UCD180AD missing transistor?????

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#21
Chris,

Let us know what your findings are. I'm only half aware of what this current loading does, and I have no idea what the impact on the sound would be.

"Hidden Audiophile" option does sound good though. But I'd only consider it if it is really an improvement, not a "coloration" of the true sound.

For the moment, i'm still enjoying the standard AD modules in all their glory 😀
 
#22
Yves Smolders said:
Chris,

Let us know what your findings are. I'm only half aware of what this current loading does, and I have no idea what the impact on the sound would be.

"Hidden Audiophile" option does sound good though. But I'd only consider it if it is really an improvement, not a "coloration" of the true sound.

For the moment, i'm still enjoying the standard AD modules in all their glory 😀
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Hi Yves, will do.

I would expect better microdetail and therefore possibly an increased soundstage, even more "real".

"Hidden Audiophile" option sounds alot different to me..

I wouldn't expect any sort of coloration or "effect" per se.

It's going to be a little while before I can let you know though, but it's one of the oldest audiophile "tweaks" known, if that encourages anyone to try it.

Cheers,
Chris
 
#23
Guys,

The 'missing transistor', will only work with the AD8620 op amp. Because the PSRR is not the same on both rail voltages. The 'missing transistor' improves the PSRR on the rail voltage what is worse.....

So, if you replace the AD8620 with an other op amp whereby the worse PSRR is not at the same voltage (+12V or -12V) the circuit will not work!

Jan-Peter
 
#25
Dear Dean:
I have a couple of super regulator boards that I want to try for powering the AD8620.
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I say, DO IT man! 😀
...and then, tell us. I bet we will be shocked.
I'm out of SR's :bawling:

(Andy, are you there? 🙂 )

Increased operating temperature of the amp is the only downside and I can't see that being a very big deal.
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Why? Heat is good for sound! :clown: 😀

Cheers.
Mauricio
 
#26
I've been a bit lazy and not spent time on my UCD amp, its lying beside my PC with toroids, modules & switching relays waiting for an idle day that never comes to assemble it (finishing my new home theater is the priority).

The last part I am waiting on is some slit foil or 4 pole PS caps but I can't locate any at a decent price.

I have the superreg parts but I'm thinking with the St411 tweak the superreg wont make that much difference to the UCD modules. I have extra superreg boards to go into a NONOS DAC that is also waiting to be assembled!

However I am interested in the reviews of cap swapping, I also have FC caps ready to be swapped in but they are getting mixed reviews.

Regards,
Dean.
 
#27
SEIJI said:
Hi All,

Some of my UCD180AD that I get from local Hypex dealer in Singapore has got missing T22 and T21 smd transistor and some of the modules were intact, all of the module were V4 dated 11/04/2005.

I wonder is that a manufacturing fault, or Hypex removed the T22 and T21 for goods.........

I had about another 20 modules yet to open for inspection....

any comment???
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Seiji - I must say you have a keen pair of eyes! I'm located in Singapore too - had built a pair of UcD 180 AD based micro monoblocks last year. The Hypex modules rock!!

The monoblocks have permanently replaced a well known Kiwi central heating system (which also functioned as a Class A amp) in my main Hi-Res+CDDA based setup 😀 .

I'm currently working on a pair of super souped up UcD 400 monoblocks project now. I would be happy to exchange construction notes with you over a beer or two in my listening room.

cheers!
 
#29
Hans L said:
Chris,

did you get around to trying this tweak? Do I understand correctly that it involes only removing the two transistors... as simple as that?

Cheers,
Hans.
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Hi,

I have done this and it envolves "adding" current regulator diodes.... sot-23 SST511 or equivalent.

If you dont' see the empty solder pads you're free to try one of the other "biasing tweak" options, could be as simple as a resistor, as complex as a current mirror.

Soundwise it's pretty much what I expected, deeper soundstage, cleans up the finer harmonics, making it a little bit more musical, and alot more real.

It's not that obvious an improvement, but well worth it.

Hope that helps.
Chris
 
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