Has Anyone Tried 6550's or KT88's in an Origin 20C

[Pistons&Petrol]

If not what's the blocker? I used to run KT88's in and 6550's in my 70's and 80's Marshall's back in the late 90's early 2k. I loved the sound of a wide open master volume Marshall with those bigger headroom tubes. I have a feeling I would love them in this thing.

Thoughts or does anyone have any references?

 

[DonP]

If not what's the blocker?

Burning down the house?

Some 70's and 80's Marshalls were designed to run 6550's. I've not see proof the Origin 20C is designed to.

 

[ampmadscientist]

If not what's the blocker? I used to run KT88's in and 6550's in my 70's and 80's Marshall's back in the late 90's early 2k. I loved the sound of a wide open master volume Marshall with those bigger headroom tubes. I have a feeling I would love them in this thing.

Thoughts or does anyone have any references?

Apparently this is a class A power amp which could theoretically run KT88, 6550, etc.
Measuring the plate current, or viewing the waveform using an O- scope is more ideal.
The cathode resistor is adjusted to optimize distortion VS heat...when re-designating output tubes it may be to your advantage to adjust.

 

[Pistons&Petrol]

Burning down the house?

Some 70's and 80's Marshalls were designed to run 6550's. I've not see proof the Origin 20C is designed to.

Strat's were never initially designed for humbuckers and Miata's weren't designed for V8's.

A properly done mod won't burn anything

 

[Pistons&Petrol]

Apparently this is a class A power amp which could theoretically run KT88, 6550, etc.
Measuring the plate current, or viewing the waveform using an O- scope is more ideal.
The cathode resistor is adjusted to optimize distortion VS heat...when re-designating output tubes it may be to your advantage to adjust.

I'm dropping it off with a guy known locally for Marshalls. I'll let him do the leg work if nobody's done it before. I'm not good enough myself to dig into an amp I've never worked on without "burning down the house"

Thanks for the input folks!

 

[Gene Ballzz]

I'm not sure the 6550s or KT88s will provide that same sort of "headroom" increase in a cathode bias situation and a mod to make the amp "fixed" bias would likely require an upgrade of transformer(s) and actually be turning the amp into a whole different animal. Even the possibly simple mods needed for using these tubes in cathode bias mode may increase the wattage/power enough to stress the output transformer. Marshall has not been recently noted for "overkill" in the robustness of their iron!

More Experienced Folks Will Know More Than Me!
Gene

 

[Filipe Soares]

excellent point... why modding? because we can!

 

[South Park]

You most likely will not get the same sound with those the kt88. The preamp and power supply have a major impact on tone .

 

[Filipe Soares]

I think 88s would be too big, but 77s would be a nicer fit. but in any of these cases you'll have to rewire the sockets.

Replacing EL34s for KT77s is easy, I've done it in my Engl Savage 60.

 

[neikeel]

Anyone got a schem for one of these yet?

 

[Gene Ballzz]

Anyone got a schem for one of these yet?

You, my friend are around here enough for me to assume you are making a "tongue in cheek" joke? The new normal for Marshall seems to be that schematics will not be available until "AFTER" an amp model has been discontinued! Now they may be available to authorized service shops, but few of the folks who operate/own such shops would be willing to jeapordize their authorization status just to appease us internet yahoos by sharing schematics! It's silly, but it is what it is!

Just My $.02,
Gene

 

[neikeel]

You, my friend are around here enough for me to assume you are making a "tongue in cheek" joke? The new normal for Marshall seems to be that schematics will not be available until "AFTER" an amp model has been discontinued! Now they may be available to authorized service shops, but few of the folks who operate/own such shops would be willing to jeapordize their authorization status just to appease us internet yahoos by sharing schematics! It's silly, but it is what it is!

Just My $.02,
Gene

 

[Pistons&Petrol]

excellent point... why modding? because we can!

Exactly!

You most likely will not get the same sound with those the kt88. The preamp and power supply have a major impact on tone .

For sure. Like I said in the first post, I've had modded a 1983 2203 that I ran EL34's, 6550's and finally KT88's in and 1976 JMP 2204 I switched back and forth between 6550's and EL34's regularly. That's just the point. To change the sound.

I think 88s would be too big, but 77s would be a nicer fit. but in any of these cases you'll have to rewire the sockets.

Replacing EL34s for KT77s is easy, I've done it in my Engl Savage 60.

I'm going to relocate the amp into a Mojotone Bluesbreaker 1x12 cab before anything else. Unless the tubes are too close to one another, I don't think fitment shouldn't be an issue. That said; I was thinking about WHY I want the KT88's last night and I was thinking that I probably don't need THAT much headroom in a tube for this amp. I think these two EL34's already have more headroom in this circuit than they do in a 50 watt circuit. If that is true, the KT77 would be the way to go.

Anyone got a schem for one of these yet?

You, my friend are around here enough for me to assume you are making a "tongue in cheek" joke? The new normal for Marshall seems to be that schematics will not be available until "AFTER" an amp model has been discontinued! Now they may be available to authorized service shops, but few of the folks who operate/own such shops would be willing to jeapordize their authorization status just to appease us internet yahoos by sharing schematics! It's silly, but it is what it is!

Just My $.02,
Gene

I really hope amp tech's have access to this.

 

[Filipe Soares]

I thought the 20c used EL84s...

I'll say to you that changing from 34s to 77s in my engl wasn't much of a change.

 

[Pistons&Petrol]

I thought the 20c used EL84s...

I'll say to you that changing from 34s to 77s in my engl wasn't much of a change.

The Origin 5c uses EL84's
The Origin 20c and 50c use EL34's

 

[Johnny 99]

After reading the thread where Santiago said you could basically use any octal tube in the 20h, I went ahead and threw a couple 6l6s in mine.

Long story short, it worked.

I didn't notice a huge difference, but I didn't really crank it and put it through all the places. I would like to put some kt66s or 5881s in at some point, but I get the feeling that the cathode biasing would negate some of the headroom differences between say an EL34 and a kt88. It should work though.

Of course, as always, ymmv.....

 

[DonP]

Strat's were never initially designed for humbuckers and Miata's weren't designed for V8's.

A properly done mod won't burn anything

A humbucker in a strat won't sound like a strat anymore.

A V8 in a Miata won't handle like a Miata.

An improperly done mod can burn down the house.

Good luck I hope you do your research.

 

[Pistons&Petrol]

A humbucker in a strat won't sound like a strat anymore.

A V8 in a Miata won't handle like a Miata.

An improperly done mod can burn down the house.

Good luck I hope you do your research.

You must have never driven a V8 Miata. They drive extremely well and still drive like a Miata. Still steer by foot. Just have it done properly.

A Strat with a Humbucker is still a Strat. It just sounds like a Strat with a Humbucker. Just don't use a garbage pickup.

... and that's why I have professional amp techs work on my amps.

 

[Filipe Soares]

You must have never driven a V8 Miata. They drive extremely well and still drive like a Miata. Still steer by foot. Just have it done properly.

A Strat with a Humbucker is still a Strat. It just sounds like a Strat with a Humbucker. Just don't use a garbage pickup.

... and that's why I have professional amp techs work on my amps.

indeed.

for those who want to see some swap porn:

 

[Pistons&Petrol]

indeed.

for those who want to see some swap porn:

YES!!!!

That's what I'm talking about. I have a project built engine/big turbo/standalone ECU Fiat 124 (Miata with a nose job) at the moment that's getting a bigger engine swap after this upcoming season is finished.

If you're bored, take a look:

https://youtube.com/c/pistonspetrol