High Voltages After Headfirst Origin 50 Mod

Inspector #20

Inspector #20

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How difficult is this to do???



This guy stated the following, "The Origin 20 and the Origin 50 preamp circuitry are identical, right down to the resistor and capacitor numbers. The main difference is that the 20 is cathode biased EL34 and the 50 is fixed bias EL34. These mods will work in your Origin 50. Go for it!"
 
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I know this won't work on and Origin, but would something like this be better than the "Headfirst" mod???

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Legendary Tones - HOT MOD V2 EVO: The Ultimate Marshall High-Gain Plug-in Tube Modification Module!

Introducing the LegendaryTones HOT MOD V2 EVO, a plug-in dual tube module specifically engineered to dramatically increase gain in Marshall and other amps. The HOT MOD V2 EVO requires NO chassis cutting, drilled holes, or wiring modifications to your amp – it simply and easily installs in place...
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eSGEe said:
I see a mod coming soon..... this thread is basically @Robert Herndon TALKING HIMSELF into modding his Marshall.......

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I've been wanting to add a gain stage for a long time...but I'm not really comfortable with my skill level.

I'm thinking that maybe we get our amp guru's together in here, we can come up with something.
 
I know I'm a lone voice in the wilderness about this, but I could never understand this need to mod perfectly good amps. What is so wrong about Marshall's that has to be changed? I know it's a common (almost obsessive) thing, but I feel once you do that, it's not really a Marshall anymore.

Standing by for incoming. :bash:
 
Far Rider said:
I know I'm a lone voice in the wilderness about this, but I could never understand this need to mod perfectly good amps. What is so wrong about Marshall's that has to be changed? I know it's a common (almost obsessive) thing, but I feel once you do that, it's not really a Marshall anymore.

Standing by for incoming. :bash:
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There's a certain timbre and gain structure in the video that I've never been able to get with a stock amp.

Remember that George Lynch and Slash both used the now famous SIR #39 Marshall (modded by Tim Caswell with an extra gain stage) on their most iconic recordings.

That tone (with an extra gain stage) is basically a Marshall on steroids.
 
I found this post from a fellow who performed the Headfirst mod to an Origin 50H. In the text, he mentions differences between V1 and V2 PCB's:

Got a Marshall Origin 50 recently and I'm thinking about modding it. Thoughts?

"I did end up doing it. If you want more gain, especially at more reasonable volume, this will certainly do that. There are a couple things to keep in mind though.

tldr; Mod is great for gain, but in my experience not great if you want to keep the clean tone. This mod adds noise so shield the cabinet with foil or aluminum tape or something. There's a V2 of the board. If your board says V1 on the top left of the board under the Marshall logo, you're good to go. If yours says V2 then you might want to read on to the my text in bold below.

This doesn't seem to be a mod you want to use if you plan to retain a clean sound though. I find my clean tone to be lacking body and it sounds somewhat thin now, even without the bright cap installed. High gain sounds great which is fine with me since I bought this exclusively to use for gain.

The push-pull gain knob seems to do very little now so it functions basically as a normal gain knob as far as I can hear. Maybe someone with a more trained ear can hear a significant difference, but to me it sounds nearly identical on or off.

Also with the addition of a new gain stage and with none of the preamp tubes having shields the amp becomes pretty noisy. Lining the inside of the chassis with foil helped mitigate the noise significantly though (although the noise issue could have been a *me* problem since my room is pretty prone to electrical noise anyway, and my main guitar uses P90 pickups.)

Most importantly, there's now a V2 of the origin PCB. I'm not sure about the Origin 20 but the Origin 50 certainly has a V2. They are extremely similar but for the addition of a couple caps that I saw.

The one that interferes with the mod is marked C64 on the PCB I believe. It's just under C38 which is removed in the mod. What I did, and what seems to have worked well is remove C64 as well, then run a jumper across the two pads linking them and then I followed the instructions 1:1 the rest of the way through the mod.

Other than that there's another capacitor under the V1 socket. I left mine intact and didn't touch it since it didn't seem to impact anything to do with the mod. I'm not sure what it does though so maybe removing it would affect the sound in a positive way, I really can't say. I offered pictures to the creator of this mod but he didn't seem interested in looking for himself and he essentially told me to just post it in his FB group and someone in the community might offer advice.

I ended up not doing that since I was already done with the mod by the time he got back to me but someone else may have posted the V2 board in his group already. If you have V2 it might be worth a look..."
 
Robert Herndon said:
One comment that puzzles me. The Headfirst amp guy said the Origin 50H is fixed bias, but I can clearly see at least one bias pot:

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What they mean by "fixed bias" is that the amp runs class AB.
There is a negative voltage on the control grid of the output tube.
The negative voltage shuts the tube off, between guitar notes. It causes the tube to idle cooler.
Like a plexi or fender bassman, or DSL , etc....
The negative voltage is adjustable yes, but once adjusted the bias is "fixed" in one place.

The 20 watt is class A.
There is no negative voltage to control the bias.
The tube runs 90-100% at all times (it's turned on full at all times).
It has no idle like class AB does.
It's going to run hotter and use more tubes over time, compared to class AB.

In the old days, most amps were class A.
But over time the more efficient class AB amps dominated due to reliability and incresed tube life cooler operation.
 
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