Fade 1.4 vs previous versions: op-amp choice

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fragletrollet
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Fade 1.4 vs previous versions: op-amp choice

Post by fragletrollet » Mon Jun 28, 2021 12:44 pm

Hey,

gonna build some Fade modules, and although I can't find a schematic I noticed from the BOM that the 1.4 version only uses the TL072/74 while the older version, as with Shades, uses LME49720, I suppose for the mixbuss? the LME is a dual while the 074 is a quad, I'm guessing this is the IC in question? Why the change of component?

I will primarily use the modules for cv, so I suppose the 07x is just fine. But I have a Manhattan Mix with the LME, and it sounds great (nothing at all, just clean) and I would guess the Fade's mixer is just a simple inverting + fader booster setup.

Any input? :hmm:

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Re: Fade 1.4 vs previous versions: op-amp choice

Post by fragletrollet » Mon Jun 28, 2021 12:46 pm

So I had a look in the Atn8 build manual, and lo and behold, LME49743 is listed as a possible upgrade for the TL074. Guess that applies here aswell!

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Re: Fade 1.4 vs previous versions: op-amp choice

Post by fragletrollet » Sun Jul 11, 2021 5:53 pm

Unfortunately not available in soic14. I see OPA1604AIDR, but pretty costly...

Wonder the sense in changing the pcb layout for soic14 compared to the tssop14 used earlier, where the 49743 is widely available at about half the cost.

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Re: Fade 1.4 vs previous versions: op-amp choice

Post by fragletrollet » Sun Sep 05, 2021 11:24 am

Okay so I went ahead and built up 5 of my 8 Fade modules, with OPA 1604's and 2134's.
A schematic would be really helpful as I am uncertain if both op-amps are in the audio path or if the 2134 is wasted on straight CV duties, in which case they might be better used elsewhere.

I have had problems with erratic resistance readouts on a couple of the modules, after some confusion after having reheated all joints I narrowed the fault down to the fader being broken, and after replacing it this was confirmed. I got the fader caps that looks like the ones Antumbra uses, and as no specific part number is listed and ebay is referenced as source it's hard to say if I got the exact same ones, although they look exactly the same. They are branded as AKAI APC40 replacement caps. However, the fit very tightly on the Bourns sliders, and if you install them by simply pushing them onto the faders the pressure will bend the pins between the internal slider and the carbon track underneath, which causes erratic and intermittent fader behavior. Holding the fader actuator with pliers while installing the caps helps as the pressure should apply to the pliers instead of the internal bottom surface (carbon track) of the fader. However this way it is very hard to properly seat the fader caps and get an uniform look between the modules. I got some other fader caps (in a local store, I think they are the Roland caps for the Aira ecosystem, that slide much gentler onto the bourns faders, but I really prefer the look of the original intended caps).

Are there other faders that fit the pcb's other than the Bourns? Would be nice to be able to use higher quality faders from ALPS or similar.

Any feedback is greatly appreciated.

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Re: Fade 1.4 vs previous versions: op-amp choice

Post by fragletrollet » Fri Sep 24, 2021 12:32 pm

The amount of responses and interest in the thread is mind boggling. Sent several e-mails directly to Antumbra trying to at least get my hand on a schematic for this and ATN8 but no answer. Why bother having contact info...

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