New guy needing help with vintage mixer

[Mike]

Hi,
A friend of mine from the Synth-DIY group suggested I signup here and
post about my new mixer and the issues I have because of it. I have
just bought a Toa RX-7:
http://www.toaelectronics.com/disc/manuals/RX-7-164_248_328_IM.pdf
http://i108.photobucket.com/albums/n13/somnium7/gear/ToaBoard01.jpg

I plan to use it in my home studio for recording. Problem is that most
of my gear has -10 dB consumer level outputs and the mixer has
floating transformer inputs at standard 1.2K mic impedance. It also
has +4 unbalanced send/recieve for each input.
Now I know plugging in my gear to either of these inputs can be a
noisy situation. I also can't afford to buy 24-32 line bumps. What I
need is a simple and affordable solution. I design and build
synthesizers and have also modified a fair amount of other audio
equipment so I am handy with electronics and soldering. Is there a
simple mod I can make to my input channels to get the levels/
impedances matched?

Or should I do the brute force DIY method and design a multichannel
line bump?
Anybody here tried this?

All advice is very much appreciated.
Thanks!

[Scott Dorsey]

Mike > wrote:
>post about my new mixer and the issues I have because of it. I have
>just bought a Toa RX-7:
>http://www.toaelectronics.com/disc/manuals/RX-7-164_248_328_IM.pdf
>http://i108.photobucket.com/albums/n13/somnium7/gear/ToaBoard01.jpg
>
>I plan to use it in my home studio for recording. Problem is that most
>of my gear has -10 dB consumer level outputs and the mixer has
>floating transformer inputs at standard 1.2K mic impedance. It also
>has +4 unbalanced send/recieve for each input.

So, have you tried it, and is it a problem?

If it is, is this one of the TOA consoles that uses plug-in octal modules
for the input stages?

>Now I know plugging in my gear to either of these inputs can be a
>noisy situation. I also can't afford to buy 24-32 line bumps. What I
>need is a simple and affordable solution. I design and build
>synthesizers and have also modified a fair amount of other audio
>equipment so I am handy with electronics and soldering. Is there a
>simple mod I can make to my input channels to get the levels/
>impedances matched?

Maybe, but you'll need to get the manual for the console. If it's got
transformer-coupled inputs, doing it properly will cost more than bump
boxes will.

If you actually plug everything in, how does it sound?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul Stamler]

"Mike" > wrote in message
oups.com...

> I plan to use it in my home studio for recording. Problem is that most
> of my gear has -10 dB consumer level outputs and the mixer has
> floating transformer inputs at standard 1.2K mic impedance. It also
> has +4 unbalanced send/recieve for each input.
> Now I know plugging in my gear to either of these inputs can be a
> noisy situation. I also can't afford to buy 24-32 line bumps. What I
> need is a simple and affordable solution. I design and build
> synthesizers and have also modified a fair amount of other audio
> equipment so I am handy with electronics and soldering. Is there a
> simple mod I can make to my input channels to get the levels/
> impedances matched?
>
> Or should I do the brute force DIY method and design a multichannel
> line bump?
> Anybody here tried this?

You can make simple pads:

RCA hot -----10k-------------XLR pin 2
|
150
|
RCA gnd----------------------XLR pin 3, shorted to pin 1

If the ASCII art came out okay, you will have a 10k series resistor and a
150 ohm shunt resistor, and you'll short pin 3 to pin 1 at the XLR male plug
going into the mixer. This should work fine, giving you about -45dBu at the
input, just right for a mic input. The one thing you want to make certain
sure is that the mixer's phantom power is turned off, or you'll magnetize
your transformers instantly and probably blow up your synth's output too..

Peace,
Paul

[Mike]

On Apr 8, 5:41 pm, "Paul Stamler" > wrote:
> "Mike" > wrote in message
>
> oups.com...
>
> > I plan to use it in my home studio for recording. Problem is that most
> > of my gear has -10 dB consumer level outputs and the mixer has
> > floating transformer inputs at standard 1.2K mic impedance. It also
> > has +4 unbalanced send/recieve for each input.
> > Now I know plugging in my gear to either of these inputs can be a
> > noisy situation. I also can't afford to buy 24-32 line bumps. What I
> > need is a simple and affordable solution. I design and build
> > synthesizers and have also modified a fair amount of other audio
> > equipment so I am handy with electronics and soldering. Is there a
> > simple mod I can make to my input channels to get the levels/
> > impedances matched?
>
> > Or should I do the brute force DIY method and design a multichannel
> > line bump?
> > Anybody here tried this?
>
> You can make simple pads:
>
> RCA hot -----10k-------------XLR pin 2
> |
> 150
> |
> RCA gnd----------------------XLR pin 3, shorted to pin 1
>
> If the ASCII art came out okay, you will have a 10k series resistor and a
> 150 ohm shunt resistor, and you'll short pin 3 to pin 1 at the XLR male plug
> going into the mixer. This should work fine, giving you about -45dBu at the
> input, just right for a mic input. The one thing you want to make certain
> sure is that the mixer's phantom power is turned off, or you'll magnetize
> your transformers instantly and probably blow up your synth's output too..
>
> Peace,
> Paul


Ok took me a couple days to get to the point where I could make some
tests. I had to tear apart my entire studio and rearrange it to fit
this beast. Nearly all my gear works fine through the recieve jacks -
no noise, good level. The exception is one of my older synths, which
always had a weak output anyway. I'm gonna use Paul's idea here and
pad the output of that synth and plug it to the mic input of a mixer
channel. I'll have alot more gain adjustment options that way.

Thought I might that I am completely in love with this console! It's
absolutely SILENT. I turn the headphones to max and top the sliders on
a dozen channels and hear absolutely nothing. While testing all the
channels with a mic i found myself pleasantly suprised by the sound of
the preamps - very smooth - silky ...and with a sweet vintage tone.
Just fantastic!
Problems are minimal and all things I can fix. First 6 channel faders
are slightly scratchy and I get static from the group one module until
the unit warms up. none of the meter lamps light up - maybe a bad
connector or relay. Of course with the age of this mixer it could very
well be that all the bulbs have failed. Overall, I can sit down and
lay tracks with it right now.

Thanks everybody for the helpful suggestions!
Mike

[ostaz]

Just wondering, what year is this mixer. Are Toa mixers any good...I used
to have some Toa stage 15 inch stage monitors that were just awful. Perhaps
that wasn't their forte.

Pete

[Mike]

On Apr 11, 9:15 pm, "ostaz" > wrote:
> Just wondering, what year is this mixer. Are Toa mixers any good...I used
> to have some Toa stage 15 inch stage monitors that were just awful. Perhaps
> that wasn't their forte.
>
> Pete


Pete,

I have been going through the innards of my Toa and I'm very impressed
with it's construction. I would say that this is a VERY good mixer.
Every channel has good quality Tamura transformers, decent op-amps and
very good Alps faders. The mic preamps sound incredible to my ears. I
found that the preamps and program outputs use a proprietary op-amp
module made by Toa which is not available for replacement. The one
that I suspect to be dead is on a group channel module. Since I have
no use for 8 program channels I am going to canibalize one to repair
the group channel module. Luckily this thing is a breeze to work on.

If you are interested in getting one of these consoles I found one for
sale on Ebay while googling for repair parts. Item #120108053269. It's
not mine btw, you'll have to pry mine from my cold dead fingers.

Mike

[ostaz]

"Mike" > wrote in message
oups.com...
> On Apr 11, 9:15 pm, "ostaz" > wrote:
>> Just wondering, what year is this mixer. Are Toa mixers any good...I
>> used
>> to have some Toa stage 15 inch stage monitors that were just awful.
>> Perhaps
>> that wasn't their forte.
>>
>> Pete
>
>
> Pete,
>
> I have been going through the innards of my Toa and I'm very impressed
> with it's construction. I would say that this is a VERY good mixer.
> Every channel has good quality Tamura transformers, decent op-amps and
> very good Alps faders. The mic preamps sound incredible to my ears. I
> found that the preamps and program outputs use a proprietary op-amp
> module made by Toa which is not available for replacement. The one
> that I suspect to be dead is on a group channel module. Since I have
> no use for 8 program channels I am going to canibalize one to repair
> the group channel module. Luckily this thing is a breeze to work on.
>
> If you are interested in getting one of these consoles I found one for
> sale on Ebay while googling for repair parts. Item #120108053269. It's
> not mine btw, you'll have to pry mine from my cold dead fingers.
>
> Mike

Good luck with the mixer. It sounds like you've got a good one!

Pete