Discussion in 'General Audio Discussion' started by Negotiableterms, Jul 22, 2015.
Having a 500 joule power supply does wonders for sound quality.
After I built my Heathkit AR-1500 receiver back in those heady hi-fi days of 1972, I had it tested at a McIntosh "clinic," where they hope to demonstrate that your item is substandard due to test measurements vs. published specs and generate sales. I'll never forget the McIntosh Sales/Tech person's remark that "If you keep building these like this we'll never sell you a McIntosh." The AR-1500 was considered to be the most powerful and sensitive receiver at that time, and even the stodgy & somewhat biased Consumer Reports magazine concurred.
I took my AR Integrated to one such event in 1972 where Dave O'Brien handed me the personalized THD graph verifying that it was performing to the 0.25% spec.
It was that experience as a teenager that illustrated the meaningless of hte total harmonic distortion metric as really telling you anything useful about how an amplifier actually sounds. While the AR was fine at high levels, low level resolution was poor. I've owned many amplifiers since that likely measure no better, but sound considerably more transparent.
You didn't see the graph I was presented with, showing total RMS power per channel at 40% above spec with THD markedly below spec. Add to that the fact that it was rated as the best receiver on the market in those years, even in AM mode. It had a power supply and transformer that elevated it far above the scads of crummy amps and receivers of that period. Plus it was aesthetically appealing and uncluttered. The opinion of the trained McIntosh technician not withstanding, I guess our ears hear things differently. No worries .Cheers.
What I discovered is THD, no matter how *good* it looks, is a largely irrelevant metric to provide any useful knowledge about sound quality.
In fact, I avoid units with exceptionally low numbers because you know the designer took the easy way to get those by dialing in tons of corrective feedback at the expense of sound quality. The Crown D150 I had for a short time had great numbers. And still sounded bad.
With all due respect, there are dozens of reasons why your D150 may have sounded bad thru no fault of its own. I try to not fall into the "conjecture" trap regarding nefarious designers. If the product is from good stock (not Montgomery Ward, etc.), has a good reputation, low THD and IMD, a flat frequency response at power, a compliant phono stage, and a robust power supply capable of handling low frequency response and transients galore on demand, I'm all ears. Especially back in the early 70s when such equipment was either hard to find and/or out of the price range of the average young audiophile like me. I couldn't afford a Crown or McIntosh but I could afford $350 for the kit, which I enjoyed building and using for many years. Excuse me for thinking that this was the point of the thread. Cheers.
Why it has poor sound is easily documented. It ran in class B output mode using a crude, first generation Fairchild ua739 op amp with tons of corrective feedback. While later versions still ran the outputs with no bias in class B, at least they used LF357 op amps. Frank Van Alstine used those to replace similarly the similarly bad sounding LM301 found in the Dynaco PAT5 with his FET5 modification. I had one of those from about 1976-1981.
I was a bit unusual buying one at age 17. I was also interested in the ICK preamp, but the dealer provided a listening comparison to a Citation 11 which quickly determined my choice. I confess that I was taken with the Crown's 4 ohm output power to drive double Advents vs alternatives.
Some "classic high end gear" was better than others. Audio Research gear (also carried by that dealer) was substantially better sounding. While I couldn't afford that brand as a teenager, I purchased an SP-6C at 23 and currently use a DAC8 and SP20.
Yes, the Audio Research gear was formidable. We were fortunate to ride the new wave of high fidelity that began in 1969 and learn the ropes. My dad was radioman on a ship in the S.Pacific during WWII and later became a Heathkit fan, and I followed in his well-advised footsteps. We built many kits together.
Back in the day my best audiophile friend/competitor had a KLH system. It sounded great but I was not a fan of acoustic suspension speakers. I went for high efficiency and to this day the foundation of my system is the Heathkit AA-1800 and AP-1800 plus JBL L112 speakers.
I really appreciate the polite discourse and education. Good on ya.
I remember the Heath store located near me. I went the Dyna route and built a couple of their kits as a teen. That basic understanding and practice with assembly/soldering allowed me to perform basic modifications later on. Following FVA's lead with his Double Dyna mod, I built an external power supply for an Audire amplifier with an additional 60,000 uF of capacitance and new bridge. Quadrupling the stiffness to 100 joules taught me the value of using truly large power supplies. Sound quality became more dynamic and transparent. A later Threshold Stasis amp started out that way so Nelson Pass seems to agree.
That is always my intention. As an IT guy, I tend to be direct in my assessments which may not appeal to everyone.
I KNEW you were a kit builder. I learned a lot from the experience, but I see your skills surpass my own. I have a good working background in electronics, audio theory of operation, and understanding of specs, but no formal tech education, and there's the rub.
I have a "repair & revitalize" project going on that I have stalled on - coincidentally, a cosmetically mint AR-1500A that I got from ebay. The seller claimed it was in working order, but it wasn't. I kept it because of the seller's hard-luck story, the unit's potential to be a stand out, and the chance to reclaim my youth.
If I lived in your neighborhood you'd be my new best friend as a pursued the project.
You nailed it, although Lord knows we've all seen worse. Thank goodness things have improved, and buyers are increasingly savvy.
Good luck with your project!
While more of simply an assembly task, I've enjoyed learning about and using a Raspberry PI computer as a digital renderer for the garage system. It does require some understanding of the various hardware and software options and settings.
I am a newbee. Appreciate your advice. Want to pair a SS power amp Mcintosh MC 2100 with Conrad Johnson PV 2A or PV 6 to be played through my JBL L 150A speakers.
You should favor your JBLs with a higher-powered system. But then, I'm just an unfrozen caveman lawyer...
sub'd to this thread
I should do a pic but my little pair of Bogen DB 110's are very sweet to my ears. And from what 1957 is my best guess if I am wrong feel free to tell me. It won't change my opinion on them. And for just a few bucks back when you could get sometings nice for a few bucks.
Missed this thread for a while. One true classic is the Conrad Johnson Premier 12 monoblocks, 140 watts each. Its smaller sibling is the Premier 11 (70 watts/ch), and big brother the behemoth Premier 8 monoblocks (275 watts each). All use the same basic circuitry. Many have praised the Premier 12s over the years as being the last of the "classic" C-J sound, and they received many favorable reviews in the press. Even today they are hard to come by--I only see a few sets per year show up for sale. I have a Premier 11 currently, but my long-term plan is for a set of Premier 12s. Sure, I'd love Premier 8s instead, but 1) they burn a lot more kilowatt-hours which would please the utility company, and 2) retubing those is pricey. (Between the two, 16 KT120s, and twelve smaller tubes that would be a mix of 5751s and 6CG7/6FQ7s).
Loving this thread!
Well I'm not sure how vintage we go here. But this is one of my systems. I haves since taken the Adcom out of service and it has been replaced with a Dynaco st-70 that I love. And I moved my old Maggie MMG's down here Since I bought new 1.7's for upstairs. I also keep quite a few 60's/70's receivers and Cassette decks around as well. I could make a list but it would be very long. I have had the Pioneer 707 since new in 77. Still works and sounds fantastic. I also have a stash of NOS cartridges from Empire, Stanton, Pickering and a few Ortofons as well. Right now the Kenwood has a 681EE on it. I also added a Macintosh MVP 861 that is currently doing the CD's.
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