What's in a Mars Specialist?

[yowza]

They take an old Filmosound chassis gut it and build a new amp inside. I recall something about Bell and Howell transformers.

There's a Youtube clip out there of Lance Keltner playing one, it does sound really sweet.

http://atmarsamps.blogspot.com/

[The New Steve H]

You can see that the amp I posted has a big octal in the preamp, while the one hired hand posted has a 12AT7 and a 12AX7. I guess they vary?

Not sure why the photo with four loose tubes has four octals, which would be consistent with the first amp, not the second.

The variable power switch is a mystery. They wouldn't need it to switch between 8 and 16 ohms, since you can do that with two jacks and no switch. I see it isn't included in the newer amp.

I would be afraid to trust a crusty old transformer like that. Isn't there a pretty good chance the laminations are getting to an age where they'll start shorting?

More info: I logged into the Gear Page and read about the amp. The owner confirms it's a 12AX7 and 12AT7. The cabinet was built by the first owner, not Mars.

[camerongrieve]

*** "I would be afraid to trust a crusty old transformer like that. Isn't there a pretty good chance the laminations are getting to an age where they'll start shorting? "***

I'm sure I've read an article (somewhere, and it may or may not be total BS) about old power transformers oozing with Mojo ... something to do with the rust forming an insulating layer between laminations, if I remember correctly.
I've used a few old transformers myself, without trouble. If you're worried, and have access to one, test it with a megger.

[The New Steve H]

I wish I had access to a 5E3 and/or a Specialist, so I would know for sure what to expect. It looks like we're going to build an amp; I don't want it to be a disappointment.

I'm thinking we'll use the best info we have, which means 12AX7, 6SL7, two 6V6s, and no extra doodads.

If anyone has any idea how the 7w/18w switch works, I would love to know.

Just to clarify, this is an actual amp for a non-imaginary friend.

I will have to gather info on point-to-point building.

I appreciate all the help. Especially the photos.

[Zippy]

You can see that the amp I posted has a big octal in the preamp, while the one hired hand posted has a 12AT7 and a 12AX7. I guess they vary?

Not sure why the photo with four loose tubes has four octals, which would be consistent with the first amp, not the second.

The variable power switch is a mystery. They wouldn't need it to switch between 8 and 16 ohms, since you can do that with two jacks and no switch. I see it isn't included in the newer amp.

From the Mars website (highlighting added):

"The guitar amplifier built most often by At Mars Amplification is The Specialist. This amp is driven by a pair of 6V6 power tubes with the power supply rectified by the 5Y3 rectifier tube. The front end normally uses a 12AT7 and 12AX7 for the preamp and driver/phase inverter. However both of these tubes can be substituted  with any tube from the 12AU7 family to provide a variety of gain structures based on your preferences. The Specialist is a cathode biased amp and puts out about 15 watts.  The combination of the cathode bias and it's uncommon phase inverter makes the amp very “touch sensitive”. Although normally the amp starts to dirty up at about “3”on the dial,  adjusting your pick attack or rolling back your volume knob can take the amp from dirty to clean without the use of a stomp box. The amp responds to how hard or soft your pick attack is, so you can control the amount of distortion with just your fingers and the strings of the guitar."

"Although this amp might be considered “low power” at 15 watts, it is not a practice or bedroom amp. It can be surprisingly loud especially with efficient speakers. Running the amp half way open is the kind of fun that makes your ears ring. All chassis have eight ohm speaker taps and many have a 16 ohm tap as well, allowing you to run a variety of different speaker configurations."

[The New Steve H]

I guess my imaginary friends should have told me to go to the Mars site.

[yowza]

There is a version of the Specialist that has a 6SL7 preamp tube because if you go to the link I put in my previous post and scroll down the page and click on the first demo video, Lance Keltner is talking about it and playing through it and he specifically mentions the 6SL7 tube. Not sure if it's a custom option or a special amp they cooked up just for him, maybe they started out with that version and later switched to 12A_7 tubes.

It sounds like there could be more to this amp than just a 5E3, cathode biased amp, specifically something about the Phase Inverter being different so unless you have gutshots or another amp to look at to clone from who knows if you'll really be building that particular amp.

[Zippy]

It sounds like there could be more to this amp than just a 5E3, cathode biased amp, specifically something about the Phase Inverter being different so unless you have gutshots or another amp to look at to clone from who knows if you'll really be building that particular amp.

The 5E3 uses a "less common" phase inverter - ie not a LTP.

Is there ANYTHING about a 5E3 that does NOT fit their description?

[yowza]

The 5E3 uses a "less common" phase inverter - ie not a LTP.

Is there ANYTHING about a 5E3 that does NOT fit their description?

Very true Zippy, my point was that without seeing what's inside how does he know he's really building that particular amp? If it is a just simple cathode biased 5E3 (with cathodyne PI) then cloning a version of that may well be enough but if they did anything else out of the ordinary maybe it won't sound the same.

Respectfully,

Ed

[tubeswell]

Old atmars pops up here from time to time Steve. http://music-electronics-forum.com/t12702/ If you join than forum you can PM him and ask him yourself.

[The New Steve H]

How would he feel about me asking him how to clone an amp so my buddy can avoid buying his product?

[The New Steve H]

Well, it looks like he posted some schematics and a lot of info. Thanks, Tubeswell.

[Zippy]

The 5E3 uses a "less common" phase inverter - ie not a LTP.

Is there ANYTHING about a 5E3 that does NOT fit their description?

Very true Zippy, my point was that without seeing what's inside how does he know he's really building that particular amp? If it is a just simple cathode biased 5E3 (with cathodyne PI) then cloning a version of that may well be enough but if they did anything else out of the ordinary maybe it won't sound the same.

And that's where the joy of discovery and tweaking come it.

I wouldn't want to deny New Steve that experience!

[Zippy]

Well, it looks like he posted some schematics and a lot of info. Thanks, Tubeswell.

Please share what you find, Steve, regarding the differences.

[The New Steve H]

You are welcome to what I have, if I ever understand it. And provided Atmars doesn't drive down here and punch me in the face.