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DIY Stompboxes => Building your own stompbox => Topic started by: Renegadrian on June 24, 2020, 07:09:45 PM

Title: DOD 250 and active baxandall - help
Post by: Renegadrian on June 24, 2020, 07:09:45 PM
I'd like to build a dod 250 which will be used on bass (like in THIS (https://www.youtube.com/watch?v=yjQdVeEGxIA) video here), but also thinking about adding an active bax, like in the xotic ac/rc or similar pedals. Or the second part of the active baxandall HERE (https://www.parasitstudio.se/stripboard-layouts/active-baxandall-tonestack). Also saw the black hearts quantum mystic, using a quad to add an inverting stage, for what I see.
Do you guys think I can just add the active bax after the dod part, just after the diodes?! shall I change some caps to better go for bass!?
Title: Re: DOD 250 and active baxandall - help
Post by: bartimaeus on June 24, 2020, 07:45:26 PM
yes, you can just add it. throw together that layout and see how you like it! at worst, you swap a few wires and try it in different positions. maybe use sockets for the capacitors so you can try some different values.
Title: Re: DOD 250 and active baxandall - help
Post by: Renegadrian on July 03, 2020, 02:20:51 PM
ok done with testing...made a 250 with on/off/on switch for diodes and a switchable active bax.
without diodes, the tone part works quite decent, with diodes the bass pot works until mid run, then it cuts sound. I tried to tame input signal of the second part with a resistor, but that don't help.
Title: Re: DOD 250 and active baxandall - help
Post by: Renegadrian on July 03, 2020, 02:24:43 PM
(https://i.postimg.cc/xqPkK2ft/tonestack-sch.png) (https://postimg.cc/xqPkK2ft)
Title: Re: DOD 250 and active baxandall - help
Post by: antonis on July 03, 2020, 02:42:12 PM
Try a 1k series resistor right after pin 7..
Title: Re: DOD 250 and active baxandall - help
Post by: Renegadrian on July 03, 2020, 04:00:28 PM
Quote from: antonis on July 03, 2020, 02:42:12 PM
Try a 1k series resistor right after pin 7..

I wrote that I tried to tame input signal of the second part with a resistor, but that don't help.
actually it was a 10k just after the switch.before the two network resistors.
Title: Re: DOD 250 and active baxandall - help
Post by: antonis on July 03, 2020, 04:15:29 PM
I've got the nasty habit to read carefully what people write.. :icon_wink:

By placing resistor after diodes you get nothing 'cause op-amp's output is already loaded by diodes..
(10k is way high impedance seen by Bax..)
Title: Re: DOD 250 and active baxandall - help
Post by: POTL on July 03, 2020, 05:43:25 PM
I'm not sure this is a good idea.
I tried adding Baxandall to many of the popular overdrive and distortion pedals, but usually it didn't have very good results.
The fact is that in an increase in gain, the signal is distorted and the active equalizer starts to sound unpleasant, low frequencies add unnecessary subby and fuzzy, upper hiss and bite.
However, in clear sound, this equalizer sounds nice.
Perhaps with the bass, this equalizer will sound better than with a guitar, but I would try to raise the frequencies selectively, and not globally.
Look at the Friedman Buxom Boost and BE-OD circuits, they sound much better, because you are not raising a large spectrum, but only the desired frequencies.
In general, equalizers with a narrow and medium bandwidth will work much better.
I would make them asymmetric, for example, you raise the frequencies only by 5 dB and cut them by 10 dB.
Believe me, you do not need a lot of additional amplification of certain frequencies.
If the gain becomes too large, the sound loses its naturalness.
An example of poor design is often a large Wampler product.
Title: Re: DOD 250 and active baxandall - help
Post by: PRR on July 03, 2020, 10:54:23 PM
> the bass pot works until mid run, then it cuts sound.


(https://i.postimg.cc/tZNLSwZ8/tonestack-sch-w-Cap-42.gif) (https://postimg.cc/tZNLSwZ8)
Title: Re: DOD 250 and active baxandall - help
Post by: Renegadrian on July 05, 2020, 02:41:55 PM
wow that was it! That cap made it work perfectly!
DOD 250 is stock but input cap 100n and gain cap to ground 470n (large value means more bass, but it's nice even with a 100n). diodes on a on off on switch, asym 4148 and 2 red leds. nice iin all 3 positions.