DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: gigimarga on November 18, 2008, 06:42:07 PM

Title: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 18, 2008, 06:42:07 PM
Hello,

I am a big fan of envelope followers.
First, i borrowed from a friend a cheap Ibanez Soundtank Autowah. It sounded very interesting to my ears (even with his poor quality sound), so i'd built a Nurse Quacky which i'd liked very much (the effect, of course :) ).
After that i built a improved MXR EF 440.
Both of them (Nurse and MXR) was exchanged and, after all, i bought an older EHX Q-Tron which sounds amazing...i spent few hours every day for almost a week to play with it and i think i have much more to discover.

After a long struggle i finished a Maestro FSH which remains No.1 in my stompboxes top!

Last week i built a hard modded EHX Bassballs (thx Mark Hammer again...) which i like very much, too.

So, my questions are:

1. It is possible to simulate the EHX Bassballs using Q-Tron (my pedalboard have 210 x 80 cm and it's full!!!)?

2. It is possible to modify the EHX Q-Tron to obtain a distortion/fuzz which has the amount of distortion controlled by the force of picking (my beloved dream...like Boss DN-2, but analog)?

3. Is there any others stompboxes of this type which sounds different from what i have (like Mutron, Brassmaster, etc.) which i deserve to build?

Thx a lot!
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Unbeliever on November 18, 2008, 09:42:43 PM
1. It is possible to simulate the EHX Bassballs using Q-Tron (my pedalboard have 210 x 80 cm and it's full!!!)?

Depends, how picky are you about the accuracy of a 'simulation'?  :) The Bassballs and Qtron have different filter topologies, and in fact different number of filters (two in parallel that can be tuned to different frequencies vs one), so the answer here is no, realistically speaking.

Quote
2. It is possible to modify the EHX Q-Tron to obtain a distortion/fuzz which has the amount of distortion controlled by the force of picking (my beloved dream...like Boss DN-2, but analog)?

Yes, if you are happy with a fuzz-sound that would be similar to that obtained via the Bassballs; you need to take a tap from the FWR circuit. I think EH schematics are banned from here, so I can't give you more details.

Quote
3. Is there any others stompboxes of this type which sounds different from what i have (like Mutron, Brassmaster, etc.) which i deserve to build?

If you have a Q-tron, I wouldn't bother building a Mutron III clone. The Q-tron is an improved MutronIII, and has the same filter arrangement (state variable) and hence a very, very similar sound.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 19, 2008, 12:45:15 AM
Thx a lot Unbeliever!

I tried a little to simulate the Bassballs using the Q-Tron and i had no good result, but now i have the confirmation.
Anyway, it's possible to add another filter to Bassballs? How it will sound?

If you want to help me to obtain the fuzz from the Q-Tron i can send the schematic to you on the email (if you want).

Thx a lot again!
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Unbeliever on November 19, 2008, 01:21:02 AM
I tried a little to simulate the Bassballs using the Q-Tron and i had no good result, but now i have the confirmation.
Anyway, it's possible to add another filter to Bassballs?
Sure, you can just duplicate the circuitry that is there for one filter section already. The two caps determine the base frequency.

Quote
How it will sound?
Try it and let us know. It might be a good example of the law of diminishing returns... three 'balls' may not offer significantly more performance than two.  ;)

Quote
If you want to help me to obtain the fuzz from the Q-Tron i can send the schematic to you on the email (if you want).
Try tapping off the signal at the junction of R29, D2 and R31 - you'll want to use a DC blocking Cap (eg 100N), and depending on level you might wave to add a pot as a volume control. Feed all of this via a 4k7 resistor into Pin 3 of U4A (if you want the distortion to go via the filter). This is just from a quick look at the schematic (which I have, thanks), some trial and error with signal feed points and destinations should give interesting results.

Please post back what you find out.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: B Tremblay on November 19, 2008, 07:35:50 AM
Are you using guitar or bass with the Bassballs?
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Mark Hammer on November 19, 2008, 09:46:26 AM
The Bassballs has two unique traits.  First, the attack time is very short; short enough that you mostly hear the decay portion so it seems to only sweep downward.  Second, the peaks of the two filter sections are staggered apart in a characteristic way.  On the builds where I can tune both filters, many of the settings reslt i sounds which do not sound at all like a Bassballs.  Good sounds, but not THAT sound.  Perhaps it would be possible to mimic the Bassballs with the rackmount Bi-Filter, but just about every other commercial floorpedal I know of uses a single filter with a single resonant centre or corner frequency.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 19, 2008, 10:13:14 AM
Are you using guitar or bass with the Bassballs?

Thx a lot! I use Bassballs with a Squier Affinity guitar (not a bass).
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 19, 2008, 10:17:57 AM
The Bassballs has two unique traits.  First, the attack time is very short; short enough that you mostly hear the decay portion so it seems to only sweep downward.  Second, the peaks of the two filter sections are staggered apart in a characteristic way.  On the builds where I can tune both filters, many of the settings reslt i sounds which do not sound at all like a Bassballs.  Good sounds, but not THAT sound.  Perhaps it would be possible to mimic the Bassballs with the rackmount Bi-Filter, but just about every other commercial floorpedal I know of uses a single filter with a single resonant centre or corner frequency.

Thx a lot again Mark! It's very clear now!

What about a BOSS AW-2? It's interesting?
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: DougH on November 19, 2008, 10:24:55 AM
This is a great article on envelope followers in general: http://www.geofex.com/Article_Folders/ECFtech/ecftech.htm (http://www.geofex.com/Article_Folders/ECFtech/ecftech.htm)
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Mark Hammer on November 19, 2008, 10:52:34 AM
Pretty good article, but I hear from reputable sources that the guy who wrote it is a class A putz. :icon_wink:

This article, while older, is a little more authoritative. http://www.elliott-randall.com/ecf.htm
This makes a good read too: http://www.beigeltech.com/articles/vintage/vintage1.html
Finally, this one looks real interesting too: http://www.beigeltech.com/articles/ics/ics1.html
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: B Tremblay on November 19, 2008, 02:06:25 PM
Pretty good article, but I hear from reputable sources that the guy who wrote it is a class A putz. :icon_wink:

Well, everybody knows that class A is where the mojo resides...

Over the summer, I spent some time with the Bassballs circuit.  Here's a schematic of the minor mods I made:
(http://runoffgroove.com/images/attachments/bb.png)

First, I jettisoned the fuzz mode.  Then I added the resonance switch, which changes the filters to true twin-Ts for more pronounced peaks.  Finally, I added the filter blend pot at the filters' outputs.

Thanks to Topopiccione for its Bassballs page.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Mark Hammer on November 19, 2008, 03:12:28 PM
Funny, I pretty much jettisoned the clean mode on some builds. :icon_lol:

That resonance mod looks very interesting, especially since it only involves a toggle.

I would strongly encourage you to explore varying the 330k decay resistor.  Faster decays make the effect sound much more synth-like.  That, and greater resonance could make a nice one-two punch.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: B Tremblay on November 19, 2008, 05:06:29 PM
I would strongly encourage you to explore varying the 330k decay resistor.  Faster decays make the effect sound much more synth-like.  That, and greater resonance could make a nice one-two punch.

I toyed with different values for the 4u7 cap, but didn't consider the resistor.  I'll definitely explore that option, though instant gratification tinkering isn't much of an option during this time of year.  Sure, I can build a fire in the shop, but I much prefer being able to scoot out there whenever inspiration hits.

Can you please keep some of that frigid air in Canada where it belongs, Mr. Prime Minister?  At the very least, some of that lake-effect nonsense?
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Mark Hammer on November 19, 2008, 07:05:56 PM
I work 3 blocks from Parliament Hill. I'll trot over lunch-time tomorrow and see what I can do.  Not making any promises, though. :icon_wink:
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: orangetones on November 19, 2008, 07:14:23 PM
Hey Mark, This is off topic, but I live here in Ottawa too!  /Neato!
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 20, 2008, 12:46:27 AM

Well, everybody knows that class A is where the mojo resides...

Over the summer, I spent some time with the Bassballs circuit.  Here's a schematic of the minor mods I made:
(http://runoffgroove.com/images/attachments/bb.png)

First, I jettisoned the fuzz mode.  Then I added the resonance switch, which changes the filters to true twin-Ts for more pronounced peaks.  Finally, I added the filter blend pot at the filters' outputs.

Thanks to Topopiccione for its Bassballs page.

Thx a lot all again!

I used the filter blend pot as you described and sounds very good. I still keep the fuzz mode because i like it :)
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: earthtonesaudio on November 20, 2008, 02:41:36 PM
I was working on a similar filter design to the one B Tremblay posted (dual parallel twin T filters) a while ago and found that BS170s gave less distortion and more range than any of the BJTs I tried.  You might want to swap some FETs in there to see if you like the sound.

Note: One big difference, I was driving the FETs with a PWM, not a control voltage.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Celadine on November 20, 2008, 10:47:13 PM
Heres a page about modding a BassBalls, schematics at bottom of page:

http://members.tripod.com/urekarm/synth/fuzzyballs.html (http://members.tripod.com/urekarm/synth/fuzzyballs.html)

 :D
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 21, 2008, 10:44:31 AM
Heres a page about modding a BassBalls, schematics at bottom of page:

http://members.tripod.com/urekarm/synth/fuzzyballs.html (http://members.tripod.com/urekarm/synth/fuzzyballs.html)

 :D

Thx Celadine...i know the schematic, but i think it's too complicated... ::)
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: StephenGiles on November 21, 2008, 01:26:49 PM
Ripple!!
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: Mark Hammer on November 21, 2008, 02:07:26 PM
Um, are you refering to the rectifier, or is this just some outburst about cheap wine, such as Father Jack Hackett might yell as a non sequitor?
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: B Tremblay on November 21, 2008, 02:53:43 PM
Either meaning is still relevant.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: RickL on November 22, 2008, 08:44:06 PM
Quote
It might be a good example of the law of diminishing returns... three 'balls' may not offer significantly more performance than two.

I built a  'four ball' BB a couple of years ago, each filter with a different range (one above and one below the standard BB) and it was indeed a matter of diminishing returns. I built it with switches so I could pick from zero to four filters and I found in my experimentation that I most consistantly liked only two at a time. Three might be worth having but four was overkill.
Title: Re: Questions about Q-Tron and others envelope followers...
Post by: gigimarga on November 23, 2008, 12:24:08 PM
Thx a lot RickL!
I am happy not to try to modify it again :D