Simul-Class SWitch on IIc+

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RocketRick

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I'm trying to understand exactly what this switch does.

the 6/84 invoice reads:

100 Watt Chassis with Pwr Selector Switch and Fan
Simul-Class Modification

I read that when down, the switch gives 15watts and when up gives 75watts.

Yet the invoice shows 100 Watt. It did come with 4 6l6 tubes-matched set and still in.

Seems like I remember it was 60wtts down and 100 watts up but not sure.

Anyone have an idea on this question?

thanks
 
You are right. If you have a Simul-Class/Class A switch you will get 75W and 15W respectively. The other transformer option was the 60/100W model so that's probably why the Simul-Class was listed as an upgrade option on the form from the stock 60/100 option.

Hold onto those tubes...they are STR415s and are amazing. I would get some nice EL34's for the outer sockets so you have a spare set of 415s for your inside pair.
 
Platy, platy, platy....

1. Again, if i ordered the 100 watt option why is the map not a 60/100 watt amp? I don't understand.

2. All the tubes are the orig and it perfect condition . Even the extra 12ax7 in the plastic holder.

3. In a land far away and loooong ago I ordered 3 extra 12AX7's and a matched pair of 6L6GC-WC tubes. I was wondering why I ordered the 6L6 tubes. Must be to make sure I have extras.

Blame it in a senior moment Ha!.

thanks for responding. :)
 
You may have a Simul-Class amp, or you may have a 60/100 watt amp, but not both.
No such animal as a "Simul-Class 60/100 watts".
If it's a 60/100, you cannot put EL-34s in the outer sockets.
If it's a Simul-Class IIC+, it's 15/75 watts, never 60/100.
Never.
"Simul-Class" and "60/100" are two separate and totally different amps. You may have to check the output transformer numbers with Mesa to be sure.
By the way, a 100 watt amp is not 25% louder than a 75 watt amp.
For that you need almost 200 watts.
 
RocketRick said:
Platy, platy, platy....

1. Again, if i ordered the 100 watt option why is the map not a 60/100 watt amp? I don't understand.

2. All the tubes are the orig and it perfect condition . Even the extra 12ax7 in the plastic holder.

3. In a land far away and loooong ago I ordered 3 extra 12AX7's and a matched pair of 6L6GC-WC tubes. I was wondering why I ordered the 6L6 tubes. Must be to make sure I have extras.

Blame it in a senior moment Ha!.

thanks for responding. :)

It's one or the other... look at the switch on your amp :p
If it says 60/100 but the invoice says Simul upgrade you'd have to take a pic of the inside of the chassis for us to be sure.

Based on what you're saying, it sounds like you ordered the 60/100W amp but received a Simul-Class amp?

If you're willing to part with those 415s let me know ;)
 
Platy,

The switch down is Class A. Up its Simul-Class.

Well the inside has what looks like 4 pre-amp tubes and 4 large output ones. 60 or 100?

Here's the pic;

BackofBoogie.jpg
 
:shock: Nice amp, that's considered to be the most sought after C+ out there.. hardwood combo with EV12l with the export tranny and simul-class, especially if it has EQ.

It's safe to assume it's simul class because of the switch and the invoice, not a 60/100W amp. If it were 60/100 the switch would read 100 in the up position and 60 in the down position.

It's highly highly doubtful that it's a 60/100 but stranger things have happened... if you want to be 100% sure we'd need inside the chassis pics but I'd say it's **** near 100% sure. (example, I have a simul amp that some dumbass sent back to mesa to have rewired in the outer sockets as well as changing the bias resistor.. I promptly had it restored to factory condition)

Hold on to that thing forever.

And I'm serious about those spare 415s ;)
 
Platy and gts,

Yeah I know. I was offered $2k abt 5+ yrs ago for it. Plus I got the metal road case. Can't rem its name but its skoocum..

I have all the shipping data, all the invoices and even the letter from R himself. Still has the tech check tag on it.

Well In know my tech here can tell me by loading it up ot looking at it. Kinda of a pain tho.

What about if I give ya all the nos off the chassis et al?
 
RocketRick said:
Platy and gts,

Yeah I know. I was offered $2k abt 5+ yrs ago for it. Plus I got the metal road case. Can't rem its name but its skoocum..

I have all the shipping data, all the invoices and even the letter from R himself. Still has the tech check tag on it.

Well In know my tech here can tell me by loading it up ot looking at it. Kinda of a pain tho.

What about if I give ya all the nos off the chassis et al?

It's certainly worth more than 2k.

The chassis code on the side of the chassis (you'd have to remove it from the combo, kind of a pain) should read DRGX if you have the EQ on the front. A picture of the inside of the chassis where the power tubes are wired would tell us for sure.. but it's pretty much guaranteed you have the simul option, which is the more desireable of the two.
 
but it's pretty much guaranteed you have the simul option, which is the more desireable of the two.

So its 15watts in Class A mode and 75 in the simul-class mode?
 
RocketRick said:
but it's pretty much guaranteed you have the simul option, which is the more desireable of the two.

So its 15watts in Class A mode and 75 in the simul-class mode?

Yes.

You can also run EL34's in the outer sockets (ie position 1 and 4 only. if you number the output tubes left to right 1 2 3 4). In the class A mode on the toggle this only uses the outer tubes so you can run your preamp through a pure EL34 power section, or have the added versatility of a mixed power section.
 
RocketRick said:
so you can run your preamp through a pure EL34 power section, or have the added versatility of a mixed power section.

Please clarify that info...


Ok. You can run EL34s in your outer power tube sockets, so tubes 1 and 4 on the back with the two middle ones staying 6L6s. Then, if you choose the Class A toggle, it kills the two inner tubes out of the circuit so you're running your amp through 2 EL34s at that point only. Does that make sense?
 
Platypus said:
RocketRick said:
so you can run your preamp through a pure EL34 power section, or have the added versatility of a mixed power section.

Please clarify that info...


Ok. You can run EL34s in your outer power tube sockets, so tubes 1 and 4 on the back with the two middle ones staying 6L6s. Then, if you choose the Class A toggle, it kills the two inner tubes out of the circuit so you're running your amp through 2 EL34s at that point only. Does that make sense?


Make sure that you check that pin#1 is grounded on the power tube circuit board (outer sockets only) before using the EL-34's in these positions. Ask me how I know :shock: .
 
OK Joey I'll try that. Don't need a diagram..

Where's the best place to get some EL-34's and which ones. There are a quite a few diff manufs.

This has been an enlightening thread for me. I bet there's some more cool things to do with this amp.

My latest joy has been playing it thru a Marshall 2x12 cab.

I also want to try out some vintage 30's.

thanks
 
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