Modify stock ts9 with sparledrive blend...

[Projectile]

Hi guys, this is my first post here, and I have to say this is a great community. I'm really glad this place exists and I learned a lot searching through old posts on this forum. I've built a few electronics projects and modified some amps and pedals in the past, but I still consider myself a beginner. I have some ideas and I was wondering if some of you with more electronics knowledge than I have wouldn't mind helping me with and giving some suggestions.

Basically, what I'm thinking about doing is modding a stock ts9 with a clean blend like the one in a Voodoo Labs Sparkle Drive. I've seen a few other solutions like Sean's bBlender, but I'm wondering if this particular way would work.

The TS9 and SparkleDrive seem to be nearly identical all the way through their input buffers, clipping section, and tone section. Except for a few small changes to cap values, they only really seem to differ in the addition of the opamp boosted(?) clean blend section that is wired in parallel to the clipping section and the tone section, and also different output buffers. The TS9 has a transistor based output buffer, where as the SparkleDrive uses the other half of the opamp that it uses for the clean blend to accomplish the output section. I imagine VDL probably changed the output stage because they had the available opamp left over, and could cut the cost by not adding the extra transistor... but I'm not sure? So, basically what  I'm asking is: will the clean blend section from an SD still work properly with the original output section from the TS9? And then, following that logic, would it be possible to just mod a TS9 by dropping in the blend section from the Sparkle Drive without changing the output stage, or is there something I'm missing?

Seems pretty simple, just 2 resistors, an opamp, and to a dual gang pot and you basically have a sparkle drive.

Here are the schematics for the TS9 and the SparkleDrive for reference:

http://www.muzique.com/schem/ts808.gif
http://home.hetnet.nl/~chrisdus/download/VLSD.jpg

And here is a quick photoshop kludge of what I'm proposing:

http://www.freeimagehosting.net/image.php?bf6650062e.png


Could someone take a look at it and let me know if this looks do-able. Thanks a lot.

Oh, and one other question for the time being. What is the purpose of R10? and why is it so large? 100k seems like an awefully large amount of resistance to just drop in the direct path(?) of the overdrive circuit. Wouldn't that drastically reduce the output of the whole overdrive section? Okay, I'm getting ahead of myself. I'm just going to let someone far more experienced than me explain.

[ianmgull]

I honestly don't know the answer to this but if it does work PLEASE report back because I would love to try this.

[km-r]

take the sparkledrive schematic, replace clipping section from U2b to U2a and connect in the TS components from IC one A to one B...

correct?

[Projectile]

take the sparkledrive schematic, replace clipping section from U2b to U2a and connect in the TS components from IC one A to one B...

correct?

No, I'm starting with a ts9 and just dropping in the clean blend section copied from a sparkle drive schematic. The sparkle drive uses a different output configuration than the ts9, but I wondering if it's necessary to use the SD's specific output section in order for the clean blend circuit to work properly. If the different output section isn't an essential part of the clean blend circuit that comes before it, then I should be able to just drop the clean blend circuit form the SD into a stock ts9, because other than that they appear to be mostly the same. (though I may have to move it to another enclosure to get it all to fit)

This should all be clear in the last schematic I posted, which shows my proposed modification in purple. I just don't have enough electronics knowledge to know if this is a feasible mod.  It looks like it would work to me, but my knowledge is very elementary, so I would like someone to look at it and tell me if there are any glaring errors with my idea, which I suspect there may well be. 

The one thing that does seem strange to me is R10, which seems like it might greatly reduce the output of the clipping stage compared to the stock ts9, and then I'm thinking the SD might be making up for this lost gain in the output stage, which would be a problem if I try just dropping the blend circuit into a ts9, but I really have no idea. I'm just taking shots in the dark here. This is why I want somebody to take a look.

Am I making any sense? If you compare the SD schematic to the modded TS9 schematic at the bottom of the post it should clear things up. A picture is worth a tousand words.

[Projectile]

take the sparkledrive schematic, replace clipping section from U2b to U2a and connect in the TS components from IC one A to one B...

correct?

Okay km-r, I read your post again and I think there might be just a minor translation error or misunderstanding. If I edit your statement to read like this:

"take the sparkledrive schematic, remove the clean blend section from U2b to U2a and connect it in to the TS components from IC one A to one B..."

...then it IS an accurate description of the mod I'm proposing. Thanks.

[km-r]

oh yes, i took it the other way around haha... 

i never got the chance to try out those clean/dist blend thingies...

good luck

[slacker]

What is the purpose of R10? and why is it so large?

On the sparkledrive R10 works with the volume pot to set the volume of the overdriven signal. U3B makes an inverting amplifier as shown here http://sound.westhost.com/dwopa.htm#invert, the volume pot and R12 equate to R1 and R10 equates to R2. So when the volume is at maximum you get a gain of just over 1 and as you turn the volume pot down you reduce the gain and the volume of the overdriven side.
On the clean side R11 and the volume pot set the gain so at maximum you get a gain of about 7.5 (100/13.3), this is probably to make up for the difference in volume between the clean and overdriven sides.

To keep things acting the same in your schematic I would keep U3B but replace the volume pot and R12 with a 100k resistor then take the output of that to the 1uf cap before the volume pot.

[Projectile]

Thanks for the help guys. I realized I'm in a bit over my head here. I don't have enough electronics knowledge to thoroughly understand how different circuit components interact, so I choose a different route. Instead of botching a perfectly good tubescreamer, I ordered a breadboard and all of the parts I would need to build both a Tubescreamer and a Sparkledrive. Now I can experiment with both circuits all I want and see for myself what exactly I can get away with. Might as well just get my hands dirty, right? I'll report back here with my findings. This will be my first try at breadboarding anything, so wish me luck.   

[Derringer]

This won't work exactly the same way as the sparkle drive blend does ... but I think it's a good place for you to start when dealing with the "blend" concept.

"Buff'N'Blend"

http://aronnelson.com/gallery/main.php/v/Toneys-Album/Buff_n_Blend.png.html

http://www.geocities.com/jrtookmyfalseteeth/buffblnd.gif

[Projectile]

Just wanted everyone to know that I did finally breadboard this and I now have a working version of a sparkledrive-like clean blend that leaves the original TS circuit almost entirely intact. I had to totally abandon the Sparkle Drive design after understanding it a little better, but I found another solution that works great.  I'll report back with a working schematic soon.

[aziltz]

Just wanted everyone to know that I did finally breadboard this and I now have a working version of a sparkledrive-like clean blend that leaves the original TS circuit almost entirely intact. I had to totally abandon the Sparkle Drive design after understanding it a little better, but I found another solution that works great.  I'll report back with a working schematic soon.

it never does make true sense until you breadboard it!  good form!