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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Using the power amp of an integrated amp
Using the power amp of an integrated amp
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Old 5th December 2019, 07:54 PM   #11
rayma is online now rayma  United States
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Originally Posted by ulogon View Post
I added a 50kΩ resistor to RCA socket, but since the preamp output impedance is just 1Ω I think that also a lower value should work: do you agree?
Furthermore I'm just wondering how it would sound (related to its musicality) without that resistance, but I'm afraid to take it off because I don't know what could happen...
So, please what could risks be?
What did you exactly mean with "after the control is disconnected"?
Can you post the brand and model of your amplifier? It may be possible to tell whether
there is already a resistor inside. Any value 10k - 100k should work if there isn't.

There could be a preamp output capacitor that would roll off the bass with a too small resistor.
If there is no resistor inside, it's possible the circuit could be perturbed without one in place
of the volume control.
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Old 8th December 2019, 08:45 PM   #12
ulogon is offline ulogon
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Originally Posted by rayma View Post

There could be a preamp output capacitor that would roll off the bass with a too small resistor.
Yep, after your addressing I've learned about that possible issue

Mix and match impedance | PS Audio

However I can confirm it does not seem that case since the sound is good.

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Originally Posted by rayma View Post
just to be sure there's a DC path to ground
As said really I was afraid about the above statement since I'm not an expert...
Thanks!
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Old 8th December 2019, 09:59 PM   #13
rayma is online now rayma  United States
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Originally Posted by ulogon View Post
As said really I was afraid about the above statement since I'm not an expert...
Thanks!
What brand and model is your integrated amplifier?
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Old 8th December 2019, 11:22 PM   #14
Douglas Blake is offline Douglas Blake  Canada
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Quote:
Originally Posted by ulogon View Post
Everyone's buddy Paul ... great guy, but a source of considerable ongoing disinformation about audio and hifi. I catch him out all the time.

Modern amps no longer require precise impedance matching. They use a system called Impedance Bridging that guarantees you can freely connect one device with another.

The source device (pre-amp, tape, CD, etc) will have a low output impedance, 75 ohms is typical. The input of the next device (pre-amp, power amp, etc) will have a high input impedance, 10k ohms is typical. In this way you can be sure that one device can feed another without degradation of the signal.

The signal levels are also standardized. One for professional audio (PLL) and one for consumer audio (CLL) as explained HERE

So it is pretty much mix and match, although there is no gurantee this is continued inside each device.
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Last edited by Douglas Blake; 8th December 2019 at 11:26 PM.
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Old 12th December 2019, 05:49 PM   #15
ulogon is offline ulogon
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Quote:
Originally Posted by rayma View Post
What brand and model is your integrated amplifier?
AMAudio T-90

Features translation (if useful in some way) in attachment.

However during my trials I've replaced the 51k resistor (> good sound) with a 7.5k one and the sound got worse.
Then I've replaced the 7.5k with 2x51k resistor (102k) and the sound is good again, nay improved.


Quote:
Originally Posted by Douglas Blake View Post
Everyone's buddy Paul ... great guy, but a source of considerable ongoing disinformation about audio and hifi. I catch him out all the time.

Modern amps no longer require precise impedance matching. They use a system called Impedance Bridging that guarantees you can freely connect one device with another.

The source device (pre-amp, tape, CD, etc) will have a low output impedance, 75 ohms is typical. The input of the next device (pre-amp, power amp, etc) will have a high input impedance, 10k ohms is typical. In this way you can be sure that one device can feed another without degradation of the signal.

The signal levels are also standardized. One for professional audio (PLL) and one for consumer audio (CLL) as explained HERE

So it is pretty much mix and match, although there is no gurantee this is continued inside each device.
Thanks for your appreciated reply, I'm just learning more and more, but please note that the topic is related to a power amp stage of an integrated amplifier and I do not know if that is just matter.
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Old 12th December 2019, 06:39 PM   #16
rayma is online now rayma  United States
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Quote:
Originally Posted by ulogon View Post
I've replaced the 51k resistor (> good sound) with a 7.5k one and the sound got worse.
Then I've replaced the 7.5k with 2x51k resistor (102k) and the sound is good again, nay improved.
Then try a 100k pot, but keep it close to the amp to avoid hf loss.
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Old 12th December 2019, 07:54 PM   #17
ulogon is offline ulogon
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Originally Posted by rayma View Post
keep it close to the amp to avoid hf loss.
Ok, thank you!
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