I'm using a Blue Alps 100K. I have no pops...
I have a little noise but only where I'm living. At my friends location
there is zero. weird..
/Michael
Hi Felipe...
I have tried several different resistors, as grid stopper, grid leak resistor and now I'm using Shinkoh as grid stopper.
This is one of the best "upgrade" I have done for a while. Much warmer, and
more dynamic compared to the following.
KOA Spear (Carbon). Too Dull.
KOA Spear (MOX). Too noisy, a little to much on the Top.
Takman REX (Carbon). Very nice, both still do polite.
TakMan REY (Metal). Indeed very nice. A little too thin but I was quite satisfied.
Shinkoh (tantalum). Very musical, very open, and very warm (My favorite).
This gave me so much in 4P1L. Tweaking the grid stopper was worth the
time and price.. Do not save on the budget here.
/Michael
You could try NO grid stopper at all (or maybe just a ferrite bead close to the pin, make sure it doesn't rattle around).
I know very well the sinkhos, I made the Shallco attenuator with them but my advice isn't to use in all positions, for grid leak resistor try Mills 12W. In my setup the ladder without grid leak resistor sounds better possibly have to try 68K.
It is wrong to use a switched attenuator without a fixed grid leak resistor: the contacts may be bouncy or even fail after some time. In this case the grid is no longer ground referenced: you will get pops or even a tube and power supply meltdown.
Also, the grid leak's value should be at least 5 times bigger than the potentiometer/attenuator, or else you will change too much the attenuator's transfer law and its impedance. When you use a 47K resistor in parallel with half of a logarithmic 100K pot, as you do, you will get a weird 32K equivalent potentiometer with a different transfer law...
Hi.
I'm only using shinkou as grid stopper, so far. I know about the Mills
using them as cathode resistor, and very happy with them.
We're am living, I have a old house, I have more noise on the main, and
I have lower noise when using the shinkoh, which is very nice.
I also had read, not to use them in every position, but very pleased with them in the signal path.
Again we're all different, so our individual taste is quite different..
/Michael
Hi
I'm using Amtrans as grid stopper and I'm pleased.
You're right fortunately each person & system is different.
Felipe
I'm using Amtrans as grid stopper and I'm pleased.
You're right fortunately each person & system is different.
Felipe
Thanks for the beautiful curves.
The +2V trace looks the most linear. Is +2V workable in a preamp? It seems like -8V is the standard?
What do you think of using step-up transformer as a volume control in front of 4p1l whit 10K load,
like the PVA from electra print. Maybe 1:2 or 1:4 ??? Any thought?
like the PVA from electra print. Maybe 1:2 or 1:4 ??? Any thought?
Subscribing to this interesting thread.
Linearity is not seen from how straight the trace looks like. It's from how equal the spacing between each trace is. 4P1L is beautifully linear because if you draw a straight horizontal line crossing all traces, the crossing points are evenly spaced from each other.
Also, positive grid voltage (+2v as you mentioned) would also mean you have grid current and as such, lowers the input impedance greatly which is usually something we want to avoid.
Hi.
I have build a couple of 4P1L for my friends, but this morning, my
friend and I have those "microphonic pops" from both our amps.
After haven't seen any logic , In behavior , I just did the old trick
replaced the cathode Mill MRA-12, in both amps.
With a pair of Ohmite non magnetic 7w in instead and now
the 4P1Ls is playing, but for how long time ??
These two amps are nearly playing 24/7 , so are there someone out
their with extreme usage like me, that could recommend STABLE cathode resistor
, because I'm getting tired of flushing my money in the toilet.
I'm on the 8 ohm first version, just in case it should matter...
PS! This is very weird. The two Mills from my Friends Amp was measured
at exactly 8.2 Ohm , which I replace with two Ohmite with exactly 8.2 ohm,
this solved the problems with those "extreme pops".
/Thanks Michael.
I have build a couple of 4P1L for my friends, but this morning, my
friend and I have those "microphonic pops" from both our amps.
After haven't seen any logic , In behavior , I just did the old trick
replaced the cathode Mill MRA-12, in both amps.
With a pair of Ohmite non magnetic 7w in instead and now
the 4P1Ls is playing, but for how long time ??
These two amps are nearly playing 24/7 , so are there someone out
their with extreme usage like me, that could recommend STABLE cathode resistor
, because I'm getting tired of flushing my money in the toilet.
I'm on the 8 ohm first version, just in case it should matter...
PS! This is very weird. The two Mills from my Friends Amp was measured
at exactly 8.2 Ohm , which I replace with two Ohmite with exactly 8.2 ohm,
this solved the problems with those "extreme pops".
/Thanks Michael.
Funny thing, in the end it was a grounding problem not the resistors! 🙂
Idont believe you had a resistor problem here Michael, but I may also be wrong.
Idont believe you had a resistor problem here Michael, but I may also be wrong.
If these are for filament bias, my recommendation would be TWICE the wattage - these resistors get hot. I would use some big vitreous enamel ones. My 4P1L PSE amp is on 24/7 and has been for a year and a half, and no pops.