XTC R19 gain mod to Blue & Red

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Setneck

Setneck

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Hi!

Some time ago in this topic: http://bognerampforum.informe.com/mods- ... hlight=r19 Brent wrote about certain mod for XTC's Blue and Red Channel: "This will give it more gain in the mids on all lead channels including the plexi channel. In plexi mode its going to be classic marshall crunch to dirty clean. Its very simple to do. Just look for R19 which is a 1k resistor and bypass it (piggy back) with a .68uF cap. Just make sure the leads are soldered down good and thats it".

I tried that lately and I'm quite impressed. The cap bypasses cathode resistor of V3A (R19), which is 3rd gain stage for Blue Channel and 4th gain stage for Red Channel.

The 0.68uF cap gives very nice Marshall swirl to the tone. The sound become slightly more compressed but the tone gets boosted in upper mids. Works especially well with the pre2004 tone (without factory or cameron mod).

Tried also 1uF there (SLO value) which is also cool. That cap works well especially with Red Channel, the tone become nicely tighter.


For those who use R12 Marvel Mod I can tell a secret :) that The Marvel Mod 2 is coming :). It is gonna be R19 mod with three positions: 0.68uF - no mod - 1uF :). So be prepared :gethim: :rock:.


Regards, Andy :)
 
Sounds good. I tried to contact you about purchasing your marval mod. Do you still sell it?
 
Write to Marvel himself to alfisti [at] post.pl, there are a few Marvel Mods still available.

Regards, Andy :)
 
Sorry, I thought you were him. I did send an e-mail to that address and recieved no reply...
 
No, it wasn't me :). Give him a minute to response, as he's currently quite busy (He's an amp maker). He'll answer for sure.

Regards, Andy :)
 
awesome bit of info, for us tweakers. thanks, Setneck! :thumbsup:

i will certainly snag a Marvel 2 board--easier and cleaner than doing it myself.
 
No problem Mate, I love experimenting as well as sharing my ideas with others :).

Today I thought about something else. As You may know, Structure switch bypasses V2A (which is 2nd gain stage for Blue and Red Channel) cathode resistor R11 4.7K with another 4.7K resistor in parallel bypassed by 2.2uF cap. It gives overall 2.35K resistor value bypassed. I find 2.2uF cap a bit muddying the tone so I'm gonna try a combination of 6.8K resistor bypassed with 0.68uF or 1uF cap. It'll give aprox. 2.7K cathode resistor value, so same as in Splawn QR (where 2.7K cathode resistor is bypassed with 1uF cap for both 2nd - if 3rd gear engaged - and 3rd gain stage). I'll see how it would sound.. :)

I'll try the same for V2B (which is 3rd gain stage for Red Channel only) cathode resistor - R12 which is 10K, so the resistor in mod should be 3.3K to give aprox. 2.5K overall value (4.7K would be too much as it would give about 3.2K). BTW, R12 is currently modded by Marvel Mod :).

Regards, Andy :)
 
So, if you have the Marvel Mod, are you going to be able to get the Marvel 2 Mod installed as well? Or is it either or?
 
In fact it is practically possible to install and use 3 mods at the same time in XTC:

- bypass of R11 V2A cathode resistor (2nd gain stage for both Red and Blue Channel) - factory bypassed by Structure switch. So the mod is to be used instead of it, You got to solder the mod straight to the resistor the same way as Marvel Mod

- bypass of R12 V2B cathode resistor (3rd gain stage for Red Channel) - we all use Marvel Mod here

- bypass of R19 V3A cathode resistor (3rd gain stage for Blue Channel, 4th gain stage for Red Channel) - factory clean, with no mod, although I've read somewhere that in early Classics that resistor was bypassed by 0.68uF cap.

Note that R6 V1B cathode resistor (1st gain stage for both Red and Blue Channel - 820R) is factory bypassed by C4 0.68uF cap and it is not switchable. So in fact it is possible to have all gain stages bypassed.

I will want to end up with installing all three mods in my amp, putting two switches in place of optional line-outs on rear panel and R11 mod in place of Low Input jack, that I don't use. I doubt that I will use all mods simultaneously, as it would totally compress the tone of already strongly compressed XTC, I only want to have a different possibilities here :).

But first I will play with different values of resistors and caps for all 3 mods. I hope that especially lowering R11 bypass cap (Structure) will open the tone. I find 2.2uF cap making it a bit unclear as it passes more lower frequencies than 1uF or 0.68uF. As I've said I will try the cap only and the resistor-cap combo here, but I must say that 6.8K + 1uF one (making Splawn's 2.7K + 1uF combo) looks the most promising though :).

BTW, I have lately changed both 2.2uF bypass caps for 1st and 2nd gain stage for 0.68uF and 1uF values (resistors are with values 1.5K for 1st gain stage and 2.7K for 2nd) in my Marshall 6100 and the improvement in tone is huge. I know, it is different amp but it inspired me to try it in XTC too ;).


Regards, Andy :)
 
I wwould like the marvel mod can I put it on the classic?? How bout marvel mod 2
 
just42dave":2c684sgk said:
I wwould like the marvel mod can I put it on the classic?? How bout marvel mod 2
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Yes, You can put all those mods, including Marvel Mod, on the Classic as well. Write to Marvel to get it, You may find his email in one of the above posts.

Regards, Andy :)
 
Hi,

Sorry if I missed someone's email.

I've got literally TWO mod boards left. So rcm78 and just42dave please PM me to confirm you're still interested.

There'll be a new batch of mod boards in September. With more options and probably a trimmer, so you can dial in exactly what works best for ya. The funny thing is that the "XTC mod" works equally well in most other amps. Setneck has already mentioned his Marshall 6100. But there're hundreds of others. Splawn QuickRod has this kind of mod accessible from the front panel, and probably footswitchable, called Gear 3.

I also asked Setneck to take care of the orders and shipping for the new batch of mods, so that the customer service is superb and shipping is fast. :rock:

Regards, Marcin
 
Marvel":39x01bs9 said:
The funny thing is that the "XTC mod" works equally well in most other amps. Setneck has already mentioned his Marshall 6100. But there're hundreds of others. Splawn QuickRod has this kind of mod accessible from the front panel, and probably footswitchable, called Gear 3.
Click to expand...
Indeed that kind of mod can be used in nearly every amp as it works the same way in all of them: it bypasses cathode resistor for more gain and/or for tone shaping in particular way. The thing is what kind of mod do You need as there are two kinds of them: cap only or cap+resistor combo. In that combo the point is that You change cathode bias point. The lower the value the more gain You get. You can read about that here: http://www.diystompboxes.com/pedals/tubedummy.html.

The best thing in those mods is that You can keep stock tone of Your amp and also add two (or more) other options for tone shaping at the same time. So You don't loose anything, only earn more :).

My newest idea as for the Structure switch is to install a 6-way switch instead of C2 tantalum cap which bypass the V2A cathode resistor and solder 6 different caps to it.
FYI, in my amp C2 is 1.5uF and not 2.2uF as it is marked on schems floating thru the net. Maybe Bogner used to use 2.2uF cap but now they use 1.5uF and that value is confirmed by Charlie from Bogner. I like 1uF here very much, 0.68uF is also interesting. I wait for 0.82uF caps to try.
Tried 0.22uF, 0.33uF and 0.47uF, they seem to be somewhat useful in studio, for recording solos for example. For gigging - 1uF seem to be the point for me.

As for the Marvel R12 Mod - tried many many options here. The point to start for me was Factory 2004 Mod, which contains 2.7K in series with 0.22uF cap. You may also use 0.1uF, 0.33uF and 0.47uF caps here, every of them sounds nice in its own way. Those caps increase gain mainly in upper frequencies (what is pretty obvious). The main point here is to find a right resistor for the combo and to decide, if You solder them in series (like in Factory Mod) or in parallel (like in Structure circuit). Both aplications sounds obviously different.

I haven't decide yet what values I will use here. The cap and the trimmer (so variable resistor) seem to be perfect choice though.

Regards, Andy :)
 
What about a switch(mods) for the Uberschall (Rev Blue)? Tweaks and options are always fun if you can go back to stock.
 
Sounds acceptable. I approved to acquaintance you about purchasing your marval mod. Do you still advertise it
 
SLOgriff":3812kvnf said:
What about a switch(mods) for the Uberschall (Rev Blue)? Tweaks and options are always fun if you can go back to stock.
Click to expand...

I am not too familiar with Uber circuit but those mods actually works the same way in every amp - it bypasses the cathode resistor of particular gain stage with a cap. I will have same mods in my Marshall 6100. So I am sure You might use it in Uber as well, the thing is to find a right cap value for the mod.

Regards, Andy :)
 
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