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Thread: shorter wiring to/from preamp tubes; better board design?

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    shorter wiring to/from preamp tubes; better board design?

    If we took a bit wider fiberglass board, drilled a few holes along the centerline, a bit larger diameter than the preamp tube sockets, then rearranged the turrets so that they were close to the socket pins, we could shorten or eliminate a lot of the wiring between pin sockets and components/turrets. If the hole is big enough, but not too big, it would not have a thermal coupling with the board as well.

    I could understand this given technology of, say 40's-60's, but today, with CNC machines and such, wouldn't this be very easy to do?

    I did a couple of hand sketches, and could get a few components between socket pins and turrets mounted around the tube hole, and freed up some space on the board as well for filter caps and dropping resistors.

    Has anyone tried this with one of the classic tube circuits, e.g. Fender Deluxe, Pro, Vibrolux, or Marshall or Vox? With so much less wiring, it seems like a lot easier to build as well. Still get benefits of a board and no point to point wiring, but very little 'hookup wire' used.

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    Sure - why not? You describe one of many options that lead to shorter wires and simpler construction. Both are desirable (IMO) and yes, we have better methods, materials, and tooling than 50 yrs ago. Many modern amps use these ideas and more. What you describe reminds me of the THD amps. They cut circles in PCBs for tube socket pins and short (1/4") jumpers made connections. Worked well, as far as that goes. Unfortunately, their PCB's had excessively long traces on them that negated many of those short connection benefits. Construction is complicated in that everything affects everything else and good construction requires careful planning and weighing of options to find an optimal combination of compromises.

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    Actually we had better ways even 80 years ago - point to point. If it was critical to keep leads short, as in RF circuits, that was the simplest way. After all we had radio and even TV circuits before world war 2.

    But ours are just guitar amps, and my personal view is you have a solution looking for a problem. meaning we do occasionally find lead dress problems, but those are easily solved, and the plain old eyelet boards with those over-long wires have been working qquite well ever since they started using them.

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    I did a repair on a radiogram amp from maybe the late 50s/early 60s that was built in a similar fashion. That particular amp was PCB construction. It had holes in the board to mount regular tube sockets and the terminals were fanned out and soldered to the pads. Very little wiring because all the tubes were mounted in this way - including 2xEL84 which had cooked the SRBP board and lifted the pads.

    I can see this being a convenient way to build a preamp board along with turrets or eyelets and had it at the back of my mind to do a hi-fi build using this method. The only reason being that when I sell to this market the buyers want pictures of the inside of the amp and it would look neat.

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    Bent Member Chuck H's Avatar
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    This is an idea I've toyed with. What I found, from a design perspective, is that you still need flying leads to the input jacks, panel controls, effects loop, reverb tank jacks, foot switch jacks, transformers, common ground, etc. There are some circumstances where it may improve things a little bit, but not without undue complication an/or detriment to some other lead dress conundrum.

    And, FWIW, I've seen it done in PCB amps where the tube sockets are chassis mounted. I can't remember the model/s I saw like this though.

    What I HAVE done is design the board layout and tube locations in tandem. Rather than just row the tubes up along the back of the chassis and then design the board around tube location. So, for example, I may have the input tube very near the input jack on the opposite side of the board from most vintage designs. In one of my Fender/BF type topology designs this means the second triode for the tone stack is also RIGHT THERE and I used a five point terminal strip to mount the tone stack components. Now over all lead length for the first two preamp stages is MUCH shorter than vintage designs.

    I will also note that this is for better or worse. Because sometimes it's the anomalous inductive/capacitive loops in a circuit, the components that aren't really there, but are hidden in lead dress and cross talk that give a particular design it's mojo. That is, if you want the tone of a particular vintage design you should not try to "improve" it in any way. It will sound different. So in the end you didn't get the tone you were after. I'm intimately familiar with this phenomenon. It's been said many times here, there's more to an amp than the schematic.

    Here's an example the design concept I mentioned. G=ground. Because I run individual ground leads without daisy chains the grounds are located under the board. Since I'm running so many ground leads this makes for a neater appearance.

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    Quote Originally Posted by Chuck H View Post
    ...What I HAVE done is design the board layout and tube locations in tandem. Rather than just row the tubes up along the back of the chassis and then design the board around tube location. So, for example, I may have the input tube very near the input jack on the opposite side of the board from most vintage designs. In one of my Fender/BF type topology designs this means the second triode for the tone stack is also RIGHT THERE and I used a five point terminal strip to mount the tone stack components. Now over all lead length for the first two preamp stages is MUCH shorter than vintage designs.
    Excellent.

    Because just clicking "Like" didn't seem sufficient.

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    Quote Originally Posted by mikepukmel View Post
    If we took a bit wider fiberglass board, drilled a few holes along the centerline, a bit larger diameter than the preamp tube sockets, then rearranged the turrets so that they were close to the socket pins, we could shorten or eliminate a lot of the wiring between pin sockets and components/turrets. If the hole is big enough, but not too big, it would not have a thermal coupling with the board as well.

    I could understand this given technology of, say 40's-60's, but today, with CNC machines and such, wouldn't this be very easy to do?

    I did a couple of hand sketches, and could get a few components between socket pins and turrets mounted around the tube hole, and freed up some space on the board as well for filter caps and dropping resistors.

    Has anyone tried this with one of the classic tube circuits, e.g. Fender Deluxe, Pro, Vibrolux, or Marshall or Vox? With so much less wiring, it seems like a lot easier to build as well. Still get benefits of a board and no point to point wiring, but very little 'hookup wire' used.
    As Chuck H said, you still end up with flying leads. In other words, you can get some components closer to the tube sockets, but overall, the components themselves are spread out more. Unless you're exceptionally clever about layout, you need more flying leads to connect them.

    I do like Chuck H's idea of putting the input tube close to the input jack.

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    Supporting Member loudthud's Avatar
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    It's been a while, but there were some pics of layouts like this on Amp Garage. IIRC it was a Trainwreck clone.

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    Quote Originally Posted by loudthud View Post
    It's been a while, but there were some pics of layouts like this on Amp Garage. IIRC it was a Trainwreck clone.


    I always worry about this and take it a little personal when it happens because my design is not UN TrainWreck like. And I always feel compelled to mention that I designed this amp before there was any public disclosure of the TrainWreck circuit. But, to be fair, I did (later) take one aspect from the TW circuit and A/B it with my circuit. I liked the TW idea better so I adopted it. Strictly a matter of tone and going with what sounded right. Other TW aspects were rejected with the same criteria. Anyway...

    I know the layout doesn't look especially TW, but when I saw the TW circuit I was startled at how close it actually was to my amp on a fundamental level. It use to be a bit closer actually, but I've made changes since then. At this point I think my design is much more versatile and user friendly than the TW, but that's just my prideful opinion

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    Quote Originally Posted by Chuck H View Post


    I always worry about this and take it a little personal when it happens because my design is not UN TrainWreck like. And I always feel compelled to mention that I designed this amp before there was any public disclosure of the TrainWreck circuit. But, to be fair, I did (later) take one aspect from the TW circuit and A/B it with my circuit. I liked the TW idea better so I adopted it. Strictly a matter of tone and going with what sounded right. Other TW aspects were rejected with the same criteria. Anyway...

    I know the layout doesn't look especially TW, but when I saw the TW circuit I was startled at how close it actually was to my amp on a fundamental level. It use to be a bit closer actually, but I've made changes since then. At this point I think my design is much more versatile and user friendly than the TW, but that's just my prideful opinion
    Chuck, youíre my EL84 brother here at the forum. While Iíve only ever heard clips of Trainwrecks, the trainwreck liverpool is the best sounding amp Ive ever heard. Definitely an inspiration for me to experiment and design for with Ď84s.
    I hope I get the chance to play one of your amps someday

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    Bent Member Chuck H's Avatar
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    Well how can NOT give a thumbsup for that? But it's unlikely. I don't get any orders anymore and I've only built five of this model. Actually four. One is my personal amp so it doesn't count. No one is ever going to 'run across' one somewhere. They're all in different packages too. That is, different head or combo designs. Only two have logo's or model names on them. I never made any money doing it and I only use my bench for hobby purposes. So it's not like I'm at my bench all day anyway and building amps when not repairing. Which is what some guys do. But I've been anxious for someone here to try one of my amps just so they could give a second person report to everyone else here It's not an ego thing. Honestly. More like a desire for personal validation for the time I spent on it.

    As to el84 brothers. I'm in. Easily my favorite tube to design around. I'm familiar enough with what to expect from that tube that I actually find myself at a loss when designing for other types. Which I've enjoyed actually. Always something new to learn. Even if I do it in my own, slow time.

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    I've been looking over at Amp Garage and you can't search for "PCB". There are a couple of hits for "Printed Circuit" and a couple of pics came up for "layout". The ones I saw weren't very good. One problem most software has is that you can't rotate components except for 90 degree increments. So you have to create a new footprint if you want a component at an angle.

    I too would like to get some feedback on some of my designs. Send me a PM (anyone) if you're coming Dallas way. I want to do one of those videos where you start playing to an open field and a bunch of cows show up.

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    Quote Originally Posted by loudthud View Post
    I've been looking over at Amp Garage and you can't search for "PCB". There are a couple of hits for "Printed Circuit" and a couple of pics came up for "layout". The ones I saw weren't very good. One problem most software has is that you can't rotate components except for 90 degree increments. So you have to create a new footprint if you want a component at an angle.

    I too would like to get some feedback on some of my designs. Send me a PM (anyone) if you're coming Dallas way. I want to do one of those videos where you start playing to an open field and a bunch of cows show up.
    I used to live in Dallas (briefly), on Swiss Ave. If I ever find my way down ther again (It'll probably be on my way to Austin) I'd definitely be interested in checking out your amps/shop. I'm interested in what you've developed in your solid state designs. Plus, you've been in the game long enough that you strike me as the kind of dude that has a good stash of great test equipment.

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    Quote Originally Posted by loudthud View Post
    I've been looking over at Amp Garage and you can't search for "PCB". There are a couple of hits for "Printed Circuit" and a couple of pics came up for "layout". The ones I saw weren't very good. One problem most software has is that you can't rotate components except for 90 degree increments. So you have to create a new footprint if you want a component at an angle.

    I too would like to get some feedback on some of my designs. Send me a PM (anyone) if you're coming Dallas way. I want to do one of those videos where you start playing to an open field and a bunch of cows show up.
    Yeah, put a huge amount of effort into getting some things drawn out (only a layout and not a schematic even), re bending and rotating components. But, for, say a turret board, we can place turrets anywhere we want and stick a couple of holes in the board at the right places, so that the sockets mount to the chassis and not the board (get around heat, mechanical problems etc)

    I didn't think flying leads could be gotten rid of completely, but quite a few. I have a few hand sketches, moved components around, so that they met with turrets on the board, but the flying leads towards the pots and jacks were not so much different than the 'standard' Fender/Marshall/Vox/Ampeg period designs. Not like Im going to make anything better than was made over the past 75 years, but cool stuff to tinker with. And, wiring tends to be my weak point anyway, so less I have to do . . .

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    Quote Originally Posted by Chuck H View Post
    This is an idea I've toyed with. What I found, from a design perspective, is that you still need flying leads to the input jacks, panel controls, effects loop, reverb tank jacks, foot switch jacks, transformers, common ground, etc. There are some circumstances where it may improve things a little bit, but not without undue complication an/or detriment to some other lead dress conundrum.

    And, FWIW, I've seen it done in PCB amps where the tube sockets are chassis mounted. I can't remember the model/s I saw like this though.

    What I HAVE done is design the board layout and tube locations in tandem. Rather than just row the tubes up along the back of the chassis and then design the board around tube location. So, for example, I may have the input tube very near the input jack on the opposite side of the board from most vintage designs. In one of my Fender/BF type topology designs this means the second triode for the tone stack is also RIGHT THERE and I used a five point terminal strip to mount the tone stack components. Now over all lead length for the first two preamp stages is MUCH shorter than vintage designs.

    I will also note that this is for better or worse. Because sometimes it's the anomalous inductive/capacitive loops in a circuit, the components that aren't really there, but are hidden in lead dress and cross talk that give a particular design it's mojo. That is, if you want the tone of a particular vintage design you should not try to "improve" it in any way. It will sound different. So in the end you didn't get the tone you were after. I'm intimately familiar with this phenomenon. It's been said many times here, there's more to an amp than the schematic.

    Here's an example the design concept I mentioned. G=ground. Because I run individual ground leads without daisy chains the grounds are located under the board. Since I'm running so many ground leads this makes for a neater appearance.

    Now *that* is a cool design!

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