signal to noise in the GSSL comps.
- Thread starter j.hall
- Start date
Help Support GroupDIY Audio Forum:
Kev
Well-known member
errr !!!
pressure
no schematic ... :shock:
theres an electrolytic after the input 5534 ... link the cold of this to the input pin ... err ... or jump the electro all together ???
pin 2 ?
:roll:
of the first 1/2 of the 5532 (same channel)
if you used a socket for the VCA ... remove the VCA
arrgghh
I should have stayed away !!
pressure
no schematic ... :shock:
theres an electrolytic after the input 5534 ... link the cold of this to the input pin ... err ... or jump the electro all together ???
pin 2 ?
:roll:
of the first 1/2 of the 5532 (same channel)
if you used a socket for the VCA ... remove the VCA
arrgghh
I should have stayed away !!
Kev
Well-known member
NO !
you will still need to link
to get from 5534 output to 5532 input
gain structure may be a little changed but close enough
no schem ... and all memory !!! arrgghh ... run away Kev.
you will still need to link
to get from 5534 output to 5532 input
gain structure may be a little changed but close enough
no schem ... and all memory !!! arrgghh ... run away Kev.
chrissugar
Well-known member
Hey j.hall
Pull out the 2180 from the socket and make a bypass from pin 1 to pin 8 of the VCA. It should pass audio.
The bypass link will connect the output of the balanced input receiver to the input of the rebalancing output circuit.
By the way, the bypass switch is not a real hardware bypass, it disables the control signal to the VCA. The signal will pass the VCA even in bypass mode.
chrissugar
Pull out the 2180 from the socket and make a bypass from pin 1 to pin 8 of the VCA. It should pass audio.
The bypass link will connect the output of the balanced input receiver to the input of the rebalancing output circuit.
By the way, the bypass switch is not a real hardware bypass, it disables the control signal to the VCA. The signal will pass the VCA even in bypass mode.
chrissugar
so, let me make sure i have this right.
if i pull the 2180, and put a jumper in from pin 1 to pin 8 it will pass audio and i don't need to do what kev said?
i want to keep this as simple as possible to aid the troubleshooting.
i doubt i have a bad chip as i've swapped them and the problem stays primarily on the left channel.....
if i pull the 2180, and put a jumper in from pin 1 to pin 8 it will pass audio and i don't need to do what kev said?
i want to keep this as simple as possible to aid the troubleshooting.
i doubt i have a bad chip as i've swapped them and the problem stays primarily on the left channel.....
chrissugar
Well-known member
What I say is exactly what Kev sugested but because he has no schem at hand he couldn't tell you exactly what to do.
Do this and then report. Depending of the results we can continue to troubleshoot.
chrissugar
Do this and then report. Depending of the results we can continue to troubleshoot.
chrissugar
ok, i remembered something just recently while working on this comp.
i built two....one is working great, this one has an issue.
i remembered that when i first dropped all the chips in, i accidentally turned the TL074 the wrong way, powered it up, did a few tests and realized audio wasn't passing before i figured it out.
that chip was blown and i dropped in another one and moved on.
could reversing that chip have casued other problems?
all my voltages are fine, the regulation is fine, and i haven't found any solder bridges or bad chips.
i built two....one is working great, this one has an issue.
i remembered that when i first dropped all the chips in, i accidentally turned the TL074 the wrong way, powered it up, did a few tests and realized audio wasn't passing before i figured it out.
that chip was blown and i dropped in another one and moved on.
could reversing that chip have casued other problems?
all my voltages are fine, the regulation is fine, and i haven't found any solder bridges or bad chips.
chrissugar
Well-known member
j.hall
Did you do the test?
If you did it and you have answers we can isolate the error.
chrissugar
Did you do the test?
If you did it and you have answers we can isolate the error.
chrissugar
test performed.
noise remains when VCA are "bypassed" using jumpers on the sockets.
i also re-checked my PSU section and noticed i had -24 volts feeding the negative 15 volt regulator but only 19 volts feeding the positive regulator.
the output of both looked ok, but that sort of surprised me and i could swear a few weeks back everything was normal.
if the PSU has a problem, shouldn't i be getting the noise on both channels?
anyway. the left side is still really noisy and the right side has a tiny bit of the same noise.
i aslo gutted the Left VCA section and rebuilt it hoping there was a solder bridge i just wasn't seeing with my magnifing glass....BUT NOPE.
noise remains when VCA are "bypassed" using jumpers on the sockets.
i also re-checked my PSU section and noticed i had -24 volts feeding the negative 15 volt regulator but only 19 volts feeding the positive regulator.
the output of both looked ok, but that sort of surprised me and i could swear a few weeks back everything was normal.
if the PSU has a problem, shouldn't i be getting the noise on both channels?
anyway. the left side is still really noisy and the right side has a tiny bit of the same noise.
i aslo gutted the Left VCA section and rebuilt it hoping there was a solder bridge i just wasn't seeing with my magnifing glass....BUT NOPE.
J, if you can afford it, replace all the opamps in the thing. I had trouble with mine and this fixed it... If you buy a replacement set of opamps and they all turn out to be good, yuo can use them for other projects in the future probably. I still dont know what I did wrong when I installed the opamps in mine, but when I replaced them all, all my troubles went away.
dave
dave
chrissugar
Well-known member
Hi j.hall
So it is not the VCA.
OK, now do the next test. Make a bypass from pin 1 of the right channel [you said the right channel is the good one] to pin 8 of left channel. [ I'm talking about the pins of the VCAs ]
If the noise disapears then it is clear that the input stage of the left channel is bad so you will need to change the chip [ne5534] from left input.
If the noise remains you have to change the two NE5532 from the output stage of the left channel.
Hope it is clear.
chrissugar
So it is not the VCA.
OK, now do the next test. Make a bypass from pin 1 of the right channel [you said the right channel is the good one] to pin 8 of left channel. [ I'm talking about the pins of the VCAs ]
If the noise disapears then it is clear that the input stage of the left channel is bad so you will need to change the chip [ne5534] from left input.
If the noise remains you have to change the two NE5532 from the output stage of the left channel.
Hope it is clear.
chrissugar
the pin 1 to pin 8 VCA by pass jumper doesn't work.
i'm just now getting some free time to continue testing this unit.
i made the jumper and patched a CD to the inputs. Left channel VCA jumpered, right left alone with the 2180 chip. only the right channel is passing audio.
i put the 2180's back in and now the left channel is totally dead.
one of the 5534's in the input section is running really hot. the other one is fine. i mean hot enough to burn my fing when i touch it.
that doesn't seem right.
i'm just now getting some free time to continue testing this unit.
i made the jumper and patched a CD to the inputs. Left channel VCA jumpered, right left alone with the 2180 chip. only the right channel is passing audio.
i put the 2180's back in and now the left channel is totally dead.
one of the 5534's in the input section is running really hot. the other one is fine. i mean hot enough to burn my fing when i touch it.
that doesn't seem right.
Change the hot opamp. And then - as usual: Chech for shorts, component values, psu voltages.
With the VCA's removed, you should be able to see the input signal at the input pin of the VCA's. When the VCA's are in circuit, you don't see anything here.
Jakob E.
With the VCA's removed, you should be able to see the input signal at the input pin of the VCA's. When the VCA's are in circuit, you don't see anything here.
Jakob E.
Hi :thumb:
I have some similar problem on my comp. There is noise on both channels + a little hum on the right channel. The rest (compression, makeup, meter) seems to work fine!
So I read through the thread, pulled out my two channel VCAs (2180s) and bridged pin 1 and 8 as chris suggested almost 2 years ago :grin:
Et voila, I hear the signal loud and proud at my outs. No hum at all.
So what could it be? The VCAs seem ok as they behave well in my (modded) 3630 :razz:
I just measured some volts at the empty VCA sockets and the plugged 5534s..
2180s (VCAs removed)
pin 7: 15V
pin 5: -15V ?? shouldn't that be less due the 5k1 that I have between the -15V rail and pin 5 instead of the 3k9?
5534s(while plugged in)
pins 1 and 8: 12,6 V
pin 4: -15V
pin 7: 15V
At the schemo I read that it should be +-12V at pins 7 and 4..
Is there something wrong with my circuits? Could anyone of you be so kind and give me a little hint?
BTW the two 10k, the 86R, 1M and the 50k trim around the VCAs are removed as seen in the 218x mod threads here in the forum..
:sam: :green:
I have some similar problem on my comp. There is noise on both channels + a little hum on the right channel. The rest (compression, makeup, meter) seems to work fine!
So I read through the thread, pulled out my two channel VCAs (2180s) and bridged pin 1 and 8 as chris suggested almost 2 years ago :grin:
Et voila, I hear the signal loud and proud at my outs. No hum at all.
So what could it be? The VCAs seem ok as they behave well in my (modded) 3630 :razz:
I just measured some volts at the empty VCA sockets and the plugged 5534s..
2180s (VCAs removed)
pin 7: 15V
pin 5: -15V ?? shouldn't that be less due the 5k1 that I have between the -15V rail and pin 5 instead of the 3k9?
5534s(while plugged in)
pins 1 and 8: 12,6 V
pin 4: -15V
pin 7: 15V
At the schemo I read that it should be +-12V at pins 7 and 4..
Is there something wrong with my circuits? Could anyone of you be so kind and give me a little hint?
BTW the two 10k, the 86R, 1M and the 50k trim around the VCAs are removed as seen in the 218x mod threads here in the forum..
:sam: :green:
your circuits are alright - see the pcb layout..
I was just a bit confused why in the schematic in the DBX202 EMU section the NE5534 get +-12V while in 'real life' it's +- 15V..
So what could it be? Dirt from the power supply? Or should I assume, something is wrong within the EMU section on my board?
I tested the channels with That2181LB, That2150A, DBX2151 and the That2180LB I want to use. The hum/noise is alwys there, so I guess it's not the VCAs?
I just got a small multimeter but no scope, so it's a bit like being in the dark about what the voltages look like..
So what could it be? Dirt from the power supply? Or should I assume, something is wrong within the EMU section on my board?
I tested the channels with That2181LB, That2150A, DBX2151 and the That2180LB I want to use. The hum/noise is alwys there, so I guess it's not the VCAs?
I just got a small multimeter but no scope, so it's a bit like being in the dark about what the voltages look like..
..it's just a schematic inaccuracy..
