transformers not attached to chassis??

[joshdfrazier]

So, I have a 7x5 chassis that i used for tiny SE amp. I've slowly dismantled it over time, using it as a donor for other projects.. I have a PT and OT pulled from a PP EL84 hammond organ that I would like to use for a new build. Obviously the tiny enclosure is not large enough for the transformers, PI tube, preamp and power tubes.

I already have the combo amp built, and was thinking about just screwing the transformers into the amp, with the leads going into the enclosure and speaker. Sounds like a good idea in theory, but practice is usually a different story as i've come to learn with this stuff. is this a bad idea?

[Milkmansound]

keep in mind that there is very high DC voltage on the primary

some old amplifiers had the output transformers mounted directly onto the speaker - so it can be done. If its just an amp for you to use, and you are ok with the risk, you should be ok

[joshdfrazier]

it would be for my own personal use, and the transformers would be mounted on either side of the chassis to minimize the length and exposure of the leads. i have also seen many older amps mount the OT directly onto the speaker, but have never seen a PT that wasn't affixed to a chassis. i think grounding was my primary concern.

[Tillydog]

I would suggest putting the power transformer inside a metal box (doesn't have to be fancy) and making a good connection between the metal of the box and the main chassis. It's what I did with my little combo amp:


[IMG680]http://i255.photobucket.com/albums/hh14 ... c7ff81.jpg[/img]

That's 7 core cable going between the main chassis and the transformer box - there's a heavy core which I used to connect both lots of metalwork. The OT on the side of the main chassis has heat-shrinked & shrouded terminals, and you can't really reach it with the back on:

[IMG1134]http://i255.photobucket.com/albums/hh14 ... C_0242.jpg[/img]

12AX7 -> EF86 -> EL84... I think it's sweet, but then I'm (cathode) biased!

[IMG1134]http://i255.photobucket.com/albums/hh14 ... C_0240.jpg[/img]

[joshdfrazier]

LOL thats a dad joke if i ever heard one.

i was thinking of using this ax84 6v6 poweramp as the base for my poweramp. except i will be using el84, as that is what i have on hand. i have read that 6v6 and el84 are very similar and can be a direct replacement with an adapter, but i have also heard that this isn't the case. what is the official word on that? and how would the schematic need to be modified?

http://www.ax84.com/static/corepoweramp ... ematic.pdf

[Structo]

I would suggest putting the power transformer inside a metal box (doesn't have to be fancy) and making a good connection between the metal of the box and the main chassis. It's what I did with my little combo amp:


[IMG680]http://i255.photobucket.com/albums/hh14 ... c7ff81.jpg[/img]

That's 7 core cable going between the main chassis and the transformer box - there's a heavy core which I used to connect both lots of metalwork. The OT on the side of the main chassis has heat-shrinked & shrouded terminals, and you can't really reach it with the back on:

[IMG1134]http://i255.photobucket.com/albums/hh14 ... C_0242.jpg[/img]

12AX7 -> EF86 -> EL84... I think it's sweet, but then I'm (cathode) biased!

[IMG1134]http://i255.photobucket.com/albums/hh14 ... C_0240.jpg[/img]

Nice looking combo there Tilly!

[Structo]

@ joshdfrazier

Even though you plan on keeping the amp and not selling it, we should plan on the inevitable that when we either pass on or leave it to our kids, that it should be as safe as possible and follow industry standards such as UL and CE when possible.

We certainly don't want anybody to ever be harmed by one of our projects.

I would recommend that all safety precautions be followed to not only protect users but also to protect ourselves from a lawsuit.

Just my 2 cents.

[tribi9]

That cabinet is really awesome Tillydog.

[Tillydog]

Cheers dudes!

(Sorry for the derail! )

[surfsup]

Totally agree with this:

"Even though you plan on keeping the amp and not selling it, we should plan on the inevitable that when we either pass on or leave it to our kids, that it should be as safe as possible and follow industry standards such as UL and CE when possible. "

[Tillydog]

LOL thats a dad joke if i ever heard one.

i was thinking of using this ax84 6v6 poweramp as the base for my poweramp. except i will be using el84, as that is what i have on hand. i have read that 6v6 and el84 are very similar and can be a direct replacement with an adapter, but i have also heard that this isn't the case. what is the official word on that? and how would the schematic need to be modified?

http://www.ax84.com/static/corepoweramp ... ematic.pdf

Have my kids been talking to you ???

Without splitting hairs, the voltages in that schematic are too high for EL84s (so you would need a different power transformer, at least) - have you looked at some of the 18W variants for an EL84 schematic?

[Ken Moon]

I wish I had a better pic, but on this project I converted a solid-state Marshall Lead 12 into an 18watt Superlite, and didn't have room for a PT.

So I mounted an Antek toroid on the bottom of the cab, and used wires sheathed in black plastic corrugated tubing, with high-current Molex connectors to allow disassembly. Then I put an Antek round metal cover over the PT, and tucked in all the wiring behind the edges of the cab.

It worked out really well, even though the wires to/from the PT are long. The amp is easy to carry, and is dead silent.

[img768]http://i514.photobucket.com/albums/t346 ... ersion.jpg[/img]