• Hello and Welcome to HiFiVision.com - an online community for the home entertainment and tech enthusiasts!

    If you would like to ask a question, participate in a discussion and view attachments please Register yourself.

Planning a discrete Op-Amp buffer for my pre-amp

Hari Iyer

Well-Known Member
Joined
Feb 8, 2010
Messages
2,578
Likes
1,434
Points
113
Location
Mumbai
#1
Currently my pre-amp just has the Phono pre-amp and other line inputs (CD/Tape Deck) are just switched in the pre-amp without any amplification. I am planning to built a discrete op-amp buffer similar to the Marantz HDAM cicuit but with different components. I am mighty impressed by this circuit in the blue-ray player and think it can also benefit in the pre-amp. I shall built only 3 boards currently. Earlier i had built a class A pre-amp and also the DCB1 but was not impressed by them. I believe the DCB1 JFET was duplicate and hence did not benefit.
 
SPONSORED ADS

SPONSORED ADS

sachu888

Well-Known Member
Joined
May 8, 2010
Messages
2,611
Likes
1,553
Points
113
Location
Gwalior,Nashik
#2
From where did you by the Toshiba Jfets? There are mostly fake Jfets available on eBay. There is only one genuine seller fetaudio as far as I know for 2sk170.

Regards
Sachin
 

Hari Iyer

Well-Known Member
Joined
Feb 8, 2010
Messages
2,578
Likes
1,434
Points
113
Location
Mumbai
#6
jls001, unless i can borrow a DCB1 for a couple of days and can compare the sonic benefit from my current setup, i cannot say about this. I also have other smd jfets with me but they are having higher capacitance tha.n the 170K.

The reason i am planning the hdam way is i can for sure see the sonic benefits of that circuitry which i could not with the DCB1. Also i had designed a tube buffer ckt, but did not built them because i was not too sure about the benefits from them hence abandon the project.
 

Hari Iyer

Well-Known Member
Joined
Feb 8, 2010
Messages
2,578
Likes
1,434
Points
113
Location
Mumbai
#8
spirovious, thats the reason i built them but could not find benefit. For me the sound stage collapsed and the HF response was less. Honestly, this was about 1 year ago, before i went with all the other mods in my amp, IC, speaker cables etc. May be if i do this now, i can / may get benefit. Maybe i should try and hook them up again on this long weekend.

Anybody in the forum have a spare dcb1 pcb? Mine was point to point wired.
 

spirovious

Well-Known Member
Joined
Apr 10, 2008
Messages
11,937
Likes
2,321
Points
113
Location
Mumbai
#10
spirovious, thats the reason i built them but could not find benefit. For me the sound stage collapsed and the HF response was less. Honestly, this was about 1 year ago, before i went with all the other mods in my amp, IC, speaker cables etc. May be if i do this now, i can / may get benefit. Maybe i should try and hook them up again on this long weekend.

Anybody in the forum have a spare dcb1 pcb? Mine was point to point wired.
Which psu was used?l tried one with group buy and got new Oms one too.New one built with Nichicon and Tdk caps,it sounds better than Samvaha cap psu.But only looses in headroom as nichicon used are 2200uf and not 4700uf.
Also if jfets are not matched properly,they produce some unwanted color.
 
SPONSORED ADS

Hari Iyer

Well-Known Member
Joined
Feb 8, 2010
Messages
2,578
Likes
1,434
Points
113
Location
Mumbai
#11
Which psu was used?l tried one with group buy and got new Oms one too.New one built with Nichicon and Tdk caps,it sounds better than Samvaha cap psu.But only looses in headroom as nichicon used are 2200uf and not 4700uf.
Also if jfets are not matched properly,they produce some unwanted color.
I used a parallel class A power supply based on LM317 & LM337 and power transistors for current regulation which i continue to use for my Phono pre-amp. They are quite good and i have managed to keep the ripple around 100mV. My Phono pre-amp is dead silent with this PSU implementation. I have used a total of 8000uF in the PSU before regulation and around 3300uF in the final output stage. I have also used inductors for reducing ripple voltage.

This time unless i can get a demo of the DCB1 in my setup and i can see a marked improvement, i may not want to spend money on this.
 

jls001

Moderator
Staff member
Joined
Feb 9, 2010
Messages
5,684
Likes
3,398
Points
113
Location
Mumbai
#12
Interesting read about discrete opamps with a special two or three capacitor compensation that results in a very high open loop gain and very high SNR (much higher than the usual monolithic opamps), and 12 dB/octave roll off (against the usual 6).
 
SPONSORED ADS

Top