18W TMB Build

[Dimitar]

Hello everyone! I was not active on this forum for a long time, until recently when I became interested in building tube amps, even though I was always interested in electronics, both analog and digital. This is my first serious build, the actual first one was a one-day jobbie, EL84 SE with simple preamp build from old parts from tube radio. But that did it for me and I'm now really into bulding tube amps, and I'm already planning my next build.

So here it is:















Most of the parts were sourced from tube-town.de, since I live in Macedonia, Europe it was the best choice considering quality, price, shipping cost and duties.

The power transformer is build by TubeTown in Germany, the HV winding is 600 V C.T. @100 mA, 6,3 V C.T. @3,2 A heaters and separate 6,3V @1,8A for the tube rectifier heaters. Output transformer is Hammond 1750PA with 8400 Ohm primary and 4,8,16 Ohm secondaries.

Filter capacitors are F&T, tone caps are Mallory 150, carbon film resistors are Xicon, APEM switches, Belton tube sockets, Neutrik jacks and Alpha pots.

At first I wanted to build the original 1974 circuit, but I changed my mind and built it with TMB channel. I sourced every part individually and not as a kit, so I have combined the 1974 schematic from Tube-Town for the Normal channel and the TMB channel from Dockery. It is currently loaded with JJ and EH 12AX7s in the preamp, and unmatched set of EL84 tubes.

As you can see I still don't have the faceplate and haven't build a headshell, but since I would use this amps to try different mods like PPIMV, VVR, Pentode/Triode switch, relay channel switching and so on, the headshell wouldn't be of much use.

I'm really satisfied with the results. I love it. Recently I also got a Marshall JMP SuperLead 100W head from 1978 with matching 4x12 cabinet with G12H-30 55Hz Blackbacks and damn, it sounds awesome with them.

As of this moment I don't have any soundclips but I hope I will soon. Just need to find someone who would record the amp for free (or beer) for couple of hours.

Here it is in my small workshop on the 4x12 cab:

[neikeel]

Excellent.
Bet it sounds really good through those speakers?

[danman]

Nice looking build!!

[Dimitar]

Thank you. Yeah, it sounds really good with Blackbacks. Still haven't tried it with my 4x12 G12-80 cab. When I buy or make a headshell it would surely complement the small 2x12 Marshall cab I have.




I will be building the same amp for a friend but with some twists like VVR and footswitchable channels.

I'm still looking for ideas for the switching relay wiring. Most amps with switchable channels share the first gain stage. On this amps the channels are completely separate.

I'm thinking if I install relay on the inputs it would introduce pops and cracks when switching and I want to avoid this.

Any thoughs?

[neikeel]

I used a Grainger opto coupler recently for footswitching an extra gain stage in and out - works perfectly.

[axeman]

Excellent, post a vid on youtube. What are the transformers used. I have all the parts to build an 18 watter except the trans