18Watt TMB and tone kit build

Modulus_Amps · February 2016

Hi Guys, I intend to build a new kit towards the end of this week, it is a TMB + Tone 18watt amp, with a post phase inverter master volume control. should be a cracking amp, anybody want to see pictures?

BigMonka · February 2016

Yep! I love watching build threads, it's what got me hooked on the forum.

paulnb57 · February 2016

Yep!

Modulus_Amps · February 2016

Ok Great, will upload some stuff tomorrow then.
cheers

paulnb57 · February 2016

Fab!

mudslide73 · February 2016

Having built a Ceriatone / Loverocker TMB 18 it will be interesting to see one done properly

Modulus_Amps · February 2016

Ok here is the layout I intent to build to start with, It is not thoroughly checked yet! so use with caution. The thing that concerns me most is the master volume control right next to the power switch, I may need to make that wiring shielded.

I am going to built it stock and then probably add two switches, one to run the channels together and one to cascade them for higher gain if needed, I will see when I get there.

https://www.mediafire.com/?kln631d0mxcx5lc

Here is the turret board being drilled out this morning, I prefer to use hole boards

Modulus_Amps · February 2016

Going a bit slower than expected here, got too much going on!

Got the chassis components all test fitted last night. Took about 45 minutes using hand tools

I will remove the jacks to ensure there is enough work room inside

Modulus_Amps · February 2016

Chassis wiring done, I don't use twisted heater wiring, it does not need to be twisted to cancel hum, if you are a beginner though I recommend you twist.

Modulus_Amps · February 2016

Turret Board Populated - No soldering to the underside of the board, it is not really a good practice IMO, all wires routed to the top so easy to see whats connected and easy to service/mod later on.

By routing through holes to the top is also helps support the wires and prevents fatigue failure... yes I know this is not mil spec gear but every little thing can help.

Modulus_Amps · February 2016

more photo's here if interested

https://www.facebook.com/media/set/?set=a.1230436080304097.1073741833.161119120569137&type=3

John_A · February 2016

Really neat work you make it look so easy!

Modulus_Amps · February 2016

its not hard, just have to take your time and not rush it, if its not right do it over...

GuitarMonkey · February 2016

Modulus_Amps said:

Chassis wiring done, I don't use twisted heater wiring, it does not need to be twisted to cancel hum, if you are a beginner though I recommend you twist.

I always understood that it was best to twist unless you use a rectified current for wiring?

Modulus_Amps · February 2016

Wires have to run parallel to cancel hum as the electric field that causes hum is perpendicular to the surface of the wire, twisting keep them together and achieves this, however you can just run them parallel like I do or use zip cord and achieve the same thing. I have done this in high gain amps with no heater hum.

It also helps to keep heater wires away from signal wires, which is why I have the wire running over the socket rather than all the way around. The effect of the electric field reduces exponentially.... meaning fast, so adding few mm between wires if you have heater hum can help allot

Modulus_Amps · February 2016

Input Sockets - the easy way to wire them up

Modulus_Amps · February 2016

Amp finished off, sounds pretty good, very pleased with the outcome, I had to reduce the gain going into the PI from the TMB channel as you could not get a clean tone from it, now that is it done sounds pretty sweet. good cleans and crunch, video to come soon.

Modulus_Amps · February 2016

Here is what it sounded like on Friday morning...Got some mods to try now, the customer that asked me to put the kit together wants more midrange and less EL84 sparkle from his kit.. more 70's JMP if you please... this will be interesting

https://youtu.be/st4Mnt8o5fQ

thermionic · February 2016

Sounds very nice.

Does the TMB reduce the overall gain in an 18W circuit? My experience with my N5X is that you get a lot more gain when the TMB is switched out, but that sounds pretty overdriven to me.

Modulus_Amps · February 2016

That video has both the pre amp and power amp overdriving, so it can get pretty thick with distortion. But this amp has a Post Phase inverter master volume, so it has 4 gain stages that can overdrive at lower volume levels with the TMB channel, I actually had to cut the gain going into the phase inverter so there is plenty on tap if I or the builder.customer wanted more.

The thing about the 18w circuit is there is no negative feedback, so the phase invertor and power section overdrive very easily, the TMB channel on this amp is pretty dirty.

if I was desperate for gain I could bypass the tone stack, but I don't need to, also that leaves you with a one trick pony then, Personally I think you would be better building a good boost pedal for the front of the amp.

Just had a look at the N5X schematic, not much gain on tap in that circuit and a plate fed tone stack is very lossy, I would add another 12AX7 to the amp to get the gain levels most guitarists are after.

thermionic · February 2016

Thanks for that answer, very informative!

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18Watt TMB and tone kit build

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