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AC30 trany layout

9/12/1997 7:36 AM
Steve Keay	AC30 trany layout Hi,, Could anyone with experience laying out a DIY AC30 please give me some advice/pitfalls to watch out for in laying the tranys, choke, and tubes out so I can avoid any unobvious problems??? I know the power trany gets pretty warm on these amps but does it radiate EMF at all??? How about the OT??? I have no room to spare so every sqaure inch counts in this case. I have a preliminary layout and have a couple other options and the warmer components appear to be spread out enough. Is there a problem putting the output tranny within inches of the pre-amp tubes? How about the EF86 tube. Is this more microphonic than say a 12ax7??? I am installing a fan but this is all going in a fairly small 1-12" oak cab so I want to be sure of cooling... Any and all tips very appreciated... Steve K

9/12/1997 7:36 AM

Steve Keay

AC30 trany layout

Hi,, Could anyone with experience
laying out a DIY AC30 please give me
some advice/pitfalls to watch out for
in laying the tranys, choke, and tubes
out so I can avoid any unobvious
problems??? I know the power trany
gets pretty warm on these amps but
does it radiate EMF at all??? How
about the OT??? I have no room to
spare so every sqaure inch counts in
this case. I have a preliminary layout
and have a couple other options and
the warmer components appear to be
spread out enough. Is there a problem
putting the output tranny within inches
of the pre-amp tubes? How about the
EF86 tube. Is this more microphonic
than say a 12ax7??? I am installing a
fan but this is all going in a fairly
small 1-12" oak cab so I want to be
sure of cooling...
Any and all tips very appreciated...

Steve K

9/12/1997 9:57 AM
Bruce	Steve, An AC-30 clone is probably not a good choice for a DIY amp that has to be built in a small enclosure. But you might be OK with a fan in it to keep some air moving. It won't do the tubes that much good but it might help the transformers stay a bit cooler. Try and keep the power supply transforemer as far away from the preamp input and tube as possible. Keep "anything" that carries heavy current away as well. Twist those filament feeder wires together as tight as possible and use min of 18 gauge wire. Curve them up and away for the chassis like a small suspension bridge and keep audio lines away from them too. Dig up some thin shielded cable to run the high gain audio stages through to the next stage. From the input jack to the grid of the first preamp tube is a good candidate for the shielded cable. Align the transformers so that none of them have there respective parallel plates in the same plane. If you bought a good transformer it will be a shielded one with coppper shileding around the windings followed by the normal looking bell covers on each end. It should have VERY little radiation. The EF86 has been touted as being more microphonic then others. I'm not so sure. So what? Mount the tube socket on small tiny rubber 'O' rings. I use the smallest, tinyest, rubber grommets I can find under the tube socket flange and under the head of the screw. This traps the socket flanges in a rubber surround for isolation. Good luck Bruce

9/12/1997 9:57 AM

Bruce

Steve,
An AC-30 clone is probably not a good choice
for a DIY amp that has to be built in a
small enclosure.
But you might be OK with a fan in it to keep some
air moving.
It won't do the tubes that much good but it
might help the transformers stay a bit cooler.
Try and keep the power supply transforemer as
far away from the preamp input and tube as
possible. Keep "anything" that carries heavy
current away as well.
Twist those filament feeder wires together as
tight as possible and use min of 18 gauge wire.
Curve them up and away for the chassis like a
small suspension bridge and keep audio lines away from
them too.
Dig up some thin shielded cable to run the high
gain audio stages through to the next stage.
From the input jack to the grid of the
first preamp tube is a good candidate for the
shielded cable.
Align the transformers so that none of them have
there respective parallel plates in the
same plane.
If you bought a good transformer it will be a
shielded one with coppper shileding around the
windings followed by the normal looking bell
covers on each end. It should have VERY little
radiation.
The EF86 has been touted as being more
microphonic then others. I'm not so sure. So what?
Mount the tube socket on small tiny rubber 'O'
rings. I use the smallest, tinyest, rubber grommets
I can find under the tube socket flange and under
the head of the screw. This traps the socket
flanges in a rubber surround for isolation.

Good luck
Bruce

9/12/1997 10:00 AM
M.Romasco	Steve, I guess you dont want to do your layout like Vox did? If you want some info on the way my AC30/4 layout is, e-mail me w/ your fax# and maybe I can help. Matt.

9/12/1997 11:39 AM
Steve "double post" Keay	Thanks very much Bruce and Matt for your help with this. I have seen Boogie amps (and owned a couple) that was more compacted with components but also, they don't run in true class A either I've read, but it looks to be enough breathing room. I'll email you my FAX Matt if you could send me that layout, that would be great... Well damned if I didn't double post again...phew...what a day... Thanks again all for your unrelenting assistance with this... Steve K

9/12/1997 11:39 AM

Steve "double post" Keay

Thanks very much Bruce and Matt for
your help with this. I have seen
Boogie amps (and owned a couple)
that was more compacted with components
but also, they don't run in true class
A either I've read, but it looks to be
enough breathing room. I'll email you
my FAX Matt if you could send me that
layout, that would be great...
Well damned if I didn't double post
again...phew...what a day...
Thanks again all for your unrelenting
assistance with this...
Steve K

9/12/1997 1:57 PM
R.G.	The conventional wisdom is to orient the transformers and choke so that the axes are at right angles to each other - that is, one with the tongue of the core vertical, one with it horizontal, and one with it at right angles to the other two. Even with copper strapping (although that helps immensely) an E-I core transformer/choke will both radiate and pick up magnetic field through the gaps where the E's and I's meet. It's good to use an aluminum chassis, as a steel chassis can actually "conduct" magnetic field to sensitive spots. I'll echo the earlier caution on heat - the AC30 puts out a LOT of heat, so if you're in a tight chassis, count on using a fan with appripriate slow speed to keep it from igniting - don't laugh, some AC50's and AC 100's actually did ignite. Spectacular, I hear.

9/12/1997 1:57 PM

R.G.

The conventional wisdom is to orient the transformers and choke so that the axes are at right angles to each other - that is, one with the tongue of the core vertical, one with it horizontal, and one with it at right angles to the other two.

Even with copper strapping (although that helps immensely) an E-I core transformer/choke will both radiate and pick up magnetic field through the gaps where the E's and I's meet.

It's good to use an aluminum chassis, as a steel chassis can actually "conduct" magnetic field to sensitive spots.

I'll echo the earlier caution on heat - the AC30 puts out a LOT of heat, so if you're in a tight chassis, count on using a fan with appripriate slow speed to keep it from igniting - don't laugh, some AC50's and AC 100's actually did ignite. Spectacular, I hear.

9/12/1997 3:01 PM
Steve Keay	Thanks for the info RG... Unfortunatly the only chassis I found that was strong enough in my mind was the new Hammond steel chassis. Thats also the best fitting one for this cabinet I had. Guess I'll live and learn if it turns out to be a problem being steel. Not sure what you mean by a fan "with appropriate slow speed" but I am going to install a fan. I did see a Vox head go up one time in a puff of smoke on stage, live. Not a pretty sight. Nor was the other guitarists face... If my mind hasn't completely escaped me, it was a AC30 head. There are a few of those floating around I've seen. But boy did it sound good just before it went... Thanks again for you input... Steve K

9/12/1997 3:01 PM

Steve Keay

Thanks for the info RG...
Unfortunatly the only chassis I found that was
strong enough in my mind was the new Hammond
steel chassis. Thats also the best fitting
one for this cabinet I had. Guess I'll live
and learn if it turns out to be a problem
being steel. Not sure what you mean by a fan
"with appropriate slow speed" but I am going
to install a fan. I did see a Vox head go up
one time in a puff of smoke on stage, live.
Not a pretty sight. Nor was the other guitarists
face... If my mind hasn't completely escaped
me, it was a AC30 head. There are a few of
those floating around I've seen. But boy did
it sound good just before it went...
Thanks again for you input...
Steve K

9/13/1997 5:28 AM
M.Romasco	Steve, My AC30/4 is a rare head virsion, especially for 1960. I've never seen one like it before but someone had the right idea to keep the ef86 isolated from the speaker cab. The Vox chasis is made of three parts of aluminum (control panel, preamp tube sec./component bds., power amp sec.) mounted on a wooden base that slides into the cabnet. You might want to make your amp a head virsion, it will save your ef86 and the cost of speakers when you do your next project. Hey R.G., Can you give us more details on the appropriate slow speed fan thing. I keep the back cover of my amp off for more air, would like to add a fan. Do you have any reccomendations. Matt.

9/13/1997 5:28 AM

M.Romasco

Steve,
My AC30/4 is a rare head virsion, especially for 1960. I've never seen one like it before but someone had the right idea to keep the ef86 isolated from the speaker cab. The Vox chasis is made of three parts of aluminum (control panel, preamp tube sec./component bds., power amp sec.) mounted on a wooden base that slides into the cabnet. You might want to make your amp a head virsion, it will save your ef86 and the cost of speakers when you do your next project.

Hey R.G.,
Can you give us more details on the appropriate slow speed fan thing. I keep the back cover of my amp off for more air, would like to add a fan. Do you have any reccomendations.

Matt.

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