mikeyB

Re: Roger Mayer RM57 build?
« Reply #320 on: February 02, 2019, 11:20:26 AM »
Do the FETs have to be matched? That is the audio FET and the meter FET.
Great sounding unit by the way
making better music!


RuudNL

Re: Roger Mayer RM57 build?
« Reply #321 on: February 03, 2019, 04:12:42 AM »
Yes, to obtain good stereo tracking, you should match the Fets. (Since there is no way to adjust the tracking.)
In my case, tracking is better than 0.5 dB over 20 dB gain reduction.
I found two pairs out of 20 Fets.
The meter tracking circuit should use Fets that have the same characterictic as the attenuator Fets.
So in an ideal case a 'matched quad'.  (Although a small difference isn't that critical in the meter circuit, but try to match them as good as you can.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

mikeyB

Re: Roger Mayer RM57 build?
« Reply #322 on: February 03, 2019, 04:27:10 PM »
Thanks RuudNL
making better music!

RuudNL

Re: Roger Mayer RM57 build?
« Reply #323 on: February 04, 2019, 03:24:10 PM »
If there is a small tracking error, you can cheat a little and vary the value of R1 (18K) a little.
This way you can optimize small tracking errors!
There is a solution for every problem!

http://www.vansteenisaudio.nl

mikeyB

Re: Roger Mayer RM57 build?
« Reply #324 on: February 09, 2019, 10:44:35 AM »
Thankyou,
Probably my next project - I've got an albums worth of drums to squash!
making better music!


 

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