JMP channel switch

[warioblast]

Would it be possible to switch between 2 channels with a DPDT relay. I would be adding 2 independent pre-phase inverter master volumes. I'm thinking something like this.
Would it be that easy ?
I only use the brightest input on my JMP and I don't jump the channels. Do you guys think it's a good idea ?

[shooter]

I only use the brightest input on my JMP and I don't jump the channels.

not sure why you'd go through the trouble if you're only using 1 channel?

It will work, but maybe not well, switch popping is probably gonna have to be dealt with.  Volume/gain jump might be a factor.

[warioblast]

I only use the bright input but I'm constantly playing with the gain and PPIMV.
I find the normal channel too dark for my taste, but I thought I could maybe tweak it to make brighter, gainier... a different flavor.
I didn't thought about switch popping.
What about having only 1 channel, but with switchable gains & switchable pre phase-inverter master volumes. Would it be less prone to popping noise ?

[tubenit]

What about an A/B/Y box?

[shooter]

the normal channel too dark for my taste

I have a plexi-ish and agree each channel on it's makes me want to tear it down n start over, but once I get them blended, it makes me smile!

I would play around with jumped channels, (mine is single in, blended), like tubenit says an ABY

[Tone Junkie]

I'm with shooter . I always started with the bright channel then blended in the normal channel till I found the sweet spot. Tonal bliss was found in that combination. Either by themselves wasn't were it was at
. Both together was the sound of much of the rock from our generation. Since then I have tried many things with that circuit . From the Randy Rhodes Mod Which I doubt he ever used. Because it sounded terrible. To several others. You can get a  Free type tone by starting lower volume before blending. To a real chunky dirty tone by starting with a higher volume before blending.
the only thing I changed in the amp I play know was putting a master volume after tone stack and a ppimv . then blend 
Bill

[warioblast]

So you guys are basically saying I should turn my JMP into a JCM800 

I think I have enough jacks left to build an ABY box.

I kept reading about relay & opto / fet switching. One other thing I didn't think about was delay between switching channels.
But relays and FETs are fairly cheap so I might give it a try too.

[sluckey]

So you guys are basically saying I should turn my JMP into a JCM800 

I think I have enough jacks left to build an ABY box.

I kept reading about relay & opto / fet switching. One other thing I didn't think about was delay between switching channels.
But relays and FETs are fairly cheap so I might give it a try too.

They're not saying convert to a JCM800. They're simply saying jump the two channels together. BTW, JMP is not a single amp. It's a whole series of amps. Same with the JCM-800 series.

You don't need an ABY box. Just plug your guitar into the Bright channel "High" jack and use a short patch cable to connect the Bright "Low" jack to the Normal "High" jack. Now use the volume controls to blend the bright and normal channels together. The sound is way better than the sound of either single channel. I think you will be so pleased with the tone possibilities that you will always want to play that way. You'll never go back to single channel again, so an ABY box would be useless for this amp.

There should be no audible switching delay using relays, optocouplers, or FETs.

[warioblast]

So you guys are basically saying I should turn my JMP into a JCM800 

I think I have enough jacks left to build an ABY box.

I kept reading about relay & opto / fet switching. One other thing I didn't think about was delay between switching channels.
But relays and FETs are fairly cheap so I might give it a try too.

They're not saying convert to a JCM800. They're simply saying jump the two channels together. BTW, JMP is not a single amp. It's a whole series of amps. Same with the JCM-800 series.

You don't need an ABY box. Just plug your guitar into the Bright channel "High" jack and use a short patch cable to connect the Bright "Low" jack to the Normal "High" jack. Now use the volume controls to blend the bright and normal channels together. The sound is way better than the sound of either single channel. I think you will be so pleased with the tone possibilities that you will always want to play that way. You'll never go back to single channel again, so an ABY box would be useless for this amp.

There should be no audible switching delay using relays, optocouplers, or FETs.

Steeve, My JCM800 remark was a joke. Oh well...

I have tried to jump my channels. What I'm really missing from my DSL50 is having a clean and a dirty channel. I understand that you can put a boost in the chain with the ABY and somehow deal with volume discrepancies between a clean and a dirty sound.

"There should be no audible switching delay using relays, optocouplers, or FETs. " Well sometimes there is a delay, and as a matter of fact my DSL50 had a short one.

[sluckey]

Joke... Yes, I saw that.

DSL50??? I thought you were talking about a JMP series amp?

[warioblast]

I'm talking about a 1987 circuit that used to be a JTM50 that was built using a DSL50. 
http://el34world.com/Forum/index.php?topic=21066.msg223171#msg223171

[warioblast]

I found the schematic of the Friedman Small Box 50W and I'd like to steal some ideas from it. For instance the relay switching 
Do you think I can use the bias tap of my transformer to power the relays ? It's 20V, so after rectification it should be around 28V ?
The max input voltage for the 12V regulator is 35V. It should be fine, shouldn't it !?

Also why is Friedman using 5V relays 

[sluckey]

A properly working bias supply is crucial to the life of your tubes, OT, and maybe even the PT. If it dies all of those things are in harm's way. I personally would not add stuff onto the bias supply.

Using 6.3VAC filament voltage to source a 5 volt power supply will easily power a small 5 volt relay.

Also why is Friedman using 5V relays

Why do you say Friedman is using 5 volt relays? I don't see anything on that schematic that suggests he used 5 volt relays. He does have a dedicated 12 volt supply and that suggests to me that his relays are 12 volt coils.

[warioblast]

The bias tap from my PT is unused.

I've seen other schematics from Friedman. The amps use the same power supply arrangement for the relays which are "G5V-2-H1". I assumed they were all rated 5V. I just checked and G5V is the name of the series that goes from 3 to 48V. That didn't make sense. You were right they have to be 12V.

[PRR]

24V AC rectified to ~~28V DC will power "24V" relays just fine.

One such is G5V-2-H1-DC24, 24 VDC, DPDT, Coil Current 8.33 mA.

Your not-Bias winding is 20V-0V-20V? Two rectifiers, two caps, a resistor. See attached.

The G5V will work 75% to 120% of nominal voltage, no regulator needed.

[warioblast]

Many thanks PRR. The bias winding is 20V-0-20V indeed.

How do I choose the value of the flyback diode ?

[PRR]

1N4007

[warioblast]

Thanks. 

[warioblast]

I carried on my investigations. Now I'd like to have a Fenderish clean channel by adding a 12AX7.

I attached 2 examples. 1st one is from the Friedman BE100 and the 2nd is from the sloclone OD3.
How do you calculate or choose the values for the inter-stage attenuator and grid leak resistors ? (I think that's how you call them)
Respectively R15 & R22 for the Friedman and R94 and R93 for the sloclone.