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Thread: Behringer Tube Ultragain Mic200 Preamp - No input signal

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    Behringer Tube Ultragain Mic200 Preamp - No input signal

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    Hi all,

    I have been using a Behringer Tube Ultragain Mic200 Preamp for years now and it has served me well.

    I recorded something last week but came to do the same this weekend but was getting no input signal. I tested the preamp out with different mics and instruments just in case, but still wasn't getting any input signal. All the cables etc are working fine, so it's definitely the preamp.

    Do any of you clever people know why this could be happening and how I can solve the problem?

    Thanks in advance!
    Andy

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    Some of the push buttons Behringer puts in their gear suck. They get dirty and can fail to make a connection. You might try getting a can of contact cleaner (DeOxit is about the best) and shoot a quick shot down the side of the push button followed by operating the button several times.
    Do any of the LED's light including the VU level lights with input?
    Mark.......

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    I know my eyesight is poor but I cannot see any valve on that attached schematic!

    As Mark says, what indications do you have? If you want to fix this pre amp you will need a Digital Multimeter.
    The circuit also uses several connectors in the audio path and these have to be suspect. I have had the RC4580 ICs fail in a Behringer but these are probably Surface Mount devices and beyond the scope of most people to change.

    Dave.
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    Quote Originally Posted by ecc83 View Post
    I know my eyesight is poor but I cannot see any valve on that attached schematic!

    As Mark says, what indications do you have? If you want to fix this pre amp you will need a Digital Multimeter.
    The circuit also uses several connectors in the audio path and these have to be suspect. I have had the RC4580 ICs fail in a Behringer but these are probably Surface Mount devices and beyond the scope of most people to change.

    Dave.
    If you have the same PDF schematic, scroll down (page 2). X6(4) and X6(5) page 2 tie it back to X7(4) and X7(5) page 1 (I think). If you want a challenge, find the source of the signal that goes to the LED level metering 'MTR' shown on the second page.
    Mark.......

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    Quote Originally Posted by arcaxis View Post
    If you have the same PDF schematic, scroll down (page 2). X6(4) and X6(5) page 2 tie it back to X7(4) and X7(5) page 1 (I think). If you want a challenge, find the source of the signal that goes to the LED level metering 'MTR' shown on the second page.
    Gotcha! Ok, well the valve IS in the signal path but 12AX7/ECC83s rarely fail at 300V, running at 48V very unlikely. Still, should be easy enough to jumper those connectors.

    If it is the valve stage at fault most likely is loss of heater power. Again, O/C heaters in valves is very, very rare. I would trust even a Russian valve over Behringers build quality!

    As an aside. One of the things I regret is never getting around to working with standard valves at very low anode voltages? Many people disclaim the practice as "not proper" but I am not so sure. Whatever it is that peeps want from valves should be there if they are working at all?

    Since the main benefit of 200V+ circuitry is massive voltage headroom there has to be a reason to use a valve at low volts (other than marketing puff) because even with a 48V supply a decent op amp can beat it.

    Dave.

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    Quote Originally Posted by whome View Post
    Wowee, it has been a LONG time since I had valve classes at the uni.
    I vaguely remember that they were more linear at higher plate voltages. Maybe also more efficient.
    But there was a reason they were run that way.
    Quite honestly, with the resistor values in that circuit I cannot see that valve stage working at all! But then as I say, I have done nothing with ultra low voltage valve circuits.

    Compared to say an NE5532 even the best valve circuits are "not very linear" but then I guess that is part of the reason peeps love 'em?

    Dave.

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