Matt Macchiarolo wrote:
I'd definitely check out the modification situation. If it was Jim
Williams who acutally did the mod (or at least designed it if he
wasn't the one who put in the parts) even if it's based on op-amps
that aren't normally used in audio circuitry, chances are he's given
enough thought to it to use them properly, and to good advantage.
That's what he does.


My thoughts exactly. 5 of the input channels have installed his mic preamp,
I am assuming he did the install, and apparently he offered some sort of mod
on the master module as well, so I am assuming he did this mod as well. (The
literature that came with the console included a Audio Upgrades catalog.)
Both the mods on the input channels and the master module involve more than
just swapping op amps, there are several other components swapped or added
too.

So call Jim up and ask him what to look for.

I called him yesterday but caught him at a restaurant. I can wait till
Monday.

"Kurt Albershardt" wrote in message
...

So call Jim up and ask him what to look for.

I called him yesterday but caught him at a restaurant. I can wait till
Monday.

"Kurt Albershardt" wrote in message
...

So call Jim up and ask him what to look for.

"Matt Macchiarolo" wrote in message
...

Haven't yet had a chance to measure the noise yet. But that is on the
to-do
list. I did notice in when I threw up a quick mix on the console at a
moderate volume level...when I stopped the tape machine, I could hear it.
So
I pulled all the channel faders down thinking it was the cumulative noise
of
each channel but it wasn't. The noise isn't in any of the aux or efx
busses,
just the main l-r bus.

This is a dumb question, but I've gotten bagged by this. Are there any
returns coming to the main bus that might be turned up?

Peace,
Paul

"Matt Macchiarolo" wrote in message
...

Haven't yet had a chance to measure the noise yet. But that is on the
to-do
list. I did notice in when I threw up a quick mix on the console at a
moderate volume level...when I stopped the tape machine, I could hear it.
So
I pulled all the channel faders down thinking it was the cumulative noise
of
each channel but it wasn't. The noise isn't in any of the aux or efx
busses,
just the main l-r bus.

This is a dumb question, but I've gotten bagged by this. Are there any
returns coming to the main bus that might be turned up?

Peace,
Paul

This is a dumb question, but I've gotten bagged by this. Are there any
returns coming to the main bus that might be turned up?

Peace,
Paul

No, I thought of that but it;s still there even if all the returns are off.

This is a dumb question, but I've gotten bagged by this. Are there any
returns coming to the main bus that might be turned up?

Peace,
Paul

No, I thought of that but it;s still there even if all the returns are off.

Hi,

Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
noticeable level of noise in the master module when I pull up the faders,
even though there is no signal from any of the channels. I called Peavey's
tech dept and they suggested replacing the op-amps in the master module, as
they age they lose their tolerances and can cause noise (it sounds like
white noise). The manual shows that it contains a bunch of 5532's, a few TL
074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
found that there seems to be many "versions" of each chip, each with a
difference suffix to the chip number. I can physically replace the chips,
but determining the right version is beyond my expertise.

I wish I had a schematic for this mixer so I could give you a better
answer, but...

There are lower noise & higher performance parts to be sure, but there
are also have been some high dollar, high performance mixers that have
used exactly the same parts you describe. TL071's, 72's & NE5532,
NE5534s are popular basic building blocks capable of producing
excellent noise figures. I suspect it's the internal gain structure
&/or other aspects of the design and not the parts at issue. Though
you still may be able to improve by the retro-fit the Peavey tech
suggested.

There are some op amps out there with 2 to 3 nV / root Herts noise
figures... Maxim, Burr Brown, Analog Devices... Probably best to stick
with parts that others on this group or those with experience can
recommend, since the musical quality of op amps is definitely a
factor. Some op amps designed to be used in video circuits are
actually great for audio, but can be cost prohibitive. Personally, I
think Japan Radio Corp, Burr Brown & Signetics have some very musical
sounding op amps. Great specs don't always translate into great sound.
Sometimes you have to just try 'em out. Hopefully some folks on here
will give you some good advice on specific parts.

Most of the noise in mixers comes from the front end, the highest gain
section. So microphone preamplifiers are the contributor to most noise
problems. The trick in the design should be to get a low noise front
end and then operate well above the noise floor in successive gain
stages.

If you acquire the schematic & show it to a good tech & he could
research it & perhaps find some lower noise transistors to use in the
preamp stage. It is possible that the front end gain stages of your
mixer are based solely on op amps and do not have discrete transistor
preamps! If this is the case you *definitely* should try lower noise
parts in these stages!


Here's a simple idea for the adventurous:

Get a schematic and look at the power supply. If the split supply that
feeds the op amp stages is say around +/- 12 Volts or even +/- 15V,
you may be able to get improved performance by increasing the voltage
to say +/- 17 or even +/- 18 V. If the split supply is adjustable or
uses simple IC regulators it should be easy to modify or adjust.
This modification, if practical, can greatly increase head room. It
may or may not decrease noise depending on the circuit, but it's
relatively easy & shouldn't hurt anything in trying.


PS, the 741 is probably used for a metering circuit or signal light.

Skler
Austin, Tx

Hi,

Just got a new (old) mixing console, Peavey/AMR 2400, and there is a
noticeable level of noise in the master module when I pull up the faders,
even though there is no signal from any of the channels. I called Peavey's
tech dept and they suggested replacing the op-amps in the master module, as
they age they lose their tolerances and can cause noise (it sounds like
white noise). The manual shows that it contains a bunch of 5532's, a few TL
074's, a few TL 072's, and a 741. I did a search at Digikey's website, and
found that there seems to be many "versions" of each chip, each with a
difference suffix to the chip number. I can physically replace the chips,
but determining the right version is beyond my expertise.

I wish I had a schematic for this mixer so I could give you a better
answer, but...

There are lower noise & higher performance parts to be sure, but there
are also have been some high dollar, high performance mixers that have
used exactly the same parts you describe. TL071's, 72's & NE5532,
NE5534s are popular basic building blocks capable of producing
excellent noise figures. I suspect it's the internal gain structure
&/or other aspects of the design and not the parts at issue. Though
you still may be able to improve by the retro-fit the Peavey tech
suggested.

There are some op amps out there with 2 to 3 nV / root Herts noise
figures... Maxim, Burr Brown, Analog Devices... Probably best to stick
with parts that others on this group or those with experience can
recommend, since the musical quality of op amps is definitely a
factor. Some op amps designed to be used in video circuits are
actually great for audio, but can be cost prohibitive. Personally, I
think Japan Radio Corp, Burr Brown & Signetics have some very musical
sounding op amps. Great specs don't always translate into great sound.
Sometimes you have to just try 'em out. Hopefully some folks on here
will give you some good advice on specific parts.

Most of the noise in mixers comes from the front end, the highest gain
section. So microphone preamplifiers are the contributor to most noise
problems. The trick in the design should be to get a low noise front
end and then operate well above the noise floor in successive gain
stages.

If you acquire the schematic & show it to a good tech & he could
research it & perhaps find some lower noise transistors to use in the
preamp stage. It is possible that the front end gain stages of your
mixer are based solely on op amps and do not have discrete transistor
preamps! If this is the case you *definitely* should try lower noise
parts in these stages!


Here's a simple idea for the adventurous:

Get a schematic and look at the power supply. If the split supply that
feeds the op amp stages is say around +/- 12 Volts or even +/- 15V,
you may be able to get improved performance by increasing the voltage
to say +/- 17 or even +/- 18 V. If the split supply is adjustable or
uses simple IC regulators it should be easy to modify or adjust.
This modification, if practical, can greatly increase head room. It
may or may not decrease noise depending on the circuit, but it's
relatively easy & shouldn't hurt anything in trying.


PS, the 741 is probably used for a metering circuit or signal light.

Skler
Austin, Tx

Oh, I forgot to mention...

It is possible for op amps to operate in a failture mode in which they
still pass signal, but they are very noisy and/or their gain is
altered, so you should definitely replace the op amps in the suspect
stage of your mixer, even if you just use the original parts!

Skler

Oh, I forgot to mention...

It is possible for op amps to operate in a failture mode in which they
still pass signal, but they are very noisy and/or their gain is
altered, so you should definitely replace the op amps in the suspect
stage of your mixer, even if you just use the original parts!

Skler

In article , Scott Dorsey
wrote:

Fletcher basically was driven off the group by the poor S/N and by his
ISP's lousy news feed. He hasn't been here in ages. I miss him a lot.
--scott



Scott,

I think the real reason Fletcher isn't here has to do with $. His
current gig online pays, and pretty good too.

Ya, he was reason enough to keep tabs on this newsgroup. Now this place
looks like Fallujah.





David Correia
Celebration Sound
Warren, Rhode Island


www.CelebrationSound.com

In article , Scott Dorsey
wrote:

Fletcher basically was driven off the group by the poor S/N and by his
ISP's lousy news feed. He hasn't been here in ages. I miss him a lot.
--scott



Scott,

I think the real reason Fletcher isn't here has to do with $. His
current gig online pays, and pretty good too.

Ya, he was reason enough to keep tabs on this newsgroup. Now this place
looks like Fallujah.





David Correia
Celebration Sound
Warren, Rhode Island


www.CelebrationSound.com

Phil Allison wrote:
"Matt Macchiarolo"


Don't bother abour Phil, he's our resident rodent / troll.

Every group seems to have one.





** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.





........... Phil



Phil,
Why are you?

Phil Allison wrote:
"Matt Macchiarolo"


Don't bother abour Phil, he's our resident rodent / troll.

Every group seems to have one.





** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.





........... Phil



Phil,
Why are you?

"david" wrote in message news:161120040155442790%

I think the real reason Fletcher isn't here has to do with $. His
current gig online pays, and pretty good too.

Ya, he was reason enough to keep tabs on this newsgroup. Now this place
looks like Fallujah.


Yeah, and he took no prisoners, just like a Marine.

geoff

"david" wrote in message news:161120040155442790%

I think the real reason Fletcher isn't here has to do with $. His
current gig online pays, and pretty good too.

Ya, he was reason enough to keep tabs on this newsgroup. Now this place
looks like Fallujah.


Yeah, and he took no prisoners, just like a Marine.

geoff

"Phil Allison" wrote in message

"Matt Macchiarolo"

Don't bother about Phil, he's our resident rodent / troll.

Every group seems to have one.

** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.

Great job of misplaced priorities, Phil! The folks you damn here are among
the most productive on-topic posters this group has.

It's the Off-Topic trolls (names withheld to avoid inciting the guilty to
additional misbehavior) that have ruined this place.

"Phil Allison" wrote in message

"Matt Macchiarolo"

Don't bother about Phil, he's our resident rodent / troll.

Every group seems to have one.

** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.

Great job of misplaced priorities, Phil! The folks you damn here are among
the most productive on-topic posters this group has.

It's the Off-Topic trolls (names withheld to avoid inciting the guilty to
additional misbehavior) that have ruined this place.

"Arny Krueger"
"Phil Allison"
** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.


Great job of misplaced priorities, Phil! The folks you damn here are among
the most productive on-topic posters this group has.


** As near inexhaustible sources of copious amounts of misinformation the
above trolls are Second to None.

As ever present, menacing threats to any person *daring* to post
technically factual information here the above trolls are the Grand Masters.

The above trolls also have a small army of acolytes and sycophants who
together form a pernicious infestation that chokes and ruins a public
information forum like this - then of course even worse trolls follow
in their footsteps ( ones everyone recognises as trolls ) much as do
cockroaches down a sewer.

As a posturing "One Trick Pony" with no insight into how damn little he
comprehends on practically any subject - Arny Krueger can find plenty of
like minded types here to keep him company.




............. Phil

"Arny Krueger"
"Phil Allison"
** This NG consists of virtually 100 % trolls.

Trolls with names like Dorsey, Rivers, Cain, Ford, Shaw and a cast of
thousands of know nothings.


Great job of misplaced priorities, Phil! The folks you damn here are among
the most productive on-topic posters this group has.


** As near inexhaustible sources of copious amounts of misinformation the
above trolls are Second to None.

As ever present, menacing threats to any person *daring* to post
technically factual information here the above trolls are the Grand Masters.

The above trolls also have a small army of acolytes and sycophants who
together form a pernicious infestation that chokes and ruins a public
information forum like this - then of course even worse trolls follow
in their footsteps ( ones everyone recognises as trolls ) much as do
cockroaches down a sewer.

As a posturing "One Trick Pony" with no insight into how damn little he
comprehends on practically any subject - Arny Krueger can find plenty of
like minded types here to keep him company.




............. Phil

"Arny Krueger" wrote ...
It's the Off-Topic trolls (names withheld to avoid inciting
the guilty to additional misbehavior) that have ruined this place.

Thats why they invented killfiles (for both individuals and
for OT threads). Quite marvelous and effective noise-reduction.
Would that we had devices that good for audio!

"Arny Krueger" wrote ...
It's the Off-Topic trolls (names withheld to avoid inciting
the guilty to additional misbehavior) that have ruined this place.

Thats why they invented killfiles (for both individuals and
for OT threads). Quite marvelous and effective noise-reduction.
Would that we had devices that good for audio!

"Richard Crowley"
"Arny Krueger" wrote ...
It's the Off-Topic trolls (names withheld to avoid inciting
the guilty to additional misbehavior) that have ruined this place.

Thats why they invented killfiles (for both individuals and
for OT threads). Quite marvelous and effective noise-reduction.



** I bet they invented sand just so ostriches like you Crowley could stick
their heads in it.

Would never do to have your cherished prejudices challenged now would
it ???





............... Phil

"Richard Crowley"
"Arny Krueger" wrote ...
It's the Off-Topic trolls (names withheld to avoid inciting
the guilty to additional misbehavior) that have ruined this place.

Thats why they invented killfiles (for both individuals and
for OT threads). Quite marvelous and effective noise-reduction.



** I bet they invented sand just so ostriches like you Crowley could stick
their heads in it.

Would never do to have your cherished prejudices challenged now would
it ???





............... Phil