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Author Topic: Ampeg Scrambler clone problem  (Read 3320 times)

LJN

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Ampeg Scrambler clone problem
« on: October 02, 2015, 04:41:39 PM »
Hello. I have a question regarding the ampeg scrambler circuit. I built one a while back and it has had many problems, most of which have been solved. The problem I'm having now is the overall smoothness of the effect . The ring modulation and octave up are there, but the overall tone is dark and the fuzz is weak. I've been running it through my Kasino u100-p amplifier , which all my other fuzzes sound great with. Has anyone else had similar problems with this circuit? What can I do to get this thing sounding as it should?
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Enzo

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Re: Ampeg Scrambler clone problem
« Reply #1 on: October 02, 2015, 09:17:57 PM »
You could start by providing a schematic of what you built.

LJN

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Re: Ampeg Scrambler clone problem
« Reply #2 on: October 02, 2015, 10:16:59 PM »
I don't have any way of posting a schematic . I don't even remember the numbers on the transistors I used. I just measured a bunch and used the ones that had the highest gain. Q3 and Q4 are over 500 (Q3), and over 300(Q4). They're not darlingtons, but from the parts I had they had the highest gain.
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Enzo

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Re: Ampeg Scrambler clone problem
« Reply #3 on: October 03, 2015, 08:41:37 AM »
OK then, I will see if I can find one.  But without a schematic, we have no idea what Q3 or Q4 might be doing, where they are in a circuit, or anything else.

teemuk

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Re: Ampeg Scrambler clone problem
« Reply #4 on: October 03, 2015, 11:27:47 AM »


Final part of the full-wave rectifier made out of two forward biased half wave recitifiers (the diodes) and a differential amp (Q3 & Q4).

I think the point of that BJT differential is that it operates less ideally than a traditional FWR and somewhat "smoothens" the transitional region to cutoff state. If a sinusoidal input is fed to traditional FWR you get a "pulsating" output (IOW rectified sine wave) at 2x input frequency (IOW an "octave up" effect). When you feed the sinusoidal input to this circuit it tends distorts so much near the cutoff state that the output resembles more a sinusoidal wave (at 2x input frequency) than a traditional rectified sinusoidal wave.

LJN

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Re: Ampeg Scrambler clone problem
« Reply #5 on: November 29, 2015, 06:27:02 AM »


Final part of the full-wave rectifier made out of two forward biased half wave recitifiers (the diodes) and a differential amp (Q3 & Q4).

I think the point of that BJT differential is that it operates less ideally than a traditional FWR and somewhat "smoothens" the transitional region to cutoff state. If a sinusoidal input is fed to traditional FWR you get a "pulsating" output (IOW rectified sine wave) at 2x input frequency (IOW an "octave up" effect). When you feed the sinusoidal input to this circuit it tends distorts so much near the cutoff state that the output resembles more a sinusoidal wave (at 2x input frequency) than a traditional rectified sinusoidal wave.
Thanks for the explanation,  but I really don't understand what that means. Is the effect supposed to be smooth sounding?
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

phatt

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Re: Ampeg Scrambler clone problem
« Reply #6 on: November 30, 2015, 12:49:18 AM »
I have never been close enough to even smell this particular circuit but generally these analog octave generators are FAR from smooth. Usually it's a hard edgy sound and likely needs a mix of a few pedals to make it work like you want.
Long ago I did build a couple of Tychobrahe pedals and they needed perfect balance drive of the 2 diodes before you got a decent sound, well relatively smooth at best. :-X

Kenny W Shepard example in a song called Blue on Black where I believe he used 2 TS9's and the octave pedal to get it to sound sweet.

Also keep in mind these analog octave circuits tend to only really start to work on higher notes, lower notes it's less pronounced. The digi stuff is likely better in that regard.
Phil.

LJN

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Re: Ampeg Scrambler clone problem
« Reply #7 on: November 30, 2015, 08:18:02 AM »
Thanks. Maybe the problem is the diodes I used,  then. I don't know what they are. I just found some and threw' em in there.  My problem with it is that it sounds too smooth and dark. Sure, the ring modulation is strong and the octave- up effect is there, but where's the insane sounding fuzz that this circuit is so famous for?
« Last Edit: December 01, 2015, 12:47:13 AM by LJN »
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Ampeg Scrambler clone problem
« Reply #8 on: January 15, 2016, 04:18:56 PM »
Hi, everyone. I ended up ordering some 2N5306 transistors and 1N34A diodes for my clone. I completely rebuilt it and it sounds much better now, although it's still kind of smooth. I guess it's just supposed to sound this way. Thanks.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

 

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