Cathode Bypass Caps C106 & C112 - Electrolytic?

[Roman Ships]

Ampeg V4B

C106 & C112 Cathode Bypass Caps.
They list as 6.8uF and polarized. According to that value I would assume they have to be electrolytic.

The ones on the board are very small black plastic rectangle types.
Certainly don't look electrolytic.

here is an image i found online.
On the far right top corner you can see black caps.
Those are the ones I am talking about.
http://www.talkbass.com/attachments/74-v...pg.522401/

I ask because I am replacing most of the caps in the amp and especially since they are supposedly electrolytic I wanted to replace while im in there. Unless they aren't worth messing with.

anyone know the scoop on those caps?


Thanks,

[Liquids]

Ampeg V4B

C106 & C112 Cathode Bypass Caps.
They list as 6.8uF and polarized. According to that value I would assume they have to be electrolytic.

The ones on the board are very small black plastic rectangle types.
Certainly don't look electrolytic.

here is an image i found online.
On the far right top corner you can see black caps.
Those are the ones I am talking about.
http://www.talkbass.com/attachments/74-v...pg.522401/

I ask because I am replacing most of the caps in the amp and especially since they are supposedly electrolytic I wanted to replace while im in there. Unless they aren't worth messing with.

anyone know the scoop on those caps?


Thanks,

Yep.

They're in V4*B* amps circuits only and at that, they're for the ultra-low circuitry. They're cathode caps at a certain value for a low-mid bump, when combined with the other circuitry in the ultra-low.

Do you use the ultra low? I mean, by all means, replace them if you feel the need, because as you said - you'll be in there (and getting at that board IS a bit of a time-suck when you need to get at it for anything).

But that's the scoop.

[Roman Ships]

Yep.

They're in V4*B* amps circuits only and at that, they're for the ultra-low circuitry. They're cathode caps at a certain value for a low-mid bump, when combined with the other circuitry in the ultra-low.

Do you use the ultra low? I mean, by all means, replace them if you feel the need, because as you said - you'll be in there (and getting at that board IS a bit of a time-suck when you need to get at it for anything).

But that's the scoop.

Thanks ! So is the value not super critical? That is, 8uF might ok? 8 uF electrolytics seem easier to find than 6.8.

[Liquids]

Thanks ! So is the value not super critical? That is, 8uF might ok? 8 uF electrolytics seem easier to find than 6.8.

If you use the ultra-low, the value is semi-critical for the intended frequency response.

Consider putting caps in parallel if you use the ultra-low.

I could run some plots via spice etc to see the difference with 8uF, which might be minimal, but with 8uF you are going to get more of a low end boost than intended (those 8uF rated caps may be 9uF in realtime anyhow) - the ultra low is kind of like an overall boost that shaves off some ultra lows and highs, which ends up being like a low-MID boost. So a larger cap would end up boosting a wider band extended more in the lows than with the 6.8uF cap.

It's significance may be more about taste. But this is low voltage - for a preamp tube's cathode, 25v caps should be plenty. I have 6.8uF caps at that voltage myself I think, just because. I'd parallel a 4.7uF with a 2.2uF if not.