and why the noise almost goes away with the stereo hifi preamp driving the output
must be something to do with going from 0/+ supply to symmetric +/- supply
looking at Nelson's B1 buffer, could this be the reason why he 'constructed' a pseudo midpoint for the jfet's grid to ground resistors
tried adjusting drain and source resistors
15ohm source res stays in, no doubt
not sure what kind it is
old and beige colored, so I suspect its a carbon film, 1/2W or something
tried a metal film, but didnt sound so nice
(signal resistors are metal films)
Drain resistor is lowered a bit, from 1K5 to about 1K2 or 1K3
measured +7.18V over drain res, and -82mv over the source res
dont know if those are the best values, but sounds good
15ohm source res stays in, no doubt
not sure what kind it is
old and beige colored, so I suspect its a carbon film, 1/2W or something
tried a metal film, but didnt sound so nice
(signal resistors are metal films)
Drain resistor is lowered a bit, from 1K5 to about 1K2 or 1K3
measured +7.18V over drain res, and -82mv over the source res
dont know if those are the best values, but sounds good
15ohm source res stays in
Drain resistor is lowered a bit, from 1K5 to about 1K2 or 1K3
nope, drain res is still 1K5
well, actually 1K6, since its 2 paralel 3K2
I removed series resistors from the power supply
and thats it
at input, instead of 1M to ground I have 850K
will try increasing input/gate series resistor
ups, been busy
yes its snerring hum
my present setup have variable attenuation on final output, and takes away most of it(its a stereo preamp buffer)
at 12 o'clock nothing, but above that it begins be audible, and gets really aggressive when turned up fully
almost no hiss, and in general very silent right now
weird setup btw
bass guitar--compressor--jfet boz
then devides into two channels
one channel, jfet boz--headamp--stereo pre--poweramp--mid/tweeter
second channel, jfet boz--stereo pre--poweramp--woofer
inserting the headamp gives me a lot more control, and a picture of how it ought to work
I think it will work very well when Im able to control every gainstage in both channels
its getting closer
yes its snerring hum
my present setup have variable attenuation on final output, and takes away most of it(its a stereo preamp buffer)
at 12 o'clock nothing, but above that it begins be audible, and gets really aggressive when turned up fully
almost no hiss, and in general very silent right now
weird setup btw
bass guitar--compressor--jfet boz
then devides into two channels
one channel, jfet boz--headamp--stereo pre--poweramp--mid/tweeter
second channel, jfet boz--stereo pre--poweramp--woofer
inserting the headamp gives me a lot more control, and a picture of how it ought to work
I think it will work very well when Im able to control every gainstage in both channels
its getting closer
btw
I have tried almost all possible configurations with the effect units I have, and some sounded pretty weird
one acted like a synth, another like pure distortion, and others sounded just muffled and phased
tells it not so simple at all with effect 'pedals
I only use compressor pedal unit right now
would like to do without, but right now its not possible
but maybe later
I have tried almost all possible configurations with the effect units I have, and some sounded pretty weird
one acted like a synth, another like pure distortion, and others sounded just muffled and phased
tells it not so simple at all with effect 'pedals
I only use compressor pedal unit right now
would like to do without, but right now its not possible
but maybe later
For the hum situation, I would try an isolated input jack, input signal wire shielded from jack to jfet input, but shield terminated only at the signal ground directly at your jfet's source resistor ground. That is the most direct route for return path to your instrument. Adding a bypass cap across the source resistor may help. Check all other signal grounding points in your preamp are star grounded or bussed onto a heavy gauge copper grounding wire in your cabinet. You may need to add shielding metal panels in future if you are picking up ambient EMF. Your outputs are splitting to two different stereo preamps? You may have a ground loop issue there too. let me know if they are separate preamps powered on AC, DC etc. one output may need to be isolated to break ground loops on outputs.
hey, will try bypass cap on source res
note, its not the channel splitting
hums also with only one channel
but its a proto built on a piece of plywood
the other evening I could hear faint spanish radio
but was gone again just by a simple off/on switching
seems to be a one time only
but I might have a faulty plug on my bass
its gets noisy when not touching the strings
note, its not the channel splitting
hums also with only one channel
but its a proto built on a piece of plywood
the other evening I could hear faint spanish radio
but was gone again just by a simple off/on switching
seems to be a one time only
but I might have a faulty plug on my bass
its gets noisy when not touching the strings
hey, will try bypass cap on source res
tried 22uf el cap
sounded ok, but a bit muffled, or maybe more like phased
then a 1.0uf film cap
sounded more open, but nervous
then 2.5uf
bang, sounds just right, very smooth
great 'egalite', responsive and tuneful, tight bass
I would say spot on
2.2uf works ok too
actually, in some way even better
compressor sounds ok again
for some reason my compressor didnt work so well with 2.5uf
could be because it was a different type
also tried a 3.3uf orange colored cap
didnt last one minute
should I have a selector option, it would switch between 2.2uf and 2.5uf
worth the trouble ? yeah, its enough to make that little important difference
might be it actually affects the tuning pitch just a bit, but enough for 'certain occations'
anyway, a switch would at least make it easier to test different caps
well, enough of that
working on a simple regulated supply for the jfet
actually, in some way even better
compressor sounds ok again
for some reason my compressor didnt work so well with 2.5uf
could be because it was a different type
also tried a 3.3uf orange colored cap
didnt last one minute
should I have a selector option, it would switch between 2.2uf and 2.5uf
worth the trouble ? yeah, its enough to make that little important difference
might be it actually affects the tuning pitch just a bit, but enough for 'certain occations'
anyway, a switch would at least make it easier to test different caps
well, enough of that
working on a simple regulated supply for the jfet
Hi Tinitus, glad you tried out the bypass caps. It may help also with hum and radio interference too.
The different cap types can affect the subtle differences in sound. Also tolerance on caps is wide so was could to try different types to get it sounding right. Was the 2.5 uF a film cap?
The different cap types can affect the subtle differences in sound. Also tolerance on caps is wide so was could to try different types to get it sounding right. Was the 2.5 uF a film cap?
Was the 2.5 uF a film cap?
yes, the 2.5uf was poly type
a bipolar smooth foil might be worth a try
still happy with the 2.2uf
30year old and weird Wima MKC4 type
my regulator is finished
only needs power, and a check
my regulator is finished
only needs power, and a check
and its working, 16.6V
sounds more precise, and plays faster
I have removed bypass cap again
with the regulated supply something changed
sounded out of phase, like loosing hearing on one ear
I did try to increase cap from 2.2uf to 3.3uf
and it did help, but still better without
seem I got my sound back, in the most simple way
small simple regulated supply, and nothing else
wonder if it works a bit like a ccs
then there should be no bypass cap, right ?
maybe thats what it needs, a ccs
will look at inserting a LED in the source res
with the regulated supply something changed
sounded out of phase, like loosing hearing on one ear
I did try to increase cap from 2.2uf to 3.3uf
and it did help, but still better without
seem I got my sound back, in the most simple way
small simple regulated supply, and nothing else
wonder if it works a bit like a ccs
then there should be no bypass cap, right ?
maybe thats what it needs, a ccs
will look at inserting a LED in the source res
The bypass cap is increasing normally the gain on the stage, and you could be hitting saturation. Ids, gate bias and bypass cap will all play a part in whether you are at a signal operating point that is pleasing on the ears. For guitar there is more reasons to play with saturation and cutoff, but you may want a clean signal for bass at least at the first stage, with plenty of headroom.
Ids, gate bias and bypass cap will all play a part in whether you are at a signal operating point that is pleasing on the ears.
I think you have a good point with that
regulator drops about 2V
heck, right now Im thinking maybe 2V is too small
anyway, I still measure about the same 80mv over the source resistor
well, that said, I found the sound nice softy round
but I prefer a more dry sound in the long run
fells kind of less 'picky'
so I threw in a couple of 3300uf, seperated by a 1ohm resistor, and the bleeder/LED
and that actually gave a much more dry sound
I will try to go down to 15V
experiments not over yet
trying to figure out that LED thing
a found interesting stuff
well, I have heard it before, and not had a clew what
lets see how it works
plate voltage divided by plate resistor gives bias current
ups, sorry, drain and not plate
I have about 8V and 1K5
and that gives 5ma
wow, I think 5ma have been mentioned by Nelson
and to check source resistor, I have 80mv and 15R
funny, but thats also 5ma...wow, it works
so, to calculate the LED current flow I would need to know its inner resistance, I guess
and ups again, forgetting about jfet type and idss
a found interesting stuff
well, I have heard it before, and not had a clew what
lets see how it works
plate voltage divided by plate resistor gives bias current
ups, sorry, drain and not plate
I have about 8V and 1K5
and that gives 5ma
wow, I think 5ma have been mentioned by Nelson
and to check source resistor, I have 80mv and 15R
funny, but thats also 5ma...wow, it works
so, to calculate the LED current flow I would need to know its inner resistance, I guess
and ups again, forgetting about jfet type and idss
ahh, appears that 5ma is close to where a led turns off
does not sound very nice
but whatever
if I have undestood any of it, the LED bias is meant to lower source(cathode) resistance to achieve better or more stable gain
but a 15R resistor is already low, so whats the point anyway
does not sound very nice
but whatever
if I have undestood any of it, the LED bias is meant to lower source(cathode) resistance to achieve better or more stable gain
but a 15R resistor is already low, so whats the point anyway
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