UcD400 Q & A

[deandob]

Well Chris, you had better open up your 1820M and check the DC coupling arrangements first

The UCD has a gain of 20 (26db) so will the difference between 1.5mV and 3mV make a difference? The BR version costs $27 each from digikey!

Regards,
Dean

[deandob]

All,

I've been researching the best power cap for the UCD400. I'll be using a 300VA shielded toroid per monoblock and want to use 2 x 10,000uF per rail (4 caps). As expected, opinions vary what is the best cap to use but the BHC series, especially the slit foil seems to be the favourite for the UCD.

I'd like to try the BHC ALC10S1080 slit foil (10,000 63v) but can't find any source except Schuro in Germany but it seems this vendor is not interested in selling outside of the Euro zone.

Does anyone know where I could find this cap that would ship overseas? Or maybe what equivalent cap could be used?

Regards,
Dean

[BOB LEWIS]

Deandob,
You can purchase the T-Network slit-foil caps direct from DNM,the inventors,for £22 each + £15 overseas carriage.
See their website for more details.

Bob Lewis

[deandob]

Thanks Bob. I need 4 per monoblock which is 8 x 22 pounds + 15 pounds = a big investment. I was hoping to find a source for the cheaper slit foils (without the T).

Regards,
Dean

[t.]

Ok I'm slowly getting all the additional parts needed before I order the UCD400's

2700vA toroidal with 2 x 40-0-40 secondary's
A softstart for the above
Swiches,fuses and cable
A pair of AvondaleCap-6 modules using MBR20200 Schottkies
A mixture of dual smd op-amps to try out
A pair of diy regulator boards posted earlier by Roger for the op-amps, Thanks Roger
Diy 22k passive pre

I still need the 2.2uf Auricaps for the coupling.
If all the above are ok is there anything else anybody recommends I need or should try?

Cheers!

[sx881663]

T,
Don't forget you will need a nice, very sturdy chassis to hold that heavy transformer and stuff. The mounting hardware must be equally sturdy. Also the amount of wire you need is so small I would recommend using some of the high quality specialty stuff available from Michael Percy and others. I personally would avoid the silver and silver plated stuff as it does have a sonic signature. High purity (Like 6-9’s) copper with expanded polyethylene insulation seems to be the best all around general purpose wire. Michael Percy also would be a good source for the I/O connectors. I like the new low mass WBT chassis RCA’s.
http://www.percyaudio.com

Consider the Neutrik Powercon jack/plug as your choice for the AC power connections, far superior to the standard IEC. Nice thing is they mount in a round hole and the plug locks in place. Their only drawback is the ugly light blue color. You can solder wires to them as the plastic is a very high temperature type. These are available from Mouser. Mouser also is a good source for all the little stuff like crimp connectors, nuts, screws and stand off’s.
http://www.mouser.com

What opamps you are trying? Please give us a report. Have you thought about a supplemental supply to power them? Using a small dual output SMPS would be nice in that you could easily adjust the voltage to suit the individual opamp requirements. Small, light, cheap and takes up little room but can perform with the best of them. Do use appropriate buffer caps to reduce switching residual and to lower source impedance. I would recommend at least 1000 uf @ 25V low ESR types like Panasonic HF’s.

Almost forgot, Auricaps can be ordered from several sources like Parts Connection or direct from Audience.
http://www.audience-av.com
http://www.partsconnexion.com/catalo...itorsFilm.html
Roger

[t.]

Thanks again Roger

I'm first going to buy the UCD400 supplied with the standard op-amps
I'm then going to try AD8620, OPA2132,pairs of OPA627,AD826,AD8065 etc which I already have spare
To power them up I'll build your recommended regulator, if theres room inside the case I'll use a separate lower voltage transformer and Schottky diodes etc for the supply, I guess a low VA rated transformer would be ok for the op-amps reg supply.

A few friends who own some very good sounding tube gear and solid state amps etc are already interested in listening to this amp so I need to squeeze as much performance as possible, these guys are not easily impressed

[t.]

Oh I forgot to mention that I already have a pair of nice little SMPS which are used to power the little Amp3, these units have +/-12v as standard

[sx881663]

Originally posted by t.
Oh I forgot to mention that I already have a pair of nice little SMPS which are used to power the little Amp3, these units have +/-12v as standard

T,
Why not use one of them? A lot less trouble than building something that probably won't work as well anyway. I find using SMPS for front end applications to be very beneficial as they have extremely low line noise. Lower noise always helps! Regulation usually is not much of an issue however source impedance is and can be helped with buffer caps.
I would bet they can be adjusted up to at least +/-15V with no problem.

If you do decide to go the analog route try these transformers. TE62062 should be fine.
http://dkc3.digikey.com/PDF/T053/1525.pdf
Roger

[t.]

Great stuff thank you
I'd like to try and find a pair of even smaller SMPS if I was to use SMPS, the transformer I have for the main amp is huge

Do the UCD's work and sound good at lower volumes too? A few friends have sensitive speakers which only need a small amount of watts so if they want to compare something like a 12watt tube amp against the UCD400 it would need to be good at similar volumes, I usually listen to low volumes at home, maybe the 400 would be a bit overkill for my needs but its nice to have that power available just incase