FINISHED (Just about) - compact JTM45 build.

paulnb57

Andyjr1515 said:

No idea whatsoever what 7/8 of the threads are talking about, but it looks great and I suspect it will perform just as well

Me too!

ICBM

4114Effects said:

@ICBM that's exactly what's on order ... although the schematic I have uses 2m safety resistors :-)

Excellent . No practical difference - 1M is marginally safer for the valves, 2M2 probably gives a slightly better taper at low settings.

Wazmeister

Mate that looks superb ! You always have great aesthetics on your builds..

My concern is that the circumflex will be differentiating against the lower input thorax lumper.

That being said, I am pretty new to all this amp speak...

Modulus_Amps

Wow you have been busy!

Did you end up making the faceplates yourself? they look pretty nice...

The red tolex looks almost burnt orange, or is that just the lighting?

4114Effects

@modulus_amps it's standard red, it's just the workshop lighting that makes it look that way. Faceplates are waterproof self adhesive glossy printer paper attached to thin aluminium sheet and lacquered. Seems to have worked pretty well.

Modulus_Amps

@4114Effects yes it looks really good, will mention it on some of the amp building sites I frequent

UnclePsychosis

That looks fantastic. Great work.

Sassafras

Looks great.

I also like the power switches at the back, best place for them.

TimmyO

Great work!

4114Effects

Wow ... finished, switched on, biased and sounds awesome. I can't believe how noise-free a build of this size is. No hum, background noises or oscillations, despite some of the wire routing being less than ideal. Just a small amount of background hiss with the volume cranked, as you'd expect.

Master volume works really well. This amp is LOUD. I can't believe or stress just how loud and punchy this is. The tone is just about perfect, I've done the input jumper trick and blending the channels works really well. I've built it primarily as a pedal platform but the overdrive on it is gorgeous too. Just the right amount of crunch and gain for me.

It was a tricky build - because it's so compact the wires had to be routed in a particular order. Seems to have worked out well though.

The eagle-eyed amongst you might have spotted that it's actually a JTM50 - I went with EL34 valves in the end as that suited my output transformer.

Knobs are temporary - I've ordered some larger MXR style skirted ones. Just waiting on feet and corners to arrive now.

robinbowes

I've got a lovely 1x12 cab that matches your head perfectly!

Modulus_Amps

Well done. Looks good! Have you soldered directly to the HT fuse or is there some other magik in use?

4114Effects

@Modulus_amps for some reason the fuse holder broke when I was putting the fuse in. The fuse is soldered there until the new one comes :-)

ICBM

4114Effects said:

The eagle-eyed amongst you might have spotted that it's actually a JTM50 - I went with EL34 valves in the end as that suited my output transformer.

The best of all vintage Marshalls in my opinion - more upper mids and that classic Marshall ringing crunch than a JTM45.

It's also a Bass model not a Lead really because it has a shared cathode network for V1, although early Lead models did too. Also better in my opinion.

The knobs you really want to go with a white-panel JTM are some like these…

http://www.amparchives.com/album/Marshall/Parts/Knobs/slides/JTM 45 Clapton Knobs.jpg

http://www.vintageamps.com/jtm45Collection/1002/cabfrontA.jpg

[/pedant]

4114Effects

@ICBM yep, running the bass at about 1-2 out of 10 on the dial. Toyed with the idea of changing the PI and V1 cathode cap to reduce the bass a little but I'm loathe to alter the circuit as it sounds so good. Loves pedals too.

oaf

Very nice indeed. Well done!

BigMonka

Great work, it must have been tricky doing any soldering once the board was it the chassis as it looks really tight.

thermionic

Lovely looking amp, and really neat construction... But lose that cheap Vox handle!

benvall

Wow. This looks great. I've got most parts, except for the transformers and choke, for a JTM45 build. It's been three years and I've still not finished the main board.

I get serious gas envy when I see quality builds like this.

Any sound clips / video?

ICBM

4114Effects said:

@ICBM yep, running the bass at about 1-2 out of 10 on the dial. Toyed with the idea of changing the PI and V1 cathode cap to reduce the bass a little but I'm loathe to alter the circuit as it sounds so good. Loves pedals too.

Have you got a bright cap on the Ch.1 volume pot? I can't see in the pic. If not, 500pF (not the daft 5nF they put on later Lead models!) works well. Although obviously not if you turn it up full .

What's this running the bass at 1-2 thing? I don't think I've ever set it anywhere other than 10 on an old Marshall .