| Koifarm |
Here in the Netherlands they build a great amplifier module from Hypex (http://www.hypex.nl)the 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(http://www.hififever.com/forum/viewtopic.php?t=1738) and so i spend this chrismas holiday by modificate my Ucd amplifier.
Goal:
- Do not use the opamp inputbuffer. Direkt drive the UCD.
- Bypassing the 22uF decoppling capacitor.
- Improve the sound with some more live.
Reminders:
- 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.
http://www.lampizator.eu/
At how about the sound the UCD are now alive. I like it. |
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| Koifarm |
After one week of listening to the 6N6P tube, i have now placed the ECC99 tubes. After i switched the heater connection.
One thing i heared directly the ECC99 has less bass but also less noise. I will listen this week to the ECC99. |
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| Koifarm |
After using the circuit for a month and build several for friends, one thing is very important. If possible let the tubestage warmup for 20 sec and then turn the UCD on. During warmup there is a lot of DC at the output of the tube this can damage the UCD.
If you intergrate the tubestage in to the UCD housing and you use one on/off switch then ad a relais contact shorten the tubestage output to ground. When switch on a timer can drive the relais after 20 sec. to open the relaisontact. The timer can be a simple circuit with NE555 or just RC and fet.
My friends and i like the sound of the 6n6 tube with the UCD. |
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