Increasing the output coupling caps value

[Noskipallwd]

Is it feasible to increase the output caps value from 2.2uf to 10uf. I happen to have a couple of really nice caps at 10uf, just thought I would check to see if I could use them. Thanks for any help.

Cheers,
Shawn

[Grainger49]

The main thing to come from that is that you will spend more money than you need to.  The stock cap is calculated to form a very low frequency, high pass circuit. 

Of course, if the 10uF are better sounding caps, and since you already have them try it!

[Noskipallwd]

Thanks Grainger, yeah I have a couple of ampohm tin foils at 10uf. They are a little big but I think I can get them to fit.

Cheers,
Shawn

[Grainger49]

Shawn,

I am convinced that dangling capacitors do no harm.  Those with better ears might disagree.  But in the case of swapping output caps it is always ok to even clip them in with jumpers to make the decision.

[earwaxxer]

Hey Shawn -

Curious to get your take on the 10uf ampohms. I also have a pair of 10uf ampohm paper in oils kicking around that I once used in a speaker crossover.

I now have 2.2uf Mundorf silver/oils on my Quickie. Spent more on those than I did on the 10uf ampohms. I havent experimented with the amphoms in the quickie because I tend to, in general, like the Mundorf silver/oils over the ampohms. You never know though! I hate/love this hobby!

Eric

[Noskipallwd]

Eric, I just ordered the kit so it will be a little while, but I will certainly let you know my impressions when I get it built. I also really like the Mundorf silver oils, I am preparing to build the Eros and am going to use the silver oils in the output and interstage. I have found that the ampohm copper foil pios sound remarkably similar to the mundorf s/o, too bad they are discontinued. A friend told me he really liked the way the wax and aluminum foils sound, I think I might grab some for the heck of it before they disappear. I already have some Elna silmic II 1000uf, 35v that I plan on replacing the cathode bypass caps with. Looks like I will be busy building and listening for a while. It is a crazy hobby but I can think of far more destructive things I could be addicted to instead!

Cheers,
Shawn

[Paul Joppa]

... I am preparing to build the Eros and am going to use the silver oils in the output and interstage. ...

The Eros is direct coupled, so there is no interstage. There are however two cathode bypasses, which can benefit from better caps. The more critical one (I think) is the one on the EF86, 2700uF/4v originally. I'm not sure what's in there right now, the original OsCon became unavailable IIRC. Just FYI  :^)

[Grainger49]

I looked for a replacement for the 2700uF and could not even find the 2700uF.  The voltage across it is very low, a little over a volt.  So a higher voltage rating is not suggested for this element, if I remember what Paul said before.  What I got last fall, if it wasn't an OsCon was another organic dielectric like the OsCon.

[Noskipallwd]

Thanks Paul and Grainger,
I am not sure why but I thought there were some 0.1uf caps in the Eros, besides the output caps and the organic electrolytics used for the ef86. Well, in that case I have some Mundorf 0.1uf s/o caps that need a home. I'm sure I will find somewhere to put them. I guess I should have been more specific, but the elna silmics I spoke about are for the quickie,not the eros. I looked for actual Sanyo Oscons for the eros but could not find any at the correct value.

Cheers,
Shawn

[Paul Joppa]

I should probably not say this, but you can replace the cathode resistor and bypass with an LED. It will sound better. But you lose the bias feedback, so the operating point is more sensitive to tube variations, and less tolerant of fading battery voltage. That means you would have to reject more tubes that are fine but don't bias up at just the right voltage, and replace the batteries long before they are exhausted.

It does not seem like a good tradeoff to me. But I keep it in mind, there may be some practical way to meet these problems. I'll work on it.

[Noskipallwd]

It does not seem like a good tradeoff to me. But I keep it in mind, there may be some practical way to meet these problems. I'll work on it.

I agree paul, considering the variability of the 3S4 from one brand to another. You would have to buy quite a few tubes to find some that would work. Although they are cheap it could add up fast. I remember a post about doing a similar mod to the eros, but this would limit you to using expensive NOS ef86 variants. It's nice to know there are alternatives to stock, in case I get a little adventurous. By the way, my original question, can I get away with using 10uf caps in the quickie output?

Cheers,
Shawn

[Paul Joppa]

Oh - yes - the original post slipped my mind. No sonic problem with larger output caps. Of course the turn-on thump will be larger, but the smart person turns the preamp on before the power amp...