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 Forum index » DIY Hardware and Software » Thomas Henry designs
Bass++ Mods
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Dan Lavin



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PostPosted: Sun Feb 28, 2010 7:01 pm    Post subject: Bass++ Mods
Subject description: Let's share those mods!
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OK, I'll start it off. Here's an easy little mod that can added in minutes: a noise source. See attached schematic. This is a clone of the noise source from Thomas' MPS. With just the 2 transistors, it's signal level is low enough to go directly to pin 14 of the LM13700. Note the signal is not centered on 0V.

Attached is a sample where I adjust the decay. Note the first strike is snare-like (short decay). There are a couple of glitches in my sample caused by the cheapo switch I used bouncing a bit. Also, listening back, I have the impact tone set fairly high. The best sounds I got, I would call bass snare, if there is such a thing.

Next, I'd like to try adding in some 40106 oscillators with the noise through a bandpass filter and ..Wah-Lah!...a nice ride/splash/crash cymbal!

When I make my final front panel for my Quad Bass++, I'll add an input jack and pot, but probably will put a 100K ohm resistor between those and pin 14 of IC1. Then have a separate panel with the oscillators, noise source,mixer, filter and whatever else I think will be used with the audio and CV input jacks.


Bass++Noise.mp3
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Bass++ Noise with decay adjustment

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 Filename:  Bass++Noise.mp3
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Bass++Noise.pdf
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jordroid



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PostPosted: Tue Mar 02, 2010 2:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Excellent, thanks a bunch. I'll have to incorporate this into at least one of the four voices. I like your idea of a 40106 cymbalizer also, i think it would be fun to build a quad bass++ with each voice modified for a unique purpose. Oh, the backlog!
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The Peasant



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PostPosted: Tue May 11, 2010 9:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Bass++ mods? Yeah, I have a few.

I have actually spent the last weekend modifying this circuit, as I am building a small drum module to be triggered by a bass drum pedal striking a piezo sensor. This is so I can keep a basic beat with my foot while playing other instruments with my hands and singing.

Firstly, I left out the pitch CV input as I wasn't planning on using it in this project. So J2, R28, and R21 were simply left out.

Next, I changed the supply voltages to +/-9 volts, so that the whole thing could be run off of two 9 volt batteries. To compensate for the lower voltage I changed R5 from 1.5K to 1K to keep the LED brightness approximately the same. To reduce power consumption, I replaced the TL072 with a low current TL062 chip as well as raising the values of R1, R13, and R17 to 220R, 50K, and 100K respectively.

As this module will be used almost exclusively for bass drum sounds, I doubled the value of C2 to 0.01uF to lower the oscillator frequency range.

I wanted separate envelope generators for the pitch and volume functions, so I duplicated Q1 and associated circuitry. (Includes D1, C11, R4, 10, and 33) I also increased the decay potentiometer values to the more standard 1M, allowing me to decrease C11 to 1uF. This was done on both envelope generator circuits.

I found that triggering this circuit with a piezo disk caused some annoying popping sounds to be generated from the "impact" circuit, so I added a 2.2K resistor and a 0.1uF capacitor between D3 and R11/C9 to filter out some of the transients and lower the overall impact tone. Similarly, the "shell" VCA output also had some bad popping sounds, especially during short decays, so I added a RC filter to the current source. This entailed changing the value of R18 to 18K, adding a 2K resistor between it and the 2N3904, and adding a 0.47uF capacitor from where the two resistors connect together to ground.

Finally, I wanted some type of waveform control such as what the ADV Bass and UD Bass had. So I added a diode-based variable clipping circuit between the oscillator and the VCA sections. To do this R24 was changed to 10K, followed by a 100K potentiomenter, which then connected to two opposite-polarity diodes connected to ground, and finally a 5.6K resistor connecting to IC1 pin 14.

I am extremely pleased with how the circuit is performing now, and am especially happy with the waveform control. The sound can now be adjusted from the original "buzzy" triangle wave to a very smooth sine-like wave and then to a very resonant sounding almost-square wave. A very versatile drum voice is now even better!

I have included an updated schematic below, as well as a sound file showing the changes in sound produced by adjusting the new waveform control.

Take care,
Doug


basssynth.gif
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Bass++ MODS
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basssynth.gif



bdrumsynth.wav
 Description:
Adjusting the WAVE control

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 Filename:  bdrumsynth.wav
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richardc64



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PostPosted: Tue May 11, 2010 7:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Look like great mods. I'll try 'em when I get my Bass++ working.


10285701389.jpg
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"This is so I can keep a basic beat with my foot while playing other instruments with my hands and singing."
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The Peasant



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PostPosted: Tue May 11, 2010 7:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Laughing Laughing Laughing

Yup, that's the idea!

Take care,
Doug

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The Peasant



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PostPosted: Thu May 13, 2010 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, I have now finished building the project, it is looking and working well. More info and pictures at:

http://www.electronicpeasant.com/projects/bassbox/bassbox.html

Take care,
Doug


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Dan Lavin



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PostPosted: Thu May 13, 2010 7:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good job, Doug! These are the kinds of mods I was envisioning when I started this thread. I particularly like the waveform shaping!
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State Machine
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PostPosted: Wed Jun 16, 2010 6:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
OK, I have now finished building the project, it is looking and working well. More info and pictures at:

http://www.electronicpeasant.com/projects/bassbox/bassbox.html

Take care,
Doug


I really love this project and case you made. I went over to your website to check the project out and wondered if you can provide some details on you Piezo trigger?


Hey, I am thinking for an added wow factor, and since the case is clear, it would be cool to put some super bright LED's inside the case so that when it triggers, the entire case pulses with a beautiful glow of light Wink nice for on stage stuff. Cool

Bill
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The Peasant



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PostPosted: Wed Jun 16, 2010 7:59 am    Post subject: Reply with quote  Mark this post and the followings unread

State Machine wrote:
I really love this project and case you made. I went over to your website to check the project out and wondered if you can provide some details on you Piezo trigger?


Thank you very much for your nice comments! The details for the trigger/pedal are on this page: http://www.electronicpeasant.com/projects/ssdrums/ssdrums.html

Quote:
Hey, I am thinking for an added wow factor, and since the case is clear, it would be cool to put some super bright LED's inside the case so that when it triggers, the entire case pulses with a beautiful glow of light Wink nice for on stage stuff. Cool

Bill


That is an excellent idea! My only concern would be battery drain, but if they only flash when triggered it shouldn't be too bad.

Take care,
Doug

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State Machine
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PostPosted: Wed Jun 16, 2010 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Thank you very much for your nice comments! The details for the trigger/pedal are on this page: http://www.electronicpeasant.com/projects/ssdrums/ssdrums.html


Doug, I am very impressed by that work and by the sounds from your drum system ! Thanks for the details on your trigger also !

Now you really should build up a Quad Bass++ unit. (shameless plug .. he he). I still have PC boards for sale if your interested. Wink Wink

I agree, a flashing LED will not drain your batter very much. Just a thought. Glad you like the idea. Very Happy

Bill
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The Peasant



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PostPosted: Wed Jun 16, 2010 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

State Machine wrote:

Doug, I am very impressed by that work and by the sounds from your drum system ! Thanks for the details on your trigger also !


Thank you again for your positive comments! I'm glad that you like the drum synth, it was a number of years ago that I built that one. Lots of manual pcb design and etching. I still have to finish the second half of it with the cymbals, etc. One of these days!

Quote:
Now you really should build up a Quad Bass++ unit. (shameless plug .. he he). I still have PC boards for sale if your interested. Wink Wink


Well, if I didn't have a >30 pcb backlog I would definitely get a few. It may be years before I even get to my appendage pcb. But I'll have a look at them and think about it.

Take care,
Doug

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Dhamaryder



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PostPosted: Wed Feb 09, 2011 10:27 am    Post subject: how to make the pitch finer? Reply with quote  Mark this post and the followings unread

Hello, I just finished building my triple Bass+++. It's great. I was just wondering if anyone would know how I could make the pitch control easier to fine tune. would it just involve using a higher or lower value pot?
thanks a lot,
steve
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jumunius



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PostPosted: Tue May 24, 2011 10:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Just want to thank Doug for the shaping mod. Just got my it running on my first Bass++ this morning and I love it. As my Bass++ sits next to an MPS, I was worrying that it might simply be "MPS-lite", but that mod really helps re-define it. (Although I must admit I'm considering doing the same thing to my MPS given that I have one free hole on my panel.)

And since nobody has answered this:

Dhamaryder wrote:
Hello, I just finished building my triple Bass+++. It's great. I was just wondering if anyone would know how I could make the pitch control easier to fine tune. would it just involve using a higher or lower value pot?


Well, if I have nothing plugged into CV, the CV knob changes the pitch a bit. I assume it's not a bug, but the result of some voltage off the wiper of the pitch pot going to ground (do I have that right?). So the easiest solution would be to think of the CV knob as your fine tune (and if you have a CV input plugged in you probably don't care as much about fine tune).

If that doesn't work for you, a few general ideas:

1) Best would be to simply add a second "fine" pitch pot at a lower value (5k-10k?) in series with the existing pitch pot.

2) try the Electric Peasant's mod value of C2 simply lower your range, making fine-tuning easier (but making higher ranges unachievable). (There's still a pretty wide range available, so you could potentially even go further.)

3) I assume you could convert your pitch pot to a lower value and then add an ON-ON-ON switch which would switch between different resistor values that run in series with the pot (between pitch pot and R20 if I have that right?). The idea would be to have one switch represent R29 value of 0-40k, the next 30k-70k, and the last 60k-100k, so you still have all your desired range, but more control within each switch setting. I've done this with LFO values in other modules and it works well.
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inlifeindeath



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PostPosted: Wed May 25, 2011 5:37 am    Post subject: Reply with quote  Mark this post and the followings unread

yeah, i seem to be able to use the cv range pot as a fine tuner. it works quite well.
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Dhamaryder



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PostPosted: Wed May 25, 2011 6:02 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks for those ideas. They sound excellent. It might take me awhile to implement because i already put the panel together. If I was building a new one i would recommend one of these rather than use the Range as a fine tuner because if you've got intervals tuned with it(which sometimes takes awhile to accomplish) then messing with the Range to fine tune it will mess up your interval tuning. Anyway, what I did as a temporary fix was just use a bigger knob. It's not great but it is a small improvement. You can see it here, it's the big knob in the middle.

http://www.youtube.com/watch?v=-ATndvFLe2M
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Captain Biscuits



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PostPosted: Wed May 25, 2011 12:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've just finished my Quad Bass ++ and am at that frustrating stage of thinking "If I knew then what I knew now . . . . I'd do it rather different!"

I too want to have some finely tuneable bass notes rather than a huge range of pitch so I've just replaced the pitch pots on two of the four basses with 10K pots. To keep everything happy I've just added 90K of resistors between the +15v wire and the pot to keep 100K between the +ve and ground. It seems to work. I still get a fair range of notes but not the high tinging notes and I can tune the bass notes much better. Using the range pot too I can get pretty good tuning.

I was going to change the cap but realised I was already into sub audio at the bottom of the range so couldn't see the point.

If I did it again I wouldn't bother with separate volumes for shell and impact. I want shell up to 10 all the time and to be able to add more or less impact so shell vol can go. I might change one of them to input noise or something. As I'm always going into a mixer the main volume could go too.

The other thing I'd take out is most of the CV in sockets. Nice to have one or possibly two but I really don't need it on every voice. Taking out 8 pots and a couple or three sockets makes a fair bit of difference both in space and cost.

My next job is to try to make the low end of the impact tone a bit lower. I'd prefer a really deep thump and am not likely to be using the higher impacts on the bottom two drums. Back to the schematic!

Luckily I'm not precious about my front panels so I can get out the paper stickers and start adding notes to my front panel to explain my changes.

It is great that this design has such a lot of potential for mods. I'm looking forward to seeing more Smile

Ian
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droffset



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PostPosted: Fri May 27, 2011 2:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Definitely considering some of these mods before I drill the panel, thanks!
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jumunius



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PostPosted: Fri May 27, 2011 8:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Captain Biscuits wrote:
I've just finished my Quad Bass ++ and am at that frustrating stage of thinking "If I knew then what I knew now . . . . I'd do it rather different!"


Were I building all four (I'm likely only doing two) I'd definitely choose different options for each. I'd recommend people build one before building out the full panel.

I considered building without the shell volume, but I thought maybe in a song I'd like to drop the shell and leave only click or a few bars... then what? Another option for those who want to limit pots is to wire both imp and shell volume to a dual-gang pot, one wired in reverse. That would be a "balance" knob. But it might not sound as natural when sweeping it since both volumes would be changing at the same time.

The brighter side of the impact tone seems in keeping with other electric kicks, like the 808, no? In a mix I think it would help define the kick but to each his own.

And master volume is a bit redundant if you have a mixer, but it's nice to not have to move around too much while tweaking a sound.

I'd definitely say anyone building this circuit should leave room for the shape mod! Ahh, too many hard choices.
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The Peasant



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PostPosted: Fri May 27, 2011 10:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Captain Biscuits wrote:
My next job is to try to make the low end of the impact tone a bit lower. I'd prefer a really deep thump and am not likely to be using the higher impacts on the bottom two drums. Back to the schematic!
Ian


From my post above:

Quote:
I found that triggering this circuit with a piezo disk caused some annoying popping sounds to be generated from the "impact" circuit, so I added a 2.2K resistor and a 0.1uF capacitor between D3 and R11/C9 to filter out some of the transients and lower the overall impact tone. Similarly, the "shell" VCA output also had some bad popping sounds, especially during short decays, so I added a RC filter to the current source. This entailed changing the value of R18 to 18K, adding a 2K resistor between it and the 2N3904, and adding a 0.47uF capacitor from where the two resistors connect together to ground.


This mod does lower the impact tone considerably, it may be what you are looking for.

Take care,
Doug

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PostPosted: Fri May 27, 2011 10:49 am    Post subject: Reply with quote  Mark this post and the followings unread

jumunius wrote:
Just want to thank Doug for the shaping mod. Just got my it running on my first Bass++ this morning and I love it. As my Bass++ sits next to an MPS, I was worrying that it might simply be "MPS-lite", but that mod really helps re-define it. (Although I must admit I'm considering doing the same thing to my MPS given that I have one free hole on my panel.)


Thank you for your nice comments! I'm glad that the mod works well for you. Very Happy

Take care,
Doug

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hop.sing



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PostPosted: Tue Aug 09, 2011 3:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Doug

Just want to thank you for those great mod ideas. I incorporated the waveshaper and the seperate pitch decay control, and it does a fabulous kikdrum now. I use a log pot for tuning so I have better resolution in the bass area and have the connections from wiper to ground on the decaypots on minijacks so I can control the decay with the vactrol module from Doepfer.
I like to have a variable decay on my kicks, makes a groove much more interesting.
The bass+++ lives happily next to the mps. That is such an inspiring combo.
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PostPosted: Tue Aug 09, 2011 7:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

hop.sing wrote:
Hi Doug

Just want to thank you for those great mod ideas. I incorporated the waveshaper and the seperate pitch decay control, and it does a fabulous kikdrum now. I use a log pot for tuning so I have better resolution in the bass area and have the connections from wiper to ground on the decaypots on minijacks so I can control the decay with the vactrol module from Doepfer.
I like to have a variable decay on my kicks, makes a groove much more interesting.
The bass+++ lives happily next to the mps. That is such an inspiring combo.


You are very welcome! It's such a great circuit to start with thanks to Mr. Henry.

The log pot is a good idea, and using vactrols across the decay pots is another excellent yet easy mod. Thank you for your contribution!

Take care,
Doug

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PostPosted: Wed Aug 10, 2011 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's an easy one for people who use switching jacks that I borrowed from the MPS. Take a wire from the CW terminal of your Impact Volume to the switched jack on your CV input. (If you don't use switching jacks you should still be able to do this, I don't know if it's bad to just add it as is to a 2nd CV signal.)

This basically just modulates the Shell Pitch with the Impact tone. It is a fairly subtle effect here because the Impact decay is so fast, but when you set your CV pot high it basically creates a very short pitch bump as part of the attack of your drum sound. If you read Scott Stites' theory of the MPS, it is a realistic component of a drum sound (skin tightening upon impact). But more to the point, it adds just a bit of oomph to your drum sounds even without adding Impact volume.

The only downside here is if you are using your unconnected CV as a Fine Tune control when no CV is plugged in, you now have 2 functions depending on this knob. Ultimately I'm considering adding an SPST switch instead, so that the Impact Volume CW can be connected via resistor to the junction of R20, R21 and R23. It's not like this effect is so extreme that you need to finesse it with a pot -- on/off seems fine to me.

This attached file demos the mod. It's just a simple pattern played four times:

1) Straight Shell sound, Impact Volume at 0
2) Impact to CV Mod Shell Sound, Impact Volume at 0
3) Impact to CV Mod Shell, Impact Volume 10
4) Straight Shell Sound, Impact Volume 10

Comparing 1 and 2 gives the best sense of the mod. I uploaded this as wav with markers for each of these variations -- you can check out the first few cycles of each hit to see how they differ.


ImpactToCV_Mod.wav
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Impact Tone to CV Mod

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 Filename:  ImpactToCV_Mod.wav
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jumunius



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PostPosted: Wed Aug 10, 2011 11:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Actually, I didn't notice this when I tested my proposed Impact to CV mod the first time, but it turns out the actual pitch bump is down rather than up. It's a subtle difference but as I played around with it, with no additional sweep to confuse me, I got some more pronounced effects and it became clear that it was inverted from where I want it. Still a useful effect, especially if you are synthesizing a bass tabla. Smile

I've been reluctant to add much more circuitry to my build, but I'm considering a simple inverting op amp to fix this, running the output into the R20, R21, R23 juncture. Of course, those of you who have built Doug's independent decay control mod won't need this, but I couldn't spare the pot space so a switch is the best I can get. I could even do on-off-on with the ons being + and - respectively.
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PostPosted: Fri Aug 12, 2011 7:00 pm    Post subject:   Reply with quote  Mark this post and the followings unread

Hi, I'm trying to make this "pitch bump" mod work out, and using an inverting op amp I'm able to get a pretty desirable result, much cooler than the sample I posted earlier. My only problem is how to get rid of some DC voltage (about .5v) which causes the pitch of my bass++ to go lower.

The concept is simple:

CW of Impact Volume pot is connected to (-) input of a 1458 opamp via a 27k or 54k (switchable for more or less pronounced effect). (-) input is also connected to output via 100k resistor. (+) output goes to ground. Meanwhile the output connects to the CV junction at R20, R21, and R23 via a 47k resistor.

So the issue is the pitch drops to sub-audio for 10%-15% more of the pot's rotation. If I merely raise R8 will it solve my problem? Or do I want some other means to remove the DC offset?

Admittedly, I don't really get all the theory behind this. I'm inverting the Impact's voltage spike and amplifying it by 2x to 4x and using it as CV. Some of the choices (like the 47k to CV) are just trial and error. I don't fully understand where positive DC voltage is introduced. (Wasn't it blocked by C12?)

Any advice is appreciated. Apart from getting this offset issue cleared up, this is turning out to be a very nice addition to the drum sound. I'll post updated clips and a schematic when I get it worked out.
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