SPEC 1 Frequency Response Guidance Required
- Thread starter xlbee
- Start date
not intended for you to do, but you couild verify all the spec1 spec's against what is published.
my sneaking suspicion is a design flaw, interaction between a high z source volume control in mid position and the input capacitance of one or both of the gain stages.
maybe this is why they switched to jfets for the pre-amp gain stage after the vol in sx-x50/80 series and sa integrated.
have to do further sims&/or measurements to pin it down to where/why, what to do to fix.
i doubt it is a wiring flaw, but would hope it would be an easy fix too but i hold my breathe.
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sounds like you have it covered, sorry i did not read your tests results before commenting.
could do a freq response with gain flat and change input attenuator settings
vary balance and measure freq response at different settings
i never did understand the dual stage volume pot design reasoning, esp with +/- 49V rails = huge amount to dynamic range, which is really not needed for a nominal ~1 V Full scale o/p signal to drive a power amp..
could do a freq response with gain flat and change input attenuator settings
vary balance and measure freq response at different settings
i never did understand the dual stage volume pot design reasoning, esp with +/- 49V rails = huge amount to dynamic range, which is really not needed for a nominal ~1 V Full scale o/p signal to drive a power amp..
that's is okay, just trying to help out with some ideas.
your tests match, so we have confirmed normal spec1 behavior.
one thing i could do is test my sx-950 pre-amp freq resp vs volume setting, i will sim it in ltspice, i recall i have that design captured as i was playing with it some time ago to find a replacement for 2sk30aw/2sk117 used in that design.
your tests match, so we have confirmed normal spec1 behavior.
one thing i could do is test my sx-950 pre-amp freq resp vs volume setting, i will sim it in ltspice, i recall i have that design captured as i was playing with it some time ago to find a replacement for 2sk30aw/2sk117 used in that design.
I really appreciate you validating my findings Lee!!!!!!!!!!
Mine is still open on the bench but I just have to get the time to pull the handles, knobs and front panel off so I can remove the one board that will allow access to the volume control. Fingers crossed I will get time this week...
Agreed - what's up with that?
What file type are you trying to upload? You can send them my way and if fate is on my side maybe I can upload them.
