Q: VR2 on Aleph-X

[jrsun]

built Alpeh-X last Fall, run with XLT input, sound great. Now thinking of passive pre-amp, however I do not have balanced source. so I shorted pin 1 and 3, but have to re-adjust VR2 (200 ohm) to minimize the DC offset. then come the questions. the VR2 reachs the maximum value but DC is still very high, about 0.7V.

1. Is it normal ?
2. if yes, I guess I need repalce with a new VR, what values of VR should I use to reduce the DC to safe value, say less than 100mv?
3. any significant difference between rca and xlr inputs to alpeh-X ?
4. what value of VR in passive preamp is recommended ?
Thanks!

[wuffwaff]

Hi,

1. Yes, if you don´t use a cap between -IN and ground dc will change. Normally you should use the same input cap for +IN and -IN. Then the rel. dc offset will also go down.

2. see 1.

3. This is very difficult to compyre because the source is never the same. Theoretically it should work fine with a single ended input.

4. This depends on the length and capacity of the cables you use. With an Aleph-X with 10k input impedance I wouldn´t use a passive preamp.

William

[jrsun]

Originally posted by wuffwaff
Hi,

1. Yes, if you don´t use a cap between -IN and ground dc will change. Normally you should use the same input cap for +IN and -IN. Then the rel. dc offset will also go down.
William

William, thanks!
Is it true that even if no input connection at all to Alpeh-X then adding a cap can reduce the DC ? I thought the cap is to block the DC input to Aleph-X, maybe I'm wrong !

[wuffwaff]

Hi,

well you do connect the input, to ground. This way both inputs will see a different impedance to ground and this will change the dc offset.

William