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Old 16th March 2006, 06:40 PM   #1401
6h5c is offline 6h5c  Netherlands
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My first impression is: yes.
It's much solid-state-with-lots-of-feedback vs. less solid-state-with-some-local-feedback, and the latter wins. Maybe the next level will be to compare the sound of different types of transistors?

The only drawback is that I have to go look for good decoupling caps again, since there's plenty of DC at the output now . I think i'm going to use a 2u2 Auricap for both, or maybe a BG for the transistor stage? That one can be low voltage .

Ray.
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Old 17th March 2006, 07:24 AM   #1402
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Quote:
Originally posted by 6h5c
My first impression is: yes.
It's much solid-state-with-lots-of-feedback vs. less solid-state-with-some-local-feedback, and the latter wins. Maybe the next level will be to compare the sound of different types of transistors?

The only drawback is that I have to go look for good decoupling caps again, since there's plenty of DC at the output now . I think i'm going to use a 2u2 Auricap for both, or maybe a BG for the transistor stage? That one can be low voltage .

Ray.
This sounds very interesting, keep up the good work

Brent
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Old 17th March 2006, 08:39 AM   #1403
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Quote:
Originally posted by 6h5c
My first impression is: yes.
It's much solid-state-with-lots-of-feedback vs. less solid-state-with-some-local-feedback, and the latter wins. Maybe the next level will be to compare the sound of different types of transistors?

The only drawback is that I have to go look for good decoupling caps again, since there's plenty of DC at the output now . I think i'm going to use a 2u2 Auricap for both, or maybe a BG for the transistor stage? That one can be low voltage .

Ray.
how much dc?

allan
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Old 17th March 2006, 08:57 AM   #1404
6h5c is offline 6h5c  Netherlands
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The tubestage does between 110 and 145V DC, depending on how much current the triodes are biased. The signal is taken from the anodes, so that's obvious :-D.

The transistor stage has about 6V offset at its output. The voltage on the collectors of the differential input stage is about 7V, and that's buffered by a darlington emitter-follower, so minus 2 * Ube.

Regards,

Ray.
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Old 17th March 2006, 09:24 AM   #1405
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Ray- can You give me a few info about Your passive filter?
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Old 17th March 2006, 11:33 AM   #1406
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Quote:
Originally posted by wojtek.l
Ray- can You give me a few info about Your passive filter?
Right here.
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Old 17th March 2006, 12:02 PM   #1407
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Thank You Ray. What do You now prefer - tubs or transistors ?
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Old 17th March 2006, 01:10 PM   #1408
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Hi Ray,

I saw the article on ultranalog.com, but couldn't find the schematic anywhere. Surely you could have done a discrete equivalent of your tube stage?

Cheers,
Phil
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Old 17th March 2006, 03:17 PM   #1409
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Quote:
Originally posted by wojtek.l
Thank You Ray. What do You now prefer - tubes or transistors ?
You're welcome. Actually i've done some listening today. Both stages are very close, and sound very good. I find them both sounding better than the original opamp based filter, that's for sure. But with their own characteristic sound. Of course there are also differences between the components I used that could cause that. At first I used Nichicon Muse (ES) bipolar output caps for the transistor stage, and I was a bit disappointed with the sound. But then I changed the caps to 4,7uF MKC's that I had laying around, and that was a big improvement.

The actual active circuit has become so minimalistic that the other components in there become much more important. So in the end I think that will play a great role in how the sound of either stage will be.

Regards,

Ray.
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Old 17th March 2006, 03:29 PM   #1410
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Quote:
Originally posted by philpoole
Hi Ray,

I saw the article on ultranalog.com, but couldn't find the schematic anywhere. Surely you could have done a discrete equivalent of your tube stage?

Cheers,
Phil
Hi Phil,

The tubestage is not taken from Ultranalog, only the transistor stage. The schematic is here on the second page of the SACD Enhancer article. I changed it slightly to get a bit more output headroom, and put the passive filter stage in front. Here's the schematic I used. But both the tubestage and the transistorstage a similar: following the passive filter is a differential input stage with current sink in the tail to combine both DAC outputs, and in case of the transistor stage a buffer for low output impedance.

Regards,

Ray.
Attached Files
File Type: pdf cd67_enhancer.pdf (65.0 KB, 183 views)
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