tubescreamer for bass

[Al Heeley]

In search of my ultimate bass distortion.overdrive, I've been contemplating a new pedal build based on my favourite guitar overdrive , the Tubescreamer 808. Made a few of these for guitar now and they are great, but high mid range boost means they are awful for Bass.
There's a few posts on stompbox forums, Aaron Nelson, etc. with some info on modding tubescreamers to make them more bass frequency-frienly and I wondered if anyone had any experience with these mods and the sounds they can give.

example: the tiny 51pF cap on the standard TS-808 circuit can be replaced with a 0.47uF cap, says Mr. Nelson, to extend the circuit's distortion/overdrive as low as 72Hz. there are other '(AMZ) Phat' mods bypassing a second 0.047uF cap, as well as adding a mini switch to toggle in a third assymetric diode to give a 'more tube-like' sound, a smoother cut off to the sine wave, nowhere near as harsh as a fuzz box square wave.

I thought I'd have a go at putting all these mods + switch options onto one BassScreamer pedal and see how it works out, but be interested to hear from anyone else that's already explored the use of the modified ts circuit for bass.

[Dood]

Al,

An idea that I have been contemplating for a long while would be to take a guitar pedal - have the above mods available as switchable options, then have the ability to mix in a dry low pass (adjustable) bass signal. This would allow the correct amount of bass signal in to the dirty mix. To better explain it, if the dirty signal came down to say 200Hz, you could mix in a low pass dry bass signal that would slightly overlap. This would mean the dirty signal wont be muddy and the bottom end will remain tight and focussed - not flabby and undefined (like the BDDI on high drive seetings for example.) Obviously if you wanted to mix the whole bass signal in, then wind the low pass all the way open so that there is no filtering.

Does that kinda make sense?

[vegas_hooker]

I had a TS9 up until very recently with the 808 keeley mod installed and it was very much as you describe above, the high mids made it a little 'off' for bass and rolling a lower tone on the pedal sounded a little muddy. I found the fulltone bassdrive to sound pretty much the same but with much more low end response and flatter mids (with the sacrifice in guitar level highs).

It sounded the absolute t*ts on guitar though and I regret selling it for that reason.

Not sure if thats the contribution youre after, but my two pennies anyways. If you end up having a stab at this and making them then give me a yell. I would be interested

Edited January 26, 2010 by vegas_hooker

[umph]

[quote name='dood' post='725193' date='Jan 26 2010, 02:22 PM']Al,

An idea that I have been contemplating for a long while would be to take a guitar pedal - have the above mods available as switchable options, then have the ability to mix in a dry low pass (adjustable) bass signal. This would allow the correct amount of bass signal in to the dirty mix. To better explain it, if the dirty signal came down to say 200Hz, you could mix in a low pass dry bass signal that would slightly overlap. This would mean the dirty signal wont be muddy and the bottom end will remain tight and focussed - not flabby and undefined (like the BDDI on high drive seetings for example.) Obviously if you wanted to mix the whole bass signal in, then wind the low pass all the way open so that there is no filtering.

Does that kinda make sense?[/quote]
adding a clean signal is always great, you don't always have to low pass it though as the effected signal tends to sit on top of it anyway.

[Silent Fly]

[quote name='Al Heeley' post='724486' date='Jan 25 2010, 08:08 PM']In search of my ultimate bass distortion.overdrive, I've been contemplating a new pedal build based on my favourite guitar overdrive , the Tubescreamer 808. Made a few of these for guitar now and they are great, but high mid range boost means they are awful for Bass.
There's a few posts on stompbox forums, Aaron Nelson, etc. with some info on modding tubescreamers to make them more bass frequency-frienly and I wondered if anyone had any experience with these mods and the sounds they can give.

example: the tiny 51pF cap on the standard TS-808 circuit can be replaced with a 0.47uF cap, says Mr. Nelson, to extend the circuit's distortion/overdrive as low as 72Hz. there are other '(AMZ) Phat' mods bypassing a second 0.047uF cap, as well as adding a mini switch to toggle in a third assymetric diode to give a 'more tube-like' sound, a smoother cut off to the sine wave, nowhere near as harsh as a fuzz box square wave.

I thought I'd have a go at putting all these mods + switch options onto one BassScreamer pedal and see how it works out, but be interested to hear from anyone else that's already explored the use of the modified ts circuit for bass.[/quote]

The 51pF capacitor creates a filter that removes the top range. Increasing the value makes the pedal sound darker but it should have no impact on the mid-boost.

With the + input connected to the bias voltage via a 10k resistor, I am not sure bypassing the 47nF capacitor is a good idea. You could try increasing it but I think it is better keeping it.

You could also try to apply the Big Muff clipping system to the TS. In practice it is a capacitor in series to the two clipping diodes. If you look for a Big Muff schematic, you'll see what I mean. I never tried it on a TS but it should leave the low frequency go through and the high frequencies clip. You could also change the capacitor with a switch to change the frequency.

Alternatively, you could put a resistor instead of the capacitor (or in series to the capacitor). The resistor will change the clipping curve making the diodes a little bit less aggressive.

Edited January 26, 2010 by Silent Fly

[Al Heeley]

Thanks for the input guys - this is getting interesting.
I'm thinking a mini blend circuit like I added to the fuzzy elephant, to mix wet'n'dry signals, and 3 mini toggle switches, one for the 51pF -> .47uF lead to bass mod as per Aaron nelson, one for cap bypass (AMZ phat mod) - or switching in a different value cap, and one for additional diode for assymetric clipping since I have a spare switch.
There's another mod which switches in different types of diode clippers or LED's instead of the stock ones. Not convinced it will be tonally significant but I'd be happy to be proved wrong.
Looks like I need to go for a bigger enclosure.

[umph]

ey up, i'm with silent fly on this one the 51p isn't the cap you want to be increasing its the .047 in the negative feedback you want to be increasing to increase the frequency gain below the normal range!

changing the normal diodes for germanium or LEDS will have a pretty big effect on the sound aswell - germ more compressed and fuzz / leds more open and overdrivey sounding.

[Al Heeley]

Thanks Max & Umph, I stand corrected, was reading the schematic wrong. [url="http://www.muzique.com/lab/fatt.htm"]http://www.muzique.com/lab/fatt.htm[/url]

[Alfie]

I have just built a TS with the mods you are going to do (it is my Custard Cream in the gear porn section), I found that with the AMZ phat mod it was pretty good with bass without further mods, and spot on after a blender. However I already have a Fulltone Bassdrive, which is basically a Tube Screamer, so I didn't see the point of going mad with bass mods.

[Al Heeley]

that's great to hear - sorry your custard pic links seem to have gone AWOL

[Alfie]

[quote name='Al Heeley' post='728973' date='Jan 29 2010, 05:35 PM']that's great to hear - sorry your custard pic links seem to have gone AWOL[/quote]

They seem to be working for me, but I shall add them here as attachments too

[attachment=41437:DSC_3735.JPG] [attachment=41436:DSC_3743.JPG]

[Al Heeley]

Simply stunning! Lovely enclosure work there. Now I understand more of the biscuit thread.
Having just finished wiring up the pcb outside the box i must say i am initially very impressed with the modded TS808 circuit.
I went for a switchable .47 - .047 cap and an additional (switchable) assymetric diode clip, plus the 1meg drive pot, and it's fat, it's rich and dripping with harmonic overdrive. Now I'm putting it all in its enclosure then i can runa full check with lead guitar and bass. Sounds like an instant winner so far - and worked first time straight from the solder mat, which is a huge plus for me....

[Al Heeley]

Finished the build, pretty pleased with the results. We have a standard classic TS808 circuit from DIYStompbox galley:
[url="http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/TS808_TubeScreamer_LAYOUT.gif.html"]http://www.aronnelson.com/gallery/main.php...LAYOUT.gif.html[/url]
Then D1 has been put on a DPDT switch with a second 4148 diode siwtchable in series to give the FULL or SOFT clip option,
I've wired up an ON/OFF/ON mini toggle switch to where C4 was sitting and wired so it gives either 0.047uF cap, 0.47uF cap or both in series to radically change the tone range. the rest of the circuit is pretty much stock.
With lead guitar feeding into it, the pedal gives the expected lovely rich overdrive with the mid/high boost tone, that is with clipping on full and range on high.
Switching range to mid or Phat gives a great heavy bass boost to the signal, maybe too flabby for some high gain stuff but maybe superb for baritone metal riffs.
Switching clipping to soft introduces the third diode and assymetric clipping option, which softens down the distortion gain quite a bit while giving a more creamy smooth softer tone. Very nice.

With bass, you really need tone range on PHAT or you just get a bit too much mid honk. Seems to work best with clipping on soft and gain up at half to give a softer fuzz-type overdrive. If you want to get really nasty, put the clip on FULL, the range on MID and bring the vol back a bit - very sharp aggressive tone, cuts out any bass flab, sounds more like a nasty fuzz.

Seems this little mod gives a pedal that should be incredibly versatile for either bass or lead guitar. Will be trying it out live at next Friday's gig in Wooldale.
Very constructive way to spend a Saturday morning Edited January 30, 2010 by Al Heeley

[ase_one23]

or u could get a visual sound jekyll and hyde like me! the jekyll overdrive is an 808 style overdrive with bass boost - sounds amazing! plus u can pick them up pretty cheap on ebay every so often.

[Al Heeley]

OK here's soime quick clips played straight out the pedal into the soundcard, pretty bare but you get an idea.
[url="http://www.mediafire.com/file/q1myut44bim/ts808sclip.mp3"]http://www.mediafire.com/file/q1myut44bim/ts808sclip.mp3[/url]

Tone knob set to 3 o' clock, gain set to about 10 o' clock
first 4 soundbites are guitar (humbuckers N+B together)
1) Soft clip, hi tone selected
2) soft clip, mid tone
3) full clip, mid tone
4) full clip, phat tone
(Normal default unmodded TS position would be full clip, high tone)

Next is bass, again tone set to 3am, gain on about 10 am. Vol is on about 10am
1) soft clip, phat tone
2) soft clip, mid tone
3) full clip, phat tone - almost double the gain with full on
4) full clip, mid tone loses a bit of the heavier bass, gives a more aggressive edge to the o'drive

[Al Heeley]

As an additional development of the ultimate tubescreamer, I put together this clipping module which will attach into the diode clipping stage of a distortion or overdrive pedal and wires up to a 6-way rotary switch.
You get:
1) Normal back to back clipping
2) asymmetric 3-diode clip
3) 2 x LED clip
4) Si + Ge diode clip
5) 2 diode plus small cap smoothing
6) LED + Si diode clip

Will wire this into the next tubescreamer coming out of the sonic kitchen

[BigBassBob]

Very interesting stuff, Al

I'm using an Abunai 2 (BYOC TS 808 with some mods) in a blended loop which does the trick, but I've been contemplating having a go at changing the caps in it to get a bit more bass. It's a nice pedal for w***ing up in the higher registers and I tend to favour my Roger Mayer Voodoobass for most applications anyway.

[Al Heeley]

Pondering rewiring on the drive to work - this should simplify the whole thing a bit and cut down on soldering time:

[umph]

sounds and looks great!

[Al Heeley]

Here's the final item using the clipping module.

Sonic Kitchen is a Tubescreamer (SRV Special, ex maxxon) circuit with the clipping module added to replace the original two side-by-side diodes, and with an extra input cap on a mini toggle switch which combines a 0.47uF and a 0.047uF (the original) cap.
The bigger cap gives a huge extension to the bass range making for some dark grungy overdrive also highly suitable as a Bass guitar distortion pedal.
Leave freq on high for the original characteristic Tubescreamer mid-boost, for lead guitar work.
The clipping switch works nicely, theres some subtle differences to the distortion characteristics trying out the different modes. A couple of sweet smooth creamy overdrives on the asymmetric, the Ge/Si mix and the smoothing cap setting, as well as some much higher gain, raw distortion tones using the LED settings.
Basically 6 overdrives in one, with a huge tonal range extension built in. The ultimate tubescreamer!

[mancunianfox]

Awesome pedal Al. I really like your idea of the switch to select so many different diode options. Your labels look particularly good. Any magic there or just water slide decals?

[Al Heeley]

Thx fox, I printed the graphics out onto an overhead projector slide in reverse then glued it print side down to the enclosure with a thin smear of araldite epoxy. First time I tried that so a bit messy, a couple of crinkly air bubbles but it ain't going anywhere.

[LukeFRC]

nice! do you have any shots of it's guts? it looks quite dinky too

[Al Heeley]

heres the circuit + mods

PCB layout pic Courtesy DIYStompboxes.com

[Al Heeley]

Here's the guts