I have been working on getting my Caruso preamps and head working and I've got everything connected and taking feedback. Right now I am at 26db of feedback on both channels using a QSC USA 850 amp. I am getting a big dip of around -9 at 7k and a peak at 12k of +4, the rest of the highs from 6k up all have varying -2, -1. This is all measured against my NAB disc. When I try to fix with parametric eq (Pro-q) I can get it flatter but the corrected frequencies sound noticeable/bad.
Does anyone have any suggestions or clues where to check?
Today I am trying shorter feedback cables and a new cutting stylus. I have tried a couple different amps with no success.
Caruso frequency response
Moderators: piaptk, tragwag, Steve E., Aussie0zborn
Re: Caruso frequency response
Mine isn't here yet, but the first thing I would be doing is a quick bode plot of both the feedback compensator (gain and phase from feedback input to power amp drive output with no modulation), and a plot of modulation input to firstly the input of the drive pot (which should look basically IRIAA like) and secondly modulation input to drive output with the drive output.
All this with the head and amp disconnected, this feels like an electronics problem, up there I would be suspicious of the feedback compensator gain being too low at high frequency, those feel like mechanical resonances not being corrected.
You did note Flos notes on his schematic as to what should or should not be fitted for the various heads?
Do you have access to something like an AP test set or DScope? Failing that, this can be done with a soundcard, but it takes a little fiddling.
Oh a reminder, when fiddling with the electronics on this sort of thing always turn all the pots to zero before making a change, that way when you power it back up at it takes off, your head has some chance of surviving the experience. A pair of judiciously placed back to back diodes during initial testing are probably a good idea as a power limiter (maybe across the output opamp feedback resistor?).
Good luck, hopefully it is just electronics.
Regards, Dan.
All this with the head and amp disconnected, this feels like an electronics problem, up there I would be suspicious of the feedback compensator gain being too low at high frequency, those feel like mechanical resonances not being corrected.
You did note Flos notes on his schematic as to what should or should not be fitted for the various heads?
Do you have access to something like an AP test set or DScope? Failing that, this can be done with a soundcard, but it takes a little fiddling.
Oh a reminder, when fiddling with the electronics on this sort of thing always turn all the pots to zero before making a change, that way when you power it back up at it takes off, your head has some chance of surviving the experience. A pair of judiciously placed back to back diodes during initial testing are probably a good idea as a power limiter (maybe across the output opamp feedback resistor?).
Good luck, hopefully it is just electronics.
Regards, Dan.