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ADA Microtube 200 Problem in Bridge/Mono mode


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Hey Guys-

 

I recently picked up an ADA Microtube 200 power amp off of ebay. The amp seems to be working fine in stereo mode, although the volume seems to be a bit lower than expected.

 

However, in bridged/mono mode, there's barely any volume at all and when I turn up the volume on the preamp (Digitech GSP 1101), there's nothing but severe distortion/static.

 

I'm considering filing a claim through ebay. I'm also trying to get the seller to pay for the repair as an option. If there's an easy fix, I'd like to keep it as it is a great sounding amp (in stereo anyway :( ).

 

The preamp tubes seem fine as I tried to switch them with no change. The output in bridged mode is 8 ohms and I used several 8 ohm cabinets as well.

 

Thanks in advance-

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Have you read the manual?


Exactly how are you hooking up the speaker to the two outputs (I mean exactly... details and all)

 

 

I have. If you click on the attached, I ran the preamp into the mono in in the middle/top and the middle/bottom jack to an 8 ohm 1x12 speaker cab in mono bridged setup.

 

http://i101.photobucket.com/albums/m60/mikjwilli/guitar/ADARear.jpg

 

For stereo, I did the same, but I used the last column of jacks on the right (channel A).

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Okay does both channels work independantly?

Input A is putting out for output A.

Input B is putting out for output B.

I'd put a jack in input A with no signal on it to break the switch and put a signal through input B to see if they work individually, in stereo.

So there would be no signal on output A and whatever your feeding it on B.

 

I found your post on the ADA board,sometimes it takes awhile there's alot of people over in Europe on that board.

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Okay does both channels work independantly?

Input A is putting out for output A.

Input B is putting out for output B.

I'd put a jack in input A with no signal on it to break the switch and put a signal through input B to see if they work individually, in stereo.

So there would be no signal on output A and whatever your feeding it on B.


I found your post on the ADA board,sometimes it takes awhile there's alot of people over in Europe on that board.

 

 

Both channels are working independently and seem fine. I didn't have to put a jack in channel A. Channel B worked without.

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Looks correct.


There may be a problem with the internal normalling switches inside the jacks. Just to be sure though, verify that the mono input doesn't need a balanced signal in order to get a bridged mono output.

 

 

Same thing with a balanced 1/4 cable. Thoughts?

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Thanks everyone-


I decided to bring it to my tech, who's a pretty reputable tech. He confirmed both sides were working OK. As it turns out, there was a problem with an internal switch, which he was able to repair.

 

 

That was the most logical reason based on how the input stages are configured.

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