Lee Jackson Metaltronix Amplifiers

[George]

It seems that my Stealth problems are far from over!
Even though the amp is supposed to have been fixed, a new dilemma makes its way upon the scene!
I purchased a cab for it: a Crate 1 x 12 GT112SL , with a Celestion G12K – 100 speaker, which is a 100 watt 8 OM . The Sound is fantastic!

The problem is, that after only ten minutes of playing, low or loud—the metal housing that the tubes or set into (the chassis) gets extremely hot! I feel that if I played it for twenty minutes, I would only be able to keep a finger on the metal for about five seconds or so.

I brought the head to the music store I fancy, and we put it through an old 8 OM bass cab with four ten inch speakers and played through it for about an hour, and it got only slightly warm. It also seemed to lack the seething—power and aggression of the cab I bought.

Now I have to bring my cab and head—and test it at the shop.
The fellow who runs the shop thinks that even though it is a correct cab and speaker match for the head, that the cab might be giving forth the wrong impedance and the speaker might need some sort of electronic something or other soldered in there somewhere.

Does anyone here know or have some idea about problems like this?
It’s ridiculous that even after the amp is fixed, and even after I found a speaker cab for it---I still cannot play it without possibly burning it up!

[George]

Sadly, the longest I've got to play the amp I adore more than all others, is about 5 hours before I had to have it fixed, and then it sat in storage until I had it fixed again.
Now I am using a speaker cable to connect the head to the cab, in case anyone might think that is the reason for the hotness.

I would greatly appreciate it if any Stealth fans could feel their amp chasis in the back after playing for about an half hour to an hour straight, and tell me how hot it is back there.
Please do not touch your tubes or have wet hands. Also, if you have to sneeze turn your head away from the tubes real fast, as nose droplets flying out of nostrils onto the hot tubes could break them!

I cannot just start playing loud for an hour or so with confidence if I have the remotest fear that I might be burning something up.

Is this amp supposed to run very hot back there?

[JimD]

George

I played my gt50 combo for about half and hour, pretty hard, the chassis didnt get as hot as you describe.

Cheers
Jim

[George]

Thanks for helping!

Looks like I will have to bring the amp in to check out using the new cab.
I've got a 1 x 15 in storage thats 8 oms, but its buried beneath a ton of other stuff---and weighs about 65--70 pounds!

I cannot understand how a cab that says 8-Oms on the back could have something that gives out anything other than 8-Oms, since its brand new, and came with the speaker in it. Although, the speaker does not have any Om designation labeled on it at. The fellow at the shop said that things can happen, and that it might be a 6-Om speaker.

When all this nonsense is resolved, I will have to make up for all the trouble it caused me by some real brooding Doom metal, then a little Death metal, and once the bother is out of my system---some 8o's stuff!

Even when the amp is set to a little under 2 for volume, and the preamp on 4 for the first gain channel (still don't have the foot switch yet) the sound is utterly fantastic!

I'll keep posting, to let everyone know about this new ordeal, and my progress concerning the eventual success in the matter.

[ClassX]

Edit ,,ooops sorry just looked up and seen you are talking about a head unit ,,, this info may not apply,,,,,,

George,,,If I recall correctly ,, the GT 50 stealth came out with a 16 ohm speaker built in the combo cabinet,,it was connected with a pigtail to the back of the chassis,, to one of the 2 output jacks,, on the jack plate below one output it says "Use First",,16 ohms.. below the other output jack says 16 ohms ,,8 ohms minimum
,,,

To me when it says 8ohm minimum,, any 8 ohm load should work,,,in either output jack,,,but on the other hand it was designed with a 16 ohm main speaker out,,, with the possible 16 ohm extension,,for a total load of 8hms ,,,

just a thought ,,, maybe try a 16ohm cab/speaker,,?


also,, is your amp is using 4 6v6 tubes in the output section,,,I know these tubes run at very high voltages,,,,

Keep on aRocking,,,,,,

[George]

Thanks again to everyone trying to help me!

The amp repairman retubed the amp for me. The four 6v6 tubes or correct. I really hope the shielded tubes are the correct kind!

I am wondering if Celestion puts out a 6Om version of that 100watt speaker in my cab as well as an 8 Om version?

The chap at the shop might be right! A mix up at the factory seems unlikely, but we cannot say it is impossible.

[ClassX]

George,,,I am not 100% positive that your unit does in fact use 6v6 tubes ,,,

I'm just know that my GT 50 combo does in fact use 4 6v6 tubes in the output section,,,and I'm willing to bet the Gt 50h head unit is the same amp just that it was put in a head cabinet,,,,,

I think I have 2 original 16 ohm crate special design 12 inch speakers that came with that unit in my storage shed,,, they were made by Eminence in the U.S.A.,,,my ol'lady got them cheap at a yard sale here,,,lol,,way before I went to work for SLM,,,anyhow I know one is in real good condition ,, the other is just ok,,,,,if you want one I will sell one or both super cheap plus shipping,,,,,

Keep on aRockin',,,,,

[George]

Hello ClassX!

It definately uses 6v6's--same as the combo.

I might indeed be interested in buying one or two of those, you can e mail me at sonofthestar@Gmail.com

I am most likely bringing it to the shop today to test it with the cab that has the 100 watt 8 OM speaker.

Over there, we plug it right into the wall, whereas I have been plugging it into one surge protector, plugged into another to get it positioned in the room where I want it. I wonder if that could be causing the problem?

[George]

I brought the amp in, and the cab.
We plugged it directly into the wall socket.
We cranked her up on the gain channel—preamp 10, gain ten! Volume set at a tad above 2.
Every one there had to come into that room to see the monster that must have been in there.
They looked quite surprised to see this diminutive package, barely two and an half feet tall.

We kept her on for about forty minutes---she got hot, but not as hot as she gets at my house (how could it be otherwise?). Every few minutes we would feel the chassis.
Three highly experienced fellows investigated, all said it was not an unusual amount of heat. One said it could be two times as much and he would not be concerned!
One fellow who played gigs thru his tube bass amp said his got three times as hot in three hours.
The fellow who never heard a Stealth played before, could not believe the quality of the sound!

We played a 100 watt Marshall tube amp to compare heat build up in the back.
The 50 watt Crate smoked it! The sound from the Crate made the Marshall sound like a solid state.
The fellow who owns the place could not believe the power, and said it was actually louder than many 100watt amps he's heard! And he meant tube amps!

They think that my using a flat square surge protector type thing built to sit beneath a PC monitor, might be causing the problem. Plug it in the wall they said.

So a little later that's what I will do, and play for about an hour.
The amp made a fool out of me, just like a sick child suddenly gets well in the doctor's office!
I will let everyone know how it works out.

I cannot even imagine what the 100 Watt version sounds like!

[ClassX]

George,, I'm so glad the amp got a passing grade at the shop,,, in more ways than one,,,,

It makes sense that the buffered power supply that sits below a PC might just be the culprit,,,as tube amps can average anywhere from 10 to 20 amps pull on a single circuit,,,and I'm willing to bet that power supply box was choking it out power wise,,,,,causing it to run hotter than normal,,,,

Ya,, I know that feeling all to well of the power of these little jewels,,, running the GT 50 through a Crate Celestion loaded 4x12 half stack is like "Wow",,, running through 2 4x12's is a brutul,,heavenly sound,,,the only other 50 watt amp that beats it is my Ampeg VL-502 ,, only because it has a more versatile clean channel,,,,,

Have fun,,,

Keep on aRockin',,,,,,

[George]

I take the amp home and plug it in the wall. Within ten minutes it gets as hot as usual!

So, at the shop, it gets only moderately hot, just a tad over warm in forty minutes time.
I figure, being that my room is only slightly warmer than the air-conditioned shop, (and even when I use the air conditioner the amp still got as hot) that perhaps air circulation was the problem.

I put a radio shack cooling fan about a foot from the back of the amp, blowing directly on the tubes, not using any air conditioning. I play for about twenty minutes and feel the back----no heat build up at all!
My conclusion so far, is that the EH 6V6 tubes burn very, very hot. Since heat travels up, the chassis was getting hotter and hotter. Now, with the fan blowing all the heat out through the front grill cloth from the back, the problem is solved.
Almost too simple to be true!

So my next question is, has anyone ever used EH 6V6 tubes and had the same problem, in any amp?
They sure make the amp sound better than the old Russian tubes that were in it when I found it at the pawnshop!
What kind of 6V6 tubes should I go with if these EH’s burn out sooner than usual because I did not even think to simply use a fan.

The chap at the shop said if the fan gets hot, I should put another fan behind it, and if that one gets hot, ----then just keep adding one after another until they circle the room a few times!

Once again, I am sorry to have burdened people with this problem of mine, but it might help someone else with the same problems.

[JimD]

I have Sovteks in mine, I will be replacing them with JJ's

Cheers
Jim

[BM]

I have the schematics ect if you want or need them,reply to me with your email address and I will send them mate

[George]

This is an update concerning my Stealth exploits.

The amp no longer gets hot to any great degree with the fan directed at the tubes!
It seems I can play somewhat loud for apartment living, for an hour or two, and at the end of the session, the chassis is just warm.

I did try putting a twelve band EQ through the effects loop, with the EQ master volume at its highest.
The amp started to intermittently play, with bad speaker sounds etc. Then it stopped playing completely!
I took the EQ out of the loop, and the amp recovered--and all is well again. I will not use the loop again.

I usually play with some kind of distortion pedal through the clean channel with the preamp set to about 8. The volume on the pedal is tuned in to 12 oclock or almost all the way dependant upon its strength. It seems that even though the speaker is that heaviest magnet crate 100 watt--it just cannot handle the volume produced when I turn the volume past 5. I cannot turn the volume down on the guitar, as this sucks the full gain away that I crave so much.

So I surmise, that even though this is a 50 watt amp, and even though the 12 inch speaker is that super Celestion 100watt---I will have to have a 4 X 12 to disperse the volume stress if I am going to play with the volume at about 8 or 9, and the Bass at about 8. The twelve would definitely be destroyed if I put the bass past 5 and cranked the volume past 5. I thought a 12 inch would be enough, and it is, for a modest loudness, but this amp must have a 4 x 12 or even two 4 x 12 cabs if one is to get the maximum potential out of it.
I will dig my heavy, heavy 15" speaker cab out of storage (which is 8oms) and use it in unison with the Crate 1x12. Using two 8om cabs and setting the impedance at 16 should do it. This way, great volume should be dispersed to relieve the stress on 1 X12 which it surely cannot handle!`

[JimD]

or you could buy a THD attenuator.

Cheers
Jim