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Best method for shifting levels from -10 to +4 ?
Old 18th January 2008
  #1
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Best method for shifting levels from -10 to +4 ?

I need to shift a bunch of -10 signals (primarily from synths) to +4. I know of the Ebtech 8 channel line level shifter, but I would like to know if there are any other options that provide more channels of conversion and will not affect the sound (I'd rather do that selectively when I choose). I think there is also a DeskDoctor 24DI box that does the same (24 channels vs. 8). Any other suggestions? I need to maintain the individual ins/outs, so a line level mixer that sums to 2 channels is not that interesting to me.

thanks,

aaeronn
Old 18th January 2008
  #2
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I would wonder if this could be done with passive transformers. A typical DI box does the opposite of what you want - reduces the instrument level down to mic level. If the transformer was wired backwards, it should be able to step the signal up, and also do the balancing & isolation you need.

If you could find the right transformers this could be a very simple DIY job (or easy to find someone to put together for you).

Transformers should be cheap & quiet, and generally benefit a synth sound.

www.jensen-transformers.com/an/an003.pdf
Old 18th January 2008
  #3
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Why go through all that trouble? Can't you just give it more gain? All you are doing is going from .31vrms to 1.2vrms..
Old 19th January 2008
  #4
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And how would you do that? We're talking synths and things that are designed to output -10 at maximum gain - unbalanced. How to get that up to +4 balanced is the question.

There are plenty of line amps with gain (or compressors, eq's for that matter). Some active DI boxes output +4. I know this is High End, but a whole bunch of Avalon U5's or RND Porticos are expensive. (Might be nice though).

I think high end transformers would be an elegant solution - I just don't know if such a product exists already made up.
Old 19th January 2008
  #5
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The Aphex 228 is an eight channel -10 to +4 box. It uses rca connectors for the input side, though. Still might be worth a look.

Regards,

MM
Old 19th January 2008
  #6
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How far away are the synths from the converters/interface?

I'm not an expert so take this advice with a grain of salt.

Are you having trouble when tracking getting the headphone volume up high enough on the synths channel?

If there is no noise/ground loop problem and the volumes are good enough for headphone mixes you could probably just run the synths at -10 and record them fine. Any gain from an external analog amp is going to be noisier than just boosting the numbers in the DAW. Both approaches will bring up the noise floor anyway.

Do you track through a console? My console's insert's are -2 and I can plug synths into the inserts and it works just fine.

If you want to add some mojo from transformers or a preamp that's another story but if you just want clean gain you might not need to do anything at all.

FWIW, I used to use 8 DI's into preamps for tracking a drum module but yesterday I tested plugging it directly into my console's unbalanced inserts and it works fine.

Some food for thought.
Old 19th January 2008
  #7
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Quote:
Originally Posted by Kiwiburger View Post
I would wonder if this could be done with passive transformers. ...
Transformers should be cheap & quiet, and generally benefit a synth sound.

www.jensen-transformers.com/an/an003.pdf
FWIW, Section 2 of the article posted (end of first page) says that you can't do an adequate job of increasing gain from -10 to +4 using a passive transformer alone, an active (amplifier) design is required.

Also, don't Jensen transformers run about $60-80 a piece? (It's been years since I looked) Well, this is the high end forum, but I think that would be about a grand to build an 8 channel device based on Jensen transformers...
Old 19th January 2008
  #8
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Quote:
Originally Posted by aaeronn View Post
I need to shift a bunch of -10 signals (primarily from synths) to +4. I know of the Ebtech 8 channel line level shifter, but I would like to know if there are any other options that provide more channels of conversion and will not affect the sound (I'd rather do that selectively when I choose). I think there is also a DeskDoctor 24DI box that does the same (24 channels vs. 8). Any other suggestions? I need to maintain the individual ins/outs, so a line level mixer that sums to 2 channels is not that interesting to me.

thanks,

aaeronn
Hi,

I use the Ebtech 8 channel units. I have 2 of them. I run ALL of my keyboards through them. The difference in sound is astonishing and amazing to my ears. I will never plug a keyboard direct into a console again.

Tascam makes very nice bump boxes (that's what most call them) which allow you to adjust the true output voltage if you're really nit picky. They are the LA-80 and LA-81. My brother uses 6 of them to get levels up and down to his JH24. Pricey though at 500 bucks each.
Old 20th January 2008
  #9
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Ebtech Line Level Shifter | Sweetwater.com is the only solution I have any experience with and it seems to work without any signal degradation.
Old 20th January 2008
  #10
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Very interesting! That Ebtech is obviously using transformers to bump the voltage up - basically what I was wondering about.

mmcfarlane - thanks for pointing out that Jensem themselves don't recommend using transformers to bump the voltage up. I missed that point.

Obviously, if you use a transformer to bump up the voltage, the current gets reduced. I sort of subscribe to the Rupert Neve idea (from his website) that preamps are all about voltage multiplication - not current multiplication. But obviously if current gets starved, the tone suffers. That's why matching impedance is important.

Interesting that Jensen (who understand transformers) say it can't be done, but Ebtech say it can.

More reviews of the Ebtech please! For or against?
Old 20th January 2008
  #11
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Quote:
Originally Posted by Kiwiburger View Post
Very interesting! That Ebtech is obviously using transformers to bump the voltage up - basically what I was wondering about.

mmcfarlane - thanks for pointing out that Jensem themselves don't recommend using transformers to bump the voltage up. I missed that point.

Obviously, if you use a transformer to bump up the voltage, the current gets reduced. I sort of subscribe to the Rupert Neve idea (from his website) that preamps are all about voltage multiplication - not current multiplication. But obviously if current gets starved, the tone suffers. That's why matching impedance is important.

Interesting that Jensen (who understand transformers) say it can't be done, but Ebtech say it can.

More reviews of the Ebtech please! For or against?
I have no idea how Ebtech bumps the levels. I seriously doubt it is via transformers. I orginally bought mine to bump up to 1.23 +4dBm with a -10 dBv input. My test equipment showed their outputs did not reach that voltage. I called Ebtech and I was told the voltage they will output is relative to the input,whatever that means. But however they do it, I hear the exact opposite of signal degradation. Like I said, I and others that have witnessed the a/b difference in a high quality keyboard sound, have been amazed

The Tascam units, otoh, are powered iirc and evidently use some sort of amplification to reach a true +4 balanced level which, as I pointed out above, can be attenuated. I do know those units must be fine also because my brothers JH-24 sounds freakin awesome and is piped into a Tascam M3700 console without the balancing option. Hence his need for 3 LA80's and 3 LA-81's.

Interesting article on transformers from a company we all know about.Universal Audio
Old 20th January 2008
  #12
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The Ebtech is passive, converts balanced to unbalanced, provides gain and offers hum isolation. The only possible way it can do this is with transformers.

Most synths have plenty of current available (they can drive headphones), so I don't doubt this could work.

I'm just surprised to learn that Jensen don't consider this best practice, and you think they would know.
Old 20th January 2008
  #13
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Quote:
Originally Posted by Kiwiburger View Post
The Ebtech is passive, converts balanced to unbalanced, provides gain and offers hum isolation. The only possible way it can do this is with transformers.

Most synths have plenty of current available (they can drive headphones), so I don't doubt this could work.

I'm just surprised to learn that Jensen don't consider this best practice, and you think they would know.
If I get the chance, I'll pull one of mine out of the rack tomorrow and peak inside. Do you think it's possible they would have 8 transformers inside ? Re the keyboards, I can only describe the sound as seeming more open or maybe unmasked,like a veil was lifted. Also focused and polished. But I don't know why. But a transformer might explain it.
Old 20th January 2008
  #14
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Quote:
Do you think it's possible they would have 8 transformers inside ?
I would put good money on it. I would expect them to be input transformers - possibly in little round metal cans, not the typical output or power transformer shape.
Old 20th January 2008
  #15
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Found an old SOS artical by Paul White - he says they are high quality transformers -

Studio Essentials

I might have to get one. I would probably buy the 2 channel boxes, and have very short unbalanced cables to the synth.

I have 4 Radial JDI boxes, but they need a preamp. I like the idea of driving my converters with just a tranny in between. Preamps can add nice color, but always more noise. Another option would be good.

I find transformer isolation essential to get rid of hum. (The AC to my keyboards is just an extension cord and multibox - no star grounding i'm afraid).
Old 20th January 2008
  #16
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Quote:
Originally Posted by Kiwiburger View Post
Found an old SOS artical by Paul White - he says they are high quality transformers -

Studio Essentials

I might have to get one. I would probably buy the 2 channel boxes, and have very short unbalanced cables to the synth.

I have 4 Radial JDI boxes, but they need a preamp. I like the idea of driving my converters with just a tranny in between. Preamps can add nice color, but always more noise. Another option would be good.

I find transformer isolation essential to get rid of hum. (The AC to my keyboards is just an extension cord and multibox - no star grounding i'm afraid).
You were right wern't you. Good call.

Hehe. Yeah people thought I was a fruitcake for spending so much money on a 20 amp Furman balanced isolation transformer for my room, which btw, I just managed to pay off before the interest kicked in at 1 year. I just love zero percent financing for a year.

But I've been there, done the hum thing, and I'll never go back. And I do agree that hum on keyboards can be real problematic also. I have one of the 2 channel Ebtech boxes also, which was the first I had ever used. I bought it for use on my Otari 2 track because either the insits or outsits are unbalanced (on mine). Prolly the outputs. I don't remember the 2 channel Ebtech costing very much. But I seem to remember paying close to $500 for the 2- 8 channel versions. Maybe you could try one of the 2 channel boxes and see if you think it makes a difference on keyboards.
Old 20th January 2008
  #17
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I've just ordered the 2 channel XLR box from Frontend - i'll be interested to hear it.

This might work backwards as a stereo reamp box too. Unlike a DI box, the gain structure would be going the right way. (I've got a couple of Reamp boxes anyway, but options are good).

Interfacing semipro unbalanced stuff is a regular pain - I could have lots of uses for this. Thanks for the heads up.
Old 20th January 2008
  #18
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Quote:
Originally Posted by Kiwiburger View Post
I've just ordered the 2 channel XLR box from Frontend - i'll be interested to hear it.

This might work backwards as a stereo reamp box too. Unlike a DI box, the gain structure would be going the right way. (I've got a couple of Reamp boxes anyway, but options are good).

Interfacing semipro unbalanced stuff is a regular pain - I could have lots of uses for this. Thanks for the heads up.
''

You'll most likely want to get a 2nd one. Don't blame me, ok ?
Old 20th January 2008
  #19
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Quote:
Originally Posted by Kiwiburger View Post
I've just ordered the 2 channel XLR box from Frontend - i'll be interested to hear it....
Please let us know how it works. I may want something like this for my Roland TD-10W 8-channel drum module. Today it works OK plugged into 01V96 inserts but I'm upgrading to an Aurora16 and 'doing it right' and running longer balanced cables is attractive for $249.
Old 20th January 2008
  #20
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There are also devices made by Valley People and Studer. The Studers are modular. Have a look on the used market.
Old 13th February 2008
  #21
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ok - I was the one that originally started this thread so I thought I would pop back in with an update. I decided to get the ebtech LLS8 (1U 8 channel unit) from sweetwater - for 250$. I needed all 8 channels so it seemed like the best bang for the buck. Currently I'm using MOTU interfaces (HD192, 24IO and a 2408mk3), but will be going Apogee in the future. I figured since the MOTUs are switchable between -10 and +4 (except the 192 which is fixed at +4) that I would get everything running at +4 now so I could just swap out the interfaces and a few cables and be back up and running quickly.

What I am hearing is not what I expected. Now, I'm fully willing to admit I have done something stupid, but I figured this would be a no brainer. After I wired everything up and switched the appropriate interface inputs to +4, the meters for those inputs are only reading -24 when I have my synths at full volume. When I was running at -10 and the keys were plugged in without the LLS, I could reach between -6 and 0 on the meters (or very close). I need to double check my wiring of course (I just put it in tonight) but I was expecting to see a much stronger signal. Anyway, I'll post another update as soon as I've spent some more time looking things over.

Don't take this as a knock against ebtech - I've used their hum eliminators before and they certainly did the trick - not to mention others in this thread have had success with the line level shifters. I'm simply relaying what I'm seeing.
Old 13th February 2008
  #22
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Quote:
Originally Posted by aaeronn View Post
...What I am hearing is not what I expected. Now, I'm fully willing to admit I have done something stupid, but I figured this would be a no brainer. After I wired everything up and switched the appropriate interface inputs to +4, the meters for those inputs are only reading -24 when I have my synths at full volume. When I was running at -10 and the keys were plugged in without the LLS, I could reach between -6 and 0 on the meters (or very close). I need to double check my wiring of course (I just put it in tonight) ...
Maybe the labels on the back panel of the Ebtech are reversed and you are attenuating rather than boosting...

I hope its something that simple. I just bought the same device but haven't had a chance to take it out of the box yet.
Old 13th February 2008
  #23
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My 2 channel Hum Eliminator and Line Level Shifter arrived a few days ago, but I haven't had a chance to test them yet. I got the XLR versions - if you got the TRS versions you would have to make sure you are using TRS cables, or you would be just getting half the signal.

But i'm surprised at your comments - maybe I've got this wrong, but it seems like you are saying your interface already had a -10 setting, which you could drive to 0 directly with your keyboards? So why do you want a Line Level Shifter again?

By setting your interface to receive a +4 input, you have added 12dB of headroom. I'm wondering if you have the LLS around the wrong way? Being a passive transformer, it will pass signal both ways, but obviously will work as an attenuator if used backwards. I plan to test this feature as a stereo reamp option.
Old 13th February 2008
  #24
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Quote:
Originally Posted by aaeronn View Post
ok - I was the one that originally started this thread so I thought I would pop back in with an update. I decided to get the ebtech LLS8 (1U 8 channel unit) from sweetwater - for 250$. I needed all 8 channels so it seemed like the best bang for the buck. Currently I'm using MOTU interfaces (HD192, 24IO and a 2408mk3), but will be going Apogee in the future. I figured since the MOTUs are switchable between -10 and +4 (except the 192 which is fixed at +4) that I would get everything running at +4 now so I could just swap out the interfaces and a few cables and be back up and running quickly.

What I am hearing is not what I expected. Now, I'm fully willing to admit I have done something stupid, but I figured this would be a no brainer. After I wired everything up and switched the appropriate interface inputs to +4, the meters for those inputs are only reading -24 when I have my synths at full volume. When I was running at -10 and the keys were plugged in without the LLS, I could reach between -6 and 0 on the meters (or very close). I need to double check my wiring of course (I just put it in tonight) but I was expecting to see a much stronger signal. Anyway, I'll post another update as soon as I've spent some more time looking things over.

Don't take this a knock against ebtech - I've used their hum eliminators before and they certainly did the trick - not to mention others in this thread have had success with the line level shifters. I'm simply relaying what I'm seeing.
I had the exact same problem in my studio. I have DJ's bringing turntables in and needed a way to get the -10 rca output up to a balanced +4 and into the console patchbay. I purchased the 2 channel ebtech device fully expecting to plug and go (i assumed it had step up transformers inside) and, I don't know why, but it only bumped up the level minimally, nowhere close to where it should have been unfortunately. Tried wiring it every which way and contacted ebtech to get a spec sheet or some more precise info on whats happening inside but to no avail. I mean there is realy only one way to wire it.

I took them back. I went back to using two Avalon DI's.
just my 2cents
Old 14th February 2008
  #25
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Quote:
Originally Posted by Kiwiburger View Post
My 2 channel Hum Eliminator and Line Level Shifter arrived a few days ago, but I haven't had a chance to test them yet. I got the XLR versions - if you got the TRS versions you would have to make sure you are using TRS cables, or you would be just getting half the signal.

But i'm surprised at your comments - maybe I've got this wrong, but it seems like you are saying your interface already had a -10 setting, which you could drive to 0 directly with your keyboards? So why do you want a Line Level Shifter again?

By setting your interface to receive a +4 input, you have added 12dB of headroom. I'm wondering if you have the LLS around the wrong way? Being a passive transformer, it will pass signal both ways, but obviously will work as an attenuator if used backwards. I plan to test this feature as a stereo reamp option.
I definitely have TRS cables on the +4 jacks running to the interfaces - checked that. I wanted the shifter because I'll be upgrading my interfaces to units that only run at +4 and I didn't want to spend for a bunch of preamps or a mixer. I also checked the labeling by swapping cables, which attenuated the signal (as expected) so the labels are correct. Even though the meters are reading low, the volume for a couple machines is acceptable though not great. The one that really suffers though is the Future Retro 777 - far too quiet. I'll just run that one through one of the Pacifica DI jacks - that works quite well
Old 14th February 2008
  #26
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Hmmm - this probably confirms the Jensen info that suggest it's not really feasible to boost with a passive transformer. Logically, current has to suffer if you boost voltage. I see Jensen market a Pro-to-consumer level transformer, but only for going in the reverse direction.

Have you tried using headphone outputs? They might have more current to drive them.

It's about time keyboard makers put damn balanced outs on keyboards. They are probably saving only a few dollars by leaving them off.
Old 17th February 2008
  #27
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Quote:
Originally Posted by Kiwiburger View Post
Hmmm - this probably confirms the Jensen info that suggest it's not really feasible to boost with a passive transformer. Logically, current has to suffer if you boost voltage. I see Jensen market a Pro-to-consumer level transformer, but only for going in the reverse direction.

Have you tried using headphone outputs? They might have more current to drive them.

It's about time keyboard makers put damn balanced outs on keyboards. They are probably saving only a few dollars by leaving them off.
Haven't tried headphone outputs (I'd rather stick with the individual outs). Balanced outs are starting to show up on newer synths, so perhaps they are getting the hint.

The end result of this exercise : the LLS8 is being returned - it's just not working well enough in *my* environment (YMMV) to justify keeping it. I'll be investigating DI boxes next and possibly a couple of used preamps to run the keys through instead.
Old 17th February 2008
  #28
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you gotta amplify your signal so you need power.

whichever way you look at it a passive transformer design just won't do it. you can't magic more current / voltage outta thin air man. you're gonna need some gain to get what you want and gain = juice.
Old 18th February 2008
  #29
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Well hopefully the LLS8 will work for my application from a Roland TD10 drum head to Aurora16 converters. I can select -10 or +4 on the converter so I don't need any voltage boost and at least I should get ground isolation and balancing from the Ebtech box.

I can't test this until Lynx ships the AES16e card (soon I hope) and returning the Ebtech LLS8 isn't an option since the shipping cost to where I live essentially exceeds the cost of the LLS8, at least by courier.

Although I already have an 8 channel active DI for the drums for live use, I didn't want to add 8 more preamps to my studio just for this drum module.
Old 29th January 2015
  #30
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BUMP...

iam trying to figure out why my Apogee AD16x is recording very low levels from all my analog synths... from what i read (and almost understood) it seems like profesional A/D converters (+4dBu) are almost inherently incompatible with like 80% synthesizers (-10dbV)...

i took all my savings and jumped from budget MOTU 828Mk3 straight into the legendary Apogee AD16x/DA16x and now iam figuring out i will probably have to sell the Apogees back on Ebay, because i mainly do synth heavy & electronic music and level-matching all my analog synths to Apogee would mean rebuilding whole home studio, 2x more cables and a bunch of other hardware worth thousands of USD to only match synths levels with the Apogee to get a good sound into my DAW... i dont think its worth for me...

2x Ebtech LLS-8 (16 channels) looked like the missing link in my synth heavy setup...

but i get the outcome of this thread is that Ebtech LLS-8 is essentially a piece of junk that claims to do something that is impossible physically to happen in passive device and that is amplify -10dBV to +4dBu...

Radial is selling 2 channel -10dBV to +4dBu amplifier (Radial J+4) which is fully ACTIVE and costs 220 USD for 2 channels...

but i would have to spend 1800USD to level all my synths (16 channels) with my +4db INPUT Apogee AD16x...

Ebtech claims to do the same trick as Radial passivelly for 290 USD for 8 channels... thats 3x cheaper...

is that a 3x times bigger marketing bull*hit from Ebtech ? why would anyone buy Radial J+4 if you could do the same trick with Ebtech at 8 channels for 290 USD...

there is a couple threads asking about Ebtech LLS-8 and LLS-2... ussually without answers... lets solve this Ebtech myth once and for all... are these boxes worth anything ? or its nonsense claims...

anyone here had good luck matching their synths with a professional A/D using Ebtech products or are they just junk ?

i read here that the boost necessary between -10dBV to +4dBu would have to be 11.79dB... is that really feasible with passive transformers for 290 USD on 8 channels ?

Last edited by mizpulyn; 29th January 2015 at 02:03 AM..
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