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In Reply to: RE: Measuring properties or changing operation? posted by rick_m on June 25, 2009 at 06:35:16
Recently I witnessed an improvement in sound with usage of an aftermarket power cord on a SS power amplifier (replacing yet another aftermarket power cord) that rather shocked me.The main reason for the shock was largely due to the fact that the effect ran counter to my experience, that power cords seem to make the least impact on SS power amplifiers vs. source/preamp/low power gear; regardless of how counterintuitive that may seem.
The second reason for the shock was due to the particular SS amplifier, a Bryston 4BST, an amplifier which along with its SST sibling has long ranked in my most hated list. The ills associated with the 4BST/SST, what I would call electronic sheen (a subjective description) seemed to me to have vanished!
Now do we have an engineer present who would like to step up to the podium and propose that the power supply design of a Bryston 4BST is inadequate? I rather doubt we'll witness such at thing. The point is that one can lean on one's engineering principles/background, bring in ideas from other fields and what-not, but the rubber hitting the tarmac is a different story altogether.
---
OH, having had a peek inside a Bryston 4BST ... the one I had on a home trial, that incidentally embarrassed itself against the Kenwood L-07M monoblocks (late 70's production) I was then using ... I was a bit surprised by what I thought was relatively modest sizing of the capacitor banks. Certainly many other current designs provide a heck of a lot more for the power rating. Still from an engineering perspective no doubt the sizing is more than adequate; it's true that (per side) storage *was* greater than what was in the much older L-07M.
(The L-07Ms had had their captive zipcord replaced with garden variety outdoor (orange) extenstion cord (that's how they were when I got them) and IIRC I used the stock power cord provided with the Bryston. At that time I likely wouldn't have had anything much better lying around to try on the 4BST).
Everything matters, don't forget to tweak your placebos!
Edits: 06/25/09
Your findings raise a more-important point.......
Bryston amplifiers have often been deemed "properly designed" by the so-called "scientific" audio community, in regard to how little effect audio cabling should have on sound if interfaced to such designs.
But based on your findings, even this respected amp line is apparently affected sonically by cabling. (I've always suspected this would be the case. I've never come across an amplifier that was immune to cabling.)
So the term "properly designed" is nothing more than an ideal that seems to **never** exist in reality. Yet this idealistic term is often mentioned as factual basis for why audio cables don't or shouldn't impact sound.
It does seem to be mostly semantics doesn't it. In fact as best as I can tell at least one of our resident "engineers" (Don Till) seems to have taken it to a declarative/definition level by essentially stating that if an amplifier's performance varies with usage of power cords then by definition its power supply is not "well designed"... and it seems he's more than willing to include Bryston in the poorly designed group (assuming there's any truth to my report of course!).
So isn't that so very clever! Power cord are hence allowed to effect performance along with a nice tidy reason for why this is the case... our engineer sleeps well at night and all in the universe is in order!
LOL
Everything matters, don't forget to tweak your placebos!
"So isn't that so very clever! Power cord are hence allowed to effect performance along with a nice tidy reason for why this is the case... our engineer sleeps well at night and all in the universe is in order!"
And are you suggesting things are somehow different? As if there aren't tradeoffs made in every component design at every price point. Some of us might immediately condemn a slight high frequency roll off or minor transient shaping at the same time ignore, or even worse claim higher resolution from components displaying problems protecting itself from being influenced by external factors.
deny my call on your definition/declaration!
LOL
Everything matters, don't forget to tweak your placebos!
Why should I deny it? If I establish the level of acceptable performance for a well designed component as being not audibly effected by external influences in normal operating conditions it's not like I'm setting a high bar. Or am I?
And just to clarify this. I don't believe the Bryston as you describe it is working to spec (as advertised), just like my Raysonic CDP that greatly benefits from an "better" power cord. It's not like I think the sound of these things get betters than advertised when external power cords or conditioners are applied. I think only then do they deliver on the promise of the original purchase.
It may be that the particular instance of the amplifier was defective. This could be the result of a component or wiring failure. Or perhaps a batch of instances were defective. This could be the result of Manufacturing performing some "value engineering".
A company that sold audio kits many years ago used to do this kind of "value engineering". The purchasing agent would make "minor" substitutions of component values or tolerances to reduce parts cost. I heard this from the purchasing agent's son.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Of course, there's always a possibility of amplifier being defective - it's just that being affected by power cord change is in no way or shape the sign of "defectiveness".
More experience with resolving equipment, and less preconceived notions in the head - that's best possible cure against such "defects" in amplifiers.
Actually I was quite serious.
I have had a defective amplifier, and it was in the power supply, no less. As it turned out, the defect wasn't at all subtle—it resulted in a moderately loud hum in one channel. The amplifier had separate output filter capacitors for each channel and one of the four had gone bad. The manufacturer had gone out of business and there was no direct replacement available at "You-do-it Electronics" so I substituted four new capacitors of slightly larger size, which fit only when held in by duct tape. Interestingly enough, the result was a significant improvement in sound over what it had been prior to the failure. I presume that the original capacitors either lacked sufficient energy storage capacity when new, or perhaps had gradually lost their capacity over time.
Had the failure been in the input power line filter then I might not have noticed it, at least not until I moved into an environment with lots of EMI. At that point, I might have effected a sonic improvement by replacing the defective internal components or by attaching an external power cord that provides rejection.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
In this instance I have to rely on the veracity of bjh's observations - ie. they are presented in such a way that indicates it's not a one time observation and have been repeatable in a variety of different situations. At least that was my take on the wording of his opinion of Bryston equipment.
In my normal work environment when issues come up the first thing I like to do is to witness them. Whether this occurs in the lab or I reproduce them at my desk kind of depends on the importance and severity of the issue.
I agree with your take it could be a defective unit and the defect could be for one of any number of reasons. However and again - the comments I'm relying upon indicate this is the normal performance one achieves from the Bryston amplifiers in question.
Often when I get to the lab or reproduce the issues as described by a customer, technician, marketeer or even other engineer the issue is actually quite different than the description. I'm giving bjh the benefit of the doubt for the purposes of this conversation.
.
Everything matters, don't forget to tweak your placebos!
by members of self-proclaimed "scientific" community, for effects of substituting different power cords. The same as with, for instance, Van Alstine DAC, that according to manufacturer, was supposed to be immune to differences between transports - but wasn't.
Why would the pseudo-scientific community test for a foregone conclusion??? They might discover the world isn't flat!!! How can you remain an audio regressionist if you test things all the time???? :)
"Now do we have an engineer present who would like to step up to the podium and propose that the power supply design of a Bryston 4BST is inadequate? I rather doubt we'll witness such at thing.
Given that the amplifier as supplied merits the following comment when an after market power cord is installed -
" The second reason for the shock was due to the particular SS amplifier, a Bryston 4BST, an amplifier which along with its SST sibling has long ranked in my most hated list. The ills associated with the 4BST/SST, what I would call electronic sheen (a subjective description) seemed to me to have vanished!"
I would say yes the amplifier power supply filtering is inadequete, based on your comments for the environment in which you made your observations. I can't believe the designers of this amplifier intended the "electronic sheen" and I hardly doubt it takes an experienced golden eared trained listener to hear it.
But alas if one can buy a Bryston power line conditioner or any number of after market power cords to solve the problem who's to complain?
Personally this is the kind of crapola that long ago turned me against the marketing vehicles posing as audiophile magazines willing to tolerate such performance deficiencies to further their vested interests in growing the industry.
Sure power cords and conditioners can and do often make a tremendous difference and most anyone should be able to hear it.
Communications and test equipment owner's wouldn't tolerate for an instant such haphazardly designed products. Funny how audiophiles and the industry in general seems to tolerate it at the same time marketing spending for the work arounds as ways of bringing home improved performance.
I would have added an exception for you.
Everything matters, don't forget to tweak your placebos!
"The point is that one can lean on one's engineering principles/background, bring in ideas from other fields and what-not, but the rubber hitting the tarmac is a different story altogether."
No it's not a different thing, not at all. Whether possibilities jump out at you or need to be sought after does somewhat depend upon what 'other fields' you have been plowing.
So, the power cord changes the sound, what does that mean and to whom does it mean it? Does the product no longer meet it's specifications? Probably not. Does it mean that the specifications are inadequate? Maybe.
Most likely if there is an error it's that in the internal product requirements. Either what you are experiencing was regarded as insignificant or whatever is causing it was missed completely. You can usually rely upon products meeting their production specifications, what's a lot iffier is relying upon those specifications to predict the outcome for all users.
"I was a bit surprised by what I thought was relatively modest sizing of the capacitor banks."
Physical size? Capacitance? ESR? Net energy storage? Capacitors have come a long way the last decade, especially in terms of HF ESR. How much capacitance you need depends upon the headroom and PSRR of the amplifier.
One of the things that's fun about this hobby is all of the counter-intuitive things you find that can affect the sound. I've had rum luck predicting whether I'll like the sound of something without listening to it. Size, color, cost, weight, brand et al are poor predictors. How can you tell a "better" power cord without trying it in a particular application?
Rick
> > "The point is that one can lean on one's engineering
> > principles/background, bring in ideas from other fields and what-not,
> > but the rubber hitting the tarmac is a different story altogether."
> No it's not a different thing, not at all. Whether possibilities jump
> out at you or need to be sought after does somewhat depend upon
> what 'other fields' you have been plowing.
If the exposure to 'other fields' merely informs to discount anecdotal evidence (power supplies are adequate, hence reports are fictions), or dissuades investigation (power supplies are obviously ill-designed, not worth bothering with), which seems to me to be just barely concealed (intentional or otherwise) message(s) in tomservo's post, then I would maintain the 'other fields' applicability is null.
I won't bother with the other points as they seems to me more than a little argumentative oriented.
Everything matters, don't forget to tweak your placebos!
I don't understand where you are coming from. This is a discussion, not an argument. I didn't see Tom discounting the issue as much as advocating that it can be fixed. I'm essentially on the same page but in trying to address your question of whether hearing a difference due to changing a cord meant a defective power supply tried to broaden it out to examine reasons both social and technical that they might especially at the system level even if the individual components were within spec.
Sorry if I waxed too philosophic, no harm intended.
Rick
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