mod Allen & Heath Mod 2 for +4 to connect up a 16trk

How does the board sound? I have one I am in the middle of restoring.

Thank you,
Chris

My GS3V 24x8 board has this option, but you need to have cards from A & H , I believe. I stayed at -10 and it is fine for my application. When I looked into it it seemed like too much trouble.

First of all, does your multitrack really need a +4dBU signal? It might have enough gain to compensate for a lower input level.

If you really do need +4, probably better to use an external box rather than kludge up the inside of your console. If you are an electronics novice, as you seem to be implying, you would not be well-advised to dig into the innards of your console needlessly.

A well-designed external box would do the job with quality as good (probably better) than anything you could cram inside your console.

My A&H GL3 also have an option in the form of a Direct Out. This option is available as a post fade post mute -2dBu signal. Its taken from the input card.

Page 7 here!
www.mentol.dk/diy/schem/gl3.pdf

Soeren

Dimebag,

I think it is the old discrete A&H modular-2 you mean.

What I remember, it have a nominal level line in/out around 1 volt "0 dB" so it is very near "+4 dB" (no consideraiton to dBm, v or u)

In the end of 1970`s I modified some of this consoles to work together with Scully 8 and 16 track machines, so if you tell me more about your idea, maybe I have some usable notes in my old documentions.

--Bo

db,

If the recorder have +4 dB operation level in and out, and the console have "0 dB" nominal level in and out, (what I remember) and if the console VU-meters read 0 dB, you shall have approx -4 dB on the recoder VU.

Further, the console in and outputs are un-balanced and the recorder in and outputs are electronic balanced (what I think), you must connect the recorders XLR-connectors pin 2 as +/Hi and pin 1 as ground/screen, and then then link pin 3 to pin 1 (ground/screen)
If you not have do that, you can have additional 6 dB lower level, (both in/out side) because the incorrect un-balanced to balanced level match.

--Bo

Dime, I am not sure why you have 1 and 9 only connected, but that probably doesn't mater. Bo, is expaining how to interface with gear that is electronically balanced via opamps/transistors vs transformer balanced. You should check out rane's website of technical articles on the subject. They seem to be the source that most folks refer to for balanced/unbal. interfacing.

http://www.rane.com/library.html

http://www.rane.com/note110.html

You could always make a test cable that uses wire clips to troubleshoot interfacing in your system. Send a tone to/from your recorder to monitor what different senarios do to the signal. If you have it wired wrong you may hear noise or a weak signal. I have done this for my studio and it has paid off dearly

-Good luck

-What Allen Heath do you have?

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dB,

you wrote:
I've connected the patchbay output of the A&H MOD 2 to the inputs of my Mitsubishi x400 digital 16 track recorder

I mean that your line outputs and input on the A&H console are un-balansed, and the in and outputs on your Mitsubishi tape recorder are electronic balanced, probably with XLR connectors.

So check that the un-balanced in and outputs on the console not only feed or receive one of the tape recorders balanced signal phases, +/hi (XLR pin 2) or - /lo (XLR pin 3)

--Bo

I had alot of trouble with my patchbay at first. I found the best way was to keep everything at the patchbay wired tip Ring and sleeve disctetely and then custom wiring the connections at the components to make sure they interface nicely with most your gear eg. the way Bo recomended to wire your recorder.

db,

I must do a comment about the unbalanced to balanced (and vice versa) wiring,

when I wrote in my second replay:

connect the recorders XLR-connectors pin 2 as +/hi and pin 1 as ground/screen, and then then link pin 3 to pin 1 (ground/screen)

it was a suggestion to arrange usable interfacing if the signal/cable already was unbalanced/single wired (one lead and screen) in the tape recorder end.

But the best way to arrange this interfacing are:
Use paired cable (two lead and screen) connected (XLR pin 1=screen, pin 2= +hi, pin 3=-lo) from the balanced in and outputs on the tape recorder, and then do the "un-balanced ground link" in the unbalanced console end. (screen and lo cable connected to ground terminal and hi cable to the signal terminal)

This arrange help to balance the cable "semi balanced" between the tape recorder and console, and will help to suppress disturbance as hum and buzz. (if the balanced in and outputs on the tape recorder are of good quality)

Sorry If I complicate the ting, but I will give you a better alternative if you shall re-wiring your sytem.

--Bo

Hi Guys,
I've been lurking around this forum for a while now so I thought I better register!

I have a similar issue to dimebag - I'm interfacing an Alesis HD 24 (+4db balanced) with a Tascam M3500.(-10 db unbalanced - I think?) I recently bought the console s/h and have no documention.

As suggested here I have read the Rane notes on balanced/unbalanced etc and I think I understand the concepts therein But I have a couple of questions specific to the M3500. I hope one of you guys experienced with this console may be able to help me.

Firstly - most of the ins/outs are mono 1/4' plugs - except 2 track in, mic ins and stereo outs - I think I read somewhere that these XLRs are not wired pin 2 hot. Can anyone confirm this? BTW when I connect the stereo out 1/4" jacks to my power amp via mono unbalanced leads(guitar leads) I get an earthloop big time. When I connect the XLR stereo outs to my amp with unbalanced mic leads (XLR to mono plug) - the signal is clean???

Is there a viable way to convert 24 channels of in and outs on the console to +4db. This thread mentioned an external box in regard to db's A&H - but is this available or are we talking DIY. I believe I can do the DIY if someone can direct me to a design schematic

I understand (well I think I understand!) that connecting balanced to balanced with an unbalanced lead can attenuate the signal by 6db. But is it possible to incorrectly connect balanced to unbalanced in a way that needlessly attenuates the signal? That is - so far I've used single core shielded cable with a mono plug at the console end to a TRS at the Alesis with the ring and sleeve bridged. Is there a better way to do this with 2 core cable?

And finally - does it all really matter? It worries me mostly that the 0VU test tone from the console arrives at the Alesis at about -30 dbfs - That same test tone comes back to the console Tape Ins at about +5VU. I can bring it back via the console line ins and trim it - but how do I get it to the alesis hot enough (from the direct outs) with out overdriving the console? Or should there be enough headroom for this not to be a problem?

All of the usual apologies apply for dumb novice questions!!!
Thanks guys
Jeremy H

hi everyone,
i have 24-Channel Mod 3 (actually its the mod 2, i dont know the difference except it has grey knobs instead of couloured ones)console and i have 23 Channels equipped with
additional pcb's to boost the direct out. as i bought it like that, i dont know if this is custommade or a&h-stuff. anyway i could do some photos, but unluckiliy i do not have the schematics of the directout-pcb. but it works.

photos of the pcb's here.
http://loehmann-klaus.magix.net/website;jsessionid=1j14wb09d404s.omaasp32?act=15&pos=0
transistors are BC 107 and BC 177. signal is taken from the postfade-bus.