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Author Topic: An $11 Stereo Amplifier - New!  (Read 7072 times)

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Offline raymonda

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Re: An $11 Stereo Amplifier - New!
« Reply #15 on: August 26, 2015, 09:05:53 AM »
Smokin'! :P

Nice touch with the volume knob!

I would be seriously concerned with how you have your AC wired. That is not UL compliant and certainly has potential for shorts and fires. Either add a IEC jack or just hard wire it.

Offline raymonda

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Re: An $11 Stereo Amplifier - New!
« Reply #16 on: August 26, 2015, 09:08:20 AM »
Well, I'd have to go dig the last one out of its burrow; too many flies buzzing in and around it now though. Its kind of stinky out there.
I do have the RatsPaw though; my DIY tonearm.


Nice job on the table. I would be interested in seeing some closer and better shots of you arm.

Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #17 on: August 26, 2015, 09:27:27 AM »
Smokin'! :P

Nice touch with the volume knob!

I would be seriously concerned with how you have your AC wired. That is not UL compliant and certainly has potential for shorts and fires. Either add a IEC jack or just hard wire it.

Its DC, not AC.
The input jacks are rated at far greater amperage than the output of the PSU.  18ga. hookup wire is suggested; i went with 16ga. The power supply is fused at the output.
I have the highest level of contempt for IEC; won't use it; but cannot avoid them.  I was considering Neutrik Speakon, which I've used on the TT above (due to my strong dislike of IEC).
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Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #18 on: August 26, 2015, 09:42:36 AM »
Overview:


The deck has a modern DC motor, with speed controller card, and hall sensors; dead locked to speed for a solid month of continual rotation. I also completely redesigned the driveline, to that of a single idler wheel (it had three to begin with).  This is a hot-rod of a deck.
There is a build thread overview, here, at audiohaven.org.  If you decide to join up over there, tell them that mfrench sent you (please and thanks. there is a new membership signup contest underway).

This is the c.weight end:


The c.weights pivot on an axle that is perpindicular to the arm wand.  They freely pivot. When they encounter a warp, they drop straight down, rather than having the weight firmly attached, and being made to carry that load thru an arc.  I spoke with Frank Schroeder about my concept, and he agreed. He suggested that the fixed counterweight makes the arm plow thru the warp, causing wear in the groove, whereas, the rotating c.weights tend to unload at the hop of the warp, then reload on the downslope, rather than to have to carry the load the the arc; comparing it to a steamer/high seas cutter plowing thru waves, without wavering (which is not necessarily good for record wear).
They also act as stabilizing outriggers.
The bead chain is to damp out the side-to-side rocking action that unipivots have.  You can see them quickly and quietly bring the arm back to still and stable. Its akin to a phase cancellation.
The wires are lashed to the arm wand with waxed dental floss.
The arm cost -$1.50, and is made from free garage junk,, fishing weights, copper plumbing pipe, and precision brass hobby tubing.

Unipivot cup:


Unipivot stanchion, and the RatTrap arm holder:

It allows for VTA adjustment:


Brass and soapstone articulating mount:


Head-mount:

Lots of room for adjustments.
« Last Edit: August 26, 2015, 10:14:56 AM by m0k3 »
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Offline raymonda

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Re: An $11 Stereo Amplifier - New!
« Reply #19 on: August 26, 2015, 11:13:20 AM »
Nicely done!

Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #20 on: August 26, 2015, 03:03:43 PM »
Thanks, Raymonda.
That has been a really nice arm; functions flawlessly, and tracks superbly.  I don't need anything like an arm lift, so that a non-starter.  I use that rock by the tonearm to steady my hand, to put the needle down. It picks up really easily with the little loop behind the cart.
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Offline Ben Turnbull

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Re: An $11 Stereo Amplifier - New!
« Reply #21 on: August 30, 2015, 03:24:46 AM »
Wow, I didn't know  they offered the Brilliant Pebbles in Texas Size!  ;D  Always like seeing what's coming out of your shop. 

Question, that little amp put out much heat?  If so, you must run with the hood up?
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Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #22 on: August 30, 2015, 11:18:46 AM »
I've not noticed any heat, at all, and thats been crucial this past week, as we've been cooking here in the Friendly Village of Fallbrook.
My Plinius AB SS amp runs warm, on average. So, this is proving to be the opposite, which is a giant bonus.

Hood up?....   
I did at first, but have not felt it necessary now that we're settling in with it, and becoming comfortable. Its not near anything flammable, and i have it on a piece of granite to isolate it from the carpet (in case of the worst case scenario). 
I have it running my big guns right now, and its a shockingly good little amp.
I think that my Plinius is a bit better at the bass register, at least thru my Soliloquy speakers (which have remarkable bass response).  But, that suggestion was when I had the little amp cranked to 10, and with a live recording, which might have had a bit of bass bloat to begin with.
Back to heat,....
I can put my fingers on the little heat sink, and not feel any heat. The power supply runs totally cool as well.  So this might become my summer amp.
Sarge wants me to build her a girls shed; she calls it a tearoom. I was thinking that this could be a neat amp for that sort of thing, as there is no power where she wants it to be built. So, a couple of marine batteries, and a solar panel, and this little thing,... you've got a system that can work in remote locations.

Magic Beans rocks,....
Nahh,.... its just a rock from the garden, that was flat on the top and bottom. Nothing as fancy as magic beans.
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Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #23 on: August 30, 2015, 01:35:26 PM »
thanks, Jon.
Is it that little heat sink that I should be feeling for heat?  In my know not much about this mind, I thought thats where I should bee feeling, but, really don't know.
Should it be to a point of feeling warm? If I felt it as being warm, I'd be concerned; if it felt hot, then I might not be using it.
I've run it for a fairly extended test last monday. Sarge goes to town for groceries on mondays, and I get to crank it up during those times.  I had some really hard rocking blues on last monday, and I didn't feel anything that I thought felt warm, over ambient room temp.
Beyond that, I listen at a low-moderate level;  at a level where a headbanger would want louder, and a chamber musician might not like it so loud.
There is also a heat sink on the power supply, that has a transistor mounted to it; nothing overt to report there either.

In all of my listening so far, it has played very nicely with my Bozak b302a Urbans.  They seem to be a fine match together.
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Offline kindms

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Re: An $11 Stereo Amplifier - New!
« Reply #24 on: December 10, 2015, 12:04:03 PM »
I picked up that Little Bear tube Pre-Amp off ebay today. I just happened to take a look to see what was around and they had an auction for one. It was only at $4.72 when i noticed it. I picked it up for $11.27 + shipping which was $16

looks like they have a few similar auctions if anyone is interested
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Offline Moke

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Re: An $11 Stereo Amplifier - New!
« Reply #25 on: December 11, 2015, 10:21:45 AM »
congrats! please let us know what you think.

To the $11 stereo amp,....
Still blowing me away.  I'm running it into a pair of Bozak B302a Urban speakers (wonderful late 50's hifi speakers that were refreshed with new Bozak drivers and x-over works, done by the factory, in '77/'78, per the original owner, who I bought them from).  They are not entirely efficient speakers; they prefer an amp with some backbone; I'd guess on the order of 88dB efficient.  This little inexpensive amp drives them wonderfully, and they make a wonderful pairing. They easily go louder than I'm comfortable with, with a lot of reserve power left to go if you like to head-bang. Bass?  Really deep bass, and everything else is there as well, very well balanced.
The B302a speakers and TPA cigar box amp are the stereo rig to the right, with the low-boy speakers:
« Last Edit: November 06, 2017, 10:39:14 AM by Moke »
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Offline Colin Liston

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Re: An $11 Stereo Amplifier - New!
« Reply #26 on: December 21, 2015, 01:22:52 AM »
Could this little amp be powered by a 12v sla?  I  am thinking thjs would make a great somewhat portable "boombox"
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Online Gutbucket

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Re: An $11 Stereo Amplifier - New!
« Reply #27 on: December 21, 2015, 08:39:18 AM »
Sure.  Years ago a buddy and I used one of these for a portable "car stereo" (R09 > amp > two small box speakers) powered via a cig-lighter power adapter in our stripped down autocross car.  Listen to the most interesting recent live pull on the drive to the airfield, then unplug the stereo and throw it into a box in the trailer = nothing in the car.  Easy peasy.

And if you were to use two 12V SLAs in series in your boom-blaster you'd achieve full power, Scotty.
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Offline Colin Liston

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Re: An $11 Stereo Amplifier - New!
« Reply #28 on: December 21, 2015, 11:52:30 AM »
Sure.  Years ago a buddy and I used one of these for a portable "car stereo" (R09 > amp > two small box speakers) powered via a cig-lighter power adapter in our stripped down autocross car.  Listen to the most interesting recent live pull on the drive to the airfield, then unplug the stereo and throw it into a box in the trailer = nothing in the car.  Easy peasy.

And if you were to use two 12V SLAs in series in your boom-blaster you'd achieve full power, Scotty.

That would finally be loud enough on the beach and piss off everyone around me. 
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Re: An $11 Stereo Amplifier - New!
« Reply #29 on: December 21, 2015, 02:04:22 PM »
Except you don't really need help doing that, do you?

C'mon, do it right with three of these and six speakers on a hexagonal pop-up canopy!!
Piss off the entire county.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations > virtual teleportation time-machine experience

 

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