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Building New Housing for part of an Amp Head
Old 6th January 2015
  #1
Gear Head
 

Building New Housing for part of an Amp Head

My SUNN O))) Alpha 115 combo amp has a speaker that is much too large and loud for my current purposes, so I disconnected the head from the speaker to see how I could temporarily and safely keep the two separated. I found that the underbelly of the head (where it met the cab below it) is unprotected - all of the innards are exposed when the amp head is taken off.

I am thinking about building a wooden side for this underbelly to protect the innards, and I wanted to check if anyone had any tips, tricks, or advice for a project like this. I imagine simply covering the open side will suffice, but I have no experience doing this. I want to make sure that later I will be able to disconnect this newly made side so I can reattach the cab that came with it.
Old 7th January 2015
  #2

I've been thinking about this a lot lately (got a Tweed Deluxe chassis kit on the way...)

If you have tubes and caps that extend below the bottom, you need to create space for them (especially if they get hot). Ventilation may be required too.

In the end, building a new box that's the same except for the height is probably the best approach. Attach the chassis to it the same way as the stock box. Make sure to allow for ventilation if needed.




-tINY

Old 7th January 2015
  #3
Gear Head
 

It's a solid state amp, so there are no tubes to worry about. The original design made no effort to allow for ventilation. Is that also a design characteristic required mainly for tube amps?

Thanks for the insight.
Old 7th January 2015
  #4
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Jeff Scott's Avatar
 

Quote:
Originally Posted by hfdz0 View Post
It's a solid state amp, so there are no tubes to worry about. The original design made no effort to allow for ventilation. Is that also a design characteristic required mainly for tube amps?

Thanks for the insight.
Even SS amps require proper ventilation; that SUNN did not do so does not mean you shouldn't, either.

I had a SWR Workingman's 12 (the original style) years ago that I took the amp out of the combo case and built a head case for. The heatsink fins extend out from the back of the chassis and was completely surrounded by carpeted casework! Only the back edges of the heatsinks were free of any obstruction, and this got very hot after being on and played through for a short while.

I made a really nice case out of oak, with the front slanted to match the angle of the front panel, and I made cutouts above and below the heatsink to allow for proper convection cooling, something SWR did not do.

So long as you are going to the effort to make a head case for your SUNN do it right and provide for ventilation of the output transistors/heatsink area.
Old 8th January 2015
  #5
Gear Head
 

Thanks for the info Jeff, you raise a good point. Unfortunately I don't have the cash or access to high quality wood, but since the case is only temporary and won't be gigged with I think it will be ok to use what I have around.

One additional thing I didn't mention -
I plan to use the amp only with headphones after the job is done, and would prefer not to attach a new speaker. Are there special caps or stoppers I should put on the ends of the jacks where the cab generally would be connected to the head?
Old 8th January 2015
  #6

Just don't plug anything into them. A solid-state amp will be happy with no load all day long.

Now, if your amp is a weird one with a current-feedback - you could have issues with no load.

Check the resistance from the speaker outputs to the chassis. If one of them is not less than 1 ohm, you may have to look at the schematic.




-tINY

Old 8th January 2015
  #7
Gear Head
 

A nice little surprise today - according to the official sunn amps page (the company was bought out by fender a while back if you didn't already know) it costs $5 to get a schematic and snail mail is the only listed means of sending it to you. I contacted fender customer service to check and they sent me the proper manual quickly and for free!

I will check the speaker outputs when I get a chance.
Old 8th January 2015
  #8
Quote:
Originally Posted by hfdz0 View Post
A nice little surprise today - according to the official sunn amps page (the company was bought out by fender a while back if you didn't already know) it costs $5 to get a schematic and snail mail is the only listed means of sending it to you. I contacted fender customer service to check and they sent me the proper manual quickly and for free!

http://oi59.tinypic.com/ziuesz.jpg

I will check the speaker outputs when I get a chance.
The pic you linked to is a flow chart, not a schematic. Also, the site tries to force a software download on you - it shows a popup that says your media player isn't showing the content correctly and to "upgrade", then when you click on the "X" to try to close the popup it tries to start the download automatically instead of simply closing. Not nice and highly suspicious behavior. I'd avoid that site if I were you, that's a common technique used for planting spyware on your computer.
Old 8th January 2015
  #9

My corporate firewall had big issues with that pop-up too. I didn't get to see what it said, though.

Something wrong with posting your scan directly to GearSlutz?



-tINY

Old 9th January 2015
  #10
Gear Head
 

I apologize for the evil link. I didn't get any pop ups or warnings when I went there, but I should have known that a popular and free image hosting site like that might host spyware. That's what I get for being lazy. I'm used to simply putting the link in {img}{/img}'s but i am too new for that apparently.

Image is attached below.

Please forgive my lack of experience with schematics and flow charts - Thanks John Eppstein, for correcting me there. I asked fender if they had a schematic, still waiting on that.
Attached Thumbnails
Building New Housing for part of an Amp Head-sunn-alpha-series-schematic.png  
Old 10th January 2015
  #11
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Jeff Scott's Avatar
 

Just a guess, but this schematic is probably pretty similar, outside of some component values and the reverb circuit:

http://music-electronics-forum.com/a...pha-12revb.gif
Old 10th January 2015
  #12
Gear Head
 

Thanks for that Jeff Scott. Fender got back to me with the schematics for the alpha series. There are a few different preamps in the pdf the Fender guy sent me and I'm not sure how to figure out which one I have. The amp head is open and I can see all the innards but I don't have experience translating what I see in the real world to a schematics diagram. I'll have to to do some research there. I forgot that there is actually a reverb circuit in my amp, and a 1/4'' jack for a reverb pedal in the back of the head that i have never used. Not sure if I need the foot pedal made specifically for the amp.

Right now the attached is my best guess
Attached Thumbnails
Building New Housing for part of an Amp Head-alpha-series-schematic.jpg  
Old 11th January 2015
  #13
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Jeff Scott's Avatar
 

Quote:
Originally Posted by hfdz0 View Post
Thanks for the info Jeff, you raise a good point. Unfortunately I don't have the cash or access to high quality wood
I used oak as that is what was around at the time, the guy with the wood shop had a very large stash of it that he acquired decades before so it was cheap (free) for me!
Old 12th January 2015
  #14
Gear Head
 

Lucky find Jeff! All I have is some dried out plywood and 2x4-esque pieces left out in a barn where it has been between 0 and 25 degrees farenheit (about -18 to -4 C) for the past week. I was able to cut the pieces without any cracking or splitting, but now I am letting the pieces sit by a humidifier before I put screws in them.

I am planning on building a C-shaped enclosure around the innards of the amp that can screw in from the top of the head (there are already screw holes in the amp head's top cover at just the right spots for this). At one end of the C-shape I was thinking of installing a hinge and sticking velcro to the other end of the C so I can open it up whenever I need to. Now I'm thinking that this setup is a little too temporary and should in fact be screwed in at each end of the C-shape to better protect the amp's innards. If velcro is the only thing keeping the housing from coming apart it might not stay closed.

I decided I wanted the option of attaching a small speaker I have lying around, but I am having trouble getting the wires from the speaker to the head to stay connected. I don't have the same connectors that its previous speaker wires had to stay stable, so now all I have is bare wires poking into the jacks on the amp head.

Does any one have advice for keeping these wires from the speaker stay in place in the amp head?
Old 12th January 2015
  #15
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Can you post photos of the connectors or give us a more detailed description? Do they go to pins or a connector header on the PCB of the amp?
Old 12th January 2015
  #16
Gear Head
 

It's not like any speaker connection I have seen before - perhaps the pins are beneath what I am seeing.

To give a more accurate description - i said jacks earlier but these "jacks" are really just small steel barrel-like orifices sticking out of the circuit board. There is nothing to secure the wires plugged into them with unless the wires come with a small, open steel extension on them that fit snuggly around the jacks/barrels. The opening on the barrels are no more than 2-3 mm wide and 1/3 of an inch long, so it takes a good deal of focus and willpower to get the wires in there in the first place. Once they are in they don't stay in if the amp is moved, no matter how slightly.

Let me know if this makes sense.
Old 12th January 2015
  #17
Old 12th January 2015
  #18
Gear Head
 

I can't load the first link for some reason, and they look a lot smaller than the terminals on the second link.

They kind of look like the second pin in the upper left most row in this, although a 1/4 inch longer:

https://www.mill-max.com/assets/new_...e-PCB-Pins.jpg
Old 12th January 2015
  #19
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Jeff Scott's Avatar
 

Split-fork terminals? Like these?

http://swartamps.com/tech/bias_mod/bias_far_full.jpg

The wire should go through the terminal or wrapped around it, then soldered. These kinds of terminals are common on vintage style tube amps. You probably will not find a mating connector that plugs into it. Doesn't mean you can't make some mods to the amp to accommodate the speaker leads, though.
Old 12th January 2015
  #20
Gear Head
 

Can't see what you're talking about in that pic. I see that the ground appears to be circled, but I can't find a terminal that looks like mine.

Looked up split-fork terminals and I see what you are saying - I actually was thinking the fork part is what was connected to the circuit board, and all I saw was the tube-ish structure sticking out of the board at the opposite end. Apparently this is the opposite?

Anyways, i see small steel tubes sticking out of the inside of my amp, as i said "no more than 2-3 mm wide and 1/3 of an inch long" 2 of my posts ago. I know that they work if i simply stick the wires in there because i tested it and the speaker played the audio signal the amp received from my guitar.


I still want to be able to take the speaker and amp apart with ease, as I will not be able to store and play it in the same area.

Thanks for your patience
Old 13th January 2015
  #21
Can you post a photo?

I'm thinking that either these are solder type terminals that we not soldered or that they're part of some kind of connector that has been broken - I can't see Sunn just sticking unsecured speaker wires loose into contacts. Some contacts have a little spring inside the holds the wire but your description doesn't really sound like any of those I've seen.

BTW, they're probably not steel, much more likely tinned brass.
Old 13th January 2015
  #22
Gear Head
 

Below are pics of the wires from the original cab with the "extensions" I was trying to describe above. Also, 2 pics of the barrel-like orifices in the amp - a birds eye view and another view so you can see the lengths of them.
Attached Thumbnails
Building New Housing for part of an Amp Head-20150112_211748.jpg   Building New Housing for part of an Amp Head-20150112_212209.jpg   Building New Housing for part of an Amp Head-20150112_211824.jpg  
Old 13th January 2015
  #23
Quote:
Originally Posted by hfdz0 View Post
Below are pics of the wires from the original cab with the "extensions" I was trying to describe above. Also, 2 pics of the barrel-like orifices in the amp - a birds eye view and another view so you can see the lengths of them.
Those are a type of push-on connector, similar to ones used in some automotive applications. The ones on the board are males, the wires have the female sockets. If they're loose (and they do get loose if taken apart frequently) you need to tighten the females by squeezing them gently with a pair of needle nose pliers to squash them just a teensie-eensie amount. Do Not oversquash them, be careful. Squeeze them just enough to make them click into place on the male posts, rather than fitting loosely.
Old 13th January 2015
  #24
Gear Head
 

If you read above, I'm not trying to connect those wires (the ones pictured) to the connector, but instead I have a different cab that I would like to temporarily fix the head to. This different cab has standard wires without the male posts, they are straight sleeved wires stripped at the ends. Any ideas on how to connect these standard wires to the female connectors stably and safely? I only attached the picture of them to show how the connector and wires went together in the first place.

Additionally, is it safe to connect wires that extend from the female port i showed you on the amp to a capped off end when not in use? It's going to be difficult and depreciating to attach the wires from the speakers ever time I want to use them, as I am going to have to detach them every time I use and then later, store them. As a result, I would rather simply keep wires plugged into the female ports extending out from the ports so I can twist them together with the speaker wires when needed.
Old 13th January 2015
  #25
Quote:
Originally Posted by hfdz0 View Post
If you read above, I'm not trying to connect those wires (the ones pictured) to the connector, but instead I have a different cab that I would like to temporarily fix the head to. This different cab has standard wires without the male posts, they are straight sleeved wires stripped at the ends. Any ideas on how to connect these standard wires to the female connectors stably and safely? I only attached the picture of them to show how the connector and wires went together in the first place.

Additionally, is it safe to connect wires that extend from the female port i showed you on the amp to a capped off end when not in use? It's going to be difficult and depreciating to attach the wires from the speakers ever time I want to use them, as I am going to have to detach them every time I use and then later, store them. As a result, I would rather simply keep wires plugged into the female ports extending out from the ports so I can twist them together with the speaker wires when needed.
The connectors on the wires are female. The ones on the PC board are male. You need to get the appropriate female crimp on connectors to attach to your new wires. They're not hard to find, they're actually common as dirt. Check sites like Digi-Key, Jameco, Allied, Newark, and plenty of other electronic parts distributors. You'll need the appropriate female connectors (pennies) and a hand crimper (around $20, give or take.)

Or clip the old wires with the connectors on them at an appropriate length and solder them to a suitable 1/4" jack.

Really, this isn't rocket science although you will need to learn to solder or get a friend to do it for you.

Or if you can't deal with it, take it to a tech.

Last edited by John Eppstein; 13th January 2015 at 10:20 AM..
Old 13th January 2015
  #26
Gear Head
 

Thank you for the very intelligible info John. At my level I really need that! I am unfamiliar with crimping, but I found some good youtube vids on it. It will take me some practice, but i am sure it is a worthwhile skill to master if I am going to continue working on / with this guitar amp in case of repairs, modifications, etc.
Old 14th January 2015
  #27
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Jeff Scott's Avatar
 

John's suggestion to add a 1/4" jack to the amp out is probably your best choice as this way you can very easily go from one cabinet to the other. Find a place on the chassis to drill a hole to mount the jack permanently, then add a 1/4' phone plug to the existing combo 's speaker (whether using the existing wires or new).
Old 14th January 2015
  #28
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Quote:
Originally Posted by John Eppstein View Post
Those are a type of push-on connector, similar to ones used in some automotive applications.
Oh, hell, those are plain old Molex connectors, aren't they? They're pretty common.
Old 14th January 2015
  #29
Gear Head
 

Wasn’t familiar with Molex connectors, but if google pics is reliable I can tell that is not what i have. See pics above (post #22 ).

Found some useable much on connectors at the hardware store. The manager called them bullets - and they do look somewhat like small empty casings. The ones they gave me were a little large, but after I trimmed them down and compacted the end, it fit well. Music sounds good coming out of the speaker.

A question that remains - Is it safe to connect wires that extend from the connectors I bought, now on the male port on the Board in the amp, to a capped off end when not in use? I am going to have to detach them every time I use and then later, store them and it's going to be difficult and depreciating to attach the wires from the speakers ever time I want to use them. As a result, I would rather simply keep wires plugged into the female ports extending out from the ports so I can twist them together with the speaker’s wires when needed. Just not sure if this is 100% "healthy" for the amp, or if there is something about this that might be damaging that I don't know about.
Old 14th January 2015
  #30
Quote:
Originally Posted by lame pseudonym View Post
Oh, hell, those are plain old Molex connectors, aren't they? They're pretty common.
Well, Molex usually refers to the ones encased in a Nylon shell (and "Molex" is a brand name that also encompasses pin connectors and a couple other types), but essentially, you're close. There are minor differences between a Molex and this type of barrel connector. (Molexes aren't ribbed the way these are and also usually have a spring contact split out from the side of the female.)
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