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The Passinwind Open Source Preamp

#227
BassLife77 said:
did you burn out your free samples? I got 2 of each from Linear Tech with free shipping. I got it in 3 days
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I've long since gone that route, but LT has been out of stock for one or the other for quite a while now anyway. Normally I just buy from them, although their shipping cost is pretty high and you need to buy pretty many to make it worthwhile. I haven't checked their stock in the last week or so though, FWIW.
 
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#228
Passinwind said:
What's the hangup? Digikey are showing both the LT1351 and LT1352 as being in stock for immediate delivery in my current cart view.
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Got the 1351s immediately. The order said the 1352s were on b/o.

And...just looking I see the LM1352CN8#PBF-ND I did a cut & paste from the project BOM is still backordered, whereas the LT1352IN8#PBF-ND you're probably looking at is in stock.

So I guess I'll just wait a bit since we're already getting close to the 4 week lead time DigiKey is saying and I have a lot on my plate for the next two weeks. Besides, if I ever want to play an outdoor gig in freezing weather, the CN8 will work down to 0 centigrade - so I'm all set! Woo-Hoo! :laugh:
 
#229
40Hz said:
Got the 1351s immediately. The order said the 1352s were on b/o.

And...just looking I see the LM1352CN8#PBF-ND I did a cut & paste from the project BOM is still backordered, whereas the LT1352IN8#PBF-ND you're probably looking at is in stock.
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Nope, but it turns out that Digikey's cart system was lying to me. If I enter a new order they are saying March 28th though, which isn't too far away at least.
 
#230
Passinwind said:
Nope, but it turns out that Digikey's cart system was lying to me. If I enter a new order they are saying March 28th though, which isn't too far away at least.
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Yeah. Ran into that with my order too. Both said they were in stock. It wasn't until I actually ordered that it said one was out of stock and backordered. Which I thought was kinda cute. Also brought back some old memories about why I tend to try to avoid doing business with DigiKey.
 
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#231
Passinwind said:
Sneak peak at the 2-band spinoff, which measures 1 1/3" by 1 3/4":

PW1B.jpg


I'll do a test stompbox install right quick, but I don't expect many surprises with this one.
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So wait - is the two-band spinoff an actual thing yet? Or is it still in R&D?

And what's this trade off you speak of? Would it loose the super cool swept treble section?
 
#232
40Hz said:
Yeah. Ran into that with my order too. Both said they were in stock. It wasn't until I actually ordered that it said one was out of stock and backordered. Which I thought was kinda cute. Also brought back some old memories about why I tend to try to avoid doing business with DigiKey.
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Roger that. I'm going to get in touch with my local LT rep and see if he can do anything for us. I'll also start testing alternative parts ASAP.
 
#233
Freekmagnet said:
So wait - is the two-band spinoff an actual thing yet? Or is it still in R&D?

And what's this trade off you speak of? Would it loose the super cool swept treble section?
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I've only built up one test board so far. It's in the bass shown in post #181 and has been working flawlessly. There's no treble control at all, just bass and mids. I'd guess that share arrangement might be a month or so out, since I want to wrap up the original one's build Wiki first, and we need a few more builds done by other people in the wild to vet the design properly. ric426 ran into a few unexpected glitches and he and I are still working on ironing those out right now.

I tried a layout for just the LPF section but it came out a bit larger than I expected. So another try is in the queue, but it's likely to be at least a few weeks before I get to it.
 
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#234
Passinwind said:
... I'll also start testing alternative parts ASAP.
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I was going to ask how critical are these LT135X op-amps.
I'm thinking about building the preamp on a prototype PCB (to mount in an external box) and I'll use the JFET op-amps I already have (e.g. TLE2062/072, OPA2134, LF442 etc.) Other than current consumption and noise, I don't think preamp performance will be different.
 
#235
Passinwind said:
Roger that. I'm going to get in touch with my local LT rep and see if he can do anything for us. I'll also start testing alternative parts ASAP.
Click to expand...

No rush AFAIC. Tomorrow it gets nutty for me for the next two weeks so I doubt I'll have the time to sit down to it even with the parts.

I also found out this morning that my soldering station has gotten annoyingly wonky, so I'll probably be looking at replacing that too before I do anything. But no worries. I've been jonesing for a new one anyway.
 
#236
ex-tension said:
I was going to ask how critical are these LT135X op-amps.
I'm thinking about building the preamp on a prototype PCB (to mount in an external box) and I'll use the JFET op-amps I already have (e.g. TLE2062/072, OPA2134, LF442 etc.) Other than current consumption and noise, I don't think preamp performance will be different.
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The 1351 and 1352 are bipolar oddballs, and there's a good chance that something like a 2134 will actually sound better if you don't mind only getting around 1/16th of the battery life. I haven't yet been able to identify any viable sub for the 1351/1352 pair given my own priorities, but I'm definitely all ears.
 
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#237
Passinwind said:
The 1351 and 1352 are bipolar oddballs, and there's a good chance that something like a 2134 will actually sound better if you don't mind only getting around 1/16th of the battery life. I haven't yet been able to identify any viable sub for the 1351/1352 pair given my own priorities, but I'm definitely all ears.
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Sounds like that might be a better solution for pedal builds then. Would a pair of 2134s replace both the 1351 and 1352 just by dropping them into the sockets in the existing circuit? If so, I may go that route instead.
 
#238
If you're going to run it externally as a pedal with a 9V adapter however…

Hmm…maybe an alternative chip that's technically capable of higher audio quality for use purely as a pedal might be interesting. Also be interesting to see if it makes a noticeable audible difference in real use.
 
#239
lakefx said:
Sounds like that might be a better solution for pedal builds then. Would a pair of 2134s replace both the 1351 and 1352 just by dropping them into the sockets in the existing circuit? If so, I may go that route instead.
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Nope, OPA2134 and 2132 are dualies, and you need a single for the second slot. OPA 134 is the single version of the 2134. There are many other possibilities as well, but many of my favorites are SMT-only, and to my mind having to use adapter boards is not very appealing.
 
#240
Passinwind said:
Nope, OPA2134 and 2132 are dualies, and you need a single for the second slot. OPA 134 is the single version of the 2134. There are many other possibilities as well, but many of my favorites are SMT-only, and to my mind having to use adapter boards is not very appealing.
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I have very little experience with any of these, but looking at the pinouts, it looks like a 134 would replace the 1351 and a 2134 would replace the 1352. Would the rest of the circuit need to be overhauled too? I'm just trying to decide if it's worth trying to sub the LTs out given my lack of full understanding.
 

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