You are here

I found an old desk in the shed...

Customising, building or repairing your own gear? Need help with acoustic treatment or soundproofing? Ask away…

Re: I found an old desk in the shed...

Postby ef37a » Mon Sep 07, 2020 10:10 am

Arpangel wrote:
ef37a wrote:"I would only ever use it for line level signals, forget microphones."

Ah, not THAT good then? And "completely rebuilt"? Sounds a bit 'Triggers Broom' to me!

Dave.

It doesn’t have balanced inputs, mic or line, I only ever used it for synths, which sounded amazing.
I didn’t renew any of the caps etc, I was scared of loosing the sound, all the sockets were worn out, and the wiring on the stereo buss looked like it was done with old bell wire, I replaced that with 00 gauge model railway track rails, and replaced all the jack sockets.
I know of a few mixer manufactures who used model rail track for bus bars, it’s ideal.
I also replaced all the faders, there really wasn’t anything else wrong with it.

Ah! It is a LINE level mixer...did not know that. Replacing the caps would not "change the sound" so long as you fitted the same value. Mind you, the caps in the EQ will be foil types and really do not age. Even electrolytics last way longer than many people think.

Dave.
ef37a
Jedi Poster
Posts: 12036
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: I found an old desk in the shed...

Postby Folderol » Mon Sep 07, 2020 10:40 am

Being slightly pedantic, there is the possibility the very old oil filled 'bumble bees' could change the sound slightly, as the foil can move dependent on voltage. In theory that changes the capacitance and also the leakage current (which is comparatively high). I don't know if anyone ever did a proper test of this, and if so how much difference it actually made.
User avatar
Folderol
Jedi Poster
Posts: 11367
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: I found an old desk in the shed...

Postby ef37a » Mon Sep 07, 2020 11:58 am

Folderol wrote:Being slightly pedantic, there is the possibility the very old oil filled 'bumble bees' could change the sound slightly, as the foil can move dependent on voltage. In theory that changes the capacitance and also the leakage current (which is comparatively high). I don't know if anyone ever did a proper test of this, and if so how much difference it actually made.

Well! If you are talking about "crap caps" Will all bets are off! And, a "Varicap" effect? At 741 supply voltages?

Yes, old capacitors leaked, in valve kit but I don't think I have ever had one fail in solid state gear in forty years? Plus, never had a cap fail in any Blackstar amp, valve (up to 700V!) or sstate.

Dave.
ef37a
Jedi Poster
Posts: 12036
Joined: Mon May 29, 2006 12:00 am
Location: northampton uk

Re: I found an old desk in the shed...

Postby James Perrett » Mon Sep 07, 2020 12:56 pm

ef37a wrote:Ah! It is a LINE level mixer...did not know that.

Tony was using it as a line level mixer but, as it sounds like it was an MP175, it would have had mic/line switches on the input. Back in those days most PA mics would have come with an XLR to jack lead as most PA amps had unbalanced jack inputs for mics so the choice of unbalanced inputs wasn't that strange.

The subsequent model, the MP180, had balanced inputs. As far as I can remember the capacitors are mainly the green Mylar type.

In my experience the noise is only an issue with quiet sources - with typical rock music sources the limitation is still tape hiss.

As Tony says, the eq is simple but just right on these.
User avatar
James Perrett
Moderator
Posts: 9694
Joined: Mon Sep 10, 2001 12:00 am
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Previous