Valves, I think I'm starting to understand what the fuss is about.

[Reid Malenfant]

Aye, a FRED They'll do nicely

In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple

[lurcher]

Yes, as said those will be fine. The confusion was that they are not schottky
But I just noticed that RS now stock the Cree high voltage schottky diodes.

http://uk.rs-online.com/web/search/s...duct&R=7027453

I must give them a try.

[HighFidelityGuy]

Aye, a FRED They'll do nicely

In reply to your possible changing of PSU capacitors, if it was me i'd change C1 as that will be subject to the most ripple

Awesome, thanks Mark.
I was thinking the same thing with the caps. C1 had already been swapped for a 220uF so I might use a similar capacity to remove extra ripple over the standard 100uF. It's mainly C2 and C3 I can't decide on. I've heard C3 has a bigger impact on the sound than the other two and that a film cap should work well but that would seriously limit the capacity I could use due to space and cost restrictions. Do you have any recommendations on what caps to use in those positions?

My other idea is to use some smaller film caps (maybe around 3uF) after C3, one for each Channel of the amp as close to point B on the schematic as possible. My idea is that it would provide small energy supply close to the area of demand to smooth things out. What do you think to that idea?

Cheers.

[Reid Malenfant]

I'm not sure i'd change the value of C3 very much if at all It appears that it's just being fed by a resistor & the circuit along with another bleeding resistor looks to be maintaining a fairly stable DC for the front end. You could bypass the 100uf with something of better quality or go the whole hog & regulate the front end with a discrete voltage regulator using a power Mosfet. As i say though, looking at it as is i'd keep to around 100uf.

That leaves you with C1 & 2, as i have already mentioned C1 will have the largest ripple voltage so that to my mind is the one to focus on in the way of chucking capacitance at it. C2 should be worth bypassing as it directly feeds the output stage..

Just remember i know diddly squat about valves though

[Ali Tait]

Dave, just MHO, the Mundorf silver oils are quite good, but I found them a little too much at the top end. If you are prepared to spend a few quid, I'd go for either SCR teflons or AN coppers. These two are the best I've tried so far.

[HighFidelityGuy]

I'm not sure i'd change the value of C3 very much if at all It appears that it's just being fed by a resistor & the circuit along with another bleeding resistor looks to be maintaining a fairly stable DC for the front end. You could bypass the 100uf with something of better quality or go the whole hog & regulate the front end with a discrete voltage regulator using a power Mosfet. As i say though, looking at it as is i'd keep to around 100uf.

That leaves you with C1 & 2, as i have already mentioned C1 will have the largest ripple voltage so that to my mind is the one to focus on in the way of chucking capacitance at it. C2 should be worth bypassing as it directly feeds the output stage..

Just remember i know diddly squat about valves though

Ok, thanks Mark. What would you use for bypassing C2?

Dave, just MHO, the Mundorf silver oils are quite good, but I found them a little too much at the top end. If you are prepared to spend a few quid, I'd go for either SCR teflons or AN coppers. These two are the best I've tried so far.

Thanks Ali. I'm slightly worried about the Silver/Oil's sound too bright. I think some people perceive them that way while others think they sound detailed and airy. I guess it also depends on what they're used in. I decided it was worth the risk as they're pretty much at the top of my price range. I've already spent about the same on components as I did on the amp, so I'd prefer not to go any further. I've heard the standard Mundorf Supreme version sounds similar to the Silver/Oil but a bit less bright, so that's a possibility. I was just a bit worried that with the Kiwame resistors and the the warmer sounding caps that I'd end up too much warmth. I guess I'll have to wait and see if my theory works in practice.

[Reid Malenfant]

Some kind of high voltage Polypropylene or similar film capacitor Depending on what you can fit in i'd go for 0.47uf or bigger if possible. 500V DC rating or higher to be on the safe side

[HighFidelityGuy]

Some kind of high voltage Polypropylene or similar film capacitor Depending on what you can fit in i'd go for 0.47uf or bigger if possible. 500V DC rating or higher to be on the safe side

Thanks Mark. I might look at getting some Solen FastCap's to experiment with bypassing. Or maybe some Evox-Rifa Pulse caps. I'll have to check on the dimensions.

[Ali Tait]

Dave, I've found the Takman resistors very good. Cheap too.

[Reid Malenfant]

I'd go for the Solens out of the two, they are a little more specialised where as the Evox-Rifa are more general purpose as far as i'm aware

I'm sure there are a bucket full more out there though so take your time. Whilst it won't have any audio signal passing directly through it it still one of the most important caps in the amp keeping the voltage on the front end stable.