Ever since I acquired a batch of Svetlana SV572-3 from a fellow board member (the ever-so-helpful Dhaen, aka John), I have been dreaming of building an all-triode amplifier. My general requirements are for reasonable power (~20W for my moderatly efficient speakers), and an all-triode single ended topology.
I plan to drive the 572 with a interstage transformer coupled 2A3, in a Loftin-White configuration. Now, I must admit, I never heard a L-W anp, so my decision is purely based on what I have read & heard.
Not being a tube design specialist, I am designing this using the 'cut and paste' philosophy. That is to say, I took existing L-W designs, and replaced the output transformer with an interstage xformer (whose primary is the same as the original output xformer's primary), and used that to drive the 572. It seems to make sense to me, at least.
For the PS, I plan to use individual PS's for the 2A3 and 572's, with a Pi (or double Pi) tube rectified configuration.
Perusing my collection of tube articles & magazines, I found 3 L-W 2A3 designs, so I cut & pasted 3 proposals, which I will post here. I would greatly appreciate any and all comments & suggestions!
I plan to drive the 572 with a interstage transformer coupled 2A3, in a Loftin-White configuration. Now, I must admit, I never heard a L-W anp, so my decision is purely based on what I have read & heard.
Not being a tube design specialist, I am designing this using the 'cut and paste' philosophy. That is to say, I took existing L-W designs, and replaced the output transformer with an interstage xformer (whose primary is the same as the original output xformer's primary), and used that to drive the 572. It seems to make sense to me, at least.
For the PS, I plan to use individual PS's for the 2A3 and 572's, with a Pi (or double Pi) tube rectified configuration.
Perusing my collection of tube articles & magazines, I found 3 L-W 2A3 designs, so I cut & pasted 3 proposals, which I will post here. I would greatly appreciate any and all comments & suggestions!
Attachments
SV 572-3
Hi,
Not a Loftin White but take a look anyway:
SEKIDO
And here:
ANDREA CIUFFOLI
The Loftin White circuit has been discussed in *L'Audiophile* many years ago.
Likewise it can be found in a summary book by Mr.J.Hiraga called:
*Initiation aux amplis a tubes* and *Selection de L'Audiophile,Tome 1*
Bonne chance,
Hi,
Not a Loftin White but take a look anyway:
SEKIDO
And here:
ANDREA CIUFFOLI
The Loftin White circuit has been discussed in *L'Audiophile* many years ago.
Likewise it can be found in a summary book by Mr.J.Hiraga called:
*Initiation aux amplis a tubes* and *Selection de L'Audiophile,Tome 1*
Bonne chance,
Loftin-White
Yes, I did read Hiraga's book. That was one of the reasons that I chose the L-W configuration. There is also the O. Asano 2A6 & 2A3 L-W design, on page 79 of the aforementioned book.
My dilemma is that I do not really want to build too many versions of the circuit - I want to select one layout, breadboard it, refine parts selections, and then build it.
Yes, I did read Hiraga's book. That was one of the reasons that I chose the L-W configuration. There is also the O. Asano 2A6 & 2A3 L-W design, on page 79 of the aforementioned book.
My dilemma is that I do not really want to build too many versions of the circuit - I want to select one layout, breadboard it, refine parts selections, and then build it.
Here's mine so far
Hi Igor,
I don't know how much you know of how far I've got so far.
I've been using both channels breadboarded for a couple of months now, and am very pleased with the results.
The metalwork has taken much longer than expected, as I'm using a rather unconventional construction.
I'll post an early schematic of one channel:
Cheers,
Hi Igor,
I don't know how much you know of how far I've got so far.
I've been using both channels breadboarded for a couple of months now, and am very pleased with the results.
The metalwork has taken much longer than expected, as I'm using a rather unconventional construction.
I'll post an early schematic of one channel:
Cheers,
Attachments
The 845 has turned out similar to drive to the 572-3.
As you know I was lucky to get a pair of VV32's (300B on steroids) as drivers. This turned out to be a mixed blessing.
It was more difficult to drive: With a maximimum grid value of 100K, the input stage had to have better drive current capability. This meant investigating mu stages. I'm glad I did. The linearity up to massive voltage swings is perfect. And, unlike some of it's detractors, I think it sounds "sweet".
Once everything is finalized, I'll put it on my web-site for "critisism".
Cheers,
As you know I was lucky to get a pair of VV32's (300B on steroids) as drivers. This turned out to be a mixed blessing.
It was more difficult to drive: With a maximimum grid value of 100K, the input stage had to have better drive current capability. This meant investigating mu stages. I'm glad I did. The linearity up to massive voltage swings is perfect. And, unlike some of it's detractors, I think it sounds "sweet".
Once everything is finalized, I'll put it on my web-site for "critisism".
Cheers,
AH...A MU FOLLOWER AT LAST.
Hi John,
Seems like a good circuit you concocted.
Is the 300B really necessary?
How about a regulator valve (IHT,I know) such as a 6C41 or 6C33-C to drive the 845?
It's just that I feel it such a pity to waste a 300B like that.
Cheers,
P.S.You knew I had to say at least something,didn't you?
Hi John,
Seems like a good circuit you concocted.
Is the 300B really necessary?
How about a regulator valve (IHT,I know) such as a 6C41 or 6C33-C to drive the 845?
It's just that I feel it such a pity to waste a 300B like that.
Cheers,
P.S.You knew I had to say at least something,didn't you?
OnRyoku
Frank,
I can't answer that for sure without trying something else, such as a 2A3. It was the 2A3 that I was considering when I got the oportunity of the VV32B's (biggie 300B's). It's true that Rod Burman did take a second breath when I said I was going to use them as drivers...
Probably, if I'd kept with the 2A3 plan, I'd have been able to use AC heaters for the driver.
My deliberations and philosophy are here if you are interested:
http://www.dhaen.org.uk/vdocs/onryoku.htm
Like everything else, it's not finished yet. But it's a start.
Cheers,
Frank,
Good question.
I can't answer that for sure without trying something else, such as a 2A3. It was the 2A3 that I was considering when I got the oportunity of the VV32B's (biggie 300B's). It's true that Rod Burman did take a second breath when I said I was going to use them as drivers...
Probably, if I'd kept with the 2A3 plan, I'd have been able to use AC heaters for the driver.
Yes, I considered this, but in the end decided on a DHT, partly because of the low distortion, and the fact that I could use a 1:1 transformer.
My deliberations and philosophy are here if you are interested:
http://www.dhaen.org.uk/vdocs/onryoku.htm
Like everything else, it's not finished yet. But it's a start.
Cheers,
Evolution of the Power Supply
First, I would like to thank all those who posted to this thread.
My thoughts are now turning to the power supply. I am considering using two seperate power supplies: one for the 2A3 and its driver tube, and a separate power supply for the 572-3. The intent is to minimize ps-sourced distortion, and maximize weight
Rectification will be tube based.
So far, I have not been able to source a suitable transformer for the 2A3. The only one with 2.5 v secondaries is the Hammond,which is not available with 220V primaries. Ideally, the amp will have dual primaries, allowing world wide operation.
Smoothing will be with pi filters, c-l-c, perhaps dual pi. I am thinking of completely eliminating electrolytic capacitors, and using several(relatively) ac motor start polypropelyne caps. I have a small box of 50 uf 250V caps, which look like they might work.
As soon as I put together a schematic, I will post it, but as always, comments are appreciated.
Gilid
First, I would like to thank all those who posted to this thread.
My thoughts are now turning to the power supply. I am considering using two seperate power supplies: one for the 2A3 and its driver tube, and a separate power supply for the 572-3. The intent is to minimize ps-sourced distortion, and maximize weight
Rectification will be tube based.
So far, I have not been able to source a suitable transformer for the 2A3. The only one with 2.5 v secondaries is the Hammond,which is not available with 220V primaries. Ideally, the amp will have dual primaries, allowing world wide operation.
Smoothing will be with pi filters, c-l-c, perhaps dual pi. I am thinking of completely eliminating electrolytic capacitors, and using several(relatively) ac motor start polypropelyne caps. I have a small box of 50 uf 250V caps, which look like they might work.
As soon as I put together a schematic, I will post it, but as always, comments are appreciated.
Gilid
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