MESA MARK I...... AWESOME!

Yeah, so I found out the amp I just bought is a 70s Mark I combo equipped with a EV SRO speaker.
At first I had trouble dialing in a good tone. I think the trick is not to turn both preamp vols up too high. I took out the Chinese tubes and put in a pair of NOS Tung Sol 5881s and some good USA pre amp tubes.
After playing with the vols a bit, this little amp screams! Notes holding out forever. Very pleased. Anyone else hip to the Mark ones?

Hmmm, Tung-Sols. I wonder if the voltage in the MKI will kill them prematurley?

Russ,
What kind of plate voltages are normally found on a mark I?
I would think the Tung Sols would hold up better than the cheapos that were in there before. There is no bias adjust, and the plates aren't glowing red. :? Is there something I'm missing here?
BB

Tung-Sol 5881's are a 23 watt tube, rated for 360 plate volts. Fender Twins and Super Reverbs are known to "eat" them right up. Plate voltage in a Mark is similar. The MKI has around 450 plate volts.

All I'm saying is that even though they may sound great, they may not last too long. It would be good to measure your plate volts and current draw. Tung-Sol 5881's go for $180 a pair from KCS NOS Tubes!

That said, Tubes have been run past their ratings ever since there were tube amps for guitars...but then again, great new tubes were once cheap and plentiful...things are getting better in that regard, though.

Wow! Only 360V ? Thats about the same as a 6V6 isn't it?
I'll have to pull them until I can check the plate voltage.
How about some old RCA blackplates? I also have some Philips 6L6s.
Is it possible to run 6V6s if the voltage is low enough?

Hey Russ,
I put in a pair of Philips small bottle 6L6s. I hope these will be ok.
I think the amp sounds even better now!
BB

Small bottle Phillips 8)

You taunt me with your NOS tubes...

I have new Shuguang/Valve Arts/TAD Big Bottles in my 50cal. It's a copy of the RCA blackplates, yada, yada...they sound pretty good! (and $35 a pair)

I thought you always had to use Mesa tubes in Mesa amps because of the fixed bias. Won't other brands of tubes burn out faster or hurt the amp or is this just a myth?[/quote]

I agree. What is the deal with switching power tubes. I was looking at getting some JJ 6l6's, but then do I have to get my amp biased?

Geez Mike, I heard you the first time!

No biasing nessessary, when you order your power tubes, just specify that you have a Boogie MKI, and the good vendors will "hook you up"

Mesa dont make their own tubes anyway, they just select the sovteks or chinese ones which are within their bias range.

btw- Try hitting 'submit' once next time.

The first thing I did when I got my MK I RI was to have my tech add a bias pot. It's a simple fix.