AMplifer A/B Blind testing- Time to hear for myself!

[captainobvious]

I'm cross posting this here as well for my banned brethren


"The Goal"

I have a little pile of amplifiers at my disposal(some A/B, some class D, some large, some small, some old and some new, and some expensive, some middle of the road) and I want to determine first if I CAN hear a difference between them, and then, which I prefer and for what reasons.

I want to do a blind test so that I am not influenced by anything other than what my ears are hearing. Below I will detail the equipment and what I'm planning-please point out anything that could be a potential issue and advise of any easier methods you might recommend. One caveat- The process has to be fairly simple and not require much outside expensive gear other than what is available at my disposal already.


"The Gear"
TPS 75amp DC powersupply
Pioneer P99RS Source
Alesis Monitor Two studio monitors (10"/4"/1" configuration)
OWON Oscilloscope and true RMS DMM
Xtant X604
Diamond Audio D7054
JL Audio HD900/5
Phoenix Gold Ti800.4 (2011)
Arc Audio XDi804
Zapco Z-150.6
Soundstream REF4.920



"The Configuration/Setup"
The amplifiers will be powered by a TPS 75amp dc power supply. DC from the supply will then run through a circuit breaker to control power on/off for the whole system, and then off to fused power and ground distribution blocks to supply the amplifiers. For signal, a single pair of rca outputs will be supplied from the P99 with no crossovers or processing applied. These RCA's will plug into an rca "patch panel" where the source inputs are tied to each of the 8 RCA output pairs. This means the same signal is shared to each of the amplifiers being tested. Each amplifier will have it's own pair of RCA cables to supply its signal from the patch panel. All of these cables will be the exact same model and length and impedance will be measured of each to ensure they are in close tolerance. On the output side, each amplifier will output 2 channels (L and R) to a patch panel of binding posts. We will use one pair of speaker wires with banana plugs to "plug in to" the amplifier we wish to use to power the mains.


"The Method"
The source unit will be measured for clipping point and will be kept at a volume point a few notches below to ensure a full, clean signal. All filters and processing will be disengaged. The source volume will not be changed during the listening tests.

All amplifier gains will be set as close as possible to equal output voltage at the speaker terminals. I will aim to leave plenty of amplifier headroom so that the larger amplifiers do not gain a significant advantage over the smaller ones and output is relatively consistent.
The speaker patch panel will be hidden from view, leaving the listener unable to see which device is currently powering the speakers. The assistant will keep a list and assign a number to each amplifier randomly so that the listener has a basis for notes. To change the "source amplifier", the assistant will swap positions on the patch panel.

[captainobvious]

Pics of some of the gear. I've wanted to sample some of these for quite a while. A few others on my coveted list as well but chances of acquiring them are tough-
Mosconi AS series and Phoenix Gold Elite series and the Audison AV/Thesis.

[BigAl205]

I love this idea, thanks for sharing

[Hi-FiDelity]

subbed, this is definitely going to be interesting. I want to see how the REF4.920 and the Ti800.4 stack up against some of the older "audiophile" completion.

[astrochex]

Thanks much for doing this.

I understand the intent and plan is for a blind test but do you have any expectations before you start?

[captainobvious]

I don't have any expectations, nope. Only to learn and hopefully be enlightened a little.

I'm keeping an open mind for sure. I'm hoping to like the smaller class D amps if only for conservation of space, but I guess we'll see how it turns out!

[captainobvious]

We also will have a Phoenix Gold Elite amplifier and a Zuki Eleet for the testing

Update:
I'm in contact with some of the hotels in the King of Prussia, PA area to try to arrange the rental of a meeting room for Saturday February 1st. This will provide a much nicer venue with plenty of space and seating as well as a good central location with easy access to major roads, food etc. If you would like to attend, please respond in the thread and we'll get a list going. IF we have enough people to justify renting out the meeting room, I would ask that people help out with contributing a few bucks toward the rental fee as I've already put out quite a bit for amplifiers, parts, supplies, shipping costs, etc.
I'll be developing the track list, burning discs for each of the participants and creating the testing parameters/procedure as well as making up some scoring sheets for the testers. We will have some excellent amplifiers in the lineup for this and it will be a good chance to demo them on an equal playing field to find the answers for yourselves about sonic differences in amplifiers, topologies, etc. Should be a fun time!

One thing to note regarding the larger room...I may be looking for a volunteer to bring a good set of tower speakers along for the testing. While the Monitor II's I have are very good and capable of more output than a standard recording console set, I won't know what to expect with the larger room size. I'm open to suggestions here.


If you plan to bring a guest, please add them to the list as well. This will be limited as it's going to be difficult to accommodate testing with too large of a group with the time we have. Thanks!

Attendee List:

1. Captainobvious (Steve)
2. Guest of Captainobvious (Mike)
3. ChefHow (Howard)
4. Mic10is (Mic)
5. dgr932 (Dustin)
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[Notloudenuf]

How about this?

[West]

If you were local I'd bring my class A by

[decibelle]

This is gonna be good. Interested to see how this pans out. Wish I could attend, but I'll still be watching eagerly for results from the interwebs.

Also, consider a way to make it a double-blind study if possible. You going full-on scientific method here, or something a little less formal? That way there is no question whatsoever about any bias. Another thing I would be concerned about is that this whole shindig is centered around telling differences in amps (or lack thereof). Most folks I know either believe there are or there are not audible differences in amps, and that preconception may cloud some judgment, especially when we see what the amps are beforehand.

There's just still a lot of room here for accidental bias, you may want to be careful what you make public until the test is through, especially to those who will be taking part. Just some thoughts. Thanks for doing this experiment!