No bass with SI T-amp. Why ? - Page 2 - diyAudio
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Old 16th April 2005, 12:16 AM   #11
BWRX is offline BWRX  United States
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i recently did some frequency response testing as well. i obtained results similar to panomaniac.

the data and plots are in here. download the freq response excel spreadsheet to check them out. my testing shows that the recasing and a much better power supply improve bass response and smooth out the higher frequencies. for reference, the stock t-amp was tested with a dc bench supply at 12V. also, disregard the 8 ohm results unless you want to know the frequency response at 0.125W... those were tested at the wrong output voltage and i only realized that after i had taken the data.
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Old 16th April 2005, 01:27 AM   #12
Pano is offline Pano  United States
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Great stuff! Your 8 ohm response chart shows the high end going way up. Is that what we should disregard?

As far as the high THD at the high end, Tripath claim that different measuring techniques are needed for switching amps. That must be the case, as the amp certainly does not sound as bad as the THD chart might indicate.

Thanks for the good work. Nice to know that just a better power supply helps.
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Old 16th April 2005, 03:24 AM   #13
BWRX is offline BWRX  United States
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Quote:
Originally posted by panomaniac
Your 8 ohm response chart shows the high end going way up. Is that what we should disregard?
it's just that i took the 8 ohm measurements referenced to 0dBV at 1kHz which is only 1/8 W output power. i should've taken measurements referenced to 9dBV at 1kHz into 8 ohms which is 1W output power. i'll update that when i get a chance. i'm still working on getting access to equipment to see the switching spectrum.
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Old 18th April 2005, 01:02 AM   #14
lohk is offline lohk  Europe
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Did you check your polarities? My SI had one output wired out of phase. That can cause no bass at all because of cancellation. The building quality of these items is a bit questionable.
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Old 18th April 2005, 06:56 AM   #15
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Yes, it was the input cap I was refering to. If there are indeed units around with outputs wired out of phase then that would indeed be a real "bass-killer". Apart from lacking bass also the midrange and localisation would suffer greatly.

Regards

Charles
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Old 18th April 2005, 12:32 PM   #16
irss is offline irss  Lithuania
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"Did you check your polarities? My SI had one output wired out of phase. That can cause no bass at all because of cancellation. The building quality of these items is a bit questionable."


I reversed the speaker cables. Strangely, the sound neither improves nor changes. It remains the same with all speakers' cables configuration - flat/weak bass, annoying highs and mids...
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Old 18th April 2005, 01:41 PM   #17
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Quote:
Originally posted by irss
"Did you check your polarities? My SI had one output wired out of phase. That can cause no bass at all because of cancellation. The building quality of these items is a bit questionable."


I reversed the speaker cables. Strangely, the sound neither improves nor changes. It remains the same with all speakers' cables configuration - flat/weak bass, annoying highs and mids...
Reading your initial post, the problem appears to be the CDP and the SI. If the SI has bass when connected to your PC sound card, it is not the SI itself. The 8 -10k input impedance could be it.
Is it possible your speakers are tieing the grouds together? The sound you describe is close to what you here it the grounds for both channels get connected.
Someone brought a sub for some very expensive speakers over yesterday. It tied the neg. leads to electrical ground. Since it is powered it would make the SI sound like crap.


George
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Old 18th April 2005, 02:01 PM   #18
irss is offline irss  Lithuania
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George, I have connected another amp to my initial CDP. Everything was fine, bass was OK. I tried many combinations and the problem seems to be SI.

The volume on PC souncard can be adjusted, therefore, I suppose increasing the volume on PC souncard improves the bass performance on SI.

damn it...I'm totally lost
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Old 18th April 2005, 02:05 PM   #19
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What if the PLAYER has a problem with your SI ? Does anybody know the input impedance of the SI (are the 8 - 10 k approved ?), that may give a problem together with the CD players output drive capabilities (i.e. too small coupling caps).

Regards

Charles
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Old 20th April 2005, 08:54 AM   #20
irss is offline irss  Lithuania
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Quote:
Originally posted by phase_accurate
What if the PLAYER has a problem with your SI ? Does anybody know the input impedance of the SI (are the 8 - 10 k approved ?), that may give a problem together with the CD players output drive capabilities (i.e. too small coupling caps).

Regards

Charles

Is there a way to fix it?
Would the usage of pre-amp solve the problem? If it did solve the problem, would the usage of pre-amp decrease the quality of sound which goes to SI, therefore decreasing the overall sound quality?
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