Hotrodding the UCD modules

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#1,141
Re: Re: Re: Re: Re: Snubber circuit for free!

t. said:


I've probably got this totally wrong so please excuse me😀
I can change anything easy so thats no problem, just quickly done the + side first so if its not right I can change it.
Click to expand...


Almost the exact opposite. Ahhh for a picture.

You want to have the cuts such that they force current under the pad. What you have does the opposite.

Another try. Take again, the upper left cap, bottom pad.

Cut a void that is an equalaterial triange in the copper so its apex points to the Cap pad.

Mike

p.s. I tried a scan, but it was to big and I don't have much time now.
 
#1,142
Re: Re: Re: Re: Re: Snubber circuit for free!

Bgt said:

Mike,
the resistors in the shield take the humm(groundloop) out. You may put lower values there also. Remember I have the middle of the 4 caps. to ground. This is also my middle leg of the toroid. I use 1 rectifier bridge for each channel but the ground is the 0V of the PSU where the 0V of the power amps are connected 2.
It all comes down to having no humm, no capacitive influences(wire) and great depth. I have spent weeks on end trying out how to get the soundstage wider and wider(improve crosstalk figures). It sounded flat, still nice but not OK enough. And thats with 1 toroid with 2 windings, 2 rects., 4 caps.


PS tried the resistor on the other end of the input cable but it distroyed my crosstalk.
Made the input cable more sensitive to cap. coupling.
Bert
Click to expand...


So now you are back to single bridge with center tap, and that better? Correct me if I mis-understand. That would indeed be interesting if that was better.

I don't understand the issues, but I'm glad you got it good.
I assume you did as Chris said, and tried no resistor.
Problem might be in your source or preamp. UL and CE are not always in line with optimal I think.

Are you using a earth ground in your amp?

Do you possibly have a picture of how you wired your transformer and caps?

(Please note, I'm not expecting to be any help, just want to understand.)

Regards,

Mike
 
#1,143
Hmmm, I didn't really say to try it with no resistor, obviously you'd be left with a ground loop. I was more less saying to make it work without a resistor, which implies breaking the ground loop elsewhere, or using other means.

Bruno also gave a pretty good response to that resistor awhile ago, and I'd recommend following that as well.

This resistor will be a real soundstage killer, but yeah it will minimize loop hum.
 
#1,144
classd4sure said:
Bruno gave you some good advice on why that resistor is less than optimal and how to do it right. You'd gain tremendously in soundstage by following that advice, and breaking your groundloop elsewhere, such as by floating the supply.

This resistor thing will surely decrease audible hum if you choose to accept a ground loop, but it will reduce the soundstage /depth of field and everything all at the same time.

It's like using a dirty shoelace as a bandaide.

I'd say heed Bruno's advice and try to experiment with breaking the groundloop via other means while keeping the signal path as pure as possible, with the input stage referenced to source ground, or even floating as a last resort.

Mike made that same mistake and noticed vast improvements after changing it. 🙂
Click to expand...


Chris,

I'm glad you brought that up, I think🙄

The stereo amp is better not done that way then my monoblocks done that way (Lots of other possible reasons.), but I didn't try it that was because my brain said there would be a serious loop current caused by each amps relitively noisy ground through my single ended inputs.

I think I'm glad you brought that up but not sure, because its a 40+ screw task that takes me a couple of hours and no good way to test it before its all buttoned up for the most part. 🙁

To help me avoid a 4 hour task:
Do you have your shields tied together at the other end?
I recall you have a transformer based preamp, right?
I could see you getting by not tying them, but are the shields isolated from each other?

Thanks

Mike
 
#1,145
No Mike I have an 1820M audiodock and I've put it through numerous successfull variations of configuration, from single ended to broken shield at either end with supply grounded to fully floating supply and broken shield to lifting the ground at the source and fully connecting the shields at either end.

Next move is to clean up the grounds of pc's smps by removing the Y caps in it.

Anyway the shields are not at all isolated from one another, in fact I make it a point to tie them together.

PS:

"To help me avoid a 4 hour task:"

Why avoid it? Why not start with a better configuation for experimenting with from the beginning? It still takes time but it's the best way to see what's up. Should make yourself a little test rig. I haven't had my modules in a case yet!
 
#1,146
Mike,


See it this way,
1 toroid with center tap
2 rect. + 4caps with center tap
2 plusses and 2 minusses, each amp. gets 1 pair. The ground is connected to the center taps of the caps. and toroid and the 2 power amps. Thats all there is to it. Call it a star ground. This is done all on 1cm(square). So no humm because of long traces/wires. To separate both the inputs ground wire from the amp. power section ground I use the 10 ohms resistors. Otherwise there could be a current flowing through the input ground wires/shields. This would result in exta crosstalk/EMI.

Chris, I know you use it differntly and believe me, I tried it your way also but it just does not work for me. If I take 2 monoblocks...than it works out well. This is not because I dont believe you but it just doesn't give me a wide soundstage. Remember I use 2 amps. in 1 housing with very high opamp. gain. I just could not get it OK with the inputs grounded and a floating psu.
I have no mains ground. You don't need it here if the amps are well isolated from the mains.

PS the NAD C272 power amp. I had also had an isolated mains plug, and this was UK made.
 
#1,147
classd4sure said:

Next move is to clean up the grounds of pc's smps by removing the Y caps in it.

Anyway the shields are not at all isolated from one another, in fact I make it a point to tie them together.

PS:

"To help me avoid a 4 hour task:"

Why avoid it? Why not start with a better configuation for experimenting with from the beginning? It still takes time but it's the best way to see what's up. Should make yourself a little test rig. I haven't had my modules in a case yet!
Click to expand...


Chris,

Cool preamp. So I take it you don't spin discs to listen to music anymore 🙂

This stereo unit was an effort to get a second system up and running with a remote volume control. It sounded better than the monoblocks which are pretty easy to get at.

I really want to get to the dual bridge thing in my monoblocks but am trying to source a transformer that could fit first. If not, then its a hunk of Aluminum and mount it all on that.

This stereo unit is NOT a good plateform to screw around on it turns out. But it does have a decent enough remote volume pot to do what I intended, be a movie amp! It sounded so good compared to the monoblocks... It got the spot for now in my listening room.
What I need to do next is get my monoblock UcD boards back to stock, or at least the stock bypass caps becuase I'm starting to question my phonographic memory on the topic.

Best Regards,

Mike

p.s. You should build up a nice linear PC supply 🙂
Or maybe, look into that technical balanced thing Mauricio keeps bringing up. Taking out Y caps on a pc supply would scare me. I hope your not a pioneer in this.
 
#1,148
Bgt said:
Mike,


See it this way,
1 toroid with center tap
2 rect. + 4caps with center tap
2 plusses and 2 minusses, each amp. gets 1 pair. The ground is connected to the center taps of the caps. and toroid and the 2 power amps. Thats all there is to it. Call it a star ground. This is done all on 1cm(square). So no humm because of long traces/wires. To separate both the inputs ground wire from the amp. power section ground I use the 10 ohms resistors. Otherwise there could be a current flowing through the input ground wires/shields. This would result in exta crosstalk/EMI.

Chris, I know you use it differntly and believe me, I tried it your way also but it just does not work for me. If I take 2 monoblocks...than it works out well. This is not because I dont believe you but it just doesn't give me a wide soundstage. Remember I use 2 amps. in 1 housing with very high opamp. gain. I just could not get it OK with the inputs grounded and a floating psu.
I have no mains ground. You don't need it here if the amps are well isolated from the mains.

PS the NAD C272 power amp. I had also had an isolated mains plug, and this was UK made.
Click to expand...


Thanks for clarification.

Power supplies, grounding and shielding. Always wierd I guess.

I've pondered if a bridge per channel is a good thing from on transformer. When one side shuts off and the diode snaps, the other channel is still conducting.
Just a wild theory. Not hard to try!

Perhaps running these amps at high gain is a good way to optimize!

Mike
 
#1,149
Have you also tried floating your supplies from the chassis?

I actually do use a mains ground on the chassis, but the supply floats from it, the signals are grounded to chassis with the source via the shields, which are still about 12' long no less. Stands to reason it could improve with trimming.

Mike, it's all about Pioneering. Most supplies don't have them at all anyway, or they didn't used to at least. I already floated the earth from it, no sense having them there at all now.

Personally I'd working on identifying why the movie amp has a better sound than the monoblocks, and I wouldn't be looking at things like damping at all. No doubt there's very obvious differences to note long before anything so obscure.

That could possibly cut down on the experimental process.

Oh, this balanced power stuff is .. Hm... well. it's AC right??
 
#1,150
Mike,

Grounding is such a precise job to do. And I always do it first like the original id of the amp. designer. But than I compare it to my other amp. (mono blocks)and hear the flatness, dull soundstage, voice in the box instead of out...well thats the time to start experimenting.
And my grounding scheme which I use now turns out to be the solution for me and thats it. Just wanted to share it,
there are may ways of doing things...tough luck.
It also turned out that all the cap. mods hardly did anything to my sound/soundstage. I have done a lot of A/B switching between amps and find the differences insignificant. Only this ground thing was an eye opener.
Off to bed.
 
#1,151
classd4sure said:
No Mike I have an 1820M audiodock and I've put it through numerous successfull variations of configuration, from single ended to broken shield at either end with supply grounded to fully floating supply and broken shield to lifting the ground at the source and fully connecting the shields at either end.
Click to expand...

Totally OT: You can power the 1820m audiodock from a separate linear supply as far as I know.

There are also some interesting mods to do to the audiodock 🙂.
 
#1,152
Hi All,

Well, I've read this thread now, and I'll tell you the truth, this is mighty discouraging. I was thinking of building one of Kevin Haskin's UCD putting it loosely, kits. It is sure disheartens me to hear that the UCD as stock doesn't have dynamics using an IC frontene, compared to that of a standard analog amp. To get any dynamics, might as well stick with the 2134 chip, and just using the trim pot on the newer board, take out the DC offset and short out those DC imput caps.

Also, seems to me, if going the totally mono route, the Rcore transformer would be cheaper, allbeit bigger, and would work just as well.

Ray
 
#1,153
ray bronk said:
Hi All,

Well, I've read this thread now, and I'll tell you the truth, this is mighty discouraging. I was thinking of building one of Kevin Haskin's UCD putting it loosely, kits. It is sure disheartens me to hear that the UCD as stock doesn't have dynamics using an IC frontene, compared to that of a standard analog amp. To get any dynamics, might as well stick with the 2134 chip, and just using the trim pot on the newer board, take out the DC offset and short out those DC imput caps.

Also, seems to me, if going the totally mono route, the Rcore transformer would be cheaper, allbeit bigger, and would work just as well.

Ray
Click to expand...


Ray,

It is quite good, just not the very best I've heard. For me, only bested by a hand built class A/B. It smokes my Yamaha BX-1 class A monoblocks, McIntosh MC75's, and MC240's. Its real claim to fame in my book is its the absolute best stage I've ever heard from any amp, being very wide, high, deep and solid.
I suspect some of the lack of dynamics might be the surface mount resistors, but haven't gotten to playing with that yet, which is a shame, since its likely one of the easier changes to try.

Anyone have experience with good sounding surface mount resistors?

Mike
 
#1,155
ray bronk said:
Hi All,

Well, I've read this thread now, and I'll tell you the truth, this is mighty discouraging. I was thinking of building one of Kevin Haskin's UCD putting it loosely, kits. It is sure disheartens me to hear that the UCD as stock doesn't have dynamics using an IC frontene, compared to that of a standard analog amp. To get any dynamics, might as well stick with the 2134 chip, and just using the trim pot on the newer board, take out the DC offset and short out those DC imput caps.

Also, seems to me, if going the totally mono route, the Rcore transformer would be cheaper, allbeit bigger, and would work just as well.

Ray
Click to expand...

there are many on this forum that are grossly misrepresenting the sound quality of the units in their stock form. i have personally built and tested these units (specifically the UCD400AD) in a manner which would annoy just about everyone in this thread, only to have it sound better than most amps ive heard.

this thread's primary interest is to make the UCD's sound as good as they possibly can. this is not to be mistaken with trying to make the UCD's sound reasonably good, as they already do in stock form.

the best advice that can be given is to buy some, throw together a working amplifier in its most amateur fashion, and listen to it. if you like how it sounds in general, you should be impressed with any and all upgrades that can be made.

i think they UCD's in stock form can outdo most amplifiers in the mid-fi to lower-end hi-fi range given a fair and unbaised comparison. this has been the case in my system and the numerous people that have done that comparison.
 
#1,156
Re: Re: Re: Re: Re: Re: Snubber circuit for free!

Portlandmike said:



Almost the exact opposite. Ahhh for a picture.

You want to have the cuts such that they force current under the pad. What you have does the opposite.

Another try. Take again, the upper left cap, bottom pad.

Cut a void that is an equalaterial triange in the copper so its apex points to the Cap pad.

Mike

p.s. I tried a scan, but it was to big and I don't have much time now.
Click to expand...

How about this, I'll get there in the end😀
 

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#1,157
A litttle idea to try

Ifd I got it right, a friend of mine use to take a small .22 mf cap and put it across a chip, 1 leg on the imput and the other on the output. It did seem to give more dynamics. worth a shot anyhow.

I had read somewhere I think it was on the audiocircle someone had used an Ad825 chip. This was in a preamp I think. Any takers on that one?

Ray

Ray
 
#1,159
Re: Re: Re: Re: Re: Re: Re: Snubber circuit for free!

t. said:
How about this, I'll get there in the end😀
Click to expand...

Imagine you're laying out a really thick trace (say twice as thick as the pad diameter for the cap) and the trace width necks down to the diameter of the cap's pad as it approaches the pad, then it expands back to it's original width as it leaves the cap's pad. I think that's what Mike was trying to explain to you.
 
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