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Analog mixing desk - Soundcraft series two
Old 13th January 2020
  #31
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Alex,
I did check all the meters. They are ‘locked up.’ No needle bounce. No action outside of circuit.
I attempted getting into one of them. It just seems delicate enough that I stopped before disaster.
All of the circuits outside are operable.
I moved meters around, which IS a time consuming b$tch!
Thanks for the reply.
John
Old 14th January 2020
  #32
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crosscutred's Avatar
Quote:
Originally Posted by hnbcstudios View Post
Alex,
I did check all the meters. They are ‘locked up.’ No needle bounce. No action outside of circuit.
I attempted getting into one of them. It just seems delicate enough that I stopped before disaster.
All of the circuits outside are operable.
I moved meters around, which IS a time consuming b$tch!
Thanks for the reply.
John
Good stuff, just wanted to check you weren't going to spend a lot of money when a cheap component would fix it.
Old 4 weeks ago
  #33
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hnbcstudios,

Thanks for sharing your experience. I wish I could be of any assistance but I admit that I don't have experience so any ideas from me would be just.. unreliable.

Best thing I can do at the moment is share the stages of my restoration project as it develops.

I have ordered some Nichicon and Panasonic capacitors as well as Toshiba transistors, as pointed out by J.Williams, so I should begin replacing them in the power supply and desk. I will report back when I test the sound before & after.

Jim, I read that you have used the NOS LME49740NA replacing the TL074CN opamps. Is that a direct (swap out / swap in) procedure with this desk?
How about the smaller OPA1641 in place of MC1741SCP1?

I have read a lot about opamps lately but sometimes reading information without having the necessary, prior, knowledge simply adds confusion to the equation, which is logical..


(Picture of Swept-EQ Channel : Magenta = MC1741SCP1
Blue = TL074CN )
Attached Thumbnails
Analog mixing desk - Soundcraft series two-channel-opamps-.jpg  
Old 4 weeks ago
  #34
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crosscutred's Avatar
Quote:
Originally Posted by bagomusic View Post

Jim, I read that you have used the NOS LME49740NA replacing the TL074CN opamps. Is that a direct (swap out / swap in) procedure with this desk?
How about the smaller OPA1641 in place of MC1741SCP1?

I have read a lot about opamps lately but sometimes reading information without having the necessary, prior, knowledge simply adds confusion to the equation, which is logical..


(Picture of Swept-EQ Channel : Magenta = MC1741SCP1
Blue = TL074CN )
In your situation I would leave the existing opamps alone until you know the sound of the desk as it was designed, then you have something to compare against.
It's very much a matter of taste.
Old 4 weeks ago
  #35
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Quote:
Originally Posted by crosscutred View Post
In your situation I would leave the existing opamps alone until you know the sound of the desk as it was designed, then you have something to compare against.
It's very much a matter of taste.

Thanks.

What about changing opamps on a few channels, for example 1-4 so I could have a more direct sound comparison with the rest? Would that be a good idea or perhaps not?

When I had the desk working I found the bass frequencies to be a little shy and not too tight for my taste - same goes for the extension of the higher frequencies. Is this something to consider in view of the opamps?


Cheers.
Old 4 weeks ago
  #36
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crosscutred's Avatar
Quote:
Originally Posted by bagomusic View Post
Thanks.

What about changing opamps on a few channels, for example 1-4 so I could have a more direct sound comparison with the rest? Would that be a good idea or perhaps not?

When I had the desk working I found the bass frequencies to be a little shy and not too tight for my taste - same goes for the extension of the higher frequencies. Is this something to consider in view of the opamps?


Cheers.
You will probably find the sound much improved by recapping alone.

When I have started messing with op amp swaps in old Soundcraft desks it either results in no significant change or things sound "thinner" probably due to less distortion. It looks better on a scope but that isn't always what you're shooting for.

This desk is never going to be a "posh" sounding desk (for want of a better description) which doesn't mean it won't sound great.

For the channels you want to start experimenting with, I would make them work properly first (you can then make sure the test channel sounds the same as the control) then install chip sockets, that will make it easier to compare different chips.

I could well be wrong there is always another chip or mod to try.

Have fun!
Old 4 weeks ago
  #37
Lives for gear
Op amp changes can either make a huge difference or none at all, sonically. Really depends on the board I think. One thing tho, new op amps will still sound trash through old caps . Old caps in the master section will suck
The life out of any modded channel.

Cross cut is right, get the board working well with the original op amps before experiementing with mods, saves time and money.

Doing two or four channels as a test is great at that point, you can compare etc.
Old 3 weeks ago
  #38
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Great guys, thank you very much.

Just one final thing, if I decide in the end to change opamps in a couple of channels, would the LME49740NA be a direct replacement for Tl074cn or I will run into trouble just by swapping them?

Last edited by bagomusic; 3 weeks ago at 09:43 PM..
Old 3 weeks ago
  #39
14 pin DIP quad opamps like LME49740 or even OPA4134 are long out of production. NOS prices are sky high, IF you can find the real deal. Many are remarked Chi-com crap.

SOIC dual opamp to quad adaptors give all the choices.
Old 3 weeks ago
  #40
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Ah, I see.
I know that it is probably a matter of taste, but would you recommend any combo (adapter + opamps)? For calculating the cost as well..
Old 3 weeks ago
  #41
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Quote:
Originally Posted by bagomusic View Post
Here are a few photos of the board:
what a beauty
Old 3 weeks ago
  #42
Quote:
Originally Posted by bagomusic View Post
Ah, I see.
I know that it is probably a matter of taste, but would you recommend any combo (adapter + opamps)? For calculating the cost as well..
Not without adding the missing phase compensation and power supply decoupling caps. Each must be checked on a scope for instabilities.
Old 3 weeks ago
  #43
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Understood. Thank you.
Old 3 weeks ago
  #44
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Manual

Found this link for the series II manual

https://www.manualslib.com/manual/10...-Series-2.html
Old 3 weeks ago
  #45
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Great stuff Ade,
Thanks!
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