pstamler

Unbalanced-balanced output adapter?
« on: March 30, 2008, 02:25:43 AM »
Could anyone here use a simple adapter to go from unbalanced -10dBV in to balanced +4dBu out? It'd have highish input impedance, a +6dB opamp gain stage, and the output section would probably be a THAT 1646. I'm thinking of designing a quickie board to do this.

If you want this...do you want it stereo, or mono? Or two sections that could be cut apart, a la the Tri-Way power supply? Would you want on-board AC coupling?

Dunno if this really belongs in the Brewery, but it's not on the drawing board yet, and it's not ready to build so it doesn't belong in the Lab, and it's not for sale yet so it doesn't belong in the Black Market. So it's here, getting beer stains on the drawings.

Peace,
Paul


okgb

Unbalanced-balanced output adapter?
« Reply #1 on: March 30, 2008, 02:40:42 AM »
Sounds like a nice utility to have ,
depending on cost  [ you could have them etched
10 to a board or something like that ]
 Of course using an i.c. with a universal footprint
might make it more versitle for some

o.k. i'm in for 2 at least , support the cause
GKB Audio / Greg Boboski

peterc

Unbalanced-balanced output adapter?
« Reply #2 on: March 30, 2008, 05:14:54 AM »
Paul

You could try something like this:

http://1176neve.tripod.com/id6.html

Peter
If opportunity doesn't knock, build a door.

Rochey

Unbalanced-balanced output adapter?
« Reply #3 on: March 30, 2008, 11:27:04 AM »
if there really is demand for one, then don't be suprised if you see one soon on www.expataudio.com :)

Lets see how much demand there is, and how many channels people need per board.

/R
Expat Audio Home: http://www.expataudio.com

barclaycon

Propak
« Reply #4 on: March 30, 2008, 04:27:00 PM »
Quote
Could anyone here use a simple adapter to go from unbalanced -10dBV in to balanced +4dBu out?

There are any number of these things around aren't there ?
We used to call them Propaks.
Little boxes that interface consumer gear (Cassette machines etc.) with the pro world.
I've still got a stack of Audio & Design boxes which were used for just that purpose.

Wow Rochey, you are really pushing that Expat audio thing !
By the way how how are you doing mate ?

sodderboy

Unbalanced-balanced output adapter?
« Reply #5 on: March 30, 2008, 06:43:16 PM »
This box sports high quality German iron, and goes both ways:

http://www.ebtechaudio.com/lls-2des.html

For mini TRS device, consumer DVD, etc. connection it is fabulicious.
Mike

Rochey

Re: Propak
« Reply #6 on: March 30, 2008, 10:52:17 PM »
Quote from: "barclaycon"

Wow Rochey, you are really pushing that Expat audio thing !
By the way how how are you doing mate ?


The DIY side is just a way we can test different subcontractors for metalwork, pcb's etc. (In other words, it's not done for profit).
In a few months, I hope to release complete products -- keep your eyes peeled :)  I think I mentioned what I was working on last time I was in the UK with you guys.

As for me -- I'm overworked and underpaid :)
They put me on Home Audio as well as Pro Audio in the last 6 months. I now spend my travel in Asia, rather than Europe and the US.

The Japanese I like... and my Chinese colleagues are nice too... I just hate the way they drop food out of their mouth onto the plate  :schock:

Ahhh... differing cultures, eh?  :cool:

/R
Expat Audio Home: http://www.expataudio.com

Freq Band

Re: Propak
« Reply #7 on: April 02, 2008, 04:09:48 AM »
Quote from: "Rochey"


I just hate the way they drop food out of their mouth onto the plate...



Long noodles, long life.

=FB=
Facebook is an unfortunate way to receive news, and a good place to receive rumors.

solder_city

Unbalanced-balanced output adapter?
« Reply #8 on: April 02, 2008, 08:37:15 AM »
Quote from: "sodderboy"
This box sports high quality German iron, and goes both ways


passive -10 to +4 'line level shifter' devices debunked by whitlock, reference in this thread:

http://www.groupdiy.com/index.php?topic=300324

SSLtech

Unbalanced-balanced output adapter?
« Reply #9 on: April 02, 2008, 09:21:05 AM »
Audio & Design 'Propak' are what I used to buyto send to and from Cassette decks etc. in the 1980's... -They were about $700 each!!!

Mind you they were bidirectional and had about a 12dB gain trim window (±6dB from nominal +12dB gain...)

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.


sodderboy

Unbalanced-balanced output adapter?
« Reply #10 on: April 02, 2008, 04:32:33 PM »
That Whitlock reference is great info, especially the first paragraph.  It distills the circuit elegantly.

I have been looking at the actual circuit and trying other transformers in similar situations on my bench, so testing response with different loads is part of my procedure.  I will re-check the source impedances of my Mac, MP3, etc.

I have tested and used the Ebtech normalled to IC based consoles and there are never any interface problems; the circuit is well designed.  Source impedances are less than 1K and loads are greater than 10K.  I never tried one in a "vintage load impedance" situation- I'll have to jack one into two Pultecs or something and listen/look for distortion.  They would reflect only a 38 ohm load!
Mike

pstamler

Unbalanced-balanced output adapter?
« Reply #11 on: April 04, 2008, 12:11:04 AM »
I should maybe explain why this came up. I need unbalanced-to-balanced adaptors for a couple of things, including the outputs of the Picocompressors the Audio Construction Club is building, but also for a doohickey I need for some tests. So as usual, many hands make light the load (but so do constant-current sources).

Peace,
Paul

MartyMart

Unbalanced-balanced output adapter?
« Reply #12 on: April 04, 2008, 09:44:08 AM »
I have a Peavey AMR 8 channel -10 to +4 interface amp that's been very
useful .... in fact it could help me out now with "unbalanced" inserts !
But that means unbal -> bal and also bal -> unbal back to the board and I'm
not convinced this makes sense ?
anyone ?
I think that it can be used either way around ... JR ??
Behringer make a fairly cheap but nice DI800 for 8 channels of unbalanced
to balanced also.

Marty.
"Success is the ability to go from one failure to another with no loss of enthusiasm"

pstamler

Unbalanced-balanced output adapter?
« Reply #13 on: April 05, 2008, 12:58:18 AM »
Yes, that'd work for the Pico...but I still need something very specific for my test gear, an unbalanced>balanced adapter with output Z of 50, 150 or 600 ohms. Hence the idea for this boardlet.

Peace,
Paul

clintrubber

Unbalanced-balanced output adapter?
« Reply #14 on: April 05, 2008, 10:39:53 AM »
Quote from: "pstamler"
Yes, that'd work for the Pico...but I still need something very specific for my test gear, an unbalanced>balanced adapter with output Z of 50, 150 or 600 ohms. Hence the idea for this boardlet.

Peace,
Paul

'Test gear' triggers the thought to check schematics of other test gear.
There's for instance such a schematic in the service-doc of the HP8903B (search the Agilent-site, hefty pdf downloads though), it does 600 or 50 (selectable).
So 150 could be added.

Not sure if these topologies would still be OK enough by todays thoughts about the matter, but it'd never hurt to have seen them.

Regards,

  Peter

JohnRoberts

Unbalanced-balanced output adapter?
« Reply #15 on: April 05, 2008, 11:18:39 AM »
Quote from: "MartyMart"
I have a Peavey AMR 8 channel -10 to +4 interface amp that's been very
useful .... in fact it could help me out now with "unbalanced" inserts !
But that means unbal -> bal and also bal -> unbal back to the board and I'm
not convinced this makes sense ?
anyone ?
I think that it can be used either way around ... JR ??
Behringer make a fairly cheap but nice DI800 for 8 channels of unbalanced
to balanced also.

Marty.


Oh yeah.. the old AMR 8ch bump box (IA8410?)... That was designed for interfacing small format (-10dBV) tape machines with our +4 dBu consoles.

Using it in inserts might be useful if you had a -10dBV mixer and were interfacing with +4dBu (balanced) outboard gear located at some distance from the mixer.

I have designed so many boxes I don't recall the specifics of that one. I vaguely recall it might have had trimpots to adjust gain? If so it might be more usable but I can't swear to the trims. I just have a vague recollection of a 2U high light gray box.

If I needed to Bal/unBal an interface I'd be more tempted to standardize on +6dB/-6dB to standardize headroom coming and going.

I am not inclined to add circuitry into insert paths unless problems dictate the need for some help.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

MartyMart

Unbalanced-balanced output adapter?
« Reply #16 on: April 07, 2008, 05:16:21 AM »
Hi John, yes it has 16 "gain" trim-pots on the front and each of the 8 channels
has I/O for -10 to +4 and +4 to -10  :-)
One more of the "unsung heroes" of the AMR range !
I wish that I'd bought a few at the time  :roll:  .... think that I have a parametric
EQ in a 2U rack somewhere too ....

Marty.
"Success is the ability to go from one failure to another with no loss of enthusiasm"

kiira

Unbalanced-balanced output adapter?
« Reply #17 on: April 09, 2008, 08:47:46 AM »
Paul, someone who I'm building some other equipment for asked me for just such a thing a few days ago. He'd want iron on the output though.
I'd build him a 4 or 8 unit rack device.

Kiira

pstamler

Unbalanced-balanced output adapter?
« Reply #18 on: April 09, 2008, 01:05:52 PM »
That'd be a different story, Kiira. To work in my measurement setup, I'm going to need transformerless.

Peace,
Paul

kiira

Unbalanced-balanced output adapter?
« Reply #19 on: April 16, 2008, 05:37:44 AM »
Hi Roger,

Quote
I know Paul needs transformerless connections, but I thought I'd chime in here about transformer outputs.

I have been driving transformers with THAT 1646s for a year or so now with really good results. I drive the primary differentially from the output of the balancing chip (could be SSM2142 as well)

To be completely proper, you need to drive the 1646/2142 input from a simple buffer like a 5534 in a V follower configuration.

But, I have been using these chips without the input buffer for even longer and there is no audible or electrical issues that I have ever seen. So it can be quite simple... An unbalanced 1/4" input jack connected to the 1646/2142 input with it's output driving a transformer. Any 1:1 will work very well. Ie, Edcor WSM600. That explains the box I use to interface my synth rack to my MOTU DAW system.

The only other parts that are needed are the two .1uF power rail bypass caps per chip.

Roger


Roger thank you. This looks like something my guy would like. He likes iron. He's inexperienced but listens and so far his studio is superb. He installed an isolated electrical circuit and grounding first! Where can I source the That chip? Ithink I'd buld him a channel and one of Paul's device when he has it ready and see what he likes.

I've got plenty of signetics 5534s around too.

Kiira


 

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