Ignoring power output: UcD700 vs. UcD400 vs. UcD180 - diyAudio
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Old 16th January 2007, 09:05 PM   #1
elg2001 is offline elg2001  United States
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Default Ignoring power output: UcD700 vs. UcD400 vs. UcD180

Hi,
I've been doing quite a bit of research on "the ultimate amplifier". I know that's a vague term, but basically I'm looking for the flattest freq response possible. Whatever signal is fed into the amp, it comes out at the output with the exact same waveform but amplified. That's my goal (I think "transparency" is the right term?).

I've been looking into the UcD amps and those are what I'm going to use (unless someone steers me elsewhere). I'll have one monoblock for each of my Adire KitLCR fullrange speakers. I've been researching the UcD options, and the dealer that I'm most likely going to buy the amp from told me that, IGNORING POWER OUTPUT, the UcD700 has better sonic quality versus its lower-powered siblings (the SQ improvements were a result of tweaks based on experience through sales of UcD400 and 180 modules). Is this an accurate statement? Please elaborate on the differences, keeping sound quality the #1 concern.
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Old 16th January 2007, 11:55 PM   #2
zilog is offline zilog  Sweden
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Amplifiers designed for heavier power numbers should in my opinion perform worse sonically. This is based on an assumption of the use of bigger mosfets that can handle higher currents and voltages than the mosfets used in the lesser variants, and the UCD700 being tweaked for larger deadtime due to larger voltage swing than the lesser amps. I dont know how Hypex handles body diode recovery, but if they handle it the same way as I do, switching slow enough to avoid killing the mosfets, then should an amplifier designed for larger output current also have slower switch slopes.

I am completely positive that Hypex are better engineers than I am, but I myself get higher switching time and higher deadtime using mosfets that handle higher power as the associated gate charge grows with mosfet size.

These are just my thoughts on the subject, and I am most likely wrong..
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Old 17th January 2007, 12:34 AM   #3
BWRX is offline BWRX  United States
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Default Re: Ignoring power output: UcD700 vs. UcD400 vs. UcD180

Quote:
Originally posted by elg2001
Ignoring power output...
How can you ignore power output? It's one key piece of information you should use when determining what amplifier to use with your speakers. How big is your listening room? How far away from your speakers do you normally sit? How loud do you like to listen to music? What is the nominal impedance of your speakers? How sensitive are your speakers? The answer to those questions will help you determine the minimum power you'll need/want.

I wouldn't worry about the quality of the 180 vs the 400 vs the 700. I'd bet they're pretty similar sonically. The main difference is of course price. The modules themselves are more expensive and the power supply cost needs to be taken into consideration as well.

If you have money to burn then go all out and get a pair of each! Be sure to report back and tell us how they sound
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Old 17th January 2007, 08:13 AM   #4
lucpes is offline lucpes  Europe
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There have been reviews where the UcD700 were stated to be sounding better (maybe due to separate front-end supplies, but that can be done in both 180&400), I can't find a link right now, but if money were no concern I'd go with the 700's because they have the headroom to handle virtually every speaker no matter how difficult the load is.

Load impedances - both the 400 and the 180 actually handle low impedances without a problem, but each to it's own limits (10A for the 180 afaik and 20A for the 400). The 700 has 28A current limiting and due to its higher voltage swing will sound better with certain speakers.

I own what people call difficult speakers (old Infinity Reference Standard II), they have 2 10" woofers each and combined impedance which dips below 2 ohms and the 400's with a stiff supply drive them with no problem (would have gone with the 700's but money was an issue). Used the 180's before on them and they were clearly a bottleneck even at usual listening volume.

Just my 2ec.
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Old 17th January 2007, 02:42 PM   #5
elg2001 is offline elg2001  United States
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Quote:
How can you ignore power output? It's one key piece of information you should use when determining what amplifier to use with your speakers. How big is your listening room? How far away from your speakers do you normally sit? How loud do you like to listen to music? What is the nominal impedance of your speakers? How sensitive are your speakers? The answer to those questions will help you determine the minimum power you'll need/want.
I've done a ton of research, and I already own the speakers. It's a KitLCR pair of speakers (http://www.adireaudio.com/Home/KITLCR.htm), so it's 8 ohms nominal impedance. The reason I'm ignoring power is because I want the best possible sound quality out of these things. I don't listen to music all that loud usually, but occasionally I like to bump it up a bit for parties at my place.

Judging by what lucpes just said, my guess is a UcD180 will be underpowering them a bit considering i'll only get 90 watts into each speaker. Plus, on the UcD modules, distortion seems to shoot up when you get close to its max power rating. Still good distortion numbers, but nowhere near what you get at max/2 or lower.

So far, I have two votes for the UcD700's sounding best; one vote from lucpes, and one from Kevin at diycable.com (the guy I'll likely be buying the amp from, so I would assume his opinion is somewhat biased because he sells them), and one vote for the UcD180 from zilog (although he states himself that he is probably wrong ).

If you have any sort of opinion on this subject, please share. Please focus on sonic quality.
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Old 5th February 2007, 08:16 PM   #6
GregD is offline GregD  United States
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I've been using a pair of UCD400 monoblocks with a home brew power supply for over a year now, and I've been very happy with them. I just finished putting my first UCD700 together with the Hypex 700 power supply, and hooked it up to one channel with a UCD400 on the other channel.

I haven't had a chance to do any critical listening yet, but the initial impression is that the difference in sound quality between the two amps is pretty small. Of course, it's always that little bit that keeps us tweeking our systems. I should have a better comparison by the end of the week.
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Old 5th February 2007, 08:53 PM   #7
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For the best sound quality change the opamp of the UcD to the new LM4562.
The LM4562 is getting very good reviews in all kind of opamp swaps/installs.
See the thread "UcD400, in summary" :
UcD400, in summary.
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