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Old 12th March 2011, 12:28 AM   #21
amhlee is offline amhlee  Hong Kong
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Originally Posted by Marra View Post
Took the top off my Xono built with Ralf Stens pcb's to check the bias setting. I reset to 0.35v it had drifted a bit; when I checked the dc offset it was fluctuating wildly; +- 100mv plus on both sides of the 10uf output caps and could not be adjusted much with the trimmers. Is this something to be concered about? Any advice/pointers as to what to check would be much appreciated. TIA.

It is a little bit high , are you using 2sk389 or 2sk170 ? Look like it is the matching of the transistor.
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Old 12th March 2011, 03:59 AM   #22
Marra is offline Marra  United Kingdom
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Originally Posted by amhlee View Post
It is a little bit high , are you using 2sk389 or 2sk170 ? Look like it is the matching of the transistor.
I am using 2sk389.
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Old 12th March 2011, 01:57 PM   #23
dot is offline dot  Canada
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At the risk of stating the obvious, I find the voltages unstable while the unit warms up or without operating in an enclosure. Thermal instability.(?) That said I have found the Sten xono clone boards to be the best sounding phono preamp I have heard. It bested the phono section of a Spectral DMC20. (Just my opinion, mileage may very.)
Cheers, Glenn
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Old 12th March 2011, 02:17 PM   #24
Marra is offline Marra  United Kingdom
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Originally Posted by dot View Post
At the risk of stating the obvious, I find the voltages unstable while the unit warms up or without operating in an enclosure. Thermal instability.(?) That said I have found the Sten xono clone boards to be the best sounding phono preamp I have heard. It bested the phono section of a Spectral DMC20. (Just my opinion, mileage may very.)
Cheers, Glenn
Thanks Glen; yes I realise that things do not settle down for quite a while with this phono stage. It has been out of use for some months what with one thing and another so I thought I'd better check things again before connecting it back in my system and for some reason the output offset won't settle. Other voltages check out .
I must agree this is one fine sounding phono amp; I used it for some months last year before the system had to be disconnected.
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Old 14th March 2011, 01:43 AM   #25
amhlee is offline amhlee  Hong Kong
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Look like that some the transistors/ resistor are not well match. But it does not really matter as there are caps in the output to filter out. Pass does not design this as 0mv out, Mine has a full matching set on both transistor and resistor, I am able to achieve 10 mv output.
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Old 14th March 2011, 02:51 AM   #26
Marra is offline Marra  United Kingdom
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Originally Posted by amhlee View Post
Look like that some the transistors/ resistor are not well match. But it does not really matter as there are caps in the output to filter out. Pass does not design this as 0mv out, Mine has a full matching set on both transistor and resistor, I am able to achieve 10 mv output.
Unfortunately these readings are on the output side of the 10uf caps
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Old 14th March 2011, 06:21 AM   #27
Zen Mod is offline Zen Mod  Serbia
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you don't have bleeder resistor at that side ?
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Old 14th March 2011, 09:57 AM   #28
Marra is offline Marra  United Kingdom
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you don't have bleeder resistor at that side ?
No its not that there is a 100k resistor to ground after the capacitors.
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Old 14th March 2011, 10:04 AM   #29
Zen Mod is offline Zen Mod  Serbia
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if you have bleeders at output cap's side , then something is wrong either with your DMM or your caps
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Old 14th March 2011, 11:46 AM   #30
Marra is offline Marra  United Kingdom
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if you have bleeders at output cap's side , then something is wrong either with your DMM or your caps
I'll try a different DMM before taking things apart.
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