Switch for the 18watt Plexi?

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cstenger5
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Switch for the 18watt Plexi?

Post by cstenger5 »

Howdy folks, I'm looking over the layout and schematic for the 18w Plexi, and I think I'm going to start building a BOM and get ordering. What type of switch is used for the Y/cascade function? And for that matter, does anyone have a BOM premade for this (for my lazy ass)? Thanks in advance!
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Re: Switch for the 18watt Plexi?

Post by Daviedawg »

Welcome to the forum.

If you go to the Downloads section on the left you will find documents on the 18w Plexi.

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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

Thanks Dave, I do have the docs and I'm building the bill of materials. I just wasn't sure what type of switch is referenced for the Cascade switch.
Thanks for the welcome. I've been soaking up everything here like a sponge and it has helped tremendously. I'm looking at my first two builds with a completely new set of eyes after seeing all the advice here.
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Re: Switch for the 18watt Plexi?

Post by ViperDoc »

The switch(es) you select will depend on how you want to control the cascade. Will it be a set-it-and-forget-it kind of thing, or do you want to control it on the fly? You can use a panel-mounted mini-switch or push-pull pot for the front of the amp, or run that option in series with a foot pedal. I've only ever put EQ-bypass boost on foot switches myself.

Check these out: https://www.tubesandmore.com/products/s ... older-lugs
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Re: Switch for the 18watt Plexi?

Post by JMPGuitars »

Personally I don't like mini switches for the cascade switch. I use a DPDT Carling switch, same size / rating as the mains switches on my amps.

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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

Thanks Josh. That's the same as I did for a nfb loop on added to my vibrolux build to keep all it uniform.

I'm so stoked to have found this forum. Thanks to all for all the great info.
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Re: Switch for the 18watt Plexi?

Post by ViperDoc »

JMPGuitars wrote:
Sat 09/11/21 10:53 am
Personally I don't like mini switches for the cascade switch. I use a DPDT Carling switch, same size / rating as the mains switches on my amps.

Thanks,
Josh
Do you think the mini switch is too under-rated? I’ve never done a cascade switch, so perhaps when I do, I’ll follow your advice.
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Re: Switch for the 18watt Plexi?

Post by JMPGuitars »

ViperDoc wrote:
Sat 09/11/21 8:21 pm
Do you think the mini switch is too under-rated? I’ve never done a cascade switch, so perhaps when I do, I’ll follow your advice.
Probably, but not only that, they're difficult to use with the appropriate gauge wire. I only use those mini toggles for low current or low voltage stuff. Like a bright cap in a reverb circuit, or the bright/fat switch on the Superlite TMB. Otherwise I only use them in pedals.
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Re: Switch for the 18watt Plexi?

Post by geoff 1965 »

Depending on which cascade you use comes into this,if you use ZP’s version or similar where the switch is handling plate voltage then I would definitely use a large switch.i used a mini toggle on/on to cascade the normal channel into the TMB channel but that is only directing AC signal voltage.if I remember I had to ream the holes out slightly on the switch for the wire to fit like Josh mentioned.
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Re: Switch for the 18watt Plexi?

Post by zaphod_phil »

geoff 1965 wrote:
Sat 09/11/21 10:16 pm
Depending on which cascade you use comes into this,if you use ZP’s version or similar where the switch is handling plate voltage then I would definitely use a large switch.i used a mini toggle on/on to cascade the normal channel into the TMB channel but that is only directing AC signal voltage.if I remember I had to ream the holes out slightly on the switch for the wire to fit like Josh mentioned.
I would really *not* be happy with the cascadeswitch having to handle anode voltages. That will cause some pops and bangs! IMO it should only be witching the signal chain to get the different gain levels, like the relay in the attached shematic of Trinity's SIII One.
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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

This tangent discussion has me really interested in learning some theory about switch placement. I'm new enough (only Vibrolux and Mojo 18TMB builds under my belt so far, which I'd have built differently had I found this site earlier) that I haven't done any internal channel or cascade switching. I infer that there's a lot that can be done architecturally with multipole switching for adding or removing segments of a circuit, but I have no experience with execution of that.
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Re: Switch for the 18watt Plexi?

Post by geoff 1965 »

i’ve been at this 4 or 5 years now but still feel like a novice at times,it’s a constant learning progress but I love it!
which actual schematic/layout are you referring to,the Johnson 18W plexi in the downloads section or the trinity ZP mentioned?
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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

I had been looking at the one posted here. I hadn't looked at the Trinity docs, but I did get some good help from Patrick during my 18 tmb build via Facebook.
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Re: Switch for the 18watt Plexi?

Post by geoff 1965 »

The Richard Johnson plexi in the downloads is quite old now “2009” but still looks like a good amp,I notice his tweak notes of 1000 or 2200uf on the el84’s bias for a tighter feel,something most people are using now!
The trinity amps are more up to date plus “ZP” one of the senior amp techs has worked with them so his contributions are worth taking note of.
Good luck with the build
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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

The Zaphod name alone tells me to pay attention. If it makes any sense to anyone but ZP, my handle was often slartybartfast in the past. If that doesn't make sense to you, please just ignore it :-).

I looked over the trinity 18 watt Plexi Mark 2, and it looks like exactly what I'd like to do - particularly with the cascade switch.

To show my level of novice-ness, once I do start putting it all together I'm going to have to ask for help in situating that switch within my layout. I get the logic aspect of it in the schematic, but without it represented in the layout I'm going to lack confidence in placing it properly.
I've also got one of Trinity's VRMs, and this would be an excellent project to use it in.
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Re: Switch for the 18watt Plexi?

Post by zaphod_phil »

slartybartfast makes lots of sense to me, as I'm a hoopy frood who knows where his towel is! :lol: I've actually been around some years in the DIY tube amp world, including on 18watt.com. Unlike you, I've never tried building planets or designing fjords :)
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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

Coastlines I can do, amps are another story - but I'll get there.
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Re: Switch for the 18watt Plexi?

Post by Daviedawg »

We all love Slartybartfast

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Re: Switch for the 18watt Plexi?

Post by cstenger5 »

Well I'm *clearly* among friends here :)

Looks like I'll do the Trinity MkII version. Seems pretty straightforward, but I'll absolutely have some dumb questions to pepper you guys with along the way.
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Re: Switch for the 18watt Plexi?

Post by zaphod_phil »

cstenger5 wrote:
Tue 09/14/21 7:38 am
I'll absolutely have some dumb questions to pepper you guys with along the way.
Each time, you'll get the answer "42" :lol:
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