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SE SV-811-10 power supply
SE SV-811-10 power supply
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Old 14th March 2018, 12:03 AM   #11
Lewis1 is offline Lewis1  United States
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jdg,
Interesting stuff. I flipped through all the VTV issues this afternoon looking for a follow-up, because I remembered that there was one. Just didn't realize it was in a different mag! I'll have to pull out my stack of GAs to see if I have that issue.
Pardon my ignorance, but what are the 6DEAs in your PS schematic?
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Old 14th March 2018, 01:57 AM   #12
Lewis1 is offline Lewis1  United States
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NM, I get it; it's a 6DE4. Didn't mean to dis your penmanship!
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Old 14th March 2018, 06:59 PM   #13
w5jag is offline w5jag  United States
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Quote:
.....
It is worth noting that the performance report shows peak power higher than continuous. As expected for a de-biasing amp. However 7 Watts continuous is not a small amp, and speech/music is far from continuous. ....
My notes show that on a modified TubeLab SE board, with SV 811-10 I was getting 9.5 watts continuous at 1 KHz. Idle power was only thirty (30 ) watts. OPT was Hammond 125ESE at 5K, 445 volts on the plate, 67 mils. Lots of power left on the table.

Tubelab's Powerdrive will drive the ever loving snot out of these things. I wouldn't even fool with a cathode follower. My amp is torn down for overhaul and a bigger power supply, unfortunately other projects have moved ahead of it.

Win W5JAG
Attached Images
File Type: jpg TSE_811-10_1kHz_sine_yee_ha.jpg (436.5 KB, 213 views)

Last edited by w5jag; 14th March 2018 at 07:06 PM.
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Old 14th March 2018, 07:20 PM   #14
w5jag is offline w5jag  United States
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Quote:
.... I found the original. Vacuum Tube Valley, Issue 5, Fall 1996. Here's a dim scan.
There are also at least three ( 3 ) technical bulletins worth taking a look at: Svetlana U. S. nos. 8, 9, and 46, describing various implementations and technical details of the SV 811-X / 572-X tubes.

I have them, unfortunately they are in HTML format. I note that when I click on a picture link, it takes me to the Internet Wayback Machine, so they can probably be accessed by going there, and pulling up the old Svetlana website .....

Win W5JAG
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Old 15th March 2018, 12:43 AM   #15
Lewis1 is offline Lewis1  United States
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The full write-up starts in Glass Audio Volume 8, Number 3 (1996) and then Eric Barbour has a follow-up with some specific circuit changes in Volume 9, Number 5 (1997). Seems like the VTV article was sort of a side thing. Much more detailed information in Glass Audio articles. In fact, the GA articles read much like a construction guide, along with the discussion of the how and why of the circuits. I have those two issues and I'm now re-experiencing the excitement I felt when I first started planning this project. Definitely moving forward this time! Let me know if you want any info from the two GA articles or the VTV article.
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Old 15th March 2018, 10:26 AM   #16
snimater1 is offline snimater1
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Quote:
Originally Posted by 211hojbjerg View Post
Hi,
thatís a nice project, but it will not work with SV811-10.

Best regards
Karsten
Yes this is for 811a.
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Old 17th March 2018, 03:26 PM   #17
Lewis1 is offline Lewis1  United States
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Default Some more SveltanaSV811 docs

Here's a link to a directory of archived Svetlana tech bulletins:
Svetlana Technical Bulletins
And several of them related to the SV-811 attached as pdf docs. Thanks to w5jag for the idea!
Attached Files
File Type: pdf sv811-10 PS.pdf (31.5 KB, 31 views)
File Type: pdf SV tech bulletin 8.pdf (204.4 KB, 38 views)
File Type: pdf SV tech bulletin 9.pdf (176.8 KB, 33 views)
File Type: pdf SV tech bulletin 36.pdf (165.6 KB, 32 views)
File Type: pdf SV tech bulletin 46.pdf (184.2 KB, 39 views)
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Old 17th March 2018, 04:18 PM   #18
Diogenio is offline Diogenio  United States
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I have built countless different implementations of the SV-811-10 amplifier, and I can say that ALL of them sounded fantastic. The earliest Barbour driver circuit used capacitive coupling to the 811 and provided about 6 clean watts. Sounded amazing into high efficiency speakers.

Barbour later added a cathode follower to the driver, it raised output to 8 - 9 watts and also sounded wonderful.

THE VERY BEST implementation for running A2 on a zero-bias triode is either a cathode follower that returns to a NEGATIVE SUPPLY, or a MOSFET equivalent such as the TubeLab driver board. I got 15 CLEAN watts continuous out of my SV-811-10 using a 6L6 follower that was running balls out at 50 mA idle! It is the best-sounding amp I've ever owned, and many of my audiophile friends agree.

As I was developing the CF, I started with smaller power tubes such as 6V6, and kept increasing idle current, then stepped up to larger and larger tubes with more current each time. When I finally got to the 6L6 I stopped. In my mind, I had arrived at what I was seeking.

The SV-811-10 zero bias tube is an unsung hero, the sound quality if driven properly is astounding.

One other note, the longevity of those SV-811-10 tubes is incredible. I ran my first pair at least 8 hours per day for over two years and they still sounded and tested fine on my TV-7 D/U transconductance tester!

Last edited by Diogenio; 17th March 2018 at 04:21 PM.
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Old 17th March 2018, 05:47 PM   #19
Lewis1 is offline Lewis1  United States
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Diogenio, any chance you could share a schematic of your 6L6 cathode follower implementation?
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Old 17th March 2018, 06:05 PM   #20
Diogenio is offline Diogenio  United States
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Lewis, I recently moved to another state, so my notebook is still packed away. The implemention is pretty simple. The cathode of the 6L6 follower is connected to a power resistor as usual. Instead of the resistor bottom leg connecting to ground, it is connected to a well-filtered, negative HV supply...I think in my case it was around -300 VDC. The objective is to set idle current through the tube so that the cathode is sitting at ZERO volts, which then connects directly to the grid of the SV-811 power tube...direct coupled, no cap! Remember, the SV-811 wants it's grid at approximately zero volts for proper operation at ~ 100 mA idle. You need to add a simple bias adjust voltage to the 6L6 grid, which in turn will set the cathode at 0V +/- whatever you want.

The beauty of this arrangement is that as the 6L6 conducts, the cathode can swing both positive AND negative in a symmetrical manner. It extracts maximum swing from the driver, and yielded 15 W RMS output in my setup. Clipping was also symmetrical. It sounded great.

With -300 VDC on the resistor, and 0 VDC at the cathode, at 50 mA this works out to a 6k ohm resistor for the cathode follower. It will dissipate 15 watts idle, so use a 25 W resistor! Imagine throwing away 15 watts in the driver just to get 15 W out of the power tube? It's inefficient alright...but sounds fantastic.

You can do the same thing with a power MOSFET, as done by TubeLab in his circuit. Don't know if it sounds much different. I just like the look of all tubes.

Don't be afraid to experiment on a breadboard.

Last edited by Diogenio; 17th March 2018 at 06:13 PM.
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