kaouki
Registered User
Join date: Sep 2012
111 IQ
#1
Hi all,

I am new here and a novice guitar player playing a bit of Blues, Jazz, Classic Rock.

I had the opportunity to buy a H&K Tubeman MKI secondhand for 100 euros. I like some of the sounds I can get out of it a lot but the pedal lowers my guitar volume instead of giving me more gain. This happens on all three outputs (Guitar Amp/Mixer/Power Amp).

The controls work well, so I am thinking it is maybe the tube that needs to be replaced. The tube in it is a Electro Harmonics 12AX7 or ECC83. As I don't like the "Rock" setting (the pedal has four modes: Jazz/Funk/Blues/Rock)

I would like to have a smoother sound. Is a 12AT7 or 12AU7 as I read often on the internet a good replacement?

Will this solve my gain problem?
Last edited by kaouki at Sep 18, 2012,
end_citizen
New bird. Flightless
Join date: May 2006
1,581 IQ
#2
I'm not too familiar with the pedal and can't find any schematics on it. If it is like a regular tube preamp (high voltage - not starved plate), avoid the 12AT7. It has very harsh distortion characteristics.

The tubes I would recommend you try to get are either the 5751 or a 12AY7. I don't know if this would make the pedal any louder since I can't find a schematic and certainly don't have one in front of me to test.
kaouki
Registered User
Join date: Sep 2012
111 IQ
#4
When looking for the schematic I maybe found the answer. As Thomas Dunham stated on his Picassa gallery:
"The greatest tube pedal ever! The components are top notch except the pots which I have replaced twice already, otherwise very nice quality. Power supply is 12V A/C but when my power supply died, HK sold me a replacement 14V and threw in a set of said mini pots."