Q11 - 536 vs 945 tests

by phono on Thu Jun 18, 2009 3:03 pm

after alex_dubinsky discovered that using a 945 in Q11 instead of a 536 added a bit more metalic resonance i figured i would do some tests with the 945's that i have here to see what the difference was, must say i was plesantly suprised.

the test files are here
theres both 16bit and 24bit version for those of you who prefer higher quality

http://www.bahnhof.se/wb447909/phono/x0 ... -16bit.zip
http://www.bahnhof.se/wb447909/phono/x0 ... -24bit.zip


i recorded some takes with different betas and cut and pasted them together to make life easier to compare them, each wave has the same knob positions for all betas and the format of them is like so,

first you hear everything stuck together which is

2 loops of a pattern with a 536 (sorry i couldnt get my meter to read its beta since i clipped it out and the legs were too short to work in my meter)
2 loops of a 945 with a beta of 300
2 loops of a 945 with a beta of 287
2 loops of a 945 with a beta of 275

a small pause and then after this i do side by sides

536 vs 945 with a beta of 300 (2 loops of 536 then 2 loops of 945)

short pause

536 vs 945 with a beta of 287 (2 loops of 536 then 2 loops of 945)

short pause

536 vs 945 with a beta of 275 (2 loops of 536 then 2 loops of 945)

i did quite a few takes but i whittled it down to 3 waves since the difference is sometimes subtle, its very noticable when env/decay is up high, in my ears teh 945 sounds much better than the 536 in this position as alex stated. I'm leaning towards the lower beta (275) 945 but ive not totally decided yet. Lower beta 945s definately sound a little more squelchy in this machine. I should point out that the box im using to test has high gain 733AP in Q8,Q9,Q10 and 733P elsewhere so this may be coming in to play also.

All in all its quite satisfying to use a 945 at this position, well done Alex for discovering it. As most of you probably know the 954's were rumored to be in the later builds of the real 303's how true this is i don't know, but it might well accoutn for some tb's sounding better than others.

The 945's im using are silver faced (nec possbly?) and marked C945P W58

anyway give the wav's a listen and let us know what you think.

Alex's original thread is here

viewtopic.php?f=12&t=11245
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Re: Q11 - 536 vs 945 tests

by E:pp:ik on Fri Jun 19, 2009 8:09 am

Thanks for the post phono!

I can confirm the 945s in the 303s. My original TB has them and they're original factory parts.
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Re: Q11 - 536 vs 945 tests

by phono on Fri Jun 19, 2009 9:39 am

E:pp:ik wrote:Thanks for the post phono!

I can confirm the 945s in the 303s. My original TB has them and they're original factory parts.


cool so its true they used both 945 and 536, good to hear.
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Re: Q11 - 536 vs 945 tests

by E:pp:ik on Fri Jun 19, 2009 3:55 pm

Note the bottom left. It's the best shot I could get of a 945. Most are buried in the circuit.
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Re: Q11 - 536 vs 945 tests

by alex_dubinsky on Fri Jun 19, 2009 6:23 pm

Glad I could provide some insight. The discovery was made after a customer complained about the pops that sometimes happen on all 303's at the start of notes when res/cutoff/env are turned down. I examined a few x0x's I had onhand, and also an earlier unit (in fact one of the first) I had built that used 945 transistors that I'd been using for a/b reference testing. What I'd took note of was that the new 536 x0xes were much quieter with the knobs low, which contributed to the pop indeed being more noticeable and distracting. I decided to bite the bullet and rip apart both PCBs, swapping transistor by transistor and comparing the sound at each step. This wasn't the only difference I was trying to get to the bottom of. The new 536-based x0xes also sometimes (though not always) had lower resonance and cutoff range, with less vibration on max. This really frustrated me, because I could hear it in the a/b testing, but it was subtle, and it seemed to vary from note to note. (In fact, playing notes repeatedly would boost resonance and vibration, making the sound equivalent with the old x0x's, making me question whether I was hearing anything at all. I called the whole thing the first-note problem.) I tried swapping what I'd thought were the most important components, the 2291's and the 1583's, which had come from a few different suppliers, and the Q10s and Q9s, with no results (except delays). I hadn't suspected the root of the problem was the switch to the much more expensive 536's. But eventually I decided to just go ahead and start swapping every single transistor. Thankfully, though, I didn't end up swapping even half. I was really relieved when I listed to the x0x after Q11 was swapped. It wasn't a subtle change, it wasn't like I feared where it was several components contributing to the differences and teasing out which ones it was would involve looking out for many small shifts. That was it.

Now, what I wonder is that is this simply an issue of beta, or does the full curve of the transistor play the difference. Man, I would really like to acquire a curve tracer. Or go ahead and construct my own (with PC uplink and all that jazz).
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Re: Q11 - 536 vs 945 tests

by lord.bix on Mon Jun 22, 2009 6:48 am

Hi Phono, Hi Alex,

damn.. This difference is realy noticable. I am impressed. I realy was wondering why my xox'es had this little "dead" sound in comparision to the 303 i have in my studio. Now i know why. The 303 has 945'ies in them. The wobbling sound, which i realy like, is more noticable with the 945'ies.

For god sake i soketed them in my boxes..

What di you think, should i change all 536'ies to 945's?

/Marco
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Re: Q11 - 536 vs 945 tests

by phono on Mon Jun 22, 2009 11:08 am

lord.bix wrote:Hi Phono, Hi Alex,

damn.. This difference is realy noticable. I am impressed. I realy was wondering why my xox'es had this little "dead" sound in comparision to the 303 i have in my studio. Now i know why. The 303 has 945'ies in them. The wobbling sound, which i realy like, is more noticable with the 945'ies.

For god sake i soketed them in my boxes..

What di you think, should i change all 536'ies to 945's?

/Marco


dont forget the machine in this example also has 733AP at the key points, so id start at q11 and see how that works out first
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Re: Q11 - 536 vs 945 tests

by lord.bix on Mon Jun 22, 2009 2:08 pm

Hi Phono,

have one machine fully stuffed with AP's (all positions) and another 2 with P's. Had no time to change the other 2 ones. I wanted to do some tests anyway, how AP's work out in different positions (i know there were some tests even with k).. if i would have time.. lol

Thanks in advance

/Marco
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Re: Q11 - 536 vs 945 tests

by ripe909 on Sun Feb 14, 2010 12:44 pm

Just to add to this, I have an original 303 with a different part used: C1685

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It doesn't sound as good as another 303 I have that is a 945 box.


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Re: Q11 - 536 vs 945 tests

by dj_metronome on Sun Feb 14, 2010 10:16 pm

interesting... do you think this might be the result of a repair?
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Re: Q11 - 536 vs 945 tests

by ripe909 on Sun Feb 14, 2010 10:26 pm

Not from the looks of it, the solder joints look original and the same part is used throughout the machine.

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Re: Q11 - 536 vs 945 tests

by phono on Mon Feb 15, 2010 3:15 pm

very interesting, can i use your image for a post on my blog?
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Re: Q11 - 536 vs 945 tests

by ripe909 on Mon Feb 15, 2010 3:18 pm

sure thing, feel free to use it!

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Re: Q11 - 536 vs 945 tests

by phono on Mon Feb 15, 2010 3:34 pm

ripe909 wrote:sure thing, feel free to use it!

cheers
ripe


excellent thanks
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Re: Q11 - 536 vs 945 tests

by phono on Mon Feb 15, 2010 3:43 pm

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