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SE SV-811-10 power supply
SE SV-811-10 power supply
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Old 11th March 2018, 06:27 PM   #1
Lewis1 is offline Lewis1  United States
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Default SE SV-811-10 power supply

I've been wanting to build this amp for 20+ years since the Eric Barbour article in Vacuum Tube Valley (I think) came out. One representative schematic is is here: SV811/SV572 SE1.
I have a collection of components gathered together for the power supply section, but I've never designed a power supply and I'd love to have some more eyes taking a look. Using Duncan's Power Supply Designer, it seems like I will get 630V and 430V B+ and B1+, respectively, which should be OK. And fairly low ripple. But I don't know if I have correctly modeled the loads. I've attached the power supply schematic from PSUD. Anybody willing to take a look and critique?
Thanks!
Lewis
Attached Files
File Type: pdf sv811-10 PS.pdf (31.5 KB, 197 views)

Last edited by jazbo8; 28th March 2018 at 08:17 AM.
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Old 12th March 2018, 09:58 AM   #2
211hojbjerg is offline 211hojbjerg  Denmark
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Hi Lewis,
The amp you have likened to is coupled as zero bias. This requires a very stable driver that can drive the 811-10 into A2. Using a C coupling between driver and power tube will give you a pour result in the A2 region.

Best regards
Karsten
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Old 12th March 2018, 04:15 PM   #3
snimater1 is offline snimater1
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Hi. Currently i am building this. If you are not in a harry i will soon post the results of the project.
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File Type: gif 811akairo.gif (10.6 KB, 450 views)
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Old 12th March 2018, 07:07 PM   #4
211hojbjerg is offline 211hojbjerg  Denmark
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Hi,
thatís a nice project, but it will not work with SV811-10.

Best regards
Karsten
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Old 12th March 2018, 08:31 PM   #5
Lewis1 is offline Lewis1  United States
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Karsten, thanks for the input. If I understand correctly, you are talking about the final section that is labelled "RC Filter Section." In the Power Supply Designer simulation, that section drops the voltage down to 430V and also reduces a 7 mV ripple to less than one mV. Is your suggestion to replace that RC filter with just a resistor or maybe a voltage divider?
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Old 13th March 2018, 07:43 AM   #6
211hojbjerg is offline 211hojbjerg  Denmark
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Hi Lewis,
No, Iím only talking about the amp schematic you have linked to.

Best regards
Karsten
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Old 13th March 2018, 09:36 AM   #7
artosalo is offline artosalo  Finland
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SV811-10 seems to be low mu triode:
https://frank.pocnet.net/sheets/164/s/SV811-10.pdf

This maybe causes the confusion, since the "real" 811 is hi mu triode.
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Old 13th March 2018, 03:37 PM   #8
Lewis1 is offline Lewis1  United States
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Thanks to all for the replies! I'm not committed to the schema linked in my original post. I'm also looking at others using a 6BM8 as a driver. I'll pay closer attention to the coupling arrangement.
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Old 13th March 2018, 04:30 PM   #9
PRR is offline PRR  United States
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Quote:
Originally Posted by 211hojbjerg View Post
....it will not work with SV811-10. ...
I agree it looks very dubious. The power tube is nearly zero bias with large positive swings. And with C-R coupling to the grid. At first glance it "must" de-bias itself on every positive peak. The 4uFd cap "sees" 47K on the down-swing and <1K on the up swing. It is a rectifier which will ratchet-down the grid voltage with a 0.2sec recovery time.

I found the original. Vacuum Tube Valley, Issue 5, Fall 1996. Here's a dim scan.

The link that Lewis1 gave is a faithful copy of Barbour's plan. The text gives Barbour's thinking. I trust Barbour >99%... it worked for him. The last page has reviews by other ears, who praise the sound.

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.

All I can think is that the grid impedance of this tube is not that low, and in real listening rarely driven hard.
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File Type: pdf Barbour-SV811-10.pdf (477.7 KB, 100 views)
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Old 13th March 2018, 10:38 PM   #10
jdg123 is offline jdg123  United States
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SE SV-811-10 power supply
I too am gathering materials to build the Barbour 811-10 amp and I have a pretty specific power supply in mind. You can skip the barrier diodes, or, if you like, I can go into further detail as to why they are there in an aside (PM).

The other file is from Glass Audio containing a suggested rework of the front end. Please excuse all the margin notes unrelated...

I am following in the footsteps of SET12 from AudioKarma who's 811-10 build I heard some years back and it's been an inspiration ever since.

Ill be looking for your further posts regarding the 811-10. I'm taking my time with this build, savoring it. I'll post here when it is all done...maybe fall of this year.

Best of luck to you!

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File Type: jpg 500VDC B+ copy.jpg (454.8 KB, 350 views)
File Type: jpg Dan's 6em7 driver copy.jpg (924.3 KB, 353 views)
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