Ampmaker P1800 footswitch mod: done

Fatfingers

Those of you that have built this amp – have you considered making the two inputs foot switchable? Seems to me this would be a great way of getting a boost for lead work.

Fatfingers

I guess that's a no, then. Well, I've ordered one of those little Weber switching boards, so will report back once I've got it installed.

paulnb57

I emailed Ampmaker (I'm working nights and am foggy headed, so bear with!) asking if I could A/B between inputs on one of his amps, Im pretty sure it was the P1800 to give faux two channels/lead boost, and he replied that it would not work....I think its to do with the way the inputs are wired, dunno if it could be modded, but Ampmaker offered no suggestions, so perhaps with this design its not possible......drop Ampmaker an email, he is very helpful.....

Fatfingers

I can't really see why it wouldn't be possible. After all, there are two inputs. If you can physically select them by pulling the jack out of one and putting it in the other, it should be possible to do the same thing with a relay.

ThePrettyDamned

Fatfingers;462165" said:

I can't really see why it wouldn't be possible. After all, there are two inputs. If you can physically select them by pulling the jack out of one and putting it in the other, it should be possible to do the same thing with a relay.

I think one input cascades into the other though, which might stop this working.

Fatfingers

Yes, I think you're right that one cascades into the other. But I don't see why that can't be done with a relay?

Danny1969

You can mod it you just need to mimic the action of the switched jacks as well as the input into the first valve. So if input One is empty pin 1 and 2 are shorted and 3 and 4 are shorted for example. 

Fatfingers

Danny1969;462669" said:

You can mod it you just need to mimic the action of the switched jacks as well as the input into the first valve. So if input One is empty pin 1 and 2 are shorted and 3 and 4 are shorted for example. 

Yeah - that's what I thought. I'm going to give it a go. I'll report back when I've done it.

Fatfingers

Blimey

Can anyone help with this? I have a little DPDT relay board ready to go, but I'm struggling to get my head round the schematic required to replace the two input jacks with one input jack, and the relay.

Fatfingers

Here it is as standard. The top jack is the Normal input, which feeds into the second half of the ECC83 preamp valve. The lower one is the Hot input, which feeds into the first half of the valve, the output of which is then fed back into second half.

Fatfingers

Okay. Do we think this will work? I can't see the need to switch the input of the Hot gain stage to ground when using the normal input, as its output is isolated when the Normal channel is selected.

Misterg

Fatfingers said:

Okay. Do we think this will work? I can't see the need to switch the input of the Hot gain stage to ground when using the normal input, as its output is isolated when the Normal channel is selected.

I think that should work - I would switch the 1st stage input to ground though. Just good practice. (All you need to do is ground the N.C. terminal up in the top left.)

Fatfingers

Yes. Certainly can't hurt.

Fatfingers

Okay - a mere 18 months later I've finally got round to making this mod. With the hot channel selected via the switch that controls the little Weber relay board, I have the hot channel. But with the normal channel selected, I have zilch. Nada. Sod all. Can someone cleverer than me please have a look at the circuit and suggest what the problem is?

Fatfingers

Eek. If the combined wisdom of The Fretboard can't help, I'm in unchartered territory!

Fatfingers

I've sussed it. Will post details and pics tomorrow.

paulnb57

Good news!

Can I ask your overall impressions of the Amp? Giggable?

Ive already built the little WF 55 and would never get rid........

Fatfingers

I absolutely love it. Yes - it's giggbale, certainly. I have two Vintage 30s in mine, which are pretty efficient speakers so it goes plenty loud enough. And with the foot switchable channels it's even more useable.

Fatfingers

Here is the channel switch board installed.

Chalky

Well done - your perseverence is an inspiration!

Fatfingers

Thanks, but I didn't have a lot of choice but to persevere – this is currently the only amp I own!