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Old 15th August 2006, 07:17 AM   #1
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Join Date: Aug 2006
Default power amp kit recommendations

Hi, I am newbie here. I am searching for a small, easy to build, lost cost power amp for my pair of JVC speakers (they are from my out of ordered UX-2000 mini-hifi). The speaker's impedance: 4 ohms and power handling capacity: max 20W.

I have a Little Dot III headphone amp that I will use it as preamp.

Thanks very much
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Old 15th August 2006, 10:56 PM   #2
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Location: Monroe Township, NJ
While it's not a kit, an "El Cheapo" is within the grasp of a 1st time builder. From the outset, the "El Cheapo" project was an exercise in good performance at LOW cost.

Read the "El Cheapo" SAGA here.

"El Cheapo" will work with 12AQ5s, 6AQ5s, EL84s, 12V6s, or 6V6s as the O/P devices. A cathode resistor change is needed to use EL84s. The Triad brand power transformers called for are made in China. Getting equivalent O/P transformers in HK shouldn't be difficult. Just about any reasonable constant current sink (CCS) and negative supply will work in the 12AT7 "tails".

BTW, "El Cheapo" is an "integrated" amp. A preamp is not needed.
Eli D.
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Old 16th August 2006, 02:04 AM   #3
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Dynaco 70's are available once more.
"Make everything as simple as possible, but no simpler" Einstein
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Old 16th August 2006, 03:19 AM   #4
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what's your budget? the efficiency of the speakers?
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Old 16th August 2006, 07:29 AM   #5
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Thanks for replies,

Sorry that I really don't know the efficiency of the speakers. I even can't find it on web. What I know is that the speakers came with JVC mini-hifi UX-2000, with 4ohms impedience and power handling capacity max 20W (as stated at the back of the speakers).

My budget is US$120 or less. Below $80 will be the best. I know this budget is too low for good stuff, but that's what I can afford (as a student )

Actually, my headphone amp also have speaker output. However, I need to turn the volume knob to nearly max. in order to have enough volume. So I am thinking if I should install a power amp.
With my low bugdet, should I consider adding a DAC, or changing the speakers, instead of adding a power amp, in order to achieve best improvement?

Thanks very much.
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Old 16th August 2006, 08:18 PM   #6
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Location: Berlin
to be honest, unless you can find some vintage amp used, $80 won't get you very far for a tube amp. you're better off buying a Class T power amp, or DIY-ing some type of chipamp .
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Old 16th August 2006, 09:19 PM   #7
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Yes, for $80 you almost need to find a cheap donor amp (we have quite a few under $100 amps here), but do keep in mind that the target ceiling for the El Cheapo is $100 and that was reached with all new parts.

Our Scott based El Cheapo cost less than that, but only because we got the Scott for cost of shipping (something like $40) and then were able to recoup most of that selling the knobs & faceplate. That saving was countered by our penchant for using Solen film caps instead of elcos in the PS.

community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
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Old 16th August 2006, 09:30 PM   #8
scott_m is offline scott_m  United States
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Location: Portland, OR
I can vouch for the el-cheapo relative ease of construction - and I'm very satisified with the high quality of sound it produces. I think the original goal was, however, to keep the iron costs under 100 dollars. The initial outlay of tubes, sockets, caps, resistors, ect...provided by Jim was another 100 - 125 depending on which pieces you opted for.

I think Dave's idea of scavenging a doner amplifier for transformers and possible chassis is a good one - provided you have access to these kind of materials.

The idea of building a chip amp was good as well. Charlize (diyparadise (dot) come) has a very 'organic' tube like sound and the amp module can be ordered for sub 100 dollars.

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Old 16th August 2006, 09:37 PM   #9
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Location: Lisboa
Why not mix both worlds and make a hybrid? Tube voltage amplifier stage feeding to a MOSFET power follower.
"There's something organic about a happy cloud of electrons" - Neutron Bob
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Old 17th August 2006, 12:06 AM   #10
Sherman is offline Sherman  United States
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Location: Chicago area
Originally posted by Simpleton
Why not mix both worlds and make a hybrid? Tube voltage amplifier stage feeding to a MOSFET power follower.
I second this idea. A pure tube amp would be nice but for the budget it would be hard to beat something like an LM3886 gainclone with a tube front end.

You wouldn't necessarily need any gain from the front end, just a simple cathode follower would work. No it isn't a SET and the sound won't be confused with a Loftin-White 2A3 but hey, it is a start. (Plus it is on my mind right now since I had a bunch of old 3875 chips in the box and slapped together a couple hardwired gainclones and just yesterday put a 6922 cathode follower front end on a pair of them. ).
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