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OK. I'm a dummy. Just ignore my tube numbering system because I'm wrong. On my amp the inner pair of power tubes would be numbered V3 & V4, and the outer pair would be V5 and V6. You'd think I don't know how to read a schematic or a tube use chart...and you'd be right. Sorry for any confusion.

Thanks.

Did you ever run the MKIV with the R1 Master up high and the R1 Vol control at about 3, like I was doing?

Probably not, but maybe. I bought mine new in approximately 1997. Did the A's come in the wide-body cabinet with the Celestion 90 watt speaker? That's what I had.

The MKIV's that came with EV's were front loaded like most of the MK series amps. I used to own a MKIV wide-body combo with the Celestion 90 watt speaker and it was rear-loaded. It was ***** trying to swap out and try various speakers in that cabinet. Nowadays, Mesa is only using the...

I used to own a MKIV wide-body combo, with the Celestion. I found the reverb was really noisy when it was used. Some of you rock guys probably wouldn't notice it. But I used to use that amp in a jazz big band and whenever it got really quiet the hum from the rverb became really noticeable. I...

Mike Bendinelli has told me that this is a misprint in the MKIV's manual. The MKIV in "Class A" Triode puts out about 15 watts (like the old SimulClass amps, MKII, early MKIII). In "Class A" Pentode it puts out about 30 watts (like the 2:90's "Class A" tube pair). These ratings are for Full...

BTW Mike Bendinelli at Mesa just told me that the bias voltages for my amp should be: -47V on the outer pair (The "Class A" pair) -52V on the inner pair (The Class AB pair) [He thinks that my tech probably took a fauly reading with his "8 volts difference between left and right pairs" and...

I wish I knew what that means. <g> Are you trying to tell me that all the pentode/triode switch does is to send a different bias voltage to the the Class A tubes, but they still run in triode? Then why does he call it a "pentode/triode switch"?

?? I don't follow how the information I've told you leads you to make the above comment? The inner pair are in within 10% of "what"? Did you understand what I said about the 8 volts difference in the bias voltages? That V3 and V4 have the correct voltages but the voltages at V5 and V6 are...

Let me clarify something I said in my last post. It's not that the outer tube pair and the inner tube pair have bias readings that are 8 volts off from each other. It's that the two left-most tubes and the two right-most tubes have the 8 volts difference. I.e. One side of the entire parallel...

You can see the switch in the MKIV schematic found here: <http://www.tubefreak.com/mk4-4.gif>

Well I wish I understood that because it's probably being really helpful. Are syaing that switching this switch to the Pentode position does not really run those tubes in pentode but does something else? Thanks for listening to my rants and baby-sitting me, by the way. So...Have I...

Well...To make thing's even weirder, for me at least, and with the effect of making me look like a total idiot... It turns out that the Simul Satellite may already have the "Class A" tube pair running in Pentode. At least this is what a tech I have looking at my amp right now is trying to tell...

Just curious... Do you actually own a 2:90 or have you spent a lot of time playing them? If yes, and you're sure about the "Deep" mode on the 2:90 affecting the negative feedback then I'll just take your word for it. But, like I said, I don't recall it acting that way when I was renting a...

What's too bad? Well I actually did spend some time reading the patent(s): 4,593,251 and the other one, 4,532,476, which seems to be the same thing. Of course, tech talk like this is well beyond me. But it looks like those patents are saying that Mesa's "Class A", as implemented in the...

Well, that's not what I got from that article. I thought he was spending all that verbiage to make the true Class A circuitry of the Lonestar Special more widely understood. In the brief discussion of SimulClass he makes it sound like it too is true Class A power, by the RCA handbook's...

That may well be. It's been a couple of years since I sold my MKIV. Not sure how it's relevant though. The Push-Pull pot on the Satellite's Presence knob is a whole other animal. Well, like i said, when I rented a 2:90 I don't remember that being the case. I may rent it again to check that out...

Hmm. I thought that's what "Modern" was. My Simul-Satellite has a Pull Shift function on its Presence pot. The Shift setting (i.e. pulled) is the norm though and when pulled the Presence control works like the Presence control my old MKII had on the back. When the pot is not pulled there is an...

Well I appear to be right about some things and wrong about others, from Mr. Smith's POV at least. Here's what he says about Simul-Class: "Many Simul-Class amplifiers also ran the Class A pair wired for Triode operation. This means that the screen grids of those two tubes are wired to the...