[WDC]

When building and mono block tube amplifier is there an advantage in using the point-to-point Teflon coated wire circuitry over a printed circuit boards. Do you lose quality of sound when using a printed circuit board over point-to-point wiring? I read a lot of discussion about Teflon coated wire and silver solder points and am curious as to why people choose this type of circuitry over the simplicity of circuit boards other than cost. Is there a sound quality issue here. In doing some research I see a lot of name brands amplifier manufactures use printed circuit boards such as Macintosh.

Attached is a photo of a Macintosh PCB

 

[JohnFerrier]

Therefore, air wiring creates smaller capacitance than PCBs (which have small interlayer capacitors with FR4 as a dielectric). I chose a JFET design that doesn't use a PCB. (Erno Borbely actually sells PCBs that otherwise fit an earlier design goal.) Instead my unit uses 0.035" sheet "O.F." copper for power/ground planes and the components are air wired using 17 AWG silver wire. The idea being to use as much copper and silver as possible and to use everything else as little as possible (even wire insulation--though I do use insulated power leads). Technically, there may be a small gain in signal to noise; realistically, it probably doesn't make an audible difference. But hehehe...maybe it does make a difference... Anyway, I thought if I was only going to build one amplifier, why not air wire it.

Below is an inside picture. At the edges, you may see the white electrical grade teflon seperating the power and ground copper plates. The plate copper was too difficult to solder so I used silver impregnated epoxy. Silver is a slightly better conductor of electricity and of heat (for heatsinking the JFETs to copper refrigerator tubing/6 AWG copper plugs). hehehe... this isn't called a Boutique Follower for no reason... the sound is ever so slightly juicy... hehehe...

http://www6.head-fi.org/forums/showthread.php?p=779010


JF

 

[Wodgy]

FYI, that's not actually a photo of a McIntosh PCB. That's a photo of one of the Chinese imitation PCBs that sell on eBay. Some of those are not bad, but the quality varies quite a bit. A lot of them aren't even efforts at cloning the original circuit. Tone controls for example are usually always missing, and some of the PCBs don't come with parts lists.

Most or all of the classic McIntosh amplifiers from the 50's and 60's were point-to-point wired. They did not use a PCB. Modern McIntosh amps do.

While purists sometimes claim that point-to-point amps sound better, I'm not sure there's any real difference in sound. A well laid out PCB is also generally going to be less noise prone than a messy point-to-point amp. The real reason most hobbyists use point-to-point wiring is because it's easier. Tube circuits, particularly single-ended ones, are simple and the parts are generally big and easy to manage. You can easily swap parts of different sizes in and out and correct mistakes. It's a lot harder to correct mistakes in a bad PCB layout after you've soldered everything down. Also, real PCB layout software costs money (even Eagle, since the freeware version doesn't support large enough boards for most tube circuits) and producing boards involves additional costs. By the time you've done the PCB layout and had it made, you pretty much could have point-to-point wired your amp.

 

[drewd]

I'm with Wodgy on this. For a one-off design, point to point may be more economical than a PCB, but at audio frequencies, the small capacitance introduced by a circuit board is virtually insignificant - as insignificant as the inductance that a wire introduces in a point to point layout.

A PCB offers the advantage of ease of construction and, more importantly, consistency of design and of electrical properties. A drawback is that once the design is etched, it's done. A point to point design is ripe for (relatively) easy modification.

I think that the bottom line is that the design and constuction quality far outweighs whether or not the amplifier is built on a PCB or air wired. And both methods can yield exceptionally good performing amplifiers.

-Drew

 

[JohnFerrier]

Quote:

Originally Posted by Wodgy A well laid out PCB is also generally going to be less noise prone than a messy point-to-point amp.

Well, I'd like to read the details of this...

Noise is mostly a function of resistance. Because of the cross-sectional area of wire is much larger, conductivity is larger (and the tiny bit of noise is lower). Further, contamination on the PCB or the PCB materials may possibly cause noise or degradation of sound. Compare this to air.

If you mean some kind of signal coupling, then again the proximity of PCB traces lends itself to higher coupling noise.

---

Quote:

Originally Posted by drewd ...as insignificant as the inductance that a wire introduces in a point to point layout. -Drew

To quibble, PCBs have the exact same inductance. Regardless, reactively, capacitance will be higher than the inductance. Also, the cross-sectional area of wire is going to be much higher than a PCB trace. Not to mention the higher cross-sectional area of silver in some wires...this point being the higher conductivity of wire over traces...

---

The beauty of air wiring is the use of three dimensions to route signals. One can use large diameter, high purity conductors and separate signals to minimize coupling and capacitance effects. Air is working as an excellent dielectric. (A PCB has three dimensions, too. It's just that one of the dimensions is very small.)


JF

 

[Wodgy]

Quote:

Originally Posted by JohnFerrier Quote: A well laid out PCB is also generally going to be less noise prone than a messy point-to-point amp. Well, I'd like to read the details of this...

In tube circuits, a messy point-to-point layout is prone to have signal wires running close to AC tube heaters, the chassis mains switch, or to unfiltered B+ lines, causing noise pickup. Carefully wired gear is fine, of course. PCB assembly tends to deliver consistent performance from unit to unit without having to worry where the wires are in 3-space, and the ability to enforce design rules in software (for trace separation) mitigates many worries to begin with.

Quote:

...the components are air wired using 17 AWG silver wire. The idea being to use as much copper and silver as possible and to use everything else as little as possible (even wire insulation--though I do use insulated power leads). ... Because of the cross-sectional area of wire is much larger, conductivity is larger ... Also, the cross-sectional area of wire is going to be much higher than a PCB trace. Not to mention the higher cross-sectional area of silver in some wires...this point being the higher conductivity of wire over traces... ... One can use large diameter, high purity conductors

I'm curious. You're one of the forum's most vocal cable disbelievers (I'm a disbeliever too, but not vocal about it). Do you think any of these things you're talking about really has any impact on sound at all? How is this line of argument consistent with your position on cables? Why did you go to the special expense of using 17 AWG silver wire when building your amp if wires don't make a difference? Wouldn't it have made more sense to put your money where your mouth is and just use regular 20-24 gauge copper hookup wire? This isn't meant to be combative; I'm just curious.

 

[drewd]

Quote:

Originally Posted by JohnFerrier Well, I'd like to read the details of this... Noise is mostly a function of resistance. Because of the cross-sectional area of wire is much larger, conductivity is larger (and the tiny bit of noise is lower). Further, contamination on the PCB or the PCB materials may possibly cause noise or degradation of sound. Compare this to air. If you mean some kind of signal coupling, then again the proximity of PCB traces lends itself to higher coupling noise.

Given the low currents that we're talking about here, the effect of the cross sectional area of the traces is negligible. The effects of contamination of the PCB or its materials is also quite small, given that a professionally produced PCB is manufactured to quite strict tolerances.

A well designed PCB does not lend itself to signal coupling. The effective placement of ground traces and planes, in fact, can virtually eliminate coupling, while the small surface area of the traces themselves dramatically reduce capacitance. Further, since coupling is a function of both trace geometry and signal edge rates, it becomes even easier to reduce or eliminate coupling because the edge rate of an audio signal is quite low.

Quote:

Originally Posted by JohnFerrier To quibble, PCBs have the exact same inductance. Regardless, reactively, capacitance will be higher than the inductance. Also, the cross-sectional area of wire is going to be much higher than a PCB trace. Not to mention the higher cross-sectional area of silver in some wires...this point being the higher conductivity of wire over traces...

But a well-designed PCB tends to have shorter traces than an air wired amplifier, so the effect of the inductance is less. If you consider the traces and wires as a distributed inductance, you'll find that the overall inductance of a PCB trace tends to be less because the trace is shorter. Nonetheless, as I pointed out, the effect of the inductance at audio frequencies is marginal at best.

Quote:

Originally Posted by JohnFerrier The beauty of air wiring is the use of three dimensions to route signals. One can use large diameter, high purity conductors and separate signals to minimize coupling and capacitance effects. Air is working as an excellent dielectric. (A PCB has three dimensions, too. It's just that one of the dimensions is very small.)

I don't dispute that point to point wiring is easier. I don't dispute that air is a fine dialectric. But, all things being equal, a well designed PCB can sound just as good as a well designed point to point wiring job. The issues that you've raised are measurable, in that we can measure the picofarads of capacitance, femtohenries of inductance and microohms of resistance differences between the two wiring techniques, but the sonic impact of such differences are inaudible - they lie below the inherent variation of the components in the amplifiers themselves!

-Drew

 

[JohnFerrier]

Quote:

Originally Posted by Wodgy I'm curious. You're one of the forum's most vocal cable disbelievers (I'm a disbeliever too, but not vocal about it). Do you think any of these things you're talking about really has any impact on sound at all? How is this line of argument consistent with your position on cables? Why did you go to the special expense of using 17 AWG silver wire when building your amp if wires don't make a difference? Wouldn't it have made more sense to put your money where your mouth is and just use regular 20-24 gauge copper hookup wire? This isn't meant to be combative; I'm just curious.

When I built my amplifier, I was less sure about the differences that wires make. Technically, such things make a tiny difference. However, as is well known, our ears work on a power log scale (and therefore have difficultly with small differences). Like everyone, I want to have the best system. Some things make much bigger differences than others (for technical reasons I put wire at one end of this spectrum). In the end, I think a person should do whatever makes a person a better listener. Through these audio chains (from recording to play back), our ears are presented with an enormous amount of complex signals. From an "audiophile" standpoint, I find it useful to be spending more time thinking about what is going on with the recording process--recording acoustics, equipment, etc.

The reason I've been vocal is to force out the most objective evidence that wires make an audible difference. Since I have a technical understanding of how this works, I've hoped to balance this with the rather vocal proponents of the audibility of cables. This is a public forum, we are in this together...

And regarding messy wiring, I didn't consider tube equipment (even though you did mention it in your previous post...).... You can see, I need to work on my reading/listening skills too...


JF

 

[erix]

My favorite reason:

Point-To-Point is WAY more fun to build.

ok,
erix

 

[JohnFerrier]

Quote:

Originally Posted by drewd ...differences between the two wiring techniques, but the sonic impact of such differences are inaudible - they lie below the inherent variation of the components in the amplifiers themselves! -Drew

Yep. It's just that I was less sure about the audibility of such things when I built it. Since I only wished to build one, I desired my best effort. This took six months, I didn't take the easier route.


JF