Matchless Chieftan - WTH

[lowell]

So this combo came in with low volume and distortion. I checked the bias and was shocked. 70ma per EL34. Plate volts are 430v. So I figured these tubes are toast and put a new pair in. Same result.

I subbed in an OT, and checked the Rk' s etc... all this only to see on the schematic that this is CORRECT! So...WTH.

In the schematic it has 24v/270ohm on cathode. 89ma!! At 430v Ra that's 38watts!!

Please someone tell me there's a reason for this. They have "special" EL34 they use from the factory right? 藍

http://www.thetubestore.com/lib/thet...-Schematic.pdf

[TimmyP1955]

I'd think that there ought to be a resistor after C9 and C18 (if I am reading the numbers rightly). As it is, when the master is at zero, V5A and V5B are driving each others' plate resistors in parallel with their output impedances. Seems as though this would compromise the performance at low MV settings.

[Leo_Gnardo]

In the schematic it has 24v/270ohm on cathode. 89ma!! At 430v Ra that's 38watts!! Please someone tell me there's a reason for this. They have "special" EL34 they use from the factory right?

Not only are the Matchless amps intended for deep pocketed rock (and country) stars, their need for constant maintenance (read output tube changes) keeps them out of reach for ordinary folks. No, there is no "special" EL34. Just a special disregard for real world operating conditions by the designer/manufacturer. Dont'cha know, it's hip to run your output tubes at red plate heat, and put in a new set for every gig. Maybe every song. Carry plenty of spares, plus a pair of oven mitts. Phooey!

I've tried increasing the cathode resistor but by the time plate current is brought down to a sane level, the output is in deep crossover distortion. Can you tell, they're not my favorite amp?

[Justin Thomas]

Not to mention, that "Master Volume" is just a courtesy. It was never really intended to be used below "10" anyway...
All joking aside, it was meant for shaving off a little bit, not getting Rawk in the living room.

Justin

[Leo_Gnardo]

Not to mention, that "Master Volume" is just a courtesy. It was never really intended to be used below "10" anyway...
All joking aside, it was meant for shaving off a little bit, not getting Rawk in the living room.

Justin

But dont'cha just luv the way their logo lights up, ain't that special? All the guys in Pelvis Parsley's band got one'a them Matchless amps on the Hootenanny show, I gotta get one too!

[Enzo]

Think of it as a class A amp, and then you ignore the high current.

[J M Fahey]

Killer sounding amps, they are what they are, and if you don´t like them, just don´t buy them.
I do regular maintenance on the few available in Argentina (less than a dozen) and players love them.
They run so hot that the plastic front panel bends.
I added a 12V fan fed rectified 6.3V (about 7 or 8 V DC) so they just blow a gentle breeze and owners clip one wire to stop them, claiming "sound is not the same" ... who am I to disagree?

A common problem is that power tube cathode caps dry up , at least once a year, check that.

[The Dude]

One of my favorite guitar tones for a semi-distorted sound is Todd Nichols (Toad the Wet Sprocket), who plays a DC30.

[J M Fahey]

I'd think that there ought to be a resistor after C9 and C18 (if I am reading the numbers rightly). As it is, when the master is at zero, V5A and V5B are driving each others' plate resistors in parallel with their output impedances. Seems as though this would compromise the performance at low MV settings.

That´s the idea.
Both plate signals mix ... out of phase.
When MV pot is set to 0 ohms, combined output is also 0 VAC.

Even if it were not, same signal drives both power tube grids ... which again are out of phase so they cancel whatever small signal *might* have survived.

"Brilliance" control does the same, but at high frequencies ... and it´s just the 60 years old VOX "Cut" tone control.

[TimmyP1955]

That´s the idea.
Both plate signals mix ... out of phase.
When MV pot is set to 0 ohms, combined output is also 0 VAC.

Even if it were not, same signal drives both power tube grids ... which again are out of phase so they cancel whatever small signal *might* have survived.

"Brilliance" control does the same, but at high frequencies ... and it´s just the 60 years old VOX "Cut" tone control.

I understand the concept - it's how the level control on a Leslie 122 works. It just seems odd to me to load down the PI so much. A resistor in series with each leg should not affect the phase cancellation, just ease the load on the PI.

[Leo_Gnardo]

One of my favorite guitar tones for a semi-distorted sound is Todd Nichols (Toad the Wet Sprocket), who plays a DC30.

I wonder if he got his semi-distortion by dialing down the bias current with a bigger cathode resistor, and we're hearing krossover krunch. Not a bad solution, if you like that tone.

[Chuck H]

I wonder if he got his semi-distortion by dialing down the bias current with a bigger cathode resistor, and we're hearing krossover krunch. Not a bad solution, if you like that tone.

You can get a lot cooler than idling a 25 watt tube at 38 watts and still avoid crossover distortion. That's just ridiculous. Juan reports that players love the sound of these Easy Bake Ovens though and I guess anything done to cool them off would be sacrilege.?. Nothing clever to say. Just shaking my head. If it were "my" amp I'd cool it off.

[J M Fahey]

This is one of my customers, listen and judge for yourself:

by the way, this is not Rock, Blues, Pop, etc. but one of our popular Folkloric songs, just played with electric instruments.

[Leo_Gnardo]

This is one of my customers, listen and judge for yourself:

by the way, this is not Rock, Blues, Pop, etc. but one of our popular Folkloric songs, just played with electric instruments.

Kool, they got the blues in Argentina! Can't argue with his tone nor playing. Do I see an AKG C-12 on the kick drum? Holey crow - spare no expense!

[Chuck H]

This is one of my customers, listen and judge for yourself

Sounds amazing! Great tone. Great playing. Great voice too and nice arrangement and performance overall You don't need to qualify genre on that clip because the artists seem very good at bringing a more contemporary sound to the work. Fortunately for him modern el84's are pretty good with excess current (and don't I enjoy that myself!). But WRT el34's as above I would be (have been) more concerned about modern offerings.