Lee Jackson Metaltronix Amplifiers

[Carlos]

I recently needed to replace the tubes in my M-1000. Unfortunately half of the original tubes from when I received the amp were not labeled. So now figuring out which tubes to put in the amp can be discouraging to someone like myself who doesn't have a lot of knowledge about tubes and doesn't have enough money to buy them all for experimentation. With that said, please help me out.

1. Which tubes do you use in your Metaltronix M-1000? Preamp and Power?

I recent bought a quad Groove Tubes E34LS and Mullard 12ax7s and I am really displeased with their sound.

Thanks a lot!

[ClassX]

Carlos,,Welcome to the Lee Jackson amp forum,,,

Sorry to hear you are displeased with the sound of your amp ,,,To be honest I'm surprised that the amp does not part your hair with the best tone of any amp ,,with those tubes,,,

I have 2 questions for you,,,

1 Where did you get the tubes from,,?

2. Did a amp tech set the bias of the amp after the new tubes where installed,,,,,?

Keep on aRockin',,,,,

[Carlos]

Hey thanks!

1. I bought the tubes from zzounds.com.

2. I thought I didn't need to get the amp rebiased since the amp has a switch. So is the one of the problems? I need an amp tech to rebias it? Does this improve the sound?

Thanks!

[ClassX]

Carlos,,,Did you visual inspect all the Groove Tubes,,,,I know that Groove Tubes Rate all their output tubes on a scale from 1 to 10 ,,1-3 being fast to breakup ,, 4-7 middle of the road ,,,8-10 good strong clean output,,,

Edit,, it may be "vise versa",,,1-3 strong clean output,,,8-10 fast breakup,,,,anyway the Tubes should be marked 1-10 somewhere,,,,

With that being said ,, I also know that tubes that were supposed to be matched ,, that were not matched close enough,,,I have seen that happen quite often when using 4-6 output tubes in an amp,,,,"an Ampeg SVT bass amp uses 6 output tubes",,,,

Generally,,when an amp gets a fresh set of tubes it is best to have the bias checked,, as most likely the new tubes probably are not even close to the old tubes ,, unless they are an exact match,,,,

With the bias set to cold ,,the amp will sound flat,,brittle,,to hot,,,, it will sound great,, but the tubes will not last long,,,,,either way it should still be very loud,,,

There is a chance that the problem is one of the 12ax7 mullards pre-amp tubes,,,,,,You could try switching the 12ax7's around in different slots,,, just to see(hear) if there is a difference,,,,,or try some other 12ax7's you know are good,,,for testing,,,,

Does your amp have bias adjustment trim pots and red or green led lights on the back of the amp ,,,????

Edit,,,,I just read this in the M-1000 manual,,,,

Now, for the first time you can make your own decision about whether you like EL-34 tubes or 6550 tub
With a flick of a switch (located on top of the amplifier chassis by the output tubes) and a quick tube
change you can switch between EL-34’s and 6550’s anywhere! The amplifier bias is still adjustable
internally and should only be done by a qualified service technician. Bias voltages: EL-34 = -42 volts,
6550 = -50 volts. WARNING: INCORRECT BIAS SELECTION (i.e. 6550 tubes on EL-34 setting) IS
UNSAFE AND CAN CAUSE DAMAGE!


Keep on aRockin',,,,,
_________________
!!!ATTENTION!!!,,,I am not a amp tech,,I was an employee at the SLM electronics plant,,that made Ampeg and Crate products,,for the last 3 years before they moved operations to China,,,