RT2/50 mods..

Ok here's an ambitious idea: let's see if we can cook up any mods for the RT2/50 poweramp!

Idea's:
- Upgrading / modding the prescence+density caps
- Half power switch (don't know if this is possible at all, does this need a different tranny?)
- Tube rectifier (on one channel .. or switchable for the most flexible poweramp in the world!)
- "Bridged" mode to 100 watts mono

Except for the first these are pretty crazy idea's, but I thought I'd throw it out there as some might be easier than I thought

Who here can enlighten me?

Ambitious sir! Here is my super "off the top of my head" quick replies:

Idea's:
- Upgrading / modding the prescence+density caps
- Half power switch (don't know if this is possible at all, does this need a different tranny?)
- Tube rectifier (on one channel .. or switchable for the most flexible poweramp in the world!)
- "Bridged" mode to 100 watts mono

Click to expand...

In order:

1: Quite possible and I would gladly work on this after I get some work/R&D and other stuff out of the way.

2: My initial thought is no. Particularly because each side only has 2 tubes, so you can't turn a pair off. There is the Pentode/Triode approach, but that's more like 2/3 power and it will impact tone significantly. For the hassle, the decrease in wattage wouldn't really be worth it to me. I should also point out these amps are among the best at low volume playing that I own.

3: There is seriously no room inside to make this happen. It's PAINFULLY tight in there.

4: If I recall (not in front of an open amp right now), each side has it's own tranny and runs independent of the other. Do not quote me though. So this is probably not likely either.

Thanks for your reply!

1: Great, that is probably the only one I could do myself

2: I figured that would be the case. I agree that these amps sound great at lower volume. That said: at half power it should sound even better or good at still lower levels.

3: Good point, I've been in there for the fan. Maybe you could squeeze it in with a lot of trouble, but then you'd probably get noise issues. I think we can forget about this one
Another idea: do different types of solid state rectifiers sound different? (like FET and Si transistors, it might not be tube but still a usefull difference?)

4: Yep, each side does have it's own transformer. This is why it's so cramped on the inside and **** heavy!
I must say I have no knowledge about the poweramp side of amps, so I might say some stupid things here: couldn't you just connect the outputs of the transformers in parallel? Basically reversing a multiple-cab idea? (I'd guess you'd have to double your cab ohmage then).

Again, maybe that's stupidity but it's worth asking.

I have a set of detailed gutshots of the RT2/50. I'll post them later.

Loving the Tube Rectifier question and I do believe it's possible to emulate power tube sag, however it would involve switching the Negative Feedback loop OUT. Therefore, switching the Density and Presence controls out of the signal path to achieve a more chewy, looser feel.

What are the possibilities of throwing a switch in for that, Rob?

On the topic of SS rectifiers, I know nothing about how they work. Though an idea arises from a friend's modding of a TS808 clone (please feel free to let me know if I'm full of it here ).
I know symmetrical diode clipping will be harsh, but asymmetrical diode clipping tends to have more life and tube-like character to it... Could a similar concept be applied to the SS Rectifier? Or are we talking about two totally different things?

Does anyone have a RT 2/50 schematic? I don't have one and it would make thinking through this stuff way easier.

Jaded Faith said:

Does anyone have a RT 2/50 schematic? I don't have one and it would make thinking through this stuff way easier.

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I emailed you the schematics and gutshots I have.

If anyone else wants them, PM me with your e-mail!

m0jo said:

Jaded Faith said:

Does anyone have a RT 2/50 schematic? I don't have one and it would make thinking through this stuff way easier.

Click to expand...

I emailed you the schematics and gutshots I have.

If anyone else wants them, PM me with your e-mail!

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Everyone who PM'ed has mail!

Here's a gallery with the gutshots I made:
https://www.dropbox.com/gallery/7181889/1/RT250%20pics?h=2eb58a#/
They are kinda random, but it might help.

Mercury Magnetics are more than willing to manufacture input and output transformers for the RT2/50. All its gonna take is one guinea pig to tear out their desired trannies and send them to MM for R&D then manufacturing. Something I was gonna do, but bought a fryette power amp instead.

1. of course

2. You can ground one of the input grids on one tube in a pair, which would make it sound like an SE amp. Peavey did this with a pot and called it a texture control

3. you can add tube recto sag by putting in a big resistor in the power supply to restrict current flow.

4. the amp already does bridged mode.

nomad100 said:

1. of course

2. You can ground one of the input grids on one tube in a pair, which would make it sound like an SE amp. Peavey did this with a pot and called it a texture control

3. you can add tube recto sag by putting in a big resistor in the power supply to restrict current flow.

4. the amp already does bridged mode.

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Thanks for the clear response

But does 2 not make the tubes wear differently, disturbing the matching?
Again, I'm not very knowledgable on these things yet, learning

The amp does not have a bridged mode.
There are two options: stereo and switching. In stereo both channels are completely seperated (as you can see in the gutshots there are 2 output trannies).
In switching mode you choose which channel to use, using one cab or a cab per channel (muting the other cab).
There's also an option to mute the poweramp, handy to eliminate any sounds completely when tuning or whatever.

i read the manual wrong sorry i'm not sure about the tube wear.

nomad100 said:

i read the manual wrong sorry i'm not sure about the tube wear.

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I don't blame you, the manual isn't exactly clear on a lot of things

Does anyone else have an idea about that push-pull to single-ended mod??
That would be exactly what I'd like, a simple mod with very usable results.
(you could do this per channel .. creating even more wide possibilities!)

m0jo said:

nomad100 said:

i read the manual wrong sorry i'm not sure about the tube wear.

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I don't blame you, the manual isn't exactly clear on a lot of things

Does anyone else have an idea about that push-pull to single-ended mod??
That would be exactly what I'd like, a simple mod with very usable results.
(you could do this per channel .. creating even more wide possibilities!)

Click to expand...

I've done some research and the mod seems easy enough to do. A simple piggyback type mod without having to ruin anything (if I'm reading the valveking schems correctly).
The question is wether it would really have much merit. The opinions are divided over wether it's a usable option or just a gimmick..

I have a 5W SE amp, and a lot more responsive than a PP amp. Any amp i would build myself would have the switch.

nomad100 said:

I have a 5W SE amp, and a lot more responsive than a PP amp. Any amp i would build myself would have the switch.

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Yes but this is not true SE, it's only "like" it.
So that's why I wondered, how much like it.

It is true class A SE just not traditional SE. You would get better frequency response with less weight not having to use a big air gaped transformer. The second tube just working as a dummy balancing the dc I believe. I'm not sure how to describe the difference in tone. I would say it's much more alive. My little amp has a very simple 2 stage preamp. The power amp distorts first then the pre from back to front.

nomad100 said:

It is true class A SE just not traditional SE. You would get better frequency response with less weight not having to use a big air gaped transformer. The second tube just working as a dummy balancing the dc I believe. I'm not sure how to describe the difference in tone. I would say it's much more alive. My little amp has a very simple 2 stage preamp. The power amp distorts first then the pre from back to front.

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Hm ok, seems worth a shot!

I have a Marshal 8008 power amp..its an older 90s power amp, supposedly a design that uses tubes but also SS parts...is that what you gusy are talking about??
Min is lightweigher (well LIGHTER) and it is smaller, and it sound tube-like..
but I still like my Rt2/50 better even though I curse the weight!

GtrGeorge
what does SE stand for? I admit I am not knowledgeable in these areas.

GtrGeorge! said:

I have a Marshal 8008 power amp..its an older 90s power amp, supposedly a design that uses tubes but also SS parts...is that what you gusy are talking about??
Min is lightweigher (well LIGHTER) and it is smaller, and it sound tube-like..
but I still like my Rt2/50 better even though I curse the weight!

GtrGeorge
what does SE stand for? I admit I am not knowledgeable in these areas.

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SE = Single Ended, as opposed to Push-pull.

If I say it right, push pull means one tube will work one phase of the signal, while the other tube in the pair does the other phase, so basically pushing and pulling the signal.
Single ended is where the signal is only being pushed one side, so you can use one tube for this (whereas push-pull requires 2 tubes to accomodate the 2 functions).

Am I getting this right guys?

ok..
Im still not sure what SE sounds like...versus other options.
GtrGeorge