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PostPosted: Sat Jan 24, 2015 2:37 am 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
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Location: Tucson, AZ
Regarding the 100 ohm resistors under the cathode bypass cap:

The resistor alters the gain of the stage. The DC voltage "sees" 1.8k and 100 in parallel = 94 ohms. Gain boost is reduced from a circuit with 1.8k and 1uf to ground.

The resistor also alters the corner frequency for the gain boost. AC voltage "sees" 1.8k and 100 in series to the cap. The gain boost affects frequencies over 83.8 Hz (vs 88.4 without it).

It's called a cathode boost limiting resistor, IIRC. In this case, removing the 100 ohms would alter the gain boost much more than the corner frequency.

My personal opinion would be to leave the one on stage 1 alone if you want a clean sound that's clean. Since the tone stack follows it, the treble, presence, and gain controls for CH1 should cause breakup and overtones much earlier than the stock setting, were it removed.

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PostPosted: Sat Jan 24, 2015 2:47 am 
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Mark III
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I cannot believe I was such a slacker I never got around to uploading a recording.

This is a scratch track I made for my drummer to lay his tracks down to. Forgive the beep as It is hard coded in the mp3 for him.

https://soundcloud.com/lasanche/hell-correct

We did this a few weeks back. Running my Ibanez DT-250 into my Dual with mods I made from this thread. No changes to the amp since I last posted. I think I was actually running the Orange channel for this recording.

Amp settings Pres: 11:00, Master: 1:30, Gain: 11:30
Bass: 12:00, Mid: 1:00, Treble: 4:00

Guitar has single volume, no tone control, Dimarzio Megadrive pickup.

In September I had decided to stop down tuning to B which we had been using since 2013. I had grown tired of trying to figure out how the guitars and bass can play nice with each other at that tuning. After listening to all the stuff I loved when I was growing up. the music that really moved me and made me want to play this style and after listening to my holy grail heavy tune Slowly We Rot and finding out it is in standard tuning, I tuned back up to standard tuning. That doesn't fit my voice so we dropped it down a half step, now all guitars have their space. My bassist has even started using distortion on his bass, which I had always hated before, but it actually compliments the guitars right now.

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PostPosted: Mon Jan 26, 2015 2:48 pm 
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Mark II

Joined: Sun Sep 30, 2012 4:40 pm
Posts: 134
Location: Finland
I finally got around to make some clips of my modified Multi-Watt DR.

nearly two years ago I made the following changes: 1) jumped the 100 ohm resistors 2) added 5M5ohm Resistor in parallel to the 680k resistor in the first filter section to drop the total resistance to Rev C/D values.

Here you can find link to the clips:

http://www.tonefinder.com/index.php?section=user&value=shemham

Basically I recorded two clips in Vintage and Modern modes practically everything set towards noon. Then I made one fine tuning to Modern settings and used my standard settings for another Vintage clip. I tried to make the clips very plain to demonstrate the actual tone and texture of the modified amp. I use a clean boost to bring my guitar signal to moderate levels as I'm using fairly low output pickups. Anyway, you can find most of my settings and gear used behind the link.


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PostPosted: Tue Jan 27, 2015 3:00 pm 
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Mark III

Joined: Sat Jul 01, 2006 1:23 pm
Posts: 264
Shemham wrote:
I finally got around to make some clips of my modified Multi-Watt DR.

2) added 5M5ohm Resistor in parallel to the 680k resistor in the first filter section to drop the total resistance to Rev C/D values.



Hi,
What does this do to the sound/feel of the amp?

I've done the 100 ohm resister jumpers, that made the amp more present.


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PostPosted: Tue Jan 27, 2015 9:44 pm 
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Mark IV

Joined: Thu Aug 15, 2013 12:20 am
Posts: 656
Location: Tucson, AZ
Shemham wrote:
I finally got around to make some clips of my modified Multi-Watt DR.

nearly two years ago I made the following changes: 1) jumped the 100 ohm resistors 2) added 5M5ohm Resistor in parallel to the 680k resistor in the first filter section to drop the total resistance to Rev C/D values.

Here you can find link to the clips:

http://www.tonefinder.com/index.php?section=user&value=shemham

Basically I recorded two clips in Vintage and Modern modes practically everything set towards noon. Then I made one fine tuning to Modern settings and used my standard settings for another Vintage clip. I tried to make the clips very plain to demonstrate the actual tone and texture of the modified amp. I use a clean boost to bring my guitar signal to moderate levels as I'm using fairly low output pickups. Anyway, you can find most of my settings and gear used behind the link.


I really like the tube/modern one. The other one is really good, too. All of the dirt channel recordings sound good.

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PostPosted: Wed Jan 28, 2015 7:37 am 
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Mark III
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Joined: Mon Apr 05, 2010 12:28 pm
Posts: 414
Shemham wrote:


Wow, that sounds good. Especially the 50W channel 2 Vintage sound, awesome tightness, it's pure hot-rodded Marshall from hell! :twisted: The 100W samples aren't bad either, just a little mushier.

The samples are pretty close to what my C sounds like, esp. the tightness of the 50W sample. The main audible difference I can discern is the different top-end character - the highs of your modded Rec sound more saturated, or somewhat "wetter" (for the lack of a better word). I guess the different transformer might play a role in this. But otherwise, it (again, especially the 50W sample) is very close. You can consider your mods a success - and I believe that the EL34s help also in the tightness department.


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PostPosted: Thu Jan 29, 2015 10:18 am 
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Mark II

Joined: Sun Sep 30, 2012 4:40 pm
Posts: 134
Location: Finland
Thanks for the comments.
kramerxxx wrote:
Hi,
What does this do to the sound/feel of the amp?

I've done the 100 ohm resister jumpers, that made the amp more present.

Installing the 5M5ohm resistor parallel to the 680Kohm resistor equals to removing the 2M2ohm/82pf circuit and replacing the 680Kohm with a 470Kohm resistor except it does not influence Raw mode at all. 82pf cap is so small that it should be insignificant with the 0.0022uf cap there.

Tone/feel wise the change is quite subtle. I get more gain, with more mids and lows. In other words, it makes the tone a bit fuller and I find it useful for leads. It's still something pretty minor. If you have changed the gain pot value, that will yield much bigger change and makes the change even less noticable. I didn't like the higher value gain pot and deciced to stick with standard Rev C/D specs.

Alternative method is to change the 2M2ohm resistor with a 1M5ohm which will give same resistance as Rev C/D in Vintage and Modern modes while adding more gain to Raw mode.

LesPaul70 wrote:
Wow, that sounds good. Especially the 50W channel 2 Vintage sound, awesome tightness, it's pure hot-rodded Marshall from hell! :twisted: The 100W samples aren't bad either, just a little mushier.

The samples are pretty close to what my C sounds like, esp. the tightness of the 50W sample. The main audible difference I can discern is the different top-end character - the highs of your modded Rec sound more saturated, or somewhat "wetter" (for the lack of a better word). I guess the different transformer might play a role in this. But otherwise, it (again, especially the 50W sample) is very close. You can consider your mods a success - and I believe that the EL34s help also in the tightness department.

Haha! Thanks. Yeah, it's kinda Marshallesque. It's what I use for both my rhythm and leads normally.

I actually tried 250kohm presence pot with Modern mode once. It (at least seemingly) tightened the lowend even further as you're likely to dial your presence higher, but that was way overkill and made the mode a bit too brittle IMO. But yeah, some of the differences with the highs might be related to different output transformer, although you already confirmed that Rev G does not sound like Rev F through Rev C's power section so there's likely something else going on with Rev F's preamp.


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PostPosted: Thu Jan 29, 2015 5:00 pm 
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Mark IV

Joined: Wed Apr 28, 2010 6:33 am
Posts: 730
Location: Chicago, IL
Shemham wrote:
I finally got around to make some clips of my modified Multi-Watt DR.

nearly two years ago I made the following changes: 1) jumped the 100 ohm resistors 2) added 5M5ohm Resistor in parallel to the 680k resistor in the first filter section to drop the total resistance to Rev C/D values.

Here you can find link to the clips:

http://www.tonefinder.com/index.php?section=user&value=shemham

bjorn218 wrote:
I cannot believe I was such a slacker I never got around to uploading a recording.

This is a scratch track I made for my drummer to lay his tracks down to. Forgive the beep as It is hard coded in the mp3 for him.

https://soundcloud.com/lasanche/hell-correct


That sounds really good guys!

These clips are pretty much nailing the tone on Rev C clip:

https://dl.dropboxusercontent.com/u/473 ... 00-6L6.mp3

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PostPosted: Sat Jan 31, 2015 10:00 am 
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Bottle Rocket

Joined: Sat Jan 31, 2015 9:55 am
Posts: 1
JCDenton6 wrote:

That sounds really good guys!

These clips are pretty much nailing the tone on Rev C clip:

https://dl.dropboxusercontent.com/u/473 ... 00-6L6.mp3


wow - awesome tone.
what amp version do you use, and what mods have you done?
as far as I have read here in this board, you have tried some different mods. so - which mods are responsible for this tone?


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PostPosted: Sun Feb 01, 2015 3:10 am 
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Mark IV

Joined: Wed Apr 28, 2010 6:33 am
Posts: 730
Location: Chicago, IL
Thanks, I'll PM the mods to you.

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PostPosted: Fri Apr 10, 2015 3:56 pm 
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Mark IV

Joined: Wed Apr 28, 2010 6:33 am
Posts: 730
Location: Chicago, IL
I found more anomalies that I have previously overlooked: R503(?) and R361-R362(100 ohm) , which I didn't find on the schematics and is soldered in Rev C, D, E, F and up into the early serials of Rev G.

I didn't see this on later Rev G's...

Might have to download for full size pics.

Rev C: https://www.dropbox.com/s/hglqdm9uiiek2 ... 4.jpg?dl=0
https://www.dropbox.com/s/1eglwvt1py492 ... 4.jpg?dl=0

Early Rev G: https://www.dropbox.com/s/yr7ozypwv6bdv ... 3.jpg?dl=0

My Rev G Triple without R503 and R361-R362: https://www.dropbox.com/s/ixsx9v8x9xefq ... 3.JPG?dl=0
https://www.dropbox.com/s/z12xmcnqe8ddn ... 7.JPG?dl=0

EDIT: Finally found the full 2 ch schematic, So apparently R503 is a 220 ohm 5w wire round resistor that was used in the LDR power supply in early models.
R361-R362: They were used to reduce hum when the tap off of the PT was soldered in a different place in the older amps, the Rev G's setup like mine have a tap running of the PT and is soldered right before the LDR power supply, nothing to do with tonality.

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PostPosted: Sat May 23, 2015 10:34 am 
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Bottle Rocket

Joined: Thu Apr 10, 2014 3:26 am
Posts: 3
I've revamped the Lasse & Mago DI after the pre 500 mod. Sounds Huge in my opinion. What do you think? https://www.youtube.com/watch?v=yi7Gwa7PosA


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PostPosted: Sat May 23, 2015 10:53 pm 
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Mark IV

Joined: Wed Apr 28, 2010 6:33 am
Posts: 730
Location: Chicago, IL
It sounds great, you can hear the characteristics of the pre 500 rectos in the clip.

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PostPosted: Sun May 24, 2015 2:07 pm 
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Mark II

Joined: Sun Sep 30, 2012 4:40 pm
Posts: 134
Location: Finland
Yeah, that does sound huge no question. I'd still like to hear the amp without the OD-808 slamming the front end.


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PostPosted: Wed May 27, 2015 11:33 am 
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Mark II

Joined: Fri Oct 24, 2008 5:03 am
Posts: 59
Location: Czechoslowakia
hey guys...I just recorded another short clip of my modded recto...

https://soundcloud.com/wolfernus/sd-liv ... recto-test

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