Suggestions for specific Low-End tweak I'm looking for

[Travis_HY]

The EVH Marshall has a couple of things that will add bass. One is a giant 220uf cap across the EQ's cathode 820ohm (or 1k) resistor but you can experiment with that value. .68 is pretty spicy in the high end but it certainly has a cool sound with humbuckers. I like 1uf there too, 4.7uf and 10uf are a cool sound with Teles and Strats, and the giant EVH cap is for maximum gain all the way down to something crazy, single digit HZ or something.

Ed only used the lead channel and it was stock with the typical 2.7k/.68uf/.0022uF deal. Adding bass by increasing the cathode cap kind of goes away from the classic Marshall trip to my ears but you can add an additional .68uF across that Lead channel cathode and see if you like it. There aren't any rules with that cathode cap really-just tweak it till you like it, I suppose.

A schematic of what you are working with could also be helpful with tweaking points, but I know it can also be a pain to write out a schematic. Either way, hope you make some headway on it.

[Stevem]

What current drawvdo you have your outout tubes idling at?

You want the tubes idling at 60% and I assume your running 425 to 450 volts on the plates?

If so here's the millamps they should idle at to attain that 60%.
425V = .035

435V = .034

450V = .033

You can go as high as 70% if your running the JJ/ Groovetubes EL34S which is a 30 watt tube and not suffer a lesser tube life.

Driving the output tubes harder will definitely crunch up the low end more!

[Roe]

The EVH Marshall has a couple of things that will add bass. One is a giant 220uf cap across the EQ's cathode 820ohm (or 1k) resistor but you can experiment with that value. ....
Ed only used the lead channel and it was stock with the typical 2.7k/.68uf/.0022uF deal. Adding bass by increasing the cathode cap kind of goes away from the classic Marshall trip to my ears but you can add an additional .68uF across that Lead channel cathode and see if you like it. There aren't any rules with that cathode cap really-just tweak it till you like it, I suppose.
...

no, the v1b cathode resistor is 820R, not 2k7.

[Phil_S]

Detail matters, especially so with such a nebulous query.
It’s hardly that big of an ask for you to sketch out the schematic, note the values, and take / upload a photo of it, surely?
A Marshall 50 is not a specific thing, there are variants.
What you’ve got in front of you may be obvious to you, but that doesn’t work over the internet.

Consider what this looks like. And I assure you that I am not intending to be mean spirited. This is just, in my view, the cold truth.

Given the volunteer nature of the group, your response that you've already posted information isn't adequate. Do you expect these generous volunteers to print a schematic and pencil in the adjustments just so they can have a conversation with you?

You are asking people you don't really know to help you. They are more than willing. That alone is a testament to their humanity and dedication to the topic. It isn't such a big request for an updated schematic. It is what you should do to encourage intelligent conversation about your question. Give a little to get a lot. Post the schematic. It's a critical item. They would do the same if you made such a request.

[Travis_HY]

The EVH Marshall has a couple of things that will add bass. One is a giant 220uf cap across the EQ's cathode 820ohm (or 1k) resistor but you can experiment with that value. ....
Ed only used the lead channel and it was stock with the typical 2.7k/.68uf/.0022uF deal. Adding bass by increasing the cathode cap kind of goes away from the classic Marshall trip to my ears but you can add an additional .68uF across that Lead channel cathode and see if you like it. There aren't any rules with that cathode cap really-just tweak it till you like it, I suppose.
...

no, the v1b cathode resistor is 820R, not 2k7.

That's incorrect in a 1959 like Ed's. It was a split cathode Super Lead where V1a is the Bass channel with the 820r/320uf/.022uF arrangement, while V1b is the Lead channel with the 2.7k/.68uF/.0022uF arrangement.

I was referring to the V2, pin 8 820r cathode of the cathode follower driving the EQ. Like I said, Ed never used the V1a Bass channel with the 820r/320uF/.022uf configuration. He only used the Lead channel which is built around V1b.

[lgehrig4]

What current drawvdo you have your outout tubes idling at?

You want the tubes idling at 60% and I assume your running 425 to 450 volts on the plates?

If so here's the millamps they should idle at to attain that 60%.
425V = .035

435V = .034

450V = .033

You can go as high as 70% if your running the JJ/ Groovetubes EL34S which is a 30 watt tube and not suffer a lesser tube life.

Driving the output tubes harder will definitely crunch up the low end more!

460V. I just increased the bias to 40mW. Not much of a difference, but I like the way it sounds and I don't care about tube life.

[lgehrig4]

Detail matters, especially so with such a nebulous query.
It’s hardly that big of an ask for you to sketch out the schematic, note the values, and take / upload a photo of it, surely?
A Marshall 50 is not a specific thing, there are variants.
What you’ve got in front of you may be obvious to you, but that doesn’t work over the internet.

Consider what this looks like. And I assure you that I am not intending to be mean spirited. This is just, in my view, the cold truth.

Given the volunteer nature of the group, your response that you've already posted information isn't adequate. Do you expect these generous volunteers to print a schematic and pencil in the adjustments just so they can have a conversation with you?

You are asking people you don't really know to help you. They are more than willing. That alone is a testament to their humanity and dedication to the topic. It isn't such a big request for an updated schematic. It is what you should do to encourage intelligent conversation about your question. Give a little to get a lot. Post the schematic. It's a critical item. They would do the same if you made such a request.

I think you misunderstood me. I never said that it was a big deal to sketch out a schematic and I planned on posting a photo of the chassis. I just didn't think it mattered in the context of the question that I asked, or at least thought I asked.

Forget my amp for a second. You guys know amp circuits and you know what to expect when component values are changed in the different parts of the circuit. An increase in the NFB resistor of a Fender I assume would have a similar affect as it does on a Marshall? I'm just looking to understand the parts of this circuit that could potentially help me achieve what I'm looking to do. From there I can experiment.

Anyway, I think I've gotten plenty to chew on to get me started. Thanked to all!

[pompeiisneaks]

Detail matters, especially so with such a nebulous query.
It’s hardly that big of an ask for you to sketch out the schematic, note the values, and take / upload a photo of it, surely?
A Marshall 50 is not a specific thing, there are variants.
What you’ve got in front of you may be obvious to you, but that doesn’t work over the internet.

Consider what this looks like. And I assure you that I am not intending to be mean spirited. This is just, in my view, the cold truth.

Given the volunteer nature of the group, your response that you've already posted information isn't adequate. Do you expect these generous volunteers to print a schematic and pencil in the adjustments just so they can have a conversation with you?

You are asking people you don't really know to help you. They are more than willing. That alone is a testament to their humanity and dedication to the topic. It isn't such a big request for an updated schematic. It is what you should do to encourage intelligent conversation about your question. Give a little to get a lot. Post the schematic. It's a critical item. They would do the same if you made such a request.

I think you misunderstood me. I never said that it was a big deal to sketch out a schematic and I planned on posting a photo of the chassis. I just didn't think it mattered in the context of the question that I asked, or at least thought I asked.

Forget my amp for a second. You guys know amp circuits and you know what to expect when component values are changed in the different parts of the circuit. An increase in the NFB resistor of a Fender I assume would have a similar affect as it does on a Marshall? I'm just looking to understand the parts of this circuit that could potentially help me achieve what I'm looking to do. From there I can experiment.

Anyway, I think I've gotten plenty to chew on to get me started. Thanked to all!

I think you're misunderstanding how much topology of the amp can impact this. Some suggestions may have 0 impact if the amp is setup with a specific type of topology. Some may make things worse instead of better if another is used.

Understanding the exact circuit would tell them something maybe very quickly as well that would be a very simple, exacting solution for what you need. Instead there are a lot of great educated guesses, all of which might not work at all and wouldn't have been suggested had they known the actual circuit. They still offered suggestions, despite the lack of information they asked... because they wanted to help.

Hope that makes sense?

~Phil

[Roe]

The EVH Marshall has a couple of things that will add bass. One is a giant 220uf cap across the EQ's cathode 820ohm (or 1k) resistor but you can experiment with that value. ....
Ed only used the lead channel and it was stock with the typical 2.7k/.68uf/.0022uF deal. Adding bass by increasing the cathode cap kind of goes away from the classic Marshall trip to my ears but you can add an additional .68uF across that Lead channel cathode and see if you like it. There aren't any rules with that cathode cap really-just tweak it till you like it, I suppose.
...

no, the v1b cathode resistor is 820R, not 2k7.

That's incorrect in a 1959 like Ed's. It was a split cathode Super Lead where V1a is the Bass channel with the 820r/320uf/.022uF arrangement, while V1b is the Lead channel with the 2.7k/.68uF/.0022uF arrangement.

No, the 2k7 was introduced much later. A 12000 series 1959 from 1968 has the 820R, as does many of the 1969 amps. This is an important part of the sound and affects the low end significantly. See my paper on the evolution of the 100w plexi in Doyle's last marshall book

[lgehrig4]

Consider what this looks like. And I assure you that I am not intending to be mean spirited. This is just, in my view, the cold truth.

Given the volunteer nature of the group, your response that you've already posted information isn't adequate. Do you expect these generous volunteers to print a schematic and pencil in the adjustments just so they can have a conversation with you?

You are asking people you don't really know to help you. They are more than willing. That alone is a testament to their humanity and dedication to the topic. It isn't such a big request for an updated schematic. It is what you should do to encourage intelligent conversation about your question. Give a little to get a lot. Post the schematic. It's a critical item. They would do the same if you made such a request.

I think you misunderstood me. I never said that it was a big deal to sketch out a schematic and I planned on posting a photo of the chassis. I just didn't think it mattered in the context of the question that I asked, or at least thought I asked.

Forget my amp for a second. You guys know amp circuits and you know what to expect when component values are changed in the different parts of the circuit. An increase in the NFB resistor of a Fender I assume would have a similar affect as it does on a Marshall? I'm just looking to understand the parts of this circuit that could potentially help me achieve what I'm looking to do. From there I can experiment.

Anyway, I think I've gotten plenty to chew on to get me started. Thanked to all!

I think you're misunderstanding how much topology of the amp can impact this. Some suggestions may have 0 impact if the amp is setup with a specific type of topology. Some may make things worse instead of better if another is used.

Understanding the exact circuit would tell them something maybe very quickly as well that would be a very simple, exacting solution for what you need. Instead there are a lot of great educated guesses, all of which might not work at all and wouldn't have been suggested had they known the actual circuit. They still offered suggestions, despite the lack of information they asked... because they wanted to help.

Hope that makes sense?

~Phil

Understood. Thank you for feedback

[lgehrig4]

Here are some photos of the board. I don't quite remember what the value of the smaller (in size) split cathode cap was. All I remember is that I used the similar values that Frank Levi used on one of his amp mods. I also forgot the value of the cap in parallel to the NFB resistor. I tried a bunch until I found the combination I like the most. This gave me more gain and retained the low end nicely.

[Travis_HY]

no, the v1b cathode resistor is 820R, not 2k7.

That's incorrect in a 1959 like Ed's. It was a split cathode Super Lead where V1a is the Bass channel with the 820r/320uf/.022uF arrangement, while V1b is the Lead channel with the 2.7k/.68uF/.0022uF arrangement.

No, the 2k7 was introduced much later. A 12000 series 1959 from 1968 has the 820R, as does many of the 1969 amps. This is an important part of the sound and affects the low end significantly. See my paper on the evolution of the 100w plexi in Doyle's last marshall book

I understand. He actually had two of these amps, and one of then was 820r/.68 and the other was a 2k7/.68. The "main" one I saw was 820r so that was my mistake. Another, which had the natural wood headshell was 2k7 so I got confused.

The "main" amp that had the 820r V1b also had a 50k Middle pot and the aforementioned large cathode bypass cap for the V2 EQ (330uf), which the 2k7 "natural" amp didn't have. The "natural" was .68uF for the v2 bypass cap.

Sorry for the confusion. Those amps changed specs quite a bit over the years. Small changes, but significant changes tonally.

[lgehrig4]

Ok, so far I changed the V1b bypass cap back to .022 from .0022 and the phase inverter coupling caps to .022 from .1

Too late to crank it up but this is what I noticed so far. Before I wouldn't have called the amp congested by all means, but these changes have made the amp sound more airy and almost acoustic. Not night and day but the difference is apparent. Also feels like I can turn the bass up a bit more to be where I was before. Again, not a huge difference, but noticeable. Can't wait to turn it up tomorrow and determine my next move.

[lgehrig4]

Just wanted to update this thread. I ended up doing the Bainzy mod on this amp (adding 3rd preamp) and I absolutely love what it did, plus the bonus is that I can switch it off and have a stock plexi as well. Actually 2 bonuses. I had a cap on the bright volume push/pull and I never cared for how it sounded with the stock plexi, but with the 3rd preamp engaged the it sounds great. I changed that cap since taking these photos from a 250pf ceramic to a 120pf silver mica and for me it's perfect now. Next up I need a MV. This amp is very loud and the sweet spot leaves my ears ringing.