switchable gain is possible.
One should check that stability margins do not change adversely at some of the options.
Switching a gain stage to unity gain gives no useful advantage. It would be better to either switch select to a buffer stage or bypass and go completely passive if the source can drive the resulting capacitances.
Nope sorry Farooq. It's got to be a 5K dual linear pot. A log pot will not work.
Thanks Carl...I am still in collecting parts phase...found a good quality pot but it is a log type.
5k pot
Page 33 of DS book...Self on Audio.. made me think otherwise but I might be missing something.
"It can be readily shown by simple algebra that the control track resistance now has no effect on the gain law, and hence the channel balance of such a system depends only on the mechanical alignment of the two halves of a dual linear pot."
Page 33 of DS book...Self on Audio.. made me think otherwise but I might be missing something.
"It can be readily shown by simple algebra that the control track resistance now has no effect on the gain law, and hence the channel balance of such a system depends only on the mechanical alignment of the two halves of a dual linear pot."
I think that refers to the fact that the pot value doesn't matter (1k or 5k or 10k or 50k or whatever). The law itself must be linear.
They ran too hot to touch. I replaced them with mbr1060's and the psu was fine. No clue at all what was wrong with the mbr1045's.
Carl,
Give me some advice, I built the self preamp It sounds great but i am plagued by an intermittent loud noise, sounds like static, maybe its a grounding issue? but i can find it.
I've traced it back to the i/o board, but figure out if its a bad relay or short somewhere,
Whats the grounding scheme? Are the the ca's and xlr grounded thru the chassis, i've installed it in a wood box?
thanks,
david
Give me some advice, I built the self preamp It sounds great but i am plagued by an intermittent loud noise, sounds like static, maybe its a grounding issue? but i can find it.
I've traced it back to the i/o board, but figure out if its a bad relay or short somewhere,
Whats the grounding scheme? Are the the ca's and xlr grounded thru the chassis, i've installed it in a wood box?
thanks,
david
David,
The first thing that I would do is look at bottom side of the IO board for 'cold' or bad solder joints under a well it magnifying lens. And then just for good practice touch them all with a clean and hot solder pencil tip. That's always my first step in troubleshooting such problems.
I made some measurements on the tone control of the Elektor 2012 amplifier. I was a bit surprised because the impedances were extremely low in the 1k pot design. I knew that, but it was so low that I was surprised.
Z = 110 Ohm (@ 20khz), full boost
Z = 230 Ohm (@ 20khz), linear
Z = 330 Ohm (@ 20khz), full cut
A small OP that can never drive without having extreme distortions. The split-drive baxandal does not help either. What do you think?
Z = 110 Ohm (@ 20khz), full boost
Z = 230 Ohm (@ 20khz), linear
Z = 330 Ohm (@ 20khz), full cut
A small OP that can never drive without having extreme distortions. The split-drive baxandal does not help either. What do you think?
Thank you, Carl and Douglas, for this project!