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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Wed May 09, 2012 10:32 pm Post subject: |
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Yeah you can pretty much buy anything out of China now if you look hard enough. SOme of it is actually pretty good quality and for the price you can't beat it.
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Walter
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed May 09, 2012 10:55 pm Post subject: |
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I had a buddy from Hong Kong bring over a 200 watt per channel integrated amp kit, that must have been 1980. Without heat sinks, case or power transformer, I think they were $50 CDN each? We both built them, mine didn't work, his did. I didn't have the skills to troubleshoot it, and I think my parents threw it out when I moved out.
I've love to get a kit like that again. I'm sure it was a transistor in backwards or something, but I'd build one of those in a heartbeat. The 'unbuilt Heathkits' on eBay are dwindling down...
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Wed May 09, 2012 11:18 pm Post subject: |
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I haven't seen any kits available lately, mind you I haven't really looked. You looking to build a 200W/ch amp?
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Walter
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed May 09, 2012 11:25 pm Post subject: |
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Oh, if I could find one for under $100, I'd just do it for the fun of building it. Iv'e never built a high power amp before.
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Wed May 09, 2012 11:29 pm Post subject: |
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JUst go to ebay and do a search for power amp kits, I just did and there are lots of pages of available kits. Some are you stuff the board others come stuffed.
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Walter
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Thu May 10, 2012 1:00 am Post subject: |
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There you go and it'll cost you a whole 50 bucks. It would be nice to see a schematic and what kind of outputs it's using. BUt for $50 what hell.
Bass treble midrange controls, what are those? Real audiophiles don't use those, straight through it the only way, no phase shfting controls allowed.
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Walter
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Boilermaker
Joined: 21 May 2006
Posts: 527
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| Posted: Thu May 10, 2012 1:56 pm Post subject: |
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Damn - Can't believe they can sell that for that price. Incredibly cheap, but I would certainly use bigger heat sinks than they show.
I built an excellent high power amp years ago for very little money all based on AA projects. I had a GAS Ampzilla that I bought for $10 that someone had blown up, so I stripped it down and just used it for a chassis and power transformer.
I used the original Pass A40 board that I got from OCSL and instead of using it as a 40 watt class A as it was intended, I run the voltage up and dropped the bias current so that it was about 250 watts (8 ohm) class AB. Then I used another AA board (can't remember the author) that was a very high current/ high voltage regulator which I used to fully regulate the amp at about 200 watts. If you remember, the Ampzilla had fan fed heat sink chimney and I just attached the output mosfets that the regulator used to the chimney. I removed the VU meters and used the space to add additional fans as the regulator sucks up power and produces lots of heat.
It was really ugly, but I used it for many years and loved it until the original PS bridge rectifier gave up. Still have it sitting on a shelf gathering dust as I replaced it with a Bryston I got for free. Need to get off my butt and fix it. That regulator was awesome!
Bob
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Thu May 10, 2012 10:09 pm Post subject: |
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Were those regs designed by Borbly?
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Walter
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Boilermaker
Joined: 21 May 2006
Posts: 527
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| Posted: Fri May 11, 2012 10:49 am Post subject: |
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NO, and I can't remember the author. They were really nice as you could adjust the output voltage with a pot and just needed a 5 or 10 volt spread and used several mosfets to provide output voltage. So simple that I wondered why more amp companies don't do it? And it was reliable!
Bob
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Fri May 11, 2012 12:59 pm Post subject: |
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Hmmm, don't remember those.
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Walter
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Boilermaker
Joined: 21 May 2006
Posts: 527
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| Posted: Fri May 11, 2012 3:33 pm Post subject: |
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I'll see if I kept any hard copies of the article that I built them from. I do remember getting the boards from OCSL. They were long and skinny and the outputs could easily be mount to a heats ink. I will have access to a camera in a couple of weeks and can take a picture if you are interested.
Bob
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sun May 13, 2012 12:44 pm Post subject: |
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Uh, am I the only one who noticed the failed mounting of the output transistors on the picture? (assuming they are the same type, and why not?) the ones mounted on the layer side should be reversely connected.
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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Mon May 14, 2012 1:17 pm Post subject: |
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Who's to say they are sharing the same pads? Can't really tell.
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Walter
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Boilermaker
Joined: 21 May 2006
Posts: 527
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| Posted: Wed Jun 13, 2012 1:02 pm Post subject: |
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| Quote: | | Were those regs designed by Borbly? |
Walter,
I finally found some info on them as I pulled out the old amp and took the top cover off to see them. I was going to snap some pics, but my camera is giving an error statement, so I'll post them later.
The designer was Ryan and in his article they were used to regulate the big flagship Adcom amp of the time, but it could be used on any amp. The boards are about 2" X 7" and the big Toshiba mosfets hang out the side to be bolted to a heatsink. The article was in the 4th issue, 1989 which is still available in reprint for $20 from audioamateur.com .
They worked very reliably for many years, but the full wave bridge rectifier on the amp went out about the same time I received a pair of Bryston's for free, so I never bothered replacing the rectifier. If I had any sense, I would remove the boards and install them on one of the Bryston's! Got a few projects to do first.
Bob
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Boilermaker
Joined: 21 May 2006
Posts: 527
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| Posted: Sun Jun 24, 2012 4:43 pm Post subject: |
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Walter - I finally had an opportunity to get to that old amp with the Ryan regulators. You can see both of them as I used some extruded aluminum to mount the power mosfets to and then to the "chimney" There is a little pot on each one that you use to adjust the output voltage. Still works fine, and doesn't take up too much space.
Bob
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WTS
Joined: 08 Mar 2006
Posts: 1276
Location: Calgary
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| Posted: Mon Jun 25, 2012 1:36 pm Post subject: |
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Cool, still working after all those years.
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Walter
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