[PatOMalley]

Jim,

is it ok to increase the output cap value on the Cornet2 to 4.7uF?

[tubesforever]

I have gone as high as 1.19 and as low as 0.92 and didn't really hear much change.  I think Jim said you could expect to hear a change to the frequency response if you jump outside the +/-10% value. 

What makes you want to try 4.7 uf?  Did you find an interesting motor run cap?

You could use these to bypass the 47uf B+ bypass caps. 

Cheers!

[PatOMalley]

I read where someone increased their output cap value from 2uF to 4.7uF on the Foreplay which reduced FRI. Even though I am using the CineMag transformers I still wanted to try to get the Cornet to be quiet standalone.

[PatOMalley]

snip..

 I prefer a 1uF for output coupling capacitors because it can still deliver 16Hz rolloff into a 10k ohm load.  Too small a capacitor means you lose bass, too big and you pass too much rumble.  IMHO, 1uF is the best compromise considering the range of preamplifier loading that the capacitor will experience.

..snip

jh

Ahhhhh, so now, with my new SiNi bearing I should have rumble in vanishing amounts.

A 4.7uF cap in this case may be acceptable; Worth a try.

[tubesforever]

I would try for  1.5 uf or 2.0 uf as your first testing ranges. 

The uf value he selects is to accomodate a low frequency crossover point that reduces woofer pumping.  I worry that what you gain in bass extension might be eaten up in paralytic losses from wp.  I wish I had a scope to check all this out personally.  It would be fun to try to hit say 9 hz vs 12 hz as the crossover and see what happens with wp in my own system.

However like Jim states, if the table is up to snuff (which would include the table platform and footers ability to control accoutical feedback) you might be able to have your cake and eat it too.

Pat, isn't diy the best!  I can already tell, I will be spending some more money figuring this one out!

[PatOMalley]

Why wouldn't that table be up to snuff?
Ha. It is a Technics SL1200 with your modified Silicon Nitride bearing.
But I will cut the mean and a little more and go for 3uF.

I am not looking for bass extension. I am looking to squelch the hum. The CineMags do a good job at that but But I want to push it back so that preamp can standalone without hum not using the transformers.

[hagtech]

Sure, you can increase output cap value.  Just don't go too high, or you'll get a bigger and bigger power-on -off thump.  This won't change the bass rolloff, though.  That is set by the 0.1uF coupling cap between 1st and 2nd stages...

jh

[PatOMalley]

Thanks Jim. Great news.

I have a Bendix in the Clarinet which takes too long so a power on thump is no issue.
Just switch to a different selector on power off and no thump.

And bass is fine and sometimes ponderous so no worries about changing the .1uF for me.