Increasing capacitance in this circuit, will there be major negative results?

Kenwood KR-9400 tone control board.

IMG_7026.jpeg


There are 10 capacitors on the board marked in red above that are 6.8 uF 10v bipolar electrolytics. That is such an odd value, not something I keep on hand. I have polar, but not non polar. Would there be any significant harm by increasing to 10 uF? I have dozens of 10 uF 25v Nichicon ES or I could do 2.2 and 3.3 in parallel and go down a little, but would really prefer to use a single cap in each location. I’m really trying to avoid placing an order for one item and if I buy extra to get the cost per piece down it’s likely I’d never need them again, I haven’t until now.

Thank you,
Dan
 
6.8uF is E6 series, how is that an odd value? 1.0, 1.5, 2.2, 3.3, 4.7, 6.8, 10.0....

As a datapoint 6.8uF is an impedance of 1.17k ohms at 20Hz, I suspect you'd get better bass extension moving to larger values than just 10uF for some of those coupling caps. Say 47uF? Then there will be much less signal voltage across them at the bass end and they won't be able to contribute as much distortion, as well as getting a lower frequency roll-off. Ci18 and Ci19 seem to have a very high impedance load and can probably be smaller in value, incidentally, perhaps film caps will work there.

Ci3 and Ci4 seem to be the most crucial as they drive the relative low impedance of the Baxandall filter.

Anyway they have used a one-size-fits-all approach to all those coupling caps in order to reduce the size of the BoM, rather than pick logical values for the impedances in question.
 
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They are all in a direct signal path...
If tone defeat is used, there are only 2 (in that part of the amplifier)

The caps are already bipolar ("for sound")... I wouldn't touch them.

Edit: any reason why you want to replace them..??

I’m just going through it as it was really misbehaving and I found several capacitors with high esr. Since it’s nearly 50 years old and it’s such a pain to get taken apart it just makes sense to replace them all at this point.

I would use your 10uF 25V Nichicon ES caps. They are excellent, and no problem with the higher value.

But here are some bipolar 6.8uF 50V caps.
https://www.digikey.com/short/3d2b727p

Mail Digikey a check for the parts plus your state tax, and they pay the shipping.
No minimum order.

Excellent, advice is was looking for! Thank you for the link, I actually did find those, but I’m guessing those are the speaker crossover series???? They’re enormous, over double the diameter and height of the originals. I wouldn’t be able to get them to all fit onto the board correctly.

6.8uF is E6 series, how is that an odd value? 1.0, 1.5, 2.2, 3.3, 4.7, 6.8, 10.0....

As a datapoint 6.8uF is an impedance of 1.17k ohms at 20Hz, I suspect you'd get better bass extension moving to larger values than just 10uF for some of those coupling caps. Say 47uF? Then there will be much less signal voltage across them at the bass end and they won't be able to contribute as much distortion, as well as getting a lower frequency roll-off. Ci18 and Ci19 seem to have a very high impedance load and can probably be smaller in value, incidentally, perhaps film caps will work there.

Ci3 and Ci4 seem to be the most crucial as they drive the relative low impedance of the Baxandall filter.

Anyway they have used a one-size-fits-all approach to all those coupling caps in order to reduce the size of the BoM, rather than pick logical values for the impedances in question.
C119/C120 could be jumpered out, the following stage is unity gain


Well yes, I use 6.8uF somewhat frequently when playing with diy speakers or refurbishing old crossovers, but 6.8uF is a value you nearly never see in the electronic circuitry side of things. I have some polar 6.8s I bought 5 years back or so and I used them just the one time. And this is my biggest hobby, I work on fixing electronics almost daily, I just don’t run into them, the first time for bipolar. I mean the fact that Nichicon doesn’t have the value in their ES line shows it isn’t really used all that much.

I really appreciate the advice. I do have some 47 @ 16v in the ES line as well. Do you have a recommendation as to out what where? I figure in a lot of this older stuff it was a one size fits all.

As in:

Ci3 and Ci4: 47uF
Ci19/Ci20: jumper (as suggested by David, Mark saying they can be a smaller value)

That leaves
Ci17/Ci18
Ci21/Ci22
Ci27/Ci28

Go for 10uF for those 6? Or would any of those benefit from a jump to 22uF, 33uF, 47uF?

Thank you,
Dan