No NFB line amp (GainWire mk2)

[MiiB]

Joachim you're at tease too.. anyway I calculated he Riaa for a gain of 61dB and a tolerance of +/-0.2 dB

 

[Joachim Gerhard]

God enough for Rock and Roll.

 

[MiiB]

actually it's more like +/- 0.1 dB, but i doubt we can mak the components that exact anyway

 

[dadod]

actually it's more like +/- 0.1 dB, but i doubt we can mak the components that exact anyway

So, are you going to show the circuit?

 

[MiiB]

Sorry I can't show, as it belongs to Sergio, I and Joachim are just birth helpers... sorry for polluting your fine thread. I do admire your skills.

 

[dadod]

Sorry I can't show, as it belongs to Sergio, I and Joachim are just birth helpers... sorry for polluting your fine thread. I do admire your skills.

Oh that's pity, I am very interested in good riaa preamp, specialy if it use novelty circuit.

 

[smms73]

I can send you a decent MC Cartridge.
You need it.

Thanks very much for your kind offer, If you lend me one of your MC head would be super, in less than a month my first son will born, and I feel I must save for any eventuality.

 

[smms73]

Oh that's pity, I am very interested in good riaa preamp, specialy if it use novelty circuit.

I think I can get you one finish pcb.

 

[dadod]

I think I can get you one finish pcb.

Thanks a lot, does the schematic is coming with?

 

[smms73]

 

[padamiecki]

I can send you a decent MC Cartridge.
You need it.

Hi Joachim
You can send one for me, I need it too

 

[dadod]

Here is corrected layout with thermaly connect Q13/Q15 and Q14/Q16. I hope I did not make mistakes, but is someone has a time to check.
BR Damir

 

[RCruz]

Ola Sergio

Another special riaa... that is my cup of tea..... please post the schematic..... Does it use any servo to control DC offset ?

 

[cast]

Current Audio Signal Transmission

Current Audio Signal Transmission

 

[dadod]

Here is corrected layout with thermaly connect Q13/Q15 and Q14/Q16. I hope I did not make mistakes, but is someone has a time to check.
BR Damir

Prototype board ready. I have bought 100 peaces of ONSEMI BC550C/560C and now I have to match them and I hope I've got enough of them.
BR Damir

 

[dadod]

This is proto board used for testing.

 

[dadod]

I gave up of using ODNF in this pre amp. Now it is going to have two possibility, NGFB, and CFA, and it is set by one jumper, J2 on is NGFB and J1 on is CFA operation.
ODNF is not easy to adjust, and CFA gives the same very low distortion. Now I can choose between those two operation and could compare the sound quality.
As the switch between NGFB and CFA shows different DC offset, DC servo was added.
Simulated THD:
NGFB output 4.5 Vpp
-------------line out phone 300 ohm phone 32 ohm
THD20k 10 ppm 14 ppm 0.01%
THD1k 8 ppm 12 ppm 0.01%

CFA output 4.5 Vpp
THD20k 0.05 ppm 0.15 ppm 2.55 ppm
THD1k 0.00 ppm 0.03 ppm 0.71 ppm

Output simulated level is more then enough and in more cases lower level is going to be used and with much lower distortion(NGFB).
I decided to make one PCB for dual mono with shunt regulator included. It needs a transformer and input selector + volume control to get complete line and phone preamplifier.
BR Damir

 

[Krisfr]

Prototype board ready. I have bought 100 peaces of ONSEMI BC550C/560C and now I have to match them and I hope I've got enough of them.
BR Damir

I got 300 each, but they are from mouser - Fairchild....

 

[mcd99]

I got 300 each, but they are from mouser - Fairchild....

Quick question.

Do you rate Fairchild devices above the OnSemi equivalent? I've always thought the opposite.

 

[Krisfr]

Quick question.

Do you rate Fairchild devices above the OnSemi equivalent? I've always thought the opposite.

Oh no, I just got some BC550 and 560 from mouser, I did not know that there was a big difference between Fairchild and On Semi... maybe I need to get some from On Semi instead... Mine read BC550CBU... Is that GOOD or BAD?

The On Semi are 10 cents and the Fairchild are 6 cents... in hundreds... so maybe I can get some more