TAC MATCHLESS RECAP

Graham Langley founded Amek in 1973 with Nick Franks. Since then, AMEK and TAC recording consoles have been the choice of demanding audio professionals for over 25 years.

Moderator: Matt Syson

Postby brianroth » Thu Feb 15, 2007 8:42 pm

The reference guide I have shows that #12 AWG wire has a resistance of 1.62 Ohms/1000 feet, or 0.00162 Ohms/foot. Assuming the distance between the PSU and desk was 25 feet, that would be a total of 50 feet of cable for the positive and negative rail lines combined, or a total of 0.081 Ohms. If 10A of current is flowing, then the voltage drop would be 0.81 Volts rail to rail, if I've done all of this correctly. Hence, that would argue for an even larger conductor than #12 to meet your suggestion of 0.3V drop/wire.

To be honest, I don't recall how many conductors (if more than one per rail) or what gauge that TAC used with the OEM "snake" and will have to answer that question.

I hadn't noticed the isolation diodes within each module, likely because it was never an issue for me! <grin> Plus, the schematics are not at my fingertips, so that design feature was unknown to me until you mentioned it.

Thanks again for the comments, Matt.


Bri
User avatar
brianroth
Yacht Rocker
 
Posts: 312
Joined: Tue Oct 10, 2006 2:04 am
Location: Oklahoma City

Postby Matt Syson » Fri Feb 16, 2007 4:17 am

Hi Brian
I meant 0.3 volts for 1 run not the return loop so you would be 'allowed' 0.6 Volts. 0.3 is only a suggestion anywat, it is not so important if it were 0.5 per run. An Einstein typically loses this on a standard cable.
A matchless does not take anything like 10 amps, I think it is about 6 for positive and 4.5 for negative. It must be considerably less than 10 otherwise 10Amp fuses in the AC part of the supply would never hold up.
Thus your 12 gauge (whatever the hell that may be) is plenty.
What is the dynamic impedance value for a 1N4001 diode with say 70mA flowing through it?
Matt S
Matt Syson
Engineer
 
Posts: 1030
Joined: Sun Oct 08, 2006 6:04 am
Location: North UK

Postby Audio Maintenance Limited » Fri Feb 16, 2007 4:48 am

You'll probably find that the DC cable supplied with the console is 0.75mm2 as it is quite easy to fit it into the 4 pin XLR..... which I would expect to typically give you about a 1 volt drop .... obviously length and load dependent.

....it is possible to fit 1.5mm2 into an XLR with a bit of a squeeze (cables that come from AML are done that way).....

... above 1.5mm2 you would need to start swapping DC connectors.

1.5mm2 should be easily sufficient for the load of a Matchless..... above that is probably just overkill.

A sensible thing to do to "beef up the PSU" would be to get a 17.5v module and use it to supply just the meterbridge.... this way you reduce the load on the console PSU (which will extend its life) and isolate the audio from any switching noise of the comparitors (assuming that comparitors generate rail noise?).

As far as capacitors go.... the 9098i ones give excellent audio results and are affordable so we fit them to everything.... the ones from here are 105C (Note: low impedence doesn't necessarily equal good audio... they are intended for PSU's / high current flow) .

Colin
www.audiomaintenance.com
Audio Maintenance Limited
AMEK/TAC Spares & Service
 
Posts: 239
Joined: Thu Oct 05, 2006 2:07 pm
Location: Manchester, UK

Postby brianroth » Sat Feb 17, 2007 4:17 am

Matt Syson wrote:Hi Brian
I meant 0.3 volts for 1 run not the return loop so you would be 'allowed' 0.6 Volts. 0.3 is only a suggestion anywat, it is not so important if it were 0.5 per run. An Einstein typically loses this on a standard cable.
A matchless does not take anything like 10 amps, I think it is about 6 for positive and 4.5 for negative. It must be considerably less than 10 otherwise 10Amp fuses in the AC part of the supply would never hold up.
Thus your 12 gauge (whatever the hell that may be) is plenty.
What is the dynamic impedance value for a 1N4001 diode with say 70mA flowing through it?
Matt S


Thanks again for the information, Matt. I plan on running some tests on the PSU Monday and will check the current consumption under various load conditions.

I would tend to think that the current consumption of any given module would be relatvely constant so the drop across the diodes would also be relatively constant. I just looked at the curves for fairchild 1N400x diodes, and the drop at 50 mA is 0.7V, and at 200 mA is 0.8V (those were easy data points to pick out on the graph). That was the only useful info on that data sheet which covers any series impedance related specs.


Here in the USA, wire sizes are specified with the American Wire Gauge system, with a smaller number representing a larger wire. According to my reference book, #12 AWG has a diameter of 2.053 mm. If I correctly understand the dimension "conventions" which you and Colin are using, I guess be a wire with a cross-section area of 3.3 mm2??? (Pi * R^2)

Bri
User avatar
brianroth
Yacht Rocker
 
Posts: 312
Joined: Tue Oct 10, 2006 2:04 am
Location: Oklahoma City

Postby brianroth » Sat Feb 17, 2007 4:30 am

Colin, I need to find a handy reference which converts from AWG size numbers to the (cross-sectional area???) millimeter sizes which you and Matt have been mentioning.

Splitting up the rails for the meterbridge and the rest of the desk is a very interesting idea, and would require only the installation of a new DC connector. I'm not a big fan of XLR connectors for powering, although I do see that a Neutrik XLR4 connector is specified for a maxiumum of 10A.

We are definitely interested in your capacitor "kit" for the 32 channel Matchless, and I will contact you via an offline email.

Thanks!

Bri
User avatar
brianroth
Yacht Rocker
 
Posts: 312
Joined: Tue Oct 10, 2006 2:04 am
Location: Oklahoma City

Postby emtee » Sat Feb 17, 2007 6:21 am

Try this calculator for wire sizes -

http://www.eraser.com/main.cgi?m=wirecalc

Or there's a table here -

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

Is the Matchless in question actually 32 channels or is this a typo? I've only seem 36 & 26 before.
emtee
VU Meter Specialist
 
Posts: 44
Joined: Mon Oct 23, 2006 4:08 pm
Location: Sheffield - UK

Postby Audio Maintenance Limited » Sat Feb 17, 2007 7:07 am

Matchless capacitor quantities and part numbers;
click here or right click to save
Audio Maintenance Limited
AMEK/TAC Spares & Service
 
Posts: 239
Joined: Thu Oct 05, 2006 2:07 pm
Location: Manchester, UK

Postby brianroth » Sun Feb 18, 2007 4:10 am

emtee wrote:Try this calculator for wire sizes -

http://www.eraser.com/main.cgi?m=wirecalc

Or there's a table here -

http://www.engineeringtoolbox.com/wire-gauges-d_419.html

Is the Matchless in question actually 32 channels or is this a typo? I've only seem 36 & 26 before.


So, my understanding is correct re. wire gauges versus dimensions as used in the UK. That second table shows that 12AWG cable is 3.3 mm^2 just as I calculated, and posted in an earlier message.

Going back through earlier posts, 0.75 mm^2 would be in between 18 and 20AWG, which seems tiny to me! 1.5 mm^2 would be in between 16 and 14AWG, much better.

I think you're correct, Emtee...36 channels.

Bri
User avatar
brianroth
Yacht Rocker
 
Posts: 312
Joined: Tue Oct 10, 2006 2:04 am
Location: Oklahoma City

Postby brianroth » Sun Feb 18, 2007 4:18 am

Audio Maintenance Limited wrote:Matchless capacitor quantities and part numbers;
click here or right click to save


Thanks Colin! I will email you to obtain the current "kit" pricing for the desk modules, since the spreadsheet indicates those prices may have been subject to change.

Bri
User avatar
brianroth
Yacht Rocker
 
Posts: 312
Joined: Tue Oct 10, 2006 2:04 am
Location: Oklahoma City

Postby Matt Syson » Sun Feb 18, 2007 5:13 am

Hi
2.5mm2 or 4mm2 would be European favoured sizes and if you were to be going 25 feet then perhaps the thicker would be preferable but the awg that is around 3.3mm2 is probably fine.
Incidentally I think the slope resistance at 70mA is around 0.6 ohms.
I measured at 50,60,70 and 80mA noting the change in voltage across the diode. At the lower end of the range the resistance is around 3 ohms.
Matt s
Matt Syson
Engineer
 
Posts: 1030
Joined: Sun Oct 08, 2006 6:04 am
Location: North UK

PreviousNext

Return to AMEK & TAC Recording Consoles

Who is online

Users browsing this forum: No registered users and 6 guests

 
Mr Patchbay sells patchbays, tt/bantam cables and more