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Point to Point Wiring

Discussion in 'Amps and Cabs [BG]' started by thobbinghotrod, Apr 11, 2009.


  1. I just took apart a little 60's SS practice amp to clean a pot and found a point to point chassis, maybe six components in the whole thing.

    What would a modern Solid State amp sound like with the very best components. I know that even the boutiques skimp here and there on a few things, but a home builder wouldn't have to skimp.

    Throw in a tube pre and you've got the best amp in the world, or is someone already doing point to point without tube power?

    I'm thinking about each component, a home builder can pay a few cents more per part to go from cheap to spectacular even in the solid state power section.

    I'm just curious, I'm not planning on building anything.
     
  2. Just to clarify, by boutique I meant factory made amps like Thunderfunk or Aguilar etc.
     
  3. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Contemporary solid state power amps are at least 10x more complicated, and the sheer amount of wiring would make P2P prohibitive. Even modestly priced amps are already spec'ed for levels of distortion below the threshold of audibility.

    For the DIY'er, issues such as thermal design and safety loom large, and many schematics published online lack features required for portable gear, such as overload protection.

    Class-D depends on tight printed circuit layout, and is out of reach for DIY'ers, unless we buy ready-made modules.
     
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    To be fair, I should mention that it might be possible to lower the noise floor by a few dB on many amps by choosing premium op amps.
     
  5. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    What's intrinsically superior about p2p anyway? Mainly nostalgia value - and in amps that are simple enough to use it in the first place, repair.
     
  6. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I am speculating here, but maybe it is more reliable where there is some heat being generated, such as at tube sockets. Also, for the local boutique builder, P2P is probably cheaper and easier to customize and repair. Designing a printed circuit for large components, high voltages, vibration, and heat, requires some engineering know-how.
     
  7. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Yep.
     
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Sonically, nothing. All amps were once built that way only because printed circuit boards didn't yet exist. PCs are a pain to work on, but they're also a lot less expensive to produce. So long as the amp doesn't need repairs PCs are the better deal.
     
  9. Thanks for sorting that out, I was wondering why there were so few components in my Kalamazoo, made in the 6o's by Chicago Instrument Corp.
     
  10. Early PCB's didn't get along well with the heat from tubes. I find PCB's actually easier to repair than some p2p. Anybody that has had to work on a Vox AC30 with Top Boost will understand what I'm talking about?
     
  11. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Hopefully that rhetorical question was noted as such ; }
     
  12. Yessssss:cool:
     
  13. Kindness

    Kindness

    Oct 1, 2003
    Chicago
    Point to point? Ick!!!

    IMG_3424.

    I prefer turrets or eyelet boards.

    IMG_4447.
     
  14. Good examples.
     
  15. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The cop-out answer is low fidelity. However... there was a time period when engineers were just getting up to speed with transistors, and circuits were designed which simply used topologies similar to existing tube designs. This included continued use of inter-stage transformers.

    I suspect that the complexity of circuits increased as engineers came up with techniques to address the circumstances of solid state design, along with improved understanding of what could be accomplished with negative feedback. Also, designers have gotten more persnickety about stability, safety, and circuit protection. And components have gotten cheaper.

    Of course today, at least for the power level of that Kalamazoo amp, the sky's the limit on circuit complexity because it's all hidden in an IC, and you might be able to get pretty close to a half dozen components once again!
     
  16. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Hey, do you have the schematic for the Kalamazoo? It should be stapled or pasted inside the amp cover. That would be a nice history lesson.
     
  17. FFTT

    FFTT

    Mar 15, 2009
    I'm glad you showed the difference in two hand wired chassis.

    One true point to point and the other turret board.

    The primary benefit to both of these configurations is that
    there are no critical proprietary circuit boards to worry about.

    On the road or ten years down the road, you know that any
    competent amp tech can fix or upgrade your amp as needed.

    My Bad Cat is true point to point and my Reeves is turret board, both
    built to last decades with proper care and feeding.

    My '73 SVT and my '93 USA Fender Blues Deluxe both had
    problems in the printed circuit board.

    The SVT needed repair twice in 8 years and while the
    Blues Deluxe remained fairly trouble free for 12 years,
    the problem in the circuit board was essentially deemed un-repairable
    with the cost of replacing the circuit board with labor
    exceeding the value of the amp. My replacement USA Blues Deluxe
    also developed a problem in the circuit board due to a much less
    serious loose solder joint on the circuit board.

    Many techs may think of true point to point as a rat's nest
    to work with, but we have also learned from experts like
    Ken Fisher that the finest details in the way the amp is assembled
    may have a dramatic change of the amp's tone.

    The kind of wire, length of wire, routing of the wire
    as well as selection and placement of the individual components
    all have an effect on the amp's tone and responsiveness.
    This is why Ken's Trainwreck amps are so highly prized.

    What many amp techs like my father found was that
    the only problem with hand wired amps was the inconsistency
    once the amp went into mass production, where human error
    accounted for loose solder joints, crosstalk and noise due to improper
    routing of the circuit and cost cutting measures in the quality of components
    to improve the companies' bottom line.

    We're fortunate to have 50 years of touring experience
    to help us determine which design to go with for roadworthiness.

    Of all the classic hand wired circuits out there, the Hiwatt, military spec turret board circuits remains the most rugged and trouble free in design and execution.

    Vintage Fender amps generally hold up very well too, while
    original Marshall and Vox circuits were more like owning a British sports car.
    When they ran right they were wonderful, as long as you could afford to keep them
    running right.

    Manufacturers of PCB amps will argue that computer controlled PCB design
    improves consistency on the assembly line while reducing labor costs.
    This may be true in some cases as long as the execution of the design
    is not undermined by final hand assembly or the failure of individual
    third party circuit components.
     
  18. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Those are good points about the classic amps. In the day, your friendly neighborhood tech or even a hacker like me could take a pretty good stab at fixing any tube amp -- often without a schematic -- drawing from a modest collection of parts.

    It has even taken solid state amps some time to evolve decent circuit board designs. I have seen plenty of older solid state amps, with scorched circuit board material under the emitter resistors. And when these need repair, half the job is mending the damage done to the board by the previous tech.

    A friend of mine worked in an amp factory. The tube chassis were wired in Mexico, and installed in the cabinets in Chicago. My friend was part of the group that tested the amps. He said they came from Mexico with no consistent color code for the wiring, and many mistakes that had to be re-worked.

    But I won't haul a 60-pound amp just for the sake of it being repairable 30 years from now. And there is a flip side. When my amp needed a repair recently, the postage for mailing it to the factory was less than I would have paid for the replacement part.
     
  19. Interceptor

    Interceptor Supporting Member

    Mar 29, 2005
    Madison, WI
    I've been doing component level electronic repair for more than 30 years. Not much of it has been MI, my specialty is RF products made for the broadcasting industry.

    The stuff I like working on the most is circuit board based, second is the turrent style of construction. I really don't enjoy working on dead bug construction. My constant goal is to perform a repair without leaving any footprints. That goal is beyond reach working on some of the MI gear I've seen with point to point wiring without causing more problems. There are times when that perfectionist approach isn't the one to use, and that is when the work will stress other components due to heat or the pulling needed.

    My feeling is the average tech can perform a repair faster and with less collateral damage in circuit board or turrent.

    There are audible differences between the styles. Prototype a circuit using dead bug and then lay it out on a proper circuit board - it'll perform a little different. Not always better, not always worse.
     
  20. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Been there, done that! Ain't got no T shirt though! Worked on a lot of Vox amps back in the day. I still think the AC30TB is arguably one of the best guitar amps ever made.

    Paul
     

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