Separate names with a comma.
Discussion in 'Marshall Amps' started by MarshallDog, Apr 27, 2018.
too cool! I'll be trying one out then.
It really delivered last night for my playing style!
I opened up the Origin 50 head today for the first time wanting to roll some tubes. I have been happily playing the amp in it's stock form up until now but I wanted to mix things up a bit to see what other tubes will bring to the table. For the life of me. though, I cannot finds the bias points for the power tube swap (I see the trim pot btw).
I am including images of the board. Can someone please point them out?
I am going to try some mallards and a pair of EHX 6CA7s in the power section and just roll though my collection of preamp tubes.
Also I am going to swap out the speakers in my 4x12 from 2xVintage 30s / 2x WGS ET65s to 4x G12K-85s to check out a different flavor.
These aren't cathode biased? I can't see a trim pot...it's early and my eyes are still not focussed
No Bias trim pots. Just swap the power tubes and play.
3rd pic top left. That's a trim pot. Don't know what its for but it's there
So just like the Origin 20, the Origin 50 needs no bias adjustment when swapping power tubes?
Ok. So I tried the Mullards... they sounded nice but smoothed everything out too much for me. I then put in the EHX 6CA7s and WOW what a difference. The thing fuckin' growls hard now.... no pedals in front of the amp. I haven't even done anything with the preamp tubes yet. Also, the combo of WGS ET65s and Celestion G12K-85s definitely add more tight bass response.
Its that little black pot in the lower picture. Its the one in the upper left corner next to the little black chip..
Wrong, the 50 needs to be biased.
I would like to know what resistor(s) is the choke resistor in this amp??? I would like to replace it with a real ClassicTone 3 Henry choke I have. Anyone have any idea???
Ok. That's what I thought I had heard. I will need to bias the tubes that I just put in. So I see the trim pot but where are the actual bias points to connect my multi-meter?
Not sure about that, I use the Weber BiasRite meter.
One trimmer for both tubes. That's cool. I prefer 2 trimmers so I don't need matched tubes but one works fine when matching.
Ok. I guess I will bias it old school like my 2204.
Using some recommendations from here, I installed the eminence swamp thing and also installed a Tung sol in V1 and V3 (paid a little extra from tubestore for higher gain/low microphonics for V1) and a Mullard in V2. The amp sounds even better now. “Fuller” with a little more bottom and tamed highs. Still dialing it in and breaking the speaker in, but I’m very pleased with it already!
Is the 50w head the same size as a Marshall 1987X or JTM45 RI?
I want to know if it will fit in a Marshall "Bluesbreaker" style combo cab.
That’s a good question. I have an empty 1987 Marshall Head shell. I will test it out and get back to you.
I just reached out to Marshall about the bias points. Marshall did not add the bias points but they did show me where the solder pads are. These can be used with your multimeter to bias your tubes. Look for CN32 on the board (See attached pic). They also recommended to bias to 65mV... take it or leave it.
You cant just set the bias at 65. Thats stupid. Every tube needs to be dialed in based on plate voltage.
And to add: most Marshall amps I've biased are more in the 30-40 range.