94Tremoverb said:The second one *is* better, but the first is perfectly adequate for the job.
94Tremoverb said:The second one *is* better, but the first is perfectly adequate for the job.
fluff191 said:94Tremoverb said:The second one *is* better, but the first is perfectly adequate for the job.
+1
I used the Bourns pot on my Recto.
94Tremoverb said:I forgot to say - if you don't use the Slave output jack, there's a far better way of doing this that doesn't require either of those pots - turn the Slave level pot into a bias control... then you can get at it from the outside of the amp. I also added bias sensing resistors and connected them to the Slave jack itself, so by plugging a meter with a 1/4" plug on the cable in there, I can get a direct bias reading.
The Slave pot is 10K, so if you use it and a 12K resistor in series to replace the original 22K ground resistor in the bias circuit, you get the stock value when it's full up and hotter as you turn it down - but not *too* hot (apart from in Bold/Diode), and it's also fail-safe since like all bias control methods that use the ground resistor, if the pot goes bad the bias voltage goes up, not to zero, which is always the right way to do it.
Thank you, I was quite proud of it .fluff191 said:**** that is a good idea.
No - what you do is fit either a 1-ohm 1% resistor to each tube base the standard way (what I did, since I have plenty of them) then parallel the tube cathode ends, giving an effective .25 ohms in total, or - if you can find a 1% one, you could use a single .25-ohm resistor - so you get the average reading from all four tubes, and then connect that to the jack tip contact. The worst that happens if the plug shorts the two contacts as it goes in, is that it momentarily reverts to the stock situation where the cathodes are grounded anyway, so no harm can occur.With the Bias voltage going to the jack, you would totally need to turn the amp off then plug in the dummy jack and then turn the amp back on right? Otherwise you risk shorting something? Just curious.
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