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Old 17th January 2007, 07:05 PM   #1
danielm is offline danielm  United States
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Default LF351 substitute

I am working on an old vintage mixing console which uses the 'discontinued' LF351.

http://cache.national.com/ds/LF/LF351.pdf

I have a tube full of LF356 which looks to be a good sub. Any thoughts? Other suggestions?

http://web.mit.edu/6.301/www/LF155.pdf

Each of the balanced mic channels are transformer coupled input connected to selected NE5534 then the LF351.
I just finished digging into one of the potted transformers and was able to repair it.
Now I find a few bad LF351 discontinued parts.

Cold weather projects...
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Old 17th January 2007, 08:08 PM   #2
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Yes I've got one comment re:LF356. I seem to recall that Walt Jung did an article on op-amps in the 1970s and there was a discussion of slew rate and sound quality etc. I'm pretty sure that he didn't like the LF356 and I believe it was something to do with the circuitry where there was some sort of "enhanced" design. Anyway it wasn't just subjectivism. He gave his reasons. The article was in "Audio". I'll check his website as he's got some of his material there. Again from memory the Texas "071" series got better auditions.
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Old 17th January 2007, 08:25 PM   #3
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Hi danielm. I just done my "homework" You'll find the reference if you chase up the following. Put "Walt Jung's website" in Google. then go to "Library" on the LHS, then "Classic Articles" There is stuff from AA which would almost certaintly cover it but the thing I recalled is in a three part art' called "An overview of SID and TIM" AUDIO 1979 co-authored with Stephens and Todd. The listening tests are summerized on page 9 of the second section IE Part II (It was "asymetry" that was the issue.)
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Old 17th January 2007, 11:18 PM   #4
danielm is offline danielm  United States
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Thanks Jonathan. I remember Walt Jung's articles from yrs past.

Interesting reading.

I'm not sure what to look for now that I can't find the 351. The TL071, 084, NE536 and the OPA134, although it may get a bit pricey, all look to be suitable candidates.
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Old 17th January 2007, 11:54 PM   #5
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I'm intrigued to see on the page I mentioned that the far left column list a number of op-amps that appear "transparent" on listening tests. I'm sure you've seen some of the comments that are passed on the sonics of various electronics in this forum and while I am sure that there are differences I think some of the reactions could have been submitted to a creative writing contest. Sorry, I'm just going thru' a "bitter and twisted" phase. There is an "Audio grade" model in the 071 series from TEXAS isn't there? That will be new since the Jung art. Best wishes, Jonathan
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Old 18th January 2007, 01:28 AM   #6
danielm is offline danielm  United States
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So far I have two input channel strips installed and going. In one I installed a 351, the other a 356.
Panned one left one right and listened to a variety of music.
I noticed when driven hard the 356 is less... open sounding. Maybe a tad less detail.
I swapped ears (headphones) to verify. It is ever so slight and if didn't know it would be a tough call.
I have sockets so its easy enough to try a few different ones.

I did find one strip oscillating. Closer inspection with the scope revealed it was a 357 (LM357, not the firearm) in place of the original 351. A 356 solved this problem.

I'm OK with the performance of the 356 in a couple or more chans that need them. I will be using this for FOH live.
I think it will be a good console for hostile RF environments with its transformer inputs.

We'll, I better get back to it...
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Old 18th January 2007, 02:49 AM   #7
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it wasn't difficult to blow the early JFET opamps -- easily substituted with parts from Analog, Texas Instruments etc.
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Old 18th January 2007, 03:13 AM   #8
Leolabs is offline Leolabs  Malaysia
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TLO71 is a good head start.
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Old 18th January 2007, 03:13 AM   #9
lineup is offline lineup  Sweden
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Default Tle2071 Tl051 Tl071 Lf351

Quote:
Originally posted by Jonathan Bright

There is an "Audio grade" model in the 071 series from TEXAS isn't there?
That will be new since the Jung art. Best wishes, Jonathan

Jonathan,
maybe you refer to this one:

The best direct upgrade replacement for TL071 from Texas
would be TLE2071 ( TLE207x )
http://focus.ti.com/docs/prod/folder...t/tle2071.html
http://focus.ti.com/lit/ds/symlink/tle2071.pdf
Quote:
* Direct Upgrades to TL05x, TL07x, and
TL08x BiFET Operational Amplifiers
* Greater Than 2 Bandwidth (10 MHz) and
3 Slew Rate (45 V/μs) Than TL07x
* The TLE207x family of BiFET amplifiers are Texas Instruments highest performance BiFETs, with tighter input offset voltage and ensured maximum noise specifications.
Texas also has got the TL051 ( TL05x ).
But in my opinion TL051 is not very much of an upgrade for TL071.
Anyway, very slightly better data, if looking to specs only.


And, of course, if answering this topic,
TLE2071 would be a very good replacement for LF351, too.



Regards
lineup
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Old 18th January 2007, 07:17 AM   #10
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Hi danielm, I'm interested in the 357 causing problems. Again I'm working from memory but I think the LF357 is not stable at unity gain whereas the 356 is compensated appropriately. Would that make sense of your recent experience?
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