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DIY preamp

saikatbiswas82

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I have gone through the whole thread and found that no-one has asked the most important question. Correct me if I've missed anything.

What are the input and output impedance of this preamp?
 
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haisaikat

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I have gone through the whole thread and found that no-one has asked the most important question. Correct me if I've missed anything.

What are the input and output impedance of this preamp?
From another thread where this was earlier discussed this information was provided

Hi @haisaikat specifications as follow

- Discrete stereo preamp/headphone amp
- Input Impedance: 100kOhms
- max gain: 8dB
- max voltage output: 11V rms
- SNR: 115dB
- THD: <0.002% 20-20000Hz, Vo=5V rms
- Transformer required: 18-0-18V AC, 50VA
- Frequency response: 1-150000Hz(-3dB)
He has also designed a Class AB power amp for 75W and 120W version. @Aniket can provide you more details on this.

Regards
Sachin
 

hydrovac

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Hmm... I guessed so, just wanted to share... nothing negative here.

To clear this, Aniketh messaged me saying that actually a 100K linear was to be installed in the first place, but due to non availability of the same couldn't do... and forgot to inform me about it.
Very soon he will be sending me an Alps Japan, 100K linear... isn't that great?

Will update after replacing the pot.

...

Replaced the pot... the channel imbalance gone, and got more sweep on the pot.
Thanks Aniket!

...
 

MaSh

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Lovely build log and a beautiful setup you have.

Recently added a Peeceebee V4 power amp to my setup and really amazed with it. Might add this preamp to it.

MaSh
 

sachu888

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Lovely build log and a beautiful setup you have.

Recently added a Peeceebee V4 power amp to my setup and really amazed with it. Might add this preamp to it.

MaSh
You won't be disappointed.

Regards
Sachin
 

tcpip

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100 ohms approx is what Aniket told me
100 Ohm output impedance for a preamp which is so high current that it can drive 4 Ohm headphones, as stated in an earlier post? Are you sure?

Anything which can drive a 4 Ohm load cleanly is a tiny power amplifier. I can't understand how such a circuit can have 100 Ohm Zout.
 
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spirovious

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100 Ohm output impedance for a preamp which is so high current that it can drive 4 Ohm headphones, as stated in an earlier post? Are you sure?

Anything which can drive a 4 Ohm load cleanly is a tiny power amplifier. I can't understand how such a circuit can have 100 Ohm Zout.
This pre is headphone amp too. So must be the reason. Usually headphone out has different output arrangement of parts than preout on same board. When l compared headphone out of AVR with its preout, obviously headphone louder than preout. May Aniket can explain better.
 
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Aniket

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100 Ohm output impedance for a preamp which is so high current that it can drive 4 Ohm headphones, as stated in an earlier post? Are you sure?

Anything which can drive a 4 Ohm load cleanly is a tiny power amplifier. I can't understand how such a circuit can have 100 Ohm Zout.

100 ohm output impedance is when used as a preamp, but with the headphones connected output impedance is less than 0.1ohm.
 

tcpip

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100 ohm output impedance is when used as a preamp, but with the headphones connected output impedance is less than 0.1ohm.
Understood. Thanks.

Just a question which I've often wondered about: what would happen if the preamp output had retained the low Zout? Do you add some deliberate Zout for the preamp output to protect the output circuit in case of a short? Does distortion or other non-linearity rise if Zout is kept extremely low?
 

Aniket

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Understood. Thanks.

Just a question which I've often wondered about: what would happen if the preamp output had retained the low Zout? Do you add some deliberate Zout for the preamp output to protect the output circuit in case of a short? Does distortion or other non-linearity rise if Zout is kept extremely low?
Even if the preamp output is fed with the direct low Z out, it wont affect anything, as then the load on the preamp would be higher Z, normally greater than 10kohm, or the input impedance of the amp. there wont be any sonic or performance difference.

Regards,
Aniket
 
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