TriAmp Mk3: Effects loop and LED panel

Hi all,

I just picked up a second hand Hughes and Kettner TriAmp Mark 3 and all I can say is...... 'That amp is amazing!!!!'

Can I please have your help to answer 2 questions regarding this amplifier.


Question one is: Led noise

I seem to have some noise when I turn on the LEDs. When the LEDs are off the noise has gone. When the LEDs are turned on by the control from the back panel, the noise is present.

Is this normal? Can it be removed?

Question 2: Effects loop

Series/serial effects loop vs parallel effects loop. Every time I play the guitar I manually from the back panel, have to switch on series effects loop. This is because when I turn the amp off it reverts back to parallel.

It's this normal? How do I make it stay on series/serial?

Cheers Justin

And what do you know, there is another one out there!  Congrats on your buy Justin, I haven't played one myself so can't be too effusive but soundwise in vids they seem to be great amps and others love them too.

You really shouldn't get any noise from the lightss, (I presume you mean the front panel ones shining in the perspex?)  They should be well isolated from the signal circuitry.  I've dug up the schematic for the Triamp which is available online and I've had a look.  At first glance I can't find any reference in there on the light connections or control.  There is discussion online as to repairing these and it talks as though the lights are basic bulbs and not LEDs.  Assuming this is true I would be very careful.  They are a bit specialist and they are very expensive to replace - if you can even get your hands on them.

The GM36, which I have and know, uses LEDs for this.  It has a simple 2 pin socket from the main PCB with twisted wires up the right hand side of the perspex as you look at it from the front.  These lead up to the end of the LED PCB which is a very thin strip sitting on top of the perspex panel under the top cover.  You can see the twisted wires of this leading up the right hand edge inside the case.  The LEDs are surface mount on the PCB underside and therefore shine directly into the top edge of the perspex.

Can you see if your lights are fitted anything like that or if they are bulbs in fixed holders?  A couple of other relevant points.  Are they all working?  Is there any chance the cabling or any PCB has been damaged in some way, perhaps nipped or not refitted correctly during say a valve change?

What is the nature of the noise?  Is it a hiss/shush sound or do you mean you get a mains hum or buzzing type of sound?

The other side, i.e. the serial/parallel loop issue, seems to be that you should be storing the setting, parallel or serial, with each preset.  The manual says "The SmartLoop effects routing circuit offers parallel and serial FX loop modes for patching in external effects devices. Its status – on or off and parallel or serial – is stored within each channel or MIDI Preset."  Have you tried setting it to what you want then manually storing that preset to get the amp to remember it?  At the moment the amp would seem to be returning to the stored setting for its base preset and that means the loop is set to the same thing every time.

Thanks for your reply I really appreciate it.

Some of your direction has helped me already.

I ended up saving my settings via MIDI and now when I turn to the stomp box settings the series effects loop stays on. Goal achieved!!

The sound it's like an angelic hum not a buddy fizzy hum. It's soft but it's noticeable and it's only one volume. It doesn't increase.

I'll pull it apart later to see if the pin is as you noted.

Thanks again I think case is closed.

My next mission is to figure out how I can change the LED colours.

If the level of the noise stays the same when you use the amp that gives us a little more info. From that I would assume it also isn't affected by which channel you select. It isn't being injected into the signal chain early on in the preamp. It must be creeping in later after the level controls, perhaps in the power amp stages. I would guess the Fx Return buffer V8 is a prime candidate and you could consider the phase inverter valve V9 rather than the output valves themselves. You could try just slipping a valve screening can over those two in turn making sure it touches the metal chassis as it sits to ground it so as to be effective at screening to see if that makes a difference. Borrowing the one from the unused channel should be fine just for a test. It may even be possible that one of those two valves has itself become faulty and is sensitive in some way. Maybe swap each of them out in turn with a known good spare?

I do find it odd that there is no mention of the lights (are you sure they are LEDs, others report they are standard bulbs which is more awkward). The schematics in the service manual show nothing to do with them while they are clearly marked in in the GM36 schematics. If they are LEDs they should work with no affect on the noise level in the circuitry at all. You will have seen the vids online which show peoples' mods to the LED colour. Be warned, these are not as straight forward as some of them say. LEDs are not bulbs and you need to take a different approach to controlling them completely.

Anyway, good luck with it, glad the Serial/Parallel issue is tied down at least. Let us know how you get on with your LED conversion. Who knows, there may be yet another Triamp out there somewhere with an owner who loves a light show.