Thank you Dave for the suggestion.
I have some 6EM7 tubes and will try them asap.
Enclosed a project of a small amplifier using them. The project comes from a Dutch audiophile named Gerrit Gerritsen and a couple of articles have been published by Elektor ( in Dutch and German ), two years ago.
I only contributed to increase the power output, but the power supply voltage, as you see from the enclosed schematics, becomes rather high.
In the case of DCMB, I hope that the 200V accepted by the 6EM7 will generate enough swing to drive the 6S33 without too high a distortion. In the current schematics of the Duplex, the P.S. voltage of the driver is 420 V, the anode load resistance 10K that results much lower with the parrallel plate resistance of the 6SN7GT (7-8 k) and it prroved low enough not to loose too much high frequency.
All the best.
Ari
Enclosed : schematics of the 2x2W amplifier.
I have some 6EM7 tubes and will try them asap.
Enclosed a project of a small amplifier using them. The project comes from a Dutch audiophile named Gerrit Gerritsen and a couple of articles have been published by Elektor ( in Dutch and German ), two years ago.
I only contributed to increase the power output, but the power supply voltage, as you see from the enclosed schematics, becomes rather high.
In the case of DCMB, I hope that the 200V accepted by the 6EM7 will generate enough swing to drive the 6S33 without too high a distortion. In the current schematics of the Duplex, the P.S. voltage of the driver is 420 V, the anode load resistance 10K that results much lower with the parrallel plate resistance of the 6SN7GT (7-8 k) and it prroved low enough not to loose too much high frequency.
All the best.
Ari
Enclosed : schematics of the 2x2W amplifier.
The lo nu triode is able to swing wider at lower distortion than the med mu triodes that you are currently employing. You may also use the hi mu triode in the envelope to provide additional gain and/or local FB.
Of course if you were to employ plate loaded chokes on the drive tubes then you could crank the current up to 40 mA, your drive swing would double, and the load line flattens out resulting in even lower distortion.
Of course if you were to employ plate loaded chokes on the drive tubes then you could crank the current up to 40 mA, your drive swing would double, and the load line flattens out resulting in even lower distortion.
Thanks for the schematic of the one-tube SE amp. I noted a few issues with it however.
1) The unbypassed 330-Ohm resistor on the output triode cathode circuit will raise the plate impedance; causing a deleterious effect on the damping factor.
2) Just AC Couple the thing and use fixed bias instead of having those electrolytics in the signal path.
3) Better yet follow the advice of the Radiotron Manual and run the triodes push-pull. That BTW is the amp that I am going to build; except I am going to use the compactron 6FM7's.
1) The unbypassed 330-Ohm resistor on the output triode cathode circuit will raise the plate impedance; causing a deleterious effect on the damping factor.
2) Just AC Couple the thing and use fixed bias instead of having those electrolytics in the signal path.
3) Better yet follow the advice of the Radiotron Manual and run the triodes push-pull. That BTW is the amp that I am going to build; except I am going to use the compactron 6FM7's.
Hi Dave,
Thanks for your analysis.
1) Regarding the damping factor versus improvement of the quality (less distortion), I gave priority to the latter. Moreover, some wellknown audiophiles are now questioning the high rates of damping factor, considering that it should not exceed 1.5 - 2 . I am not able to say if they are wrong or right, but am waiting for a paper that will be published sooner or later.
2) From about 10 years I discarded the push-pull topology. I know this statement will raise hell, but it is so, and many friends joined me in this decision, especially after they tried S.E., that they had neglected before, for the reason that they were looking to efficiency/high power.
Now, with the low internal resistance valves and suitable output transformers, getting 12-20 W of output power is no problem, with singlee ended amps.
This power is enough for more than 90% of audiophiles, especially if they use high efficiency ( > 90 db ) speaker enclosures.
The sonic qualities of the single ended are, in my opinion and many others, well over those of push-pull. That's why I enjoy music a lot with my Simplex.
As I suggested in a quite old article ( Valve mgazine - 2001 ) if you are skeptical, just try it. It does not take much and it is worth the effort, at least if you want to be able to express a final judgment.
2) I prefer fixed bias, but not from a power supply source. This means D.C.M.B. ( direct coupling modulkated bias ). However, the schematic I sent you is a suggestion that follows a friend of mine's project. I had to keep the main lines.
I'll continue my answer in a few minutes.
Cheers,
Ari
Thanks for your analysis.
1) Regarding the damping factor versus improvement of the quality (less distortion), I gave priority to the latter. Moreover, some wellknown audiophiles are now questioning the high rates of damping factor, considering that it should not exceed 1.5 - 2 . I am not able to say if they are wrong or right, but am waiting for a paper that will be published sooner or later.
2) From about 10 years I discarded the push-pull topology. I know this statement will raise hell, but it is so, and many friends joined me in this decision, especially after they tried S.E., that they had neglected before, for the reason that they were looking to efficiency/high power.
Now, with the low internal resistance valves and suitable output transformers, getting 12-20 W of output power is no problem, with singlee ended amps.
This power is enough for more than 90% of audiophiles, especially if they use high efficiency ( > 90 db ) speaker enclosures.
The sonic qualities of the single ended are, in my opinion and many others, well over those of push-pull. That's why I enjoy music a lot with my Simplex.
As I suggested in a quite old article ( Valve mgazine - 2001 ) if you are skeptical, just try it. It does not take much and it is worth the effort, at least if you want to be able to express a final judgment.
2) I prefer fixed bias, but not from a power supply source. This means D.C.M.B. ( direct coupling modulkated bias ). However, the schematic I sent you is a suggestion that follows a friend of mine's project. I had to keep the main lines.
I'll continue my answer in a few minutes.
Cheers,
Ari
Cathode Follower 6S33S SE Amp.
Well here she is!!! I wound up doing zero feedback. At first the amp was rather flat sounding but after a few hours it has really shaped up nicely.
The sound is very clean and detailed, against a dead quiet background. This new build has easily 12dB better signal-noise versus the previous build that I posted previously.
And of course it is running an octal front end; also a great improvement over the miniature tubes used in the first build.
I will get the schematics posted soon. In the meantime I am just enjoying...
Well here she is!!! I wound up doing zero feedback. At first the amp was rather flat sounding but after a few hours it has really shaped up nicely.
The sound is very clean and detailed, against a dead quiet background. This new build has easily 12dB better signal-noise versus the previous build that I posted previously.
And of course it is running an octal front end; also a great improvement over the miniature tubes used in the first build.
I will get the schematics posted soon. In the meantime I am just enjoying...
Attachments
Here ya go...I checked the caps, after several hours running none are very hot. Tubes are running only around 250 mA so power diss is under 50W.
The last pic is the guy in China that has the transformers. They are very quiet and having the power transformer custom wound to run the 6S33S amp is nice indeed. Of course I have another set; they take about 3 months on that slow boat from China.
The last pic is the guy in China that has the transformers. They are very quiet and having the power transformer custom wound to run the 6S33S amp is nice indeed. Of course I have another set; they take about 3 months on that slow boat from China.
Attachments
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Congratulation nuvistordave, good looking amp. (THX; and the sound stage on this thing is really to die for. lots of effort and cost over $600 but well worth it.)
If you use another tube amps please share us your experience, and sound differences between 6C33C and the others amp. (That amp behind the 6S33S unit is a KT120 P-P driving Mesa Strategy 400 OPT's in UL configuration)
Can you tell us the name of the speakers that you use? 2 sets; the good ones are home brew 3-way rigs; bought the drivers and crossover components from Madisound. Also have a pair of Klipsch 8" bookshelf units; might have warmed over the crossovers.
The 52V bias on the low mu sections is what I measured and should be about right. The mu is only 5 on those units, so they are going to take a lot of bias with over 300V on the plates.
Oh and BTW on those chassis, which are still available from EBAY seller; the caps are hanging in large holes which the brackets straddle. So they stay cool calm and collected. This was not the first 6S33S amp that I built; the first one I had for 5 years.
If you use another tube amps please share us your experience, and sound differences between 6C33C and the others amp. (That amp behind the 6S33S unit is a KT120 P-P driving Mesa Strategy 400 OPT's in UL configuration)
Can you tell us the name of the speakers that you use? 2 sets; the good ones are home brew 3-way rigs; bought the drivers and crossover components from Madisound. Also have a pair of Klipsch 8" bookshelf units; might have warmed over the crossovers.
The 52V bias on the low mu sections is what I measured and should be about right. The mu is only 5 on those units, so they are going to take a lot of bias with over 300V on the plates.
Oh and BTW on those chassis, which are still available from EBAY seller; the caps are hanging in large holes which the brackets straddle. So they stay cool calm and collected. This was not the first 6S33S amp that I built; the first one I had for 5 years.
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Ari Polisois DCMB amplifier
Hi Midlife,
I'm very interested in the DCMB amplifier and I'm considering to build one. I never heard an Ari Polisois amp and I'm curious what the quality of sound is compared to my Audiomat 6550 Push Pull power-amplifier.
Have you ever compared your amp to a fine commercial amp?
And can you describe the benefits of the DCMB amp in sonic terms?
Looking forward to your answer.
kind regards,
Cambridgedac3, The Netherlands.
Hi Midlife,
I'm very interested in the DCMB amplifier and I'm considering to build one. I never heard an Ari Polisois amp and I'm curious what the quality of sound is compared to my Audiomat 6550 Push Pull power-amplifier.
Have you ever compared your amp to a fine commercial amp?
And can you describe the benefits of the DCMB amp in sonic terms?
Looking forward to your answer.
kind regards,
Cambridgedac3, The Netherlands.
I think it's not the tube that has the drift but the main voltage. I used for 10 years a se 6c33 with fixed bias at 200v/250ma without any problems. Maybe every month or 3 month checking the bias was enough.
Do not use a stabilised fixed bias or use an all stabilised power suply.
Do not use a stabilised fixed bias or use an all stabilised power suply.
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Had to look up that 'DCMB' That is basically what my amp is; it uses 2 stacked supplies and the drive stage is direct coupled to the output stage. BUT since 'Nuvistor Dave' dreamed the circuit up without consulting any references it has a few twists on it.
1) the output stage is being run as a Cathode Follower
2) BOTH supplies are ground referenced; one positive to ground and the other negative to ground.
3) The amp uses fixed bias and it is very stable because it is a Cathode Follower output.
4) NO 40W power resistors and...
5) no regulators; just tubes and iron, which is as thing should be.
1) the output stage is being run as a Cathode Follower
2) BOTH supplies are ground referenced; one positive to ground and the other negative to ground.
3) The amp uses fixed bias and it is very stable because it is a Cathode Follower output.
4) NO 40W power resistors and...
5) no regulators; just tubes and iron, which is as thing should be.
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