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Jason
Copper Member
USA
3 Posts |
 Posted - 04/02/2010 : 04:47:31
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Hey all,
I am a first timer on this board, but have been lurking for a few weeks.
I recently purchased a DS1 from MF and bought the kit to perform the Keeley SEM/Ultra MOD. I performed the mod and the sound was really nice with my ESP that has the Seymour Duncan Hot Rodded Humbucker set (SH4 and SH2), I could play as hard and loud as I wanted and it sounded fine. I then switched to my PRS Tremonti SE with the upgraded Tremonti Bridge and Neck pickups and with the volume and tone on 10 the pedal sounds like it was overloading, kinding of clipping out, but not good sounding. For example, if I played a G very loud it would sound like a limiter and get a "blarty" ( try looking that one up in webster's. :-) ) but this was more noticeable on the notes on the low E string. If I roll the volume back to about half it goes away and sounds fine, but then I am playing a little more weak. I do like playing with the volume rolled back, but like to crank it for leads and certain parts. I know these Tremonti pickups are really hot, on a scope, they were MUCH hotter than the Duncan's, but is that really the problem? THe pickups are adjusted right about even with the rings, so they are not too high.
I tried to revert the pedal back to stock just to check if it was something the mod was doing in combination with the pickups, and it does it to some degree on a stock pedal, and then by rolling the volume or tone back just a bit it is better.
NOTE: I should note that I run a Modded GCB95 Crybaby, TS808 Homebrew, Line 6 M13, DOD EQ, and Homebrew Boost into a JSX and have absolutely no problems with this guitar causing an issue.
My question: I am very comfortable working with electronics, however pedals and modding is new to me in the last year. I am wondering if there is someplace in the circuit that I could mod to attenuate the input somewhat, or if anyone has any idea what could cause this. I wouldn't think that these pickups are too hot for the pedal, but that is exactly how it acts. I haven't this problem on any other pedals, but this is honestly my first BOSS pedal, so I am not sure what to expect.
Thanks so much.. This is driving me nuts... SO I am hoping that someone might have some insight.
Jason
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/02/2010 : 12:55:31
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Hi Jason
Welcome to the forum from Australia.
Yes it sounds most definitely to be the very hot pickups.
You have to remember that when these early pedals were designed way back in the early 1980's nothing as hot as those pickups existed.
Do you have the Schematic/service notes for the DS-1?
There are many places on the web where you can find a copy.
But they will be of the earlier MIJ version.
There have been at least 5 or more variations of opamps that have been used in the DS-1.
Other than the opamps variations, there are very few differences in the various reincarnations of the DS-1.
Your MIT DS-1 probably uses M5218L SIP opamps.
If not please tell us which ones it has in it.
What we really need to know, is where the overload is actually occurring in the DS-1.
The input stage transistor of the DS-1 is emitter coupled.
Seeing you have a scope, can you probe the emitter & see if
the first stage is already being overloaded,
or if its the collector output of the Q2 in the second stage.
And it's nice to know you are a Tech minded Musician.
With test gear. 
Regards Dr. Bob  |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 04/02/2010 : 14:07:52
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I would try to reduce the pre-clipping gain of the BJT transistor based pre-amp around Q2.
You can achieve this by changing the value of C4 to something between 1 nF and 2.2 nF.
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Jason
Copper Member
USA
3 Posts |
Posted - 04/02/2010 : 15:27:09
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Thanks for the responses... They are much appreciated.
The op amp in the box is the M5223AL SIP, which I assume is the MIT box...
I was going to check today the signal running into the circuit and try to determine where it was overloading. I was running a 500mV p-p 1kHz sine wave through it the other day and was tinkering around with the clipping section at the output of the op amp, but this was when I thought it was working before noticing it wasn't. 
I will fool around with the input stage components and see if there is something I can change there. That is a good idea!
I tried to scour the lowly bowels of the Internet looking for something or someone that might have had a similar problem with these pickups or some other pickup, but didn't have any luck.
This seems like a great forum, so glad I have now joined.
Thanks..
Jason |
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gymnopedist
Copper Member
Indonesia
4 Posts |
Posted - 04/03/2010 : 04:28:31
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I got same problem too. I mod my DS-1 into Keeley ASE mod. I use Seymour Sh-8 Invader in bridge (Single PU). When I try the pedal, I found that the sound gets (yeah I like to say) over. The bass sounds cut off, the mid undefined & the treble is 'Too trebly'
I suspected this is because my Marshall micro amp. I thought my Marshall couldn't deliver the signal in this power. Once I get in to studio, I try my DS-1 to a 50W Guitar Tube amp. I thought I was right but I'm wrong. It sounded same too like in Marshall micro.
I've downloaded all video of Keeley DS-1 demo. It sounds fine. In Gibson (one of the video) it sounds great. I've checked my mod more than twice, I've searched the web about any info of keeley & my mod is right.
My conclusion, the pickup roles well in the keeley. |
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 04/03/2010 : 05:19:50
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| The DS-1 actually has a lot of places to gently reduce the gain, and compensate for hot humbuckers. Make R1 a 10K resistor, try making R9 a 100-ohm resistor, and try making R14 a 10K resistor. R1 increased to 10K and R9 increased to 100-ohms should alleviate your problem. Increasing R14 is almost a last resort. It should still sound like a DS-1. |
Edited by - ranjam on 04/04/2010 00:56:20 |
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Jason
Copper Member
USA
3 Posts |
Posted - 04/05/2010 : 13:35:41
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Hey all..
Thanks for the feedback. I will give it a try tonight to tweak a few resistor values and see what happens. The weekend got a little busy, but I will reply with what I find out for any others who may have a similar problem.
Thanks again...
Jason |
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Topic |
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DS-1 issues
