• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

A mystery single ended SV-811 amplifier

pixelriffic

pixelriffic

New Member
This came from a recent estate. Searched the interwebs, and can find no origin. Appears to be kit based. The construction is similar to the Bottlehead kits. I can say that it sounds glorious.

If anyone recognizes it, I'd love to hear.
 

Attachments

  • SET2.jpg
    SET2.jpg
    156.5 KB · Views: 107
  • SET1.jpg
    SET1.jpg
    131.2 KB · Views: 107
Register to hide this ad
What is the stamp on one of the output transformers? And which SV-811 is it? I think that's too complicated for a Bottlehead kit but I could be wrong.
 
Nice find. Looks true DIY to me. If you trace out the schematic please post it here. Perhaps someone would recognize it and provide the provenance of the design.
 
Pretty sure that's DIY, not a kit. Yep, it would be interesting to see the transformer labels.
 
The chokes are Hammond. I see some lettering on the side of one of the OPT's. It looks to be a nice DIY build. Seeing the underside and having the circuit traced out would be cool. I like the dual power supply.
There have been a number of SV-811 amps built by folks over at DIY.
Maybe someone over there would recognize it?
 
Last edited:
The 'which SV-811?' is an interesting one, as that tube was available in several mu variants. SV-811-160 comes to mind and something like a -3 and -12 were also available( I think; might have been the SV-572-xx ) that had a variety of gain/Rp combinations to choose from.

Douglas
 
SV-811-160 would be same as 811A, zero bias for class B (if plate voltage isn't too high). Mainly useful for amateur radio. Svetlana made lower mu versions better suited to class A usage: -3, -10, -20 (suffix is approximate amplification factor, mu)
 
pixelriffic said:
If anyone recognizes it, I'd love to hear.
Click to expand...
I recognize it from eBay. I was tempted, but without knowing which 811 it uses and without seeing the underside to look at the circuit and components, I was less tempted. I would still like to see the circuitry.
 
Tom Bavis said:
SV-811-160 would be same as 811A, zero bias for class B (if plate voltage isn't too high). Mainly useful for amateur radio. Svetlana made lower mu versions better suited to class A usage: -3, -10, -20 (suffix is approximate amplification factor, mu)
Click to expand...

Tom, do you recall if the SV811-160 was happy idling at positive bias/continuous grid current like the 811A is can?

Douglas
 
I would think that positive bias would work at lower B+. Mu is 160, same as 811A, so it should have similar characteristics. I looked at the ca. 2000 Svetlana website last night on archive.org - but the only circuits shown were for the lower mu versions - understandable, since those versions were unique to Svetlana.
 
I'd love to see measurements on a low-voltage push-pull 811A amp. Are the grid current curves sufficiently linear for positive-bias mode? I have a NOS quad of Cetrons that I'd love to light up, but always too many other projects.

Jack
 
They are not what I'd call 'brilliant' Jack. Adequate comes to mind. Per the datasheet I saw on Frank's site anyway, and it is notable for its lack of a set of plate curves at lower current/voltage( like what RCA did for the 6SL7; showing a peak plate current of something like 1 mA anyway ). It is also only a 30W plate. I am going to use another tube for a zero bias amp. 65W per plate too... :)

Douglas
 
PakProtector said:
They are not what I'd call 'brilliant' Jack. Adequate comes to mind. Per the datasheet I saw on Frank's site anyway, and it is notable for its lack of a set of plate curves at lower current/voltage( like what RCA did for the 6SL7; showing a peak plate current of something like 1 mA anyway ). It is also only a 30W plate. I am going to use another tube for a zero bias amp. 65W per plate too... :)

Douglas
Click to expand...
The Cetrons I have are true 811A. A quick look at the curves doesn't reveal anything particularly likable about push-pull at low voltages. Other tubes simply do it better. I originally bought the quad as spares for a kilowatt RF amplifier. I'll probably end up selling them to another ham operator one of these days.
 
pixelriffic said:
This came from a recent estate. Searched the interwebs, and can find no origin. Appears to be kit based. The construction is similar to the Bottlehead kits. I can say that it sounds glorious.

If anyone recognizes it, I'd love to hear.
Click to expand...
This looks like a implementation of a amp from _Glass_Audio_. I decided to build it, as two mirrored monoblocks. I could (over time) dig up the schematic, however I have seen it on the interwebs. Unfortunately mine are rather large, and I don't have a lot of room to set them up. Sad. Lights up nicely though.
 
You must log in or register to reply here.
Back
Top Bottom