High Voltages After Headfirst Origin 50 Mod

[Inspector #20]

@smitty_p - Let me add this...the gain and articulation at high gain settings, from the custom DiMarzio Neanderthal 16.5k AlNico9 44awg humbucker is almost impossible to describe.

No matter where I play YelloStrat, I get comments and questions.

It sounds more like a Les Paul than a Les Paul, but when I switch to the screw pole piece hum canceling single coils, it's pure Blackmore...

 

[Clockworkmike]

Good observations!!!

This is exactly why I'm going with a twin-amp setup. You can't beat my Marshall MG50 Solid State for its crystal clear clean tones. Maybe a Princeton is cleaner, but I have this 50 watt MG50 on hand, so it's a good choice for zero dollars spent.

The more I think about it, the more the clean/dirty amp setup makes more and more sense. No need to alter amp gain or volume or fiddle with rolling the knobs back between songs, just simply switch on 'A' or 'B' and you're ready instantly.

I'm wondering why I didn't do this sooner.

I used a similar setup years ago. First Marshall I had was a 4500 Dual Reverb, so channel switching was easy ( though you have a shared EQ and were pigeoned holed like a lot of split channel amps). But when i returned it a month later ( long story), i then bought a single channel 2500 SLX and lost that capability. You have two Master volumes thats footswitchable, but its really just a volume boost for soloing.

So we took a footswitch from another Marshall ( think it might have been a valvestate?), where it has two switches ( channel and reverb) with one input jack and modded the Reverb side into an A/B switch ( since there is no reverb on an SLX anyways). The Channel/boost switch remained the same

I would use a Peavey Envoy 110 40watt for cleans and could run an entirely different EQ section, mic it and it worked great honestly.

These days I use a DSL50 in just one setting but i have a Mode Four which is two separate amplifiers in one, so you can run two different EQ sections as well.

 

[smitty_p]

By the way, there's quite a volume drop when the Jose Diode Clipping switch is kicked in...

That makes perfect sense. The arrangement of the clipping diodes is nearly identical to how the Monte Allums Tri-Gain mod for the Boss DS-1 pedal worked. There were two sets of diodes. In the case of the Tri-Gain mod, you could select to use just the op-amp, a set of silicon diodes, or a set of germanium diodes. Just like you have a switch added to select the Jose Diode Clipping, in the Tri-Gain mod I had to add a small toggle switch to do the same sort of thing.

Anyway, I experienced the same thing. When selecting either of the diode sets I’d get a volume drop. That is because part of the waveform is being clipped off.

 

[smitty_p]

I used a similar setup years ago. First Marshall I had was a 4500 Dual Reverb, so channel switching was easy ( though you have a shared EQ and were pigeoned holed like a lot of split channel amps). But when i returned it a month later ( long story), i then bought a single channel 2500 SLX and lost that capability. You have two Master volumes thats footswitchable, but its really just a volume boost for soloing.

So we took a footswitch from a Dual Reverb, where it has two switches and modded the Reverb one, into an A/B switch ( since there is no reverb on an SLX anyways). The Channel/boost switch remained the same

I would use a Peavey Envoy 110 40watt for cleans and could run an entirely different EQ section, mic it and it worked great honestly.

These days I use a DSL50 in just one setting but i have a Mode Four which is two separate amplifiers in one, so you can run two different EQ sections as well.

A lot of the higher end two-channel amps have a separate EQ section for each channel. A lot of Mesa amps have separate EQ sections. The Rivera amp I am getting has separate EQs for each channel, as well. Shoot, even my Peavey Trans-Tube has separate EQs!

More and more, I get frustrated with Marshall. They have just enough on an amp to irritate me!

 

[Inspector #20]

A lot of the higher end two-channel amps have a separate EQ section for each channel. A lot of Mesa amps have separate EQ sections. The Rivera amp I am getting has separate EQs for each channel, as well. Shoot, even my Peavey Trans-Tube has separate EQs!

More and more, I get frustrated with Marshall. They have just enough on an amp to irritate me!

Best tone I think I ever got (back in the old days) was through my 230V English JTM30 using a DOD FX-50 and a DOD FX-90 using a custom step-up transformer.

The most frustrating thing about Marshall is not the lack of features, but how wimpy the gain production is. I run two EQ pedals, plus I "color" my tone with the tone knobs on the TS-9 and the CE-5.

 

[Amp Mad Scientist]

I am told that both of those functions (power scaling and boost) are basically bypassed or rendered ineffective by the modification due to the added gain stage.

No matter to me, because I always ran it on high power and Max boost all the time.

What's shocking is how nice the amp cleans up when the gain is rolled off...

On one hand I don't see the need for a boost switch.
I just set it on boost all the time and use the guitar volume to go from overdrive to clean.
I never saw the need for 2 volume controls.
There's those who don't need a bunch of gimmicks and foot switches.
I really don't have need for a bunch of effects either.

Diode clipping, I rather the tube overdrive with no diodes.
The sensitivity is much higher without the diodes and I get better sensitivity , harmonics and sustain which is what a lead guitar player really wanted anyway... .

The most recent clipping circuits use LEDs for the diodes.

 

[Clockworkmike]

A lot of the higher end two-channel amps have a separate EQ section for each channel. A lot of Mesa amps have separate EQ sections. The Rivera amp I am getting has separate EQs for each channel, as well. Shoot, even my Peavey Trans-Tube has separate EQs!

More and more, I get frustrated with Marshall. They have just enough on an amp to irritate me!

Yeah its aggravating that they keep to the single EQ on split channel/dual channel designs largely. The only valved ones i know of with 2 or more independent EQs are the JVMs, 6100, JTM60/JCM600 and JCM2000 TSL. The hybrids like the Valvestate, AVT and Mode Fours have it as well, but that is it as far as I know.

Anymore, that ought to be a standard design if you're going to make a 2 channel amp

 

[Inspector #20]

On one hand I don't see the need for a boost switch.
I just set it on boost all the time and use the guitar volume to go from overdrive to clean.
I never saw the need for 2 volume controls.
There's those who don't need a bunch of gimmicks and foot switches.
I really don't have need for a bunch of effects either.

Diode clipping, I rather the tube overdrive with no diodes.
The sensitivity is much higher without the diodes and I get better sensitivity , harmonics and sustain which is what a lead guitar player really wanted anyway... .

The most recent clipping circuits use LEDs for the diodes.

I learned many years ago that FX were an integral part of my tone, but each one makes only a subtle difference, until all are switched on.

This practice was reinforced when I heard Richie Faulkner say that his chorus pedal is on 100% of the time...

 

[Inspector #20]

On one hand I don't see the need for a boost switch.
I just set it on boost all the time and use the guitar volume to go from overdrive to clean.
I never saw the need for 2 volume controls.
There's those who don't need a bunch of gimmicks and foot switches.
I really don't have need for a bunch of effects either.

Diode clipping, I rather the tube overdrive with no diodes.
The sensitivity is much higher without the diodes and I get better sensitivity , harmonics and sustain which is what a lead guitar player really wanted anyway... .

The most recent clipping circuits use LEDs for the diodes.

I learned many years ago that FX were an integral part of my tone, but each one makes only a subtle difference, until all are switched on.

This practice was reinforced when I heard Richie Faulkner say that his chorus pedal is on 100% of the time...

 

[Clockworkmike]

Best tone I think I ever got (back in the old days) was through my 230V English JTM30 using a DOD FX-50 and a DOD FX-90 using a custom step-up transformer.

The most frustrating thing about Marshall is not the lack of features, but how wimpy the gain production is. I run two EQ pedals, plus I "color" my tone with the tone knobs on the TS-9 and the CE-5.

Marshall makes a few valve "hi gain" amps like the JCM900s, JCM2000s, DSLs, 6100. But compared to others using that title, they can be restrained in comparison.

The JVM and JCM800KK are their highest gain models, in which some call it " ultra high gain"

 

[smitty_p]

More and more, I get frustrated with Marshall. They have just enough on an amp to irritate me!

The most frustrating thing about Marshall is not the lack of features…

What I mean is that sometimes they have a feature set that is insufficient for the amp, as a whole. For example, they’ll have a two channel amp, but have a shared EQ section. Now, other times, they’ll be fine…like they’ll have a good, single-channel, non-master volume amp that roars! In that setting, the feature set is appropriate to the model.

 

[smitty_p]

Yeah its aggravating that they keep to the single EQ on split channel/dual channel designs largely. The only valved ones i know of with 2 or more independent EQs are the JVMs, 6100, JTM60/JCM600 and JCM2000 TSL. The hybrids like the Valvestate, AVT and Mode Fours have it as well, but that is it as far as I know.

Anymore, that ought to be a standard design if you're going to make a 2 channel amp

Totally agree.

 

[Inspector #20]

What I mean is that sometimes they have a feature set that is insufficient for the amp, as a whole. For example, they’ll have a two channel amp, but have a shared EQ section. Now, other times, they’ll be fine…like they’ll have a good, single-channel, non-master volume amp that roars! In that setting, the feature set is appropriate to the model.

Understandable. I guess I have just never put that much thought into it?

 

[syscokid]

So, just to be clear, does this mod actually change the gain structure of the amp, or is the apparent gain increase really a result of the added diode clipping?

Even without activating the diode clipping mod, the amp now has a buttload of added gain. V1 was massaged a little at its cathodes. But the reconfiguring of V2 definitely gets the party going as Robert described.

 

[Inspector #20]

I used a similar setup years ago. First Marshall I had was a 4500 Dual Reverb, so channel switching was easy ( though you have a shared EQ and were pigeoned holed like a lot of split channel amps). But when i returned it a month later ( long story), i then bought a single channel 2500 SLX and lost that capability. You have two Master volumes thats footswitchable, but its really just a volume boost for soloing.

So we took a footswitch from another Marshall ( think it might have been a valvestate?), where it has two switches ( channel and reverb) with one input jack and modded the Reverb side into an A/B switch ( since there is no reverb on an SLX anyways). The Channel/boost switch remained the same

I would use a Peavey Envoy 110 40watt for cleans and could run an entirely different EQ section, mic it and it worked great honestly.

These days I use a DSL50 in just one setting but i have a Mode Four which is two separate amplifiers in one, so you can run two different EQ sections as well.

That sounds awesome!!!!

 

[ivan H]

Even without activating the diode clipping mod, the amp now has a buttload of added gain. V1 was massaged a little at its cathodes. But the reconfiguring of V2 definitely gets the party going as Robert described.

I had to go back & find the pre & post mod pre-amp schematics to be sure, but in following the Jose V1a/V1b theme, the amp is actually developing "less" gain from the first two triodes than it would have if he (Jason Tong) had left the cathode R/C combinations as they were.
V1a previously had 1k5/1uf, he's biased the tube cooler & with less gain in the low end by using 2k7/0.68uf (though IIRC @syscokid used 2k7/1uf).
V2b previously was biased quite warm, with an 820 ohm cathode resistor. This was "partially" bypassed by a 0.68uf capacitor in series with a 47k resistor. Engaging the "boost" function bridges (or "shorts") the 47k resistor, which "fully" bypasses the cathode resistor with the 0.68uf cap, thus producing the gain boost. Again he's followed the Jose theme of using a 2k7 cathode resistor which biases the tube a good bit cooler. This right there is why engaging the boost now has so little effect. To make the boost function more effective, increase the value of that 47k that is in series with the 0.68uf capacitor (try say, 3 ~ 5 times its current value, 150k ~ 250k).
Doing away with the previously plate driven tone stack on the output of V1b makes for a stronger signal coming out of this stage.
The gain increase comes from doing away with the losses inherent to a plate driven tone stack, & then, most definitely yes, from converting the following triode to a gain stage with 1k/22uf cathode arrangement (runs full design gain across the whole frequency range). This 3rd stage is also where a good amount of overdrive is happening.
The DC coupled cathode follower provides slightly less than unity gain, but avoids loss in the tone stack (the cathode follower is a low impedance source).
Cheers

 

[syscokid]

To make the boost function more effective, increase the value of that 47k that is in series with the 0.68uf capacitor (try say, 3 ~ 5 times its current value, 150k ~ 250k).

I should try this while I still have the amp!

 

[ivan H]

I should try this while I still have the amp!

Yes. First verify that the resistor value IS 47k. That is what it "appears" to be on the hand drawn schematic.
Be aware that with the boost feature NOT engaged this will knock the gain down some, but this will return to the normal amount that it has now once the boost IS engaged.
Just experiment to find a value that gives reasonable gain reduction. Cheers

 

[Inspector #20]

Wow, I wish I knew more about these things!!@@!!

What advantages (if any) would we see with this mod???

 

[syscokid]

What advantages (if any) would we see with this mod???

World Peace...