Parts sourcing... two qustions

1. I’m searching for LM13700 OTA at Digikey.
“LM13700N-ND” are not available.
I serached for “LM13700” and found those:

http://www.digikey.de/product-detail/de/LM13700N%2FNOPB/LM13700N%2FNOPB-ND/228996

do they work as well?

2. In Eurorack Land, we like to change the TL074 with a better one for improved audio quality.
this one works fine: LME49740
All I know is that it draws more current.
Would it improve audio quality? is it necessary ? and would it be ok because of drawing more current

thanks a lot for your help

1: Yes.
2: Maybe. It has better data than the TL074, replacing the Opamps is a step, but not necessarily a panacea. It won’t hurt, but maybe try in a few modules, be sure to A/B listen before you go all in.

You have to start with a good, well-filtered PSU, all metal film resistors in the audio path, the right kind of caps, short cable runs, optimized PCB layouts and a whole lot of other things. It’s a holistic adventure. You can do lots of things and it won’t automatically translate into a more “hi-fi” sound. The law of diminishing returns applies as always.

thanks for your reply.
re 2.: you’re right, you have to listen, if it makes a positive difference in sound quality. I changed some in vca’s and mixers. I tried some filters and the filter didn’t sound the same anymore - so I didn’t change

If it won’t hurt the voice cards, I will try, as I order them anyway for my modular

Op-amp swapping is a joke in this context (and most of the time indeed…). What’s the point of getting the supposedly improved signal fidelity of the LME49470 for a signal that is distorted and colored by OTAs? Any noise/distortion added by the TL074 is hard to perceive compared to the noise/distortion introduced by the other elements.

I found this series of articles interesting on the subject of opamps here

I don’t know. It’s very esoteric.
It might be that the sound becomes more clear… better S/N… distorts not so fast… what do I know :smiley:
I changed some in my vca’s and audio mixer, as well A-119 and panning module.

I’m not sure that it is really desirable to have a filter that distorts less ; and anyway, the part responsible for most hiss and distortion issues is the lm13700.
If you want something cleaner, you better go for 4P filters.

Hmm, LM13700 are badged as TI parts now, bye bye national semi :frowning:

changing parts may not influence the sound character of course. I have already made that experience with a doepfer filter. changed the TL074 and sounded not that nice at all anymore.
but if you can just improve the audio signal path, I’m in!

well, I think, this might be a dispensable discussion, especially for the MI stuff. I trust in Oliviers work and am completely satisfied with my two shruthi’s

You could make more impact by replacing the 13700s. Chances are you would have to perform major surgery as you replace central parts of what makes things tick. If you look at compressors there’s the option of modding the Alesis 3630 using pin-compatible RMS detectors and VCAs in SIP packages from THAT corp instead of the old dbx originals. Presto, it will sound nicer!

If you design something from scratch the THAT2180 is a very nice VCA, but it’s not economical or efficient in terms of PCB real estate and power use in a poly synth or a mono with a decently complex signal path. Or you can use some old CA3280 if money’s no object or you require hideous precision for esoteric Ian Fritz (that guy’s a genius!) designs. I love the Threeler, Teezer and the Wavolver. Must try his chaos circuits one of them days.

Wheres the benefit in replacing some TL07xs to make your Synth sound more HIFI if you run it thru gear that has - TADAAAAAA! - mostly TL07xs or worse in it?

Its like polishing your exhaust tubing from the inside while driving with off road tires on a race track.

I suppose that Youkon uses “hifi” gear around, or that he has modified his gear in that direction.
Anyway, if you really want to replace the tl074s and like to throw money away (since, again, it’s going to have no impact except a worse power cunsomption, which is not really a nice thing with the ambika), you can try Burr Brown opamps.
Maybe a good place where you could use an audiophile part is the mixer, with an opa2134 (the only opamp on the mobo).

no no, forget it, guys! will do nothing.
I’m just one of these audiophile guys hating noisefloor and loving unmuddy crystal clear sound.

as I said, I’m completely satisfied with my shruthis. was just asking, as I’m a noob in building

I’m temporarily using a british filmmixer ad-149 from audio developments and headphones for about 500 from ultrasone …according to audiophile

but before I “waste” money for esoteric stuff, I prefer to buy new synths or modules for my eurorack :slight_smile:

can I perhaps interest you in an oxygen free 2 ga. size 1m power cable? I am having a sale right now at 999 euro each. Wont last long at that price

is it published with virgin fairies pubic hair at full moon? the connectors forged by islandic dwarfs? are the single leads active electron anti coriolis woven pattern?

@ altitude

you could offer me two AT24C512B :wink: these are needed

you might laugh, I really started to upgrade my cables :smiley:
but you don’t need them in every place. And until now, there’s no single cable in my studio which costs more than 100 euro and I hope this will stay so for long
as I said - better buying lots of synth stuff

ps: I ordered all parts for my 6 voice Ambika on Monday night at Digikeys and already today, I got a phonecall from UPS Germany - unfortunately they wanted my EORI first - which I haven’t yet and takes about two weeks to get it… grrrrrrrr
but hey! Digikeys really fast

now, to start to derail(TM by fcd72) my thread :smiley:

@fcd - did you already make the instrument definition for the shruthi in your Cirklon?
yesterday, I had awsome fun modulating my shruthi with the Cirklon

I posted a CKI file in the cirklon forum, but some parameters seem to be faulty, have to check it and replace it

@youkon
atm I’m having more fun modulating my anushri with the exfilinator… but ill have to solder a breakout panel so i can modulate it with the BigC as well. I might fell the need for a CV Patchbay…

oh, yes
I’m almost only CVing! so much fun
"http://dmachinery.files.wordpress.com/2013/01/8367179913_65fb4127ce_c.jpg"
looks quite interesting! your own work?

@youkon
roger that. I wanted to drive my favorite Synth with the Exfilinator - and Shruthi is better served by MIDI than by CV.
BTW every time i think about buying some EuroModules i make the mistake of counting in a MIDI Interface - and every time i am so lucky when i discover i have the BigCThing™ with CVIO! :-))))