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Old 23rd December 2011, 12:25 AM   #221
gabdx is offline gabdx  Canada
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Does anyone know the correct value of the grid resistor? I tried 250k, 75k, and now trying 10k soon. So far the dac is clipping with high distortion when music is playing fortissimo.
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Old 18th October 2012, 01:00 AM   #222
gabdx is offline gabdx  Canada
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Quote:
Originally Posted by Ryssen View Post
And if you donīt like opams,is tfafos the way too go then?
Yes... like in audio note.

Moving Coil etc... - Hifi Collective

You can use this instead of the resistor/capacitor

cap is parallell, resistor i/v, transformer, then another resistor + cap .

---) this goes to tube cathode follower or anode then cathode for more gain.

you can buy the number 450, 496 or 497 from the link.

Please, no opamp!
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Old 18th October 2012, 02:23 AM   #223
gabdx is offline gabdx  Canada
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also check less expensive: SOWTER DAC I/V TRANSFORMERS
Less expensive: From hammond the 140NEx and 140Pex
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Old 9th December 2012, 09:57 PM   #224
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Sorry that I'm so late to this game. I bought a pair of O-netics DAC output transformers from Budp about a year ago and finally got them installed in my Behringer DEQ2496. I used 560ohm series resistors in each leg of the primary with no secondary loading. The bass seemed very rolled off until I jumpered out the series resistors. Now I measure flat output through the bass range compared to 1kHz.

The dynamics are very good and small inner details are much more resolved. But, it seems like the sound gets harsh as I increase the volume. I'm playing at volumes that I've always used but never with this harshness before. I have a low powered PP tube amp. Do you think I'm getting the amp into clipping or near it's limits with the increased dynamics? I have to decrease the volume quite a bit now before this problem subsides. The only thing I've tried so far is adding a 2.2k resistor across the primary since I've seen it mentioned that sometimes a shunt resistor will even out the impedance at higher frequencies.

Thanks,
John
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Old 10th December 2012, 07:14 AM   #225
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It's good to control THD at the output of your amp at the different volume settings, or, at least check the signal form. There might be the case that you got a bit more amplitude with the transformers (if they work like 1:2 or so), and therefore may overload input bias at the tubes drivers.
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Old 12th December 2012, 08:59 PM   #226
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Thanks. I recently corresponded with Budp of O-netcs from whom I bought the output transformers. He gave me some good advice regarding the use of primary side series resistance to control the loading on the DAC. I am making progress. He suggested that in the end the optimal value of resistors for sound quality would be something under half of the recommended resistance. Am doing trials now.

John
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