Show us your flea-watts amps!

[goldleaf]

I know that I have to do something to these amps to keep them from being
live chassis suicide machines, but for now I'm just trying to be careful. Joe

An isolation transformer like a Hammond 172b can be had fairly cheap used at a ham show or flea bay. You can connect 2 old tube transformers back to back (make sure the 2 secondaries are the save voltage and are at least 2 amps) and /or you can get a Shockshield Portable GFCI plug which retails for less than 20 bucks. http://www.amazon.com/TRC-90265-6-0...?ie=UTF8&qid=1380095751&sr=8-14&keywords=gfci

 

[joenicholson]

flea amps

Thanks for those ideas. I'm going to go to the surplus electronics store, and try to find something that I can use as an isolation transformer. Joe

 

[mhardy6647]

BTDT. Actually, you can use any two identical transformers (e.g.,a 120V primary/12V secondary) wired secondary to secondary, as long as they are transformers (not autoformers) and the VA capacity is high enough They don't have to be "old tube transformers" - modern "solid state" transformers from R/S or PartsExpress or your favorite surplus place are fine to make into an isolation device, as long as they're beefy enough.

 

[goldleaf]

They don't have to be "old tube transformers" - modern "solid state" transformers from R/S or PartsExpress or your favorite surplus place are fine to make into an isolation device, as long as they're beefy enough.

Good point. Mouser has inexpensive ones, less than 20 a piece for 60VA capacity. Around here old ones are a lot cheaper than that though at ham fests, and higher amps.

 

[opa1]

Decware ZKIT1/SE84C P2P Clone.

Mark

 

[joenicholson]

Very nice looking little amp. Functionality aside, beautifully assembled projects like yours, are an art form that can be enjoyed without even hearing it.
Thanks for the picture, Regards, Joe

 

[jdg123]

It has been a while

'Just finding this post after a long time away from AK. It was with the help of a very fine AK member (SET12) that I built my flea powered amp. I'm not sure it will even make 2W but oh what a lovely sound they (a mono block pair) make!

Yup, it is my first build ;-)

 

[TerrySmith]

Rh-7695

Here's my 2c, an SE amp using transformers and 7695 output tubes from a Zenith console. Basically a RH-84 circuit but with series strung filaments and direct line operated through an isolation xfmer.

The sound is a lot better than the stock circuit. I just threw it together on an old chassis but will rebuild it with better iron and chassis.

 

[wa2ise]

I'd rearrange the order of the heater string to place the 12AX7 in the middle. As the middle of this string, before the bridge rectifier, looks like a centertap on the isolation transformer. A centertap on a transformer secondary that feeds a bridge will have half the total B+ DC voltage. And thus the 12AX7 heater will have half the B+ voltage as measured from the negative terminal of the bridge. With minimal AC waveform, good for lower hum, and the heater being positive compared to the cathodes also is good for lower hum pickup. I'd add a small cap to the 12AX7 heater to the amp's ground (which would be the negative of the bridge) to add a little filtering as well.

 

[davidro]

Runnin a pair of 86dB @ 6 ohms with my 9W now...keep the pics coming pals!

 

[davidro]

'Just finding this post after a long time away from AK. It was with the help of a very fine AK member (SET12) that I built my flea powered amp. I'm not sure it will even make 2W but oh what a lovely sound they (a mono block pair) make!

Yup, it is my first build ;-)

wow :drool:

 

[sled108]

6LU8 Compactron Spud Amp...Maybe 7 W/CH...

 

[cubdog]

DAMN IT PEOPLE! Stop tempting me! You know I have no willpower.

cubdog

 

[Curtwheeler]

My little Magnavox

Here's my slightly modified and recapped Magnavox 8303. It sounds so sweet I fixed it up to take with me down south for the winter. I just wanted something small that sounds good. I can't play it to loud in a R.V. Park anyway.

 

[Curtwheeler]

Here's the back

 

[mjalazard]

Sam Kim's Platinum Heathkit AA 151 with a dynamic 7 WPC triode:

 

[fdrennen]

Heres my little Philco "suitcase phono amp" mods,,, It had a tube rectifier, and 35C5's ... I converted the PS to SS, with an isolation transformer, and 50C5 output tubes, and a center tapped 12AX7 to help lower heater hum,, (thanks wa2ise!!),,, I have a pair of new Sylvania 50C5's, and an Electro Harminix 12AX7, in it now,,,I also removed teh tone controls...
The OPT's have a separate feedback winding, and it's pushing a pair of 15" Magnavox console cabinets, and sounds pretty amazing to me...

Regards,
John

I'd like to try that with a suitcase amp they are becoming hard to find these days.

 

[sony6060]

Does this count? I injected audio at the volume control to hear the single-ended 47 tube mighty 1.5 watts. It sounded surprisingly clean. I am thinking about a 6C6-47 tube stereo version.

 

[knockbill]

I'd like to try that with a suitcase amp they are becoming hard to find these days.

Well worth the time, in my opinion, I rebuilt a Zenith phono amp also,,,

I just added a CL-90 to lower the heater V a little, but mainly, it allows the tubes to warm up more evenly....

Regards,
John

 

[litefootdan]

Gosh,
You guys sure do have some impressive stuff here. I've just got this to show, but it sounds good to me. It's a couple Decware ZKIT1's that have been Mono'd. Said to be around 6 watts a side.