Sound differences xox vs. 303

[3phase]

hello,
I just made my first runs with my xoxbox..

But the first test wasnt really like a 303 sound i know...

but via part selction i got allready closer to my goal to make it sounding like the 303´s i know...

Ok..they all sound different..but i miss a certain type of smoothness that is common to all of them..

My xoxbox sounded initially harder... not bad.. but not so close as i expected for a circuit that is so close to the original.

I started swapping a few pNP transistors with my old 303 what helped actually a lot..even when the old transistors dont have betas higher then 260.. they sound much more bodyfull and 303ísh muffeld...

I did the reverse check with 733p´s in the old 303... there the sound difference appears not as strong..but is still there...

733ak´s was actually getting closer to the 733ap than the 733p... but that might be beta related..the ak´s have the highest beta of the transistors i ve availible... but that made them only favorable in position Q33 and Q 9...
And even there i would have go for the original used 303 733ap´s when i would have enough availible..

this results in some new questions...

1) is the sound difference related to the transistor type? or is it related to transistor aging? the pnps with the lowest beta in my original and intesivly used 303was found in the filter... with betas around 220... all others was above 250...

is this maybe an aging effekt because the are driven harder in the filter circuit? Or just accidental?
Nothing in the 303 gives indication that the transitors was selcted...

I never considered a single transistor so much as a sound dominating part... and as said within the original 303 the differences are subtile..while in my xoxbox i clearly hear the difference between any transistor..even within the same type and batch..

this especially clear sounds indicates maybe a problem with my xoxbox that has panasonic bc´s for all electorytics.

Maybe they clean out the sound too much opposite to the originals 303 muffly charakter that well can be partially be related to the standart electrolytcs that are used in a huge amount...

I will check that later...
but i expect using the recomended standard electrolytics will give a more original 303 sound.

Another thing i came along is that the foil caps in my 303 and 606 are a different type than the ones recomended in the xoxbox partlist...

they are the transparent green japanese foil caps ..the ones that you usually find in better japanese hif equipment from the 80´s..

As a general experiance from highend preamps i know that better foil caps have a subtile smoother sound...

But however.. i dont know if any 303 has the green transparent foils or just early units...

maybe its mainly a question of aging...especially musical instruments tend to sound smother when they get older..

This applies to electronic instruments aswell.

Maybe the xox box sounds more like a brand new 303?

Regarding transistor selection i can tell that Q8-10 are indeed the most significant PNP´s for beeing selcted

But Q33 is a position that is important aswell... and Q27..especially in combination with Q8 this shapes the sonic character of the xox box quite a bit..

I just got a few original ba 662.. i will see what they do..but after listening to the test audiofiles on the forum i expect them to add another little muffle that brings the whole thing closer to the original 303 sound...


I will post my additional findings...

[3phase]

some adds,

with an BA662 in the xoxbox the differences between transistors get less dominant as in the real 303..

The BA6110 is not responsible for the harder sound i am fighting against.. But it is more bright and clear than the BA662..

I havent decided yet which one i prefer.. of cause the BA662 is a bit closer to the Roland TB303, but the aditional brightness is not ugly...

Regarding the original 733pa´s : They have a more pronounced/distorting midrange than the new 733p´s and 733ka´s..

That is most beneficial in the oscilator for Q27 and Q8..
because there it brings the whole thing a lot closer to the sound i know from my 303.. especially the saw via Q27 gets closer to the real03 with that little dirt in the midrange the 733pa´s provide...

However...its not far or bad sounding with other types in that position..
Just IMO opinion the best place for original transistors...

In the filter and output amp its a question of taste..high beta other types sound interesting aswell when beeing selected for good behavior...

On an original 303 its only possible to source 3 733pa´s without altering the sound ...
So i will stick witgh 2 for the oscilator and the position for nr.3 has to be decided during the mod process..either Q10 or Q 33

In the moment i expect the panasonic BC´s to be most responsible for the harder sound...

I will bite in the sour apple and replace them later...

[guest]

these are all good results
thank you for doing this

[katarakt]

Very interesting! Good work 3phase!

Well, i've read on the net that some people examined the same that different capacitors change the sound VERY much! I'm not sure, the one i can remember wrote that plastic capacitors (edit: MKT) are really make a big change to the sound in a negative way.

As i can remember the one wrote the same thing with these green capacitors you mentioned so this would be really really interesting! Hm, can you give me a link to these green "high end" capacitors? I 'll check them and maybe i build my second x0x with all the green caps.

Maybe there's something else beside the highbeta transisors and powersupply which gives the magic in the real 303? maybe the capacitors

[bcbox]

nice work 3phase.
I was very surprised reading your notes because I can confirm a lot of what you have written.
I have also taken all the transistors from one of my 303's and put them in a x0xb0x. I this case I too found it sounds pretty much identical. Also I found that when I put the x0xb0x parts in my 303 it actually didn't change the sound too much, still very much fluid. This agrees exactly with what you have mentioned. I have also planned to do more tests on this in the near future. It would be a good test to compare the metal foil caps to the metallized polyester. I've done tests with caps before and they can make a difference. I don't expect the electrolytic caps in the x0xb0x to make any difference.

[hyphen nation]

As a tube amp enthusiast, I have been curious about the capacitors myself...nothing is spoken of in an almost mystical way as capacitors in the voodoo filled world of guitar amps. Check out the selection at Angela Instruments....I was going to either try and figure out which once were critical in my next x0x build, or just replace them all...

[bcbox]

if you want to try swappign the foil caps I would change only the ones in the audio signal path. C18, C19, 20, C21, C24, C25, C26, C27.

[hyphen nation]

if you want to try swappign the foil caps I would change only the ones in the audio signal path. C18, C19, 20, C21, C24, C25, C26, C27.

Hey Thanks! I thought I was going to have to figure that out on my own..

Would you swap any in your x0xi0 rear kit?

[bcbox]

Would you swap any in your x0xi0 rear kit?

no. there's no additional caps in the signal path except for the distortion.

[katarakt]

if you want to try swappign the foil caps I would change only the ones in the audio signal path. C18, C19, 20, C21, C24, C25, C26, C27.

Thanks for info bcbox! Maybe in my second x0x i'll use Panasonic FC capacitors for these points...maybe for the complete x0x, it depends on the price. I'm sure someone will be faster finishing a x0x with these caps, if so let us all know how it sounds.

FC.jpg (11.87 KiB) Viewed 3586 times

[3phase]

Some additional findings.. The panasonic BC´s was indeed a main source for the harder sound i was fighting against..

For a original 303 sound i recomend building the whole thing with standard electrolytic caps...

And when modding it with better quality caps , listen to it closely..and dont expect beneficial results when you dont have real highend ones at hand... The BC´s make a clear sound..but they actually dont sound smooth..rather hard and grainy...

I got better results than using standard electrolytics only when testing some bipolar elnas or golden roedersteins..what are booth highend audio caps..
there i had very beneficial results in the output and coupling stages.. clear and smooth.. not clear and hard..
Especially the big headphone out cap benefits from a highend cap..even when you have to stick it with heat glue somewhere on the board... Theese highend audio caps are usually huge...

But for the original 303 muffeling standard electrolytics are the best.

For the filter and everything envelope related caps i suggest to stick with standard ones because better caps can lead to a stiffer sound there.. the mushiness and elasticity of the 303 seems to be related to the cheap caps in theese stages...



Regarding the Xicon foilcaps in the filter section .. i checked with highend styroflex foil caps..

in position c20 c21 c25 and c27 they was highly beneficial getting a warmer sound..

for C18 c19 c24 and c26 they were "too good"..resulting in more high freq excess in resonant states, what i dont liked too much...

So i can state the type of foil caps is altering the sound and filter behaviour.. So sticking with the originals is the best you can do for the original 303 sound..while carefully checking other types can lead to good results too..
Question is : What are the original 303 foil caps?

Sofar i only was able to collect opinions regarding transparent green Xicons versus dark green Xicons..

technicans in my surrounding belive that they are different types because they have seen the transparent green ones only in high end hifi gear from japan while the dark green ones seem to be used in very cheap transistor radios all over the place...
But this can be accidental..the dark green Xicons are defenetly an old japanese standard


Maybe its just by accident that i ve green transparent Xicons in booth my original 303 and 606..But I checked a juno 106.and all transparent green Xicons..

Would be interesting to know if all 303´s have transparent Xicons or if there are also models that use the dark green Xicons...

If anybody on the list here that can have a look in its real 303 or 606 this would be interesting...

However.. i am more satisfied with the sound of my xoxbox now... defently much smoother and 303 ish now than on my first test run...


have to check a few mods now... my original 303 is modded aswell...

and than i can finaly close the box...

[3phase]

and regarding getting the green transparent Xicons.. i ve no idea..
maybe they are not manufactured anymore.. like many industrial specialized audio parts..
To source them you probably need to slaughter an old marantz amp, or alike.

But sofar its absolutly unclear wether there are different types of Xicons or not...

More people have to have a look in theire original 303´s... when they all have transparent ones there is the likely possebility that its a different type.. And after my tests i would expect them to sound different than...

[guest]

my 303 has transparent capacitors
a slight yellowish tinge if i recall
someone told me that they had a different dialectric
polystyrene or something like that
but im not completely convinced

[katarakt]

Some additional findings.. The panasonic BC´s was indeed a main source for the harder sound i was fighting against..

Hm, as my search i've read that the panasonic BC's gives some warm sound. Ok, maybe i'm wrong. If you say these are giving harder sound that's indeed something we don't want.

Excellent that you have the time testing those different things, respect

[bcbox]

All 303's and 606's I've tested have the transparent green types. This includes about fifteen 303's and four 606's I've had my hands on.