Couple of Qs regarding SSL Tech's balancer reduced...

http://www.groupdiy.com/index.php?topic=196961#196961


hi

i need to balance this output (please see the link above) and would like to use Keith's balancer from his SSL9k mic pre design.i am wandering:

1)have i reduced his 2ch design to 1 ch. only successfully?
2)are 100n caps. ceramics?
3)any suggestions welcome...



thank you

m

How about your voltage rails?

+/- 18V .all other ics are tl072 and 5532.

Try the IC datasheets.

People seem to like using NPO/COG ceramics for audio circuits as they perform better.

I like the polypro parts for decoupling, but NPO/COG are fine. Add some 100uf lytics in parallel with the 100nf for some reserve.

Those output capacitors are rather small.

I would increase to at least 1000u if you intend to drive 1k loads or higher. use 2200u for 600R loads.

Really...

You need those caps on the output only for protection against phantom power and you can leave them out.

Cheers,
Mike

2200u caps into 600 ohm balanced load would give lower corner freq
at 0.25 Hz. That would be usefull with 600ohm transformerless inputs
or with 600ohm input TXs that can go down to 0.25 HZ. I'm not aware
of either.

cheerz
urosh

[quote author="cuelist"]I would increase to at least 1000u if you intend to drive 1k loads or higher.[/quote]
Math seems completely wrong here...

The higher the load impedance, the BETTER a given cap value will perform, and the less need to increase the value.

Using 100µF, the corner frequency should be in the region of 5Hz into a 600Ω load, shouldn't it? -If that sounds like you're losing bottom end, feel free to put whatever size cap makes you feel good in there.

For local decoupling by that IC, what you really need is something fast, so 100nF ceramic will be fine.

I really don't get into the whole "X type of dielectric sounds mushy (or whatever) to me" debate. If you are going to spend time debating over that sort of thing, remember that time is money. 100nF caps are usually only a few pennies no matter what they're made of. Buy some ceramic, some polyester, polyprop, some silver mica, some pressed silk and some unobtanium. If you can hear a difference, feel good that you took the time. It cost you less to "buy-em an' try-em" than the time you would spend discussing which is going to sound better...

All I know is that if you put dodgy electrolytics in there as local high-frequency stabilisers, things get unstable. That's what the 100nF caps are there for, and using ceramic close to the chip I don't get any instability. I'm sure that anything that performs better than writing paper between two sheets of tinfoil will work just fine...

:wink:

Keith

I would parallel some 10uf-100uf with the 100nf. the 100nf is for HF shorting, essentially a lowwpass filter. the higher value cap is for rail stability. if the output swing is fast and hard then you will need that extra capacitance to bolster the immediate current draw to keep the voltage potential up on the rails.