Marshall 2466 And New Genelex KT66's

[@timothyjay2012]

I just got this same type amp. It still had the Marshall branded Chinese tubes in it so I got 4 of the Gold Lion KT66's and 4 Long Plate Mullard 12AX7's. With setting my Bias at 41Ma I have one of the most versatile Marshall amps ive ever used!! I enjoyed the video and actually rewatched it before settling on the bias setting I did. With my bias at 38-39 ma the amp seemed Cold and sterile. By moving it up just a touch to 41 ma the thing came to life and will absolutely shack the pictures off the walls!! True story I was cranking it one evening while my wife was in the shower. She came in from our Living room and I stopped briefly for her to say you just broke 2 picture frames. Lmao im so proud of the ol girl!! Thanks for the video again I really enjoy them!! Please upload so more!! Tim

[@ElPasoTubeAmps]

I like JJ tubes also - every brand has their premium group from my experience - these tubes were provided by the client - in the basic phase splitter known also as the cathodyne circuit, balanced sections won't matter at all but in the balanced long-tail phase inverter it can make a significant difference. There are some nice articles on the Internet if you Google "cathodyne phase splitter" or "balanced long-tail inverter".

[@ElPasoTubeAmps]

I agree with the bias adjustment and the triode stages - the last 12AX7 had been, somewhere along the line, replaced with a 12AT7 - I am pretty sure this was the stage you are thinking about not operating in its linear range and then the new KT66's with a lowering of the bias did improve the notch distortion considerably - I can sometimes get full power at 5% but generally I have to drive the amps to 10% and with linear clipping top and bottom they seem to perform very well on stage.

[@mesa401]

Thank you so much for the reply. I will read up on it. I enjoy your videos.

[@onetime504]

Love the videos - they are like The Joy of Painting with Bob Ross, except for guitar players. Thanks!

[@ElPasoTubeAmps]

The driving level is similar between most all amps, -30 to -50 dB for the high gain inputs 0 dB to +10 dB for the Return input (driving just the power amp) - always watching the output signal. if you were to leave it overdriven into a square wave for long periods of time, I would suspect damage could occur but not for short test bursts -

[@guitarristagac]

Muy buen video!!

[@lousekoya1803]

Nice video !.......had my tech install some GL's yesterday and same thing ,....he said the effect loop was making the tubes clip because the value in the loop are too small ,.......does it make sense ?

[@moodyga40]

nice amp

[@jefflinkert6273]

What about going all the way and have the 12AX7 premium Gold Lions

[@ElPasoTubeAmps]

This amp came and went in my shop. I don't know anything of its whereabouts. I personally like the Gold Lion KT88's in my Mc275 but I have always stuck with the vintage small tubes (12AX7, etc) - in particular I like the Telefunken.

[@johnsimms3957]

What's the safest way to turn off a Marshall tube amp that has both a power and standby switch? Right now I turn the standby off, wait three minutes, and then turn off the power.

[@jameswellington4795]

You're doing it fine!

[@mitchellferre1652]

It would have been helpful to demo the amp. I am a player not a tech so I use my ears.

[@Nightingale1887]

Look at how good it sounds.

[@christopheraustin8827]

What are you using for a dummy load here? Any info appreciated! Cheers! -Chris Vancouver, BC

[@ElPasoTubeAmps]

I use precision 1% resistors made by Arcol and purchased from www.mouser.com There are a number of less expensive dummy loads available on Ebay. I use the precision resistors because I do a lot of measurements that I want accurate results from and the Arcol precision resistors do not change resistance when hot or cold. The cheap ones that look like aluminum blocks work OK just to dissipate power but they change from 8 ohms quite significantly when hot. I have a couple of other videos on dummy loads that you might enjoy.

[@christopheraustin8827]

Thanks for the swift reply! I *just* discovered your channel so I'll certainly be watching! I just got my first scope and signal generator so I'm super excited to learn. I have one of those alu-block style ones as that is all I could find locally. What rating are you using for a load here? 8ohm 100w? or?.... I mostly have 50w heads but would like to be able to handle 100w heads and possibly bass heads as well.

[@ElPasoTubeAmps]

The aluminum block loads are OK but you will find that as they get hot the resistance goes up. I use a pair of 300 watts 8 ohm loads mounted on the wall above my workbench. If you watch many of my videos you will see them. I upgraded them a few years back from 200 watts loads. I was working on big amplifiers and I once got the Arcol resistors up to 360 degrees ( I use an IR thermometer to measure a lot of things ) It was so hot it turned the labels on the heat sink black. But I checked and they were still 8 ohms :-) Best of luck and progress with your scope and signal generator. Be careful and work only with one hand around vacuum tube voltages. One hand at a time is important. I work with big amplifiers at 3000 and more volts and one mistake and I will be dead. Never lean on the work bench or the equipment while sticking a probe or meter lead into the amp. Learning the hard way is not likely to be deadly with 450 volts but it sure does hurt and may make you hurt yourself and knock your equipment onto the floor and ... whatever. Stay safe and post your discoveries on KZbin.

[@christopheraustin8827]

Thanks for the sound advice. Most of what you have said I am already aware of, but it never hurts to reiterate. I used to work in a guitar shop in my highschool days (I'm 30 now), and was taught the same method. At that time, all I ever did was retube and rebias using a bias probe, so now I'm looking to delve deeper. You're right! I should post my findings on KZbin. Once I get a few more under my belt I certainly will! Cheers! and thank you so so much!

[@mickeystanic4750]

Bias?

[@srprice2383]

Why are you calling it by it's code number? It's a Vintage Modern!

[@mesa401]

I like jj tubes. Is there really any reason to use a balanced tube in the phase inverter position?

[@basspig]

What I see here is an output stage biased too negative, raising the output impedance and causing the notch. In addition, an input stage is not operating on linear portion of its curve. The combination of the two is what you see on scope. BTW, 5 percent THD is Fender standard for power measurement. Ten is pissin in the wind.