from forum


Here in the Netherlands they build a great amplifier module from Hypex ( Ucd series. I have the standard serie and i used it for 2 years. The modules sounds perfect, so perfect that with time i got boring. I read a lot of the modifications with were possible but nowhere a read about using a tubebufferstage for the Ucd. Luckely a had experience with the modification of my shanling CD-T100se( and so i spend this chrismas holiday by modificate my Ucd amplifier.


- Do not use the opamp inputbuffer. Direkt drive the UCD.
- Bypassing the 22uF decoppling capacitor.
- Improve the sound with some more live.


- Input impedance = 10k
- Source must be DC free
- Compensate 4,5 X gain of the opamp

At work:

I removed the decoppling caps of 22uf from the UCD pcb.
They were between the opampinputbuffer and the UCD powerstage. Then i connect the input sym.+ en sym - to the new points on the PCB according the picture below.

Now i only need a max 5 V rmss input signal with i can get from my shanling player by using a higher value of the I/V resistor in my tube output stage.
My shanlingplayer is the first 10 seconds not DC free so i must wait 10 sec before i press play the first time. Other wise the UCD going pumping.

If you have a tubepreamp with has 5 Vrmss output you can use that.

For the people who want to intergrate the tube stage in to the UCD housing i have a nice schematic.


This is the same SRPP circuit i use in my shanling player but with other tubes ( 6N6P ). With enough gain ( 11 X ) and working with a voltage of 40 V and higher so you can use the original UCD power supply. For the heather voltage you can use 12 V by putting two tube heaters in serie.
This SRPP circuit you can build ones a channel for RCA input and twice a channel for symmetrical input.
The sound of this SRPP circuit i perfect, see this link from Polen.

At how about the sound the UCD are now alive. I like it.

Koifarm 在 2008-01-03 (星期四) 8:50 pm 作了第 1 次修改