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In Reply to: RE: Or, perhaps, it is the Buckeye input amplifier to blame? posted by emailtim on December 23, 2024 at 15:13:04
Thanks for the info and I recant my skepticism! I looked at JA's measurements again and none of them are bad though the HF IMD is way, way higher than the Purifi datasheet but still not bad in absolute terms and, as JA noted, the energy in music rolls off pretty quickly so you'd certainly never encounter 50W at those frequencies! Even dropping the power by 20dB to a still high 5W those third order IMD terms would drop by 40dB and the fifth order terms by 60dB. Out of idle curiosity, I went to ASR to look for any Purifi measurements and found a whole thread about the Stereophile Buckeye review - lot's of conjecture until someone found the announcement from Purifi about the bad modules. I would be interested to know what happened, maybe a wrong value component got loaded into the SMT machine? But, I would have hoped that Purifi would have caught it at final test, maybe they didn't routinely do a high power IMD test and their test equipment doesn't have the resolution of an AP system to catch errors in very low distortion levels? Buckeye posted to the ASR thread and, it seems, they don't do any quantitative unit testing - a 'functional' test and a listening test. Maybe Buckeye don't have the resources for test equipment but, IMO, live by not testing, die by not testing. At least Buckeye now know their listening test isn't that effective so they could drop that:)
Follow Ups:
Buckeye said they acquired an AP and recently posted they no longer have it.They did not give a reason why they no longer have such a pertinent piece of test equipment. That is a bit troubling and was a validation point for a potential customer such as myself who could box and wire a DIY kit.
For the initial world-wide review, one would assume they would inspect the review sample inside and out.
I was always taught, "Expect only what you inspect", because customers have much better memories when things go wrong than when they go right. I often found that personal inspection practice to not be ubiquitous in corporate/commercial life.
I am concerned about the half power shutdown. The Hypex SMPS can not fully power the 9040, but the amp shut down at half the Hypex SMPS's spec'd max output. It missed the 9040's max output in 2 ways. I hope that issue identified and resolved as well.
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2022/03/30 Historical Records CENSORED
Edits: 12/24/24
An AP unit is expensive and while it would be a tax write off I wonder how many amps you'd have to sell to pat for it. Jason Stoddard, of Schitt, wrote about chosing test gear in his blog though I don't remember the details but I think they have less expensive alternatives for final test. The catch-22 maybe that if you are selling products with claimed super-low distortion that you need super-expensive test equipment to prove it. Maybe the upshot for both Buckeye and Purifi is to run a very high power, high frequency IMD test and if the result is good enough on reasonably priced test equipment then it is probably good enough.
I've no idea about the power shut down. My best guess, as before, is that a batch.of boards were built with the wrong value SMT components and final test does not push power to the limit.
I own a VTV purify-based amp with which I am very happy. It's one of those amps that someone here likes to classify as built in a garage.
From their website:
"VTV Amplifier proudly uses the latest AP5x high resolution Audio Precision test equipment to certify and ensure performance. Test results are provided with each amplifier. "
Nice that the measurements are provided. It is obviously a well equipped garage. Jason Stoddard wrote in his blog about the humble beginnings of Schitt in his garage and didn't Hewlett Packard start life in a garage? And at this time of year we are reminded of other humble beginnings in an an out building.
