2a3 Capacitor question

[earwaxxer]

Debra - I would be curious how the v-cap sounds as a bypass cap! I have been curious about them. Tres expensive!

[BNAL]

I have the Mundorf silver/oil caps in my Paramount's, but never thought to add a bypass cap to them. I have a pair of Russian Teflon 0.1uF caps that I could try. I think that I will start burning them in.

[earwaxxer]

Hey Brad - Not sure you would gain anything bypassing such a good cap. I think the general consensus is to only bypass when you really cant afford to upgrade the cap in question. Bypassing is a double edged sword. The caps have to play well together. The Mundorf silver/oils IMO have all the desirable characteristics of the best caps (clean, but organic, good soundstage, lack of glare, good separation of instruments, low noise) .  Adding a teflon may sterilize things a bit. Make it a bit too clean. If your system is already a bit too organic and tubie, that could be a good thing. Curious to hear how it works in your system though.

[debk]

So is the consensus that he Mundorf silver/oil is ok with the 2a3 Paramount?

Don't want to spend the money on them is they will have a problem with the heat


Debra

[Grainger49]

I just looked at the Mundorf site.  The Silver/Oil are rated for 55

[Paul Joppa]

Sorry that the discussion got more general without getting specific first!

I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).

That's because I am a moderately cautious engineer by trade, of course - I have not attempted to measure the temperature directly inside any of the cases, mostly because it will be so dependent on the circulation (inside and out), ambient air temperature, and power line voltage. Empirically, we have not seen failures with parts rated 85C or greater. We have seen failures of for example the original Jupiter beeswax caps in the S.E.X. amp - I can't remember but I think they may have been rated 50C? (Jupiter has since revised their construction, and we have added ventilation slots to that amp.) We've seen failures in C4S installations, so I've revised my design rules - many products now have heat sinks and/or use larger transistors.

For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.

Also for what it's worth, the effective environmental temperature is usually around a 50/50 mix of sir temperature and radiation temperature averaged over the usual 4-pi steradians. If a part is close to a power resistor (for instance) it can see some high radiation temperatures!

[debk]

Thanks Paul, having been a cautious engineer at one time I understand you reasoning.

So the Mundorfs are a no go.  I may give the Clarity Cap MR a try, or take Grainger's suggestion and go with the Obligatto oil cap.  I wonder how the Obligatto would sound bypassed by the Vcap teflons I have siting around


Debra

[Doc B.]

For what it's worth, I have never liked bypassing a larger coupling cap with a smaller one. The resulting sound often seems smeared. I might consider bypassing an inexpensive high capacitance 'lytic in a power supply, but what is the point of buying a boutique cap if you have to bypass it with a boutique cap?

[2wo]

Hi Debra,
Have you tried the Russia K40? Paper in oil. May not be as starkly truthful as the Teflons, but very easy on the ear.

 And still cheep...John

[Grainger49]

Thanks Paul, having been a cautious engineer at one time I understand you reasoning.

So the Mundorfs are a no go.  I may give the Clarity Cap MR a try, or take Grainger's suggestion and go with the Obligatto oil cap.  I wonder how the Obligatto would sound bypassed by the Vcap teflons I have siting around


Debra

Debra,

Can't hurt to try.  The Ack! dAck! offers a "Teflon output option."  It is a 0.1uF bypassing the stock Auricap.  So it is done, and results vary. 

[InfernoSTi]

I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).

For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.

Thanks, Paul, this is very helpful 

What I am wondering is that several of us are using "underrated" (for heat) boutique caps in our amps with great success and over a long period of time (I've been using Mundorf S/O in my Stereomour for a year, for example.  I believe others have even used Jupiter caps, perhaps).   Given your statement about design temps, I should remove my Mundorfs.   This is unlikely to occur, however, because they sound great! 

So what can we do to cool the interior?  I'm thinking a lot more airflow, perhaps even forced?  I don't want to get too complicated but surely there is a nice 12v DC fan that could be added in some reasonable manner to increase airflow.  I really want to try the Mundorfs in the Paramounts without too much worry.

Best,
John

[Grainger49]

I have Mundorf SIO in my Eros, it is up on spikes increasing ventilation.  I have the same caps in my FP 2 and the base doesn't even have feet on it.  I'll probably put spikes on it too after Paul's post.

I liked the recent picture of a custom Bottlehead product, can't remember which, with a grill at the back of the base and a fan that snuggles up to the grill to increase cooling.  Using a 12V fan on a 9V or 6V supply will decrease the speed, lower the CFM rating and make it very quiet.

Edit:  Found the pictures.

http://www.bottlehead.com/smf/index.php/topic,3046.0.html

[Paul Joppa]

I do not recommend any component rated for less than 85 degrees C, inside any of our amps (except of course the Quickie!).

For what it's worth, in the case of power transformers and semiconductors, I normally design for a nominal internal temperature of 100C, while the parts we use are rated for 150C. For the semiconductors I assume the under-chassis temperature is 60C - but I haven't verified that.

Thanks, Paul, this is very helpful 

What I am wondering is that several of us are using "underrated" (for heat) boutique caps in our amps with great success and over a long period of time (I've been using Mundorf S/O in my Stereomour for a year, for example.  I believe others have even used Jupiter caps, perhaps).   Given your statement about design temps, I should remove my Mundorfs.   This is unlikely to occur, however, because they sound great! 

So what can we do to cool the interior?  I'm thinking a lot more airflow, perhaps even forced?  I don't want to get too complicated but surely there is a nice 12v DC fan that could be added in some reasonable manner to increase airflow.  I really want to try the Mundorfs in the Paramounts without too much worry.

Best,
John

Reading my note again, I may not have been very clear. I meant that the temperature of the wire inside the transformer, and the temperature of the silicon chip inside the transistor, would be kept below 100C. Inside the chassis the air temp is of course much lower - hotter than room temperature, cooler than 100C.

We have been adding ventilation slots in the chassis plates, gradually, as products get revised. This allows thermally-driven airflow, taking it in below the wood base frame and exhausting through the slots.

Cooling air from a fan or other cause does not need to flow very fast, but it does need to flow over the heat sources and then out of the chassis. Components don't sweat, so a fan inside the closed chassis won't cool anything - you need that cross ventilation!

[earwaxxer]

I have Mundorf SIO in my Eros, it is up on spikes increasing ventilation.  I have the same caps in my FP 2 and the base doesn't even have feet on it.  I'll probably put spikes on it too after Paul's post.

I liked the recent picture of a custom Bottlehead product, can't remember which, with a grill at the back of the base and a fan that snuggles up to the grill to increase cooling.  Using a 12V fan on a 9V or 6V supply will decrease the speed, lower the CFM rating and make it very quiet.

Edit:  Found the pictures.

http://www.bottlehead.com/smf/index.php/topic,3046.0.html

Granger - nice build! - 'those pretzels are making me thirsty!' - sorry - couldnt resist the Seinfeld quote!

[John Roman]

Hello Debra,
I've found this site http://humblehomemadehifi.com/ to be most helpful in describing specific qualities of various capacitors. There are also useful recommendations on bypass caps. I hope this helps.
John