measuring the output of a preamp

[opimax]

I believe I have narrowed down my lack of bass to my Sony ES receiver/pre-amp. I would like to measure the freq response of the pre-amp. It is suppose to be flat from at least 10 to 20K :applaud:

How can this be done?

Is it possible to be done w/o shipping this beast?:banghead:

Thanks

Mark

[hjames]

I believe I have narrowed down my lack of bass to my Sony ES receiver/pre-amp. I would like to measure the freq response of the pre-amp. It is suppose to be flat from at least 10 to 20K :applaud:

How can this be done?

Is it possible to be done w/o shipping this beast?:banghead:

Thanks

Mark

When in doubt, simplify ...

I don't have the link handy right now but there was a website referenced here (last summer I think) that offered a (free) download-and-burn test CD with various frequency test bands. You can burn that and use it as a signal source to test upper and lower limits of the sony receiver.

Haul a couple pairs of your small speakers to the stereo, hook them up to the Sony mains out, see if it sounds widerange ...

As an alternate, hook your 250tis up in place of the test speakers directly to the sony MAINS out, go through the test disc again, test highs and lows.

If needed, keep adding pieces of your system back in and find out when you don't have bass anymore.

If that works, tie the "test speakers" to one of your external amps, and tie that directly to the mains Preamp out of the Sony - see if you still have widerange sound.

[BMWCCA]

Maybe it's 'cause your woofers are diametrically challenged by something around one-inch! ;)

Just kidding. Happy Holidays.

[hjames]

I found a link for the download and burn-it-yourself RealTraps Test Tone CD (http://www.realtraps.com/test-cd.htm)

Seems its lower freqs only - but very well defined ones.

You can use this as a signal source with the testing I already described below ...

============================

TRACK CONTENTS
(All tracks are recorded at -1 dB.)
Track 1: 10-19 Hz in 1 Hz increments.
Track 2: 20-29 Hz in 1 Hz increments.
Track 3: 30-39 Hz in 1 Hz increments.
Track 4: 40-49 Hz in 1 Hz increments.
...
Track 29: 290-300 Hz in 1 Hz increments.
Track 30: Wide band pink noise Wave file, 15 seconds, for setting the level to about 70 dB for the subsequent tests
============================


Use those test tones to trace your bass levels - if you need more details,
you can even buy a Tandy/Radio Shack Sound Pressure Level (SPL) meter,
set it on a tripod and do very specific tests at specific frequencies.
With the SPL you can make actual measurements and compare the system response
for around $50-75 or so ...

Pretty sure Ian or one of the others posted VERY specific procedures for doing that here a while back ...

But the important thing for you to remember is to START SIMPLE.
Use the CD Player and Receiver only, then add in piece by piece until you loose bass ...

And if you are using Bass management software in the Sony to feed bass to just the Velodyne,
turn the software to OFF (at least, at first).



I believe I have narrowed down my lack of bass to my Sony ES receiver/pre-amp. I would like to measure the freq response of the pre-amp. It is suppose to be flat from at least 10 to 20K :applaud:

How can this be done?

Is it possible to be done w/o shipping this beast?:banghead:

Thanks

Mark

[JBL 4645]

How would I tackle it, hmm I’d take the preamp and mate it with test frequency sound generator something that can be download for free say one of few REW at the home theatre shack or TrueRTA version 1. Then send a few frequency sweeps though it and then look at the data to see just how flat it is.

I’d test my system out that way if I had several DEQ2496 to correct a few of the dips and peaks.

Test the system directly not in room response that will have more dips and peaks than you can handle, test the unit out first, you might need a few leads to patch it up with.

Send a lead from the computer audio output to the preamp input.

Send an RCA jack lead from the output preamp to the computer input then test each channel one at time.
look for even range even with spot frequencies the levels should be even, should be, if few are out of place apply some EQ to those bands, chances are you might need a DEQ2496 because most EQ only have 10 or 12 bands.

Oh, I almost forget the DEQ2496 won’t address frequencies below 20Hz.

If you what to test it via speakers make sure make sure that each speaker is in the same spot or position because room modes will send some portions of the frequencies in different directions at different SPL db levels so make sure that you test the first loudspeaker out in a fixed position.

Mark its position with tape around it a square around the speaker, then place the other speaker in that spot after you’ve tested the first speaker.

Make notes of the SPL db level on paper the dips and peaks and yes I think you what test it directly first because some frequencies will be in (null) once they become airborne in the room.


:happyh::presents::tree:

[hjames]

I read "START SIMPLE" as an indication that there's a learning curve to surmount
before computers and software enter the mix.

:scoot:

Just basic troubleshooting techniques ...
Assuming nothing, test each piece.
Start simple, and add parts until the problem presents itself ...



I’d test my system out that way if I had several DEQ2496 to correct a few of the dips and peaks.

Forget the behringers and that kind of ... stuff.

Opimax has quality low-noise gear in the system
Peraux, Adcom, etc
250tis and B460 ...
he's not trying to sweep the room,
just check his preamp, amps and 250tis ..

[grumpy]

Difficult to get much simpler than checking in vs. out of just the unit in question... :)

but it would require an investment in time (how to setup, how to know what to expect,
what to do when it doesn't it measure that way, ....) and some very basic test equipment
that often now means a computer and a sound card (for line-level stuff)... add a $50 mic
and a pre and you're dangerous.

Frankly, I'd be surprised if the pre-amp was a problem. Try some headphones.

[yggdrasil]

Download RMAA: http://audio.rightmark.org/index_new.shtml

Run a loopback test of your soundcard.

Run a test with your preamp in the loop.

Compare the results.

[opimax]

What I did to test:

Next the main rack I put a adcom pre amp gtp 400, adcom gfa 555 and a seperate CD player. I swapped out connections 1 piece at a time so could keep it simple. anything connected to the Sony has less bass.

I have tried on a 2nd pair of 250 and the same basic results. The I was tld the the Sony with its digital amp might sound different but not this much and I am using the pre outs so that shouldn't be it.

I have more bass with the 2 channel set up thanbI do with the Sony and 2 subs unless I turn them really up and it is boomy and not house shaking.

Still confused
Mark

[opimax]

I also ran the through the Perreauxs to verify that they weren't the issue and actually they sound pretty nice.

I don't have a dedicated sound card, old laptops that sit on a port replicator w/digital coax out to the Sony or mini din to rca to the amp on the newer laptop

Heather what do you have? as far as a sound card?

My equipment (1 more time :) )
Sony str-da9000es receiver
pre out for mains to 2 Perreaux 6000b to "passive" biamp of 250ti CC using European (TIBQ) CC XO w/US drivers but 14-3 for the 14-1
Center is pre out to Perreaux 3000b and 2 18Ti "stacked" sideways(mono signal run stereo for the 2 speakers)
The 4 120tis are surround run by the bulit in amps of the Sony
The subs are pre out to Velodyne SMS-1 split to B460 run by bridged Adcom gfa-555 and a Velodyne SPL1200r. The sub XO is used is from the Sony and the rest are set as high as possible or defeated

When comparing the different sound quality I compared the the Sony in 2 channel mode and the Adcom pre only does 2 channel.

Tha Adcom set up has more bass then the Sony set up w/2 channel and subs unless really crank up the subs but again boom not house shaking.

I have not tried using subs w/the Adcom set up to verify from another direction, hoping I can bust out the windows if I do (not really) after Xmas

I will admit my wiring needs attention but that was ruled out when swapping connections.

Of course I want the easy way out, borrow somebodies machine which plugs into the RCA outs and just state what it does 10-100KHZ or a graph would be ok...Sounds like the sound card test at some point.

Any other suggestions? At one point Dino was hoping to get Don M to come over to try some things but that hasn't worked out. And a Steve V was hoping to make it but that didn't wok out either.

[hjames]

I also ran the through the Perreauxs to verify that they weren't the issue and actually they sound pretty nice.

I don't have a dedicated sound card, old laptops that sit on a port replicator w/digital coax out to the Sony or mini din to rca to the amp on the newer laptop

Heather what do you have? as far as a sound card?

I have a powerMAC G4 dual 1.25gHz - OSX 10.5.6 - doesn't do winders :)

I have an old Intel Pentium 4 2.4gHz tower with mostly unknown hardware in it - I loaded Win XP Pro last year - I only use that to dupe SATA HDDs for my TIVO (really!) - not sure it even has a soundBlaster or anything in it ... probably just the stock onboard intel chip sound stuff ...

So, you tried with the adcom preamp and the perauxs -
and while its better its not a huge jump in bass over the sony ... correcto?

It also may be a problem with those 250tis - everyone swears they should have great bass,
but if they don't, either the crossovers are faulty, the crossovers are wired wrong, or the drivers are connected wrong.

[grumpy]

I have a powerMAC G4 dual 1.25gHz - doesn't do winders :)

Old version of FuzzMeasure (2.0.11)?
http://www.supermegaultragroovy.com/downloads/FuzzMeasure/FuzzMeasure_1629.tbz

Latest version 3.1.1 requires 10.5/Leopard

http://www.supermegaultragroovy.com/products/FuzzMeasure/gs/index.html

... regardless, full-use is trial-period only, IIRC.