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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 12th November 2019, 10:30 PM   #30591
1audio is offline 1audio  United States
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by wayne View Post
Would that have been the LM12?
The LM12 was an 80 watt power amp. I used hundreds in subwoofers in the 1980s.
I think the hybrid opamp was the lh0032. I used those in an early Spectral power amp. Fantastic story in the early 1980s.
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Old 12th November 2019, 10:37 PM   #30592
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by Markw4 View Post
Bob,
You might think about some questions before starting:
What is the amp worth if you sell it now in working condition?
Are you willing to risk complete loss of the unit if things don't turn out well?
How much money are you willing to spend experimenting with it?
Mark. These amps are not that hard to fix, compared to something like a Crown
Ref 1A, they are fairly straight forward.

Having said that, we will assume Bob has at minimum a decent Cro to actually
see what it's doing and a basic level of electronics knowledge otherwise, leave
it alone.

Terry
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Old 12th November 2019, 10:43 PM   #30593
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by RNMarsh View Post
WRT lead free solders, has anyone had any experience with these high
reliability varieties (REL61 and REL22) ?

High Reliability Alloys | AIM Solder

TCD
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Old 12th November 2019, 11:27 PM   #30594
anatech is offline anatech  Canada
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John Curl's Blowtorch preamplifier part III
Hi Richard,
Excellent read! Thank you.

-Chris
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Old 13th November 2019, 12:11 AM   #30595
auplater is offline auplater  United States
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Default more stuff to fret over

all of the discussion re: different plating = different sound seems naive re: the literally hundreds of (usually) undocumented ways gold is applied electrolytically to electronic components. Kester has a brief article (more I'm sure) that hints at just a few of the problems soldering to various surfaces at various gold thicknesses, underplate, nickel, palladium, etc. etc.

https://www.kester.com/Portals/0/Doc...ver_Nickel.pdf

Seems that logically all of these undocumented variables should also have an effect on perceived sound quality, but noone seems to know or care about such things as grain size, deposit purity, surface morphology, the list goes on.

Yes, a few occasional references to grain oriented cables and such, but let's be serious and think for a moment. I made hundreds (if not thousands) of parts from all sorts of base metals for radio astronomy and DOD contracts, almost all of which required precision mil-spec gold plating, with various property modifications as functionally required (and verifiable thru testing). we rarely had problems with interface distortion, micro-diodes, etc. (and working in the THz range in some cases). Hard to believe there are issues at audio frequencies.
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Old 13th November 2019, 12:40 AM   #30596
Max Headroom is offline Max Headroom  Australia
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Quote:
Originally Posted by Terry Demol View Post
Mark. These amps are not that hard to fix, compared to something like a Crown
Ref 1A, they are fairly straight forward.
hint6_black_inside 02.jpg
I say this excellent design, especially that it has two identical (none of that mirrored layout rubbish) amp modules completely on connectors that easily drop out and can be operated out of the chassis position.
All other boards will also remove pretty easily....like I said it's good Taiwan design, easy for production and easy for servicing.

Quote:
Having said that, we will assume Bob has at minimum a decent Cro to actually see what it's doing and a basic level of electronics knowledge otherwise, leave it alone.
Mark, you are making serious implications that Bob is some kind of moron if he cannot cut and solder four wires successfully on rear panel connectors, nothing to do with active pcb's, and btw he has successfully rewired his loudspeaker crossovers.
And yes of course he has already considered the outcomes you describe, otherwise he would not be asking for advice so solve a problem that bugs him, ie he bought an amp that is not performing to his expectations.
I am encouraging Bob in several no risk /low risk steps to correct/improve a few elementary aspects of the design which will improve the coherency of the sound and should get the sound closer to what wants....and maybe some tips for the factory too.

Dan.
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Old 13th November 2019, 01:17 AM   #30597
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by Max Headroom View Post
Mark, you are making serious implications that Bob is some kind of moron if he cannot cut and solder four wires successfully on[I] rear panel connectors
No chance you are jumping to conclusions?
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Old 13th November 2019, 05:32 AM   #30598
RNMarsh is offline RNMarsh  United States
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I spec'ed gold thickness for Monster connections/plugs/recept etc to be 60 u inch thickness to prevent corrosion of base metal. Those connectors were made to fit with a typical thin layer. Added gold made them a very tight fit.

High Thickness Gold Plated Connectors or Contacts (Greater than 50uin or 1.25um):
For applications where the highest corrosion protection and wear resistance are required, heavier gold deposits of 50uin (1.25um) or more are typically required. Depending on base material and surface finish of the connector, 100uin (2.5um) or more of gold plating is required to develop a fully pore-free layer that will provide the best barrier protection against corrosion of the base material. Gold plating of contacts or connectors greater that 50uin is common of mil-spec and Oil & Gas interconnect applications that are exposed to more aggressive environments as well as thermal and switching cycles. Heavier gold deposits in this range provide sufficient material to allow for very high cycle applications of 10,000 cycles or more when properly engineered with the proper underplate.

Gold Plating Thickness of Connectors - Advanced Plating Tech Blog


Porosity: Real World Concerns Part 2 | ConnectorSupplier.com


RJ45 Gold Plating Issues Causing Corrosion and Signal Loss



THx-RNMarsh

Last edited by RNMarsh; 13th November 2019 at 05:41 AM.
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Old 13th November 2019, 07:07 AM   #30599
Max Headroom is offline Max Headroom  Australia
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Quote:
Originally Posted by RNMarsh View Post
I spec'ed gold thickness for Monster connections/plugs/recept etc to be 60 u inch thickness to prevent corrosion of base metal. Those connectors were made to fit with a typical thin layer. Added gold made them a very tight fit.
Good heads up, thanks.
Quote:
High Thickness Gold Plated Connectors or Contacts (Greater than 50uin or 1.25um):For applications where the highest corrosion protection and wear resistance are required, heavier gold deposits of 50uin (1.25um) or more are typically required. Depending on base material and surface finish of the connector, 100uin (2.5um) or more of gold plating is required to develop a fully pore-free layer that will provide the best barrier protection against corrosion of the base material. Gold plating of contacts or connectors greater that 50uin is common of mil-spec and Oil & Gas interconnect applications that are exposed to more aggressive environments as well as thermal and switching cycles. Heavier gold deposits in this range provide sufficient material to allow for very high cycle applications of 10,000 cycles or more when properly engineered with the proper underplate.
Good info, thanks.

The Silver Plating Services page is interesting too.
Scroll to bottom of page for Silver Plating Services AMS 2412 Plating, Silver Copper Strike, Low Bake, looks interesting, no nickel undercoat.

Dan.






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Old 13th November 2019, 07:44 AM   #30600
Max Headroom is offline Max Headroom  Australia
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Hey, give Bob cred and encouragement I say, he is aware enough to do it right, he is just asking some questions along the way. .
Bob has good ears, he will soon tell us of sonic changes, this is a good little project, maybe Bob can find the sound he likes. .
And at least Bob is about to do actual experimenting, I haven't quite started the power isolator/conditioner box I have spoken about.

Dan.
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