Q8, Q9, Q10 IN TB303

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Mussi81
 
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Re: Q8, Q9, Q10 IN TB303

Post by Mussi81 »

antto wrote:by "calibrate" - what do you mean? centering the cutoff knob to 500Hz like the manual says?
your 303 is okay, i can't see anything wrong with it soundwise

as for R97 maybe first try to mesure the actual resistance
in my x0x it was 9.97K, and after replacing it with this pot now, the usual value i tend to use is between 9.0 and 9.5K, but it gives me freedom to tweak it however i want (since i'm doing some experiments..) the pot is connected from outside the box (soldered some long wires in the place of R97)

in your case a 10K trimpot might be better, so you can directly solder it inside
basically ive messed about with ALL the pots, ive tried to set them up using just my ears but this isnt good enough for me as i want to know that its set up perfectly. its also out of tune i think.

can you set it up using a multimeter or is it best done with an oscilloscope?

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antto
 
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Re: Q8, Q9, Q10 IN TB303

Post by antto »

oh, the tuning..
well, AFAIK 303s have poor tuning.. it's kinda "scaled"
x0x tuning is done differently, it's solid
to tune the oscillator i think you just need to follow the manual and probably use a tone generator (or any kind of 440Hz (or whatever) reference, maybe another synth..)
oscilloscope shouldn't be required, but it might help more

Luap
 
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Re: Q8, Q9, Q10 IN TB303

Post by Luap »

I thought the tuning was handled the same between x0x and 303?
The circuit diagrams certainly look nigh on identical as far as I can tell anyway.

------------

You say you moved all the pots.. I take it you mean the internal trim pots? Most of them should ideally be left alone unless you know what they do and have the means to test them.

TM4 is the main tuning trim pot, and largely does the same as the main tune pot. So it is not too critical where you leave that, as tuning is easily corrected via the main panel tune knob anyway.

TM5 is the tuning width. So for example when you play a low C, then a high C, you need it to be a perfect C at each end, and not a low B# & a high D or whatever. This is probably why I thought your demo sounded a bit out of tune?
This is the awkward one to set correctly, if you are not used to doing it. I think the manual suggests using a scope to do this. I just used a good software instrument tuner which worked great.

TM6 is also an important one (but easy to set). This sets the voltage for much of the analogue audio section (5.33v). If this is off, then it also messes with the tuning. And can also supposedly affect the tone of the machine. Plus of course if it is too high, then this is not good for the health of many components. That said, this trim pot shouldn't have much range on it. It is less than a volt difference from min to max, if I remember rightly.

There is also TM3. This one confuses many people (including me! :lol: ) This sets the filter/resonance centre frequency(?). Many people just set this according to whatever sounds good to them. Which worked well enough for me too, and also compared well with the ABL software clone I have.

However, as I mentioned before, when you build your x0xb0x, you'll learn how to set all this up anyway. And it is just as applicable to your 303. Particularly as nigh on all the parts are labelled the same between the 2 machines. IE, TM5 is the same on a 303 as it is on a x0xb0x.

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phono
 
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Re: Q8, Q9, Q10 IN TB303

Post by phono »

antto wrote: oscilloscope shouldn't be required, but it might help more
it is needed to set the vcf freq correct, but it can be done by ear of course

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phono
 
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Re: Q8, Q9, Q10 IN TB303

Post by phono »

Luap wrote:I thought the tuning was handled the same between x0x and 303?
it is practically

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rv0
 
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Re: Q8, Q9, Q10 IN TB303

Post by rv0 »

i dunno, i never heard a 303 wich scaled so well as the rock-solid tuning on the x0x.

maybe i should adjust TM4 TM5 & TM6, will try that later on

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antto
 
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Re: Q8, Q9, Q10 IN TB303

Post by antto »

phono wrote:
antto wrote: oscilloscope shouldn't be required, but it might help more
it is needed to set the vcf freq correct, but it can be done by ear of course
2 ways:

1) grab a sine-wave generator (maybe one of your VSTs?) make it play a 500Hz sine and then go to your x0x
play long notes, preferably low-pitched.. resonance=MAX (and everything as said in the manual)
you can fairly well approximate 500Hz like this, adjust the volume of the x0x so that you can hear both the resonance of it and the sinewave from the PC

2) (the easier way) use your favourite sound recorder/editor
make a pattern of one long note.. let it loop
now record 1 loop of this pattern and zoom in somewhere in the middle of the note where the cutoff envelope has already relaxed
use some kind of selection tool and select one cycle of a sinewave from the resonance, then check how many samples the selection is (for example 122 samples)
then use this formula to convert it to frequency: Hz = (Fs / length) = (44100 / 122) = 361.4Hz
tweak the trimpot and repeat..

Mussi81
 
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Re: Q8, Q9, Q10 IN TB303

Post by Mussi81 »

Thanks for the replys to this thread

It's been a massive help, by the sound of it building the x0x would help me but I really want to get some other projects finished first before I start the x0x

Mussi81
 
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Re: Q8, Q9, Q10 IN TB303

Post by Mussi81 »

Luap wrote:
TM6 is also an important one (but easy to set). This sets the voltage for much of the analogue audio section (5.33v). If this is off, then it also messes with the tuning. And can also supposedly affect the tone of the machine. Plus of course if it is too high, then this is not good for the health of many components. That said, this trim pot shouldn't have much range on it. It is less than a volt difference from min to max, if I remember rightly.
so would this be the best starting point? if i use my meter and set this 5.33v and tune afterwards ill be on the right road?

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rv0
 
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Re: Q8, Q9, Q10 IN TB303

Post by rv0 »

Luap wrote: TM6 is also an important one (but easy to set). This sets the voltage for much of the analogue audio section (5.33v). If this is off, then it also messes with the tuning. And can also supposedly affect the tone of the machine. Plus of course if it is too high, then this is not good for the health of many components. That said, this trim pot shouldn't have much range on it. It is less than a volt difference from min to max, if I remember rightly.
The 303 service manual says this about TM6:
CV
Check point: CV out jack
With PITCH mode, press low C key and note the reading - CVL.
Press high C key, adjust TM6 for CVL+ 1.000V±3mV-CVM.
While holding down TRANSPOSE UP press high C key, confirm that the reading is CVM+1.000±3mV.
what does CVM / CVL mean? :?:

Luap
 
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Re: Q8, Q9, Q10 IN TB303

Post by Luap »

Mussi81 wrote: so would this be the best starting point? if i use my meter and set this 5.33v and tune afterwards ill be on the right road?
Start with TM6, because the right voltage only takes seconds to set with the aid of a good multi meter. 5.33v will do, or if your meter can do it, 5.333v

If you can manage to get the tuning width (TM5) sorted out, then you are well on your way to having a healthy sounding 303. There are a few documented ways to do it. Personally, I use a test pattern, using 8 low C notes, then 8 high C notes (use multiple octaves to get a good span). Play the pattern into an instrument tuner ("Tuna Pitch" on my mac works great for this) and keep tweaking TM5 until the 2 C's are perfectly spanned and in tune.
Actually, what you are looking for, is for the low and high notes to be the same and in tune with each other. 2 C's, or 2 D's, 2 F's etc.. It doesn't matter. You'll make sure your C key actually plays a C note later with TM4 and/or the front panel tune knob. It is a bit of a juggle, and requires some patience, but it is perfectly doable by yourself :) TM5 is the main tuning one to get right. TM4 is far less critical simply because it does much the same thing as the front panel tune knob.
The first time I did it, it took me several hours! Now it just takes me a few minutes..

Mussi81
 
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Re: Q8, Q9, Q10 IN TB303

Post by Mussi81 »

[/quote]

Start with TM6, because the right voltage only takes seconds to set with the aid of a good multi meter. 5.33v will do, or if your meter can do it, 5.333v
[/quote]

i can not for the life of me get a reading from tm6. i must be doing it wrong. im earthing one lead and the other lead is on the back pin of the pot, and no reading??

ok i now have5.33v dc..... dc is correct right?

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rv0
 
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Re: Q8, Q9, Q10 IN TB303

Post by rv0 »

thx luap, i just fixed scaling/width on my 303 using guitar tuner and dvm

TM6 was too low
TM5 was a BANNED to set with guitar tuner but its damn perfect now

I now set it so that Pitch-max = C.. thats how i like it
Thanks man!



EDIT: it would be nice if TM3 werent that randomly :D

EDIT2: made TM4,TM5,TM6 more permanent using a touch of nail polish

Luap
 
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Re: Q8, Q9, Q10 IN TB303

Post by Luap »

Mussi81 wrote: ok i now have5.33v dc..... dc is correct right?
Seems good to me.
darffader wrote: EDIT2: made TM4,TM5,TM6 more permanent using a touch of nail polish
Hmm, but one day it may need adjusting again. Can the nail polish seal be broken easily if needed?

The only way I can think of to make the tuning a little easier, is to replace the standard trimmers with the multiturn variety instead. It's much easier to hit the mark with those than it is with the standard parts. They would be good replacements for TM5 and perhaps TM6 also.
I just ordered a bunch of them from RS for future builds/servicing.

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rv0
 
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Re: Q8, Q9, Q10 IN TB303

Post by rv0 »

Luap wrote:[
darffader wrote: EDIT2: made TM4,TM5,TM6 more permanent using a touch of nail polish
Hmm, but one day it may need adjusting again. Can the nail polish seal be broken easily if needed?

The only way I can think of to make the tuning a little easier, is to replace the standard trimmers with the multiturn variety instead. It's much easier to hit the mark with those than it is with the standard parts. They would be good replacements for TM5 and perhaps TM6 also.
I just ordered a bunch of them from RS for future builds/servicing.
yeah nailpolish seal can be broken easily enough in the unlikely event you need to change it
i thought i'd seen it before on trim pots but asked for "approval" first to someone who's in the know about these things

multiturn would be good for TM4 too

now busy with my other 303, almost there, lunch break now ;)

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