Antique Electronics Supply K-502 Stereo Amplifier

Jstas

That's it and here is a link to the specs:

K-502 Specs

Well, I bought this about 2 weeks ago when someone posted a link to it in this forum. I slammed it together tonight in about an hour and a half and spent 4 hours playing with it! I said I would let everyone know how it went so that's what I'm doing. I have pictures and I will post them later.

As far as the kit goes, it arrived very quickly, about 3 days FedEx ground. The cost was only 3 or 4 dollars so the initial investment was less that 150 bucks. For that price, this thing sounds spectacular! I'm sure I could beat it but for 150 bucks and an hour and a half on a Monday night, I can't beat it. The kit was extremely simple to put together but could be slightly challenging to a beginner. The directions are very clearly written and they go into tremendous detail. Soldering skill is required and so is the ability to understand a basic electrical circuit.

The only problem I have with it is the potetiometer for the volume control. It seems bad because it is putting out a 70 Hz cycle and when I touch it, it gets louder and plays a 210 Hz cycle in addition to the 70 Hz cycle. There is no AC power noise and no 40 or 60 Hz cycles from grounds. I think I put it together pretty solidly. I figure 5 bucks at Radio Shack for a new potentiometer and I'm set!

As far as recommendations, I whole heartedly recommend this unit! It's perfect for an office or a kid's bedroom or a garage. It will accept anything that allows you to run a pair of RCA cables to it. I have been running Walkmans and Discmans through it with a stereo mini plug to RCA adapter.

I haven't been able to turn it up to see how well it performs because everyone is asleep but on a scale of 1-10, 10 being loudest an extremely modest setting of a 1.5 plays loud enough to hear it without a problem from 40 feet away. I will definitly crank it tomorrow and see what it can do!

My plans are to use it in a lab at work where the fan noise tends to get annoying. I'm going to build a switch box that will allow me to connect more than 1 piece of equipment at a time and be able to switch between sources. That should cost about 20 bucks in parts at Radio Shack. I'm still below 170 dollars even with the new potentiometer. I think I'm going to get a set of RTi38's for it eventually but right now, I'm going to see what kinda speakers I can scrounge or maybe build cabinets with a set of old car speakers. With the RTi38's, it will be about 550 bucks. For 550 bucks, you could probably get an executive office shelf system but of those I have heard, none sound like this.

Overall I am extremely pleased! This came out much better than I ever thought it would have! This is not only an excellent little amp but it's a great tool for learning. It gives a basic understanding of how a tube amplifier works and exercises basic soldering skills. Advanced solderers and/or eectricians should be able to assemble this kit in less than an hour. It would be an excellent science fair project for a kid or just a good thing for a father and son or a father and daughter to do as a project. Totally worth the money and time.

Ceruleance

What about a mother and daughter or mother and son, huh? Mr. Politically correct?

only kidding. Seriously, though, has there ever been a woman on this forum?

Alright, didn't mean to change the subject right off the bat. Where did you get the parts for your kit? partsexpress? Does it leave any room for upgrades and things like that? It sounds like something I'd want to do over the summer or spring break, I would want to tinker with all the pieces just to see what makes a difference in the sound.

Jstas

It's a kit that comes with all the parts you need for the amplifier. There are some options you can play with yourself but you need to get the parts you would need to do it yourself, they don't come with the kit. However, it is just a pre-amp and an amp in one package. There isn't much to change. I suppose you could rewire it to get more power but your would have to change transformers and tubes and such too.

gidrah

I posted the link. I'm glad you like it. Have you cranked it up yet?

Jstas

Yeah, I was messing around with it today. I think I ran through half my CD collection! For the money, it sounds spectacular!

I also played around with outputs. Apparently, the line out on the Sony Discman I have leaves something to be desired in the low frequencies. I plugged it into the headphone jack, turned up the Mega Bass and set the volume about half-way up. It made a tremendous improvement!

The highs don't sparkle as well as some of the newer stuff but otherwise, it absolutly sings! I can hear the limits of the frequency range but it covers about 98% of what a modern solid state unit can do.

I had gotten away from wiring and circuits and stuff because I haven't had to use it. I used to build my own speed controls and such for my radio controlled cars. Building this kit reminded me how easy it is to build. It's all the more sweeter when you know that you built that piece of equipment!

Thanks for the recommendation, I'm glad I got it. Now I'm just praying I don't get laid off. If I survive the lay-offs, I'll be getting a set of Klipsch 17's from Mr. Grand. He said they need to be refinished but I have no problem with that, should be fun! That will give me a nice stereo for about 180 bucks for the lab at work.

HBombToo

Originally posted by Jstas
Now I'm just praying I don't get laid off. If I survive the lay-offs,

You and me both brother! I work in telecom and its been a tough year with another in progress.

KNOCK ON WOOD AS I SUBMIT!
HBomb

Tour2ma

Very cool Jstas. I'd be curious as to what kind of current output it can manage to produce for transients. If you have the measurement equipment in your lab, perhaps you could run a strip chart during a lunch time concert and let us know.

Also had to chuckle at its THD spec "@ 1w <1%"... and we fret over values 1/50th of that at full rated outputs.

Jstas

It's not that kind of lab. It's full of Sun systems and PC's with networking gear out the wazoo and racks and racks of drives of all kinds with a few repair stations thrown here and there. Its a lab my department has for testing and staging new and repaired equipment, maintaining the equipment and preparing equipment for shipment to remote sites. When we deliver a system to our customers, the engineers go out for the install and to perform testing, repair and maintenance. My group takes care of all the equipment the engineers use to do thier work at the remote sites. So there is no audio testing equipment in the lab at all. Since there is no recording device of any kind allowed in the area, if we want good tunes, I have to find alternate solutions that do not involve any CD-R drives, microphones or cassette recorders like you find on most boombox/shelf systems. I also don't want to put an expensive piece of audio equipment there because it will grow legs. This amp looks like hell because it is unfinished so nobody will bother with it. If I grab the set of Klipsch 17's from Mr. Grand, I'll pull the emblems off and nobody but me will know what the hell they are. Stealth is key to preserving the position of your poessesions remaining your possesions.

I used to have a decibel meter but I dropped it a week or so ago in the driveway and it's broken pretty good. Since I am in danger of losing my job, I can't really afford to get a new one right now.

The distortion rating really doesn't bother me. It's a tube amp, they typically have high distortion rates. It's not even the amplification or signal source that is the issue. It's the hum of transformers and tubes that causes the higher ratings. If you run a clean signal into it, you won't have any problems with it. I have run the amp at full volume and couldn't hear any distortion whatsoever. I have a keen ear for it too. It just plays loudly and cleanly.

Tour2ma

Good plan... ugly + no-name = secure...

Just thought you might be able to chart record either current draw or alternately, simultaneous voltage drop and impedance. Just curiosity on my part.

Will keep an good thought for you job-wise...

Jstas

I wouldn't need fancy test equipment for that though. Just a multi-meter. I suppose I could get some info for it. Depends on if I have time. When I start listening to it though, I end up playing with it for hours.