Want Pre500 tone? Here's how to get it!

[kramerxxx]

What can be done on a 3 channel dual just to increase the upper mids a little. I'm happy with the gain where it is. I'd just like to open it up a little i guess. Thanks in advance!

What you can do is remove and jump the (3) 100 ohm resistors on the cathodes of V1, V2, and V3 and remove the 82pf cap/2m circuit from V1.
That will give you want you described above without the gain boosts of changing the pots.

I have got to give this a try. Just so I'm clear, on the 82pf cap/2m circuit, do you mean to remove the Capacitor AND the resistor right next to it, or just the Cap? What does the '/2m' mean? Sorry.

 

[kramerxxx]

Old 3 channel:



Mesa used 10 ohm resistors here in both amps for some reason when they are listed at 100 ohms on the schematics, and 100k gain pots :?
No wonder why the old 3 ch heads differed so from the 2 ch heads, my old head was setup just like this, found an old pic and compared with those above :twisted:[/quote]

My amp has a different value resistor underneath the big orange cap. it is the 6th resistor from the inside.

On the resistors, is there any reason to not JUST put the jumper in place and leave the resistor? That way I could try it, if I didn't care for the sound I could just take the jumpers off instead of re-installing the resistors? Current should travel path of least resistance so across the jumper, not the resistor, righht?

 

[Shemham]

Old 3 channel:
On the resistors, is there any reason to not JUST put the jumper in place and leave the resistor? That way I could try it, if I didn't care for the sound I could just take the jumpers off instead of re-installing the resistors? Current should travel path of least resistance so across the jumper, not the resistor, righht?

In my view you can just jump it and the resistor will be bypassed. This is actually what I did to my Recto.

 

[JCDenton6]

I have got to give this a try. Just so I'm clear, on the 82pf cap/2m circuit, do you mean to remove the Capacitor AND the resistor right next to it, or just the Cap? What does the '/2m' mean? Sorry.

Yes, remove the cap and resistor completely. 2m is a 2 meg resistor.

 

[kramerxxx]

OMG!!!!!!


This is what the 3ch Dual Rectifier Should have sounded like from the beginning. Better Cleans, better Presence, better Gain.... BETTER.

I removed the 3 100ohm resistors, the 1 cap/resistor and the other capacitor. This effected the global sound of the amp. It removes a certain 'dullness' and scooped sound that is probably the reason the amp always gets accused of getting lost in the mix for. More mids, a little more treble, better feel and pick dynamics.

I replaced the Red Channel Gain pot with a 1M, Audio taper. I replaced the Presence with a 250k Linear taper. I am going to order the 250k Audio taper model and replace the linear pot. It works but the sweep really comes on hard at the end. BUT.... It is still better than Stock. It is not as radical in Vintage or Raw for the Red Channel and I'm thinking that the 250k Audio taper will change that.

I currently have Mesa EL34s in it. I can see going back to 6L6s with it setup like this. I tried it with both Tube/Silicon rectification and Bold/Spongy. Sounded very good every way. Tube rectification had a sweetness to it for soloing. Bold made the Cleans really Pop.

Thank you everyone for posting this and answering my questions. I'm very pleased with the end results and I've not even done the Orange channel yet.


Steve

 

[rpurdue]

OMG!!!!!!


This is what the 3ch Dual Rectifier Should have sounded like from the beginning. Better Cleans, better Presence, better Gain.... BETTER.

I removed the 3 100ohm resistors, the 1 cap/resistor and the other capacitor. This effected the global sound of the amp. It removes a certain 'dullness' and scooped sound that is probably the reason the amp always gets accused of getting lost in the mix for. More mids, a little more treble, better feel and pick dynamics.

I replaced the Red Channel Gain pot with a 1M, Audio taper. I replaced the Presence with a 250k Linear taper. I am going to order the 250k Audio taper model and replace the linear pot. It works but the sweep really comes on hard at the end. BUT.... It is still better than Stock. It is not as radical in Vintage or Raw for the Red Channel and I'm thinking that the 250k Audio taper will change that.

I currently have Mesa EL34s in it. I can see going back to 6L6s with it setup like this. I tried it with both Tube/Silicon rectification and Bold/Spongy. Sounded very good every way. Tube rectification had a sweetness to it for soloing. Bold made the Cleans really Pop.

Thank you everyone for posting this and answering my questions. I'm very pleased with the end results and I've not even done the Orange channel yet.


Steve

Awesome! I'm going to do this as well. I don't want any more gain though so I think I'll leave the gain pots as is. Do you think there's still a benefit to change the presence pot if I rarely use the modern mode? Also, how did you jumper those resistors? Just clip them off and solder a connection in between? And the caps are just clipped off all together? Thanks for the help. I just want to be sure before I do it.

 

[Anonymous]

Awesome! I'm going to do this as well. I don't want any more gain though so I think I'll leave the gain pots as is. Do you think there's still a benefit to change the presence pot if I rarely use the modern mode? Also, how did you jumper those resistors? Just clip them off and solder a connection in between? And the caps are just clipped off all together? Thanks for the help. I just want to be sure before I do it.

Do you find yourself turning the presence pot all the way up and the amp is still not bright enough? If not, don't worry about the presence pot.

Just jump the resistors. No need to clip them. This way - as another member suggested - if you don't like it, you can just remove the jumper.

Looking at the schematic, clipping the 2M // 82pF network will cause the amp to not pass signal in some modes. If you jump it instead, you'll bypass the entire first tone network and pass quite a bit more bass. Would definitely recommend the 1M gain pot before doing that.

 

[rpurdue]

Awesome! I'm going to do this as well. I don't want any more gain though so I think I'll leave the gain pots as is. Do you think there's still a benefit to change the presence pot if I rarely use the modern mode? Also, how did you jumper those resistors? Just clip them off and solder a connection in between? And the caps are just clipped off all together? Thanks for the help. I just want to be sure before I do it.

Do you find yourself turning the presence pot all the way up and the amp is still not bright enough? If not, don't worry about the presence pot.

Just jump the resistors. No need to clip them. This way - as another member suggested - if you don't like it, you can just remove the jumper.

Looking at the schematic, clipping the 2M // 82pF network will cause the amp to not pass signal in some modes. If you jump it instead, you'll bypass the entire first tone network and pass quite a bit more bass. Would definitely recommend the 1M gain pot before doing that.

I find in the 2nd channel I can dime the presence with little effect. I'm just wanting to lose the perceived "blanket" that I hear over the amp. So you recommend leaving the 2M 82pF circuit as is?

 

[Anonymous]

I find in the 2nd channel I can dime the presence with little effect. I'm just wanting to lose the perceived "blanket" that I hear over the amp. So you recommend leaving the 2M 82pF circuit as is?

I'd leave it as-is until you try the 1M gain pot.

As for presence, there's not much you can do there with a pot change. The stock value already contains more than enough sweep to get the amp as bright as it's going to get in those modes (orange raw is the only place where a 250k presence pot would have an effect). However, there are two other places where you could make the amp much brighter and more usable in ch. 2.

The first place I'd look is at a 33k resistor directly after the tone stack on the orange channel. Remove it. Actually, you could either remove that or remove the 0.003uF cap (should be right next to it). Either will have the same effect: not allowing the highs and upper midrange to pass to ground. Then, you can use your presence pot to tame any residual high end you may have. Should be a killer mod. Just be aware that orange raw will likely be too bright now, unless you're interested in a more extensive mod.

The other thing you can do - and this will be less effective on the orange channel and might make the red channel too bright - is remove the two 120pF that jump the two plate resistors of the phase inverter (V5). Wouldn't look here before I tried the previous mod I described.

***edit*** Looked further at the schematic, and a simple pot swap absolutely should make the amp brighter. Just be aware that you lose the sweep when you make this change. I.e., only the first 5 - 10% of the pot will affect the amp's tone in orange modern or vintage. However, due to a somewhat ingenious circuit design, the amp will be brighter no matter where the pot is positioned. Highly recommend it, though you may need to try a couple of different values (250k might be too bright). If it's still too dark, then remove the 33k.

 

[rpurdue]

I find in the 2nd channel I can dime the presence with little effect. I'm just wanting to lose the perceived "blanket" that I hear over the amp. So you recommend leaving the 2M 82pF circuit as is?

I'd leave it as-is until you try the 1M gain pot.

As for presence, there's not much you can do there with a pot change. The stock value already contains more than enough sweep to get the amp as bright as it's going to get in those modes (orange raw is the only place where a 250k presence pot would have an effect). However, there are two other places where you could make the amp much brighter and more usable in ch. 2.

The first place I'd look is at a 33k resistor directly after the tone stack on the orange channel. Remove it. Actually, you could either remove that or remove the 0.003uF cap (should be right next to it). Either will have the same effect: not allowing the highs and upper midrange to pass to ground. Then, you can use your presence pot to tame any residual high end you may have. Should be a killer mod. Just be aware that orange raw will likely be too bright now, unless you're interested in a more extensive mod.

The other thing you can do - and this will be less effective on the orange channel and might make the red channel too bright - is remove the two 120pF that jump the two plate resistors of the phase inverter (V5). Wouldn't look here before I tried the previous mod I described.

***edit*** Looked further at the schematic, and a simple pot swap absolutely should make the amp brighter. Just be aware that you lose the sweep when you make this change. I.e., only the first 5 - 10% of the pot will affect the amp's tone in orange modern or vintage. However, due to a somewhat ingenious circuit design, the amp will be brighter no matter where the pot is positioned. Highly recommend it, though you may need to try a couple of different values (250k might be too bright). If it's still too dark, then remove the 33k.

I think I'll start with just jumping those 3 resistors and see what happens. I really only use the amp in the raw modes on both channels so I also don't want to make it too bright either

 

[Anonymous]

I think I'll start with just jumping those 3 resistors and see what happens. I really only use the amp in the raw modes on both channels so I also don't want to make it too bright either

I know that was a wall of text, so to summarize, a 250k presence pot in either channel should do well to take the blanket off. Especially in raw mode, that would give you a great sweep.

 

[rpurdue]

I think I'll start with just jumping those 3 resistors and see what happens. I really only use the amp in the raw modes on both channels so I also don't want to make it too bright either

I know that was a wall of text, so to summarize, a 250k presence pot in either channel should do well to take the blanket off. Especially in raw mode, that would give you a great sweep.

So don't worry about jumping the resistors, just change the presence pots? Do I stay with audio taper? Thanks again for all your help.

 

[Anonymous]

I think I'll start with just jumping those 3 resistors and see what happens. I really only use the amp in the raw modes on both channels so I also don't want to make it too bright either

I know that was a wall of text, so to summarize, a 250k presence pot in either channel should do well to take the blanket off. Especially in raw mode, that would give you a great sweep.

So don't worry about jumping the resistors, just change the presence pots? Do I stay with audio taper? Thanks again for all your help.

I'd still jump the resistors, but that's IMO more of a response thing than making the amp brighter. Probably would go for audio if you're in Raw mode most of the time, though linear would give you a better sweep for the other modes. It's just a cosmetic preference though; no tonal difference.

 

[Anonymous]

In other news, I've been working on my Rectifier clone recently to make it a little more metal. I haven't been happy with the way it records....too sloppy and dark. To improve it, I made the following changes from stock Red Modern:

1. No 100 ohm resistors on cathode
2. 1M gain pot
3. 500pF treble cap instead of 680.
4. Removed 120pF caps at phase inverter
5. Installed a feedback loop, 100k to the 8 ohm tap.
6. Removed presence circuit altogether.

Sort of a cross between Red and Orange Modern at this point. I'm trying to get the most out of it as possible. Might even switch to KT88s depending on how it reacts cranked up...

Anyway, here's a (whisper volume) clip:

http://tonefinder.com/?section=id&value=14281

Signal chain: LP Faded --> SD Distortion --> amp --> Marshall 1960a --> G12M greenback --> Unidyne 545 (SM57)

 

[JCDenton6]

^ Kick ass, that's noticeably tighter than your last clip.

 

[2CDR]

excuse my noobness,but can one of you please explain what jumping is?or better still a pic?

 

[kramerxxx]

excuse my noobness,but can one of you please explain what jumping is?or better still a pic?

To Jumper means to 'Go Around the component'. What I did was unsolder the resistors from the Printed Circuit Board, (PCB). I then took a new resistor I had in my stash and cut the leads off of it, threw that resistor away. I used the leads, (*just the Wire - no resistor), and soldered that back in place of the resistor I took off the PCB.

As was suggested above, you could take the same piece of wire and just solder around the existing resistor. Electricity flows to the path of least resistance so by soldering the wire across the resistor on the PCB you've effectively 'Jumped' over it. e.g. Jumpered it.

 

[kramerxxx]

Awesome! I'm going to do this as well. I don't want any more gain though so I think I'll leave the gain pots as is. Do you think there's still a benefit to change the presence pot if I rarely use the modern mode? Also, how did you jumper those resistors? Just clip them off and solder a connection in between? And the caps are just clipped off all together? Thanks for the help. I just want to be sure before I do it.

If you put the 1 Meg pot in, you don't HAVE to turn it all the way up. In other words, when you install it, you get the benefit of additional gain if you choose to turn the pot up to that level, but you don't need to for it to sound MUCH better.

I tried the Red Channel I installed the 1M pot in at every gain position of the sweep and it was just better no matter where I put it.

I did notice that it didn't work the same in all modes. I only play the amp for about an hour so didn't try everything and document it. I plan on spending some time with it again tonight.

I did like it well enough though to get up early this morning and install the 1M pot in the Orange channel, along with the Linear 250k Presence Pot. I order some Audio taper pots as I want to try both, to see what I like better. Right now the Linear Pots in the Presence circuit sounds fine.

 

[kramerxxx]

Has anyone changed the Presence Pot in the Clean Channel of a 3ch Dual Rec?

 

[2CDR]

excuse my noobness,but can one of you please explain what jumping is?or better still a pic?

To Jumper means to 'Go Around the component'. What I did was unsolder the resistors from the Printed Circuit Board, (PCB). I then took a new resistor I had in my stash and cut the leads off of it, threw that resistor away. I used the leads, (*just the Wire - no resistor), and soldered that back in place of the resistor I took off the PCB.

As was suggested above, you could take the same piece of wire and just solder around the existing resistor. Electricity flows to the path of least resistance so by soldering the wire across the resistor on the PCB you've effectively 'Jumped' over it. e.g. Jumpered it.

Thank You Sir. I was thinking it had something to do with that but wanted clarification before i did it.