What is the theory behind tube spacing? Is there an optimum/standard distance observed for tube placement, maybe dependent upon type/power being used? Given the dynamics of tubes, what would cause interference between them, thus defining this spacing?
Thanks!
Tube Spacing
Moderators: pompeiisneaks, Colossal
Re: Tube Spacing
I think the 2 primary issues are
1) lead dress. The preamp tubes need to be spaced so that the leads to the board are dressed well.
2) heat. The power tubes need space for dissipation. Usually about 1.5 times the diameter of the tubes is good.
1) lead dress. The preamp tubes need to be spaced so that the leads to the board are dressed well.
2) heat. The power tubes need space for dissipation. Usually about 1.5 times the diameter of the tubes is good.
Re: Tube Spacing
> Given the dynamics of tubes, what would cause interference between them, thus defining this spacing?
In audio amps, it is almost always about fitting the capacitors and resistors nicely.
Vacuum tube computers have many more tubes and much simpler coupling networks between them. Some arrays were built with socket flanges nearly touching. In the dying days of digital tubes they did some stupidly compact stuff.
Try that with a geetar amp, and you have a 5 inch row of tubes but still a 9 inch row of caps and resistors to connect, and a real pain to wire the sockets or replace a tube.
Or stack two turret boards, and discover that any tweak is a major pain.
Coupling between tubes is, IMHO, a non-issue. Precision stereo equipment expects nearly no crosstalk between the two sides of a twin-triode, and can usually get it. There will usually be far more coupling leaking around the turret board than between tubes.
I have built very compact, and usually regretted it.
1.5 diameter may be a minimum for comfort. My experience is that 2 or 3 diameters is more comfortable to build and maintain.
Don't try to cram 10 pounds of sand in a 5 pound bag. Get all your capacitors and resistors (or paper sketch or cut-outs). Line them up in approximate order from input to output. Yes, you can tuck a 0.25" resistor in the space between/under two 0.9" capacitors, but that's a pain to maintain. Leave yourself space for emergency stage-side repairs in dim light without your best needle-nose handy. When you have all the board-parts rough-placed, throw the sockets next to them near the parts they must connect to. Push them a bit so the spacing is equal, for "looks" and so the gal on the hole-punch (or you) can use a simple jig and get it right.
In audio amps, it is almost always about fitting the capacitors and resistors nicely.
Vacuum tube computers have many more tubes and much simpler coupling networks between them. Some arrays were built with socket flanges nearly touching. In the dying days of digital tubes they did some stupidly compact stuff.
Try that with a geetar amp, and you have a 5 inch row of tubes but still a 9 inch row of caps and resistors to connect, and a real pain to wire the sockets or replace a tube.
Or stack two turret boards, and discover that any tweak is a major pain.
Coupling between tubes is, IMHO, a non-issue. Precision stereo equipment expects nearly no crosstalk between the two sides of a twin-triode, and can usually get it. There will usually be far more coupling leaking around the turret board than between tubes.
I have built very compact, and usually regretted it.
1.5 diameter may be a minimum for comfort. My experience is that 2 or 3 diameters is more comfortable to build and maintain.
Don't try to cram 10 pounds of sand in a 5 pound bag. Get all your capacitors and resistors (or paper sketch or cut-outs). Line them up in approximate order from input to output. Yes, you can tuck a 0.25" resistor in the space between/under two 0.9" capacitors, but that's a pain to maintain. Leave yourself space for emergency stage-side repairs in dim light without your best needle-nose handy. When you have all the board-parts rough-placed, throw the sockets next to them near the parts they must connect to. Push them a bit so the spacing is equal, for "looks" and so the gal on the hole-punch (or you) can use a simple jig and get it right.
Re: Tube Spacing
PRR,
Thanks for your post. I've had something weird (for me, at least) happening to one of the tubes in my amp, which is QUITE compact. The glass wall of one of the tubes was "pushed in" a bit, like someone had pushed it in with their finger.
I was also getting sparks near the on/off switches when I opened it up to check why it was blowing fuses. I had recently changed the PT, but now I think I have a burnt or about to burn OT too. It has some bubbles in the paint, which I guess were caused by the heat. Although the amp never sounded so good, it was amazingly hot. Do you think the heat generated by tubes in good working order would be the cause of all this?
Thanks
Thanks for your post. I've had something weird (for me, at least) happening to one of the tubes in my amp, which is QUITE compact. The glass wall of one of the tubes was "pushed in" a bit, like someone had pushed it in with their finger.
I was also getting sparks near the on/off switches when I opened it up to check why it was blowing fuses. I had recently changed the PT, but now I think I have a burnt or about to burn OT too. It has some bubbles in the paint, which I guess were caused by the heat. Although the amp never sounded so good, it was amazingly hot. Do you think the heat generated by tubes in good working order would be the cause of all this?
Thanks
Re: Tube Spacing
Which tube appeared melted? How long has it run hot? Do the output tube plates glow any shade of red? Have you checked bias values?
Re: Tube Spacing
I think it was V4, the one to the right, if you're looking at the amp from its back. Yes, the power tubes were almost read, a very dark orange. And no, strangely enough, the bias read normal, which is about 50 mv.
Re: Tube Spacing
> The glass wall of one of the tubes was "pushed in" ... getting sparks near the on/off switches ... I had recently changed the PT... I think I have a burnt ..OT ... it was amazingly hot. ...the power tubes were almost read, a very dark orange. And no, strangely enough, the bias read normal, which is about 50 mv.
So you changed the PT, current seems OK, everything is too hot, but not exploding.
It sounds like you screwed-up the PT wires and are getting double normal voltage.
> I think it was V4, the one to the right
Since you don't say what amp this is, they are all laid out different, nobody remembers all the layouts.... this says nothing.
So you changed the PT, current seems OK, everything is too hot, but not exploding.
It sounds like you screwed-up the PT wires and are getting double normal voltage.
> I think it was V4, the one to the right
Since you don't say what amp this is, they are all laid out different, nobody remembers all the layouts.... this says nothing.
Re: Tube Spacing
Sorry. It's an Alessandro Hounddog.
Re: Tube Spacing
I would be very nervous if tubes glowed orange and would make a thorough examination of the P supply, (if I was you). But then again, new tubes and trannies DO make a dent in MY budget. <smile>.