So what is the Rigtalk view of PCB vs PTP

[novosibir]

thanks for the insight novosibir

Anytime

Larry

 

[loudgtr]

thanks for the insight novosibir

Anytime

Larry

Yes; that was a very cool read: all of your insights and elaborations.

Maybe one of these days I'll get into some electronics. Maybe even get into sah5150's (Steve) amp kit once it gets going. I'm whatching his "amp building chronicles"thread with great interest.

Good time to be a guitar player

 

[jasonP]

Larry really cool stuff. Thank you for taking the time to write this.

 

[degenaro]

http://www.mesaboogie.com/US/Smith/point-to-point.html

I just read it once again and had to laugh so loud, that my wife woke up and asked, what's so funny on my computer
Yep - it's already 4:00 am here in good old Germany

But let's dig a bit into his writing, just picking out a few examples:

It is easy to demonstrate how moving some parts or lead wires as little as 1/4" can make a huge difference in the top end "transparency" of the sound--exactly where a lot of the magic lives--or dies.

Here he's absolutely right and obviously knows, about what he's speaking! But I want to supplement, that sometimes more than one inch left or right doesn't matter, but sometimes just 1/16 inch difference can affect the tone, the response and the dynamics of the amp a lot.

For example, the great top end of the Dual Rectifier has an aggressive bite but avoids the harshness by the way two very important traces are laid out on the board. One trace is on the top and the other runs right beneath it on the bottom side of the board. Thus the very small--but significant-amount of capacitance coupling these two together through the board performs a subtle filtering kind of negative feedback in a critical region where the harmonics can be made to line up just right.

1-st: I've never heard and couldn't hear myself yet, that a Dual Rectifier does have a great top end. The only what I could hear out of Rectifiers is a huge amount of background noise floor. So much, that the first time I've tried one myself I thought, that this amp is defective.

2-nd: It's nearly unbelievable, how he was able, to turn one of the most remarkable downsides of a PCB into a benefit! Really - IMO a good preacher got lost on him! I for myself like it better, to go the controllable way, if there's anywhere a capacitance required - then I simply solder in a cap and even can choose the cap's type after my liking. But what is, if it turns out after a while at M/B, that the cap better should have been a step bigger or smaller in value as thought at the beginning? Does he make then completely new PCB's?

Now go one step further and imagine trying to line up the letters on both the top and bottom sides of a sheet of paper--this time by writing longhand.

If he really feels himself in the situation, to must grasp to those poor and unsuitable comparasions, then anyway any objectivity already is gone.

... but we individually mount and point-to-point wire all jacks, switches, transformers and 8-pin power tubes. The reasons are increased reliability and...

But the preamp tube sockets are sitting on the PCB's - and are leading their heat into the PCB, especially when the tubes are hanging upside down! The PCB becomes warm, then hot, heating up the components -> then the component's values are drifting -> and after an hour or two the amp is sounding different to what it was sounding at the beginning, still cold. But who cares? Your ears anyway are hearing different after 2 hours rehearsing or gig

Another aspect of the heated up PCB is, that the copper traces do have another coefficient of thermal expansion than the PCB's material
The traces try to expand on the board, and shrink again after the PCB is cooled down - and again, and again... The moleculare structure of the copper is changing over time, it starts to crystalize - and anywhen (maybe during the nicest solo on stage) a trace is breaking

I must have repaired thousands of old Fenders (...) I finally found out why some of these noisy amps seemed incurable. The noise was originating in the point-to-point tag board itself! The board material can absorb moisture and become slightly conductive.

Is this his understanding for "freedom of press" or just a huge lack in fairness and objectivity?

He specifically choose the way worst example of a PTP eyelet board, to compare it to PCB - the Fender 'cardboard'! Ouch!
But I've never seen yet a PTP wired boutique amp with this paperboard inside - they've all used fiber boards, which doesn't absorb moisture.

Here's another: Tag boards warp, and the warpage increases the space between eyelets. (...) No sweat. I must have fixed a hundred black face Fenders where point-to-point board warpage had caused this problem.

Same comment as just beyond! Fiber boards don't warp!

Is a round copper wire better than a flat copper trace on a circuit board? Not according to Randall Research (no relation to me!) who has studied audio conductors under all conditions, including at the molecular level under an electron microscope. His opinion is that if there is any advantage either way, it would be with the circuit board trace whose profile offers far greater surface area. It is well established that audio signals (especially the higher frequencies) tend to flow on the surface of the conductor, not through its core.

Yes, a PCB trace offers a greater surface than a comparable round wire, hence it's a better antenna for catching any noise fields, if the trace is one of the sensitive ones, like the traces to the preamp tube grids. Maybe the reason for the Rectifier's background noise?

And yes again, high frequencies tend to flow on the conductor's surface - but this effect first becomes apparent from a frequency of 20 MHz onwards and is very important only in the GHz area. But we're speaking about audio amplifiers, and not about radio or TV transmitters

Just my two ceramic caps to this writing.

Larry

kannst ma an bauen mit drei im weggla als vorstufen?
servus von an ex nermberger...

 

[thegame]

Larry, you are brutally honest. I love it

 

[vchizzle]

As long as its well built and sounds awesome, I don't much care. I've had both PCP and PTP amps that give me "the vibe". As long as it gets your rocks off is reliable, who cares. Most of my amps in the past 8 years have been PTP, but I've had/played some great PCP's as well.

 

[jmgman69]

 

[novosibir]

Larry, you are brutally honest. I love it

As well as my amps

Larry

EDIT: Oh, interesting! With this post my board status has changed from a Hack to an apprentice NOOB - this means party time

 

[glpg80]

Larry, you are brutally honest. I love it

As well as my amps

Larry

EDIT: Oh, interesting! With this post my board status has changed from a Hack to an apprentice NOOB - this means party time

so glad to have you here on the board - you definately know what you are doing and have insane attention to detail

 

[stratotone]

So to sum it up - it depends on the individual amp, since there are shitty and stellar versions of each out there, and to buy an amp just because it is PTP or PCB doesn't really mean anything - it's how well the amp is constructed, not the style?

Pete