2 for the board about the BLS

[Buhl]

Hi there

About to assemble my BLS, I have two questions that I feel need answering before I go any further.

1. Output potentiometer - I know this have been discussed before, but still: I am building balanced, and want to use the trick with a stereo potentiometer shortening the balanced live rails - so that every half of a stereo potentiometer thereby adjusts the volume on one balanced channel.

I have a Noble 100KOhm stereopot that I would like to use - is 100K to much / appropiate in this configuration ?
What about the load for the mosfets, when the volume is at its lowest, and they are "seeing each other" - is the two 221 ohm resistors enough, or should I insert more resistance to protect the fets ?


Output caps: I have had much difficulty with gettin good 10 uF caps at a "resonable" price. I have found 4 Vishay Roderstein 3,3 uF MKP caps - those should however not give me the desired low freqency cutoff - should I not loose some bass with that low value ?

Then I have also found some 100uF 25 volt ELNA Cerafine electrolyts, wich are supposed to sound very, very good after a few weeks of use - so I'm told.

What do you think - if I use the electrolytics in parallel with the MKP's, my cutoff will be correct, but will it affect performance of the sound (audiable)?

Will 3,3 uF be enough - I'm planning on running an aleph 5 with it (dont know the input impedance of A5...)?


Cheers & Thanx !

/Hans

[Ignatz]

Hans:

I use a balanced attenuator before the output blocking caps on my BZLS and it works very well. It is simply a 23 position swicth which places one resistor between the + and - of each channel.
The last switch setting has no resisitor so this provides for full volume.

The swictch contacts see no measurable DC. This configuration allows me to split the signal to an all pass to Gradients and a high pass to FREDs like yours.

Erno Borbelly gave me the resistor values. If you want them let me know.