Melcor Deconstructed
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CJ
Well-known member
FYI, I think this is the stuff that Pmroz was talkin bout at the bottom of the previous page of posts.
"This is for Brad, I'll title it "MY COLORFUL RESPONSE"
A few people left Melcor and started API with some others. The original
2520 was "stolen" from Melcor, but the guy who designed it was one of
the ones who left. Many early API and Melcor op-amps have an RCA
sticker on them, as that is what they were. Melcor never went anywhere
after that, but the basic theory behind the amps and eqs were very
similar early on. Many people get Melcor and MAP (Modular Audio
Products) mixed up. MAP had a clone 550 and other stuff with an
IC/trans op-amp that was marginal at best.
API made as many as 20 changes over the years to the 2520, most of them
during the original 60-70's era. The changes were made because of
stability, heat, current, discontinued parts (TIS Transistors), Quieter
input devices and technical masturbation. Most of the changes made it
sound different. Datatronix made the same ones as API did,
After I purchased API, we built 2500 original 2520's and then were
forced to go to surface mount as they could not be built for less than
$200.00 each by hand. We preserved as many of the parts as possible.
As time and surface mount devices got better, so did the 2520. Just
before I sold API to ATI, Jeff and I found a matched input pair that is
almost identical to the original input pair that API settled on in the
70's. It is about the size of a crab (for those who got some on the
road and for those who didn't, it is very small) and has placed the 2520
back where it was. We did this about 2 years ago. I won't tell you
what the part is 'cause I'm a dick, and it is NOT a LM391. We started
placing the black foil labels back on them so everyone would feel fuzzy,
just like they did when we put the blue knobs back on the 550's.
Nothing will ever sound the way it used to, but we have done better than
anyone else has, so shut up. There is no product out there that
compares.
The Lord Paul"
cj
"This is for Brad, I'll title it "MY COLORFUL RESPONSE"
A few people left Melcor and started API with some others. The original
2520 was "stolen" from Melcor, but the guy who designed it was one of
the ones who left. Many early API and Melcor op-amps have an RCA
sticker on them, as that is what they were. Melcor never went anywhere
after that, but the basic theory behind the amps and eqs were very
similar early on. Many people get Melcor and MAP (Modular Audio
Products) mixed up. MAP had a clone 550 and other stuff with an
IC/trans op-amp that was marginal at best.
API made as many as 20 changes over the years to the 2520, most of them
during the original 60-70's era. The changes were made because of
stability, heat, current, discontinued parts (TIS Transistors), Quieter
input devices and technical masturbation. Most of the changes made it
sound different. Datatronix made the same ones as API did,
After I purchased API, we built 2500 original 2520's and then were
forced to go to surface mount as they could not be built for less than
$200.00 each by hand. We preserved as many of the parts as possible.
As time and surface mount devices got better, so did the 2520. Just
before I sold API to ATI, Jeff and I found a matched input pair that is
almost identical to the original input pair that API settled on in the
70's. It is about the size of a crab (for those who got some on the
road and for those who didn't, it is very small) and has placed the 2520
back where it was. We did this about 2 years ago. I won't tell you
what the part is 'cause I'm a dick, and it is NOT a LM391. We started
placing the black foil labels back on them so everyone would feel fuzzy,
just like they did when we put the blue knobs back on the 550's.
Nothing will ever sound the way it used to, but we have done better than
anyone else has, so shut up. There is no product out there that
compares.
The Lord Paul"
cj
bcarso
Well-known member
ROFLMAO!!!
At least you can't get crabs from technical masturbation!
:razz:
At least you can't get crabs from technical masturbation!
:razz:
bcarso
Well-known member
"Jeff and I found a matched input pair that is
almost identical to the original input pair that API settled on in the
70's."
I'll bet it's an SMD biploar dual from Japan, probably Toshiba. BTW those are the only packages Toshiba is making dual FETs in now---and to make matters worse the sources are tied together internally =(
Fools...
almost identical to the original input pair that API settled on in the
70's."
I'll bet it's an SMD biploar dual from Japan, probably Toshiba. BTW those are the only packages Toshiba is making dual FETs in now---and to make matters worse the sources are tied together internally =(
Fools...
CJ
Well-known member
You think that's bad, TI just went lead free on all their products. At least, that's what I heard at work today, someone might want to verify that. I hate cooperate web sites.
Flatpicker
Well-known member
[quote author="pmroz"]...also Paul Wolff, formerly of API, posted a quick history at PSW, but 20 search minutes later i can't find it...[/quote]I think he posted that at RAP, not PSW. Anyway, somewhere on a forum (don't remember which one :sad
someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use. However, if it's the same version as the '99 stock 2520 used in Session 2 of The Listening Sessions, http://www.thelisteningsessions.com/session2.htm it sounds pretty darned good! I like it much more than the "vintage" 2520 there, at least on that guy's voice.
someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use. However, if it's the same version as the '99 stock 2520 used in Session 2 of The Listening Sessions, http://www.thelisteningsessions.com/session2.htm it sounds pretty darned good! I like it much more than the "vintage" 2520 there, at least on that guy's voice.
[quote author="Flatpicker"] Anyway, somewhere on a forum (don't remember which one :sad someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use.[/quote]
Most likely the CMKT5088 and CMKT5087 made by Central Semiconductor.
These are dual versions of the good old 2N5088 and 2N5087.
someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use.[/quote]Most likely the CMKT5088 and CMKT5087 made by Central Semiconductor.
These are dual versions of the good old 2N5088 and 2N5087.
CJ
Well-known member
Holy Cow TK, bionic memory.
How's the weather up there?
Is the Columbia stil runnin?
Is tha AAA park still downtown with the Jantzen sweatere lady in the outfield?
Willy Horton hit her in the **** once. :razz:
Those Beavers are on a roll. No wait, that would make them butter. Ever had a buttery beaver? :grin:
How's the weather up there?
Is the Columbia stil runnin?
Is tha AAA park still downtown with the Jantzen sweatere lady in the outfield?
Willy Horton hit her in the **** once. :razz:
Those Beavers are on a roll. No wait, that would make them butter. Ever had a buttery beaver? :grin:
Hey,
I've got some melcors to stuff but have a cpl q's after all the action in this thread...(goin on the schemo posted in 1st post):
1. C1 - anything from 680pF to 1000pF it seems will do ye?
2. C2 - stays at 10pF (or change to 22pF?) but left leg (currently goin to Q6 base) instead goes to base of Q2?
3. C3 - stays at 10pF?
Thats it!
Cheers :thumb:
I've got some melcors to stuff but have a cpl q's after all the action in this thread...(goin on the schemo posted in 1st post):
1. C1 - anything from 680pF to 1000pF it seems will do ye?
2. C2 - stays at 10pF (or change to 22pF?) but left leg (currently goin to Q6 base) instead goes to base of Q2?
3. C3 - stays at 10pF?
Thats it!
Cheers :thumb:
bcarso
Well-known member
[quote author="tk@halmi"][quote author="Flatpicker"] Anyway, somewhere on a forum (don't remember which one :sad someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use.[/quote]
Most likely the CMKT5088 and CMKT5087 made by Central Semiconductor.
These are dual versions of the good old 2N5088 and 2N5087.[/quote]
Thanks Tamas. That's plausible. More and more manufacturers are doing two-chip duals with parts picked off of adjacent wafer locations---Philips and Diodes Inc. are two such. Damn near as good as monolithic duals and I like the isolation---much more versatile and lower coupling C.
someone posted what the "crab" size part most likely was, but I forgot it's mfg and #. I do remember that the part was so tiny, I more or less wrote it off as a real pain to use.[/quote]Most likely the CMKT5088 and CMKT5087 made by Central Semiconductor.
These are dual versions of the good old 2N5088 and 2N5087.[/quote]
Thanks Tamas. That's plausible. More and more manufacturers are doing two-chip duals with parts picked off of adjacent wafer locations---Philips and Diodes Inc. are two such. Damn near as good as monolithic duals and I like the isolation---much more versatile and lower coupling C.
Hey Fabio!
Thanks. Okay, 2 q's on C2/C3 still remain tho... I've read bcarso saying 22pF for C3 (confirmed?) and also Raf saying that C2 absolutely goes (left leg in schem on 1st post) to the base of Q2...not Q3 - is this confirmed by anyone who's rewired it so?
Best,
Thanks. Okay, 2 q's on C2/C3 still remain tho... I've read bcarso saying 22pF for C3 (confirmed?) and also Raf saying that C2 absolutely goes (left leg in schem on 1st post) to the base of Q2...not Q3 - is this confirmed by anyone who's rewired it so?
Best,
Flatpicker
Well-known member
I recall Peter C. on the other thread saying he had to use 1000pF at C1 before it would stop oscillating. I'm going to try and get one (Peter's layout) built tonight and start testing.
Flatpicker
Well-known member
[quote author="daArry"]...and also Raf saying that C2 absolutely goes (left leg in schem on 1st post) to the base of Q2...not Q3...[/quote]Not doubting Raf, but if so, there are lots of pcbs laid out wrong.
Im using 680pf for c1 right now as suggested earlier in this thread.
Are you saying that this suggestion is wrong, and c1 should be 1000pf?
And what about c2? Im using 10pf right now as in the schematic, (not sure where it goes though right now)
everything seems to be working just fine (sounds fine anyway) the way it is btw.
/Jonas
Are you saying that this suggestion is wrong, and c1 should be 1000pf?
And what about c2? Im using 10pf right now as in the schematic, (not sure where it goes though right now)
everything seems to be working just fine (sounds fine anyway) the way it is btw.
/Jonas
clintrubber
Well-known member
While I haven't fired up the corrected opamp to confirm, I thought the history of the tracing was reconstructed fairly complete a month or two ago - earlier up this thread.
See for instance the corrected schematic on the first page.
But there was an additional 'correction', which was as suggested (by PRR ?) perhaps only layout-related so not always relevant.
It's not in that drawing, but was like this:
left side of C2 goes to the base of Q2 (pin '-IN') i.s.o. base of Q3.
Note there are a bit different ideas around here about certain values & connections, so I'd first trust the guys like Fabio etc who have this circuit up & running.
See for instance the corrected schematic on the first page.
But there was an additional 'correction', which was as suggested (by PRR ?) perhaps only layout-related so not always relevant.
It's not in that drawing, but was like this:
left side of C2 goes to the base of Q2 (pin '-IN') i.s.o. base of Q3.
Note there are a bit different ideas around here about certain values & connections, so I'd first trust the guys like Fabio etc who have this circuit up & running.
Flatpicker
Well-known member
[quote author="clintrubber"]...left side of C2 goes to the base of Q2 (pin '-IN') i.s.o. base of Q3...[/quote]Fabio's schematic (see link on page 1) is the same as mine regarding C2 and Q3, so one might assume he laid his boards out this way as well, but only Fabio knows. :wink:
Also C1's value seems to still be up in the air. Even though the original used a 680pF, the 1000pF might possibly work better in our modern version. Peter seemed to think so when he built it.
Hopefully this will clear things up once and for all:
If you have the Peter C. layout board that Fallout was selling a year ago, use my schemo and layout on page one of this thread: http://www.groupdiy.com/index.php?topic=840#840 or Peter?s layout on his website if you want to go by values instead of reference numbers.
If you have Fabio's board, use Fabio's schemo on the first page of this thread.
Also C1's value seems to still be up in the air. Even though the original used a 680pF, the 1000pF might possibly work better in our modern version. Peter seemed to think so when he built it.
Hopefully this will clear things up once and for all:
If you have the Peter C. layout board that Fallout was selling a year ago, use my schemo and layout on page one of this thread: http://www.groupdiy.com/index.php?topic=840#840 or Peter?s layout on his website if you want to go by values instead of reference numbers.
If you have Fabio's board, use Fabio's schemo on the first page of this thread.
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