Question on SLO 5 stage mod?!?!?

[VaporDemon]

Just curious if anyone has ever used the 2nd (Crunch/Clean) half of V1 on an SLO circuit to do a 5 gain stage mod? Obviously would need to change Biasing and Filtering and so on for all the stages but I’m pretty determined to make this happen. I’m thinking of keeping the stock CF/Tone stack unless a plate fed TS would suit it better, and also implementing some other changes.

Any suggestions on voltages, and where I should look at cathode bypass or cold clipper locations? What are some suggestions on what to avoid or focus on?

My other thoughts are is it possible to run multiple cold clippers on two stages at different bias points or will that just make it a mess?

Thanks in advance!

 

[glpg80]

Everyone I know that’s gone 5 stage regrets it and redesigns a 4 stage to keep compression manageable and tracking for metal tight enough. Too many stages and you’ll get an unstable sluggish mess unless your plan is to dump a ton of wasted power which also doesn’t make a lot of sense.

The SLO is iconic for a reason. I suggest not playing the 5 stage internet hype game on one and messing with a reissue Marshall or kit build to do your blind testing.

 

[VaporDemon]

Hey thanks for your suggestion! This amp isn’t a real SLO but a Jet City modded to SLO spec and I’m trying to get something more unique out of it. I’m still in the process of trying out ideas to discover new tones as I continue learning amp modding. Honestly you’re not the first person to tell me about people trying it and then going a different route. I love the sound of an SLO but I’m trying to get something capable of getting tighter that sounds and feels more like it’s got a drive pedal up front. I people usually love boosts or hate them and I don’t always use it but sometimes it’s needed for some of what I love to play. I’m not dead set on a five stage so I may not end up doing it. There is a clip on YouTube of the Ground Zero modded Triple Rec Rev G without a boost and that’s a great example of the type of thing I’m shooting for. The clip is a short one with a guy playing through it with a Les Paul.

That said, I wasn’t even sure this would get me that sound but I’m just trying things. I have a different JCA I’ve modded and thats a 4 stage OD channel that’s almost like a tighter hyper gained up version of an SLO mixed with hot rodded Marshall DNA but it doesn’t do the angry recto thing quite as I’d like. Anyway sorry to ramble and thanks again for your reply.

 

[TotallyRadGuitars]

I say go for it man, sounds like a great idea. I don't think "number of gain stages" necessarily means an amp won't be tight enough for metal, even if that's the case in some situations. EVH 5150's have 6 gain stages + CF for example and while definitely compressed, I don't think anyone would say that they are too loose for metal lol.

I modded a whole bunch of values on my JCA22. I had 3-way switches for various values, some were SLO values, others wildly the other direction so I could experiment. First amp I ever modded and it was an amazing experience for me. It was the 1x12 combo so I sold it (I wanted a head) and the new owner also loved it. I never did any gain stage reorganizing at the time but it would be fun to try it now.

Long story short I have no idea where to start but I'd love to see it as the project progresses because I love the idea. Never tried two cold clippers, but I think it's notable that the SLO, Bogner Ecstasy red channel, and EVH 5150 red channels all have their cold clipper on the 3rd gain stage, while the JCM800 2203 has its cold clipper on stage 2 (out of only 3, makes sense I guess?). Something I personally have always wondered was how it would sound if the cold clipper on the SLO was on the 2nd stage instead of 3rd, I'd expect it to have a more prominent effect on the sound (for better or worse, may have to lower the value of it since the stock SLO value is super high compared to the 2203's 10k)

 

[Chubbs]

The 5 stage stuff I’ve tried all sucks, 3-4 is the sweet spot. Definitely try it but I think with an slo type circuit it’s gonna be way too much gain in all the wrong places.
I would however recommend playing around with different values or cut out the cathode follower and do a 4 stage plate fed. That’s what I did with my jca20 and it has gobs of gain. Jet city boards are stupid easy to pull.

 

[VaporDemon]

The 5 stage stuff I’ve tried all sucks, 3-4 is the sweet spot. Definitely try it but I think with an slo type circuit it’s gonna be way too much gain in all the wrong places.
I would however recommend playing around with different values or cut out the cathode follower and do a 4 stage plate fed. That’s what I did with my jca20 and it has gobs of gain. Jet city boards are stupid easy to pull.

The 5 stage stuff I’ve tried all sucks, 3-4 is the sweet spot. Definitely try it but I think with an slo type circuit it’s gonna be way too much gain in all the wrong places.
I would however recommend playing around with different values or cut out the cathode follower and do a 4 stage plate fed. That’s what I did with my jca20 and it has gobs of gain. Jet city boards are stupid easy to pull.

Hey thanks for the input! Yeah I wasn’t leaving everything else as is, I was going to reconfigure the other stages accordingly. I guess I’m just using what’s there and making totally different from an slo so not really an slo 5 stage. Yeah I agree the Jet city boards are super easy to pull. This is my 2nd one and I genuinely enjoy modding them!

 

[VaporDemon]

I say go for it man, sounds like a great idea. I don't think "number of gain stages" necessarily means an amp won't be tight enough for metal, even if that's the case in some situations. EVH 5150's have 6 gain stages + CF for example and while definitely compressed, I don't think anyone would say that they are too loose for metal lol.

I modded a whole bunch of values on my JCA22. I had 3-way switches for various values, some were SLO values, others wildly the other direction so I could experiment. First amp I ever modded and it was an amazing experience for me. It was the 1x12 combo so I sold it (I wanted a head) and the new owner also loved it. I never did any gain stage reorganizing at the time but it would be fun to try it now.

Long story short I have no idea where to start but I'd love to see it as the project progresses because I love the idea. Never tried two cold clippers, but I think it's notable that the SLO, Bogner Ecstasy red channel, and EVH 5150 red channels all have their cold clipper on the 3rd gain stage, while the JCM800 2203 has its cold clipper on stage 2 (out of only 3, makes sense I guess?). Something I personally have always wondered was how it would sound if the cold clipper on the SLO was on the 2nd stage instead of 3rd, I'd expect it to have a more prominent effect on the sound (for better or worse, may have to lower the value of it since the stock SLO value is super high compared to the 2203's 10k)

Awesome reply, thanks! Definitely going to mess with it but I’m going in with a game plan before I start it.

I say go for it man, sounds like a great idea. I don't think "number of gain stages" necessarily means an amp won't be tight enough for metal, even if that's the case in some situations. EVH 5150's have 6 gain stages + CF for example and while definitely compressed, I don't think anyone would say that they are too loose for metal lol.

I modded a whole bunch of values on my JCA22. I had 3-way switches for various values, some were SLO values, others wildly the other direction so I could experiment. First amp I ever modded and it was an amazing experience for me. It was the 1x12 combo so I sold it (I wanted a head) and the new owner also loved it. I never did any gain stage reorganizing at the time but it would be fun to try it now.

Long story short I have no idea where to start but I'd love to see it as the project progresses because I love the idea. Never tried two cold clippers, but I think it's notable that the SLO, Bogner Ecstasy red channel, and EVH 5150 red channels all have their cold clipper on the 3rd gain stage, while the JCM800 2203 has its cold clipper on stage 2 (out of only 3, makes sense I guess?). Something I personally have always wondered was how it would sound if the cold clipper on the SLO was on the 2nd stage instead of 3rd, I'd expect it to have a more prominent effect on the sound (for better or worse, may have to lower the value of it since the stock SLO value is super high compared to the 2203's 10k)

 

[VaporDemon]

Awesome reply, thanks! Definitely going to mess with it but I’m going in with a game plan before I start it.

I’ll definitely be experimenting with the cold clipper values and locations, worse comes to worse I’ll just change it if it doesn’t work.

 

[VaporDemon]

I say go for it man, sounds like a great idea. I don't think "number of gain stages" necessarily means an amp won't be tight enough for metal, even if that's the case in some situations. EVH 5150's have 6 gain stages + CF for example and while definitely compressed, I don't think anyone would say that they are too loose for metal lol.

I modded a whole bunch of values on my JCA22. I had 3-way switches for various values, some were SLO values, others wildly the other direction so I could experiment. First amp I ever modded and it was an amazing experience for me. It was the 1x12 combo so I sold it (I wanted a head) and the new owner also loved it. I never did any gain stage reorganizing at the time but it would be fun to try it now.

Long story short I have no idea where to start but I'd love to see it as the project progresses because I love the idea. Never tried two cold clippers, but I think it's notable that the SLO, Bogner Ecstasy red channel, and EVH 5150 red channels all have their cold clipper on the 3rd gain stage, while the JCM800 2203 has its cold clipper on stage 2 (out of only 3, makes sense I guess?). Something I personally have always wondered was how it would sound if the cold clipper on the SLO was on the 2nd stage instead of 3rd, I'd expect it to have a more prominent effect on the sound (for better or worse, may have to lower the value of it since the stock SLO value is super high compared to the 2203's 10k)

To follow up I noticed that the EVH 5153 red channel has a much lower cold clipper value. The SLO and similar amps use 39K and the EVH 5153 Red is like 18K which makes sense. After looking at the schematic for the EVH I notice it’s actually like you said, 6 stages and the cathode follower feeding the tone stack. I’m not sure I want to do a 6 stage but since I’m eliminating the tube fx loop and repurposing v3 for gain stages I have the option for 6. My other thought was leaving the amp as a 4 stage and using a fet boost on the front end and just tweaking the filtering and stages to tighten it up. The slo is actually in the realm of what I like but it still needs a boost to get it in the modern high gain territory I prefer in my opinion.

 

[RedPlated]

Adding a stage to that amp is going to be a long and drawn out process of dropping a lot of signal in multiple stages, creating voltage dividers, changing pot values, controlling frequencies, adding/ increasing filtering etc…. Much trial and error and potentially long nights with alligator clips. Of course anything can be done if you’re willing to invest the time in it.

Plate driven tone stacks are pretty wild to tame. I just finished a 4 stage plate fed design on a 70’s 50 watt Marshall. It’s very complex to get the response and feel correct on them. CF designs are much easier to get dialed in, in my experience.

I’d personally just tune the 4 stages. Plenty of tight gain available that way.

 

[glpg80]

Im not a fan of plate driven stacks at all. You get a quack response from them due to the previous stages output impedance being nonlinear across all frequencies a TMB tonestack typically targets. The benefit of them is that they’re more raw and aggressive. Like Jeremy said it’s a balancing act. Personally they drive me nuts.

 

[TotallyRadGuitars]

To follow up I noticed that the EVH 5153 red channel has a much lower cold clipper value. The SLO and similar amps use 39K and the EVH 5153 Red is like 18K which makes sense. After looking at the schematic for the EVH I notice it’s actually like you said, 6 stages and the cathode follower feeding the tone stack. I’m not sure I want to do a 6 stage but since I’m eliminating the tube fx loop and repurposing v3 for gain stages I have the option for 6. My other thought was leaving the amp as a 4 stage and using a fet boost on the front end and just tweaking the filtering and stages to tighten it up. The slo is actually in the realm of what I like but it still needs a boost to get it in the modern high gain territory I prefer in my opinion.

I mainly mentioned that the EVH had 6 stages because people consider it to be a generally good sounding amp capable of tight metal tones. I never liked the common assumption that "fewer gain stages = tighter" but I'm also not an amp designer, just a hobbyist, so idk, it's probably true in some technical sense.

I picked up an Avenger not long ago that has 3 holes and a tube socket drilled right near the input jack. It's since been restored to stock but I have to wonder if the previous owner had the same idea that you did, but I think they way they probably did it was by making a simple 12ax7 overdrive with volume/tone/gain knobs and just hard wired it right into the input. It's actually a rare time when I wish it were still present, I mean I wanted a stock Avenger but now I'm just wondering what they had in mind for a mod. Or hey, maybe the mod never worked/sounded good and that's why it got restored to stock before they sold it.

Anyway that reason I mention that is the FET boost idea, I drew up plans for mods for my Jet City JCA22 a decade ago and my idea was essentially to buy another Ibanez TS7 (I'd just gotten one for $19 at the time) and pull the guts right out of the pedal, wire it to be always on, and drill 3 holes for the pots into the panel of the amp. My thought process was that I like the sound of a boosted JCA/Marshall, so why mod the circuit, just hard wire the boost into the amp - simpler and easier. Basically, what Driftwood ended up doing in a much more polished/professional way. So sticking a hard-wired boost "gain stage" right after the input and before the first tube gain stage would be relatively low effort and would probably sound great tbh.

.... making me want to revisit my JCA mod on my Avenger now. I'd never modify an amp this nice but since it has 3 holes drilled in it anyway...

 

[VaporDemon]

I mainly mentioned that the EVH had 6 stages because people consider it to be a generally good sounding amp capable of tight metal tones. I never liked the common assumption that "fewer gain stages = tighter" but I'm also not an amp designer, just a hobbyist, so idk, it's probably true in some technical sense.

I picked up an Avenger not long ago that has 3 holes and a tube socket drilled right near the input jack. It's since been restored to stock but I have to wonder if the previous owner had the same idea that you did, but I think they way they probably did it was by making a simple 12ax7 overdrive with volume/tone/gain knobs and just hard wired it right into the input. It's actually a rare time when I wish it were still present, I mean I wanted a stock Avenger but now I'm just wondering what they had in mind for a mod. Or hey, maybe the mod never worked/sounded good and that's why it got restored to stock before they sold it.

Anyway that reason I mention that is the FET boost idea, I drew up plans for mods for my Jet City JCA22 a decade ago and my idea was essentially to buy another Ibanez TS7 (I'd just gotten one for $19 at the time) and pull the guts right out of the pedal, wire it to be always on, and drill 3 holes for the pots into the panel of the amp. My thought process was that I like the sound of a boosted JCA/Marshall, so why mod the circuit, just hard wire the boost into the amp - simpler and easier. Basically, what Driftwood ended up doing in a much more polished/professional way. So sticking a hard-wired boost "gain stage" right after the input and before the first tube gain stage would be relatively low effort and would probably sound great tbh.

.... making me want to revisit my JCA mod on my Avenger now. I'd never modify an amp this nice but since it has 3 holes drilled in it anyway...

Yeah man I’ve kind of wondered about an OD boost built in on amps and then amp companies started coming out with built in boosts like the Driftwood or the invective and I’m pretty sure there are 1 or 2 others that I can’t think of right now. For the FET boost I’m probably grabbing one of the headfirst boards and try different cap values to get the low end where I’d like it. I’m probably implementing the FET boost on my JCA 50 and leave it at 4 stages and save the 5 stage for my 100 which is my long term project. Good luck with the avenger! I’d love to hear it if you go through with it

 

[VaporDemon]

Adding a stage to that amp is going to be a long and drawn out process of dropping a lot of signal in multiple stages, creating voltage dividers, changing pot values, controlling frequencies, adding/ increasing filtering etc…. Much trial and error and potentially long nights with alligator clips. Of course anything can be done if you’re willing to invest the time in it.

Plate driven tone stacks are pretty wild to tame. I just finished a 4 stage plate fed design on a 70’s 50 watt Marshall. It’s very complex to get the response and feel correct on them. CF designs are much easier to get dialed in, in my experience.

I’d personally just tune the 4 stages. Plenty of tight gain available that way.

I kind of figured it would be a complicated process, Jason Tong mentioned it being a delicate balancing act if I remember his wording correctly lol. I appreciate the input on the plate fed TS also. These are definitely ideas I'd like to explore but definitely a long term project for me.

 

[VaporDemon]

Im not a fan of plate driven stacks at all. You get a quack response from them due to the previous stages output impedance being nonlinear across all frequencies a TMB tonestack typically targets. The benefit of them is that they’re more raw and aggressive. Like Jeremy said it’s a balancing act. Personally they drive me nuts.

Yeah seems like they can be headache inducing lol!

 

[thegame]

Aren't most of the popular Mesa Boogie amps 5 stage designs too?

 

[VaporDemon]

Aren't most of the popular Mesa Boogie amps 5 stage designs too?

Adding a stage to that amp is going to be a long and drawn out process of dropping a lot of signal in multiple stages, creating voltage dividers, changing pot values, controlling frequencies, adding/ increasing filtering etc…. Much trial and error and potentially long nights with alligator clips. Of course anything can be done if you’re willing to invest the time in it.

Plate driven tone stacks are pretty wild to tame. I just finished a 4 stage plate fed design on a 70’s 50 watt Marshall. It’s very complex to get the response and feel correct on them. CF designs are much easier to get dialed in, in my experience.

I’d personally just tune the 4 stages. Plenty of tight gain available that way.

Is that the one you recently uploaded the short clip of on YouTube? Sounds killer man! I wanted to ask you also, do you have a preference or recommendation on coupling cap brand/type/model?

 

[RedPlated]

Is that the one you recently uploaded the short clip of on YouTube? Sounds killer man! I wanted to ask you also, do you have a preference or recommendation on coupling cap brand/type/model?

Yup that’s the one. It’s a nasty SOB. And still cleans up incredibly well with guitar volume.

I used some orange drops and Synergy in that one. But I primarily use Vishay MKT1813’s.

 

[VaporDemon]

Yup that’s the one. It’s a nasty SOB. And still cleans up incredibly well with guitar volume.

I used some orange drops and Synergy in that one. But I primarily use Vishay MKT1813’s.

Awesome man, appreciate the info.