Hai Akshay,
What Op-Amp chips do you suggest for replacement.
N.Murali
OPA2107 looks like the best dual opamp option, for now
Hai Akshay,
What Op-Amp chips do you suggest for replacement.
N.Murali
1. Instead of the 47uF/16 on 2107's PS & Gnd, go 220uF/16.
2. For biasing, would suggest to go easy & more like 12/6 = 2k at starting. If you get good results, move to 1.8k. 1.5k only if you put a heatsink on top of 2107 as the opamp will get quite hot.
Cheers!
Prices of some products are very high-
say stereo jack here for Rs.70 & MX in local around Rs.15 to 20
LUMBERG|1503 09|SOCKET, 3.5MM JACK, R/A, STEREO | Farnell India
The MX local jacks absolutely suck, the contacts wear out soon and don't retain their shape.
It does cost a dollar and a half - I think it's a reasonable cost, actually, if you want the thing to last longer than a few months.
But the TRUE results come when you take adequate care to ensure PSU is stiff, decoupled with MKP.
When I was doing the Class-A biasing test runs, I had put in a trimmer and started with only 3mA and kept increasing to 8.5mA to see the results. Above, 7mA, only if you heatsink the chip esp for usage in our high temperatures ambient climatic conditions.
And guess who guided me towards zeroing-in on the right sort of value? Grand ole Nelson Pass!
Of course, I used a +/- 15V supply and later a +/- 18V 120VA toroidal.
When I opted for the 18V PSU, I discarded the 2107 and went for the 627BP on browndog, heat-sinked, with at 8mA bias.
Astounding results!
And guess who guided me towards zeroing-in on the right sort of value? Grand ole Nelson Pass!
Of course, I used a +/- 15V supply and later a +/- 18V 120VA toroidal.
When I opted for the 18V PSU, I discarded the 2107 and went for the 627BP on browndog, heat-sinked, with at 8mA bias.
Astounding results!
You might be interested to know that a notable preamp uses a 300VA transformer (I forget the name but it will come back to me), and has a standing current draw of over 150mA, which is as much as a NAD 355 power amplifier section. Nelson Pass's BOSOZ preamp draws around 300mA at idle, and the minimum recommended transformer is 100VA.
has a standing current draw of over 150mA, which is as much as a NAD 355 power amplifier section. Nelson Pass's BOSOZ preamp draws around 300mA at idle, and the minimum recommended transformer is 100VA.
I noticed a big improvement when I went from 15VA to 30VA for an I/V stage that draws less than a watt (all opamps, mind you).
@ akshayjha : When it comes to PSU, I always believe in overkill. The 120VA was only driving DAC chips & buffer. I/V was internally done within the DAC chipset. Buffer was a single Dual opamp.
120VA was +/- 24V, regulated down to +/- 18V for Buffer Opamp while further regulated down to +/- 12V for the DAC chips analog feed. A separate 30VA +/- 8V Raw and +/- 5V after regulation fed digital sections of the DAC circuit and input sections.