Mark III - Simul-Class Confusion

[steve_k]

A few Q's foe the Mark III or Mesa experts:

1. Are all Mark III's Simul-Class?

2. Is the full and half power switch on some of the wide heads he same as the Simul-Class / Class A switch on the back of the narrow bodies?

3. What is the difference in 100W/60W nomenclature?

These may be answered deep within the bowels of page 300 of this forum, but appreciate the answers!

Thx,
Steve

 

[av8or3]

I'll give this a go.....

#1 No.
#2 No. I think....I've seen the 1/2 power switch on the Coliseum's (180 Watt) and I don't believe that has any thing to do with
Simul-Class. I think if it's Simul-Class it will be labled Simul-Class/Class A. I know this to be true on short chassis w/no GEQ
and long chassi w/wo GEQ.
I think that the 1/2 Power switch functions the same as the 100/60 switch, that is it cuts out some of the 6L6's to reduce the
output of the amp.
#3 On the 100/60 amps the switch on the rear of the chassis is labled 100 at the top position and 60 RMS at the bottom position.
You use this switch to turn on/off the outer two tubes.

You more learned folks are welcome to jump in and correct me if needed.
Jim

 

[dodger916]

From the "IIC+ for Dummies" (second sticky in this sub-forum): Long chassis face plates can have a Full PWR / 1/2 PWR switch on the front. The only way to determine what effect the power drop will be is if you know your amp is a 60/100 or Simul-Class. Some C+'s did not come with a Simul-Class sticker. The identity can be found by looking at the output transformer part number. For the 300 Series, it will drop the center two of the six 6L6's for the 180 Watt and 2 outer sockets on Simul-Class models.

Granted, this applies to a C+, but I'd wager the same holds true for Mark IIIs. The way to know for sure is check the output transformer. It should say "Simul-class" and/or have an SC designation in the serial number.

 

[JOEY B.]

A few Q's foe the Mark III or Mesa experts:

1. Are all Mark III's Simul-Class?

2. Is the full and half power switch on some of the wide heads he same as the Simul-Class / Class A switch on the back of the narrow bodies?

3. What is the difference in 100W/60W nomenclature?

These may be answered deep within the bowels of page 300 of this forum, but appreciate the answers!

Thx,
Steve

1. NO

2. It is on my "green stripe" Simul/EQ/Reverb long chassis head.

3. 100/60 is wired all Class-AB pentode for the power section, Simulclass has the outer left and outer right power tubes wired in what they now call "exteded class-A". They are biased hotter and have the option of running EL-34's in these sockets. The switch on either the 100/60 or simulclass model cuts the inner pair of tubes out of the circuit. 8)

The series 300 Coliseum model is another story. I've owned two of them.

 

[dodger916]

A few Q's foe the Mark III or Mesa experts:

1. Are all Mark III's Simul-Class?

2. Is the full and half power switch on some of the wide heads he same as the Simul-Class / Class A switch on the back of the narrow bodies?

3. What is the difference in 100W/60W nomenclature?

These may be answered deep within the bowels of page 300 of this forum, but appreciate the answers!

Thx,
Steve

1. NO

2. It is on my "green stripe" Simul/EQ/Reverb long chassis head.

3. 100/60 is wired all Class-AB pentode for the power section, Simulclass has the outer left and outer right power tubes wired in what they now call "exteded class-A". They are biased hotter and have the option of running EL-34's in these sockets. The switch on either the 100/60 or simulclass model cuts the inner pair of tubes out of the circuit. 8)

Joey: I thought only the Green Stripes were pentode. Is there (another!) hole in my understanding?

 

[JOEY B.]

Joey: I thought only the Green Stripes were pentode. Is there (another!) hole in my understanding?

All 60/100 Boogies ar Class AB pentode. The Simulclass green stripe has the outer pair wired in Extended Class-A pentode. The other stripes have the outer pair wired in Extended Class-A triode. The inner pair of tubes is always Class AB pentode, regardless of stripe color. I have installed a switch on my outer pair of sockets that lets me choose between pentode or triode.

Again this does not apply to the series 300 models.

 

[steve_k]

Muchos Gracius.....


Steve

 

[dodger916]

Joey: I thought only the Green Stripes were pentode. Is there (another!) hole in my understanding?

All 60/100 Boogies ar Class AB pentode. The Simulclass green stripe has the outer pair wired in Extended Class-A pentode. The other stripes have the outer pair wired in Extended Class-A triode. The inner pair of tubes is always Class AB pentode, regardless of stripe color. I have installed a switch on my outer pair of sockets that lets me choose between pentode or triode.

Again this does not apply to the series 300 models.

Thanks again! Frank