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Getting a more 303 sounding box..
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Re: Getting a more 303 sounding box..

by antto on Mon Feb 24, 2014 7:18 am

rarara: no idea about BA662, but i think the offset itself comes from the 4 transistors when they aren't quite matched
the BA662 doesn't need those transistors and probably has something equivalent inside, if so - it's probably matched and there will probably be very tiny amount of offset which is not worth mentioning

the whole problem with the DC-offset is when you put the x0x thru distortion
the DC-offset adds low-frequency "mud" to the notes (both in the beginning of each new note as well as after a note ends, if it hasn't decayed yet) .. and when this gets amplified by the distortion - well.. actually who knows, someone might consider this as desirable effect

so maybe scratch that mod from the list

in any case, it's good that you ask, you don't have to follow my "recipe"
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Re: Getting a more 303 sounding box..

by antto on Mon Feb 24, 2014 7:26 am

3phase wrote:
antto wrote:i know 303s have more noise


good..and where do you think that noise comes from? its a quite audible sound difference… same components ..same circuit..where is the noise coming from? the original cpu? lesser shielding by the plastic front? lesser shielding and stray capacities and resistance on the circuit board? carbon film resitors? The power supply? Or just a mixture of all of that?

the entire circuit isn't the same

3phase wrote:In the end it might be an unsolveable goal to make the xox 100% sounding like a 303..its no 303.its a xox.. However.. getting a more 303 sounding box is possible. Some measures mentiond in this thread.are there more tricks to discover?

okay, let's say my x0x sounds "good enough" for me at this point

3phase wrote:someone should try to rebuild the original power supply..its definitely interesting to find out how much that contributes to the 303 sound.. But a very pricy mod..

it ain't gonna be me.
Last edited by antto on Mon Feb 24, 2014 7:29 am, edited 2 times in total.
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Re: Getting a more 303 sounding box..

by rarara on Mon Feb 24, 2014 7:27 am

well mine has the bcbox I/O so lots of distortion when required :D . i have never worried about a click as such until now, but my saw wave is noisy and harsh, so was thinking that this mod may help with smothness. this is an eternal circle of looking for a 'perfect' sound :roll:
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Re: Getting a more 303 sounding box..

by antto on Mon Feb 24, 2014 7:33 am

i don't know what more to say than this:

if you have a TB-303, then even if you circuit-bend the hell out of it - you can still say "it sounds like a 303" because it's a 303
a x0xb0x isn't exactly a TB-303

if you can't sleep at night due to this fact - it's bad

my advice is: accept it and make some music
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Re: Getting a more 303 sounding box..

by 3phase on Mon Feb 24, 2014 7:45 am

antto wrote:the entire circuit isn't the same


not true. the audio section is all the same .. the board layout is´nt the same.. and thats really a possible factor for the sound differences. Maybe a bigger one than the power supply.
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Re: Getting a more 303 sounding box..

by 3phase on Mon Feb 24, 2014 8:15 am

rarara wrote:well mine has the bcbox I/O so lots of distortion when required :D . i have never worried about a click as such until now, but my saw wave is noisy and harsh, so was thinking that this mod may help with smothness. this is an eternal circle of looking for a 'perfect' sound :roll:


I hope not..That was the biggest draw back with the xox that it eats so much time to get the sound right or at least good enough. To have it singing like a real 303 would be desire able after all the already performed efforts. Its only the mods that make the xox worthwhile since i dont like to slaughter my 303. MAybe i order one of the sumidas from tech transplant at one point..


Anyway..the most essential list to avoid having a very brittle sounding xox is..


5% carbon film resistors
Standard electrolytics with the typical mushy sound of cheeper caps..
avoid fake transistors.. better source the double ones yourself in old vcr´s
Use the original roland vca..
945 have a warmer sound to them
Original green transparent foil caps have a finer sound to them. ( do you oppose to that annto?)

Thats the basics..

well tune and adjust it…
How to do that? This thread could hold more info regarding that since there are plenty of points in the circuit where the behavior can be altered…


And than?

The big power supply question is a point that still needs to be investigated..

And the fx of transistors matching could be investigated..just going for high betas dont seems t nail it and even when nothing really indicates a special selection process it cant be excludet. There are exceptional good sounding 303´s out there..maybe by accident..or some got build with selected transistors while others got just randomnly equipped.. Wouldnt be the first time that such things happen during the production process of electronic instruments..
Last edited by 3phase on Mon Feb 24, 2014 11:56 pm, edited 3 times in total.
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Re: Getting a more 303 sounding box..

by 3phase on Mon Feb 24, 2014 5:32 pm

And one thing to add on my list.. the bias of the filter envelope is very important for the balistics here. Transistor choices around that area have a big impact on the way the filter envelope acts and sounds.. BUT.. you can alter the bias with the resitor values of cause too and having a little trimmer at the right position here ( Instead of R 64 or R 65 ) might be the quicker way than swapping many transistors..
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Re: Getting a more 303 sounding box..

by aminoacid on Wed Feb 26, 2014 8:33 am

i also found that q9 is good to look over. i took a npn with low vbe drop.

i also found that r113 and r114 will make stuff sound different aswell. i liked high r rather than low r.

the carbon film resistors did great!!! ive changed about 35.

im very sure about the psu is having a great impact on the sound. with the original psu design youll get the effect, i call, "the funk". it limmits dynamics in a cool way. prob makes the machine get on its knees a bit when heavy resonance is used. how do i know`? cause i rebuildt the psu with the sumida transformer. i even got batteries inside(however i have problems with the processor reseting itself too easly)! it sounds alot different to me.

other stuff i thought about is:
when i experimented with my 606 i noticed that theres more signals on the trigg lines than just common trigg and instrument trigg. i guess its because the cpu and ram are talking to each other on the same lines but in much faster words.. since the 303 uses the same cpu and rams maybe theres some extra traffic there aswell going to the adc, trigg, accet, slide, etc. in the 808 serv manual you can read on how the cpu and ram works and it has the same cpu and ram.

and the sync is horrible if the xox isnt slaved by a proper sync master unit like the mpc2000xl or a dinsync unit like the 606, this i found to be the very best setup. it will make the music soo much better. 606 masters the xox and the xox transmitt the sync further on via midi. it would be cool to reproduce the analogue clock and sync circuit of the 303. but that might be overkill.
my machines kills fascists!
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Re: Getting a more 303 sounding box..

by 3phase on Wed Feb 26, 2014 5:06 pm

aminoacid wrote:and the sync is horrible if the xox isnt slaved by a proper sync master unit like the mpc2000xl or a dinsync unit like the 606,


What was unproper sources? And what OS are you using?
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Re: Getting a more 303 sounding box..

by 3phase on Wed Feb 26, 2014 5:44 pm

aminoacid wrote:im very sure about the psu is having a great impact on the sound. with the original psu design youll get the effect, i call, "the funk". it limmits dynamics in a cool way. prob makes the machine get on its knees a bit when heavy resonance is used.


I actually tried to simulate that fx with a resistor in the powerline to reduce current delivery ..but..that hasnt brought any usefull fx..

Than i tried a little lamp.. just what was laying around.. and it of cause didnt light up.. but it already worked better than a fixed resistor.. you got the fx that it was compressing the high accented notes on high feedback sequences. And the fx seemed to work more elastic than a fixed resistor. But still weakening the bass response..but not as bad as with the fixed resistor.. but maybe just 10 ohms less resistance and you had that fx.. In Theory a lamp is a current flow dependend resistor.. or as brighter it gets as higher its resistance get.. but you need to get it glowing than..and i havent looked further into it since it gets complicated than to really have a glowing lamp a serial resistor in the Powerline.
Would be good to qualify the difference in current delivery between xox and original 303.
Anyway..just wanted to mention that experiment. probably i will rather go for a replica of the real thing at one point. But would be funny when the right type of 50 cent lamp would do the same as the 50.- sumida transformer .. But as mentioned earlier..i think the noise of the power supply might be important too.
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Re: Getting a more 303 sounding box..

by rv0 on Thu Feb 27, 2014 6:20 am

aminoacid wrote:and the sync is horrible if the xox isnt slaved by a proper sync master unit like the mpc2000xl or a dinsync unit like the 606, this i found to be the very best setup. it will make the music soo much better. 606 masters the xox and the xox transmitt the sync further on via midi. it would be cool to reproduce the analogue clock and sync circuit of the 303. but that might be overkill.


overkill indeed.. n0nx0x2 has proper sync

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Re: Getting a more 303 sounding box..

by aminoacid on Thu Feb 27, 2014 6:27 am

i might exagiarated about the sync beeing horrible but if the sync isnt starting everything on the 1st step very simultaniously and holding the sync very linear it will sound like a bad day in my oppinion. the xoxbox internal clock does this jobb quite bad.

ive used analoguesolutions europa, jomox xbase09, abelton live, and prob other machines that my freinds had when jamming. 606 > xoxbox > jomox for instance sounds fanstastic. the other way to go for me is with my mpc, it makes all machines start att the same time and holding a good sync.

i have sokkos. cant remember the version.

when i give my ml303 some service and change in parts ill see how its psu works without the sumida transformer, instead using a 7815.
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Re: Getting a more 303 sounding box..

by 3phase on Thu Feb 27, 2014 7:42 am

I get a 606 in for repair and heavy modding..and the owner is ok with lending me his sumida for some tests next week..
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Re: Getting a more 303 sounding box..

by 3phase on Tue Apr 01, 2014 4:28 pm

So i did the powersupply test..and as i expected it..it does something good to have the original roland supply..but

its also just a little step and not really much bigger than good capaciator choices in the filter.. it does however sum up .. and with all the others measures mentioned here it gets a little closer.. there is still a certain harder tone than on my 303.. so its again not the power supply alone that makes the difference.. its a combination of all..and the actual circuit board design and material is probably the missing link..except maybe some gate timing things.. i will get into that at a later point..

I made some little test loops..but..as single loops the difference is not as big as i experience it while playing the thing..seems to have more little fluctuations and more elastic feel to it with the original powersupply. And this gets lost on a sampled loop..and than the difference gets really small..

one can discuss if the hazzle of building an original power supply is worth the little difference..

I am not sure yet..getting the parts is not easy.. But i like it more with the original powersupply..especially the square gets better..

Question now..can the behaviour of the power supply be simulated? I dont want to put t much time into that right now.. but its an area one culd dig deeper into later..

can i upload the loops here?
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Re: Getting a more 303 sounding box..

by 3phase on Tue Apr 01, 2014 4:42 pm

i tried..but now the are really just one repetition..difference even smaller..
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