I plan to use 2 Sovtek 2A3 tubes in parallel for the power amplifier i want to build.....i am starting from ground zero...
I have found few schematics but still i am looking for more ideas ...
I would be very gratefull if somebody can suggest me some more designs that are really really good... not needed to be cheap - the only goal is to be really good design that sound good.....
thanks a lot for any help...
so parellel SE 2A3 design needed
I have found few schematics but still i am looking for more ideas ...
I would be very gratefull if somebody can suggest me some more designs that are really really good... not needed to be cheap - the only goal is to be really good design that sound good.....
thanks a lot for any help...
so parellel SE 2A3 design needed
Hi Sunrise,
http://www.audiodesignguide.com/New2A3/new2A3.html
my prefered, only one penthode driver stage, schematic down the page.
or this with more iron
http://www.audiodesignguide.com/my/pse3.html.
Philippe
http://www.audiodesignguide.com/New2A3/new2A3.html
my prefered, only one penthode driver stage, schematic down the page.
or this with more iron
http://www.audiodesignguide.com/my/pse3.html.
Philippe
hmmmm - not a lot of responses unforunatelly.....
at least this - for parallel 2a3 SE - how many stages??.....2 or 3.... first one to be grounded cathode and the second one cathode follower ... or maybe something like SJS Arcadia amplifier
http://www.users.globalnet.co.uk/~valveamp/images/ARCADIA.GIF
it seems to me that in Arcadia we have a lot more gain than needed for integrated amplifier - but probably i am wrong....not sure....
or maybe something like AN Neiro - there we have SRPP at the input and 5687 as a cathode follower (two 5687 triodes in parallel)....?!
one electron has an interesting project with three 2A3 in parallel....well, i need two in parallel - this might work with two of them right??!
anybody has some comments related 6BL7 tube used in this project....?
http://www.one-electron.com/SEA1_p3.pdf
maybe a loftin white with 12AT7 something like a "Baby Ongaku" from Sound Practices - but i am affraid the this will not be enough to drive 2 pieces of 2A3 in parallel.....
questions questions....
and not many answers....to bad....
at least this - for parallel 2a3 SE - how many stages??.....2 or 3.... first one to be grounded cathode and the second one cathode follower ... or maybe something like SJS Arcadia amplifier
http://www.users.globalnet.co.uk/~valveamp/images/ARCADIA.GIF
it seems to me that in Arcadia we have a lot more gain than needed for integrated amplifier - but probably i am wrong....not sure....
or maybe something like AN Neiro - there we have SRPP at the input and 5687 as a cathode follower (two 5687 triodes in parallel)....?!
one electron has an interesting project with three 2A3 in parallel....well, i need two in parallel - this might work with two of them right??!
anybody has some comments related 6BL7 tube used in this project....?
http://www.one-electron.com/SEA1_p3.pdf
maybe a loftin white with 12AT7 something like a "Baby Ongaku" from Sound Practices - but i am affraid the this will not be enough to drive 2 pieces of 2A3 in parallel.....
questions questions....
and not many answers....to bad....
o.k. - i have found the sch for the parallel 2A3 SE using one D3a penthode connected as triode in front of them....
D3a is a bit problematic to find so i have searched...
I found that E280F is similar and also E180F seems to be usefull....
But there is a problem - can someone suggest me the best operating point for E180F and E280F when connected as triodes and when driving two 2A3's connected in parallel....
D3a is a bit problematic to find so i have searched...
I found that E280F is similar and also E180F seems to be usefull....
But there is a problem - can someone suggest me the best operating point for E180F and E280F when connected as triodes and when driving two 2A3's connected in parallel....
Hello Sunrise !
May be here , where Ciuffolli got them :
http://search.stores.ebay.fr/classi...entsQQfsooZ1QQfsopZ1QQsaselZ166822955QQsofpZ0
R.C.
May be here , where Ciuffolli got them :
http://search.stores.ebay.fr/classi...entsQQfsooZ1QQfsopZ1QQsaselZ166822955QQsofpZ0
R.C.
yes yes.... thanks Ciu...
but i would rather want to use the tube that is not so rare like D3a....
so i have decided to use E180F or E280F (that is actually almost as rare as D3a).....to use them if possible naturally.....
so i am searching now for the best operating point to drive the parallel 2A3...
can somebody help me...
man, this place use to have people that actually helped.... i don't know what happened - maybe summer the vacations are still going and there is not that much people on the web....
don't know,...
but the problem stays to be solved....
so guys, please help if you know how.....thanks in advance...
but i would rather want to use the tube that is not so rare like D3a....
so i have decided to use E180F or E280F (that is actually almost as rare as D3a).....to use them if possible naturally.....
so i am searching now for the best operating point to drive the parallel 2A3...
can somebody help me...
man, this place use to have people that actually helped.... i don't know what happened - maybe summer the vacations are still going and there is not that much people on the web....
don't know,...
but the problem stays to be solved....
so guys, please help if you know how.....thanks in advance...
Still plenty of people out there willing to help. We are a couple of days away from our end of summer holiday and a lot of people are away.
FWIW I am not a big fan of paralleling anything, particularly DHTs in the output stage of an SE amplifier.. I have heard some VERY expensive PSE amplifiers and have always preferred comparable non PSE designs. For about the same amount of money you could build a 300B based amplifier with the same output power.
The D3A in a DRD based circuit with a 300B would make a good, relatively simple amplifier project I think. (I use D3A for all sorts of purposes.) 3K opt.. 60 - 70mA cathode bias, raw supply about 500V, etc.
If you insist on going the 2A3 route you will want an output transformer with about 1.25K - 1.5K primary, tubes operating at 60mA each (120mA total) at an effective Vp of about 250V. Raw dc with cathode bias of 300V. How's that for helpful.
Jack Elliano of Electra-Print has details of the DRD design on his site:
http://www.electra-print.com/
Obviously he can also make the required chokes and transformers depending on where you are.
FWIW I am not a big fan of paralleling anything, particularly DHTs in the output stage of an SE amplifier.. I have heard some VERY expensive PSE amplifiers and have always preferred comparable non PSE designs. For about the same amount of money you could build a 300B based amplifier with the same output power.
The D3A in a DRD based circuit with a 300B would make a good, relatively simple amplifier project I think. (I use D3A for all sorts of purposes.) 3K opt.. 60 - 70mA cathode bias, raw supply about 500V, etc.
If you insist on going the 2A3 route you will want an output transformer with about 1.25K - 1.5K primary, tubes operating at 60mA each (120mA total) at an effective Vp of about 250V. Raw dc with cathode bias of 300V. How's that for helpful.
Jack Elliano of Electra-Print has details of the DRD design on his site:
http://www.electra-print.com/
Obviously he can also make the required chokes and transformers depending on where you are.
kevinkr said:Still plenty of people out there willing to help. We are a couple of days away from our end of summer holiday and a lot of people are away.
FWIW I am not a big fan of paralleling anything, particularly DHTs in the output stage of an SE amplifier.. I have heard some VERY expensive PSE amplifiers and have always preferred comparable non PSE designs. For about the same amount of money you could build a 300B based amplifier with the same output power.
The D3A in a DRD based circuit with a 300B would make a good, relatively simple amplifier project I think. (I use D3A for all sorts of purposes.) 3K opt.. 60 - 70mA cathode bias, raw supply about 500V, etc.
If you insist on going the 2A3 route you will want an output transformer with about 1.25K - 1.5K primary, tubes operating at 60mA each (120mA total) at an effective Vp of about 250V. Raw dc with cathode bias of 300V. How's that for helpful.
Jack Elliano of Electra-Print has details of the DRD design on his site:
http://www.electra-print.com/
Obviously he can also make the required chokes and transformers depending on where you are.
i thought the summer holidays are the problem
heheheheh.....i know that there is allways a lot of smart people that know how to help.... hehehhehe.... related the project.... yes - i would like to go with 2A3 in parallel - rather than with one 300B....
but i was asking for the good operating point for the E180F (or E280F) that can drive 2 2A3's in parallel.....or at least a good operating point for those two driver tubes mentioned.... i figure that E180F would be enough - in triode connection it would probably go with 50Vrms output for 1V (or so) input and that on 10-11mA bias current....right or not???
i am asking questions for E180F (or if it will not be enough for E280F) - hehehehehe
Yvesm said:
Yes, but triode strapped
Yves.
of course.... triode connected
hehehehehehe
sunrise said:
You might want to be able to swing a little more, but you might get away with that. At 10mA, and a 300V B+ your driver plate load is limited to about 10k, for a plate voltage of about 150 on the e180f. Fairly high 2nd harmonic.
http://www.diyaudio.com/forums/attachment.php?s=&postid=234715&stamp=1063412366
You can swing a bit more with a 27-30k load line and lower 2nd, if you drop to about 6mA at 125V. But that may be on the margin for driving the output tube capacitance.
Or, if you don't have sand allergies, you can push 6-10mA at 125-150V with a CCS and have plenty of current drive and voltage swing and low 2nd in the driver. And, if I understand correctly, by using a CCS and connecting it as a u follower (low output impedance), you can eliminate the driver tube bypass cap.
Which sounds best? Up to you, but they will all sound a bit different.
Why not try several different operating conditions for the driver? Resistors are cheap and easy to change. A DN2450 or IXCP 10M45 (or either cascoded) is not expensive either.
Sheldon
Sheldon -
thanks a lot....
that's what i was hoping to hear.....
some tech info....
it seems to me that CCS version will be the best or to use E280F tube connected as triode.....????
what do You think???
i thought that E180F might be a bit not enough....well, well, well..... decisions deciosions....
but the guys are telling on the net that E280F is a bit dry.....
well, maybe to use E180F with CCS after all....
thanks a lot....
that's what i was hoping to hear.....
some tech info....
it seems to me that CCS version will be the best or to use E280F tube connected as triode.....????
what do You think???
i thought that E180F might be a bit not enough....well, well, well..... decisions deciosions....
but the guys are telling on the net that E280F is a bit dry.....
well, maybe to use E180F with CCS after all....
I don't have any direct experience with the 2A3. I take it that you don't either. So leave yourself room to experiment. Start with a very good power supply, with plenty of extra current capacity, and low DCR chokes. Check your designs with PSUD. If you design it for choke input to start, you can increase the voltage by tuning with input caps. Pick some good OPT's.
Then try a couple of different driver/tube configurations. As I mentioned, they are easy to change and not expensive to experiment with. Just give yourself plenty of room to work with. You might even consider making a modular driver section, to make this easier. Look here for inspiration on how to play: http://www.tubelab.com/ You can do the same thing on perf board.
Then you don't have to worry about conflicting opinions on sound. Pick what sounds good to you on your system, in your room.
sheldon
Then try a couple of different driver/tube configurations. As I mentioned, they are easy to change and not expensive to experiment with. Just give yourself plenty of room to work with. You might even consider making a modular driver section, to make this easier. Look here for inspiration on how to play: http://www.tubelab.com/ You can do the same thing on perf board.
Then you don't have to worry about conflicting opinions on sound. Pick what sounds good to you on your system, in your room.
sheldon
The audioroundtable group build forum contains a wealth of discussion on using trioded D3a, E180F, E280F and C3g to drive a 300B.
try
http://www.audioroundtable.com/GroupBuild/messages/1909.html
for starters.
try
http://www.audioroundtable.com/GroupBuild/messages/1909.html
for starters.
heheheh - yes - i have seen this post.... and this post the one to start me thinking about using penthodes for my parallel 2A3... only i wanted to get away with a resistor, not CCS... but it seems that i will have to use a CCS afterall....
can somebody tell me if i will have to disconnect the driver output until the situation with the ccs stabilizes (when powering on and off).....
i am not sure how CCS will behave of power ON... maybe to use a C4S ccs - easier to implement....the components are not so problematic to find for C4S....???
can somebody tell me if i will have to disconnect the driver output until the situation with the ccs stabilizes (when powering on and off).....
i am not sure how CCS will behave of power ON... maybe to use a C4S ccs - easier to implement....the components are not so problematic to find for C4S....???
JJ offers a 40watt plate dissipation "2A3".
Said tube could go 350V B+, 50V cathode bias, 100ma, 3K load. Gives more B+ for resistive plate load in driver. Easier load to drive than pair of other 2A3.
Since budget isnt an issue, sand could also be avoided by using a choke load in the driver, either DRD or otherwise. Not that sand is a bad idea with these demands.
Said tube could go 350V B+, 50V cathode bias, 100ma, 3K load. Gives more B+ for resistive plate load in driver. Easier load to drive than pair of other 2A3.
Since budget isnt an issue, sand could also be avoided by using a choke load in the driver, either DRD or otherwise. Not that sand is a bad idea with these demands.
sunrise said:can somebody tell me if i will have to disconnect the driver output until the situation with the ccs stabilizes (when powering on and off).....
i am not sure how CCS will behave of power ON...
It's always good to analyze your circuit for various power up and failure scenarios. If B+ is live and the driver tube is not conducting, then the full B+ will be seen at the plate of the driver tube. That's also true with a resistor or choke plate load. It won't be a problem with the tubes and voltages here, but the coupling cap should be rated for the full B+, better yet for the full B+ with no current draw.
Sheldon
o.k. - so - first be sure that your tubes are heated well.....
than turn on the plate voltage.....but still - i think that i might get some weird noises with ccs..... i have some when using ccs in the plate of the 12B4 that i have as a preamplifier.....
sure the noises here will be smaller because of the transformer on the output - but how much smaller i am not sure...
oh well..... i will have to try that.....
than turn on the plate voltage.....but still - i think that i might get some weird noises with ccs..... i have some when using ccs in the plate of the 12B4 that i have as a preamplifier.....
sure the noises here will be smaller because of the transformer on the output - but how much smaller i am not sure...
oh well..... i will have to try that.....
sunrise said:o.k. - so - first be sure that your tubes are heated well.....
than turn on the plate voltage.....but still - i think that i might get some weird noises with ccs..... i have some when using ccs in the plate of the 12B4 that i have as a preamplifier.....
sure the noises here will be smaller because of the transformer on the output - but how much smaller i am not sure...
oh well..... i will have to try that.....
I think that sequencing the plate voltage is not necessary at these voltages, and complicates things for little practical benefit. Damage to tubes due to cathode stripping is negligible unless you are dealing with something like high voltage transmitter tubes. After all, rectifier tubes have the full B+ before the filament heats up. Ask SY about the issue. People with much more experience than I have not had problems. I haven't seen any actual reports here either. I'd be more worried about a sharp transient to the CCS.
If you want a switch, a switch on the B+ side will almost certainly give some transient noise. I would put the switch on the primary connection to the supply, so that the charging time of the caps will smooth out the rise time some. Or, of course, use an indirect heated rectifier, either to rectify, as a hybrid bridge, or as an in-line slow switch after a SS bridge or rectifier. In the second case you could use a damper diode.
Sheldon
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