GP Article: Point to Point Wiring

[revgsmall]

Just got my new copy of GP and read the "All About...Point-to-Point Wiring". Although it was written in diplomatic lingo, I'll bet some of the amp builders are not going to be too happy.

I own a Mesa Mark IIC+, (two) 1970's era Fender Pro Reverbs, and a Vox AC-15 CC. Amps with the various types of construction that they talked about in the article. So far, no breakdown issues with any of them as long as I have owned them. Sound wise, I just don't know if it makes a difference.

I just don't have an opinion either way at this point on what makes a better amp. Can anyone point out some things that GP may not have covered?

[Teahead]

I agree that I can hear no great difference when PTP and PCB amps of a similar pedigree are played side by side. I've been told the advantage lies in the ease of repair offered by PTP design, but not being a tech I couldn't really care less about that.

[teleamp]

Haven't read the article, but here's my .02.

For the most part, circuit design is the biggest factor on how good an amp sounds as long as it is built properly reguardless of construction type. IMHO, there is only a slight difference in sound between contruction types when the circuit is a very simple circuit with very few parts. PTP amps (I mean where there is a solid mechanical connection that has been soldered, not just lay a wire on or through an eyelet and then soldered) are easier to service by techs that have lots of experience with repairing those types of amps. As a hobbyist builder I prefer to build amps using terminal strip/ptp construction (like a Matchless), to me it is easier than loading a board then having to solder added wire leads.

The MAIN advantage of good PTP (not eyelet board) construction is ruggedness, but only as long as good mechanical connections were made before properly soldering them.

MikeY

[HeeHaw]

I don't know if point to point wiring is better, but I guarantee the assembly line at mesa or marshall doesn't measure accross every electrical component to see if it is within spec and performing properly. I am also willing to bet that many of the big manufacturers have their transformer sets made in china for $5 each and probably don't bother checking them for consistency. VHT is probably one of the only exceptions here.

[bosstone]

Originally Posted by HeeHaw

I don't know if point to point wiring is better, but I guarantee the assembly line at mesa or marshall doesn't measure accross every electrical component to see if it is within spec and performing properly. I am also willing to bet that many of the big manufacturers have their transformer sets made in china for $5 each and probably don't bother checking them for consistency. VHT is probably one of the only exceptions here.

I doubt that there are many point to point builders who measure every component either. In defense of Mesa, I recently bought a 34 year old MK IIC+ that was heavily used with a lot of cuts in the tolex and the inside of the amp was dirty from years of bar smoke etc. Tubes had been replaced and so was the speaker but other than that, after opening it up the amp appeared not to have ever been worked on. At Mesa I watched Mike Bendinelli work on it and other than cleaning up the interior the only thing he could find that looked wrong was a resistor that showed signs of being burnt. Mike replaced it and as a preventative measure suggested replacing 2 of the silver capacitors and one other resistor. The amp sounds great and is well worth the service charge and the retolex job I am about to give it. Then he put it on a scope and actually rapped sharply on the chassis with a small ball peen hammer to find any sighs of bad connections. Some are paying $3,500.00+ for tolex ones. Hard wood versions go for at least $500.00 more than that.

[SgtThump]

Originally Posted by HeeHaw

I don't know if point to point wiring is better, but I guarantee the assembly line at mesa or marshall doesn't measure accross every electrical component to see if it is within spec and performing properly. I am also willing to bet that many of the big manufacturers have their transformer sets made in china for $5 each and probably don't bother checking them for consistency. VHT is probably one of the only exceptions here.

Are there actually mass producing factories out there that measure/check every single item before they assemble it (for any product, not just guitar amps)? I honestly don't know, but I highly doubt it. Spot checking for QC is understandable, but I can't imagine a factory checking every item.

[reaiken]

Originally Posted by SgtThump

Are there actually mass producing factories out there that measure/check every single item before they assemble it (for any product, not just guitar amps)? I honestly don't know, but I highly doubt it. Spot checking for QC is understandable, but I can't imagine a factory checking every item.

I don't know about others in the guitar amp industry, but in the other electrical engineering worlds I live in on occasion, it is very common to do a full electrical test on the bare boards and occasionally a full "bed of nails" or "flying probe" test on all loaded components for large production runs - it is called ICT, for in-circuit testing, or ATE, for automatic test equipment. There are machines that can "learn" the board and test all connections to identify misloaded or out-of-spec components. The initial setup charge can be expensive, but if you amortize it over a large run of boards, it is actually rather cheap.

http://en.wikipedia.org/wiki/Bed_of_nails_tester

http://archive.evaluationengineering...es/0800low.htm


There is no doubt that you can get far better consistency with PCB than you can with PTP. The main advantage of PTP is ease of repair, unless it is true "bird's nest" PTP, which can sometimes be a bear to trace a circuit down and troubleshoot.

Randall Aiken

[usc96]

If they sound the same, I don't see the benefit in paying that much more. Hell, if your PCB version breaks, just buy another one. If would probably be cheaper to buy 2 PCB amps than to buy just one of the comparable PTP versions put out by some of the brand name companies.

[SgtThump]

Originally Posted by reaiken

I don't know about others in the guitar amp industry, but in the other electrical engineering worlds I live in on occasion, it is very common to do a full electrical test on the bare boards and occasionally a full "bed of nails" or "flying probe" test on all loaded components for large production runs - it is called ICT, for in-circuit testing, or ATE, for automatic test equipment. There are machines that can "learn" the board and test all connections to identify misloaded or out-of-spec components. The initial setup charge can be expensive, but if you amortize it over a large run of boards, it is actually rather cheap.

http://en.wikipedia.org/wiki/Bed_of_nails_tester

http://archive.evaluationengineering...es/0800low.htm


There is no doubt that you can get far better consistency with PCB than you can with PTP. The main advantage of PTP is ease of repair, unless it is true "bird's nest" PTP, which can sometimes be a bear to trace a circuit down and troubleshoot.

Randall Aiken

Oh, what do you know about building amps anyway!!!!!!

[reaiken]

Originally Posted by SgtThump

Oh, what do you know about building amps anyway!!!!!!

Not nearly enough, believe me!

RA

[2x6L6]

Isn't there a semantic issue here (haven't read the GP article, just speaking generally) - or perhaps a misunderstanding by many of us (possibly including me!)? In that an older Fender amp wired on an eyelet board is not PTP, but might be called "hand-wired," while "point-to-point" is that specific method of hand-wiring a circuit where components are for the most part soldered to each other, directly to tube sockets, etc. Frequently using small terminal strips as bridges between components. Typified perhaps (in the olden days) by this Supro Comet:




Or something even more serious like this Maggie 440, replete with reverb and vibrato:



Or am I all wet on this one - I'd be pleased to be corrected by someone as knowledgable as Mr. Aiken!

[reaiken]

You are correct. "True" PTP is an amp wired with the components suspended from the tube socket pins or sometimes terminal strips. Some people call tag boards or turret boards point-to-point, but they are really not, if you want to get technical about it. It is a semantics issue, as both styles are equally "repairable", but turret boards or tag boards are usually easier to troubleshoot and follow a layout/schematic.

I generally lump all styles of turret/tag/terminal strip amps into the "PTP" category, as opposed to PCB amps.

Randall Aiken

[voojo]

An interesting read, if you have some time:

http://www.londonpower.com/pcbinfo.htm

[SgtThump]

Originally Posted by reaiken

Not nearly enough, believe me!

RA

That's not what I hear... :AOK

[2x6L6]

Originally Posted by reaiken

You are correct. "True" PTP is an amp wired with the components suspended from the tube socket pins or sometimes terminal strips. Some people call tag boards or turret boards point-to-point, but they are really not, if you want to get technical about it. It is a semantics issue, as both styles are equally "repairable", but turret boards or tag boards are usually easier to troubleshoot and follow a layout/schematic.

I generally lump all styles of turret/tag/terminal strip amps into the "PTP" category, as opposed to PCB amps.

Randall Aiken

Good explanation - thanks. I must say, as a hobbyist (prolly true for pros also...???), I have learned a lot working on my little rat's nest PTPs but man, oh man they are migraine-makers compared to a nicely laid out tag or turret board.