[rpf]

Hi all,

I'm interested in upgrading some caps in my MHDT Havana DAC (vocals are a touch dry, even grainy). Can I replace two 2uf/250v caps (output coupling, I believe) with two 2.2uf/650v ones?

In general, if caps have the same uf value can one use a higher voltage value?

TIA,
Rob

[face]

Since they're within 10%, you should be ok.  Higher voltage shouldn't be a problem either.

Which caps are coming and going?

[avahifi]

Does your DAC have a solid state or vacuum tube output circuit?

If solid state, the 250V rating on the present caps are probably way overkill.  There are lots of excellent lower voltage capacitors available. Check with the manufacturer to find out if that voltage rating is really necessary.

If a vacuum tube output stage, then the 250V rating is likely necessary.  However, as I understand it, if you use capacitors at a much lower voltage than their rating, such as you are thinking about doing, then the actual capacitance value of the part will be different than its nominal rating.  This might provide unanticipated results!

I suggest you stick to the existing voltage rating if you are not sure about this.

Regards,

Frank Van Alstine

P.S.  Dry and grainy vocals are the bane of audio designers.  The issue is likely more related to circuit design or choice of active parts than to passive components, unless there is a real blunder in design, such as using polarized capacitors in an application where audio voltage swing can drive the positive end into negative voltage operation.  This was common in older designs but I hope all designers are aware of this pitfall now days.

[face]

How come when I test a pair of 6.8uf 800v caps with a AA powered LCR meter, they still read 6.8uf?

[avahifi]

I don't know why.  All I am reporting is what has been reported to me.  Maybe a better engineer than me can explain.

Regards,

Frank

[GBB]

However, as I understand it, if you use capacitors at a much lower voltage than their rating, such as you are thinking about doing, then the actual capacitance value of the part will be different than its nominal rating.  This might provide unanticipated results!

I suggest you stick to the existing voltage rating if you are not sure about this.

I'll respectfully disagree with Frank on this point, especially if we're talking about film caps.  Having the capacitance change with applied voltage would imply that the dielectric constant of the insulator was changing with voltage.  That might be true with some electrolytic caps (but even that seems unlikely) but it is definitely not the case for film caps.  In fact, I believe there are real advantages to using film capacitors with higher than the needed voltage ratings.  The electric field across the capacitor dielectric will be further away from the voltage breakdown limit of the dielectric and thus likely to be more linear.

---Gary

[Niteshade]

The only thing I can think of is this: When a capacitor is used close to its rated voltage, the forming process could be more uniform. Some film caps have a self-healing feature, so this might stand true with them as well.  Just a hypothesis! 

[NagysAudio]

The answer to both of your questions is "yes." I would however ignore a lot of the other responses you've received.

[rpf]

Thanks all! Interesting and informative responses.

The existing and replacement caps are both film/foil types. The existing caps are proprietary MHDT ones, and I was planning on using Jupitar HTs for the replacements; partially because they are the closest in uf value I could find that would fit reasonably well and were at least 250V.

[jtwrace]

The answer to both of your questions is "yes." I would however ignore a lot of the other responses you've received.

Why is that? 
Can you elaborate on your thoughts?

[Quiet Earth]

I'm interested in upgrading some caps in my MHDT Havana DAC (vocals are a touch dry, even grainy).

The two large yellow "MHDT" coupling caps are probably the only upgrade you'll need to do to that DAC. I have the Constantine+, and even though I changed a lot of the other caps, it was the two output caps that brought the lion's share of improvement to the DAC. If dry and grainy is what you want to avoid, then pick a cap that is not hyper detail oriented. In other words, I would avoid the ever popular teflon.

The main question :

[/quote]Can I replace two 2uf/250v caps (output coupling, I believe) with two 2.2uf/650v ones?
[/quote]

Yes, you can. You can always go higher in voltage with your replacement coupling caps without worrying about saftey. As for capacitance, the difference between 2.0 and 2.2 uF is probably within the tolerance variation of the parts anyway, so it's not an issue. If space is an issue, you may find that you don't need the whole 2uF of coupling capacitance. For example, I am using 0.47uF copper paper in oil in my Constantine+, and there was no feeling of inadequate bass drive after stepping down from the MHDT 2uF caps. The sound quality sure got better though  .

So there you go. You have more options than you thought. You could look at 1uF caps or maybe even 0.47 and save some space and a little money too.

[rpf]

Thanks, QE.