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Old 13th February 2011, 12:08 AM   #861
vega65 is offline vega65  Norway
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pieters autoformer is an excellent performer.
non plus ultra
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Old 22nd February 2011, 03:29 PM   #862
E.T. is offline E.T.  United States
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Quote:
Originally Posted by Vinylsavor View Post
Hi!



Not optimal. That would load the tube too much. The point of transformer coupling (among others) is to give the tube a high impedance load to achieve a load line close to horizontal. I like to load a tube with 5 times it's rp or more.

In your case that would be less than 2 times the rp

better would be a 9:1 output trans like Lundahl LL1689

Thomas


Hi Thomas, thanks for your comments.

Lundahl describes the winding of the LL1689 as 9 : 9 : 1 : 1 : 1 : 1 . Is it possible to hook up the output taps to get 4.5:1 for the pre-outs and 9:1 for the 600-ohm headphone outs?

Is there a multi-tapped OT that could feed the newer headphones, which are often low-impedance and high sensitivity. Say, 30 to 100 ohms. I was originally thionking of a 6as7 for the output, since 30 ohms might be too much for #26???

Hi Thomas, thanks for your comments.

Last edited by E.T.; 22nd February 2011 at 03:36 PM.
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Old 22nd February 2011, 05:35 PM   #863
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Hi!

Quote:
Originally Posted by E.T. View Post
Lundahl describes the winding of the LL1689 as 9 : 9 : 1 : 1 : 1 : 1 . Is it possible to hook up the output taps to get 4.5:1 for the pre-outs and 9:1 for the 600-ohm headphone outs?
Yes, this could be done

Best regards

Thomas
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Old 24th February 2011, 04:44 PM   #864
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hi guys

do you happen to have tube #26 schematic that uses lundahl or sawther output transformer that you would be able to share?

or you could email me on milenn007 at yahoo dot com dot au

thanks in advance
erwin
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Old 25th February 2011, 09:45 AM   #865
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Erwin, Could start with Kanishka's post at:

#26 pre amp

His design uses a 200 Henry anode-load choke. This is an important part of the design, and must be a high quality part, with most of the inductance available at 12 to 15mA, say.

The grid is biased with a 9V consumer alkaline battery - Duracell or Panasonic powerline.

The filament can be heated with constant current [dc], and will sound better with one of my filament heat kits for #26. Don't use ac heat on a 26.

Whether this is the right schematic for you depends in part on what you are driving:

- long cables? with high capacitance?
- power amplifier input impedance?
- how much signal does the power amp expect? Can you alter the gain [DIY valve amps].

With long cables, transformers provide a good solution, but the cost is high for high quality items made by Lundahl or Sowter.
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Old 6th March 2011, 09:43 AM   #866
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Did anyone of you tried to implement a bias control e.g. this from Tentlabs ?

Click the image to open in full size.
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Old 6th March 2011, 10:12 AM   #867
regal is offline regal  United States
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Did anyone of you tried to implement a bias control e.g. this from Tentlabs ?

Click the image to open in full size.


No but planning on trying the salas shunt, check it out I don't see how you could do much better especially if you on a budget like most of us.
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Old 6th March 2011, 10:18 AM   #868
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I use Salas HV-Shunt in my Tube-I-zator with great success!
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Old 6th March 2011, 10:23 AM   #869
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Quote:
No but planning on trying the salas shunt,
Hi Regal,

The Tentlabs bias control has a different function to the Salas shunt. It is to bias a tube. Very useful if you have a push pull amplifier. Or a something like a dht preamplifier that is "universal" so you can use many types of tubes without having to change the cathode resistor. Etc. Etc.

In that sense this would be a competing product: DIYHS Active Bias Supply Module (Single pcb to Control 2 Power Tubes) | Diy HiFi Supply
Diyhifisupply's bias control.

Would be great if someone designs a diy version so us frugalphiles can try them Hint hint nudge nudge wink wink.

I had an article by David Baron in my diymag on just such a thing. But it looks suitably complex that a diy version may not be interesting. And I suppose it might not even be cheaper.
http://www.basaudio.net/pubs/DIYMAG_2006_3_4.pdf

The salas shunt reg is soon te be implemented in my power supply

Last edited by Bas Horneman; 6th March 2011 at 10:27 AM.
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Old 6th March 2011, 10:24 PM   #870
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Quote:
Originally Posted by Bas Horneman View Post
Hi Regal,

The Tentlabs bias control has a different function to the Salas shunt. It is to bias a tube. Very useful if you have a push pull amplifier. Or a something like a dht preamplifier that is "universal" so you can use many types of tubes without having to change the cathode resistor. Etc. Etc.

In that sense this would be a competing product: DIYHS Active Bias Supply Module (Single pcb to Control 2 Power Tubes) | Diy HiFi Supply
Diyhifisupply's bias control.

Would be great if someone designs a diy version so us frugalphiles can try them Hint hint nudge nudge wink wink.

I had an article by David Baron in my diymag on just such a thing. But it looks suitably complex that a diy version may not be interesting. And I suppose it might not even be cheaper.
http://www.basaudio.net/pubs/DIYMAG_2006_3_4.pdf

The salas shunt reg is soon te be implemented in my power supply
Hi Bas,

I've been working at a solution to the PP biasing problem, too. Maybe I can aim for the same ballpark of cost as the filament regs - do you think that will be frugal enough??

I don't like the microcontroller idea much. Won't it get a virus?
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