Never heard of MRS25 before now. I use lots of CMF55's in non critical places, and use them on the signal path in other amps I've got lying around - F2, Aleph MJ (Mini-A with SemiSouth).
It's never a night and day difference, but I think the lower tempco ppm, the better sounding resistor in general - IMO.
Tommorow I go over to a co-workers to try to get another set of baffles built.
It's never a night and day difference, but I think the lower tempco ppm, the better sounding resistor in general - IMO.
Tommorow I go over to a co-workers to try to get another set of baffles built.
indeed zfoils are imo worth the money if you pick and choose the positions you use them in. actually quite a good value tweak imo, better value for money than some power supply mods people dont think twice about. i will be starting with prp, mills 5w and caddock, but may try some futaba and perhaps even tx220z somewhere as time goes on. they are one of the only places to fancy up the f5 given the almost complete lack of capacitors
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I'll have to give that a try. I will listen to it as is for a while longer to get used to the sound. Does upping the bias need a change in value of the source resistors or is it simply a case of raising the voltage across the resistors?
No, if your supply and heatsink is adequate, then it is simply a matter of re-adjusting the pots for a higher current.
But how large are your heatsinks? Can you post a picture or give us the specs? It is essential that you have very good heat transfer from mosfets to heatsink.
No, if your supply and heatsink is adequate, then it is simply a matter of re-adjusting the pots for a higher current.
But how large are your heatsinks? Can you post a picture or give us the specs? It is essential that you have very good heat transfer from mosfets to heatsink.
I have just turned the amp on and will check the temp readings both on the mosfets and heatsinks when its has warmed up. The heatsinks are 300mm wide; 165mm high with 24 fins of 70mm and a base 15mm thick. According to the data sheet in a 300mm hieght there rating is 0.175c/w.
This is true of Mosfets in general.
Like silicon tubes, beside the facts that they do not glow in the dark.
D.
What about R-Core?
Yes, I have a 300VA R-core in my F5. Don't know how different it would sound with a toroid, for me in Japan it was just easier to get that than a toroid. Unfortunately I did not see cores for more than 400VA and I paid 15000 Yen (around 140 euros) for it, custom made with universal primary.
D.
Duh, MRS25 is a BC components (aka Philips) resistor, now Vishay.
(me has many thouza's of MRS25 R's in the entire range, for like 1 $c each. Matching for <0.1% couldn't be cheaper)
Btw, tip : with J74/K170 becoming more expensive and more difficult to buy, sometimes cheaper to look for older Toshiba JFET types.
(me still pay around 50 cents for a J74 BLuei, already fooking expensive imo)
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As I can't find FQA12P20/FQA19N20C mosfets anywhere, I've just ordered a pair of matched IRFP240/IRFP9240 mosfets from Hannes to potentially replace the non matched FQA12P20/FQA19N20C in my original build. I remember from early on in the original F5 thread that the IR p channel was not a preffered option due to a flaw. So my question is, will matched pairs of the IR mosfets be better than non matched Fairchilds?
I built the bog standard F5 as per the PASS instructions so by a pair I meant 2 x N and similarly 2 x P mosfets for a stereo amp. I had always read/assumed that the 2 x N's had to be matched and the same for the 2 x P's. I seem to remember that it was a bloke called Nelson Pass who opted against the IR P channels as they introduced an element of distortion (despite them being in the original schematic). I had always intended to go for matched mosfets after the initial build but this was so good in the first place that I haven't really felt the need. But things can always get better...
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