UCD180 questions

[matjans]

again!

after "some" initial trouble (eg replacing the ne5532 opamps) it's working again. When replacing one opamp, something went wrong (no clue as to what) and i completely blew up one channel. The second channel works perfectly, btw.

Got another module from hypex and it's working again. when i was there they tested the ad8620 i used. on the scope it gave some very nasty noise (ab switching? maybe it got too hot during soldering). Anyone else tried a 8620 yet?

ps die lemsteraak wordt mooi!

[dmfraser]

I connect the + input to pin 3 of the XLR, the - input to pin 2 and the input ground to pin 1.

Chassis ground is connected wherever gives the least noise. This may be XLR pin 1 as well, to the power supply common, to the Ground on the board or to the output ground. Which one works best depends on the quality of the rest of your wiring and physical layout.

If using an unbalanced input, isolate your jack from chassis ground. Connect the + in to the hot and both the - input and the input ground to the shell of the input connector. Connect chassis ground as above.

I highly recommended isolated input jacks as I find the shell of the input jack is seldom the optimum place to make your chassis ground connection. I know it seems silly to isolate the input jack when an ohmmeter will show zero ohms between it and the chassis anyway but isolating the input jacks and then finding the quietest place to make chassis ground is one of the ways to get the best possible signal to noise ratio. I always start my designs with the circuitry totally isolated from the case and determine the best place to ground experimentally in keeping with the needs for agency approval. I never actually run any signal through chassis ground.

[jam]

Dan,

Thanks for the comprehensive comparison. I guess we will have to wait for the sonic comparison after you have assembled the amp.

Regards,
Jam

[indoubt]

Although it will not reach it full potential in power terms would an UCD 180 module suffice in sound quality with a -35/+35 Volt feed.

I'm considering testing the modules and have a casing and psu available. As I don't need 100watts to establish whether the module sounds good I would like to know wheter there are sonic differences when using 35 volt supply(tranny is 25-0-25V)

I also have zap modules (not finalised yet) and they seem to perform best with oversized VA ratings. I noticed that some are using modest Va ratings for the psu. Would a single 300Va be sufficient for 2channel (8ohm load loudspeakers) or are there large sonic differences when the psu is oversized (600Va+)

If necessary I can go up to 540.000Uf on caps (8 pcs 68.000uF available, from an unfinished aleph project) although this looks kind of overdone.

( I know, lots of projects at the same time and only less than half really finished, but it is so much fun )

[matjans]

Originally posted by indoubt
[SNIP] ... I would like to know wheter there are sonic differences when using 35 volt supply(tranny is 25-0-25V) [/B]

i tried a toroid with 22V (~31vdc) secondaries and 30V (~42vdc) secondaries. With 30v secondaries it sounded much better.

when i used the lower voltage supply, the amp sounded lazy, not willing to produce music. Like (i've said this before somewhere in this thread) the musicians were playing just another set, they weren't enjoying themselves. Technically ok, but boring. With the higher voltage supply it sounded more 'involved'.

[rha61]

Originally posted by matjans
again!

after "some" initial trouble (eg replacing the ne5532 opamps) it's working again. When replacing one opamp, something went wrong (no clue as to what) and i completely blew up one channel. The second channel works perfectly, btw.

Got another module from hypex and it's working again. when i was there they tested the ad8620 i used. on the scope it gave some very nasty noise (ab switching? maybe it got too hot during soldering). Anyone else tried a 8620 yet?

ps die lemsteraak wordt mooi!

Hi Matjans
How about the sound with the 8620 ? Have you shorted the output caps ?
I've ordered 2 AD8620 but i'm very pleased with the 5532+ BG-N output caps presentation :
the UCD180 with this combination ( 500va r-core transformer , Elna Audio 12.000/63v caps ) outperforms my Accuphase307 (which had outperformed Krell kav300 , Chord spm1000 or excellent Denon Pma-s1 ...) on my system (DIY speakers : Esotar tweeter , Davis midrange Cabasse woofer )

Alain

[Jan-Peter]

Alain,

great you like the sound of the UcD...

Please change also the voltage regulators when you go for an AD8620!!! Because the AD8620 has a maximum voltage rating of 13V, if you have the possability I would recommend the ON semiconductors voltage regulator and in a 12V version.

Regards,

Jan-Peter

www.hypex.nl

[pburke]

Originally posted by dmfraser
<snip>
If using an unbalanced input, isolate your jack from chassis ground. Connect the + in to the hot and both the - input and the input ground to the shell of the input connector. Connect chassis ground as above.

I highly recommended isolated input jacks... <snip>

thanks, Dan, that's what i needed to read. I'll be able to go from there. My RCA's on the Bottlehead Foreplay preamp are isolated from the chassis and I would do the same on the power amp. My wires aren't shielded, but they work just great in my current setup, so all I needed to know is how to wire up the modules to make them work as a replacement for my current amps. I can always mess with the cables and connections afterwards.

Here's a new question - important to my speakers which have rather large drivers (planars): What's the damping factor (http://www.classic-audio.com/marantz...ingfactor.html) of the UCD modules? I assume it is pretty good, but a ballpark value would help me compare them with my current amps (rated ">800").

Peter

[Jan-Peter]

Peter,

The UcD180 has an output impedance of <0.010. So you will have a dampingsfactor of 800.

Regards,

Jan-Peter

www.hypex.nl

[maxlorenz]

Hi everybody:
I'm a beginer to DIY. I dream about a "all DIY" system (well, perhaps not with a DIY source).
I recently finished a transformer based passive volume control (AKA TVC) wich is wonderful, at least to me.

I have a couple of questions. Sorry if there are already answered. I fatigued around page #14

1) Are balanced and unbalanced input impedances different?

2) Are there versions with higher input impedance to mate better with passive pre's? Or, how can I increase input impedance, without compromising sound?

3) Will balanced input sound better than unbal?

4) Is it wise to separate the PSU box from the power amp box?

5) Is it comparable if I use one 220VAc to 2x32VAC transformer with separate rectifiers/caps instead of two completely separated PSU's, in terms of noise and channel crosstalk, etc..?

Ups, sorry


Thanks in advance.
Mauricio

:angel