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Dirk
Platinum Member
Netherlands
1309 Posts |
 Posted - 09/20/2008 : 20:18:05
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Well, somewhat...
I decided to mod my recently acquired HM-2, full story can be read on the bottom of this page:http://www.bossarea.com/forum/topic.asp?TOPIC_ID=4387&whichpage=16
Anyway, I didn't found it sounding very much like a Marshall amp as Boss claims, stock it has that shitty scooped, gained out Metalzone type of tone, but a little less extreme.
It was also very harsh sounding, somewhat resembling the dodgy Marshall 4210 amp I have (remember that one?).
Since my knowledge of basic electronics is very little, however I can read schematics, so I compared it to schems of modded DS-1's and my SD-1, I figured all distortion pedals or similar in a way.
I started swapping out diodes with others and played around with some capacitor values and the result is a pedal very similar to the crunch channel of my (good) Marshall jcm800 with all the tone controls set flat and max gain.
This is what I swapped, some of it may make no sense to you out there who's knowledge of electronics is greater than mine, but for me it seems to work.
D3, D4, D8 - change to 1N4002
D5 - change to AA119
C9 - change to 10nF
lastly I soldered a 100nF capacitor across pins 3 and 6, basically across the output pot to get rid of some of the harshness.
This really worked miracles, although there are some glitches.
There's less gain then before, and the last half of the gain control doesn't seem to add anymore gain.
Treble pot sounds fine till 10 o'clock, after that not only treble gets boosted, but also the overall volume ?? (beats me)
Even more surprising is the fact that when I turn the treble control fully counterclockwise, the scooped sound reappears, but a lot duller since there's not a lot of treble at this position.
Bass and level seem to function properly.
Maybe someone can explain what kind of monster I just created? 
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Edited by - Dirk on 09/20/2008 20:22:02 |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 09/20/2008 : 20:38:47
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The loss of gain can be explained with the type of diodes you have selected.
The originals are 1N4148's with a clipping threshold of approx. 0.63V
The AA119 and 1N4002 diodes have a clipping threshold of 0.3V and 0.55V, respectively.
Hence, overall you have reduced the output signal level. |
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Dirk
Platinum Member
Netherlands
1309 Posts |
Posted - 09/22/2008 : 19:03:58
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I see, thanks for the info cctsim.
It doesn't bother me much, since it sounds good now  |
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Ptak
Bronze Member
141 Posts |
Posted - 11/21/2009 : 03:30:06
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| Since the "smooth" mod failed with flying colours i have decided to try your mod dirk! I actually really want a Marshall JCM800 so im quite interested. Just wondering if youve updated your mod at all or if anyone would suggest better parts to fix the loss of gain. |
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Dirk
Platinum Member
Netherlands
1309 Posts |
Posted - 11/21/2009 : 10:29:35
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| Actually, I took the pedal back to original and sold it cause my JCM 800 sounds better and I didn't use it much. |
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Ptak
Bronze Member
141 Posts |
Posted - 11/22/2009 : 02:17:29
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| well no doubt the amps going to be 100% better but would you recommend this mod? what type of music does it sound best with? |
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Dirk
Platinum Member
Netherlands
1309 Posts |
Posted - 11/22/2009 : 10:31:50
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It actually came pretty close to the sound of my amp's overdrive channel.
I play all kinds of rock, hardrock, classic rock and it's perfect for that. For metal and solo's I turn on the BD-2 for some little boost. |
Edited by - Dirk on 11/22/2009 10:32:16 |
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Topic |
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HM-2 Rusty Metal Mod
