UCD180 questions

[Wasim]

Originally posted by Javin5
What exactly do you mean when you say that after half of the volume the sound starts to distort? Half of what volume? Or did I miss something here?

For example, it could well be that your music peaks reach the rated output power way before you fully turn up your volume; this is even quite common. It depends on the source, the gain of your preamp and the gain of the UcD.

Kurt

Kurt thanks for the reply,

I mean that the half of the preamp volume the bass is not very tight. It starts distort. The gain of the preamp is 20DB. I am not very technical. I just would like to ask is it happen with every amp ?or its C73 problem. When I use source signal direct with power amp UCD its perfect even with the full volume. I hope you understand what I am trying to ask.

Best wishes
Wasim

[Wasim]

One thing I would love to say The UCD is the best sounding class D amp.

Wasim

[Javin5]

I don't think that the Pioneer preamp is a problem. A CD-player will put out about 2 Volt, which is enough to drive a UcD180 to its full power. If you add an additional 20 dB of gain (a factor of 10), than that's much more than you need and you have to decrease this by the volume control, otherwise you will severely overdrive the input of the UcD180.

Since the highest levels are often found in the bass notes, the low frequencies will start to distort first. In addition, as TerryO pointed out earlier, many speakers will severly distort if you apply the full power of an UcD180 at low fequencies.

The conclusion is that it is quite natural that you cannot utilize the full gain of the C73. If I remember correctly, older preamps were built assuming around 250 mV from "high level" sources. Newer preamps generally have less gain, sometimes they are merely unity gain buffers or even passive. And some CD-players have a volume control and you can directly connect them, without a preamp, to a power amp. I have also seen external attenuators, which can be connected between cd-player and preamp to reduce overall gain and operate the volume control more in the middle position than in the first few degrees of the rotation angle.

[SDF]

Just for fun, one pic of my ucd!

[Javin5]

Very nice!

Kurt

[Wasim]

Originally posted by Javin5
Very nice!

Kurt

Hi Kurt Thanks for the reply. I understand that now.

Regards

[steklp83]

hi friend
I will buy the transformer for ucd 180 mono amp
300va 33-0-33!
it's well this transformer for one ucd180hg
thx

[SDF]

Thanks Javin5!

@steklp83, 300va 33-0-33 is a well for one ucd180hg....and even for two ucd180hg!

[steklp83]

capacitors for power supply is better 22000 or 10000+ 10000 for rail?

[maxlorenz]

To whom it may be of interest:

UCD amps also benefit from the "charge transfer" power supply develloped by -ECdesigns- on his thread about Ultimate NOS DAC. Just adapt to needed voltages and current capability of active units.

http://picasaweb.google.com/lh/photo...eat=directlink

I did not implement the "capacitance multiplier" part of the circuit yet, because of space constraints.

This mod cleans up the sound quite a bit.
I used IRF5210 for the Pchannel Mosfet, IRF930 for the N channel (if I remember correctly) and a high current high V for the power Schottkies. C1 is a 10000uF Panasonic TSHA and C2 is a 10000 BHC big can capacitor, per side.

I hope you like it,
M