PCB substrate question (Teflon Luxman & Accuphase oriented) - diyAudio
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Old 2nd July 2014, 03:40 PM   #1
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Default [SOLVED] PCB substrate question (Teflon Luxman & Accuphase oriented)

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See post #36 - PCB substrate question (Teflon Luxman & Accuphase oriented)

Hello fellow diyAudio members. This is my first post here.

My question is oriented around the pcb substrate Accuphase and Luxman is using. Both state on different places, that they use the PTFE type which is off-white type. I stumbled upon 3 articles about Luxman and I am a bit stuck in understanding everything involved, so maybe someone here can guide me.

Luxman

Click the image to open in full size. Click the image to open in full size.

Here is what the articles write:

"My favorite item in the overall design of the M800A is the use of specially fabricated, gently curved signal paths. All primary signals in the amplifier’s circuitries traverse on these specially printed routes with curved turns that resemble miniature race tracks. The PCB on which these beautiful signal paths are pressed is of specially prepared peel-coat type that is peeled off once the traces are printed. This PCB is then further coated with a 100µm-thick gold-plating to preserve the low-impedance and frequency response characteristics of the signal path against corrosion. (Note: “µm”, micrometer. 1,000 µm=1mm.)"

and

"Printed Circuit Boards normally have a green coat (dye) that can be printed upon, so the manufacturer knows where to place the copper traces and where to insert the resistors & capacitors. Luxman's designers don't like the sound of the green dye, in their extensive research they found that it smears the sound, so instead they print onto a plastic peel coat and remove it once the traces and mounting holes are in place. Then the copper traces are gold plated to reduce resistance across the circuit, as well as eliminate copper's corrosion over time.."

My two questions are as follow:

1. If I order a PTFE substrate PCB, will then get this off-white colour ? for it seams as there are types that have a brownish surface and I do not want that.

2. What is the purpose of the peel-coat. I am not talking about the photo etching resist and since Accuphase and Luxman is not using a solder mask after the gold plating. So I am kinda lost here. Any help ?

Last edited by Oneminde; 4th July 2014 at 07:32 PM. Reason: Solved
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Old 2nd July 2014, 03:59 PM   #2
marce is offline marce  United Kingdom
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They are sprouting a load of BS...
Go for FR4 standard PCB, 45 degree traces and use a solder resist (that is what the green stuff is) you will not notice or measure any difference in your signals.
The gold wont have any affect other than stopping tarnishing (not a problem anyway) and has a lower conductance than copper so will not reduce resistance.
Don't know what curved tracks are going to achieve maybe stops the electrons falling off at the corners....
Plenty of real information out there regarding PCBs, without resorting to esoteric audiophile nonsense.
Cant see the pictures by the way, a better link and one to the text would be nice....
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Old 2nd July 2014, 04:04 PM   #3
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I agree.

Last edited by Neutrality; 2nd July 2014 at 04:12 PM.
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Old 2nd July 2014, 04:15 PM   #4
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Quote:
Originally Posted by marce View Post
They are sprouting a load of BS...
Go for FR4 standard PCB, 45 degree traces and use a solder resist (that is what the green stuff is) you will not notice or measure any difference in your signals.
The gold wont have any affect other than stopping tarnishing (not a problem anyway) and has a lower conductance than copper so will not reduce resistance.
Don't know what curved tracks are going to achieve maybe stops the electrons falling off at the corners....
Plenty of real information out there regarding PCBs, without resorting to esoteric audiophile nonsense.
Cant see the pictures by the way, a better link and one to the text would be nice....
Here are the two articles.

1. On a Higher Note :: M-900u
2. A Luxman heritage illustration and a review of the $16,000 M-800A 80th Anniversary stereo power amplifier Review - Equipment Reviews - Dagogo

There are two reason why. The look of off-white PCB - should be PTFE according to my knowledge. And gold plated, and I will not need a solder mask.

I am thankful for the reply, but it did not really answer my question on Teflon or the purpose for the peel-coat, so still equally lost.

I get that there exist audiopholery and while some of that makes sense, not everything does, so I ask and I try to learn. What is obvious for someone skilled in the art of electronics may not be as obvious for someone ells, and there is the matter of taste and what looks good etc.
There are people that are happy with the project existing inside a shoebox, I am not that person.
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Old 2nd July 2014, 04:29 PM   #5
SY is offline SY  United States
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If your esthetic sense demands a white circuit board, I would bet that this is available with materials other than PTFE. Besides needless expense for audio applications, PTFE boards have markedly poorer mechanical properties and can be quite unreliable compared with more conventional epoxy resins.
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Old 2nd July 2014, 04:42 PM   #6
DF96 is offline DF96  England
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High-end audio uses high-mobility electrons which travel faster than the ordinary electrons used by lesser equipment. This means that they need a larger bend radius; otherwise they tend to accumulate at the corners of the PCB traces and create smearing of the stereo image. This problem can to some extent be reduced by ensuring that the tracks for the two stereo channels are identical - a technique used for years in high-speed digital circuits but only recently applied to audio.

These techniques (along with gold-plating) produce beautiful circuits and, as everyone knows, beautiful circuits create a beautiful music experience. In order to get the best advantage from this it is of course important that your audio sources and ancillary equipment are of the highest calibre.
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Old 2nd July 2014, 04:46 PM   #7
kevinkr is offline kevinkr  United States
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Teflon pc boards are more flexible than FR4 which means some care in handling is required. It has a lower and more stable dielectric constant which is relevant for microwave applications, but is otherwise probably more trouble than it is worth. Leakage is lower which is relevant in some very high precision analog measurement hardware. (semiconductor ATE and similar)

Again the lack of sharp angles is a technique useful in microwave and high voltage circuitry.

None of this hurts, but whether or not it is of any particular benefit is another question.

Speculating, but I assume the peel coat protects the board from damage during shipping and assembly. Possibly it could also be used during drill, and replaced subsequently. Presumably during assembly it performs the same function as the solder mask.
What are you building that requires this level of care?
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Old 2nd July 2014, 05:01 PM   #8
marce is offline marce  United Kingdom
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Plenty of esoteric materials here:
Advanced Circuit Materials - Rogers Corp

How often are they used in real life, very rarely and only on the very top 5% of designs...
Cant answer the Luxman quotes further because they are meaningless and this:
Quote:
Printed Circuit Boards normally have a green coat (dye) that can be printed upon, so the manufacturer knows where to place the copper traces and where to insert the resistors & capacitors. Luxman's designers don't like the sound of the green dye, in their extensive research they found that it smears the sound, so instead they print onto a plastic peel coat and remove it once the traces and mounting holes are in place. Then the copper traces are gold plated to reduce resistance across the circuit, as well as eliminate copper's corrosion over time..
is written by someone who has no idea about PCBs.
Interestingly I was discussing sharp corners the other day at work (90 degree bends don't even give a really sharp corner, 45s are not sharp at all)as they have no real affect on digital up to 2GHz....

As to FR4 there are many types the generic name covers a whole host of temperature ranges and weave patterns, from basic cheep stuff to more exotic FR4 for very high speed designs etc.
The only time I don't use solder mask on boards is when they are for the European space agency or similar, in space they don't like solder mask.....
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Old 2nd July 2014, 05:21 PM   #9
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Quote:
Originally Posted by kevinkr View Post
Teflon pc boards are more flexible than FR4 which means some care in handling is required. It has a lower and more stable dielectric constant which is relevant for microwave applications, but is otherwise probably more trouble than it is worth. Leakage is lower which is relevant in some very high precision analog measurement hardware. (semiconductor ATE and similar)

Again the lack of sharp angles is a technique useful in microwave and high voltage circuitry.

None of this hurts, but whether or not it is of any particular benefit is another question.

Speculating, but I assume the peel coat protects the board from damage during shipping and assembly. Possibly it could also be used during drill, and replaced subsequently. Presumably during assembly it performs the same function as the solder mask.
What are you building that requires this level of care?
To everyone, thank you for the reply's.

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@ kevinkr

Your explanation for the peel coat makes sense since that is what I consider it to be used for as well, protection during storage and transport. I guess that is important for equipment that cost several thousands of $. Not that the value is connected to parts cost, something which buggers me quite allot.

Highly rated audiophile equipment is over rated in terms of value and quite often the price level is just stupid. Lets take an example. There exist a vinyl record player that use the same type of electro motor that can be found on the Mars Rover. This vinyl record player costs $125 000,- and that is just plain stupid. Then we have the low end, low cost components and electronics that barely do what they are suppose to do with bad to generic sound. Some people will be okay with that and do not really have any requirements besides the speakers should make noise. I exist in-between these two levels. I want high grade equipments, but I do not want to pay a small fortune - if that makes sense as I am sure it does for many diy people, why ells put in time and money it is required to produce equipment. Sure, for the fun of it works, but that can hardly be the only reason.

I am planing several parts in a Music & Home Cinema solution and I am inspired by Tidal Audio, B&W, Morten Design, Accuphase, Luxman, Marantz and some of these use among other Duelund Coherent Audio, Accuton and so forth. But the cost of equipment from these producers - using Accuton, Duelund, Nichicon cap's etc is just a big no. However, develop and construct my own line of pre-amps, power amps, speakers is something I can manage. So I want quality, high grade and God damned it, good looking stuff, on a budget.

Hope that answer the question ?
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Old 2nd July 2014, 05:39 PM   #10
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Quote:
Originally Posted by marce View Post
Plenty of esoteric materials here:
Advanced Circuit Materials - Rogers Corp

How often are they used in real life, very rarely and only on the very top 5% of designs...
Cant answer the Luxman quotes further because they are meaningless and this:

is written by someone who has no idea about PCBs.
Interestingly I was discussing sharp corners the other day at work (90 degree bends don't even give a really sharp corner, 45s are not sharp at all)as they have no real affect on digital up to 2GHz....

As to FR4 there are many types the generic name covers a whole host of temperature ranges and weave patterns, from basic cheep stuff to more exotic FR4 for very high speed designs etc.
The only time I don't use solder mask on boards is when they are for the European space agency or similar, in space they don't like solder mask.....
The reduction of resistance is BC, that is a fixed material value, the gold prevents Cu oxidation and that bears merit and the only thing of interest besides that it looks nice - I am a sucker for design and how things look yes, but that does not mean I am stupid.

Now see, the part about different grades of FR4 is important and since you know what you are talking about. What type / grade should I focus on if I want the same look as the Luxman PCB ?. I guess epoxy fibreglass FR4 is fine if the substrate is white - maybe a pure design / look aspect if the substrate does very little in terms of colouring the function.

In regards to sharp and non sharp corners, 45-degree is the standard besides if there is no room to do that. Many use 90-degree and that works fine as well, but soft corners are more gentle on the signal. Its not like I think that a 90-degree corner will throw electrons out from the path
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