Dear All.
You can find a very nice and simple 12W SE amplifier at:
http://igdrassil.narod.ru/audio/pamps/se6s33s.html
(is in russian, but I hope all be clear)
This schematic use only 2 tubes: 6C33C fo the ouptut, and 6E5P for driver (input = 0.25v)
Instead of 6E5P it is possible to use 6E6P.
I works realy very nice, but take a lot of energy from the mains
You can find a very nice and simple 12W SE amplifier at:
http://igdrassil.narod.ru/audio/pamps/se6s33s.html
(is in russian, but I hope all be clear)
This schematic use only 2 tubes: 6C33C fo the ouptut, and 6E5P for driver (input = 0.25v)
Instead of 6E5P it is possible to use 6E6P.
I works realy very nice, but take a lot of energy from the mains
Konnichiwa,
Well, if I where to insist on using the 6N1P (which I would not, absolutely NOT) I would still suggest a few changes.
Give the 6S33 a cathode follower direct coupled to the Grid(s) (in essence pretty damn near mandatory for fixed grid bias with lowish mu triodes) and use Mosfets or another Valve to cascode and currentsource load the Follower. And make the Follower valve and the second stage something like an ECC99, 5687 or 6N30 while you are at it. Hans posted a suitable design schematic earlier in the thread.
Secondly, you may wish to consider shortening the feedback loop so that it actually has a chance of working and improving the Amp. Take the feedback from the 6S33 Anode and return it to the cathode of the driver valve. This will linearise the output stage notably without causing the usual (sonic) problems found with normal "long" feedback loops.
Finally, I am also coming around to the view of using differential, transformercoupled triodes as drivers, not only for PP Amp's but also for SE Amp's. The driverstage of my current DHT PP Amp uses 5687 or similar and due to suitable use of Valves and Transformers offers a gain of around 64 with a ridiculously high maximum undistorted output of quite a few 100V P-P, the main limit is the interstage transformer which can only andle around 350V P-P @ 20Hz.... The actual Valve stage looks good for > 800V P-P with lowish (< 0.5%) distortion.....
All this is achieved by using in each stage transformers with a 1:2 ratio. Sounds very good too.
Sayonara
morfeas said:
Well, if I where to insist on using the 6N1P (which I would not, absolutely NOT) I would still suggest a few changes.
Give the 6S33 a cathode follower direct coupled to the Grid(s) (in essence pretty damn near mandatory for fixed grid bias with lowish mu triodes) and use Mosfets or another Valve to cascode and currentsource load the Follower. And make the Follower valve and the second stage something like an ECC99, 5687 or 6N30 while you are at it. Hans posted a suitable design schematic earlier in the thread.
Secondly, you may wish to consider shortening the feedback loop so that it actually has a chance of working and improving the Amp. Take the feedback from the 6S33 Anode and return it to the cathode of the driver valve. This will linearise the output stage notably without causing the usual (sonic) problems found with normal "long" feedback loops.
Finally, I am also coming around to the view of using differential, transformercoupled triodes as drivers, not only for PP Amp's but also for SE Amp's. The driverstage of my current DHT PP Amp uses 5687 or similar and due to suitable use of Valves and Transformers offers a gain of around 64 with a ridiculously high maximum undistorted output of quite a few 100V P-P, the main limit is the interstage transformer which can only andle around 350V P-P @ 20Hz.... The actual Valve stage looks good for > 800V P-P with lowish (< 0.5%) distortion.....
All this is achieved by using in each stage transformers with a 1:2 ratio. Sounds very good too.
An externally hosted image should be here but it was not working when we last tested it.
Sayonara
Hello,
I have a pair of 6C33 and I think to build a SE.
What do you think of Antique Sound Lab KMP22-FOX (22W SE 6c33) ?
Here is the schematic http://ptsoundlab.jexiste.fr/depotimg/kmp-22.jpg
I think that output transformer is a 600 or 800 ohms ?
An other interesting amp is Ernst Rößler SE http://www.jogis-roehrenbude.de/Leserbriefe/Roessler-6C33-Amp/Beschreibung.htm .
Do you have opinions ?
Best Regards
Pascal
I have a pair of 6C33 and I think to build a SE.
What do you think of Antique Sound Lab KMP22-FOX (22W SE 6c33) ?
Here is the schematic http://ptsoundlab.jexiste.fr/depotimg/kmp-22.jpg
I think that output transformer is a 600 or 800 ohms ?
An other interesting amp is Ernst Rößler SE http://www.jogis-roehrenbude.de/Leserbriefe/Roessler-6C33-Amp/Beschreibung.htm .
Do you have opinions ?
Best Regards
Pascal
Hi,
Since you ask...
I am not convinced by either one of the schematics you linked to.
IMHO the one as posted by Tubtvr on his site and you'll also find on Claudio Bonavolta's site, is the better thought one.
You also have the added advantage that you can ask Tubetvr's opinion on how it sounded to him.
Cheers,
Since you ask...
I am not convinced by either one of the schematics you linked to.
IMHO the one as posted by Tubtvr on his site and you'll also find on Claudio Bonavolta's site, is the better thought one.
You also have the added advantage that you can ask Tubetvr's opinion on how it sounded to him.
Cheers,
Gentlemen,
How do You feel with the fixed bias in the 6C33C ?!
This wonderful triod, hav one disadvantage - it's current unstability.
That meas that it could be used only with servo loop - shunt resistor - curent sencor, integrator (OP), regulator (another tube or bipolat/mosfet transistor.
Or, as usually used - with automatic bias (cathode resistror with cap).
Look at the link that I'd post some days ago - this is the best 6C33 based SE amplifier by Anatoly Manakov (Russia) I/ve ever see, it's sound is clean and agressive in the same time.
This schematic is very simple and very stable, a lot of people duplicate it with great success.
I don't remember, if russian 6E5P have american/europe analog, so try to get it - it is realy good.
How do You feel with the fixed bias in the 6C33C ?!
This wonderful triod, hav one disadvantage - it's current unstability.
That meas that it could be used only with servo loop - shunt resistor - curent sencor, integrator (OP), regulator (another tube or bipolat/mosfet transistor.
Or, as usually used - with automatic bias (cathode resistror with cap).
Look at the link that I'd post some days ago - this is the best 6C33 based SE amplifier by Anatoly Manakov (Russia) I/ve ever see, it's sound is clean and agressive in the same time.
An externally hosted image should be here but it was not working when we last tested it.
This schematic is very simple and very stable, a lot of people duplicate it with great success.
I don't remember, if russian 6E5P have american/europe analog, so try to get it - it is realy good.
Not bad, it is the only practical way to go.
I have not have had any problems with instability neither in my SE amp, neither in any of the OTL amps I have built.
However, I have noticed some things that are important in order to keep the 6C33C happy:
Burn in the tubes correctly, minimum, 30 minutes with heaters only and then another 30 minutes with 200V anode voltage and 200mA cathode current.
Always use a timer delay for anode voltage, 30 seconds is enough, 2 minutes is safer.
Keep anode voltage below ~200 V
Keep idle dissipation below ~40W or 2/3 of max
Keep resistance in grid circuit below 100kohm
Interesting to note is that 6C33C in SE seems to sound best with ~200V and ~200mA
Use good quality sockets, it seems that there are problems with some types although I haven't experienced any with the sockets I am using, (ceramic, probably russian made).
Taking these precautions I have never had a problem with the 6C33C for up to 6 years use except for one tube that failed during burn in, (it was probably faulty from the factory)
Regards Hans
Hi altor,
interesting project for my pair of 6c33 wich sleep in their boxes. I have some little difficulties with your schematic. Can you help me by saying this to me :
Have you specifications of TC-180 or can you tell me where I can find that ?
What is the value of B+ and B- ?
What are KA226 diodes ? and the value of capacitor between the 4 diodes ?
What are the value of 2 capacitors between 6E5P and 6C33 ?
What is the value of B+ inductor ?
Thank you in advance if you can give me these informations
Best Regards
Pascal.
interesting project for my pair of 6c33 wich sleep in their boxes. I have some little difficulties with your schematic. Can you help me by saying this to me :
Have you specifications of TC-180 or can you tell me where I can find that ?
What is the value of B+ and B- ?
What are KA226 diodes ? and the value of capacitor between the 4 diodes ?
What are the value of 2 capacitors between 6E5P and 6C33 ?
What is the value of B+ inductor ?
Thank you in advance if you can give me these informations
Best Regards
Pascal.
PTSOUNDLAB said:
THis is a power transforme from old color TV, 180W.
2x40v + 2x60v - connected in series, and produse 200V @ 0.4 A
filament for 6c33 - 2x6.3v 4.7a - connected on parallel
flament for 6E5P - 2x6.3v 1.5a - connnected in parallel
280v after the rectifier
400v 1.7A 250ns, I prefere BYV29 or BYD57J ultrafast diodes.
1-2 uF
Don't remember, I'll ask the author.
6C33 SET - Some thoughts (partially baked)
Since seeing about this valve in DVDHack's thread, I've been idly
wondering about it.
This current thread encourages me to post ideas even though they are
far from fully formed - please make allowances for this!
First priority is how to drive the beggar!
I've looked at valve data and several ccts and my opinion is that most
of them seem to miss the point.
I really can't see a 6SL7 (even SRPP) having any chance of driving a
6C33; nor an anode loaded 6SN7; and I'd guess a 6SN7 CF would be
marginal.
If we use a half hearted driver stage, I'd expect a half hearted sound -
and then what's the point of the extra power over a 300B?
My choice is likely to be that old favourite of mine *for this purpose*,
the mu stage. (Fire hose is at the ready Thorsten).
It looks like about 75V bias on the 6C33. I have an active preamp with
plenty of gain and headroom, so I can go for a single driver stage in
the power amp. 50 gain looks enough, so a possible choice of valves is:
E180CC triode - at say 8mA, 175V, -2.5V bias (1.4 watt; limit is 2)
D3a pentode at say 20 to 22 mA (op point tbe)
Suitably configured this should have very low Zout, good current
capability, high bandwidth, and a very linear voltage swing of well
over 100V.
Note that I've seen a similar mu stage used by Bas, driving the little
cousin of the 6C33 - the 6C41.
Now for the PSUs.
No option, must have separate PSUs to run the mu stage at 450V or so,
and about 210V across the 6C33.
Driver stage: valve rectified, unregulated, single supply for both
channels (relying on the high PSRR of the mu stage to give isolation).
Power stage PSU is a problem.
I'm wondering about 6CJ3 damper diode rectifiers as these are good
for almost 2 amps. Voltage drop at 500mA is 20V, which doesn't look
bad to me (we get more across a GZ34 in a 300B amp?); but is this too
much?
Alternative might be hexfreds or HV schottkys?
Then 2 pi filter with low DRC chokes; and if space allows it, I'd
consider splitting the second stage by channel. Offboard PSU is not an
option ....
Biasing of the output valve:
I fancy fixed bias (with pot and test points for bias V and anode I),
as for one thing it eliminates the cathode bypass capacitor, and might
give better sound quality (though I need more info on this point).
However, I'm concerned at mention of runaway, which makes the safer
cathode bias attractive. Cathode bias and Black Gate caps, I wonder?
Any help on this would be apprciated.
Coupling: I'm wondering about grid choke LC coupling. Otherwise I
expect RC coupling, with low value of R which I hope would help keep
the 6C33 stable; also, a well chosen time constant should minimise
effects of any grid current. (This may be the same thing expressed in
different ways?).
OPT: I drew a load line on the curves and guess what, it was 580 ohms.
This seems to confirm the usual choice of 600 ohms. Any suggestions
for make and model would be appreciated; Tango is often mentioned;
are they readily available?
Any advice and suggestions are welcomed.
Since seeing about this valve in DVDHack's thread, I've been idly
wondering about it.
This current thread encourages me to post ideas even though they are
far from fully formed - please make allowances for this!
First priority is how to drive the beggar!
I've looked at valve data and several ccts and my opinion is that most
of them seem to miss the point.
I really can't see a 6SL7 (even SRPP) having any chance of driving a
6C33; nor an anode loaded 6SN7; and I'd guess a 6SN7 CF would be
marginal.
If we use a half hearted driver stage, I'd expect a half hearted sound -
and then what's the point of the extra power over a 300B?
My choice is likely to be that old favourite of mine *for this purpose*,
the mu stage. (Fire hose is at the ready Thorsten).
It looks like about 75V bias on the 6C33. I have an active preamp with
plenty of gain and headroom, so I can go for a single driver stage in
the power amp. 50 gain looks enough, so a possible choice of valves is:
E180CC triode - at say 8mA, 175V, -2.5V bias (1.4 watt; limit is 2)
D3a pentode at say 20 to 22 mA (op point tbe)
Suitably configured this should have very low Zout, good current
capability, high bandwidth, and a very linear voltage swing of well
over 100V.
Note that I've seen a similar mu stage used by Bas, driving the little
cousin of the 6C33 - the 6C41.
Now for the PSUs.
No option, must have separate PSUs to run the mu stage at 450V or so,
and about 210V across the 6C33.
Driver stage: valve rectified, unregulated, single supply for both
channels (relying on the high PSRR of the mu stage to give isolation).
Power stage PSU is a problem.
I'm wondering about 6CJ3 damper diode rectifiers as these are good
for almost 2 amps. Voltage drop at 500mA is 20V, which doesn't look
bad to me (we get more across a GZ34 in a 300B amp?); but is this too
much?
Alternative might be hexfreds or HV schottkys?
Then 2 pi filter with low DRC chokes; and if space allows it, I'd
consider splitting the second stage by channel. Offboard PSU is not an
option ....
Biasing of the output valve:
I fancy fixed bias (with pot and test points for bias V and anode I),
as for one thing it eliminates the cathode bypass capacitor, and might
give better sound quality (though I need more info on this point).
However, I'm concerned at mention of runaway, which makes the safer
cathode bias attractive. Cathode bias and Black Gate caps, I wonder?
Any help on this would be apprciated.
Coupling: I'm wondering about grid choke LC coupling. Otherwise I
expect RC coupling, with low value of R which I hope would help keep
the 6C33 stable; also, a well chosen time constant should minimise
effects of any grid current. (This may be the same thing expressed in
different ways?).
OPT: I drew a load line on the curves and guess what, it was 580 ohms.
This seems to confirm the usual choice of 600 ohms. Any suggestions
for make and model would be appreciated; Tango is often mentioned;
are they readily available?
Any advice and suggestions are welcomed.
Hi,
Optimum operating point in SE is closer to -65V grid and 220V anode, this gives 44W anode dissipation which is about the recommended limit, this operating point has been used in most Japanese made 6C33C SE amps.
Fixed bias is perfectly OK as long as you treat the tube alright, (burn-in, stable heater supply, limited anode dissipation and stable heater supply) the rumours about instability is just that and most likely experienced by people with limited understanding how to treat a tube with high transconductance.
I think actually a 6SL7 could be alright, the total Miller + CG cap is not that high given the low u so you can drive the 6C33C to relatively high frequncies with a 6SL7. As long as you dont drive the 6C33C close to A2 I think even a mu follower should be OK, (mu followers dont like heavy loads) but I prefer a CF direct coupled to the grid, BTW any grid leak of 100kohm or less is safe with a 6C33C.
I am sorry to say but the wonderful Tango XE-20-600S that was specially made for 6C33C in SE is not made any more, actually the -1dB point of that transformer is ~80kHz which is quite exceptional for a SE trans.
Hans
Optimum operating point in SE is closer to -65V grid and 220V anode, this gives 44W anode dissipation which is about the recommended limit, this operating point has been used in most Japanese made 6C33C SE amps.
Fixed bias is perfectly OK as long as you treat the tube alright, (burn-in, stable heater supply, limited anode dissipation and stable heater supply) the rumours about instability is just that and most likely experienced by people with limited understanding how to treat a tube with high transconductance.
I think actually a 6SL7 could be alright, the total Miller + CG cap is not that high given the low u so you can drive the 6C33C to relatively high frequncies with a 6SL7. As long as you dont drive the 6C33C close to A2 I think even a mu follower should be OK, (mu followers dont like heavy loads) but I prefer a CF direct coupled to the grid, BTW any grid leak of 100kohm or less is safe with a 6C33C.
I am sorry to say but the wonderful Tango XE-20-600S that was specially made for 6C33C in SE is not made any more, actually the -1dB point of that transformer is ~80kHz which is quite exceptional for a SE trans.
Hans
I use the Hammond 1640SE 1.25K connecting 8ohm load to the 16ohm secondary tap which brings the primary down to ~600ohms.
Very pleased with the results of the new design (not the one mentioned in the first post of the thread).
http://audio.dynatech.gr/toppage4.htm
Very pleased with the results of the new design (not the one mentioned in the first post of the thread).
http://audio.dynatech.gr/toppage4.htm
Dear Morfeas,
Why don't you try a simple SE - 6C33C amp such as the
one I described on the Valve magazine, at the following sites:-
http://www.valvediy.com/simplexpg1.html
http://www.valvediy.com/simplexreduxpg1.html
http://www.plitron.com/PDF/polisois1957.pdf
More info can be found on Ciuffoli's site
www.Audiodesignguide.com
Look for one of the last banners at the bottom ( DCMB ).
This amp consists in just one 6SN7GT valve as amplifier/driver
and one 6C33C-B power tube per channel.
Very few resistors, no capacitors on the signal path, 15-16 W
output, low THD ( practically just 2nd harmonic ), excellent
slew rate, good damping factor.
Just one extra requirement compared to classic SE amps :-
it needs a dedicated power supply for the driver unit.
You also need a very good OPT, due to the quiescent current
of 250 mA, to get an impressive sound.
Take a look.
Ari.
Why don't you try a simple SE - 6C33C amp such as the
one I described on the Valve magazine, at the following sites:-
http://www.valvediy.com/simplexpg1.html
http://www.valvediy.com/simplexreduxpg1.html
http://www.plitron.com/PDF/polisois1957.pdf
More info can be found on Ciuffoli's site
www.Audiodesignguide.com
Look for one of the last banners at the bottom ( DCMB ).
This amp consists in just one 6SN7GT valve as amplifier/driver
and one 6C33C-B power tube per channel.
Very few resistors, no capacitors on the signal path, 15-16 W
output, low THD ( practically just 2nd harmonic ), excellent
slew rate, good damping factor.
Just one extra requirement compared to classic SE amps :-
it needs a dedicated power supply for the driver unit.
You also need a very good OPT, due to the quiescent current
of 250 mA, to get an impressive sound.
Take a look.
Ari.
67,5W Dissipation!
Dear Ari,
Truly excellent design! very smart too!
I would only like to ask one thing which seems quite obvious, but I just don't get it.
At some point in the article you sugest a B+ of 270V and a quiescent current of 250 mA.
To me this is about 67,5W plate disdsipation! Is this an advisable practice for 6C33, since its maximum plate dissipation is 60W and most people use it at around 40W?
Am i missing something here (obviously)?
Moreover, may I ask the source of such a nice OPT and at what price?
Regards,
Panos
Dear Ari,
Truly excellent design! very smart too!
I would only like to ask one thing which seems quite obvious, but I just don't get it.
At some point in the article you sugest a B+ of 270V and a quiescent current of 250 mA.
To me this is about 67,5W plate disdsipation! Is this an advisable practice for 6C33, since its maximum plate dissipation is 60W and most people use it at around 40W?
Am i missing something here (obviously)?
Moreover, may I ask the source of such a nice OPT and at what price?
Regards,
Panos
Dear Panos,
You are right. In fact I use the 6C33s with 220 mA . I just mentioned 250 mA as a rounded figure and as precaution.
The voltage between anode and cathode should not exceed
265 V . That makes about 60 W dissipation. Who said the 6C33
must work at 40 Watts Pa ? Why ?
I am using them as I stated above and none died so far ( after
several years and more precisely circa 300-400 listening hours
average, during the last four years ). Anyway they cost a fraction of the overestimated 300B.
Regarding the discussions on the possibility of driving a 6C33 with a 6SN7, I assure you that, with the schematics I mentioned, there is absolutely no problem ( if limited to class A and slightly below maximum swing) .
As far as the transformer is concerned you can contact
A2Belectronic@aol.com
You are right. In fact I use the 6C33s with 220 mA . I just mentioned 250 mA as a rounded figure and as precaution.
The voltage between anode and cathode should not exceed
265 V . That makes about 60 W dissipation. Who said the 6C33
must work at 40 Watts Pa ? Why ?
I am using them as I stated above and none died so far ( after
several years and more precisely circa 300-400 listening hours
average, during the last four years ). Anyway they cost a fraction of the overestimated 300B.
Regarding the discussions on the possibility of driving a 6C33 with a 6SN7, I assure you that, with the schematics I mentioned, there is absolutely no problem ( if limited to class A and slightly below maximum swing) .
As far as the transformer is concerned you can contact
A2Belectronic@aol.com
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