UA 2192 Converter - PROBLEMS!!!

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khstudio

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Well,
I spoke with support today & he would not let me talk to the tech :sad:

It seems others don't have or see this as being a problem.

He asked me to email the issue in detail so I sent this:

Hello,
Here's a link to the topic related to & describing this problem.
It's on the LAB, Prodogy Pro Forums.

http://www.groupdiy.com/index.php?topic=24239

To sum up the problems:

My console doesn't like the DC being applied to it's output & causes distortion & degrades the sound.
I HAVE figured this part of the problem out - There is NO coupling cap between the output of my console & the CONTROL ROOM (FET) SWITCHING CIRCUIT.
There is however a coupling cap protecting the final stage before output (Fader Booster amp)... which DOES come before the FET switching to protect it under NORMAL circumstances.

This is where the problem lies... MOST equipment does not have DC @ their INPUT.
And when they do, THEY usually compensate & protect other equipment by using an AC coupling cap or transformer.

*My BIGGEST concern:*

ALL of my other PRO equipment that has differentially balanced outputs - their FINAL output coupling caps have the *+ side of the cap* facing their Op-Amp...
*So the DC coming from the UA 2192 is hitting the WRONG (-) (Negative) side of the caps... which can degrade sound quality & possibly damage the caps.*

I'd like to know why UA would put out a piece of PRO equipment, knowing this would happen & if you are even aware of it & the possibility of damaging or degrading the sound of other devices in the process?

Thank you,

We'll see :roll:
 

khstudio

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I ran a LOT of tests tonite & most are looking good. I also spoke with Dave Derr from EMPIRICAL LABS & Scott Dorsey - both were pretty shocked & felt this could be problematic with certain gear. They both mentioned transformers & coupling caps but in the case of the FATSO... it has a DC coupled output & the DISTRESSOR has caps... (with the + side facing out... so that helps).

The FATSO pulled the 2.3 volts DC down to about 50mv (pin 2 & 3) Dave told me to test for this & said anything under a few hundred mv should be OK... so this looks good for the FATSO.

I also wired up some trannys so I could test - Patching them in between my console & the UA.... then the FATSO & UA.

I have to be honest... they BOTH sounded GOOD!
The tranny added some flavor (in a cool way) but all in all there was no drastic change for the worst either way.
The tranny WAS blocking all DC too... no popping.

So this makes me feel better.

The ONLY problem I'm left with, that still exist is when the UA is plugged into my consoles master out it still distorts the control room & 2 trk returns. When I put the tranny between the console & UA it sound NORMAL.

This is very strange because I took the advise of SEVERAL people to put some coupling caps in line between my boards output & the UA input... THIS DID NOT WORK! It DID stop the popping, but STILL ruined the sound of the control room. It MUST be getting into something else OR messing with the GROUND of the board.

I tied pin 3 to GND then put caps between the two pin 2's... with the + of the cap facing the UA.

This one stumps me.
 

Sorr

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Anyway I still think that a good quality transformer, as made by Sowter etc, connected as I suggested will be sonically better than a 220 mfd or 470 mfd electro with a 10 mfd polyprop across it.
Caveat; Bypassing Electo's with film( an old HiFi trick from the early 80's) caps usually brings out the worst from both, it takes a lot of time experimenting with different brands and values to get the right combination.
 

thermionic

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Correct me if I'm wrong, but IIRC, 2-3v DC is way too much for any Sowter transformer that I know of. You'll magnetise it.

Be thankful that your inputs didn't emit +52v... My soon-to-go-on-Ebay RME FF did... RME paid the designer of my one-off preamp which was killed by it (I could've fixed it myself, but I don't like to go rustling around in one-off pieces made by pro designers) to repair it, but never admitted fault.

This is from the actual thread at GS, it should make you laugh:
Written by Thermionic
Quote:
Do you think it’s ok to have 50v from a line input under ANY CIRCUMSTANCE?

Written by RME Support
Quote:
Now this is where we have a semantics issue. The FF400 manual defines 1&2 as Microphone or Mic/Line inputs. Here's a quote:

27.2 Microphone / Line Front
The balanced microphone inputs of the Fireface 400 offer an adjustable gain of 10 dB up to 65 dB. The soft switching, hi-current Phantom power (48 Volt) provides a professional handling of condensor mics. The usage of a hi-end integrated circuit (PGA 2500) guarantees outstanding sound quality, stunning low THD, and maximum Signal to Noise ratio in any gain setting.
The two combo jacks also allow for the usage of mono and stereo TRS jacks. These jacks usually carry line level signals. To adress this correctly, the input gain can be lowered to 0 dB. The inputs are still operating servo-balanced, but can now handle levels up to +10 dBu.

Elsewhere it says: "Phantom power (48V) can be selected for each microphone input separately."

:shock:

http://www.gearslutz.com/board/moan-zone/90814-rme-fireface-400-users-must-read.html


BTW - I don't always agree with him, but Fletcher put it perfectly when he described RME as 'Real Mediocre Engineering'. I must have had less than 2 hours' worth of use out of the FF400. It sits in a box doing nothing... I'm worried that I'll get bad feedback if it goes on Ebay, even though it's a replacement unit with less than 2 hours of use...

Sorry to hijack your thread! Why don't the OEMs just take it on the chin?


Justin
 

peterc

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I tied pin 3 to GND then put caps between the two pin 2's... with the + of the cap facing the UA.

This might be worth a try.

They way I've always wired an unbalanced out to balanced in, is unbalanced hot to balanced pin2, unbalanced gnd to balanced pin 3. Probably need the caps in line as well.

The converter will pick up the studio gnd via its outputs or mains earth.

Peter
 

Sorr

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Justin, I agree that 2-3 VDC would be troublesome for the Sowter transformer, but,
"2 VOLTs of DC - measured from GND to pin 2 or 3
50mv of DC from 2 to 3 (+ to -) "
If you connected it across 2 & 3, the Bal audio out, it is only 50mV.

You shouldnt have to do this in the first place.
I cant understand how a commercial product could be sold with the DC conditions you describe, it must be faulty!!??
If it was my unit, I would return it to UA and tell them to fix it or send me a refund.
 

khstudio

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I'm trying to deal with this issue but it's just been sucking the creative life out of me. :sad:

I spoke with Dave Derr again from Imperial Labs. He told me to open my FATSO, hook it up to the UA & check the DC @ the output XLR's (Pin 2 & 3)
He wanted to know if it went down. The FATSO is DC coupled, Balanced out.

The voltage went down to 50mv... after telling him this, he said the 2v DC was probably a high impedance voltage & could be easily moved around or pulled down (I don't know enough to understand this).

UA hasn't & won't help me or comment.

The converter does seem to sound OK... I'm just concerned about different devices & their output cap direction.

As a consumer, I don't feel I should have to deal with this... & if my boards control room output wasn't affected by it , I never would have noticed. :roll:

Adding caps stopped the popping & DC in my board but DIDN'T stop the bad sound... only a tranny & completely disconnecting it worked. (or having the FATSO on the out put, where it normally is, stops the DC from reaching my board because it's handling it... until I hit the TRUE-RELAY-BYPASS on it :? )
The tranny sounded nice but was colored... which I may not want all the time on the output of my console. I'm contemplating some nice Jensen's.. but not sure what's optimal? My console uses 5532's for the output driver.

At least I've made people aware of this but it seems your rolling the dice when connecting to different gear in the studio... not something I want to think about when I'm trying to make music. :mad:
 

khstudio

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[quote author="Samuel Groner"]There's something goofy about the capacitor not working. So what are the voltages on both sides of the cap?

Samuel[/quote]

With pins 1 & 3 joined
& a 470uf/10v cap between both pin 2's (+ facing UA)

.951 volts DC Before cap
.0 after

Like I said it stops the popping & DC but still affects the control room signal.

CORRECTION :!:

The CAP DOES HELP... & doesn't make the CR sound nearly as bad as without it BUT it's NOT 100%... like the tranny or completely removing the UA from the boards output. - it's probably passable... but just annoying.

Just to make sure here:
2 caps in series (which it what's happening here) "Halves" the value of both caps???


Now... I have 2 control room inputs, A & B. One comes from my UA 2192 out & the other my CD player. I DID try pulling the UA from the other 2TRK return but still... with the UA connected to my boards output... listening to the CD player thru the 2TRK return doesn't sound as good as when the UA is removed. The tranny was the ONLY thing that matched totally removing it... & after additional listening today, the cap in line wasn't bad.

I agree... it's strange. :?

I've looked over the schematic of my board SEVERAL times & the DC shouldn't reach anything except for the switch that sends the main out to the control room FET switching. There IS a cap after the FET switch.

So the fact that it even sounds bad without these mods or disconnect is weird to say the least... it must affect the GND somehow. :?
 

Martin B. Kantola

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[quote author="khstudio"]With pins 1 & 3 joined & a 470uf/10v cap between both pin 2's (+ facing UA)[/quote]

Seriously would recommend using a polypropylene cap in parallell with the electrolytic! Try 1uF or so. Could help the sound quite a bit. Closer to that 100% at least... The better the caps, the better it will sound.

Martin
 

MHanson

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Why am I not surprised by UA's lack of support?

I had an issue with their 2176's phantom power not powering up one of my mics. They admitted a fault at one point with their unit but said they fixed it after serial #?? and mine was beyond that . . . so guess what . . . end of conversation basically.

I've left that alone, but I was thinking about buying their 2192 this week. I'm glad I saw this. I don't remember hearing any kind of problem last time I used one, but if there's a fault that could kick me later, I'm glad I know about it now. I suppose it's time to go shoot-out converters again. Maybe I'll find something else I really like.

Michael
 

khstudio

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[quote author="Martin B. Kantola"][quote author="khstudio"]With pins 1 & 3 joined & a 470uf/10v cap between both pin 2's (+ facing UA)[/quote]

Seriously would recommend using a polypropylene cap in parallell with the electrolytic! Try 1uF or so. Could help the sound quite a bit. Closer to that 100% at least... The better the caps, the better it will sound.

Martin[/quote]

It's NOT the sound of the boards OUTPUT with the cap that I'm referring to... it's the way the UA f*#ks with my control room monitoring... whether it be the MIX or 2TRK returns.

As I said... the cap DOES help that situation.
 

khstudio

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[quote author="MHanson"]Why am I not surprised by UA's lack of support?

I had an issue with their 2176's phantom power not powering up one of my mics. They admitted a fault at one point with their unit but said they fixed it after serial #?? and mine was beyond that . . . so guess what . . . end of conversation basically.

I've left that alone, but I was thinking about buying their 2192 this week. I'm glad I saw this. I don't remember hearing any kind of problem last time I used one, but if there's a fault that could kick me later, I'm glad I know about it now. I suppose it's time to go shoot-out converters again. Maybe I'll find something else I really like.

Michael[/quote]

YES it sucks BUT... this converter does sound very good.

Companies & people with big heads NEVER turn out to be a good thing.

I have THOUSANDS of $$$ of UA equipment - EVERY UAD Plug & 4 cards + this 2192.

Even though I like this thing I'd definitely go with the LAVERY BLUE OR GOLD if I had to do it over & ESPECIALLY after seeing how they treat their high end customers... this is NO TOY :!:

If they just let me talk to a REAL TECH he could have probably answered all or most of my questions & given me reasons why & possible directions on how to fix it... right from the horses mouth.

Sorry for my rant :sad:
 

Samuel Groner

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It must affect the GND somehow.
You might try to disconnect pin 1 then. If that helps, use a 100 nF in series with 47 ohm for pin 1.

Just to make sure (no time to re-read all your writing): you now have a cap both for pin 2 and 3 and the interconnect is balanced?

Samuel
 

khstudio

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[quote author="Samuel Groner"]
It must affect the GND somehow.
You might try to disconnect pin 1 then. If that helps, use a 100 nF in series with 47 ohm for pin 1.

Just to make sure (no time to re-read all your writing): you now have a cap both for pin 2 and 3 and the interconnect is balanced?

Samuel[/quote]

:thumb:
 

Martin B. Kantola

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[quote author="khstudio"]It's NOT the sound of the boards OUTPUT with the cap that I'm referring to... it's the way the UA f*#ks with my control room monitoring... whether it be the MIX or 2TRK returns.
As I said... the cap DOES help that situation.[/quote]

OK, sorry, didn't read your post properly. If you indeed have a cap on pin 3 of the UA as well (as Samuel asked), then it's very odd, because no DC should be entering your mixer. "Messing with the ground" equals HF problems or a simple ground loop to me.

Try disconnecting one pin at a time while you're listening to your CD on the 2trk, we might as well get to the bottom with this properly since we've come this far. Also try powering on and off the UA while listening.

Martin
 

khstudio

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I DON'T have a cap on pin 3... this was JUST suggested by Samuel.

As I said
khstudio wrote:
With pins 1 & 3 joined & a 470uf/10v cap between both pin 2's (+ facing UA)

I think this is a good test & will try it soon:

Boards GND thru CAP to UA (-) input

Boards (+) thru CAP to UA (+) input

Then FLOAT the UA GND (No Connect)


This SHOULD give total separation like the Tranny.

QUESTION :idea: :

I just built the ULTRA GSSL & use it a lot for my Master Buss Compression.
The output section is the same as Jacobs & the output caps have (-) facing OUT.
Can I flip these or should I use BiPolars (Non Polar)
:?:
 

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