Bypass cap on UcD 180?

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RogerWilco

RogerWilco

Member
Joined 2004
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.



regards
 
G

ghemink

Member
Joined 2004
RogerWilco said:
No one here knws if a teflon bypass cap would make much of a difference?I guess i can try another forum



regards
Click to expand...


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
 
RogerWilco

RogerWilco

Member
Joined 2004
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
 

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G

ghemink

Member
Joined 2004
RogerWilco said:
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
Click to expand...


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
 
RogerWilco

RogerWilco

Member
Joined 2004
Jocko Homo said:
Maybe you should tell us why you think that Teflon bypass caps is a good idea.

Jocko
Click to expand...


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
 
S

Stevenacnj

Member
Joined 2003
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.
 
RogerWilco

RogerWilco

Member
Joined 2004
Stevenacnj said:
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.
Click to expand...


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.
 
S

Stevenacnj

Member
Joined 2003
If you read through the UCD Hotrodding thread, you will find the info you are looking for, with suggestions, as I described above, by Bruno P. the UCD designer.

The only possible issue may be with the revision # of your module. I have a UCD 180AD Rev 2.0 and the proceedure to use is as I described it above.
 
RogerWilco

RogerWilco

Member
Joined 2004
At first i was thinking of using a top quality bypass cap with the caps already in the amp.I have used bypass caps in the pass with great results.That was my thinking here.

In response to my questions here i have learned a possible different way to Approach this.


I do have to find out if the modules i have---rev 2.0 0540 and 0553 can work with taking the caps out.I do not want to create a possible safty issue in the future just for better sound.

I do not build amps--i do not know how--It is not my Expertize ,so i am a little slow to understand things here.

My preamp is a bruce moore COMPANION III .Is a good mix with this amp--a little flavour of tubes.

The sound is very close to my taste,but i will agree that 24uf caps is alot in the signal.


Using this method is intriguing






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

2. Insert a wire strap across the pads where you removed the two 22uf 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.


I just need to know if my modules can handle this?





regards
 
S

Stevenacnj

Member
Joined 2003
RogerWilco said:
It looks like i do understand so far.But why If using single ended RCA connections, insert one 1.0uf 200v cap in line with the "+" pin. Mount the cap at the RCA jack?


I also need to make sure my preamp has coupling caps.
Click to expand...

If you read the UCD Hotrodding thread, you will find all your answers.

I am positive your amps will sound much better once you correct this problem. Please let us know.
 
RogerWilco

RogerWilco

Member
Joined 2004
Stevenacnj said:


If you read the UCD Hotrodding thread, you will find all your answers.

I am positive your amps will sound much better once you correct this problem. Please let us know.
Click to expand...


I must have missed it in the hotrod forum or at the time did not understand what i had read.

It looks like it would be fine just too use one 1.0uf 200v cap per - then one for +

It looks like trading one coupling cap for another right?I could order 2 1.0 uf mundorf silver in oil caps for this application if i am understanding this correctly .I will start posting in the hotrod forum
 
G

ghemink

Member
Joined 2004
RogerWilco said:
It looks like i do understand so far.But why If using single ended RCA connections, insert one 1.0uf 200v cap in line with the "+" pin. Mount the cap at the RCA jack?


I also need to make sure my preamp has coupling caps.
Click to expand...


If you have coupling caps on the UcD, then you don`t need them in the pre-amp. No need to do it double.

Best regards

Gertjan
 
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