• From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Topic: FF800 Pre-Amp problem

Hi all,
I have just discovered that one of pre's in my FF800 (Channel 9) has an issue and is not working correctly.

I inadvertently plugged a patch lead from from patchbay into the FF pre whilst the phantom power was on. Now, not too much of an issue, except that the patch was already loaded with 48v from an avalon 737sp.
So now, I have a whole lotta garbage noise in that channel, when ever I plug in a condenser mic. Works fine with phantom power off and a dynamic plugged in.

Is it possible that I've a buldged or blown a capacitor within? ... If this is the case, I'd be able to repair it. (it's a long time out of warranty and I can't be without one for more than a day or so).

Any ideas folks?

Regards,
Matt

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Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
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mattrixx's Website

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,849

Re: FF800 Pre-Amp problem

Not capacitor, I would expect one of the protection diodes to be blown. That perfectly explains why it still works without Phantom power. But repairing is complicated. You will have to disassemble the whole front to gain access to the diodes...

Regards
Matthias Carstens
RME

MC's Website

3 Reply by mattrixx (edited by mattrixx 2010-08-23 10:13:46)

  • From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Re: FF800 Pre-Amp problem

Hey thanks for getting back Matthias...
I should probably also have mentioned that I still get mic signal too. (with the phantom power enabled) It's just that there is a a lot of noise, similar to a really really dusty vinyl record going around at 33rpm's. (this is the best and most accurate description of what it sounds like).  This noise increases with the gain control.

Does this still sound like a diode to you? As I mentioned, a dynamic works and sounds clean and fine.

Oh and do you think my lil' patching error would have caused this, or is it some sort of coincidence? I'm leaning to the former. ;-)

One thing the thought of sending out for repairs has brought to light is my dependency on Totalmix and my studio routing. I don't know what I'd do without my FF800 these days. :-)
Regards,
Matt

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Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
----------------

mattrixx's Website

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,551

Re: FF800 Pre-Amp problem

Regardless of what might have caused the problem (48V at the input sounds like a possible cause), if the FF is installed in a rack in your studio and not used as a mobile interface, why not just grab an inexpensive (second hand) external phantom power supply for this channel and live with that for now...? You can still send in the unit sometime later, while you're on holiday or whatever.


Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

  • From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Re: FF800 Pre-Amp problem

Aha!! Daniel.... dammit, why didn't I think of that!! ;-)     Still wouldn't mind knowing a little more about it. Might have a look over the next weekend or something.... Just curious!!

----------------
Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
----------------

mattrixx's Website

  • From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Re: FF800 Pre-Amp problem

I had a little time this afternoon to take the FF800 out and have a little look.  I couldn't see anything obvious that related to my problem, but did notice a bulging cap in the power supply, but pretty certain it's not related to my direct issue.


Here's the swollen cap on the p/s.

https://skitch.com/mattrixx/rxtnr/ff800-power-supply

Here's the area o concern around the channel 9 pre-amp. (note I didn't go so far as to take out the main board to check underneath).

https://skitch.com/mattrixx/rxtnt/ff800-main-board

I am trouble finding out who can fix it in my area. I spoke to our local retailer and he mentioned he contacted the distributor in Sydney Australia, but I still haven't received any info and it's been a while.

Regards,
matt

----------------
Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
----------------

mattrixx's Website

7 Reply by MC

  • MC
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Re: FF800 Pre-Amp problem

No parts underneath. If the noise is only when swithing on 48V, then the input caps (47µ) have leakage, or the resistors and the on/off transistor for the 48V are defective (noisy).

Regards
Matthias Carstens
RME

MC's Website

  • From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Re: FF800 Pre-Amp problem

Mmm, yes Matthias, that sounds like the scenario. The resistors are surface mount, so I pray it not those, but I can certainly swap out the other components. You are right in that phantom power is noisy, but it is only noisy when a condenser mic is connected. When plugging a dynamic, it can be either on or off, with no noise. (but I guess that's obvious).

Thanks again for the quick response,
Regards,
Matt

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Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
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mattrixx's Website

9 Reply by wal (edited by wal 2011-02-18 09:35:41)

  • wal
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  • From: Derbyshire, UK
  • Registered: 2010-09-16
  • Posts: 99

Re: FF800 Pre-Amp problem

It may be the same fault I had with my Fireface 800 as the symptoms sound identical?
If the channel still works when the phantom is off but is desensitised (quieter), and then hissy and noisy when the phantom is on.
Then you might take a look at a low value resistor (part of the input protection circuity) near the XLR socket. In my case the SMD resistor had gone open circuit and therefore stopped passing one of the differential microphone signals to the op amp input (hence quieter). You could perform a simple continuity test to check this.
The repair is quite tricky, therefore I suggest that you send it back to the factory for repair..
However if you have a hot air solder station etc, or access to one, it might be worth a shot!
Regards,
Paul Walster...

wal's Website

  • From: Adelaide - Australia
  • Registered: 2007-05-01
  • Posts: 430

Re: FF800 Pre-Amp problem

Thanks for that Paul. I will certainly check it out. If I deem anything above me we have some great techs in town that would certainly be able to help me out. I certainly wont attempt any of the surface mount components (I don't have a hot air solder station or anything else for that matter that can do such fine work)
I should actually record the sound, as with a dynamic it's fine. With +48v on, a condenser is delivering broadband noise... it's ugly! :-)

Apparently there is a service agent in Sydney.. but haven't found out who yet. (a fair distance from here). So getting it done locally is my preferred option.

Thanks again,
Matt

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Matt McKenzie-Smith (UFXII, UFX, Babyface) MacStudioUltra OS13.2.1
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mattrixx's Website

11 Reply by wal

  • wal
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  • From: Derbyshire, UK
  • Registered: 2010-09-16
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Re: FF800 Pre-Amp problem

I suspect it's the same fault I found on mine Matt.
The noise is confusing. It does sound like an electrolytic gone bad.
But in my case the resistor solved it 100%
Do the sensitivity test by A/B with another channel without phantom using a dynamic mic.
If it's quieter, you could then disconnect pin two then pin three of the XLR plug in turn for a more revealing test..
good luck,
Paul...

wal's Website