Al K -- a couple of Cornwall ALK questions

[Deang]

I've been studying the ALK schematic for the Cornwall, and was wondering if you wouldn't mind helping me out a little.

1) 39uF with a 1uF bypass cap, and then another 39uF without one. If I were to use a better quality cap for the former, could I dispense with the 1uF cap. If so, should the cap be 39uF or 40uF. On the latter, why no bypass cap?

2) 2.2uF Hovland on the tweeter: I would really like to use the AudioCap Theta, but there is no 2.2uF value. Since Hovland makes a 2uF, I imagine you picked 2.2uF for a good reason -- but man, it's only .2 difference. Can I use a 2uF there? If not, would it be O.K. to run a couple of Theta's there in parallel to get the 2.2uF value? Bad, good, or indifferent?

Thanks.

Dean

[Al Klappenberger]

Dean,

The 39 uF connected across the woofer is not required to pass high frequency

energy so it doesn't need to be bypassed. The other 39 uF cap passes

everything above the woofer / tweeter crossover frequency. The idea of

bypassing a large value capacitor is to reduce the losses as frequency

increases. Modern polypropylene caps really do not need to be bypassed. I

just do it as a bit of extra measure.

The 2.2 uF cap is a 5% tolerance part. This means its true value may be

between 2.09 uF and 2.31 uF. If you substitute a 2.0 uF cap with a tolerance

of 10% the value could be anything from 1.8 uF to 2.2 uF. I would suggest

replacing the 2.2 MusiCap with a 2.2 Solen "FastCap" if you want to same some

money. Chances are you will not hear the difference. The Solen cap are also

5%. The wrong value will simply degrade the performance by moving the

crossover frequency and degrading the response curve. It may be only a

little, but it will happen. Anotyher good choice is a 2.0 uf 5% cap with a

.22 uf bypass. Just don't use those high priced, high loss "paper in oil"

things!

Al K.

[Randy Bey]

Hey Dean, I got a few 2.2 Hovlands laying around, I could send 'em to you in the "pay it forward" mode.

[Deang]

Thanks Al.

Randy, remember those nice NOS 6SN7's I sent you? How bout some pay it forward forward?

[Randy Bey]

sure thing, send me your mailing address and I'll pop them in the mail.

[Randy Bey]

Hey Dean,

you should have received them by now, notice I didn't put them under my desk at the office for four weeks ()