Tl074, Opa4134, Lme49740

[ztan]

The balanced to unbalanced converter at the front end of my Perreaux 8000C comes stock with a TL074 quad opamp (only using 2 out of 4 channels) installed.

I decided to try some upgrades to it:

TLE2074 - listed by TI as a significant upgrade to the TL074 - staging was a bit more accurate and bass sharper, but sonically sounded really quite similar to the TL074

When I first installed the OPA4134, it distorted at high preamp volume levels, and the LME49740 distorted at low levels. Fault traced to the Perreaux 1985 method of power supply to the balanced line reciever - dropping +/-112V to 15V using a resistor and Zener. Using the stock resistor, current flow was limited to around 14ma and both the OPA4134 and LME49740 idle at around 20ma. Resistor value was dropped to allow more current flow and problem was solved.

OPA4134 - installed with a DIP-SOIC adapter. Opened out the soundstage and brought in the "laidback Burr Brown sound". Some complain of tubby bass but the bass is really not at all tubby with the Perreaux output stage driving my speakers (11" Focal bass drivers). The real strength here is the timbre of the instruments. My wife (an ex-orchestral musician) came down to the listening room saying that my system was tolerable for the first time ever.

LME49740 - this is a new National low noise opamp release this year and I decided to give it a run. Bass was slightly cleaner than the OPA4134, but trebles verged on sibilant - I suspect many would call this "accurate"

After extended listening, I have left the OPA4134 in. The timbre of the instruments is so much closer to live music in my system than most systems that I have listened to. The LME49740 sounded cleaner initially and more detail was immediately apparent, but the treble was too prominent in my setup.

I guess the next thing will be to try something like the OPA627 or possibly the new OPA827, as I seem to like the Burr Brown sound best.

[sandyK]

I found exactly the same with the dual versions of those I.C.s as regards SQ. For that same reason I am using a SOIC OPA2134 in my PC soundcard instead of the LM4562
SandyK

[AndrewT]

Hi Ztan,
try using a dual with a convertor to fit the 14pin DIL.
The two channels will run a little bit cooler and take less out of the resistor/Zener combination.
Once you have the two channel conversion sorted, that opens up the chip options.
Check to see if unity gain stability is required. Most duals are stable but there are a few that are not eg. opa2228.

[ztan]

Originally posted by AndrewT
Hi Ztan,
try using a dual with a convertor to fit the 14pin DIL.
The two channels will run a little bit cooler and take less out of the resistor/Zener combination.
Once you have the two channel conversion sorted, that opens up the chip options.
Check to see if unity gain stability is required. Most duals are stable but there are a few that are not eg. opa2228.

Running a dual converter to fit the 14DIL or 2x OPA627 was my next step. I'm also probably going to go to a dedicated power supply to see if getting the Zener out of the power supply makes a difference.

Anyone tested the OPA827 prototypes yet?