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Forceaudio
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« Reply #15 on: March 18, 2008, 12:45:15 am » |
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MikeS
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« Reply #16 on: March 20, 2008, 01:23:06 am » |
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Amost done....I'm a little farther than the pic. I have the RCA grounds to chassis worked in, and figuring out how to layout the input R's.
I should finish it this weekend.
I thought I might have a score for a Yamaha MX-800 power amp to run my subwoofers with. Listed on Craigslist in Readan, WA.
I've emailed the twit twice, (no phone #) and no replies.....
This is the second Craigslist listing for a high power Yamaha power amp where the seller doesn't reply or say shit. Some loser in the Valley pulled the same thing.
Here's a novel idea.....If it's sold, pull the listing. If it's sold, email and inform me!
Email and tell me to fuck off....Christ, at least reply!
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todd.brust
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« Reply #17 on: March 20, 2008, 09:35:21 am » |
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WHOA there settle down. lol Looking good though. But again, what do you plan to run these with?
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Forceaudio
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« Reply #17 on: March 20, 2008, 09:35:21 am » |
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MikeS
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« Reply #18 on: March 20, 2008, 12:06:49 pm » |
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Them fucken Craigslist faggots....heh.....
I'll use the amp with my Cornwalls, LaScalas, and the B&C 12CXB coaxials.....
I did answer your question about 2 days ago, but it evaporated.
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MikeS
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« Reply #19 on: March 23, 2008, 09:45:17 pm » |
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There................
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MikeS
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« Reply #20 on: March 23, 2008, 09:57:02 pm » |
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"I thought I might have a score for a Yamaha MX-800 power amp to run my subwoofers with. Listed on Craigslist in Readan, WA. I've emailed the twit twice, (no phone #) and no replies....." There is a Spokane eBay seller with a Yamaha MX-800 listed currently......Fag.....I would have at least used the amplifier..... This might be a good score for some vintage tube gear. There is a Eico HF-85 pre-amp in there that's worth 75 bucks alone....I just need to get out there to pay him tomorrow. http://spokane.craigslist.org/ele/615208740.html |
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todd.brust
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« Reply #21 on: March 24, 2008, 06:58:10 am » |
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Sweetness! You beat me by a few days!
I really like your clean layouts. From what I have seen in this amp and your Eico, you might be a candidate for OCD! lol
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« Last Edit: March 24, 2008, 07:02:36 am by todd.brust »
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Forceaudio
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« Reply #21 on: March 24, 2008, 06:58:10 am » |
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MikeS
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« Reply #22 on: December 05, 2008, 06:57:03 pm » |
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You know I got that amplifier going way back in April or May, and have listened to the unit a good 50-60 hours since then.
I had one hang-up right off the bat. I hooked up the feedback loop on one side wrong so it didn't function at all.
Easy fix........
I have compared this amplifier to the original little Magnavox I have, which uses polypropelene for coupling caps, with carbon composition and carbon film resistors.
The amplifier with the Caddock, Holco, and Mills resistors has good stereo separation, with more details seeming to pop out over the other. Bass is just as strong, and almost seems a teeny bit tighter.
But the other hand, the midrange and top end is a bit aggressive sounding, and a little hard and edgy. Not much in the way of warmth to be expected from a tube amp.
Single-ended 6BQ5 does have a bit of bite to it anyway, it's kind of a characteristic of the tube. This amp seems to accentuate this even more. Even with the Russian oil caps and using a good broke-in pair of Mullard EL-84's, the amp is still a bit hard sounding.
The original Magnavox amplifier has nice warm comfy sound that you can listen to for hours on end. However, it doesn't quite have the detail and stereo separation of the newer amp, with a slightest bit of smearing.
It does have about 4 years of break-in time over the new amplifier.
So I dunno......maybe I should slip a couple carbon composition resistors in some spots, and see if that may make things less hard sounding.
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MikeS
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« Reply #23 on: February 08, 2009, 11:48:28 pm » |
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I'm a complete n00b with a scope, but I took the little Magnavox and ran square waves through it with a signal generator at around 1kHz-5kHz, watching for overshoot and ringing.
My original Magnavox console amplifier uses a silver mica 330 picofarad cap for frequency compensation with the feedback loop. It was monitored and done with a scope at my retired EE friend's on his bench, when he lived up here.
This particular sample of Magnavox amplifer, (even though it's the same design) still showed some overshoot and ringing with a 330 picofarad silver mica cap. I figured the same design, the same value for the frequency comp cap.
I suppose that isn't necessarily the case, with the output transformers being just a little different from sample to sample.
(A guess....)
The original design doesn't even use a feedback bypass cap. And square waves without a frequency compensation capacitor look more akin to a heartbeat..........
510 picofarad ceramic caps worked the best. They cleaned up the square wave to where there is just weeny bit of ring of the top front left edge.
It seemed to help. The amplifier sounds rather listenable and nice now, you can listen to it all day and still want to listen more.
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Forceaudio
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