Hey Guys,
during my buildup of the x0xb0x I ran into a fake 2291 transistor and hacked a rude replacement from 2*BC337A together in order to continue soldering while waiting for the replacement to arrive. Now the x0x is complete and I have compared both solutions. Without going into frequency spectrum analysis and in detail comparison - they do sound pretty much the same to me. Perhaps I am not very picky about that, but I thought this might be something worth sharing here with you.
I have uploaded a short test-sequence over at Soundcloud using both variations if you want to check it out yourself:
https://soundcloud.com/pulsar/x0xb0x-2xbc337a
https://soundcloud.com/pulsar/x0xb0x-2sc2291
Original 96kHz WAV files should be downloadable as well.
Cheers!
Possible 2SC2291 Replacement
Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers
Please be positive and constructive with your questions and comments.
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Re: Possible 2SC2291 Replacement
Would this trick also work with 2* BC547 ?
- pulsar256
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Re: Possible 2SC2291 Replacement
The BC547 have a lower ß, no Idea how this would affect the sound. Just give it a try.
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Re: Possible 2SC2291 Replacement
Okay can't I harm anything else ? Because I'm working on a a tb303 with the same problem as described in these topics:
http://forums.adafruit.com/viewtopic.ph ... 3&p=169937
http://forums.adafruit.com/viewtopic.php?f=12&t=30490
I just want to test if it's the 2SC2291 that's broken with some transistors I have in stock (BC547 in this case) before ordering a 2SC2291.
http://forums.adafruit.com/viewtopic.ph ... 3&p=169937
http://forums.adafruit.com/viewtopic.php?f=12&t=30490
I just want to test if it's the 2SC2291 that's broken with some transistors I have in stock (BC547 in this case) before ordering a 2SC2291.
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- Posts: 208
- Joined: Wed Sep 19, 2012 8:11 am
Re: Possible 2SC2291 Replacement
Just from a quick listening I`d say it sounds like the filter slope is less steep with the replacement. At least it`s obvious there is more high frequencies left over for a given center freq. The point now is, for me personally it sounds BETTER like this. I mean I`m constantly trying to add brights to the signal using distortion, bitcrushing and all of that, so this mod sounds pretty much like useful for me. I think I`ll also make this optional in my xox. Thanx for sharing!
- pulsar256
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- Joined: Mon Apr 01, 2013 8:22 pm
Re: Possible 2SC2291 Replacement
if you do not mess up the polarity or introduce shorts - I don't see how you could break anything. Did you test your 2291 with a transistor- or a diode-tester? At least you can test the PN junctions with a multimeter in the diode-mode. Chances are this is a knockoff and has a completly different pinout. I did also have this pleasure: http://www.adafruit.com/forums/viewtopi ... 12&t=38575Arnoid wrote:Okay can't I harm anything else ? Because I'm working on a a tb303 with the same problem as described in these topics:
http://forums.adafruit.com/viewtopic.ph ... 3&p=169937
http://forums.adafruit.com/viewtopic.php?f=12&t=30490
I just want to test if it's the 2SC2291 that's broken with some transistors I have in stock (BC547 in this case) before ordering a 2SC2291.
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- Posts: 21
- Joined: Thu Sep 28, 2006 3:27 am
Re: Possible 2SC2291 Replacement
Nope I didn't gonna solder it out tonight and I'll test it with a diode tester I don't have a transistor tester.pulsar256 wrote:if you do not mess up the polarity or introduce shorts - I don't see how you could break anything. Did you test your 2291 with a transistor- or a diode-tester? At least you can test the PN junctions with a multimeter in the diode-mode. Chances are this is a knockoff and has a completly different pinout. I did also have this pleasure: http://www.adafruit.com/forums/viewtopi ... 12&t=38575Arnoid wrote:Okay can't I harm anything else ? Because I'm working on a a tb303 with the same problem as described in these topics:
http://forums.adafruit.com/viewtopic.ph ... 3&p=169937
http://forums.adafruit.com/viewtopic.php?f=12&t=30490
I just want to test if it's the 2SC2291 that's broken with some transistors I have in stock (BC547 in this case) before ordering a 2SC2291.
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- Posts: 208
- Joined: Wed Sep 19, 2012 8:11 am
@ pulsar: Do you think you could give us another comparing audio file example, with looooong straight notes (0%, 50%, 75%, 100% reso), so we can check whats actually happening in freq domain? Talked to another guy and he agreed on that it actually sounds better, he thinks the same about the need to have brightness added for contemporary mixes. Thanx!
- pulsar256
- Posts: 42
- Joined: Mon Apr 01, 2013 8:22 pm
Re: Possible 2SC2291 Replacement
sure, give me a minute so set it up.
- pulsar256
- Posts: 42
- Joined: Mon Apr 01, 2013 8:22 pm
Re:
mario1089 wrote:@ pulsar: Do you think you could give us another comparing audio file example, with looooong straight notes (0%, 50%, 75%, 100% reso), so we can check whats actually happening in freq domain? Talked to another guy and he agreed on that it actually sounds better, he thinks the same about the need to have brightness added for contemporary mixes. Thanx!
http://machschnellgeld.de/2sc2291-vs-2b ... 0xb0x.xrns
If you do not use renoise (http://renoise.com) open the xrns with 7zip/winzip/<whatever>zip, you will see what is going on. The samples are flac/96khz/32bit. Audacity fu**** it up when opening these. Foobar doesnt.
setup:
- tm3 tuned for maximum, so the filter opens as much as possible. I am using a cuttoff-range mod to compensate for this. all mods are disabled!
- altering non accented and accented notes with same settings before lowering the resonance to the next step.
- tune: 50%
- cuttoff: See sample-name (c100,c75,c50)
- resonance: [100, 75, 50, 25, 0]
- env mod: 50%
- decay: 50%
- accent 50%
- pulsar256
- Posts: 42
- Joined: Mon Apr 01, 2013 8:22 pm
Re: Possible 2SC2291 Replacement
... and made another one with much better audible filter sweeps:
http://machschnellgeld.de/2sc2291-vs-2b ... x_2nd.xrns
This time with:
- tune: 100%
- cuttoff: See sample-name (c100,c75,c50,c25,c0)
- resonance: [100, 75, 50, 25, 0]
- env mod: 100%
- decay: 100%
- accent 0%
- non-accented notes
- no EQing (sorry, forgot to zero the EQ in the last take)
http://machschnellgeld.de/2sc2291-vs-2b ... x_2nd.xrns
This time with:
- tune: 100%
- cuttoff: See sample-name (c100,c75,c50,c25,c0)
- resonance: [100, 75, 50, 25, 0]
- env mod: 100%
- decay: 100%
- accent 0%
- non-accented notes
- no EQing (sorry, forgot to zero the EQ in the last take)
-
- Posts: 208
- Joined: Wed Sep 19, 2012 8:11 am
Re: Possible 2SC2291 Replacement
Thanx!
I took one of the files (after having a hard time with those flacs) with no reso and analyzed one waveform.
With the mod, the filter slope is 12db/Oct (see pic). I dont have my xox at hand to compare, but I would be surprised if the original filter is not of that -18db/Oct kind that it`s told to be.
I only have a rough understanding of analogue electronics, so what does this mean? Obviously the last stage of the filter now isnt actually filtering, or what? Shouldnt there be an easier way to get the 12 db signal, maybe by picking up the signal before 2291? Or what? Opinions, anyone?
I took one of the files (after having a hard time with those flacs) with no reso and analyzed one waveform.
With the mod, the filter slope is 12db/Oct (see pic). I dont have my xox at hand to compare, but I would be surprised if the original filter is not of that -18db/Oct kind that it`s told to be.
I only have a rough understanding of analogue electronics, so what does this mean? Obviously the last stage of the filter now isnt actually filtering, or what? Shouldnt there be an easier way to get the 12 db signal, maybe by picking up the signal before 2291? Or what? Opinions, anyone?
- Attachments
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- XOX.png (43.86 KiB) Viewed 4406 times
- antto
- Posts: 1636
- Joined: Thu Apr 15, 2010 3:21 pm
Re: Possible 2SC2291 Replacement
i haven't listened to anything (why flac.. )
Mario: skip that thing with the slope
if you hear a 4-pole filter with a 24dB slope, and then the same 4-pole filter with a 18dB slope - the difference is slim
as for trying to measure the said slope from the output like with that spectrum scope - that's.. not the right way
how did you calculate that it's 12dB from that image?
EDIT: i see, you've indicated that if at that given frequency the amplitude is -20dB, 3 octaves up it's roughly -56dB
and (-56--20) = -36, divided by 3 = -12
except that this is wrong, because the original input is not flat in the frequency domain.. it's a sawtooth (or worse, an irregular square)
Mario: skip that thing with the slope
if you hear a 4-pole filter with a 24dB slope, and then the same 4-pole filter with a 18dB slope - the difference is slim
as for trying to measure the said slope from the output like with that spectrum scope - that's.. not the right way
how did you calculate that it's 12dB from that image?
EDIT: i see, you've indicated that if at that given frequency the amplitude is -20dB, 3 octaves up it's roughly -56dB
and (-56--20) = -36, divided by 3 = -12
except that this is wrong, because the original input is not flat in the frequency domain.. it's a sawtooth (or worse, an irregular square)
- pulsar256
- Posts: 42
- Joined: Mon Apr 01, 2013 8:22 pm
Re: Possible 2SC2291 Replacement
First time I come across ppl having problems with flac in a audio forum So, how about a ARJ File with all the samples as WAV? Ok, just kidding. It's a ZIP File:
http://machschnellgeld.de/x0xb0x-2sc229 ... bc337a.zip
as a bonus I've also added audio samples of an modified filter section (devilfish-ish filter overload, resonance boost, cuttoff boost)
http://machschnellgeld.de/x0xb0x-2sc229 ... bc337a.zip
as a bonus I've also added audio samples of an modified filter section (devilfish-ish filter overload, resonance boost, cuttoff boost)
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- Posts: 208
- Joined: Wed Sep 19, 2012 8:11 am
Re: Possible 2SC2291 Replacement
Yeah, stupid me. Should have started to think before doing that calculation.
Anyway, any opinion what actually is going on with that mod? I think it`s obvious that for the comparing files, that mod has the same resonance peak, but there is more high frequencies left over "right" of the reso peak. And this does sound like a lower steepness of the filter, or not?
Anyway, any opinion what actually is going on with that mod? I think it`s obvious that for the comparing files, that mod has the same resonance peak, but there is more high frequencies left over "right" of the reso peak. And this does sound like a lower steepness of the filter, or not?
Please be positive and constructive with your questions and comments.