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Old 20th June 2012, 10:26 PM   #861
weskoki is offline weskoki  Europe
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Whenever i hear my records on much better set up i get the same impression.Music seems slower!Not like transients are slow but the tempo of the music seems different.
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Old 29th June 2012, 10:14 PM   #862
sonnya is offline sonnya  Denmark
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i did some changes that affected the hum level.

In the first test there was no hum.

But because we raised the current through the input pair and changed it to a CFP pair we need PMBFJ174 (PMBFJ111) instead of PMBFJ175 (PMBFJ112) which i did not have in stock. So i removed the cascode for the input pair.

This added hum as the output impedance of the input pair was lower.

But besides from that it works very very well. Better than i believed myself.

- Sonny
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Old 29th June 2012, 11:20 PM   #863
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Quote:
Originally Posted by sonnya View Post
i did some changes that affected the hum level.

In the first test there was no hum.

But because we raised the current through the input pair and changed it to a CFP pair we need PMBFJ174 (PMBFJ111) instead of PMBFJ175 (PMBFJ112) which i did not have in stock. So i removed the cascode for the input pair.

This added hum as the output impedance of the input pair was lower.

But besides from that it works very very well. Better than i believed myself.

- Sonny
Yes, it is much better when cascoded with j-fets, I did a lot of practical tests on CCS-s and input plus VAS gain stages. Every time tracking cascodes were in use the results were better regarding bandwidth as well at noise level, more stable also.

I am impressed how only two stages amp of yours is well performed because it is only powered VAS if we look to normal VAS schematic.

I decided as always, that my amps also have normal output stage after VAS and at least two pairs of power devices at +/-60 V, to use benefit of std 63 V ELCO-s.

Now I am at final QC of CSA PCB-s which will go into production next week.

Regards Andrej
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Old 30th June 2012, 02:47 AM   #864
MiiB is offline MiiB  Denmark
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Sonny I think your result is marvelous... Truly outstanding mids and highs. In this respect it's clearly better than my current mirrored version of the SSA, that in return is a true killer in the base. I think I'll take the mirrors away to see how a simpler resistor loaded VAS performes.. hope to find your resolution and sparkle in the mids and highs...

Always on the the track to something better...
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Old 30th June 2012, 11:35 AM   #865
sonnya is offline sonnya  Denmark
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Thanks Michael.

If i was you i would try replacing the drivers.

I use mirrors too. you know.
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Old 30th June 2012, 02:48 PM   #866
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by Lazy Cat View Post
Yes, it is much better when cascoded with j-fets, I did a lot of practical tests on CCS-s and input plus VAS gain stages. Every time tracking cascodes were in use the results were better regarding bandwidth as well at noise level, more stable also.

I am impressed how only two stages amp of yours is well performed because it is only powered VAS if we look to normal VAS schematic.

I decided as always, that my amps also have normal output stage after VAS and at least two pairs of power devices at +/-60 V, to use benefit of std 63 V ELCO-s.

Now I am at final QC of CSA PCB-s which will go into production next week.

Regards Andrej
I am also surprised How well it works.

The cascodes does a good job. You could send a screenshot if you want me to look at your pcb design.

I think 63V elco for 60V supply is a bit underrated. I would prefer at least 80V.

Last edited by sonnya; 30th June 2012 at 03:18 PM. Reason: Sentence added.
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Old 30th June 2012, 07:32 PM   #867
sonnya is offline sonnya  Denmark
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Michael i Think you should be proud of your latest layout. It looks good and it does Sound good as well.

Andrej i Think we need to meet some day. Your assembly skills looks good. Very good.
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Old 30th June 2012, 08:36 PM   #868
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Thanks Sonny, experiences from the past should make some difference hehe

SSA is small 30 x 30 x 12 cm, 20 kg, but it rocks very hard, Piegas can be loud as hell.

Yes it would be nice to meet you guys some day, probably me driving across Europe later this year, of course with CSA in the car.


Micheal could you show us some photo of your SSA amp, I'm really curious ...
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Old 1st July 2012, 03:18 AM   #869
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Lazy Cat View Post
SSA is small 30 x 30 x 12 cm
Sometimes I wonder, how much of that compact assembly contribute to the success of your amp sound-wise. I always like short connections but I have had difficulty to design a "PCB" where the RCA connection is on the PCB (so no cable). I will do it for sure when I have found my final amp

BUT, small amps (boxes) don't look good to me. I prefer the standard width so it will look good if had to be stacked on top of other standard sized components.
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Old 10th July 2012, 12:30 PM   #870
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Sonnya, i am interested how the schematic looks of the amp you brought to Michael.
Have you tried the J-Fet cascodes in the meantime ?
If you wish i can send you J112 and J175, selection is possible.
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