New (to me) Tubemeister 36 Redbox output issue

I'm trying to determine if I have a problem or if I am doing something wrong. Everything else works perfectly on the head but when I try to go into an interface box (Clarett) via the Redox and a mic cable I get no signal at all.

Is there some switch I am missing or is it just screwed?

The Redbox is differential out. Is your Clarett set up as differential input to match or is it single ended? And that's assuming you're using a XLR -> XLR cable and not a XLR -> 6.35mm jack?

Well, I switched the Clarett from Line (as instructed in the H&K manual) to Mic and finally got signal but it is horribly overdriven until I start a DAW. If I just try to monitor out from the Clarett the sound is horrible. Not the end of the world just odd that the signal comes in that hot.

Yes I see what you mean. I was wondering if you were set on Line or Mic. But I would have thought that it would be Line in that you wanted. The Redbox is a real amp through cabinet simulator output which has an output of -10dBV which comes in a shade under 0.32Vrms or 0.9V p-p. That's in the bounds of line level stuff. And that's at an impedance of 1360R differential.

I wonder if the H&K has a floating differential output rather than a true impedance balanced one. That's one where you have the signal on pins 2 & 3 and the screen on pin 1 but the signal is left ungrounded. When you couldn't get any signal how were you wired up? Were you using a mic XLR -> mic XLR cable or a mic XLR -> jack? From the look of the Clarett drawings it may be necessary to have a XLR -> jack into the Line socket but you would have to wire the XLR end up to suit the needs of the H&K Redbox output.

Which model is your Clarett? I've had a quick look at them trying to see how their input is set up but they don't make the figures easy to find. I think it may have a transformer input for mic work which really wouldn't take the line level very well at all. As I suggested above, you should be able to use a single ended cable, (just one side of the differential output on pin 2 and ground on pin 1), and lose half your signal but that would go into a line level jack on the Clarett if that is available.

bordonbert wrote:Yes I see what you mean.   I was wondering if you were set on Line or Mic.  But I would have thought that it would be Line in that you wanted.  The Redbox is a real amp through cabinet simulator output which has an output of -10dBV which comes in a shade under 0.32Vrms or 0.9V p-p.  That's in the bounds of line level stuff.  And that's at an impedance of 1360R differential.

I wonder if the H&K has a floating differential output rather than a true impedance balanced one.  That's one where you have the signal on pins 2 & 3 and the screen on pin 1 but the signal is left ungrounded.  When you couldn't get any signal how were you wired up?  Were you using a mic XLR -> mic XLR cable or a mic XLR -> jack?  From the look of the Clarett drawings it may be necessary to have a XLR -> jack into the Line socket but you would have to wire the XLR end up to suit the needs of the H&K Redbox output.

Which model is your Clarett?  I've had a quick look at them trying to see how their input is set up but they don't make the figures easy to find.  I think it may have a transformer input for mic work which really wouldn't take the line level very well at all.  As I suggested above, you should be able to use a single ended cable, (just one side of the differential output on pin 2 and ground on pin 1), and lose half your signal but that would go into a line level jack on the Clarett if that is available.

I have the Clarett 8PreX. I am using a standard XLR/XLR cable going from the amp to the Clarett (using everything set as described in the manual). However if I set it to Line In I get nothing. If I use Mic In I get audio, only highly overdriven... also I can not silence that channel even if I turn the volume pot all the way down. Something weird is going on I just can't pinpoint it.

I'm not surprised that you get heavy overdriven sound on mic, the Redbox out is way way above that level.  Are you sure that the Line In setting on your Clarett doesn't switch from the XLR socket to the Jack socket exclusively?

Clarett 8 PRE ‘X’ Factors:

Additional 8 channels of ADAT IO
Designed for the Studio Installation with separate instrument, line and mic inputs
Dedicated Phantom Power on individual mic pre channels
Dedicated High Pass Filters on each channel
Dedicated Phase Reverse on each channel
26 in 28 out

If I were you I would try an XLR -> 6.35mm Jack adaptor on the end of your xlr cable into the Line In socket.  It may be as simple as that.  Something cheap and easy like this:



or even make up something like this if you have the plugs lying around:

Yeah, I already ordered it.

So, yes I did finally get a signal out that wasn't ridiculously high but I still can not pot the channel down to zero. For now I am just going to stick too SP/DIF

Good, so we have the signal in the right ballpark regarding level, now it's a question of control. Exactly what is it you are trying to get at with the very low volume settings?

You are right, the TM36 manual describes this and says just what you have, You can't mute the amp completely by backing the Masters all the way down. I don't really understand why this is a problem as the volume you can reach is pretty low down and, of course, the guitar volume can mute things. They point out that the power soak helps to take care of your volume needs regarding sound from the speakers, including selecting Speaker Off which leaves the Redbox on. That way you have Redbox output but no speaker output at all if that's what you are after. The only complication you should find is that going up to 36W means an increase in volume on the Redbox too as the second pair of output valves kicks in. There is no difference between the 1W, 5W and 18W settings to the Redbox.

Anyone else have this problem in practice with the Redbox out?  I'm not a user of it so I don't know the problems first hand, (but I can read schematics ).