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Topic: Yet Another Chip Mod Question(s) |
Jack Stanton
From:
Somewhere in the swamps of Jersey
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Posted 18 Sep 2017 9:11 am |
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1.Is it correct that Texas Instruments bought Brown Burr, and so theoretically they one and the same?
2. Mouser's website shows 4 different OPA1642 chips, each with a different letter suffix. I'm assuming there's a difference, but you know what happens when you assume..
3. In previous threads Ken Fox mentioned that he doesn't change the IC for the reverb as it may self oscillate. Can anyone enlighten me as to which one is for the reverb?
I'll take my answer off the air.... |
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Bob Metzger
From:
Waltham (Boston), MA, USA
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Posted 18 Sep 2017 9:57 am
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What type/model amplifier or effects unit are you asking about?
Bob M.
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Bob M. |
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Jack Stanton
From:
Somewhere in the swamps of Jersey
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Posted 18 Sep 2017 9:59 am
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| Sorry, Nashville 400 |
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Steven Paris
From:
Los Angeles
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Posted 18 Sep 2017 10:15 am Re: Yet Another Chip Mod Question(s)
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| Jack Stanton wrote: |
1.Is it correct that Texas Instruments bought Brown Burr, and so theoretically they one and the same?
2. Mouser's website shows 4 different OPA1642 chips, each with a different letter suffix. I'm assuming there's a difference, but you know what happens when you assume..
3. In previous threads Ken Fox mentioned that he doesn't change the IC for the reverb as it may self oscillate. Can anyone enlighten me as to which one is for the reverb?
I'll take my answer off the air.... |
1. Yes, TI owns Brown-Burr
2. The OPA suffixes AIDGKR and AIDGKT are VSSOP-8 packages--VERY small. Avoid unless you are an experienced surface-mount solderer. The only difference I can see between the AID and AIDR suffixes (both are SOIC-8 packages) is the packaging quantity (75 vs 2500) and the price ($4.00 vs. $3.33). So I'd stick with the AIDR.
3. The IC for reverb drive is U5B in a Peavey Nashville 400. I believe the reason for possible oscillation is that the power supply bypass cap FOR THIS IC ONLY is much farther away than ideal, and farther away than any of the other ICs. An 0.1 cap soldered between pins 4 and 8 on the solder side of IC 5 should cure this.
Keep in mind that if you are replacing the socket-mounted chips that you will need an SOIC-to-DIP adapter board (https://www.sparkfun.com/products/13655) for EACH OPA1642 IC.
The OPA1642 does offer slightly superior specs to an OPA2134; but the 2134 is available in a traditional DIP-8 package which, the 1642 is NOT. Whether this difference is audible or not in a steel guitar amplifier is open for question. The 2134 will simply pop into a DIP socket and therefore might be the better choice. BOTH of these chips are VASTLY superior to the stock RC4558 chip.
_________________
Emmons & Peavey
Last edited by Steven Paris on 18 Sep 2017 10:23 am; edited 1 time in total |
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Jack Stanton
From:
Somewhere in the swamps of Jersey
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Posted 18 Sep 2017 10:18 am
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Steven,
Thank you!
2134 it is.. |
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Jack Stoner
From:
Kansas City, MO
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Posted 19 Sep 2017 2:23 am
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| A steeler friend (an EE) and I upgraded the chips in two Nashville 400's. Mine had the original Peavey factory installed tone mod (that didn't change the op-amps) and his had the Lemay mod (that did change some of the op-amps). We put the new OPA op-amps in and in these two tone modded amps it made no hearable difference. |
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Jack Stanton
From:
Somewhere in the swamps of Jersey
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Posted 19 Sep 2017 5:05 am
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Jack,
Fair chance you may be absolutely correct, but for the price, I'll give it a go and report back. |
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Bob Metzger
From:
Waltham (Boston), MA, USA
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Posted 19 Sep 2017 9:47 am
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A little repetition of Steven Paris's post but with my reverb mod kit for the Peavey Nashville 400 amp I recommend using the Burr-Brown op amp:
IC5 is for the reverb drive and recovery and I recommend that you change it to the better performing Burr-Brown OPA 2134PA if you have an earlier model NV 400, prior to the incorporated preamp mod (the Peavey Tone Enhancement Mod). The ICs in this amp are socketed and the IC I recommend is exact pinout compatible; just remove the old one and drop in the upgrade IC, noting the correct orientation.
Bob M.
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Bob M. |
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