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In Reply to: RE: Any reason I have not seen a fixed bias phono stage??? posted by TomWh on December 09, 2014 at 08:03:04
For all of the reasons given by other inmates plus one big one, sound quality.
I'm sure I've tried most things there is to try in phono stage design and IMHO you can't beat Schottky diodes for bias. Makes life simple because you don't have to bypass and they sound great!
SiC Schottky will give you approx 0.8V and standard is more like 0.2V at the sort of current one might typically use. Stringing them in series does not seem to compromise sound so you should be able to get the voltage you need quite easily.
Naz
Follow Ups:
Hello,
Just to report the result of the Cree diodes mod. I tried them in the phono, DAC buffer, driver stage in power amps in place of the Lithium battery grid bias. The range of current is from 2ma to 12ma.
The diodes are staying! they also make life easy in term of wiring and connection for the cathode circuit.
Thanks.
Excellent.
I also used battery bias before Schottky. I preferred Grid battery bias with Lithium to Cathode with rechargeables but (as you said), Schottkies really made life simple and do not lose out in any way.
Naz
hi, is there a minimum DC current required to pass through these diodes to keep them linear. Any issue with only 1-2ma?
The published data is difficult to read at very low current but IME their knee is quite sharp and dynamic resistance quite low. I have used them down to 0.8mA with no noticeable difference compared to 10-15mA other than a very small forward voltage drop reduction.
Naz
I can find many CREE 15A TO220 packages but no small SIC schotky diodes. What are you using? Thanks, M.B.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
TO220 or TO252 packs. 4A, 600V at 25 deg C.
A really good sounding and robust Schottky.
Naz
Hey Naz I have some csd04060's look really close on data sheet but I do not know what I am looking for. What do you think, the tubes are at 8ma and up?
Thanks Tom
Hey Tom,
At a glance they are almost the same and will be fine. In fact any Cree will most likely exhibit very similar characteristics and will sound great.
Best part about them is they have virtually no sonic signature of their own ... nothing gets lost from top to bottom and nothing is added. Can't beat them for Phono stages IMO and I've done some fairly extensive testing in this department.
Naz
Have you tried a smaller schotky? Did you compare it with a LED? Thanks again. M.B.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
Tried a number of crees and and I couldn't pick a difference. Even tried 5817 with only 0.2V drop but equally good sound. All Schottky diodes sounded much better than standard silicon diodes for some reason and also better than the LEDs I tried though there was some variability in these that I didn't hear in Schottky.
If you try please let us know what you think.
Naz
Thanks NAZ! I sure will. Waiting for parts. M.B.
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare
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