Replacing BSIAB Tone Stack with Tonemender?

punkin · April 18, 2009, 08:29:16 PM

Hello once again one and all.

I have built a BSIAB2 and a Tonemender. I'm looking to integrate them into a single package rather than seperate effects boxes. I've been running jumper wires between the two circuits for the last couple hours and I'm not having much luck.

I've used the two schematics below.

Seems that C9 in the BSIAB2 is a DC blocking cap so I thought I'd simply leave that in and insert the Tonemender right behind it. The 10M Ohm resistor, 22nF cap and the 1M Ohm resistor appear to be impedance matching and coupling for the OP Amp so I thought to leave those in place. I then reused my level control pot from the BSIAB at the output of the Tonemender. Is my thinking on track or am I missing something?

slideman82 · April 18, 2009, 08:47:25 PM

I think you're going right, but place a vol pot after the BSIAB as it is, and take out the 10M, and place a master volume, so you can rise the BSIAB vol and listen if it's clipping rightly, if you overload the IC's and make them clip, it will loose that great sound the BSIAB is characterised with... well, that's my opinion!

punkin · April 18, 2009, 08:56:10 PM

Thanks a bunch for the reply. Gives me a few things to think about. I see what you mean by overloading the input of the OP amp.

aziltz · April 18, 2009, 09:04:53 PM

Quote from: slideman82 on April 18, 2009, 08:47:25 PM
I think you're going right, but place a vol pot after the BSIAB as it is, and take out the 10M, and place a master volume, so you can rise the BSIAB vol and listen if it's clipping rightly, if you overload the IC's and make them clip, it will loose that great sound the BSIAB is characterised with... well, that's my opinion!

sounds like good advice.

problems you may run into here is that the BSIAB Tone Stack is Passive. That is, it only cuts, so you can run anything into it. The Tone Mender is Active, it has rails involved and if you hit it too hard you will cause unwanted clipping.

punkin · April 18, 2009, 09:13:09 PM

I wonder then if I should put a fixed resistor or a trimmer pot between the BSIAB and the Tonemender. Match the level so that it doesn't get over driven then put a final output control at the end of the circuit? Again, thanks for the replies.

aziltz · April 18, 2009, 09:15:55 PM

Quote from: punkin on April 18, 2009, 09:13:09 PM
I wonder then if I should put a fixed resistor or a trimmer pot between the BSIAB and the Tonemender. Match the level so that it doesn't get over driven then put a final output control at the end of the circuit? Again, thanks for the replies.

thats exactly what I would do, but make sure it doesn't change any filters between the stages. Test it on breadboard first.

slideman82 · April 18, 2009, 09:24:13 PM

Right, a trimpot will do the trick, so you leave it just before clipping... if you listen to some "fuzzy" or a bit ugly distortion is because the op amps are clipping, and op amp clipping isn't good sounding at all... that would make the BISAB loose it's magic...

Try it and let us know how does it sound!

aziltz · April 18, 2009, 09:26:33 PM

i just had a thought.

the first tone mender op amp is a buffer, you could drop that and just attach everything after that opamp where the BSIAB tone stack was. The second op-amp is make-up gain, which you can use for master volume.

punkin · April 18, 2009, 09:26:56 PM

Going to break out the o-scope. Unfortunately I'm not on a breadboard. I've already built the circuits on perf but I'll wire something up this eve.

punkin · April 18, 2009, 09:27:52 PM

oh...ok...I gotcha. That would simplify things a bit.

slideman82 · April 18, 2009, 09:43:02 PM

That's great! Just leave out that buffer... great idea!

slideman82 · April 18, 2009, 09:50:46 PM

Mmmm I dont like that 500k gain pot at the end... could be a 22k resistor, perhaps... so op amp doesn't clip by itself! Also I would change the 47p cap for a 1n cap so you keep the frecuency response...

punkin · April 18, 2009, 09:58:41 PM

Not sure I follow you there Slideman. I'm thinking I do need a volume control. I was thinking of pulling it out of the BSIAB circuit then putting it at the very end of the Tonemender. When you say 22k resistor...are you saying put that between the BSIAB and the input to the buffer stage of the Tonemender?

I am hip to the cap change out...would like to keep things transparent between the stages.

Bucksears · May 08, 2009, 01:58:33 PM

Has this gotten worked out? I'm itching to try the tonemender in place of the BSIAB II tonestack, but if it's going to be difficult to workaround......

waltk · May 08, 2009, 08:55:38 PM

Bump.
I'd like to do this too. Did it work out? If so, can you give details?

I once thought I would put a mashal tone stack at the end of a BSIAB, and was told it probably wouldn't work (being a passive stack that would attenuate too much). It was suggested that maybe the tone stack should put between the gain stages on the BSIAB, but I didn't follow through and do it.

A related question... the first circuit I ever etched and built was a tonemender (from the PCB layout on ROG). It had a loud hum problem in testing (unmounted). I eventually made it work (without all the noise) by adding a more direct ground wire. I figured it might have been poor soldering technique, or just some other beginner's mistake. I recently started from scratch and built a second one - but it had the same problem. Has anyone else seen this (or have any suggestions about how to solve it)? The power supply was very clean - from an LM317.

punkin · May 08, 2009, 11:06:46 PM

Sorry, no...I never managed to get satisfactory results with the blending of these two circuits. I had level attenuation or noise and other issues. I ultimately became frustrated with this and decided that the BSIAB II sounded great just the way it is. Why mess with a good thing right? I was hoping to add an "optional" tone stack switch but the level changes and noises just turned me off from the experiment. I just wanted to play this thing so I boxed it up and called it good.

slideman82 · May 08, 2009, 11:57:03 PM

Are you using just J201? They are too gainny...

Bucksears · May 09, 2009, 03:17:57 PM

Thanks - I think the main thing for me is the mids.
I'll look at Jack's AMZ Presence control some more, or just swap out R8 for a (150k or higher) pot and how it goes. I'm ok with the highs and could use a little more bass, but the midrange is the most important to me in this circuit.

punkin · May 09, 2009, 03:25:50 PM

I am using all J201's. Frankly I really like the sound of them...I've tried low gain tranny's but came back to the original design. I like that string "ping" I get when the trebble in the amp is turned up. I too was hoping for a little more base and mid-scoop control but again, the BSIAB sounds great to me in it's pure form. Perhaps on my next one I'll have more patience for modding. I was just really anxious to finish it up get it into a box and play with it.

If anyone else here as successfully added a different tone stack to their BSIAB, I'd be very interested in seeing their schematics.

Peace

Ben N · May 10, 2009, 02:21:52 AM

A little late, I know... I would leave out the opamp altogether: Just rewire the last FET in the BSIAB as a source follower, then follow it with the TM stack and a master volume. If there is too much signal lost this way, add a simple recovery stage, either another JFET or, better, a BJT like an LPB or the last stage of a Muff. I don't see how the opamp really makes a lot of sense in this context. Remember, the Tonemender is just a very flexible passive tone stack sandwiched between an input puffer and a recovery amp, in a configuration that makes a lot of sense for a stand-alone eq box.

News:

Replacing BSIAB Tone Stack with Tonemender?