RIFA
I am fortunate to have a small stock of RIFA PFE 210 film and foil polystyrenes
Up to 220nF.
They are about 25 years old so I thought that the stability would be compromised. I had them measured by a capacitor manuafcturer and the capacitance was spot on (within 1% which is the tol I have)!
Amazing.
I am saving these for the most high end amplifiers I have both as coupling and decoupling usage.
Sigurd
john curl said:
I am fortunate to have a small stock of RIFA PFE 210 film and foil polystyrenes
Up to 220nF. They are about 25 years old so I thought that the stability would be compromised. I had them measured by a capacitor manuafcturer and the capacitance was spot on (within 1% which is the tol I have)!
Amazing.
I am saving these for the most high end amplifiers I have both as coupling and decoupling usage.
Sigurd
John,
WIMA MKP4 and MKP10 are very good industrial capacitors! No doubt about that. I use them for decoupling sometimes. The RIFA PHE450 and 426 are similarly excellent industrial caps! Prices for these caps are actually at bargain levels.
Phe 426 is available up to 27u and these I will use in my next line amplifier whose PCBs will arrive in two weeks.
But, for an input cap, there are of course much better sounding caps. No doubt about that either.
They are often MUCH bigger, though, and often made for hundreds of volts or for loudspeaker crossovers. Who needs a bear can sized 10u input cap designed for 800V usage in solid stahe amplifiers?
Personally, I do like ike the Mundorf PP caps and use them for loudspeaker cross overs and even as outp caps for my modded CD player.
Rel RT caps I will soon try as I got 25 pcs last week.
BTW, John,
have you noticed any sonical differences between the 200V and 600V Rel RT caps?
Sigurd
WIMA MKP4 and MKP10 are very good industrial capacitors! No doubt about that. I use them for decoupling sometimes. The RIFA PHE450 and 426 are similarly excellent industrial caps! Prices for these caps are actually at bargain levels.
Phe 426 is available up to 27u and these I will use in my next line amplifier whose PCBs will arrive in two weeks.
But, for an input cap, there are of course much better sounding caps. No doubt about that either.
They are often MUCH bigger, though, and often made for hundreds of volts or for loudspeaker crossovers. Who needs a bear can sized 10u input cap designed for 800V usage in solid stahe amplifiers?
Personally, I do like ike the Mundorf PP caps and use them for loudspeaker cross overs and even as outp caps for my modded CD player.
Rel RT caps I will soon try as I got 25 pcs last week.
BTW, John,
have you noticed any sonical differences between the 200V and 600V Rel RT caps?
Sigurd
john curl said:
PMA said:
PMA,
MKP4 and MKP10 are PP caps.
The polyester series is called MKS.
I once used (grren they were) WIMA polyester caps in a loudspeaker cross over, and will not use polyester anymore. Replacing these polyester caps with PP caps increased sonics a level or two.
Why not give the WIMA polyester caps a shot and compare to PP caps?
SIgurd
I am not saying that polyester is as good as polypropylene. It is not. In case the Wima was PP, it should not have been a source of any sound problem.
My main question is - does MikeW use the oscilloscope? Did he measure transient response for whole range of output voltage? Did he check amp stability with complex load and speaker load? If not, then we speak about nothing.
My main question is - does MikeW use the oscilloscope? Did he measure transient response for whole range of output voltage? Did he check amp stability with complex load and speaker load? If not, then we speak about nothing.
PMA said:
I do have a scope. I did not do a whole range. I have checked it with different output loads. At the moment no oscillations.
john curl said:
John, I do thank you for your time. I have place an order for .1 uf REL RT caps. Hopefully they will be here by the end of the week. Listening will continue to get a baseline before the cap change.
MikeW said:
Of which at least 5 or 6mA comes from the JFETs, leaving something in the mid-teens as bias for the cascode/drive for the outputs. Hmmm. Not that you'll want to nuts like I did on drive current, but it wouldn't hurt to have a little more. There won't be a one to one correspondence between your circuit and mine, but distortion dropped quickly as I raised the driver stage bias current in the GR-25. If you run out of other things to try, you could tag a pot or another resistor in series with the 220 Ohm resistors and see if a little bit more bias helps.
Grey
Difficult to say from this distance. There are lots of things you could try, but most of the ones I would suggest would tend to lead you more towards a GR-25 than a JC-3, and I'm reluctant to mess with your basic theme.
Can you post a current schematic with a few scrawled notations as to voltages and currents?
Grey
P.S.: After a brief detour into phono stage land, I'm going to whip up a second set of PCBs and try bipolars in some of the in-between positions in the GR-25. In a sense, I'm going to meet you half-way.
Can you post a current schematic with a few scrawled notations as to voltages and currents?
Grey
P.S.: After a brief detour into phono stage land, I'm going to whip up a second set of PCBs and try bipolars in some of the in-between positions in the GR-25. In a sense, I'm going to meet you half-way.
With the exception of one scared young fella dragged home by a stepdaughter, Elwood is the only member of this site that I've met face to face. That meeting occurred back around 1971 or so and I count him as a friend...friend in this case meaning someone who gets along with you in spite of your personality deficits. Between the two of us, we've managed to keep Krispy Kreme and Bacardi in business, not to mention Gibson, Fender, Ampeg...
Mike,
The aforementioned kids will keep me pegged to the ground here. What Elwood's schedule might be, I can't say, but he's "good people" as the expression goes, and a whole lot better company than I am.
Besides, the GR-25s aren't easily portable.
There's a perfectly good reason that I avoid Myrtle Beach. Well, perhaps avoid is the wrong word. There are few things in life that are as intriguing to me as chasing women...and Myrtle Beach owes its existence to the invention of the bikini. The problem is that the young ladies in question tend to turn, place their hands on their hips, and indignantly inform me that I'm old enough to be their father.
To which I am forced to reply, "Hell, honey, have you had your DNA checked? I might very well be your father!"
Grey
Mike,
The aforementioned kids will keep me pegged to the ground here. What Elwood's schedule might be, I can't say, but he's "good people" as the expression goes, and a whole lot better company than I am.
Besides, the GR-25s aren't easily portable.
There's a perfectly good reason that I avoid Myrtle Beach. Well, perhaps avoid is the wrong word. There are few things in life that are as intriguing to me as chasing women...and Myrtle Beach owes its existence to the invention of the bikini. The problem is that the young ladies in question tend to turn, place their hands on their hips, and indignantly inform me that I'm old enough to be their father.
To which I am forced to reply, "Hell, honey, have you had your DNA checked? I might very well be your father!"
Grey