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Old 12th April 2008, 07:03 PM   #1
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Default Hypex UcD questions.

I am looking to build an Aikido preamp with a four channel Hypex UcD180 amp to bi-amp my speakers. The Aikido already has high gain so I am afraid the gain will be too much.

First off, if gain is not needed and the buffer stage in the UcD module is there to lower the input impedance below the required 1400 ohms needed by the oscillator, would it be needed at all if the preamps output is 300ohms?

Second, what do the Hypex HG regulators regulate, the buffer?

I am trying to fiqure out what I need and what I don't. I believe in the less is more ideology. If the opamp is not needed because the Aikido output imp. is already low and the gain is high enough and the regulators are used for the buffer, I would prefer to go straight from the preamp to the imput caps or even bypass them too.

Your input would be appreciated.

Dude
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Old 13th April 2008, 10:13 AM   #2
Koifarm is offline Koifarm  Netherlands
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I have bypassed the opamp with great results. Look here:
Hybrid Hypex UCD

Without the opampstage you need about 4.5 Vtt from the preamp for max. power of the UCD.

It is important that your preamp is DC free if not you still need the caps on the ucd board.

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Old 13th April 2008, 01:44 PM   #3
RX5 is offline RX5  Philippines
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why would you be bypassing the op-amp buffer?? its there for a purpose...

Put it simply, its like a "separation" between the input AND the output switching stage...
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Old 13th April 2008, 08:25 PM   #4
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Quote:
Originally posted by RX5
why would you be bypassing the op-amp buffer?? its there for a purpose...

Put it simply, its like a "separation" between the input AND the output switching stage...


My understanding is that the opamp is there to increase gain and lower impedance from high output impedance sources. If my preamp were to have an output impedance of less than 1400 ohms(will be around 300 ohms) and has a high gain there should be no need for any opamps in my signal path. Less is more philosophy. Essentially, my tubed preamp would be like a discrete buffer replacing the opamp with much greater sonic ability. Even with the new national opamps being very good, I still see them as a bottleneck.

About the regulators, are they only used for the opamp or are they used by the oscillator?
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Old 14th April 2008, 12:21 AM   #5
RX5 is offline RX5  Philippines
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with the opamp buffer(built into it), there is something MORE to that than just being a buffer and impedance matcher...

I dont have a commercial UCD180 here, BUT I did manage to build a DIY(based from a simple scheme w/c hypex has posted in thier site and some tips from this forum) there are actually 3 regulators there....2 of w/c you dont want to touch( the 3uA current source for modu board && a reg for the Hi/Lo side drivers)..

the 3rd would be the reg(bipolar) for the op-amp input buffer && the associated protection circuitry...power ON delay, over current, etc...;
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