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DIY preamp

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
 
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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.
 

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
 

captrajesh

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the initial session was with Capt Rajesh.
Sorry for posting late. I wanted to write after the channel imbalance issues are sorted out but gotten busy with domestic issues and quite a bit of travel on official work and forgot about it. I got reminded about it after learning from Jls001 about his build.

I auditioned this preamp at Hydrovac's place which I consider the reference system of what a DIY setup can do. He replaced his DIY preamp with the DD preamp, rest of the setup being same.

We listened to several tracks from some Tamil Movie tracks to some classic rock. The preamp stood out by presenting a fantastic sound; great sound stage with instruments well etched in the 3D space. Not an aorta of hiss or hum.

Of all the tracks, I vividly remember the Sade tracks. It's like some invisible veil has been lifted. Trust me, it's worth it's weight in Gold and give the run-of-the-mill commercial preamps a complex. I'm definitely building one for sure.

I wholeheartedly congratulate Aniket on the great design and Sachin for bringing it up on the forum.
 
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jls001

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Today I received the almost fully built PAM12 line level preamp cum headphone amp from Sachin. Since I'm not using my old DCB1, I removed the DCB1 board and temporarily plonked the PAM12 into the DCB1 cabinet. The R-Core transformer is 15-0-15V, rated at 1A. Connected audio inputs, outputs and output of transformer secondary and I was listening to music in less than 2 hours.

I have played it for about 4 hours so far and it already sounds amazing.

For those interested, it beats my favourite buffer the Kuartlotron by a wide margin. B1 < DCB1 clone < hotrodded Salas DCB1 biased to crazy current < Kuartlotron = JC2 clone < PAM12 has been the performance hierarchy in my setup.

Stand out features:
1/ clean, neutral sounding, if a bit leaning on the colder side of the spectrum.

2/ imaging is very specific. There's no vagueness. It dehomogenises the instruments and voices that make up the music. One can follow each strand of the music without struggling. Image width is a bit wider than that of the K buffer. Front to back separation also seems superior to the K, and this will become more apparent as the preamp gains more hours.

3/ it has unfettered, unrestrained, almost playful dynamic swing. Attack is swift. Makes the music very lively. This aspect makes it very different from any buffer or pre I have owned/built and I love it.

4/ mids are a wee bit leaner than the K buffer. The highs were initially strident on some passages but after remembering that I'm listening with fresh Italian speaker cable, a fresh Siltech IC from pre to power (PeeCeeBee v4), and fresh DIYed power cord on the power amp, I reverted to previous cables and the highs immediately improved. By the third hour it became clear that it was going to surpass the K buffer. Resolution and micro dynamics already beat the K.

5/ bass has started sounding good. I'm certain the bass definition and texture will improve with more hours. Weight is hefty. I hear lots of promise in the bass.

The sound is engaging and musical. Aniket has designed one hell of a preamp. Congratulations!!!! I eagerly await your upcoming phono preamp.
 
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