Samson pl1602 questions

[nosaj]

I've got a samson pl1602 Where Mic1 doesn't have as much Gain as Mic3. Do XLR jacks get dirty like audio jacks?
On the front i made the settings exactly the same for mic one and mic 3. Even set the trim the same.
Any chance someone has a schematic ?

Here's all I could find the user manual
http://www.samsontech.com/site_media...602_manual.pdf

Thanks,
nosaj

[Enzo]

Not likely, but those channels do have insert jacks don't they? And dirty contacts in the insert could cause dropped levels...Try poking a plug in and out of the low channel's insert jack a few times.

Did you try an unbalanced signal into the 1/4" jacks for those channels to see if one of those was low too or are they both the same level that way?

[nosaj]

Not likely, but those channels do have insert jacks don't they? And dirty contacts in the insert could cause dropped levels...Try poking a plug in and out of the low channel's insert jack a few times.

Did you try an unbalanced signal into the 1/4" jacks for those channels to see if one of those was low too or are they both the same level that way?

I used a microphone into mic 1 then I used a shure xlr to 1/4 impedance matcher volume definately lower on mic one. I have to max the trim know just to hear it.

thanks,
nosaj

[Enzo]

Let me get it staight, an XLR mic with all setting same, into MIC1 then into MIC3, and 1 sounds weak. Are you saying that you used an adaptor to plug the mic into the TRS jack1 and then TRS jack3 and the same difference was there? In other words plugging any signal source into TRS jacks 1 and 3 will show the same difference?

Did you probe the insert jacks for mic1?


Did you ASK Samson for the schematic? Include your serial number in any communication.

[The Dude]

It should also be noted that the 1/4" input is often line level. I might expect that the level would be low plugging a mic into that input.

[nosaj]

Let me get it staight, an XLR mic with all setting same, into MIC1 then into MIC3, and 1 sounds weak. Are you saying that you used an adaptor to plug the mic into the TRS jack1 and then TRS jack3 and the same difference was there? In other words plugging any signal source into TRS jacks 1 and 3 will show the same difference?

Did you probe the insert jacks for mic1?


Did you ASK Samson for the schematic? Include your serial number in any communication.

Yes, and using the adapter into the TRS has more vol. Just Mic 1 has low output. Mic 3 is excellent. Have not contacted Samson but will do that tomorrow.

Thanks,
nosaj

[The Dude]

If the insert jack is louder than the mic input, your first gain stage is not working on that channel. It should be relatively simple to find. It will likely be an op amp, though sometimes a differential pair of transistors or FET's is used. I'm betting Sampson uses op amps. Just follow the mic input to the first gain stage and check either voltages on the op amp or check for shorted transistors if that's what they use. Sometimes in the smaller/cheaper mixers, 2 channels will share an op amp, but that doesn't mean that 1/2 of it couldn't be bad.

[nosaj]

If the insert jack is louder than the mic input, your first gain stage is not working on that channel. It should be relatively simple to find. It will likely be an op amp, though sometimes a differential pair of transistors or FET's is used. I'm betting Sampson uses op amps. Just follow the mic input to the first gain stage and check either voltages on the op amp or check for shorted transistors if that's what they use. Sometimes in the smaller/cheaper mixers, 2 channels will share an op amp, but that doesn't mean that 1/2 of it couldn't be bad.

I found this in the manual can anyone tell me what HA and BA stands for? Looks like there are 4 transistors ( which do are not shorted)by the mic input and then jrc 2068dd opamps all over the board.

Thanks,
nosaj

[J M Fahey]

HA might be a discrete gain block (since you only saw transistors there) while BA might mean the ones based on Op Amps.
In any case, the diagram shows clearly the possibly weak/dirty leaf switch suggested by Enzo or the possibly bad balanced first Mic stage suggested by Dude.

Wait for the original schematic, but if not available, follow the tracks from XLR pins which will lead you to the balanced mic preamp, post a close up picture or two and lift the schematic the old way: good light and reading glasses, paper, pencil, and some background music.

That said, I wouldn´t expect much more than a discrete differential transistor pair (for lowest noise) feeding an Op Amp, not too different to:

(C) ESP/Rod Elliott

[nosaj]

HA might be a discrete gain block (since you only saw transistors there) while BA might mean the ones based on Op Amps.
In any case, the diagram shows clearly the possibly weak/dirty leaf switch suggested by Enzo or the possibly bad balanced first Mic stage suggested by Dude.

Wait for the original schematic, but if not available, follow the tracks from XLR pins which will lead you to the balanced mic preamp, post a close up picture or two and lift the schematic the old way: good light and reading glasses, paper, pencil, and some background music.

That said, I wouldn´t expect much more than a discrete differential transistor pair (for lowest noise) feeding an Op Amp, not too different to:

(C) ESP/Rod Elliott

Here's the schematic, they were very helpful.
Nosaj
PL1602.pdf

[Jazz P Bass]

Samson was helpful?????

When did that start?

Starting about 2 years ago all that I could get out of them was a hard time.

Huh. Then Times They Are A Changin'.

[nosaj]

Samson was helpful?????

When did that start?

Starting about 2 years ago all that I could get out of them was a hard time.

Huh. Then Times They Are A Changin'.

5 mins on hold then a very nice gentlemen asked how he could help me and emailed me the schematic . No questions asked.

nosaj

[nosaj]

5 mins on hold then a very nice gentlemen asked how he could help me and emailed me the schematic . No questions asked.

nosaj

Well I picked it up again, With a 1k signal injected into the center pin of mic 1 the level is the same when I plug into insert1(previously I missed what the inserts were, I now know) or into input1. But if I use a microphone in mic1 I cannot hear it but if plugged into mic3 the volume is fine. The -+15 rails on mic1 are spot on.

I think I need a better method here than what I'm trying. I did clean all the jacks but no change even the xlr.

nosaj

[Enzo]

The mic input is balanced, pins 2 and 3. You can get sound inputting one of those pins, but that doesn't test the functionality of the circuit.

Pin 1 of the XLR should be ground. If you cannot see which is pin 1, just find the pin that is wired to ground, the other two are the hot pins. So in the good channel apply your signal to the center pin (pin 3), and then to the other hot pin (pin 2). Do both sound about the same? Now go to the bad channel, try pin 3, then pin 2. I bet they sound different, like one doesn't work. And since it is a balanced input, it needs both sides to be working.

[nosaj]

The mic input is balanced, pins 2 and 3. You can get sound inputting one of those pins, but that doesn't test the functionality of the circuit.

Pin 1 of the XLR should be ground. If you cannot see which is pin 1, just find the pin that is wired to ground, the other two are the hot pins. So in the good channel apply your signal to the center pin (pin 3), and then to the other hot pin (pin 2). Do both sound about the same? Now go to the bad channel, try pin 3, then pin 2. I bet they sound different, like one doesn't work. And since it is a balanced input, it needs both sides to be working.

I was getting signal on pin1 but not the others when i flipped it over I scrapped off a lot of flux and then resoldered the xlr and several other joints that look suspect. Sounds good now.. and now signal on the correct pins.
thanks,

nosaj