Relays and switchable MV

[Smokebreak]

I figure it's time I learn about relays and implement them in a build. I've read a lot about using them but until I actually put them in, I'm still in the dark a bit. I've got a great candidate amp and the horribly cobbled together schematic is attached. My apologies for that.
I've got the amp up and running, but right now my first stage switching happens via 2 input jacks. Also, my "channel" switching happens in another spot with dpdt on front panel and the gain pots are shared. Finally I only have 1 MV.

No matter, the schematic is what I want to end up with.
So I believe I'll need 3 relays, and the last 2 need to switch "together". I would ultimately like to have a footswitch with 2 buttons : "channel" and "boost"(to insert 1st stage).

That is about all I know. I don't mind at all using a kit or even pre-assembled board(s?) this first go-around. I've looked at the Mojo, Weber, and Skipzcircuits kits, but they are all dpdt(i think), and I need 3 of those. weber has a kit that is 4 relays, so i imagine I could just use 3?
I would like to be able to use my filament supply, or I have a 5V unused tap as well, but again, I don't really understand what kind of voltage requirement I need .

Any help/input/suggestions here would be greatly appreciated. Perhaps there is a more elegant way to do this, as well?

Oh, what about the location of the board? Is it gonna be quiter in certain spots? Also, do you all usually have mechanical switches on the panel, as well?

Finally, I'm trying to work out a good switchable MV scenario. This first one is something Jana posted last week, but I think it may have been for a different application. The 2nd one came from another forum, but I'm not crazy about my signal going through a 470K, though if I understand correctly, resistance is necessary there to not load down the tone stack?

Whew, lots o questions. I'll worry about the actual footswitch later.
Thanks, J

[Jana]

As far as I can recall, my memory isn't what it used to be. I don't recognize anything in this schematic that I suggested--maybe I did but forgot, lol.

Someone here--Colossal?--sells relay boards on his website.

A few thoughts:
have you built the high gain part of the circuit and tested it yet? If not, I would highly suggest that you build a prototype of the amp with just the OD circuit. Once you start testing, you will probably find that you need to make changes, move stuff around, etc. It's not easy to put together an amp with this many gain stages and still have something musical.

Once you get the high gain section debugged and tuned, then you can decide how you want to implement the clean section.

[Smokebreak]

As far as I can recall, my memory isn't what it used to be. I don't recognize anything in this schematic that I suggested--maybe I did but forgot, lol.

Someone here--Colossal?--sells relay boards on his website.

A few thoughts:
have you built the high gain part of the circuit and tested it yet? If not, I would highly suggest that you build a prototype of the amp with just the OD circuit. Once you start testing, you will probably find that you need to make changes, move stuff around, etc. It's not easy to put together an amp with this many gain stages and still have something musical.

Once you get the high gain section debugged and tuned, then you can decide how you want to implement the clean section.

Thanks Jana. Yep this amp has been up a running for a few weeks with no issues. It was my #36 before that but I found it a one-trick pony. A really great sounding pony, but..
I like what I have in here a lot better and its quite versatile. Basically has stock plexi/800/800+, then that extra lil stage upfront. I'm getting great cleans and then the massive crunch. My switching right now is tapped off the 2nd gain pot to go from plexi>800 or plexi>4stage, depending on what input I use, but all channels are sharing the gain pots and MV, thus the different switching I've got in the scheme, and the want for the relays. So basically the placement of the switch is the only difference in the actual amp as it is built today. I have a few cathode switches too.

I think that MV setup(simple parallel one) was yours , but I seem to remember it had something to do with an FX loop setup thread or something..

[Colossal]

I'm your ice cream man, stop me when I'm passin' by
All my relays are guaranteed to satisfy

See the link below!

[Smokebreak]

I'm your ice cream man, stop me when I'm passin' by
All my relays are guaranteed to satisfy

See the link below!

Ok great!
Now, my issue is that I'm not exactly sure what all I'd need to accomplish the switching in the posted schematic. Its 2 DPDTs that need to switch together, then another separate DPDT. See I know next to nothing about relays and can all this switching be accomplished with one footswitch jack? I can't seem to open the installation pdf.

[Jana]

I would add a grid reference resistor to R7--there will be a moment when the grid of that tube has no reference to ground when the relay switches. It might be a cause of pops.

[Smokebreak]

Ah I see. Will do.

[Jana]

Um, I hate to be the one to point this out, but it seems to me that you are going to have an unused triode!

[Colossal]

To do what is shown on your schematic will take three relay boards. The first switch which adds or removes the extra gain stage up front is one board. Switching out the second stage is one board and switching between master volumes will take half of a third. You could make all relays fire with one foot switch or wire all three independently. If you want three independent footswitches, a lot of guys use the generic Marshall 3-button and put a 5-pin DIN jack on the back of the amp.

Sorry the install document link is not working. I am revising the drawings. It is a very straightforward affair to install them though. I ship them assembled and tested. All you do is wire them and I can help you with that if you are struggling or unsure. You will need a small dedicated power transformer such as a little Radio Shack special 6-9VAC, non-center tapped, or an unused 5VAC heater winding. Sorry for the shameless self promotion but your application is exactly why I started offering these. I needed to switch stuff in my own projects and didn't want some tacky, jury rigged solution.

[Colossal]

Um, I hate to be the one to point this out, but it seems to me that you are going to have an unused triode!

there is still one half of a relay available! Better add a cathode follower and switchable diode clipping.

[Smokebreak]

Um, I hate to be the one to point this out, but it seems to me that you are going to have an unused triode!

there is still one half of a relay available! Better add a cathode follower and switchable diode clipping.

Its all good. I got a great deal on ebay on 1/2 a 12ax7. But seriously, this helps a lot, and the CF master/diodes brings up a good point. Here's where I'm at :

1. Trying to find the best solution for switching between 2 MV after the tone stack. I like the one that's above the other one on my scheme, but it basically straps a 1M resistor across the pot that's in use. In that case, I think I would need the other half of that relay to lift the ground leg of the pot thats not in use. Have I got that right?

2. I'm wanting a 2 button footswitch setup. 1 that fires off the MV and the channel switch, and one that fires off the 1st gain stage.
Can I do this with 1/4" jack? Is a 5 pin DIN a necessity for 3 buttons?

[Colossal]

1. Trying to find the best solution for switching between 2 MV after the tone stack. I like the one that's above the other one on my scheme, but it basically straps a 1M resistor across the pot that's in use. In that case, I think I would need the other half of that relay to lift the ground leg of the pot thats not in use. Have I got that right?

Yes, you certainly could use the other half of the third relay board to totally isolate whatever MV is being switched out.

2. I'm wanting a 2 button footswitch setup. 1 that fires off the MV and the channel switch, and one that fires off the 1st gain stage.
Can I do this with 1/4" jack? Is a 5 pin DIN a necessity for 3 buttons?

DIN jack would be best because each on/off trigger needs a pin plus a common ground return for all.

[Jana]

But since there are only two circuits being switched, and there is a common ground, wouldn't a stereo 1/4" jack work?

[Jana]

Where is the unused triode? I have a crazy idea if it is towards the backend of the preamp.

[Colossal]

But since there are only two circuits being switched, and there is a common ground, wouldn't a stereo 1/4" jack work?

Yeah, a stereo jack would be fine. DIN jack allows for more optionality later when the modding bug strikes again.