Ptp Vs. Pcb

Discussion in 'Amps and Cabs' started by Kborg, Oct 5, 2005.

  1. Kborg

    Kborg Silver Supporting Member

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    I hope this isn't like discussing politics or religion but after seeing the direction a post took on a Guytron, and comments in regards to it using printed circuit boards in its construction, it made me curious.

    There are obviously a group of people that believe Point to Point is superior to Printed Circuit board construction.

    There is also a group that I am assuming, by the fact that they use PCB construction instead of PTP, feel that PCB is the better way to go. I'm not talking about the mass production, price point type stuff, only high end.

    I am not trying to speak for anyone, I just want to hear opinions and learn something.

    From my point of view, obtaining the tone I want and reliability are the main concerns. PTP vs PCB doesn't matter.

    What do you think and why?
     
  2. electronpirate

    electronpirate Member

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    My opinion is that PTP is easier to WORK on. PCB is easier to manufacture. Sonically, I still believe that there is NO difference for the most part.

    PCB allows amp makers to design an amp that is very consistent across production. That means they all will sound the same (obviously this can be good or bad.)
    PTP allows easier maint and understanding of the 'guts'. Also makes it easier to mod.

    Like everything, do you need to know that an amp is PTP for you to decide whether it sounds good or not? I've heard and owned many crappily built amps that sounded GREAT, and PTP's that sounded like the south end of northbound <insert mammal>.

    Ears, not construction is the judge.
     
  3. Mayflower

    Mayflower Supporting Member

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    Oh Boy.... here we go!
    PCB; Tone wise, some are great, others can be duds. Same as a PTP amp.
    PTP wired amps are generally easier to service and are more $$$.
    (this is the nutshwell version IMO)> Make your own decisions based upon personal tone taste and finances!
    Good luck!
     
  4. VaughnC

    VaughnC Supporting Member

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    A "properly designed" PCB amp can be as reliable and will be tonally more consistent than PTP. The key words though are: "properly designed"....which is where it gets very subjective. I know printed circuit boards themselves have improved greatly over the years but, in a gigging scenario, PCB mounted tubes, pots, and jacks still make me nervous.
     
  5. Kborg

    Kborg Silver Supporting Member

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    Hi VaughnC,

    I just checked out your TS9 mods and it looks like you've really done some extensive mods to the TS9. I bet they sound great in front of your Komet. I've not heard one of those yet but I always hear good things about them.
     
  6. VaughnC

    VaughnC Supporting Member

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    Yup, I always liked the basic sound of a Tube Screamer/Strat combination so I started tinkering with a TS9 reissue in attempt to try and get a bit more versatility & tone out of it....which eventually led to an OD pedal of my own design. And, being that a Komet 60 sounded best to me for my sound, I sort of tuned my TS9 mods and my homebrew OD pedal to that amp. Not everyone's cup of tone but it works for me ;) .

    If you ever get the opportunity though you'll have to try out a Komet 60. To my ear, it has that 3rd dimension that many other amps lack.
     
  7. StompBoxBlues

    StompBoxBlues Member

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    I don't have direct evidence but...I do know electronics (at a ASEE level) and have recently been reading a little more about this and there is good evidence that there IS a difference...

    PCB have one inherent problem. The traces are all runing on the same plane. This is not a huge problem, but it is a problem because this means there is capacitance between traces.

    If you have a capacitance meter, or can measure it on a DMM, try it out (this is an idea from a book I recently was reading) with just two pieces of wire. Lay them side by side, fairly close together...parallel and at the same level (on a tabletop).

    Measure the capacitance. Now put them at right angles, bend them, make them like they are in point to point....not parallel and perfectly even...the capacitance will be significantly less.

    Capacitance will bleed off the highs...

    There are folks that claim this is why reissue of amps that were PtP but the reissue is PCB never sound the same.

    Maybe they can minimize the effect with clever routing, but I am pretty sure they aren't thinking about that. Also that the wires are on the same plane...

    Another couple of things...I think PCB are more susceptible to warping, more easily damaged (by heat)...I don't think they are "hard" to work on particularly, but it is a pain when a solder job loosens a trace.. etc.

    Another thing about PCB, especially SOME manufacturers, they have plugs and ribbon cables, which means again capacitance, but also more chances for loose connections (all amps have some spades/plugs but I think they are minimized, on PCB's they run them between PCB's to link them, to make it all modular) and
    both capacitance and resistance.

    Sockets on PCB, I hate. Another thing, they sometimes mount resistors/diodes/etc..that get really hot, with the component touching the PCB. This is bad, it prevents the component from dissipating the heat (just a little gap all around can do immense improvements on heat dissipation) which means after running a while it might sound a little different. PtP I think the components generally have air on all sides.

    All this said...I don't own currently a point to point amp, and I am happy with the amps I have. I have worked on some of mine, and the PCB wasn't bad to work on (except the broken trace).
     
  8. Guinness Lad

    Guinness Lad Silver Supporting Member

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    I used to think all PCB amps wouldn't have the same harmonic complexity as PTP but after owning Tone king's and my present Guytron I think the losses you are speaking about can easily be overcome by the careful choosing the correct components to compensate for any losses due to capacitance.

    My Guytron has tube sockets directly mounted to the chassis but from what I have read Guy Hedrick decided to build the amps this way because they were more reiable then when he used the flying lead technique like Mesa.

    PTP amps look nice when done well (Victoria, Dr.Z etc...) but can also look like **** if done poorly. I will admit when I look at my amp I can't even imagine copying it but when I used to look at my Victoria I always thought building my own tweed knock off.
     
  9. pureoldsound

    pureoldsound Member

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    I think this is very subjective.....I've owned both PTP and PCB amps...
    Do I think one is better than the other I can't say as I have not owned to identical amp one with a PCB and the other PTP and compared them side by side. I used to have a Rivera Suprema and it sounded great (that was a PCB amp)....Then I went for PTP not because one was better than the other but because the amp that I wanted comes as PTP amp....I have a Silverface Pro-Reverb (PTP) that the clean sounds sound better than the Rivera, could it be because it is a PTP amp…I guess not just different design…..

    I contacted many builders and asked them the same question over and over, which one is better PTP and PCB…Their answer a good PCB with quality parts and well made will sound as good as any PTP. FUCHS is one example of that…..and I think FUCHs is highly regarded in this forum….

    Don’t quote me on this but Voodoo amps some Hex and Witchdoctor amps are coming out with PCB (you can still get them in PTP just need to make a special order)….They are highly praised on Harmony Central….They sound great……

    Like some have mentioned, PCB may be more consistent than PTP. Where as PTP will be easier to fix and modified. I don’t think (I could be wrong) that one PTP will sound exactly the same as the nest one. As far as I can understand it, the distance between resistors can make the amp sound different on PTP amp????
     
  10. aeolian

    aeolian Member

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    PCBs and larger, high power disapation components are a bit of a problem. Soldering and desoldering these from a PCB is a bit harder. Especially for folks not used to PCB rework and using large soldering irons meant for heavy terminals. There is a small bit of merit to the "repair" stigma of PCBs but it isn't necessary. Proper tools and training can remedy that.

    From a performance standpoint. There is no comparison. Hard wiring sucks. Of course, the PCB technology in most musical gear is 20 years old too. When I see statements like "PCBs have gotten better recently" I have to laugh. The PCB's in guitar amps aren't any different than a 20 year old low cost clock radio.

    I'm sitting here at a bench using a lab set up to communicate with a bunch of boards with 106MHz MPUs, downloading boot code. The set up has a hodge podge of ribbon cables and such. There is no way this could communicate with the boards main I/O's which operate at 4 GHz. That requires fairly sophisticated PCB technology. Which is nothing like the PCB techology in a 10 GHz internet router. If the "capacitance" of the traces were an issue, these frequencies would be rolled off. :) I tend to believe that audio requires 40-60 KHz bandwidth due to leading edge transients, as opposed to smooth sine waves that we can hear up to 15K or so. But that bandwidth is a far cry from gigahertz stuff. Wires have capacitance too. They also have much more series inductance. Coupling between wires is entirely random in a PTP amp. Hence the silverface instability that required the snubber caps on the output tubes.

    The boards I'm working with cost about a buck and a half in volume. At the very worst, in very small quantities of 10 or so, they cost $25. This is not prohibitive when compared to the labor of a PTP amp.

    Someday, probably in the boutique end of the market, someone will invest in a serious PCB. Then the technology might trickle down into "production" level gear. And we will all be the better. Except for the "techs" who don't keep up with the times, get smaller soldering irons, and learn how to use them.
     
  11. tonefreak

    tonefreak Member

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    This subject has been beaten to death, but this read from Andy Marshall of THD will shed some light:

    From Andy Marshall:

    Not all manufacturers choose to use PC boards just to save money. We use them for consistency more than for price, but making a somewhat affordable amplifier is a nice benefit. I don't think that someone should have to be a lawyer or Microsoft Millionaire to be able to afford a new amplifier that is hand-built, reliable and sounds and feels good to play.

    If a PC board is designed correctly and the correct components are used, the amplifier production should be absolutely consistent from one unit to the next. No re-routing of traces should ever be necessary to make an amp function or sound right. If you find it necessary to change and re-rout wires in your amps, then you are not in production, but are just making a series of unstable prototypes. Treble reduction to the point where it reduces the clarity of the amplifier is not an acceptable stabilizing technique for either a PTP or PCB amplifier.

    Recently, we got a call from a tech complimenting us on our old Plexi model amplifier (that we built between 1990 and 1995), but he said that it was just a little bit "stiff in the high-end" compared to a real Marshall Plexi. To back up his point, he told us that he had a real Marshall Plexi on the bench next to ours and was comparing the two side by side. What he did not seem to realize was that no two Marshall Plexis sound the same. They were terribly inconsistent with their component sources and values, not to mention the inconsistencies in wire routing.

    Taking a point to point or a turret-board amplifier, if one moves the wires around, the entire sound and character of the amplifier can change, often dramatically. This is a well-recognized phenomenon.

    If you understand these interactions well, you can design a PC board to sound and feel any way you want it to. Furthermore, every one will sound the same. How many times have you plugged into an old Marshall-50 watt head, only to be terribly disappointed by the sound and feel of the amplifier? While this may be caused by poor tubes, at least in part, inconsistencies in the internal layout of the amplifier often play a significant role.

    If you understand how one component affects the component next to it and how one trace affects the trace next to it, then you should be able lay out a circuit board correctly the first time, not by building 10 and picking the best one. Mind you, it takes many years of experience to develop the sort of understanding of the capacitive and inductive interrelations involved. In the old days, I did this for a living for other companies, designing circuit boards for the audio sections of amplifiers, mixing consoles, signal processing equipment, etc... While I am under confidentiality agreements with almost all of my former clients, I can tell you that there is hardly a professional recording studio in the US or Europe that does not have some audio circuit board with my layout in some piece of equipment. After a few hundred such projects, one develops an intricate understanding of how traces and components interact.

    A number of years ago, Guitar Player magazine did a review of one of our amplifiers. They stated that they, as a general rule, do not care for circuit board amplifiers, but also said that I had addressed every one of their concerns, and that they had nothing bad to say regarding our use of circuit boards. It felt good to see someone start to understand what it is that we do and why.

    Certain components throw a rather large field. Others do not. Some components are very susceptible to the fields from other components, while some are not. Components can affect the signal passing through traces, and traces can affect the signal passing through components. It ends up being an enormous network of positive and negative feedback between components within each other's sway. This is why the distance between specific components on the board and the physical orientation of the components relative to one another (rotational orientation, as well as lateral placement) cannot be ignored. Furthermore, which traces are parallel to one another and at what distance, which traces are perpendicular to one another and that what distance, and the amount of ground plane in-between them can seriously affect the overall sound and feel of the finished amplifier.

    Most people design circuit boards either haphazardly or for the greatest parts density/easiest and least expensive manufacture. Neither of these methods belongs in a high-end amplifier, and such approaches give PC Board designs a bad name.

    If you know what you are doing, a thicker board is better than a thinner board (ours are .093" or 3/32", most are .062” or 1/16”) and that thick copper is a good idea (ours is 4 oz, most use 1/2 oz or 1 oz). One of the greatest problems facing most circuit board amplifiers is board flex. Board flex creates metal fatigue in the copper. As the copper cannot really "break", it just crystallizes and makes tons of noise. This is much worse in combo amps, of course. We go to the trouble to support our boards ever few inches. Our design standard is that 100 pounds of force on a 1/4" diameter probe should not be able to flex the board more than 20 thousandths of an inch at any point on the board. All of our amps designs must pass this test. For comparison, most Marshall and Fender circuit boards would break under such force, and would flex more than 3/8 of an inch just before breaking.

    Through-plated holes are an absolute must, with solder pads on both sides. This makes it much harder for a repairman to inadvertently lift a pad or a trace by overheating or from poor technique. The way that we have addressed this is to start with boards that are clad with 2 oz copper, and in the through-hole plating process we add another 2 ounces. This leaves us with traces and ground planes of 4 ounces, and through plated holes with 2 oz copper in the holes themselves. I have seen some other people start with 3 oz copper, plating on an additional 1 oz, and I have not like the results I have seen. The through-holes pull out too easily.

    Contrary to popular belief, “Orange Drop” film capacitors are far from great. They are OK for certain position in certain circuits, but their consistency from one to the next is atrocious. Maybe this is part of why so many people who use them in PTP amps find the need to make wire adjustments. This is a big part of what I mean by using the right components.

    As for PCB solder joints becoming problematic with time, this is no more a problem than on PTP. A good solder joint with absolute minimum stress on it (using the right component with the right lead length and the right mounting technique) will yield the longest and most consistent life. Assuming that the flow-solder machine is correctly set up, the right solder, right flux, right solder temperature, right flux temperature, right pre-heat, right cooling, etc… are done, a flow-soldered board will last longer and have higher quality solder joints than a hand-soldered board. If you doubt this, ask yourself the following questions: How do you decide what solder to use? Do you choose SN60, SN63, SN96, Savebit or some other? How do you decide what flux to use in your solder and how much? How do you decide what temperature to set your iron at? It all makes a HUGE difference in the quality and consistency of your solder joints. If you cannot answer all of these questions, then you cannot even have a clue about the long-term consistency and life expectancy of your products. This, along with countless other points, is part of what separates the hobbyist from the professional.

    In a PTP amp, the entire surface of the solder joint is exposed to air, and thus, to corrosion. In a through-plated PCB amp, only the top and bottom surfaces of the solder joint are exposed to corrosion, not the majority of the joint, which is within the through-hole, which is where most of the contact is made.

    We use only FAA-approved aircraft assemblers in every stage of our manufacturing. They have to understand all of these points completely. The FAA is even more stringent than the military. Also, the aircraft industry is just about the only industry left that uses PCBs for the electronic components wired to chassis-mounted electro-mechanical components like the controls and connectors. They do this because countless FAA tests have shown that devices built this way last longer and are more reliable and consistent than any other method, even taking cost out of the picture entirely. This is, of course, why we use the exact same methods.

    In closing, I absolutely believe that circuit boards, when they are well-designed and laid out, are in all ways superior to other manufacturing techniques when one is building amplifiers in quantities. If I did not believe this firmly, I would not be doing it. This said, I think it is a terribly expensive and cumbersome method for hobbyists to attempt. If you don't have a great deal of experience under your belt designing circuit boards, you won't like the results. Point to point and turret-board techniques offer the hobbyist and the small-scale amp shop the opportunity to easily tweak their designs, as is so often necessary. So, unless you're going to be building 50 amps a month or more, it is probably best to stay away from circuit boards.
     
  12. riffmeister

    riffmeister Gold Supporting Member

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    I like single channel PTP amps. Juice to the Max.
     

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