ). The choice of old was 2N3055H or 3055, I think it was said the H was tough but the 3055 had better sound. Looking at the graphs the 15015 SOA is better and the Ft like TIP3055 that was always faster. H was 700 kHz from memory, these look to do 3 MHz +.
http://diagramas.diagramasde.com/audio/Linsley Hood Class.pdf
MJ15015 might be worth trying in the 303. BDY56 was highly thought of, MJ15015 looks similar ( Cricklewood Electronics UK claim to have BDY56 ?!?!? ) . I have a small doubt about ultra fast devices, JLH also. I am sure his advice holds true for 303 as there are some similarities. If you wade through the JLH PDF I think you will be pleased, it covers the same ground. I suspect the 2N3055 from On are fall out 15015 as they are on the same spec sheet ( Non destructive voltage test ? ). The choice of old was 2N3055H or 3055, I think it was said the H was tough but the 3055 had better sound. Looking at the graphs the 15015 SOA is better and the Ft like TIP3055 that was always faster. H was 700 kHz from memory, these look to do 3 MHz +.
http://diagramas.diagramasde.com/audio/Linsley Hood Class.pdf
Thanks Nigel, I know the MJ15015, build them in the P-300 after one side blew up. They really sound good. The original old Toshibas in the P-300 sounded ghostly with much too much space and air - kinda LSD feeling - one friend told me after listening that the P-300 with originals in it sounded like the sirens of Odysseus. Yes, the 3055 sounding slooooow and darkly and somehow depressive like an old british b&w movie from the 50's.
The original Naim NAP 160 was with BDY 56. It sounded rather nice. Strong rumour has it the NAP 160 was going to be the Quad 303 replacement ( Alan Mornington West ? ). When with Quad ESL 57's it was a wining combination. Could be true it was passed over for the Quad 405 as that was Peter Walkers baby. Naim is like Cinderella when with ESL 57. It looses the paper thin quality and sounds very real. No idea why it sounds so false when with other speakers?
Thank you for diverting to 303. The JLH is a good place to be as he had a Williamson and could not cope with going stereo.
I almost wrote to Alex Kitic ( Banned on DIY Alas ) asking if he ever tried a MOS FET in place of the 807 ( most like a FET I suspect in linearity ). It might even be good ( 0.5 C/W heatsink )? ECC81 and shunt feedback slightly like 1938 Schade of RCA . Why not ? I have some Gu 50's, now why didn't he think of them ? Some say a GU in triode looks a bit like 2A3/300B .
Thank you for diverting to 303. The JLH is a good place to be as he had a Williamson and could not cope with going stereo.
I almost wrote to Alex Kitic ( Banned on DIY Alas ) asking if he ever tried a MOS FET in place of the 807 ( most like a FET I suspect in linearity ). It might even be good ( 0.5 C/W heatsink )? ECC81 and shunt feedback slightly like 1938 Schade of RCA . Why not ? I have some Gu 50's, now why didn't he think of them ? Some say a GU in triode looks a bit like 2A3/300B .
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I use non polar caps when the DC bias and signal do not exceed 0.4 V peak. Often it is possible. Even cheap ones work. When measured they do very well as do COG ceramic. Polyester over 100 V also. Mains polyproperlene class X2 also as often they have a 630 VDC rating (e.g. pentode g2 and anode filtering for a driver ). They have to be OK as the things that cause HF loss also cause 275 VAC failiure. I have never tried the Rifa paper types, I suspect they may not be as other paper types. Suntan ( yes ) 250 V polyester are bargain devices ( Rapid UK ) . They even come in at about 1% when saying 5%.
Inside the Naim amp there are two weird things. The LTP is 22K and 1 K. This seems to mimic a single transistor. Could be not having second harmonic was not liked ? Also there is a large amount of compensation that the amp simply doesn't need. I speculated that this super tuned the amp to ESL 57 ? It is not the RCA design as people say. The RCA is more complex and looks to be better. The Sinclair is closer. The Naim sits mid way.
Without any doubt in my mind know the three types of amplifier often thought of helps. RCA ( Sinclair ) all NPN output , Dynaco, PYE Mozart. My advice for a Newby would be these. When valves what do we do about 7199 if Dynaco ( EF 86, ECC82 ?) ? Pye Mozart, is RH 34 better ? RCA, What did Harmon Cardon do? Where it gets interesting is transistor current sources and sinks are used in SE valve amps. Unless voltage gets too high the MJE 340/350 and BD139 are worth trying. FET should not be thought of as automatically better. No LM317 please even if it is nice sounding, A BD139 and LED CCS will be bteer ( LED to avoid Early effect, 1 x 1N4007 if you want it, 3 x 1N4007 is best ) . In a 1960's film the lady was caught as she made the sign of the cross with her left hand in a Catholic church. Some valve people will see a transistor as the same. That's bonkers as the current amplifier linearity of a transistor is excellent ( try a NPN/PNP feedback pair if wanting nearly perfect ) . To my ears cathode followers are not as good when typical types used in commersial amps ( Quad 2/22 ). The Leak that used and anode output and a 30 pF cable was the better way to do it. I suspect if arranged to be like Leak a Varislope and Dynaco ST 70 would be excellent. EF 86, EF86, 7199, 2 x EL34. Shure M44-7 ( too good for most preamps ) Lenco GL75 and ELS 57 . That's 6 devices between LP and Ears. The ESL 57 transformer could be improved as the speakers go way above 20 kHz in themselves. Mr Tim de Paravacine says they are + 3 dB 24 kHz when driven by valves directly. Perhaps 813 at silly voltages?
Inside the Naim amp there are two weird things. The LTP is 22K and 1 K. This seems to mimic a single transistor. Could be not having second harmonic was not liked ? Also there is a large amount of compensation that the amp simply doesn't need. I speculated that this super tuned the amp to ESL 57 ? It is not the RCA design as people say. The RCA is more complex and looks to be better. The Sinclair is closer. The Naim sits mid way.
Without any doubt in my mind know the three types of amplifier often thought of helps. RCA ( Sinclair ) all NPN output , Dynaco, PYE Mozart. My advice for a Newby would be these. When valves what do we do about 7199 if Dynaco ( EF 86, ECC82 ?) ? Pye Mozart, is RH 34 better ? RCA, What did Harmon Cardon do? Where it gets interesting is transistor current sources and sinks are used in SE valve amps. Unless voltage gets too high the MJE 340/350 and BD139 are worth trying. FET should not be thought of as automatically better. No LM317 please even if it is nice sounding, A BD139 and LED CCS will be bteer ( LED to avoid Early effect, 1 x 1N4007 if you want it, 3 x 1N4007 is best ) . In a 1960's film the lady was caught as she made the sign of the cross with her left hand in a Catholic church. Some valve people will see a transistor as the same. That's bonkers as the current amplifier linearity of a transistor is excellent ( try a NPN/PNP feedback pair if wanting nearly perfect ) . To my ears cathode followers are not as good when typical types used in commersial amps ( Quad 2/22 ). The Leak that used and anode output and a 30 pF cable was the better way to do it. I suspect if arranged to be like Leak a Varislope and Dynaco ST 70 would be excellent. EF 86, EF86, 7199, 2 x EL34. Shure M44-7 ( too good for most preamps ) Lenco GL75 and ELS 57 . That's 6 devices between LP and Ears. The ESL 57 transformer could be improved as the speakers go way above 20 kHz in themselves. Mr Tim de Paravacine says they are + 3 dB 24 kHz when driven by valves directly. Perhaps 813 at silly voltages?
No wonder, anything that clouds the SS sound is more relaxing.
The brits understood this, that's why all the Creek, Musical-Fidelity, Onyx, Mission, Sugden and other brit amps sound "nice".
In my next project I am going to do the worst of all things. That is a transistor amplifer driver stage using MPSA92 in LTP and MJE340/350 VAS + CCC. This will run at 1/2 HT ( 2 x 115 V AC in series + circa 320 V ). It wil have a gain of 50 which is about standard. The current 8 mA. It could be just 3 devices if single input MPSA92. This will run 4 x EL 84 is cathode coupled single input. 2 x EL 34s need about 48 V rms to do this. EL 84 should be about half that. The op amp section will have standard voltage feedback which could be 51 K and 1 K. The EL 84 will be either UL or triode with no loop feedback. The anode loads will be 6K6 ( anode to anode ) which is 13K2 as 4 valves ( As a V8 in stereo). I think this will be a hard act to follow if all valve. The op amp should drive 2A3 if someone wanted to get the basics sorted out. I think some trendy valves won't be as good. This op amp should be nearly a wire with gain. The non linear load of a class AB transistor amp nothing like as nice as 4 EL 84 of which it only sees 2 ( about 35 mA per bottle and 310 V ). The other side grounded grid. ECC 99 might be where it ends up .
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