Hotrodding the UCD modules

A new thread for general discussion of upgrades made to the UCD modules.
Safety issues must be dealt with like proper fuse protection, covers for exposed mains voltages, storage caps drained before service done, etc.
Any replacement parts should first be given the "Lars" magnet test.
Quality solder should be used as well as a fine tip low wattage iron.

Please add to required proceedures list.
Let’s try to keep all the mods in this thread so they can be found!!
Roger
 
ok then, what are the "hotrodding" options for the ucd modules?
I think I'll constrain myself to only replacing parts on the upper side of the pcb; my smd soldering skills aren;t really that good (and my hands tend to shake ;( )

What is there to modify?
- input filter caps
- output filter cap
- on-board psu caps
- more?

Hintd? Tips? Tricks?

I've only removed the input caps, which has lead to a change, definitely for the better, in the sound of the modules. They sound clearer, like a curtain has been removed from the sound. Less warm in the mid-bass region but with more definition in the low-low regions. At first, I've bypassed them with a solid pieces of copper wire of ~5mm length, and after having tested my pre and some other sources I;ve removed the caps completely. I couldn;t hear the difference between removing and merely bypassing the caps so if you want to keep the modules in a sort-of-original state, there's (afaik) no reason to remove them completely.
 
cap question

I think all the 400 modules have the caps right at the input connector. So if you remove the originals and connect new ones from the input jacks to the amp connector the circuit remains the same. Kind of ironic, using caps that are larger than most of the modules parts put together. This is what it takes for good sound.
Later I will be experimenting with new circuits for the opamp regulators as there is room for improvement there
Roger
 
Dont know if this is correct thread for power supply caps but..

Hypex is using BHC Slit Foils capacitors in their HG power supply.
Bruno has said that BlagGates are very good but maybe too expensive to many of us.

I am currently using 4x 10000uF Rifa PEH200 (4 channel dual mono UCD180). Some has said that Rifa dont sound too good but i cannot yet say because i have not tried anything else. Anyway, i feel that sound of UCD is good even with this PS.

Maybe i will try BHC Aerovox T-Power 4 pole caps. Anybody have experience from these with UCD?

Some other good PS caps?
 
4 pole caps

rha61 said:


rha61,
These caps are new to me. I looked through all their tech stuff and am very impressed. I really like the idea of separate input and output terminals to isolate charging current induced ripple and noise. In the equivalent circuit shown for conventional caps, the nasty high freq. trash is hardly attenuated at all. In the Jensen the equivalent series impedance works in your favor to reduce HF noise transfer.
A couple of things that bother me;
In their description they talk of several ohms of resistance between the input and output terminals. Seems using these terminals separately would severely limit ripple current capability. This resistance will also effect regulation and cause some rail voltage drop. They talk of using a series inductor between input and output to correct this so you still get the good HF isolation. However this destroys the low freq ripple isolation and makes it the same as a conventional cap with bypass as below. They don’t recommend this hookup for audio. Of course if you are using a SMPS, using inductors to couple the input to output would still give you the really nice HF attenuation with very little low freq ripple to worry about.
Doing a poor mans version would be to bypass conventional storage caps with large value film caps first then doing 1/10 value and 1/10 value again. (10uf, 1uf, .1uf etc) This will meet or exceed the specs of the Jensen but won’t give you the ripple current isolation.
I would like to try them, too bad they are so expensive. Cost nearly as much as the amp modules! Sure would like someone to try them and report it here.
Roger
 
OK in my quest for the best:

A few questions:

* The input caps, that's C23 and C24 I suppose? I'm a total newbie with soldering iron... if these caps are bled dry, is it possible to just drop a little blob of solder on both poles?

* Using new caps, how to put them on the signal path? Same way like the caps in the power supply? anything more that should be added?

* I'm interested in the HQ power supply by Hypex. Is there a PDF or something, I want to see what all the connections are for. Anyone here that is already running this power supply? I just want to see if it is possible to use 2 smaller toroids connected to one PS, and want to know how the DC protection works.

* Right now i'm running quite large 22.000uf BC 154 cans - will the slitfoils be better?

* At what VA rating is a soft start absolutely needed? (230V mains) I'm considering LC Audio

Thanks
 
in general, or so i'm told, softstarters should be used for toroids from ~225VA and upwards. For toroids >225VA, inrush current is too high for most fuses and trips them/burns them out.

I can't say whether the 22000 BC;s are better or not, i've only tried the slitfoils with my ucd400's. I can say they're better than the psu i'm using for my ucd180's (3ch surround) consisting of a couple of panasonic FC's in parallel. I swapped fc's for the slit foils and the results were clear. Way better...

on the ucd180 (rev 1.00) the input caps are c7 and c8, on the ucd400 thay are indeed c23 and c24

When replacing the input caps, you can use high quality non-polar (bipolar) electrolytics like black gate N, NX or, better still, use high quality film caps. These tend to be much larger than electrolytics but they sound better. If you want to use these, remove the old input caps, bridge them with a small piece of wire and put the input caps between the rca/xlr sockets and the modules. As these are non-polar, direction (??) is not important.
 
If i understand correct, input caps are in op.amp_output_at UCD180. Is it really so that these can be shorted and moved before input of UCD (between input RCA and input amplifier)?

Other (stupid) question.
When unbalanced (RCA) input is used, is -input capacitor needed at all, because input will be connected to ground anyway. Other words, do we still have dc-protection if only +input cap is used and -input cap is shorted?
 
Pasi P said:
If i understand correct, input caps are in op.amp_output_at UCD180. Is it really so that these can be shorted and moved before input of UCD (between input RCA and input amplifier)?

Other (stupid) question.
When unbalanced (RCA) input is used, is -input capacitor needed at all, because input will be connected to ground anyway. Other words, do we still have dc-protection if only +input cap is used and -input cap is shorted?

Haven’t seen that many stupid questions and these are not, but have seen a lot of stupid answers!
Bruno stated there was nothing to be gained with a - input cap if the input jacks were RCA's. If you have balanced input connectors and are using balanced to single conversion cables to the source it is an advantage to use 2 caps. This equalizes the input circuits for greater common mode rejection and less offset.
You may be able to jumper out the original 22uf caps in the 180 but watch the output DC. I would say if it is over .1 volt you will have to do something about it, like replace the opamp with one that has lower offset and bias current. After you jumper them out you can use rather modest size coupling caps between the modules input and the input jack. Most have settled on 2.2uf @ 200V for the best all around performance and safety.
If using input caps from the RCA’s put a 100k ohm metal film resistor across the RCA jack to insure any stored charge is dissipated.

matjans said:
Q: How do i see which side of the film cap is the outside foil lead? Is there a sign for this?

I am only sure of the Auricap. Its outside foil is marked by a black lead. Some manufactures post this info on there websites. On stacked film types it generally doesn’t matter as the exposed surface is quite small for the value. I would use the stacked film type for coupling only if there were no options other than electrolytic.
Roger
 
matjans said:
in general, or so i'm told, softstarters should be used for toroids from ~225VA and upwards. For toroids >225VA, inrush current is too high for most fuses and trips them/burns them out.
The main reason for a softstart is to avoid blowing fuses in the wall. The problem starts I think from 500 VA and 6 A fast in the wall. When I lived in an apartment with only 6 A I had those problems.

My amp with 600 VA + 44000 uF did blow a 6 A slow once in a while if I had more things connected to the same fuse.

It's OK though to use a softstart anytime in order to save the power switch and for bigger PS' also the main fuse.