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British Built MJW 200w all-valve custom monster ***New Guts Shot 30th Nov*** It's Done!!!!

Sean

By Sean,
in Build Diaries

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Sean Proficient

Sean

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Evening all,
I've realised that my dream amp doesn't exist so I've decided to do something about that and change everything.

I want a 200 watt 4xKT88 monster but with some custom features. It's the custom features that will really differentiate this amp from anything else out there.

I want a proper Brit Bass Monster but I also want a small(ish) recording amp that is all-valve and on top of that I want a 100 watt all-valve amp for churning out the power-filth at smaller gigs.

Anyway, here's the spec that I'm kicking around with the builder at the moment and I'd be keen to get some reaction to it:

Custom transformer/choke set
4 x KT88 output valves
Approx 4 off ECC83/81 preamp valves
ECC83 and ECC82 phase inverter and booster
Switchable to 100W and 50W - yes, really!
2 channels, foot-switchable
Channel 1 - cleaner channel with Baxendale/James tone stack – clean to slight grit
Channel 2 - dirtier channel with Fender tone stack – slight grit to dirt
Exact channel control config to be finalised, but:
Gain, volume, voice and T/M/B for each channel
Global master vol and presence
DI output with variable level, via XLR pin-outs and exact level TBC
DI raw post output transformer signal
SDM zero loss effects loop with bypass switch – pedal level
Speaker outputs 1x4 ohm and 1x8 ohm Speakon only
240V only, mains and HT fuses on rear panel
Custom built chassis
18mm birch ply cabinet
Overall dimensions TBC, but approx 20" wide to match cabinet
Cosmetics TBC but standard MJW appearance
Metal side handles
Grills in rear and top of amp
Large rubber feet

That's the start and the deposit is paid...

Edited by Sean
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hamfist Rising Star

hamfist

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Sounds good to me. But .... I'd recommend considering power-scaling instead of the switchable power amp outputs. 50W really still is VERY loud, and if you are wanting it to double as a home/recording amp too then power-scaling really is the dogs-b0ll0cks. Martin is also an expert installer of power-scaling so it's a double win situation ! Years ago I had a JTM45 clone built by martin with the power-scaling. It really worked very, very well. I don't know about how it would go with KT88's though. Obviously Martin can advise you there.
As for the pre-amp voicings well that can neither be good nor bad, that's just personal choice.
For me, I'd rather focus on one high quality clean channel and then use pedals for my grit. In my experience working with an expert pedal builder (like COG effects) will be able to fine-tune your dirt requirements much more accurately than a tube-based pre-amp will. But if you're committed to an "all tube" dirt/pre-amp/power amp setup then good for you.

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Sean Proficient

Sean

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[quote name='hamfist' timestamp='1395214214' post='2399726']
Sounds good to me. But .... I'd recommend considering power-scaling instead of the switchable power amp outputs. 50W really still is VERY loud, and if you are wanting it to double as a home/recording amp too then power-scaling really is the dogs-b0ll0cks. Martin is also an expert installer of power-scaling so it's a double win situation ! Years ago I had a JTM45 clone built by martin with the power-scaling. It really worked very, very well. I don't know about how it would go with KT88's though. Obviously Martin can advise you there.
As for the pre-amp voicings well that can neither be good nor bad, that's just personal choice.
For me, I'd rather focus on one high quality clean channel and then use pedals for my grit. In my experience working with an expert pedal builder (like COG effects) will be able to fine-tune your dirt requirements much more accurately than a tube-based pre-amp will. But if you're committed to an "all tube" dirt/pre-amp/power amp setup then good for you.
[/quote]

We chatted through the power scaling and for my needs and because of the specs we decided to go for the switching.

As for the filthy channel, that's really because I love the grit from valves and also prefer to have it built in and not part of outboard effects but this way I can also employ something like COG effects through the clean channel when I want to.

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Mikey R Community Regular

Mikey R

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i didnt see an effects loop in the specs, you might need one to put your modulation and / or time based effects post dirt

EDIT: doh, missed it - youre going for a buffered loop, good choice :)

Edited by Mikey R
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Happy Jack Grand Master

Happy Jack

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[quote name='Roland Rock' timestamp='1395696555' post='2405301']
Got it. It was quite well hidden, as if there should be some prior knowledge on this?

[url="http://www.martamp.com/index.html"]http://www.martamp.com/index.html[/url]
[/quote]


Mmmmmmm ... chickenheads ...

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Sean Proficient

Sean

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Sorry, I've been off line for a few days. Yes, it's MJW that is making the amp. The transformer is currently being custom made (in the UK) and I'm hoping to have it by August or September. I'll be popping up to MJW a couple of times during the build to try it out through a cab at various stages to tweak the voicing.

I'm currently thinking that Sea Foam Green tolex is the way forward but haven't decided on a colour scheme yet. Any views?

Edited by Sean
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Sean Proficient

Sean

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So today I've decided on sea foam green tolex, black hardware, black face, white chicken heads. Transformers are ready and the prelim design is done,

Kinda like this

Edited by Sean
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Sean Proficient

Sean

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The custom built transformers have arrived.
Pic shows the pair with a transformer from an 18w all valve guitar amp for scale.
You just don't get the ooomph and heft without lumps like this :-)

[IMG]http://i1221.photobucket.com/albums/dd462/Stoker1/imagejpg1_zps2a971fc2.jpg[/IMG]

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Sean Proficient

Sean

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[quote name='Happy Jack' timestamp='1395747536' post='2405694']
Mmmmmmm ... chickenheads ...
[/quote]

I've decided against chickenheads as there are two rows of knobs and round ones look less cluttered. I do like chickenheads though, very cool.

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Sean Proficient

Sean

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[quote name='Dad3353' timestamp='1409085044' post='2536255']
You'll be wanting stout, thick 'penny' washers on those transfo lugs, I should think. It's quite common on old amps to find 'em well bent up because the amp has suffered a bump, and your ones weigh the moon. Just sayin'.
[/quote]

All sorted. He's a pro. :blush:

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davedave Apprentice

davedave

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I've got one of Martin's guitar amp. (Bantam head and 1x12), I went for burgundy snakeskin. They are great sounding amps and well built too.

I saw that he was in the process of your amp Sean. Glad to see it's someone from here that commissioned it.

I look forward to seeing the finished amp.

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Sean Proficient

Sean

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[quote name='davedave' timestamp='1409304527' post='2538433']
I've got one of Martin's guitar amp. (Bantam head and 1x12), I went for burgundy snakeskin. They are great sounding amps and well built too.

I saw that he was in the process of your amp Sean. Glad to see it's someone from here that commissioned it.

I look forward to seeing the finished amp.
[/quote]
I don't think I've ever been as excited about any new toy! Martin's a great guy to deal with too, he's so passionate and unbelievably patient with me trying to explain what I want in a pre-amp section. I'm looking forward to doing a thread on it when it's done, I've already got a photographer lined up for the shoot.

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