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post #1 of 47 Old 06-11-2019, 03:43 PM - Thread Starter
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Adcom GFP 555 questions

Hello, I Have a Adcom GFP 555 preamp that will be hooked up to a Carver A-400X power amp and will be hooking up a Sub woofer also in my 2 channel system. The Adcom has 2 pre out connections labeled LAB and Normal, my question is is it possible to use both at same time so I can run two separate RCA cables one to the sub "line in" and the other to the power amp "input", otherwise normally most pre amps have 1 output jack to go to the power amp, and that would require 2 Y adapters to be used for the RCA LINE connection.

Until I can get another set of quality speaker cables to hook up to the Sub using the Hi level in/out , this is the route I need to go, just wasn't sure if it was possible to use both Pre out's on preamp at once,

"LAB" pre out on Adcom pre amp is for Direct coupled.
"Normal" pre out is for Capacitance coupled.

Sub woofer being used is a Klipsch KSW 200 powered.

Appreciate any input, thnks
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post #2 of 47 Old 06-11-2019, 05:30 PM
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Both outputs work concurrently and you can use them at the same time.

I'd use the "lab" out for the sub since in has no bass filtration.
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post #3 of 47 Old 06-11-2019, 11:57 PM - Thread Starter
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Quote:
Originally Posted by m. zillch View Post
Both outputs work concurrently and you can use them at the same time.

I'd use the "lab" out for the sub since in has no bass filtration.
Thanks for the input!!
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post #4 of 47 Old 06-12-2019, 11:53 AM
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From the GFP-555 user manual:

"The direct coupled LAB output is used with power amps such as the ADCOM models that are able to handle signals of extremely wide bandwidth. Simply stated, the purest sound can be derived from the LAB output since there are no capacitors at the output to filter out musical information. However, some amplifiers may have protection circuits which are unable to handle such an unadulterated signal. For this reason we have provided the NORM outputs."

After reading Carver's info, the amp does not have any unusual protection circuits nor is there any other reason that would require capacitors to be in the signal path. Thus, you can use the Adcom's LAB output with your power amplifier, which would be my choice to maximize sound quality. I would then use the Norm output for the subwoofer.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #5 of 47 Old 06-12-2019, 12:27 PM - Thread Starter
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Thanks for the input also, two different suggestions, I will investigate further, thank you!
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post #6 of 47 Old 06-12-2019, 12:41 PM
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Originally Posted by pizzano View Post
Thanks for the input also, two different suggestions, I will investigate further, thank you!
There's a 50/50 shot that one will be better than the other.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
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post #7 of 47 Old 06-12-2019, 01:12 PM
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In the revised version, the GFP-555II, Adcom upgraded the capacitors in the output to reduce sound degradation. Try both outputs with the Carver amp and see what you prefer.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #8 of 47 Old 06-12-2019, 01:55 PM
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Quote:
Originally Posted by m. zillch View Post
Both outputs work concurrently and you can use them at the same time.

I'd use the "lab" out for the sub since in has no bass filtration.
I doubt it would make much of a difference in real world use under blind listening conditions [even if you upgraded to a $8K sub], however here is a graphic showing the bass filtration of the "Normal" outputs on a similar Adcom preamp at the time (which included a tuner and remote), the GTP-500 II:

https://www.kenrockwell.com/audio/ad...Infrasonic.gif

Here's the same preamp's "Lab" output, however notice the x-axis is greatly expanded to make it easier to see a subtle (but inconsequential) bump:

https://www.kenrockwell.com/audio/ad...-Infra-1dB.gif

I was an Adcom dealer when these preamps were in production, BTW.
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post #9 of 47 Old 06-12-2019, 02:02 PM
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post #10 of 47 Old 06-12-2019, 04:09 PM
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The minuscule frequency response difference is not the concern, it is the overall sound quality that is relevant, which is why Adcom provided a direct signal path option and decided to upgrade the capacitors in the revised version. Whether one output sounds better than the other is, of course, up to the OP to determine.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #11 of 47 Old 06-12-2019, 04:27 PM
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"For good sound quality use our output 1 jacks. For users who prefer bad sound quality, use our output 2 jacks"

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post #12 of 47 Old 06-12-2019, 06:54 PM
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Adcom is honest about the outputs: "Simply stated, the purest sound can be derived from the LAB output since there are no capacitors at the output to filter out musical information." They make it clear that one output is more sonically transparent than the other. I would choose the one that offers more transparency.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
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post #13 of 47 Old 06-12-2019, 07:39 PM
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You don't understand what they mean by "musical information" and have instead decided to transform it to mean whatever you want.

They mean deep bass extension, or "bandwidth" as they call it.
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post #14 of 47 Old 06-12-2019, 11:34 PM - Thread Starter
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Simply stated by Adcom that the direct coupled LAB output is recommended for amps that can handle signals of extremely wide bandwidths, the only specs I can find on the Carver A-400X is a 20-20k Khz, so I guess the question is, is the Carver fall into the description of able to handle wide bandwidths.

I will try mating the" LAB" to the amp and the "Normal" to the Sub, My thoughts in the beginning of this was to eliminate the use of just using one output which every it may be, over using 2 Y adapters off of the one preout which ever it may be, (least amount of connections I assumed would be musically better).

With that said, any thoughts on the bi wiring aspect, I have read many different opinions on both sides , saying its useless and some saying it helps in sound putting less stress on the different HF & LF, my concern is if I went the route of using the Hi level in/out speaker connection , the speaker cables from the amp to the input of the Hi level on the Sub are single wire and the bi wired cables would be from the output to the speakers, confused if the in and out of the Hi level connection would be hindered by the bi wired cables not coming directly from the amp to speakers.

Speakers used are Polk RTi7

Thanks again for the input folks
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post #15 of 47 Old 06-12-2019, 11:34 PM
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Quote:
Originally Posted by m. zillch View Post
You don't understand what they mean by "musical information" and have instead decided to transform it to mean whatever you want.

They mean deep bass extension, or "bandwidth" as they call it.
Once again you have nothing better to do than toss out an insult and attempt to start a fight. Do not tell me that I do not understand what is meant by "musical information." Frequency response is only one component of musical information.

I realize the purpose of avoiding caps in the signal path and have had at least two discussions about the subject with preamp designers in years past. Capacitors can degrade the sound, often causing a degree of edginess and harshness in the upper midrange and lower treble. Removing one or more caps in critical areas can result in clearer and smoother sound quality. I had such a modification done on a preamp in the early 1980s. The improvement was significant.

In Adcom's GFP-555, the designer felt a need to offer some frequency response rolloff if needed with any power amplifier that could not handle extended bandwidth, as they explained in the user manual. But for more typical amplifiers, the LAB output should be used for "the purest sound." In the revised model, they retained a cap in the output but utilized a superior one to improve the sound quality, again to provide a purer sound. For the GFP-555, "the purest sound" does not refer simply to a a flatter frequency response that starts below about 7 Hz.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #16 of 47 Old 06-12-2019, 11:41 PM - Thread Starter
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Once again you have nothing better to do than toss out an insult and attempt to start a fight. Do not tell me that I do not understand what is meant by "musical information." Frequency response is only one component of musical information.

I realize the purpose of avoiding caps in the signal path and have had at least two discussions about the subject with preamp designers in years past. Capacitors can degrade the sound, often causing a degree of edginess and harshness in the upper midrange and lower treble. Removing one or more caps in critical areas can result in clearer and smoother sound quality. I had such a modification done on a preamp in the early 1980s. The improvement was significant.

In Adcom's GFP-555, the designer felt a need to offer some frequency response rolloff if needed with any power amplifier that could not handle extended bandwidth, as they explained in the user manual. But for more typical amplifiers, the LAB output should be used for "the purest sound." In the revised model, they retained a cap in the output but utilized a superior one to improve the sound quality, again to provide a purer sound. For the GFP-555, "the purest sound" does not refer simply to a a flatter frequency response that starts below about 7 Hz.

Cmon folks I didn't start this post so members get in a verbal tussel, I am simply trying to equate which hook ups would work best according to what any specs or reviews were printed for this equipment, Bottom line is I only would like to have my system moved once and do one hook up correctly due to I am Handicapped and moving all this stuff is a PITA.

With that said I appreciate everyone's feedback, hell I am not an expert hence starting this post.

Thanks again
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post #17 of 47 Old 06-12-2019, 11:55 PM
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Once again you have nothing better to do than toss out an insult and attempt to start a fight. Do not tell me that I do not understand
You either do not understand or have intentionally omitted critical information. Interesting how you conveniently failed to quote the sentence preceding the one you did which clearly explains the real technical difference, not your imagined one: It's bandwidth just like I wrote and documented with measurements on a similar Adcom. Here's his owner's manual's explanation:



For people who don't understand what bandwidth means they have a simpler version using lay-men's terms, hence the sentence which starts with "Simply stated", which translates bandwidth using the easier to understand words "filter[ed] out musical information".

As a (former) dealer I've been trained by Adcom technicians. Have you?
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Capacitors can degrade the sound, often causing a degree of edginess and harshness in the upper midrange and lower treble.
I'd like to learn more. Have you any evidence based science to back this using controlled listening tests of actual production units? I'm not interested in your anecdotal observations.

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post #19 of 47 Old 06-13-2019, 12:12 AM
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any thoughts on the bi wiring aspect
It's a scam invented so consumers will buy-wire: twice as much as they actually need so the dealer's profit doubles. This industry, I know quite well, is swimming in myths and scams.

People who don't use protocols to preclude expectation bias from their listening tests often fall for things like biwiring so you will find lots of supporters though.

Learn more on the importance of proper testing here: https://seanolive.blogspot.com/2009/...o-product.html

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post #20 of 47 Old 06-13-2019, 10:49 AM
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Cmon folks I didn't start this post so members get in a verbal tussel, I am simply trying to equate which hook ups would work best...
It is an ongoing problem on this website. A discussion is upended with an insult and an attack in an effort to start a fight. Well-meaning posters have to deal with it all the time.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #21 of 47 Old 06-13-2019, 11:21 AM
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The real problem with this site is a meaningful discussion of audio science is stifled by the constant chorus of audio mythology and parroting of unsubstantiated marketing claims.

"Audio as a hobby is dying, largely by its own hand. As far as the real world is concerned, high-end audio lost its credibility during the 1980s, when it flatly refused to submit to the kind of basic honesty controls (double-blind testing, for example) that had legitimized every other serious scientific endeavor since Pascal. [This refusal] is a source of endless derisive amusement among rational people and of perpetual embarrassment for me..”


- J. Gordon Holt, founder of Stereophile magazine, spoken close to his retirement date.

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post #22 of 47 Old 06-13-2019, 02:31 PM
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Quote:
Originally Posted by m. zillch View Post
You either do not understand or have intentionally omitted critical information. Interesting how you conveniently failed to quote the sentence preceding the one you did which clearly explains the real technical difference, not your imagined one: It's bandwidth just like I wrote and documented with measurements on a similar Adcom. Here's his owner's manual's explanation:



For people who don't understand what bandwidth means they have a simpler version using lay-men's terms, hence the sentence which starts with "Simply stated", which translates bandwidth using the easier to understand words "filter[ed] out musical information".

As a (former) dealer I've been trained by Adcom technicians. Have you?
I did not omit any critical information. The sentence to which you refer is redundant with what follows. I am the person who dug up the user manual to help the OP.

Your posts make it obvious you never received any training from Adcom. I remember back in the early 1990s when there were discussions about Adcom providing different preamp outputs. The talk was mostly about the upscale GFP-565. Adcom provided three outputs on that model: one was cap coupled; a second allowed the user to skip tone controls and switchable filters; and a third bypassed all but volume and balance. I found a review of the 565 in Audio magazine (link below) that explained the differences in outputs:

"Fortunately, the GFP-565's purist-oriented features include three different types of output--all with a low, 100-ohm impedance to minimize interaction with power amplifiers and help preserve maximum dynamic range. The "Bypass"output provides the cleanest signal path possible, with a minimum of components in the signal path. Only the volume and balance controls then affect the sound--a far wiser approach to purity than preamp designs that omit the balance control and ignore the very real imbalances in left and right signal strength in many recordings. The "Lab" output" is identical to "Bypass" unless the filters and tone controls are switched in. The "Normal" output is identical to "Lab" but is capacitively coupled with high-grade Roederstein capacitors.

"I suppose that I hardly need say that I prefer the "Bypass" output. There are no night-and-day differences in sound quality, but with top-quality high-end amplifiers and speakers, you can clearly hear the difference between the "Bypass" and "Lab" outputs, and even my nonaudiophile kids could still pick up some relatively minor differences between the two. Equally important, if you use the "Bypass" output, your significant others cannot sneak up on you, and switch in the controls when you're not looking--something my rock-oriented daughter has done on occasion in what seems an unending quest to convert a high-end system into the ultimate boombox.

"In fairness, many mid-fi systems are not likely to reveal most of the coloration you add as you go from the shortest to the most complex signal path, particularly those systems with relatively small speakers that suffer both from limited bass and from a roll-off and loss of speed in the upper octaves. There also are a number of transistor and tube amplifiers that really need capacitive coupling. This is especially true of older models. No competent recent design should need such protection, but you should consult your dealer or amplifier manufacturer before using the "Bypass" output."

Adcom wanted users to have a choice of outputs that provide different levels of sonic purity. It is about sound quality, not simply an ultra-low-frequency rolloff versus a flatter frequency response as you insist. A dealer trained by Adcom would know the reasons for the different outputs. I remembered and explained it.

https://www.americanradiohistory.com...io-1990-10.pdf

As for your other unnecessary attack, I was the first person to purchase an Adcom preamp, the GFP-1. I lived nearby Adcom's facility in North Brunswick, NJ. My dealer received the first units and I picked one up immediately upon their arrival. It was defective, but my dealer telephoned Adcom who then invited me to visit their offices and to replace the preamp. Years later I also visited their new huge facility in East Brunswick, NJ, this time to exchange a defective power amp. Adcom's staff were always friendly and informative.

I have spent time with Adcom's personnel at their manufacturing facilities and learned first-hand about their products. Have you?

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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It is an ongoing problem on this website. A discussion is upended with an insult and an attack in an effort to start a fight.
Where were you insulted? Zillch merely pointed out your errors. That's actually the kindest thing he could do to you, instead of cruelly allowing you to labor under your misconceptions.

Quote:
Well-meaning posters have to deal with it all the time.
A posting with the best of intentions is neither guaranteed to be true nor automatically earned sanctuary from criticism.

Everything has distortion. Some things have more distortion than others. It's meaningless to lump all distortion together as a single number- if you're going to discuss it you'd better be able to describe the spectra at different frequencies, at different levels, at different loads. And then you'd better be able to describe the setup used to measure it.

Subjective anecdotes are *almost* worthless, but especially ones that involve extensive changes to components inside gear. Your auditory memory lasts only seconds, how long did it take to upgrade the gear? Did you change it back again, so you could compare back and forth? Did you *measure* with anything besides ears?

To be fair, electrolytic capacitors fall very far from the ideal model. But everybody and their dog knows this, and they are used accordingly. Perhaps the caps in your gear were defective, damaged, or poorly implemented in the design. That's not a valid reason to denigrate all designs that use them.

Coupling capacitors are very useful for blocking DC. If a preamp produces (or from a source perpetuates) significant DC, a downstream power amp that also passes DC will amplify it and destroy most speakers in less than a second. That's a pretty good reason for blocking caps and DC protection circuits.
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Capacitors can degrade the sound, often causing a degree of edginess and harshness in the upper midrange and lower treble.
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Originally Posted by m. zillch View Post
I'd like to learn more. Have you any evidence based science to back this using controlled listening tests of actual production units? I'm not interested in your anecdotal observations.
If you actually (1) kept up with the R&D and discussions on the subject over the last 40 years or so, (2) tested components in your home and did so with no preconceived "opinions," and/or (3) attended professionally conducted DBT tests (which you refuse to do), you would not have had to ask. I do not have the time to provide a remedial audio lesson. Please do your own homework.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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post #26 of 47 Old 06-13-2019, 03:10 PM
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Originally Posted by Alex F. View Post
Your posts make it obvious you never received any training from Adcom.
I received training from them however I wasn't so gullible that I fell for their baloney about their "audibly superior" capacitors made of unicorn tears in later models so I don't repeat that nonsense here and instead stick to what matters: bandwidth differences.

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"I have spent time with Adcom's personnel at their manufacturing facilities and learned first-hand about their products. Have you?"
I have never been to their corporate buildings, no. Their techies came to my company for product training sessions.

I think what you really need is to spend some time with an ABX compactor (and learn how to precisely level match) so you'll discover the truth first hand.
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Originally Posted by Alex F. View Post
I do not have the time to provide a remedial audio lesson
You really think people here are going to fall for that? Yikes. We aren't that dumb.

Here's the truth folks: He can't find any of the tests I asked for because they don't exit.

Last edited by m. zillch; 06-13-2019 at 03:24 PM.
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post #28 of 47 Old 06-13-2019, 03:16 PM
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Originally Posted by fill35U View Post
Where were you insulted? Zillch merely pointed out your errors. That's actually the kindest thing he could do to you, instead of cruelly allowing you to labor under your misconceptions.

A posting with the best of intentions is neither guaranteed to be true nor automatically earned sanctuary from criticism.

Everything has distortion. Some things have more distortion than others. It's meaningless to lump all distortion together as a single number- if you're going to discuss it you'd better be able to describe the spectra at different frequencies, at different levels, at different loads. And then you'd better be able to describe the setup used to measure it.

Subjective anecdotes are *almost* worthless, but especially ones that involve extensive changes to components inside gear. Your auditory memory lasts only seconds, how long did it take to upgrade the gear? Did you change it back again, so you could compare back and forth? Did you *measure* with anything besides ears?

To be fair, electrolytic capacitors fall very far from the ideal model. But everybody and their dog knows this, and they are used accordingly. Perhaps the caps in your gear were defective, damaged, or poorly implemented in the design. That's not a valid reason to denigrate all designs that use them.

Coupling capacitors are very useful for blocking DC. If a preamp produces (or from a source perpetuates) significant DC, a downstream power amp that also passes DC will amplify it and destroy most speakers in less than a second. That's a pretty good reason for blocking caps and DC protection circuits.
So an insult is not an insult and accuracy is now a misconception.

As for coupling caps and what you said, nothing new there.

Music room: Cary SLI-80 tube integrated amplifier, McIntosh MA6500 integrated amplifier, Quad 99 preamp, Quad 909 power amp, Acoustic Research AR9 loudspeakers, Yamaha CD-N500 CD player, Teac UD-503 DSD DAC, Phase Linear 8000II linear-tracking turntable.
Theater room: Panasonic 65S60 plasma television; Yamaha RX-A2020 (preamp section); Adcom GFA-5503 and GFA-5400 amplifiers; Polk LSi25, LSiC, and LSiF/X loudspeaker system; Velodyne FSR-18 servo-subwoofer.
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Originally Posted by Alex F. View Post
(3) attended professionally conducted DBT tests (which you refuse to do),
False.
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post #30 of 47 Old 06-13-2019, 03:29 PM
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Maybe I could improve the sound of my preamp's capacitors if I thought they were like all fancy and stuff. . . and cost more? Hmm. . .
https://www.cnet.com/news/study-90-w...me-wine-at-10/

Last edited by m. zillch; 06-13-2019 at 11:49 PM.
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