I use this amplifier to listen to NPR classical music on headphones (Sennheiser PX100) with an old FM stereo tuner. The amplifier serves its purpose, though I'd research Headwize.com for other options if I could do it again. In situations where perfect fidelity isn't so critical as reliability, this amplifier is a good choice.
The good points:
Inexpensive Easy to assemble Reliable Powerful Input matched for line out, not headphone out.
The bad points: Noisy -- Inescapable hiss Limited frequency response -- At least that's my impression. Fussy volume controls
The kit uses garden variety opamps. These are designed for use in battery operated, lo-fi electronics, such as portable radios, definitely not hifi applications. The amplifier adds a lot of hiss, and trims the highs and lows off the signal which makes a cd sound a little like FM radio. Had Ramsey chosen to work with better sounding opAmps, this little kit could deliver outstanding fidelity, probably without upping the price too much. That disappoints me.
As I said before, I am using the unit with an FM tuner, which happens to be pretty noisy anyway. So the Ramsey's shortcomings aren't so apparent in this setup. Those shortcomings definitely limit how many different ways I can use the product though.
"Moms best friend"
2007-01-11
- Reviewed By Doit2it from Madison, TN United States
Bought this for my father. He's hard of hearing and was driving my mother crazy by turning the TV volume up all day long. Bought/built this to hook up to audio out on the TV and used a 25 foot cord to set him up with headphones. He used a cordless headset before this. He didn't like having to buy batteries for the headset continually. Yes, he's 75 years old, he got to complain about something. This way, no batteries. Now he's gotta find something else to complain about.
This is a very wide bandwidth amp and should be capable of driving just about anything you have.
What I cannot understand is the way they implemented the volume controls. Not only are they separate, which means you have to readjust the balance every time you adjust the volume, but they used linear (rather than audio taper) pots with the left on the right and the right on the left. I can see doing that if you are putting a quick prototype together out of spare parts, but if you can order parts or get to a good electronics store there is no need and if you are selling it as a commercial product there is no excuse.
I replaced their volume controls with a conductive plastic dual gang 10k audio taper for volume and a dual 5k linear taper in series on the signal side for fine balance adjust. They don't fit in the circuit board so the wiring inside isn't pretty, but it's much more convenient to use. I also bridged the switch for the sibilance filter with resistors to eliminate the ear splitting click the first time it is engaged. Anything around 3 mega ohm or above should work. That filter comes in very handy with my Beyerdynamics DT-770's which have enough high end definition to cause physical pain when listening to low quality streaming audio where the high end is all compression defects.
This kit provides quality components and clear detailed instructions. Anyone who can solder should be able to assemble it in under an hour. The result is a quality amplifier for a great price.
Like another reviewer, I am dismayed by the fact I have to remove two over-long screws, thus opening the amplifier case, to change the battery. As a result, I will rarely, if ever, run the amp on battery power. It is currently working great on a cheapo variable voltage "universal" wall-wart. I expect it will always run this way.
This amp connects a Bose Wave Radio / CD to Sony MDR-V6 pro headphones. My only complaint is that the amp volume must be run at or near minimum to prevent brain damage. The sound is clear, crisp, and big. No complaints at all on the function of this amp.
Buy this amp. The assembly is piece-of-cake easy with no surprises or tricky operations. Great instructions including the design theory for hobbyists. The amp produces great sound and has good usability as far as control function and placement. And the price can't be beat.
I use this amplifier with Grundig S350 radio(line output) and Sennheiser HD280 headphone. They form a great music system; it seems to me that all of the three devices have quite a flat response. Before you use it, you hvae to spend about an hour putting the components in the PCB and solding them. It took 20-30 hours to burn in. One thing I feel uncomfortable about is it is in lack of a battery compartment; if you want to install a 9v battery you have to unsrew two long screws and open the cover.
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"Serves a purpose, but don't expect hifi."
"Moms best friend"
"Nice, but needs a few improvements"