Tascam MX-80 Repair...

[sweetbeats]

I'm looking into this again.

Please see a thread I put up on the Tascam Analog Forum last year located here.

Since I may be using the MX-80 as a balanced to unbalanced line converter with my M520/58-OB setup I thought it might be nice to have it working right.

Any thoughts on what to check?

[RRuskin]

Putting this device between your board and machine is the wrong application. If you must go +4 into your 58, get a proper 8 channel -10 to +4 converter. (I so happen to have one if you are interested)

Using the 58's +4 inputs instead of -10 inputs does not have any bearing on the machine's performance. Your board is -10 is it not? There is no need to hang a converter on the output unless it needs to feed a +4 only unit.

[Dr ZEE]

Originally Posted by sweetbeats

...I may be using the MX-80 as a balanced to unbalanced line converter...

Originally Posted by RRuskin

...wrong application. If you must go +4 into your 58, get a proper 8 channel -10 to +4 converter....

This may become a very interesting thread. Must watch it!


/respects

[sweetbeats]

Rruskin, I follow you. Look at the oroginal post though...I'd be using the MX-80 to go from the atr to the board. The M520 has a built in 8-channel -10 to +4 balance amp in it. I'd be using that to go to the atr, and that is only if I do end up using the balanced I/O on the 58 long term (i.e. if the cable runs are longer than what I'm comfortable running unbalanced).

So...with that being said, anybody have any suggestions for how I might tweaker my MX-80 back to 100% functionality???

[RRuskin]

Originally Posted by sweetbeats

Rruskin, I follow you. Look at the oroginal post though...I'd be using the MX-80 to go from the atr to the board. The M520 has a built in 8-channel -10 to +4 balance amp in it. I'd be using that to go to the atr, and that is only if I do end up using the balanced I/O on the 58 long term (i.e. if the cable runs are longer than what I'm comfortable running unbalanced).

At what length would you start getting uncomfortable? IMHO - the MX 80 in perfect condition will do more sonic damage than good.

[sweetbeats]

At what length would you start getting uncomfortable?

At the point that signal loss or hum start to become an issue

IMHO - the MX 80 in perfect condition will do more sonic damage than good.

Because of the unnecessary gain and summing circuitry?

I don't recall any TASCAM mixers from that era having +4 conversion on the tape machine returns. Correct me if I'm wrong.

Exactly...that's why I'm devising a +4 to -10 converter...for the tape returns...you are right...the console does not have that

Again, I'm using the M520's onboard 8-channel -10 TO +4balance amp (picture below), but I need something to convert the signal back to -10 coming back from the 58.

[cjacek]

Cory, would something like this help?
http://www.ebtechaudio.com/lls-2des.html

You can get an 8 channel solution for about $200.

----

[RRuskin]

Originally Posted by sweetbeats

At the point that signal loss or hum start to become an issue

Using low capacitance wire with good connectors you'd have to go much longer than 30 feet for that to be an issue.

Originally Posted by sweetbeats

Because of the unnecessary gain and summing circuitry?

Yes.




[

Originally Posted by sweetbeats

B]Exactly...that's why I'm devising a +4 to -10 converter...for the tape returns...you are right...the console does not have that[/B]

Again, I'm using the M520's onboard 8-channel -10 TO +4balance amp (picture below), but I need something to convert the signal back to -10 coming back from the 58.

Even though pointless, you can go into the 58 balanced and come out unbalanced with no problems. The info on the tape is the same either way. Neither your board or machine performs any better @ +4.

[sweetbeats]

Daniel,

Cory, would something like this help?
http://www.ebtechaudio.com/lls-2des.html

You can get an 8 channel solution for about $200.

Yes, that would be a viable option if needed. The other point of this thread though is to try to get my MX-80 working properly regardless of whether or not I use it as a converter, which I think I'm not going to after Rick's points.

Rick,

Using low capacitance wire with good connectors you'd have to go much longer than 30 feet for that to be an issue.

The issue is that this may possibly be the case at some point, and is precisely why I wanted a deck with +4 balanced I/O and n/r units that are also +4 balanced capable. So...

Quote:
Originally Posted by sweetbeats
Because of the unnecessary gain and summing circuitry?

Yes.

Okay. That does make sense to me. Thank you.

Even though pointless, you can go into the 58 balanced and come out unbalanced with no problems. The info on the tape is the same either way. Neither your board or machine performs any better @ +4.

I realize that it would be silly/pointless to go in one type and out another, and even at that I'm not sure what I would have to do when calibrating the deck as Jimmy at Tascam said if you are going to use the balanced I/O, then calibrate it using those inputs and outputs, and then likewise if you are using the unbalanced I/O. Thinking (writing) out loud here...I'm sure the effect would be pretty minimal, but Jimmy was very clear on that point...I guess if somebody was using their deck that way (mixing their input and output circuits), you'd calibrate the deck to the input type you are using and then you'd have to just deal with the slight change in signal level you would see by using the outputs that weren't loaded during the calibration.

Phew!

Okay...This goes back to an age old question of mine though that I'm not sure I've really ever gotten an answer to...The manuals for my Tascam gear (whether it be the 58, 48, M520, PE-40, etc.) each talk about the benefits of the -10 unbalanced line level convention for recording and studio use. This is of course in direct conflict with the market standard today which is that if your I/O isn't +4 on TRS or XLR connectors it is sub-grade consumer level gear, an idea that I have bought into in the past in a big way and am slowly accepting as a falacy (do you agree?) The specs for my 58 and 48 even demonstrate that there is better performance in an area or two when using the unbalanced I/O as opposed to the balanced I/O. So here's my question:

I selected dbx 150X noise reduction units so that I could maintain a balanced signal path if the need arose to do so when recording (due to long cable runs). The 150X's will accomodate balanced or unbalanced signals from -24 to +10 dBv, adjusted via trimmers on the front panel. If it turned out that I would never need to operate the 58 using the balanced I/O, might I get better performance out of Tascam DX-4D's (owing to the potentially cleaner, better-performing -10 unbalanced path, as well as the omission of a level-setting potentiometer)?

[RRuskin]

Originally Posted by sweetbeats

The issue is that this may possibly be the case at some point, and is precisely why I wanted a deck with +4 balanced I/O and n/r units that are also +4 balanced capable.

I'd worry about the 30+ ft cable runs if and when they became necessary. Otherwise, why complicate things?

Originally Posted by sweetbeats

Okay. That does make sense to me. Thank you.

My understanding is that the MX-80 is a microphone preamp. That kind of gain added to a line level signal would scare the crap out of me regardless of how much pad was available to you. It's just the wrong application for that device. I'm not saying it won't work, just that it won't do anything good for your signal.

Originally Posted by sweetbeats

I realize that it would be silly/pointless to go in one type and out another, and even at that I'm not sure what I would have to do when calibrating the deck as Jimmy at Tascam said if you are going to use the balanced I/O, then calibrate it using those inputs and outputs, and then likewise if you are using the unbalanced I/O. Thinking (writing) out loud here...I'm sure the effect would be pretty minimal, but Jimmy was very clear on that point...I guess if somebody was using their deck that way (mixing their input and output circuits), you'd calibrate the deck to the input type you are using and then you'd have to just deal with the slight change in signal level you would see by using the outputs that weren't loaded during the calibration.

The silliness I was referring to was going +4 when there wasn't a need. The signal doesn't care what level it travels on as long as it's a clean path. I disagree with Jimmy - btw. If you had to mix input and output levels, the deck would not care. It would be a small pain the ass, though.

Originally Posted by sweetbeats

Okay...This goes back to an age old question of mine though that I'm not sure I've really ever gotten an answer to...The manuals for my Tascam gear (whether it be the 58, 48, M520, PE-40, etc.) each talk about the benefits of the -10 unbalanced line level convention for recording and studio use. This is of course in direct conflict with the market standard today which is that if your I/O isn't +4 on TRS or XLR connectors it is sub-grade consumer level gear, an idea that I have bought into in the past in a big way and am slowly accepting as a falacy (do you agree?) The specs for my 58 and 48 even demonstrate that there is better performance in an area or two when using the unbalanced I/O as opposed to the balanced I/O.

Market standard often known as hype.

Originally Posted by sweetbeats

So here's my question:

I selected dbx 150X noise reduction units so that I could maintain a balanced signal path if the need arose to do so when recording (due to long cable runs). The 150X's will accomodate balanced or unbalanced signals from -24 to +10 dBv, adjusted via trimmers on the front panel. If it turned out that I would never need to operate the 58 using the balanced I/O, might I get better performance out of Tascam DX-4D's (owing to the potentially cleaner, better-performing -10 unbalanced path, as well as the omission of a level-setting potentiometer)?

Think about it. The less circuitry in the path, the cleaner the path. You need more circuitry to get to +4. They didn't redesign to keep the specs the same. They added on to get the +4 feature. Marketing = hype For convenience sake, I'd go with the DX-4D's but the 150X's would work just as well once wired up properly.

[sweetbeats]

Rick...

Hmmm...

Lots of great food for thought/consideration. Thank you.

I'd worry about the 30+ ft cable runs if and when they became necessary. Otherwise, why complicate things?

Yes. Thank you. I have a tendency to try and setup for less than likely scenarios...takes a lot of time...I think Daniel (cjacek) is likely smiling and shaking his head in an endearing way right now. He's cautioned me in the same way more than once! I enjoy the process, but the gear doesn't get used in the meantime...too much engineering and not enough art, though I like to think that any good artist is part engineer, and any good engineer is certainly an artist!

My understanding is that the MX-80 is a microphone preamp. That kind of gain added to a line level signal would scare the crap out of me regardless of how much pad was available to you. It's just the wrong application for that device. I'm not saying it won't work, just that it won't do anything good for your signal.

You are absolutely right. Thanks. Yes, the MX-80 has a -30 pad, but you are right...it is not the proper application, and you've helped me understand why. Again, thank you.

The silliness I was referring to was going +4 when there wasn't a need. The signal doesn't care what level it travels on as long as it's a clean path. I disagree with Jimmy - btw. If you had to mix input and output levels, the deck would not care. It would be a small pain the ass, though.

Okay...I get you on the silliness comment, and I think all Jimmy was trying to address is that (in response to my "what is the way Tascam engineers intended it to be done" question I was asking him at the time) when you adjust the repro levels on the deck, it is done with a load on the outputs. If you change the load on the output side it will effect the repro level...let me restate that...the load on the output side can effect the output amp's output level. But, yes, as we are both stating it would be a small amount if at all. Jimmy's statement was a specific response to a specific question, and I didn't really make that clear.

[Richard King]

IF you want to do this, Tascam makes the LA-81 (balanced to unbalanced converter) for that purpose. http://www.tascam.com/products/la-80.html http://www.roscorrentals.com/equipme...37;20LA-81.pdf I agree with Rick though. If you aren't doing long cable runs it's a waste of time and $$. I really don't see why Tascam put that capability on the mixer if they didn't make it a two way process.

[RRuskin]

Originally Posted by sweetbeats

Rick...Okay...I get you on the silliness comment, and I think all Jimmy was trying to address is that (in response to my "what is the way Tascam engineers intended it to be done" question I was asking him at the time) when you adjust the repro levels on the deck, it is done with a load on the outputs. If you change the load on the output side it will effect the repro level...let me restate that...the load on the output side can effect the output amp's output level. But, yes, as we are both stating it would be a small amount if at all. Jimmy's statement was a specific response to a specific question, and I didn't really make that clear.

Whether connected via the -10 or +4 outs, there is a load on the output stage of the deck. Whatever the output load, it shouldn't influence the input calibration in the least. You set up your repro and sync 1st, lock them down, and calibrate your record electronics. Me thinks you either misunderstood what Jimmy said or he was doing the old tech support "tap dance and fart" routine for you.

[sweetbeats]

Just bumping this up for one more try...

Never actually got any advice on possible troubleshooting for the problem with my MX-80...anybody?