Reel to Reel to Mixing desk - unbalanced to balanced

M

man-bot

New member
I figured I'm not the only one who is in this situation and I thought I would run it by you guys.

I have a Soundcraft series II mixing desk that operates at +4. My Teac 80-8 operates at -10. Ths is my signal chain:

Mics -> Soundcraft -> 80-8 -> Soundcraft -> computer

I have been fighting some hiss issues that I usually just do some high cut to accomodate but I got to thinking about the signals. The signal is leaving my board at +4 (0db VU on the soundcraft is 0db VU on the Teac), but out of the Teac is a -10v signal which i run into the line in of a channel on my mixing desk and trim the level up to where is appropriate. I do this so I can use the EQ on my board - I don't record w/ any EQ.

To me it seems like an invitation for noise to have to reamp the level like this to use EQ... while it hasn't been too bad, I do notice it.

I assume I should be using some sort of balancing interface between the 80-8 and my board... but basically I'm just increasing the levels through a different device.

Am I being crazy? Should this balanced -> unbalanced - > balanced be a cause of noise? Is there a better way to approach this?

For reference when signal is coming back from the 80-8 to the board I have to turn the channel gain up 1/2 way at least (sometimes more). There is at most a 5'-8' run between the 2 units.

Any thoughts on how to get the hiss down as far as signal flow changes?
 
someone with more experience (plenty on this board!) should chime in but my understanding is you should be able to change your soundcraft board internally to operate at -10.
 
There is a 12dB difference between 0 VU on the Teac and 0 VU on the board if one is operating at -10dBm nominal and the other +4dBu nominal. I'd guess it is a level matching issue, not a balanced unbalanced issue, as the board expects a hotter signal coming in, so you are getting the noise by having the ramp up the gain more than you should coming from the 80-8. Also, you didn't indicate what type of interface you are using on the computer. That should be set (and most can via software) for the +4 input.

I'm assuming that the board has XLR's or TRS inputs and that you have the proper wiring from the XLR's/TRS's to the RCA's. If not, Jensen and Rane websites, both have good articles on that. I'll post a link if you need.

If you can jumper the Soundcraft that's great, you have a manual?

The next easiest thing would be to get a Fostex 5030 or a pair of Tascam LA-40 to put between the 80-8 and the board to match the +4 levels. You could also get the passive shifters from Ebtech, but going from -10 to +4 via transformer might get you some impedance matching issues.
 
Having to amplify by 12 dB or so should not be a problem. The limiting factor, by far, will be the S/N of the tape playback signal, not the input noise of your console channels. That is, the signal level of the tape hiss will be much larger than the input noise level of the console channel or the electronic noise level in the tape output signal. 12 dB of gain won't change the relative levels of those noise components. Relax.

BTW, if you plan to use HF EQ boost, you might want to consider recording that to tape, rather than waiting to apply that HF boost at mix time and simultaneously boost the tape hiss.

Cheers,

Otto
 
Heyo - I guess I worded it wrong... I am more concerned with the levels (but it is a matter of the outputs of the 80-8 being unbalanced and operating at -10, if it had balanced outs it would likely operate at +4).

I have an Audiotrak Maya1010 on the computer (which is +4) but there is no issue there as I have that side all set up (board -> computer w/ Reaper running about -12dbFS when the board is 0dbVU... i know that is a bit hot!).

I guess what is most distressing is that I am losing that level only at the 80-8 (+4 in and -10 out, yikes!)... I realize now that I should have something like a Tascam LA-80 inbetween the two to match levels.

What I am most concerned with is how much noise an LA-80 would impart on the signal as opposed to pushing the line ins on my board.

No option to operate the Soundcraft at -10, which is fine... I think I know my answer here! I need some type converter inbetween the 2 to get the levels up... needs to be clean though!
 
man-bot said:
No option to operate the Soundcraft at -10, which is fine... I think I know my answer here! I need some type converter inbetween the 2 to get the levels up... needs to be clean though!
Click to expand...

You can use one, but it's not needed and won't really improve things. Just use the console input gains. Again, 12 dB of gain (-10 dBV to +4dBu) is not going to make a difference in the relative levels of the noise components. The noise level will still be dictated by the tape hiss, and you will determine the signal to noise level by where you set the recorder gain, that is, how "hot" you record onto the tape.

Cheers,

Otto
 
Thanks Otto... that answers that, line in on the Soundcraft it is! Its too bad 12db of gain is lost with the 80-8.

As far as recording levels, I usually keep them aroung 0VU on Teac... of course when recording drums there are some peaks at +3 or more but no distortion...

I really can't figure out my tape hiss issue then, I may have to make some new cables that are 1/4" mono (I modded my 80-8 to have 1/4" jacks not RCA) to XLR and used the transformer based mic ins on the board ot see if the noise levels are better...

I guess its all gain staging...
 
If you're wanting to boost -10 up to +4 I'd suggest the Ebtech Line Level Shifers. They made two-channel boxes and 8-channel reackmounts for a better value than the Tascam LA kits. Some models are 1/4" jack only; others have XLRs too. I use a couple Ebtech boxes for patching -10 aux outs from my console to our outboard gear, pretty much all of which is +4 balanced. They're quiet and they do the job. They pop up on eBay for good prices periodically.
 
man-bot said:
Heyo - I guess I worded it wrong... I am more concerned with the levels (but it is a matter of the outputs of the 80-8 being unbalanced and operating at -10, if it had balanced outs it would likely operate at +4).

I have an Audiotrak Maya1010 on the computer (which is +4) but there is no issue there as I have that side all set up (board -> computer w/ Reaper running about -12dbFS when the board is 0dbVU... i know that is a bit hot!).

I guess what is most distressing is that I am losing that level only at the 80-8 (+4 in and -10 out, yikes!)... I realize now that I should have something like a Tascam LA-80 inbetween the two to match levels.

What I am most concerned with is how much noise an LA-80 would impart on the signal as opposed to pushing the line ins on my board.

No option to operate the Soundcraft at -10, which is fine... I think I know my answer here! I need some type converter inbetween the 2 to get the levels up... needs to be clean though!
Click to expand...

Hard to say on the noise the LA-80 would impart. Note that there was a thread here a while back re I think a MS-16 or 85-16 (can't remember) and the deck itself operated at -10 with amps up and down converting the signal to +4 on the XLR inputs.

You could just get a 48 or 58 with balanced i/o.....

Also, any kind of amp between the 80-8 and the board is going to have its sonic impact. You could build your own using discrete opamps or something.

You could also use the Ebtech's (the trafo might ad some color) also, depending on teh output impedance of the 80-8 and the input impedance of the board, you're using a 1:4 ratio transformer so that *could* be an issue, if the impedance on the board is rather low. Try it out and see what sounds the best.
 
ofajen said:
You can use one, but it's not needed and won't really improve things. Just use the console input gains. Again, 12 dB of gain (-10 dBV to +4dBu) is not going to make a difference in the relative levels of the noise components. The noise level will still be dictated by the tape hiss, and you will determine the signal to noise level by where you set the recorder gain, that is, how "hot" you record onto the tape.

Cheers,

Otto
Click to expand...

So you don't think it's necessary? What about going from a +4 to a -10 mixer? I'm using an LA40 now on mine like that. If I didn't have to maybe I wouldn't. But what do you recommend for the balanced to unbalanced conversion?
 
SteveM said:
So you don't think it's necessary? What about going from a +4 to a -10 mixer? I'm using an LA40 now on mine like that. If I didn't have to maybe I wouldn't. But what do you recommend for the balanced to unbalanced conversion?
Click to expand...

I guess the soundcraft has enough gain, whether with a LA-80 or the line ins, you're still amplifying the 80-8 signal.

I did try to by accident to run -10 from an Otari MX5050 (it's switchable) while aligning it to a Dolby 362 and it really really struggled to make up the gain, actully i couldn't align it, until I switched the Otari back to +4. If the Otari was -10 out, I'd need an amp between it and the Dolby unit if I wanted to use it.

For +4 to -10 you could also use transformers (like the Ebtech) and see how it sounds.

Note that the operating level and unbalance or balanced aren't necessarily the same. The Otari has XLR ins (although they are unbalanced by design can be transformer balanced with an add-on) and it can operate on both levels. The Dolby units, e.g. have transformers so they are balanced.
 
Blue Jinn said:
I guess the soundcraft has enough gain, whether with a LA-80 or the line ins, you're still amplifying the 80-8 signal.

I did try to by accident to run -10 from an Otari MX5050 (it's switchable) while aligning it to a Dolby 362 and it really really struggled to make up the gain, actully i couldn't align it, until I switched the Otari back to +4. If the Otari was -10 out, I'd need an amp between it and the Dolby unit if I wanted to use it.

For +4 to -10 you could also use transformers (like the Ebtech) and see how it sounds.

Note that the operating level and unbalance or balanced aren't necessarily the same. The Otari has XLR ins (although they are unbalanced by design can be transformer balanced with an add-on) and it can operate on both levels. The Dolby units, e.g. have transformers so they are balanced.
Click to expand...

Any difference between using the Ebtec or the LA40? The la 40 uses transformers too right? I also have a soundcraft series 200 with +4 inputs and to be honest the tascam m35 with the LA40 sounds just as good. I've decided to stick with using the M35 for now because it's has few more things I like about it.
 
What model is your Soundcraft? Some of them have interior jumpers to change the operating level from +4 to -10. I can't say which ones but the documentation for yours should tell you how to do it if it's an option.
 
SteveM said:
Any difference between using the Ebtec or the LA40? The la 40 uses transformers too right? I also have a soundcraft series 200 with +4 inputs and to be honest the tascam m35 with the LA40 sounds just as good. I've decided to stick with using the M35 for now because it's has few more things I like about it.
Click to expand...

I can't say for certain, but I'd assume the LA-40 does not have transformer coupled ins/outs. (The Fostex version of the same kind of thing doesn't.) So you're using transistors and resistors to add subtract gain.

The difference is using passive (doesn't use any power) vs active (does use power) amps/attenuators, and what if any coloration is added/not added to the sound by either method. It is simply two distinct electronic methods for arriving at the same thing.

Put another way, balanced i/o can be either "active" or "transformer." (XLR's can also in reality be unbalanced, like my Otari, where the - is tied to ground.)

(You could also have transformer coupled inputs/outputs that do not amp/attenuate, e.g. the Dolby 360's have transformers on either end, and my Otari has provisions for adding a transformer, as did a dbx 180 I had, that makes the i/o "balanced.") The operating level (-10dbm or +4dBu) and "balanced" or "un-balanced" are two separate concepts, although generally -10 gear is unbalanced.
 
Ebtech 8 channel versions work well. I have 2 of them here and have been using them about 5 years. The LA-80's had been discontinued at the time so I could not get them. The LA-80's do have a trim pot so that you can show true 0dB acrosss the whole system.

My brother uses 6 of the LA-80's going to and from his JH24 to a Tascam M3700. They were $3 grand if I recall. The Ebtechs are non powered and deliver a relative signal.

Danny
 
Blue Jinn said:
I can't say for certain, but I'd assume the LA-40 does not have transformer coupled ins/outs. (The Fostex version of the same kind of thing doesn't.) So you're using transistors and resistors to add subtract gain.

The difference is using passive (doesn't use any power) vs active (does use power) amps/attenuators, and what if any coloration is added/not added to the sound by either method. It is simply two distinct electronic methods for arriving at the same thing.

Put another way, balanced i/o can be either "active" or "transformer." (XLR's can also in reality be unbalanced, like my Otari, where the - is tied to ground.)

(You could also have transformer coupled inputs/outputs that do not amp/attenuate, e.g. the Dolby 360's have transformers on either end, and my Otari has provisions for adding a transformer, as did a dbx 180 I had, that makes the i/o "balanced.") The operating level (-10dbm or +4dBu) and "balanced" or "un-balanced" are two separate concepts, although generally -10 gear is unbalanced.
Click to expand...

Looking at the LA manual now. It does use transformers but I think it's just one side (if that makes sense) . I'm having hard time figuring it out looking at the manual but I'm sure I read it somewhere. There is also a switch for running it at -20dBm.

I also have tried the Ampex straight to the M35 and I think with the LA 40 it's pretty transparent. Except for the difference in level there is no noticeable difference in the sound.
 
You can also bypass the output trannies on the 440...I've heard not so becoming things about the 440 output trannies and if you bypass it you drop about 7dB's coming much closer to level-matching the M-35.

I'll be A/B'ing O/P tranny in vs out on my MM-1000...If I end up liking both for different reasons I will convert the LINE TERMINATION switches on the back to serve as transformer insert switches.
 
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