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Old 6th March 2012, 09:35 PM   #1
tvrgeek is offline tvrgeek  United States
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Default Not ready yet, but

I am not ready yet to build a monster dozen-pair class A amp yet, but...

OK, I have pretty decent hearing for an old guy, but my wife has ultra sensitive hearing. I have been discussing over in the lounge my quandary. With a lot of help and pushing, I have learned a lot of really basics about amp design in my effort to understand what we are hearing vs. objective measures that don't correlate. Read Self and Cordell, lots of white papers and 3000 or so posts from several highly respected folks who do this for a living. It comes down to this. Why the heck do my simple design bipolar Rotel 951's sound so much better than any of the more sophisticated designs from many well established and praise worthy designers?

When trumpets blare, it causes her pain. Live, no problem. (Harry James, King James Version track one for example) Simple yes/no and almost any level. I can hear differences in the bass strings of classical guitars, many amps making them sound metallic. (Bream plays Segovia for example) WHY? The quick fix is to keep buying old Rotels, but that is hard on the engineering side of me. I want to know why.

Short of building a monster "simple" amp without ever having heard one, are there any example products that may be available in e-bay that express the less is more philosophy of Mr. Pass? I don't have giant Louthers, but low efficiency bookshelf monitors, ( woofers happily powered by a John Curl Parasound, so no bass load needed) so my needs are probably upwards of 20W. I do happen to have picked up a Nak CA-5 that I think shows some of the simple side as a preamp.

I have been modifying an old DH-120 making it measurable cleaner, but with no positive change is sound. Am I going the wrong way? Should I remove the current mirror and reduce feedback instead? Should I pull the CCS in the IPS and VAS and use the space for regulated low current supplies? Are more outputs the real key? What's the thinking over here in Pass-land?
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Old 6th March 2012, 10:13 PM   #2
vdi_nenna is online now vdi_nenna  United States
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When trumpets blare, it causes her pain. Live, no problem.
There maybe [on certain electronics] more going on out of the hearing range than your wife and you can hear. Just because your ear/brain combo can't translate it, your ears can pick up on junk.

Maybe you should look for Threshold gear from when Mr Pass was there. It's still highly regarded gear today.
I build, therefore I am.
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Old 6th March 2012, 11:32 PM   #3
tvrgeek is offline tvrgeek  United States
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Also thought about the Nak PA-5 as it would sit nice with my ST-7 and CA-5. I think it was at least influenced by him. Still, I don't mind the cost as used these are a bargain, but never having heard one it is a rather expensive experiment. Which smaller Thresholds would that be? I know he did some Adcoms, but I was never enamored with them. Did he do any of the smaller ones? 50W or so? I don't need 200W for tweeters.

Failing amps range from B&K 140, Haflers, to the HCA 1200, and quite a few lessor ones. A couple of tube HK's, a Chinese tube, and all my Denons. These are all very well respected amps. I have not had her sit down with my Creek yet.

What I think is going on is some high order harmonics exciting tweeter breakup causing IM down in the audible range. Just a guess. She is just as tough on speakers, only a very few get the OK. None of mine yet, Sequels were too big, Vandersteins too ugly. I have Paradigm Studio 20's right now with my own Peerless based woofers.

I have an old Yamaha AVR not worth repairing with a really big transformer and heat sink, so one of the "smaller" ZEN's may be worth the effort, but I know 10W won't cut it. I was thinking it may work if I went to electronic crossover. A Zen-ish class a for the tweets, any decent AB for the mid.

Who else produced commercial amps with the "less is more" philosophy?
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Old 7th March 2012, 12:42 AM   #4
tvrgeek is offline tvrgeek  United States
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Adcom 535's go for a song. Maybe I'll try one of them.
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Old 7th March 2012, 04:34 AM   #5
boywonder is offline boywonder  United States
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Tvrgeek: Two suggestions.....try out some full range speakers and consider building one of the first watt or other NP designs. They are quite straightforward to build, PCBs are cheap and available (check out the DIY audio store and Peter Daniels), and there is lots of support here for your project if you decide to do one. Large heat sinks are probably the biggest ticket item.
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Old 7th March 2012, 05:38 AM   #6
generg is offline generg  Germany
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Not ready yet, but
The new BA-3 could be a possibility.....

No feedback and a pot to influence the distortion spectrum, so your wife could take part in finding the right mix......

Burning Amplifier BA-3

Good luck!
and the First Wtt is......a really First Class PSS Idea
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Old 7th March 2012, 07:25 AM   #7
Nelson Bass is offline Nelson Bass  Denmark
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Most commercial speakers have elevated treble level as this give the feeling of more details.

Full range drivers often shout to loud as well and have other problems that might be a problem for your wifes sensitive ears. Read this: http://www.troelsgravesen.dk/Lowther.htm
I have nothing against full range drivers but yet have to hear one I can live with. Let your wife hear one before buying one.

So I suggest you to try lower the treble level of your current speakers as its easy and cheap. You might even discover that live recordings will sound more natural as well.

If you're into a Pass amp I suggest you to read about the Firstwatt amplifiers and decide which one to build. The F5 is simple and very good.
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Old 7th March 2012, 10:28 AM   #8
tvrgeek is offline tvrgeek  United States
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Much thanks. I have been reading the BA series. I may have a suitable transformer and heat sink. I have not read the FW series yet. I need another project this big like another hole in my head. I would rather get back to building some more speakers, but this amp thing got me hooked.

On my list sometime is to build a another full range. I did a Jordan array many years ago. I really still can't see many advantages as you need considerable network work to get them to behave. Single driver units just can't do the job (100 up), and multi-driver get into all kinds of phase problems you are trying to avoid in the first place. Whatever the problem area is, it is not as simple as depressing the top or even reducing the typically boosted 4K range.
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