howabout that Watford game,
ruffrecords said:The pad is in the correct position as is the phantom power. You can also add a phase change switch here if you want. Jensen has an app note that shows how to do these three at the input:
http://www.jensentransformers.com/as/as016.pdf
ruffrecords said:The gain control will work where you have it. It is not ideal but in a one tube mic pre there is not much alternative. You just need to make sure the leads to and from it are as short as possible ans screened. This is a high impedance part of the circuit and is susceptible to interference. It does need to be wired as a pot so a connection to ground is needed from the bottom of the pot.
ruffrecords said:You can have an output pot on the output of a mu follower stage like this but normally only if it is feeding another tube stage. It will not drive a low impedance pot and a following transformer. If you want an output pot so you can drive the tube harder with the gain pot and reduce the output with the output pot then I would recommend using a 5K output pot. The 6922 SRPP/mu follower will drive this to quite high levels producing some nice smooth tube distortion. The output impedance of this pot should be no more than about 1.5K. If you want a transformer balanced output I would recommend using a 10K:10K type.
CJ said:howabout that Watford game,
ruffrecords said:If you want a transformer balanced output I would recommend using a 10K:10K type.
dirtyhanfri said:ruffrecords said:If you want a transformer balanced output I would recommend using a 10K:10K type.
Just noticed this, my output transformer is 2.4k:2.4k, so I suppose I need to get another transformer...
dirtyhanfri said:It's alive! ;D
It passes audio, no big hums or noises, now I'm gonna work on the Pad, HPF & Phantom to make a real mic pre.
EDIT: as far as me & a sine sweep in fuzzmeasure can tell there's no difference turning the "character" 10k pot, just a 3db drop in gain
ruffrecords said:You can have an output pot on the output of a mu follower stage like this but normally only if it is feeding another tube stage. It will not drive a low impedance pot and a following transformer. If you want an output pot so you can drive the tube harder with the gain pot and reduce the output with the output pot then I would recommend using a 5K output pot. The 6922 SRPP/mu follower will drive this to quite high levels producing some nice smooth tube distortion. The output impedance of this pot should be no more than about 1.5K. If you want a transformer balanced output I would recommend using a 10K:10K type.
ruffrecords said:It will depend on how hard you drive it. At +4dBu output the distortion will be quite small. Whack it harder so it outputs +15dBu or more and you should start to hear some serious tube sound in the SRPP position.
dirtyhanfri said:This made me think... What about putting a second tube stage after after the pot and before the output transformer?
I think that could give me the gain I'm missing right now, and the "character pot" would have more sense there, where I can get harder into the tube. 5k is fine for the pot before the second tube stage?
And, for the output transformer, 2k4:2k4 is still fine?
ruffrecords said:Anything up to 100K would be fine. On the other hand, you might want to load the first stage with 5K so as to ensure that it can also add some tube tone as well.
dirtyhanfri said:ruffrecords said:Anything up to 100K would be fine. On the other hand, you might want to load the first stage with 5K so as to ensure that it can also add some tube tone as well.
I don't fully understand this, what you mean by load the first stage?
ruffrecords said:To avoid the scratchiness of a pot with dc you could retain the 10K and place a pot (or a switched resistor) with a series cap across it to alter the ac conditions of the circuit. Sounds like quite a fun experiment to me.
dirtyhanfri said:Ok, thanks for the explanation.
Well, I got it working, With lots of gain. I'd like to work a bit more on the attenuator before the first tube, it's giving me only -6 db's, I want to get something like -18 in six steps.
ruffrecords said:To avoid the scratchiness of a pot with dc you could retain the 10K and place a pot (or a switched resistor) with a series cap across it to alter the ac conditions of the circuit. Sounds like quite a fun experiment to me.
I'll try this; If I understand right I must keep the 10k resistor and connect the pot-cap in parallel with the resistor? Which value and V rating would be fine for the cap?
dirtyhanfri said:I tried it and the result is no sound :-\
JoshuaUnitt said:Basically I'm hoping to put together a pedal that features a Fender-derived tone stack, with tube makeup gain, and possibly a choice of balanced or unbalanced out (so it can be used in a pedal chain/before an amp, or as a tube direct box with EQ).
So my question is, how reasonable would it be to drive a passive tone circuit like the standard 3-band Fender amp EQ with a cathode follower, and follow the tone circuit with your mu-follower board? Or would i see more benefit from converting the mu-follower to an SRPP?
skeeler87 said:Hey Guys!
So I'm building a 2ch pultec eq with the PMEQP1A Mk2 boards and I'm thinking of using this circuit for make up gain. However, I've never worked with tubes before. Do you guys think this would be a good first tube project for someone totally inexperienced with tubes?
Thanks!
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