[viggen]

So I've had this amp, a Greatec µVAC, since 2007.  But, sometime around 2010, I damaged it and it has been repaired multiple times.  No tech has ever fully repaired it.  That is until I found this this tech, Andy, local to me near Buena Park CA:

https://www.ebay.com/usr/jrtkyu?_trksid=p2047675.m3561.l2559

Now, the amp is fully functional and is sounding better than ever.  During the repair process, Andy told me he replaced two capacitors.  I asked which what type of caps he was installing and whether I had a choice.  He didn't seem to be the type to think caps affect sound?  But, he installed what looks like Nichicon VX 47uf 63v.



I can't complain about the sound but it seems to be a lower grade cap in audio terms?  But, main purpose of this thread is to explore possibilities regarding this capacitor:



So, my question or problem is, should I replace this capacitor?  It seems to be used in electric guitars.  And, size and specs seem to be an issue.  I don't see any audio grade capacitors that can fit in this amp that is equal or greater to this cap's specs:



Based on the image above, I think the spec reads 100uf 16v and is about an inch long and half an inch in diameter.

Can experts here please shed light as to whether I should replace this capacitor and, if yes, with what?

My goal?  I love the sound.  It's mildly warm of neutral with satisfying listen all day smoothness.  It plays very well with my high efficiency Altec Carmel which could be too airy or studio monitor-ish with other more audiophile type amps.   So, my goals is I hope this amp could gain some more audiophile attributes without losing its own character.

Also, could someone please explain to me the functional difference between the Nichichon and F&T caps in this amp?

[FullRangeMan]

Congratulations always nice to hear a good news.
my question or problem is, should I replace this capacitor?
Iam not expert in any way and I dont see any reason you should replace these good caps, if they have good sound and are cheap what one could ask more for?
But I have hear good talk on EPCOS(TDK) and Black Gate (audiophile price).
could someone please explain to me the functional difference between the Nichichon and F&T caps in this amp?
Do you posted an schematic?

[viggen]

Here's one for the prototype version.  The tech used it fine:

[FullRangeMan]

This is a nice small amp, certainly it will benefit alot with a 16 ohms FR driver as in the 1930s, both caps serve the output tube/OPT in the usual way, maybe the C2 can be replaced by a choke if Iam understanding right. 

[viggen]

really?  my carmels are 16ohm though they are not fr.

[SET Man]

Hey!

  OK, here's what I can see in that amp to answer your questions... the 100uf 160V is likely in the power supply high voltage B+ line and the 47uf 63V are in output tube bias caps.
   
     Yes changing those caps above will change the sound. But of all the caps in there, the ones that will have the most effect on the sound are those red WIMA caps, I think they are coupling caps which are directly in the signal path between input tube and output tube. According to the schematic in the link they are 100n or 0.1uf. There are lots of caps out there and each have their own unique sound even though they are the same value. The question is... what are you looking for? More transparency?

   But! If you like how the amp sound now, just enjoy it! Be careful what you wish for, sometime more expensive caps won't sound good in your amp. Sometime super transparency in audio is over rated. Most recordings out there are thin and bright so a little warm in audio is not a bad thing.



     

   

[FullRangeMan]

really?  my carmels are 16ohm though they are not fr.

Great, the OPT must be 15 ohms.

[viggen]

Hey!

  OK, here's what I can see in that amp to answer your questions... the 100uf 160V is likely in the power supply high voltage B+ line and the 47uf 63V are in output tube bias caps.
   
     Yes changing those caps above will change the sound. But of all the caps in there, the ones that will have the most effect on the sound are those red WIMA caps, I think they are coupling caps which are directly in the signal path between input tube and output tube. According to the schematic in the link they are 100n or 0.1uf. There are lots of caps out there and each have their own unique sound even though they are the same value. The question is... what are you looking for? More transparency?

   But! If you like how the amp sound now, just enjoy it! Be careful what you wish for, sometime more expensive caps won't sound good in your amp. Sometime super transparency in audio is over rated. Most recordings out there are thin and bright so a little warm in audio is not a bad thing.

Thanks for your info!

I don't really want to change the amp's character but was wondering whether there were any obvious bottlenecks based on the capacitors used.  The red WIMA caps, as I understand it, seems to be high quality and is probably not a bottleneck?  My suspicion is the power supply cap (the F&T one) is a possible bottleneck.  I'd love to fit a Duelund or try a Mundorf.  But, they seem too big to fit in the amp.

[viggen]

Great, the OPT must be 15 ohms.

According to the spec, it's wired for either 4 or 8?

[FullRangeMan]

According to the spec, it's wired for either 4 or 8?

Correct, the schematic also say it.
At this low power 0.8W 8Ω speakers draw much power.
If its working well no need change to a 16Ω OPT IMO.

[Ericus Rex]

Hmmm. The 100uF/160V is a polar electrolytic.  The only Mundorf option is:

https://www.partsconnexion.com/MUNDORF-80611.html

I don't see that Dueland makes an electrolytic cap.  I'll go against the grain here and say that, assuming this is a filter cap in the power supply, I doubt you'll hear any difference by swapping this one out.

All the hubbub about the 'sound of caps' (mostly-) involves film coupling caps (the 100nF in your schematic). I would guess these are the rted Wimas in your pics. Wimas are very respectable caps.  You will hear a difference if you swap these out for more expensive caps but you'll have to be very careful in picking out caps that will fit in this chassis. Boutique caps be large.

If you want to maximize your cap-upgrade, you might think about also replacing C2 in your schematic with a good audio-grade electrolytic cap, something like the Elna Silmic II perhaps (https://www.partsconnexion.com/ELNA-72705.html). Thankfully, these types of caps aren't expensive.

Let us know your results.

[viggen]

Thanks Eric!

Looks like I am in a good place regarding caps. 

I will concentrate on other aspects such as replacing the captive power cable.

[FullRangeMan]

Thanks Eric!

Looks like I am in a good place regarding caps. 

I will concentrate on other aspects such as replacing the captive power cable.

Dont change power cable IMO,
an IEC power connector add 9 contact points.

[viggen]

technically these don't have captive cords... they have these connectors i've not seen before.  it's rather chunky.

[Speedskater]

Replacing an AC power cord won't change the audio output and if done incorrectly it could be dangerous!
Replacing capacitors with other of the same value and type (film for film or electrolytic for electrolytic) won't change the audio output.

[FullRangeMan]

technically these don't have captive cords... they have these connectors i've not seen before.  it's rather chunky.

Seems to me these are reliable connectors,
looks your builder knew what he was doing.
How are the pins from these connectors?