Amp Guts Photos - Official Thread - Lets see those pics

[beans-on-toast]

I highly recommend that anyone getting into building, download a free copy of Eagle or Kicad (there are many others) and learn how to design a PCB. Free packages have size limitations but modular boards can be used. Circuit boards aren’t as expensive as one might think. Check out OSHpark for US production.

 

[BogeyBass]

Probably a downfall of point to point or turret construction. Is lead stress from heavy components. Such as large ceramic resistors as mentioned.
Downfall of pcb is direct mounting and excessive heat going to the board.
Boards can be slotted for heat venting. Or large vias with no connection basically making vent holes.
Otherwise the stressed leads and heat situation was solved long long time ago for point to point/ or terminal strip construction.

Chassis mount resistors. not only use the chassis for heat dissipation, but there is no lead stress since the ceramic resistor is held in place with metal clips. also mounted to the chassis. no lead stress and superior heat dissipation. likewise as many high end designs have done. chassis mount resistors and chassis venting for the resistor

With few ups and downs of tube pcb design. for the most part consistency and significant noise reduction can be achieved using pcb. specially with 9 pin pre tubes
and again hardly ever done. but board slotting or large unused vias or just actual venting holes. wanna argue cool....check out Russian military equipment or any well vented chassis design. the boards and chassis are vented. its really just that simple

 

[BogeyBass]

I never understood the logic (?) of pumping the hot air from the heatsinks right into the rack that the amp is mounted inside of.

yup turd design. side to side wind tunnels work fine with open racks. open racks offer better cooling and more associated with permanent installation like computer rack / server.

for transportable rack system requiring side walls. front to back wind tunnel is ideal.
putting the transformer inline with the fan is a notable decision, since transformer is exposed to forced air. then again Ampeg likes using bare minimum transformers and they are getting cooked.

 

[beans-on-toast]

Turret or eyelet construction offers support for components. No problem there. A lot of military and aerospace units used turrets. So did test equipment made by companies such as Tektronix and HP. Beautiful ceramic supports. It’s how it was done. The problem is, assembly is expensive.

One big problem with point to point is repair. Sometimes you have to remove wires and other components to get at one at the bottom. This could set off a chain of replacing wires and components. Terminal boards were often cheap. There are better ways.

 

[Mr. Foxen]

If you are laying out components right in a point to point amp, it pretty rapidly stops being point to point. The right place to be pretty frequently isn't between points.

 

[Leo was right]

DIY point-to-point project and commercial manufacturing are different ball game, either can be done wisely. My Boogie have a PCB but all pots are connected thrue wires to remove stress on solders, this is a good idea. In the same, we cannot say that Fender point-to-point wiring thrue eyelet are failure prone, very reliable IMHO.

 

[tubedude]

Fender amps are not point to point. They are assembled on eyeletted fiberboard, that sometimes becomes a semiconductor.

 

[Leo was right]

Fender amps are not point to point. They are assembled on eyeletted fiberboard, that sometimes becomes a semiconductor.

I called eyelet board: Point-to-point, probably wrongly, sorry I am not english native. Never heard about semiconductor effect on fiber board, mine work perfectly (44 years old).

 

[tubedude]

I called eyelet board: Point-to-point, probably wrongly, sorry I am not english native. Never heard about semiconductor effect on fiber board, mine work perfectly (44 years old).

Some of them become conductive after decades. Whenever Fenders have odd issues, check the fiberboard for conductivity. I know the first one i came across thirty some years ago had me stumped for a while.

 

[Leo was right]

Some of them become conductive after decades. Whenever Fenders have odd issues, check the fiberboard for conductivity. I know the first one i came across thirty some years ago had me stumped for a while.

Thanks I'll check it, I caught a similar problem few years ago on a whirlwind stage snake in the multi-pins isolator becaming partly conductive after years, doing strange behaviour with the phantom 48v. On high impedance circuit it can become tricky.

 

[Leo was right]

Some of them become conductive after decades. Whenever Fenders have odd issues, check the fiberboard for conductivity. I know the first one i came across thirty some years ago had me stumped for a while.

Do you remember which generation of Fender amps are doing the symptome?

 

[rufus.K]

Im going in and checking

for fiber board conductivity now

 

[Mr. Foxen]

Do you remember which generation of Fender amps are doing the symptome?

The black fibreboard ones. Because they decided the board was ugly, so dyed it black. With carbon dye they is conductive when exposed to moisture.

 

[Jeff Scott]

Some of them become conductive after decades. Whenever Fenders have odd issues, check the fiberboard for conductivity. I know the first one i came across thirty some years ago had me stumped for a while.

The black fibreboard ones. Because they decided the board was ugly, so dyed it black. With carbon dye they is conductive when exposed to moisture.

I have first-hand experience with this. In one case the whole board was replaced with a repro one, in the second case, I sold the amp and never looked back.

 

[beans-on-toast]

Spraying cleaners inside the amp where they shouldn’t go doesn’t help over time. In part, it depends on the board material and how close the eyelets are.

 

[rufus.K]

YAY.. no conductivity on this one

 

[Leo was right]

Nothing is simple, I made a search on Google image to see if mine is black, but all inside picture I found, the board is black, so...I don't know. I should check with a meter.

 

[12bass]

ive listened to hundreds of opamps, likewise enjoyed testing and playing around with majority of the designs my father did for Fairchild and National Semiconductor. With bass its just completely non audible. Only exception would be how much noise and hum is involved and that is mainly power supply design. other than that very basic understanding of gain and poor circuit values that can load down and cause very basic distortion. Rather obvious clipping or yes poor sound quality. If " opamp" swapping or rolling causes a audible difference. more than likely yes the " better" opamp just fixed a crap design. And the original opamp was fine. And agreed most the sponge or turd of a design is to many stages and poorly designed stages.

Haven't listened to hundreds of different op amps, but likely dozens. Much of my auditioning takes place with AKG K702 headphones or my true 3-way fEARful cabinet. Both are more revealing than standard bass gear. I also have Q-tuner pickups in my Rapture 5 and Lane Poors in my Hamer 12-string, which means that my basses produce more upper overtone content than most, certainly much more than a P-bass with the treble rolled off. Under these conditions, it is easy to hear the difference in sound between an ADA4627-1 and a TL072. Through a single 15" with a low bandwidth bass amp and a muddy sounding bass, not so much....

 

[12bass]

Maybe it comes off as arrogant, but I don't know how to say it honestly any better. I designed the amp line in a way that appeals to practical players. Since the whole line is well regarded by real world players, to me that's all that really matters. I frankly don't care about your "better" way of doing things because my philosophy is different than yours, and it's my design to live and die by.

If you are convinced that you have a better way, there's nothing stopping you from designing and producing a better mouse trap.

To clarify, I was not asking, or suggesting, that you design a bass amp specifically for me. What I was saying is that it would be interesting to hear something like a D-800 or WD-800 with a "pure direct" option which bypasses unnecessary op amp stages. The idea is that you push a button, and it sends the signal directly from the input stage to the power amp sort of thing. I meant that in terms of a test article, an experiment, to see if any differences would be audible by people who were interested in giving it an audition. If having several op amps in the signal path actually makes a difference to the sound, such a test should, in principle, be revealing.

 

[fdeck]

To clarify, I was not asking, or suggesting, that you design a bass amp specifically for me. What I was saying is that it would be interesting to hear something like a D-800 or WD-800 with a "pure direct" option which bypasses unnecessary op amp stages. The idea is that you push a button, and it sends the signal directly from the input stage to the power amp sort of thing. I meant that in terms of a test article, an experiment, to see if any differences would be audible by people who were interested in giving it an audition. If having several op amps in the signal path actually makes a difference to the sound, such a test should, in principle, be revealing.

It might be possible to do this through the effects loop. Of course gain matching is necessary, which is impossible if the preamp has any kind of baked in tone voicing.

I believe people have done this kind of test by chaining numerous op amps together, but I have no way of finding a description of how it turned out.