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Old 23rd July 2005, 03:58 AM   #1
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Default Bypass cap on UcD 180?

Hello

I am curious if using bypass teflon caps on my UcD 180 would make any difference?

I have 2 --12 mf coupling caps per side right now.So that is 4 caps altogether 22mf per side.

I was thinking of using some .01 or .1 teflon bypass caps.I wonder if this will change the sound much at all.



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Old 23rd July 2005, 02:19 PM   #2
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No one here knws if a teflon bypass cap would make much of a difference?I guess i can try another forum



regards
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Old 24th July 2005, 12:48 AM   #3
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by RogerWilco
No one here knws if a teflon bypass cap would make much of a difference?I guess i can try another forum



regards

I should have posted my reply here. You dropped me a private mail but my reply bounced back, here it is:



Hi RogerWilco,

> I have a UcD 180 and you had replied to my post in the forums on my unit
> with cables.It seems like you know what you are taking about so i have a
> question.

Thanks for your trust in my opinion. I'm an electrical engineer but not in
the audio field. Audio is a hobby and I just recently started building amps
and power supplies again. So I don't have much experience with tweaking
components. I'm looking at many things just as an engineer trying to judge
whether some changes could make a difference yes or no from an engineering
point of view, these opinions are not necessarely backe up by experience. Of
course I experiment but my free time is limited so I limit my choices. For
the input caps on my UcDs I use BG HQ NX caps, the reason is that in my case
I have the earliest UcD180 version that has the NE5532 opamp that needs the
caps in between opamp and modulator.

> My ucd 180 has --2 ---12 mf caps per channel. I was thinking on adding
> .10 teflon or mundorf silver in oil bypass caps
>
> Sense i did not biuld this and know very little on the design i was
> wondering if using 1-- .10mf bypass cap on each of the 4-- 12mf sonicaps
> would make a difference in sound.Or if this is an overkill

I think it is overkill. Likely you can make the main caps smaller which will
probably have more sonic benefit.. I do not know which UcD version you have.
There is a version where the coupling caps are before the opamps and a
version where they are after the opamps in between the opamps and UcD
modulator. In case the caps are placed before the opamp, you can make them
much smaller (so they can be higher quality). The input resistance of the
input stage (opamps) is 100k (except for some very early version that were
lower), so even a cap of 1uF would work very well, giving a high-pass filter
at 1.6Hz so leaving audio frequencies completely untouched.

Best regards

Gertjan
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Old 24th July 2005, 01:21 AM   #4
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Hello and thx for the reply.

I really don't know---this is the rev 2.0 serial 0540 and 0553

Having a hard time posting pictures here---this is the best i can do
Attached Images
File Type: jpg dsc03926a.jpg (18.8 KB, 274 views)
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Old 24th July 2005, 05:31 AM   #5
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by RogerWilco
Hello and thx for the reply.

I really don't know---this is the rev 2.0 serial 0540 and 0553

Having a hard time posting pictures here---this is the best i can do

Those caps are huge. I would keep them smaller and mount them not so close to the UcD module with those long unshielded wires. These unshielded wires may pick up noise from the UcD modules themselves or from another noise source.

Best regards

Gertjan
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Old 24th July 2005, 06:33 PM   #6
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I used an old ad of mine on audiogon to put better pictures of the amp on.


http://cgi.audiogon.com/cgi-bin/cl.p...127282995&item
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Old 24th July 2005, 07:05 PM   #7
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Maybe you should tell us why you think that Teflon bypass caps is a good idea.

Jocko
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Old 24th July 2005, 08:14 PM   #8
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Quote:
Originally posted by Jocko Homo
Maybe you should tell us why you think that Teflon bypass caps is a good idea.

Jocko

My sound is very good,but my midrange is a little laid back.I was thinking that using some teflon bypass caps there may help in that area.

But i don't know if i am to use 1 per side or 1 per cap.I am also considering the mundorf silver in oil .1 cap as a bypass.


Mainly just something to try--i want to make sure it will not mess with the circuit at all.

regards
jeff
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Old 25th July 2005, 10:06 AM   #9
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From what I have read in these forum and looking at your pictures, what you need to do is the following:

1. Remove the Sonicaps caps you have in place now.

2. Insert a wire strap across the pads where you removed the two 22uf 63v electrolytic caps.

3. If using single ended RCA connections, insert one 1.0uf 200v cap in line with the "+" pin. Mount the cap at the RCA jack.

4. If using balanced connections, insert two 1.0uf 200v caps inline with both the "+" & "-" pins. Mount these caps at the jack.

No bypass caps should be used on the incoming lines to eliminate smearing.
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Old 25th July 2005, 02:56 PM   #10
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Quote:
Originally posted by Stevenacnj
From what I have read in these forum and looking at your pictures, what you need to do is the following:

1. Remove the Sonicaps caps you have in place now.

2. Insert a wire strap across the pads where you removed the two 22uf 63v electrolytic caps.

3. If using single ended RCA connections, insert one 1.0uf 200v cap in line with the "+" pin. Mount the cap at the RCA jack.

4. If using balanced connections, insert two 1.0uf 200v caps inline with both the "+" & "-" pins. Mount these caps at the jack.

No bypass caps should be used on the incoming lines to eliminate smearing.

Hello and thx for your reply


What would be the drawback of this method?I do believe that when this amp was built the guy was going by the reference design.I only use single end cables.
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