|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
173.189.217.4
As predicted previously by others, I find I can not change between two amps quick enough for proper A/B testing even though I have a switch that lets me select one or the other amp to go to the same set of speakers. It still takes about 20 seconds and I have to get up from my listening position to do it and turn off one amp and turn on the other.
I would instead like to be able to leave both amps on, balance out the volume levels, and then switch amps from my listening position.
I have enough selector switches to do it, but my problem is keeping a load on the amp that is not switched in to the speakers.
I did a little searching on the net and found one suggestion to put a 150 ohm/5w resistor across the terminals of each amp so that they have a load when not switched in.
Does anyone have any experience with setting this up? Does the above method work or do you know of a better method?
Thanks
Follow Ups:
First of all, I want to say thanks to all who offered advice, I appreciate all the help.
To eliminate as many extraneous influences on the sound as possible, I have the output of my cd player going directly into two different amps (71A and 845 at the moment) with no preamp. The amps feed into a two position switch that feeds directly into my speakers.
Both amps are on full time so there is no warm up difference between them, and each amp has a pair of 10 ohm/30 watt resistors across the output terminals so that there is always a load on the amp during switching.
So far so good. I can switch between amps in a split second right from my listening position.
And now I can hear differences.... but boy are they ever subtle with these two amps. As soon as I get the FS-030 outputs back in the 300B I will put it in place of the 71A and see how it does against the 845. I also have a parallel feed Gordon Rankin design 45 "bugle" amp that I built from an article Gordon published in Sound Practices some time back. I will put it in after I test the others.
I know there are several folks that believe you have too listen to an amp for a several weeks to get an imprint before you can compare it to another, and I may try that method too once I have finished the short term testing. For my use though, I sort of figure if I can't here a major difference between the amps in short term testing the difference is probably too subtle to really matter to me. I will get used to the little bit of difference after listening to either amp for a while.
If I find any interesting results as I continue with the testing I will report back.
I have some 10 ohm 30 watt resistors that I can tie across the outputs of each amp. It would then only take a split second to switch amps with the switch I will use, and the amp that wasn't playing would have a 10 ohm load on it. Is that split second likely to be a problem?
I already tried putting one across the outputs of the 845 amp, and the only difference I could hear was a little less volume. I can correct for that at the line stage.
Is this likely to effect the sound of the amps? Have I missed anything else?
Edits: 10/23/14
Some McIntosh preamps (C26 for example) allow you to combine L & R and send to the L output or R output. Thus one amp on L and different one on R and you can AB them pretty fast. Then all you have to account for are effects of speaker placement, relative sensitivity of the amps, etc...
Hi,
IMHO, if the differences are so small you need quick AB testing to make a judgement, than the difference are not substantial enough to bother.
If an improvement is worthwhile you hear it instantly. No matter what type of music you play and for how long.
My 2 cents.
NC
The problem as I see it so far is short term memory vs long term memory, and I am not sure yet which is most critical as there have been champions of both methods. Going to try both if I can get set up for quick switching, but it is tough to do for tube amps because of the loading requirement for the amp that isn't playing. I need to figure out how to have that amp switched to a dummy load.
Edits: 10/23/14
Before getting too much involved with A/B testing, why don't you try this?
http://www.audiocheck.net/blindtests_index.php
ecc230
I would still need a way to switch between the sources........
Russound makes a switch box.
I have enough stuff to make my own switching box for a whole lot less money, I just need to know how to keep a load on the amp that isn't playing music.
Hi!
In my experience such a set up is not needed to compare amps. While many claim that you need such an AB testing set up to compare two pieces of equipment, I find it totally inadequate to assess the sound of amps.
I believe that our short term memory is not very capable to compare sounds. The long term memory is much better for that. In such a set up when you are switching rapidly between amps, the sound impression is only stored in the short term memory.
I find it much easer in a more relaxed set up. I usually have no problem to judge between amps even if I listen to them on different days. Of course only if the difference is significant and the system is capable to reproduce the differences.
I am aware that this is mostly contrary to common opinion. This is all just my subjective experience and I don'r expect anybody to take it for granted
best regards
Thomas
It would be better to get the basic circuit qualification measurements together first.
A computer based measurement system would let him look at distortion/harmonics , phase, bandwidth, etc.
Software is not expensive or can be downloaded free.
If there is a significant difference in the measurements of the two amps, then do some A/B listening tests.
Measurements don't tell everything, but can give helpful clues to the builder.
I think someone else suggested longer term listening for comparison too, it just seems counter intuitive. That probably means it works. I will have to give it a try along with the short term testing.
Thanks
For long term comparisons, one first has to be intimately familiar with system "A" before hand.
A lot of people change things about their systems so often that they are not that familiar with what they've got.
Whenever I make a change in my system I find myself listening to the system, and not the music, for at least the first couple of weeks or so.
I recommend that you start with a system that you haven't made any changes to in a long time, a system that you really understand. A system that you are intimately familiar with in terms of how it sounds.
Now make the change. In this case change to the "new" amplifier.
Don't be fooled by first impressions. Don't switch back and forth.
Listen to the new amp and get familiar with the sound of your system with the new amp in place. Leave the new amp in place until long after you stop "listening to the system" and are relaxed and just listening to the music. 2 or 3 weeks or more.
Now that you are really familiar with the "new" amp, switch back to the "old" amp.
I believe you are now in a position to make valid comparisons between how your system sounds with amp "A" vs. amp "B".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Not quite sure I understand what you are suggesting. Do you mean listen to the old amp for 2 or 3 weeks, then listen to the new amp for 2 or 3 weeks and then start switching back and forth between them to listen for differences?
I mean listen to the old amp long enough to get totally familiar with it (if you haven't already) switch to the new amp.
Listen to the new amp long enough to get totally familiar with it.
Then switch back to the old amp and you should be able to tell which one you like the best.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Do you really think the impression of the old amp will last that long? It seems like too long a time to remember it.
Hi!
I know people who can memorise sound impressions for months or even a year.
I see two possibilities for you:
1: Since you are not hearing differences, stop bothering and just enjoy the music.
2: If you want to be able to hear differences, maybe get someone who has some extensive listening experience and let him help you how to listen. Or of he also doesn't hear a difference in your set up. Try to find out why and what to change to make things audible.
As NickelCore said, differences should be very easily audible between vastly different amps. Maybe there is a bottleneck in the system which prevents that. Then any kind of A/B switching set up will not help either. I find it much easier to spot differences by casual listening. As soon as you switch to 'technical' listening mode, it gets very difficult
Thomas
.
Have Fun and Enjoy the Music
"Still Working the Problem"
I think that will depend on just how intimately familiar you are with the sound of your system with the old amp.
And remember, at the end of the 2 to 3 weeks with the new and you switch back to the old amp.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Sorta +1 toward Tre's view. For me, it takes a little longer, like maybe 3-4 weeks. You just live your daily life with a rig for basically a month, flip stuff for another month, and flip back. At each flip you learn things that you didn't know (hearing education, maybe?). That way, there's no "critical listening" etc. All the "life" variables seem to sort for me to have a solid position on something in that time.
And yeah, of-course, the short-term thing when it works in your life. Sometimes if there's a big block of time, I'll drag-out every odd speaker I have and spin them around with the same set of material. That, too, is interesting and educational, but in a different way and doesn't serve the same way as the long-term thing does.
I could be fooling myself, too, but that's what seems to help steady the rudder here.
Well, I promised myself I would try both ways of A/B ing, the long and the short, so we'll see what happens.
This is what I tried, put both speakers side by side and mono one speaker to one amp and the other speaker to the other amp, do what you must if your amp needs protection for the unconnected speaker output. Now figure out the quickest way to swap sound from speaker to speaker ... balance control, volume up one volume down other, power on one power off other, you may prefer 2 channel mono music for those tests, (you can convert it with software) or swap the input RCA over, whatever you can think of, even better if you can achieve it while still sitting in your seat.
I can see that would work, but I found another way that's ok too. See post at top of thread.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: