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

[Anonymous]

So I realise that this thread has evolved a lot from when it started, and after reading the whole thread multiple times, and I've come to the conclusion, that I'm pretty lost in what the answer to a nicely modded 2ch rectifier without rewiring any gain stages or anything too complicated is.

I think it could be nice, if you guys could do a little step on step like the first post, and help out someone like me, without the extreme knowledge about engineering, and what stuff like 2m/680k circuit actually means..

Would really appreciate it!

After everything that's been gone through, it really does seem there's only a slight difference between revisions. Most notable of C/D are the following:

1. Higher presence pot value (220k, I believe, instead of 100k) makes the entire amp brighter
2. No LDRs on the preamp cathodes means a slightly tighter, dryer tone
3. Different output transformer (which, although present on later revisions, I believe plays a role here with the aforementioned differences)

There are other changes, but as far as I can tell, that's what it takes to get C/D red modern. Because of the layout on later 2-channel revisions, there's no simple mod to get early revision tone. It's possible to get, but you'd need to understand the circuitry. Perhaps someone else here can lay it out in an easy to understand manner, but I don't own a Rectifier right now for experimenting.

As for 3-channel models, it should be easier to get the early Rectifier tones out of these (you might even be able to get a replacement Mark III transformer, but again, you'd need to understand basic circuitry). However! The 3-channel models uses a different power supply, which is, I believe, why these inherently sound and feel different from 2-channels.

As for your question:
I believe a nicely modded 2-channel will have the following two changes.

1. Replace the stock 250k gain pot with a 1M pot
2. Remove C12 (I think this is the correct number, but the schematic I'm looking at might be labelled incorrectly), the 20pF cap connecting V2A pin 2 to ground.

The pot gives you a gain boost and removing the cap gives you a nice, tight attack. Like a boosted Rectifier, but without the inherent fizz most pedals give and with stronger mids.

 

[JCDenton6]

He pretty much nailed it in his post but don't forget to change out the cap in C55 to a .0047uf like in the first initial post.
If you want to go further with the mods I'll repost pics that I have taken with some clear instructions (I've been meaning to do so for a while).

 

[Anonymous]

He pretty much nailed it in his post but don't forget to change out the cap in C55 to a .0047uf like in the first initial post.
If you want to go further with the mods I'll repost pics that I have taken with some clear instructions (I've been meaning to do so for a while).

Honestly, I wouldn't even bother with that one. After some testing, I can't hear any difference with or without it in the circuit.

 

[JCDenton6]

Honestly, I wouldn't even bother with that one. After some testing, I can't hear any difference with or without it in the circuit.

Hmm, ok.

After everything that's been gone through, it really does seem there's only a slight difference between revisions. Most notable of C/D are the following:

1. Higher presence pot value (220k, I believe, instead of 100k) makes the entire amp brighter

This is what I still wonder about, I feel my tone is Rev D tone and I'm happy with it, but still on the fence about switching out the presence pots.
I wonder if the pots affect the power amp like the 1 meg gain pots affect the preamps feel/tone?

 

[Anonymous]

1. Higher presence pot value (220k, I believe, instead of 100k) makes the entire amp brighter

This is what I still wonder about, I feel my tone is Rev D tone and I'm happy with it, but still on the fence about switching out the presence pots.
I wonder if the pots affect the power amp like the 1 meg gain pots affect the preamps feel/tone?

How high up do you turn your presence knob? If it's all the way up and still not bright enough, then I'd definitely consider going to a higher value pot. Otherwise, I wouldn't bother. For me, the stock 100k value is plenty bright.

 

[TheMadMacBook]

Hey JC, I'd love some pics for further experimenting, when I've done the basics as Magic mentioned in the earlier post
I'll post some comparison clips later, when I get some pots!

 

[JCDenton6]

@TheMagicEight:

I usually run my presence around 9-12:00 depending on the guitar. I also have been running EL34's that were in the Triple when I bought it so that could account for the darkened top end.

@TheMadMacBook:

Sure, I'll round up my pics and post them later tomorrow.

 

[Anonymous]

I usually run my presence around 9-12:00 depending on the guitar. I also have been running EL34's that were in the Triple when I bought it so that could account for the darkened top end.

I wouldn't bother then. The 220k presence pot would just mean you'd have to turn it down further.

 

[TheMadMacBook]

So i did the mod as described by Magic, and I must say, that turned it into a gain monster man.
I have what what usually be gain at 3 o'clock now at 9:00 and the rest is just insane. Im not sure why you would want that much gain tho, It got really fizzy at about 1 o'clock
It also removed my use of my overdrive, which i used to boost with, but now I'm not even able to boost it, unless I use my guitar with Emgs..
It also totally destroyed the use of the clean option, since i can't even have the gain at 7:00 before it breaks..
So overall, Im not sure its really worth it, but i will see tomorrow, where i get to crank the amp i little, and hopefully I will be posting some clips, (gonna do an A B comparison vid, already did the "before" part) And then i'll hopefully be able to judge more specific.

 

[JCDenton6]

Here is a full rundown on what I've done to my amp so far:

Remove R277 and install a jumper.


Remove R272 and install a jumper. Change the cap at C55 from .10uf to .0047uf. (the smaller orange drop cap in front of the larger 3)


Remove R271 and install a jumper.


Remove R110 (680k) and replace with a 470k, remove R322 and C10 (both which are behind that red cap.


Clip and jump LDR 4, just cut the leads as close as you can to the body of the LDR and just solder the leads together on both sides.


This includes changing both gain pots to 1 meg and changing the cap at C55 from .10uf to .0047uf.
Doing this will boost your high gain tones significantly, but will however turn your clean channel into an overdrive channel. It will also clear up that fizz that you are talking about.

I however rarely use cleans so this was right up my alley.
However, use caution while desoldering/soldering in these tight areas, these traces can lift if you use too much heat with your iron.
If you don't have an adjustable soldering station use a 15-25w iron, or keep your soldering station at 650-700F.

 

[Shemham]

Just wow! This topic has been extremely educative. Thanks a bunch guys for all the hard work!

Now I've started to wonder what exact changes Mesa did to post-2010 rectos to alter the tone/feel to its current form. I've been trying to find schematics for Multi-watt rectos, but so far I only keep finding them for the 2-channel and non-multi-watt 3-channel models. Seems like there are none available yet, but just to be certain I wanted to check if someone here would have some information on the component changes - or even better - the schematics for the Multi-watt models?

 

[JCDenton6]

Just wow! This topic has been extremely educative. Thanks a bunch guys for all the hard work!

Now I've started to wonder what exact changes Mesa did to post-2010 rectos to alter the tone/feel to its current form. I've been trying to find schematics for Multi-watt rectos, but so far I only keep finding them for the 2-channel and non-multi-watt 3-channel models. Seems like there are none available yet, but just to be certain I wanted to check if someone here would have some information on the component changes - or even better - the schematics for the Multi-watt models?

I just now saw your post, the reason there aren't any multi watt schematics available is it an amp that Mesa currently produces, they will only provide them to techs.

 

[APEMAN]

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[Shemham]

I just now saw your post, the reason there aren't any multi watt schematics available is it an amp that Mesa currently produces, they will only provide them to techs.

Ok, thought as much. I can also safely assume that they don't want to share their trade secrets on their sound on the new Rectos.

Multiwatt schematics ... I got them (I think I got all rectos apart from the MR (including Roadster RK1 RK2 tremoverb {MkV}....)), I called them and asked for schematics and they send them to me if I promise not to spread them ... true story and of course very very easy.

But don't belive you find a different cap value or resistor ... basically the sound sections are identically. Which means they didn't draw the fine differences, again...

So to conclude on the previous posts I can safely assume that Mesa doesn't want to share on the changes between the revisions. Seems that I have to open up the head and see the differences myself that were introduced between the revisions (just wondering if it voids the warranty automatically if I open up the head to compare and post the differences between the Reborn and original 3ch head...Since I could pretty much see the differences between the component values)

 

[Jorn218]

I read this thread a couple times and would like to have a go with some of the mods described. I have a 3ch dual(non multiwatt) and from my reading is that the first change would to be installing a 1M pot in the red channel for the gain pot. There are a couple of other resistor/capacitor changes, but would rather look at a schematic and then locate them on the board. Does anyone have a 3ch schematic, and know which resistor/capacitor numbers that need changing/jumpering are would be appreciated. Someone mentioned the D power rail, where on the mesa is this located? pins 1 and 6 from v-which?

(edit)Never mind I found it. the 10nF/450V cap to ground is best placed after the 100k resistors or closer to the diodes? in the D power rail?

 

[APEMAN]

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[Jorn218]

Hey Apeman, Yes I know the cap goes after the resistor, not between the socket pin and the resistor. Sorry if I wasn't descriptive enough. I was asking others who have done this to a 3ch., if it is easier to place it close to the resistor, or closer to the other end of D power rail, closer to the rectifier end. Electronically it shouldn't matter as long as it is placed somewhere between the resistor and the diodes. I just had my amp open to swap out the gain pots for the red and orange channels, red 1M, and trying a 500K for the orange channel. Seems that value others seemed to like in the orange 2ch duals.

I decided to try using the 10nF cap instead of the 5nF as someone mentioned that the Tremoverbs used that value and it sounded best to his ears. It smoothed things out a tad and removed some of the fizz. The 1M will add enough gain so that fizziness could pose a problem. The 10nF may take care of that.

I think I may take a gut shot of my amp so I can get help with others on where exactly the proper 100K cap is. I was a bit surprised by the layout as I have only worked with Marshall and Fender amps in the past where the circuit layout on the board was a little more straight forward. I am guessing that the 3ch duals have dual sided boards? I see the 100K resistor coming off v2 pin 6, but cannot see the trace for pin 1. Do both pins go into the same resistor or is there another 100K for pin 1? I am looking for a brn/blk/yel striped resistor, but the closest resistor to pin 6 is brn/blk/brn??

here is v2
http://www.flickr.com/photos/92372029@N04/8393141807/
here is diode area
http://www.flickr.com/photos/92372029@N04/8393141299/

Not to derail the thread, but anyone want to take a guess at what this stuff is? Seems to be coming from one of the transformers. Looks like melted candy.
http://www.flickr.com/photos/92372029@N04/8394226932/
http://www.flickr.com/photos/92372029@N04/8393140297/

 

[JCDenton6]

Not to derail the thread, but anyone want to take a guess at what this stuff is? Seems to be coming from one of the transformers. Looks like melted candy.
http://www.flickr.com/photos/92372029@N04/8394226932/
http://www.flickr.com/photos/92372029@N04/8393140297/

That looks to be what is used to coat the iron making up the transformer, shellac.
I assume it's dry?

Also if you can, can you take a few high rez shots of the entire board?
Thanks!

 

[APEMAN]

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[Jorn218]

Apeman, too late already swapped pots out. If I like the pots, I will call Mesa next week and order their part as I am using two normal sized Alpha pots. This way everything looks stock. What I am mainly after is more usable gain out of the amp without having to resort to a gain box as clean boost up front. To me the 3ch Duals sound neutered from the 2ch. Also I am not a fan of the inherent scooped tone of the amp. In the bedroom this is cool, but in a band situation, My amp washes out. Even using some extreme settings. Though this thread reminded me that the treble pot acts as a voltage divider to the rest of the tone circuit, ie. the more highs you dial in, the less current goes to the rest of the tone stack. Going to try using the aforementioned settings of everything at noon with mids dimed.

I am after this type of percussive tone
http://www.youtube.com/watch?v=MbBU5VIZ2A4

vs. this is the type of gain Im getting from my amp now with OD808 out front and 10 band graphic in the effects loop.
http://www.youtube.com/watch?v=TLotWFQiSj0

The first YT link is to Malevolent Creation, the second to my band. I know the studios are different, as are the mixes, but the first link the guitars are mid predominant, where my bands guitars are more scooped sounding.


@JCDenton - I will take some more gut shots either tomorrow, or Monday. I have a gig tonight and today is going to be spent tailoring my amp to the pot swaps I have done to get through the show tonight.
Yes I do believe it is the shellac used to cover the transformer windings as you mentioned. I just wondered if this was something I should be concerned about? It is dry, but should the leaking stop, or is this something that will continue?