H&K Tubemeister 5w Head

[musicman86]

Hi!!!!
i buyed this head for home studies and live music pub, but i need a schematic for adding:
- stand-By switch,
- send/Return jacks,
- channel selector from my pedalboard.
this Head it's beautifoul !! great sound and tone !!

i only find schematic for tube meister 18w, but nothing for tubemeister 5.

can you help me please ? ? ?   

thanks!!!!!

[thermionix]

Have you tried asking H&K?

[musicman86]

yes !!! but h&k release only a authorized repair center, ask a local distributor and the result is the same

this head is end of production and a basic circuit, i dont understand why make thousand problem for one schematic

Il triamp it's a  2.500 $ head, actually in production, schematic and diagram  easy find whith google.

[vigilante397]

First off, welcome to the forum

I wasn't able to find a schematic, but I have never seen an overly complicated 5W amp. That being said, some quick questions about your plan:

1) Have you ever worked on amps/electronics before? Adding a standby switch is easy enough, but adding FX loops and remote channel switching can get complicated.

2) Why do you need these mods? I've found standby switches on smaller amps rather useless, single 12AX7 preamps often don't have the power to drive an FX loop (send/return), and the easiest way to add a channel switch is to hack up the amp.

3) Have you considered alternatives? If you want your amp quiet while it's warming up, you can roll off your guitar's volume. Many effects (not all, just many) have no audible difference between FX loop and in front of the amp. If you want to switch between clean and distortion, you can throw a pedal in front of the clean channel, or roll your guitar's volume down on the gain channel.

HOWEVER if you are an insatiable DIY-er (like many of us) and you want to do these mods for the learning experience, more power to you! But you may need to trace the schematic yourself, as the schematics aren't readily available online.

Best of luck to you, and there are plent of people here smarter than me that would be happy to help as wel

[musicman86]

Hi!!

Thanks Vigilante!!,

i have experience on this area. the problem is the density of pcb, 18x15 cm dual layer, and the component is very close!! for S/R simply add a op/buffer for driving external FX , the it's amazing (for me), and the dist channel it's perfect to play hard rock!! this is "study" head 5w for home it's perfect. this model is equipped whit a "red box" speaker simulator, but then receive signal from power load and not by preamp.  switch is a simple 3 pin for controlling channel, driving by simple relay. the important mod's is S/R.

stand-by is not for noise ( impressive for very low noise) is for extend tube life.

thanks!!

[vigilante397]

Standby switches don't actually extend tube life: http://www.valvewizard.co.uk/standby.html

That's why many boutique amp builders leave them off.

As for the S/R, are you able to look at the circuit and find the end of the preamp circuit before it goes into the power amp? In many amps this is on the middle lug of the volume pot. This is where the loop will go. Is there any solid state circuitry (op-amps, etc.) in the amp already? If so it should be easy enough to draw power for an op-amp powered FX loop.

[musicman86]

Hi!!!!

Thanks for replay!!

maybe find connection from preamp to final stage. after volume pot (central tap), controlled by IC MC33078p drive a pair of transistor. i try cut trace between pot and op. new routing is

Volume pots ----> buffer send ------> buffer return -----> op amp.........

for channel mod it's very hard. manual selector have 12 pins (4 group of 3 pins).