DIY Pre-Amp for UcD400 or UcD180 - diyAudio
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Old 16th October 2004, 11:35 PM   #1
mettel is offline mettel  Netherlands
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Default DIY Pre-Amp for UcD400 or UcD180

Hello all,

I am looking for a good diy pre-amp to connect to my still to built stereo UcD400 or UcD180 stereo amplifier. I have been looking over the forum but couldn't find suitable hints. However, i found some congenial souls looking for the same answer. I am worried about conventional pre-amps with no balanced output. As i understood it is adviceable to use a balanced pre-amp coz of the DC issue.

I found for example the Velleman K8021 during my search the last few days. I believe that it has at least to be upgraded with the OPA627 op-amp instead of the NE5534 but don't know if this pre-amp will be suitable at all.

I don't like to pollute this forum but I hope someone can shine a light on it in this thread.

Mathieu
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Old 17th October 2004, 09:03 AM   #2
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Hello Mathieu,

I am also building an UCD400 amp right now and was looking for the same thing.
I found a nice and reasonably priced high-end
preamp project on the Schuro website:
http://www.schuro.de/preisl-minipre627.htm

They also have versions for other OPAMPS. If you want to go
more high-end (with discrete OPAMP!), check this out:
http://www.thel-audioworld.de/module/vxpro/vxpro.htm

In addition you need is an attenuator, an input selector
and balanced inputs (from Neutrik).

Looking forward to hear how you like the UCD400!

Regards,

Michael
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Old 17th October 2004, 11:06 AM   #3
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I'm also looking as well. I can't read german, but has anyone tried the preamps mentioned by Michael? I was considering DACT's preamp as well.
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Old 17th October 2004, 11:53 AM   #4
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Old 17th October 2004, 12:52 PM   #5
IVX is offline IVX  Russian Federation
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I've simulation for the direct (almost) cloning opa627, just in class A SE output stage, and all the 17 SMD(PCB 30X40mm) transistors+ others =$2, also i saw very simplified discrete opamp (5 tr-s) on the diyaudio.com.. so, actually, more high end would be for a less money+ flexibility and up to +/-25V rails, that's much better vs +/-15v, if 2V output is still used.
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Old 17th October 2004, 04:39 PM   #6
mettel is offline mettel  Netherlands
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Quote:
Originally posted by mlihl
In addition you need is an attenuator, an input selector
and balanced inputs (from Neutrik).

Looking forward to hear how you like the UCD400!

Regards,

Michael
Hello Michael,

I'm very interested in what your final choice will be for the pre-amp. Also wondering what other DIY UcD amp builders have chosen.

You mentioned "balanced inputs (from Neutrik)" I don't get what is meant by it. Tried to find how to implement this but don't have a clue what it is about. Does the circuit prevents a dc load on the outputs of the pre-amp?

Regards,
Mathieu
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Old 17th October 2004, 05:49 PM   #7
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Hi Mathieu,

The Neutrik connectors are for the balanced inputs.
As far as I know, all of the aformentioned preamp concepts
support balanced inputs out of the box. So there shouldn't
be any DC issue. I am also considering Thel's tube preamp
(a beautiful amp!), however I am not sure whether
the UCD likes tube gear...

Price-wise, the Thel preamp with discrete opamp is
the same as the Schuro stuff and the modules are
already pre-assembled. Some owners have reported
that the VX Pro blows away the most expensive
Burmester stuff. That should make the decision easy.
However, I am also in the market for a new DAC.
Maybe I can implement a preamp there. Since I haven't
owned any tube equipment yet, a tube preamplifier
would also be a dream. I will complete the UCD and
think about this decision for a while. Currently I am
shopping around for a nice enclosure.

I will make a preamp decision in about 2 weeks from
now but I will keep you updated on my choice!

Regards,

Michael
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Old 18th October 2004, 12:27 AM   #8
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Quote:
Originally posted by IVX
I've simulation for the direct (almost) cloning opa627, just in class A SE output stage, and all the 17 SMD(PCB 30X40mm) transistors+ others =$2, also i saw very simplified discrete opamp (5 tr-s) on the diyaudio.com.. so, actually, more high end would be for a less money+ flexibility and up to +/-25V rails, that's much better vs +/-15v, if 2V output is still used.

Not sure what your saying, could you elaborate or provide some links.
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Old 18th October 2004, 05:46 PM   #9
IVX is offline IVX  Russian Federation
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Default some links:

Jfet/bipolar PCB and Schematic (finaly)
Descrete Component Op Amp Idea

Dual discrete opamp PCB in DIP8
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Old 24th October 2004, 06:37 AM   #10
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What are the pro's and cons of just using a high quality pot on the input of the UcD400 instead of a pre-amp? Would it be a big difference in sonic quality, or is it a cheap way to get by for the time being?

What would be the correct size and correct way of wiring? Do I have to consider the output of the cd player (or DAC in my situation).

Thanks
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