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

I got moded my rev F recto last week...There is push/pull switch on gain pot so there is option to use it as standard stock recto or run in "tight mod" which is based on pre 500 circuit...I´ll do record some samples this weekend so I´ll place it here soon...

A SWITCHABLE mod!!???

That's WAY cool! Looking forward to the clips!

Hey guys...Just quick sample...I wanted to make it sound raw and natural without any effects or post production tricks...Double tracked,mic straight to center of dust cap...

Recto setting:
Bold/Diode
Red/Modern
Pres 10 o´clock
Bass 11 -----
Mids 12 -----
Treble 1-2 ---
Gain 12 ---- (500K pot)

https://soundcloud.com/wolfernus/mesa-dual-recto-f-rev-tight

wolf said:

I got moded my rev F recto last week...There is push/pull switch on gain pot so there is option to use it as standard stock recto or run in "tight mod" which is based on pre 500 circuit...I´ll do record some samples this weekend so I´ll place it here soon...

Click to expand...

so your using a pot that is switchable? from 250k to 500k?

We just changed stock 250K gain pot for push/pull 500K pot but only on red channel...It was not necesary because it has enough gain with stock one but Soldano uses 500K pot on SLO 100 so it was just experiment...So I can get same amount of gain at 12 o´clock as with 250K pot at 3-4 o´clock....Also 500K does open sound little bit more and also I can hear fuller mids...

That clip sounds pretty good Wolf, I might grab a push/pull for the orange channels gain pot.

Retubed my Triple with Mesa STR-440 tubes and finally got around to mixing a track:

http://tonefinder.com/files/641375090042-Flatulence.mp3

JCDenton6 said:

Retubed my Triple with Mesa STR-440 tubes and finally got around to mixing a track:

http://www.tonefinder.com/files/531374833525-Flatulence.mp3

Click to expand...

Sounds good man...I was tweaking my recto a bit so I made just another quick sound clip too.....

https://soundcloud.com/wolfernus/92-dual-recto-sound-test

That sounds sweet, nice and tight!

Man... I think I'm becoming addicted to tracking songs now! :lol:
Decided to re-visit an old song from a old band of mine.

http://www.tonefinder.com/files/691375081764-Robotic%20Halocaust.mp3

I would like to try this myself some day. However, after reading so many pages, my head spinning...I have a Rev G Dual, just which mods are the ones I want to try? The ones in the first post? Or something else?
I was planning to attempt this with push-pull pots and switchable circuit changes so I can get the stock G sound and the "pre 500 style" sound from the same head. I'm not particularly afraid to mod my G like this since, technically, it's no longer in original condition anyway. Its channel cloning switch died a few years ago and, unable to find a similar 3-way switch, I replaced it with a mini-toggle. Also, the original (slightly malfunctioning) PT has been upgraded to a better one. This looks like an interesting mod to try next.

...there are just too many posts in this thread, I'm not sure which instructions I need to follow. Could someone briefly summarize please?

If you're looking to go full on with this, taking your amp to Rev C specs, here are the changes you would have to make,

I'd call it more of a "reversion" to old specs than a "mod"

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.


You can also just solder a jump across the resistors/caps that I've removed if you want to make this reversible.
Another thing you can do to add a little more brightness/cut is to lift C12, opens up the high end a bit.
I left this cap in since it helps define the recto voice a bit.

This includes changing both gain pots to 1 meg, changing the presence pot to 250k in the Red channel. I left the 25k in the orange channel since the whole amp gets brightened up with the single pot change to 25ok in the red channel.

Doing this will boost your high gain tones significantly, but will however cause your cleans to have grit to them (but if you slowly raise the gain you'll find a nice sweet spot) It will also clear up that fizz.

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.

Wow, sounds like my BFG Amplification mods I had done to turn my DR into one of the best amps I have heard.

Excellent, thanks for the summary, JCDenton! If I could give a thumbs-up or a like for your post, I would.

Definitely something I want to try. But that's a bit more complicated than the version in the first post...not sure if trying to make all that switchable is a feasible idea.

JCDenton6 said:

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.

Click to expand...

All excellent info, but I would actually go the other way on the soldering iron. I personally set my iron to 750F. The idea is that it will melt the solder faster, allowing you to work faster, and thus allowing less heat transfer to sensitive parts. This is what's advised in the industry.

Sorry to bring back an old thread, but I figured I'd ask...

I'm going to do this mod my multi-watt dual, and it looks like what I'm doing is:
-jumping the 100 ohm resistors on the cathodes
-swapping the Ch 2 and Ch 3 gain pots to 1M
-reworking the filter network before the gain pot, namely clipping the 82 pf cap, and replacing the 2.2M resistor with a 1.5M... the reasoning being that the 1.5M and 680K in parallel will yield 470K, the same value as the pre-500's.
-possibly swapping the presence pots to 250K? I think this might be better left alone since the stacked pots might be difficult to find and I think I already have plenty of useful range on the presence control.
-possibly lifting the capacitor between V2A grid and ground... it sounds like something I'd like tonewise, but it doesn't appear to be a part of the pre-500 circuit (I believe), and might just promote unnecessary oscillations without significant changes to the tone as some have made it sound.

It also looks like there's no equivalent of C55 (in the "Rev F" schematic) on the 3 channel heads so I guess I won't bother with that...

Anyways, does it matter where I order the 1M pot from (or the 1.5M resistor)? It would be cool to keep all the parts genuine Boogie if possible, but I'm not sure if that's possible or even matters. Can anyone point me to a link for where to get the parts for this? much appreciated :mrgreen:

rocknroll9225 said:

Sorry to bring back an old thread, but I figured I'd ask...

I'm going to do this mod my multi-watt dual, and it looks like what I'm doing is:
-jumping the 100 ohm resistors on the cathodes
-swapping the Ch 2 and Ch 3 gain pots to 1M
-reworking the filter network before the gain pot, namely clipping the 82 pf cap, and replacing the 2.2M resistor with a 1.5M... the reasoning being that the 1.5M and 680K in parallel will yield 470K, the same value as the pre-500's.
-possibly swapping the presence pots to 250K? I think this might be better left alone since the stacked pots might be difficult to find and I think I already have plenty of useful range on the presence control.
-possibly lifting the capacitor between V2A grid and ground... it sounds like something I'd like tonewise, but it doesn't appear to be a part of the pre-500 circuit (I believe), and might just promote unnecessary oscillations without significant changes to the tone as some have made it sound.

It also looks like there's no equivalent of C55 (in the "Rev F" schematic) on the 3 channel heads so I guess I won't bother with that...

Anyways, does it matter where I order the 1M pot from (or the 1.5M resistor)? It would be cool to keep all the parts genuine Boogie if possible, but I'm not sure if that's possible or even matters. Can anyone point me to a link for where to get the parts for this? much appreciated :mrgreen:

Click to expand...

I'd stick with modding the cathode resistors, 1M gain pots, and 1.5M resistor on the filter network before anything else. The 250k presence pot is unnecessary unless you're already maxing it out. I'd also leave the cap from the V2a grid to ground alone, but you may want to give yourself peace of mind by at least trying it. I personally couldn't hear a difference with it in or out.

As for ordering, I usually use Mouser for resistors (and sometimes capacitors). I usually prefer carbon film resistors, though I think Mesa uses metal film. Shouldn't make a difference for just the one resistor though.

You can find pots on Mouser, too (it'll be cheaper with shipping to get everything from one place), but I typically use Amplified Parts for pots and other guitar-amp-specific parts.

Let us know how it works out for you!

I was preforming maintenance on my 2 ch Triple today and decided to solder C12 (20k orange cap) back in.
I like it better, got a little more low mids and a little more saturation, this cap does define the recto voicing a bit.

I did play the amp for a few minutes before soldering the cap back in, then played it after I was done - same settings ect...

Unexpectedly found a high quality pdf of the traced schematic of the Rev C posted earlier in the thread:

https://dl.dropboxusercontent.com/u/47381724/DualRectifierR0001.pdf

Did some more digging and a Rev C owner here on the board provided some part numbers for the pots (thanks again LesPaul70) and the bass pot values also changed in the post pre 500 amps along with the gain and presence.

The Rev C used a 250k linear pot (# 592738) for bass and presence on the red channel. He couldn't make out the part # for the bass pot on the orange channel but I'm certain that it's the same. Presence on the orange channel stayed at 25k.

I'll solder in the last 250k pot for bass I have on the red channel and post my findings later on. I'll order another one for the orange channel and make the switch as well.

Seems like the mystery of the pre 500 amps is being revealed now, last thing to try is the 3.9nF caps in the presence circuit instead of the 3nF according to the schematic (if correct) :?