I started tweaking a relative's Stereo Receiver in the early 1970's -- a wonderful Madison Fielding battleship -- it's a process which never stops. except for the FM tuner section, transformers and switches, there isn't an original part in the darned thing.
so delight to your heart's content!
so delight to your heart's content!
PMA said:
Since it is an MM amp, not an MC amp, these may not be the
best choice, as has been mentioned both in this thread and
other recent threads. The reason is that the input current
noise may cause these op amps to end up more noisy than
a decent JFET-input opamp, despite their excellent voltage
noise figures.
I always like to follow up with what I did/what I found, although it seems no one ever reads it. 
Anyway, reworked the regulator to supply +/- 16V, and built my own adapter since I couldn't get ahold of the guy who apparently has some premade ones. Replaced the inverting and non-inverting input coupling caps with a new Panasonic FC caps of the same value, and popped in a OPA2134. Seems the 2134 is as good as the 2604 for DC precision, as offset at the output is under 1mV. So I replaced the output cap with a jumper wire.
Sonically, the 2134 sounds peachy. But what is most noticeable about the change is how much quieter the 2134 is than the original Hitachi part. Truly a dramatic difference.
Again, thanks for the help guys. Got a great bunch of transistor geeks here.
Anyway, reworked the regulator to supply +/- 16V, and built my own adapter since I couldn't get ahold of the guy who apparently has some premade ones. Replaced the inverting and non-inverting input coupling caps with a new Panasonic FC caps of the same value, and popped in a OPA2134. Seems the 2134 is as good as the 2604 for DC precision, as offset at the output is under 1mV. So I replaced the output cap with a jumper wire.
Sonically, the 2134 sounds peachy. But what is most noticeable about the change is how much quieter the 2134 is than the original Hitachi part. Truly a dramatic difference.
Again, thanks for the help guys. Got a great bunch of transistor geeks here.
EchoWars said:I always like to follow up with what I did/what I found, although it seems no one ever reads it.
I am sure a lot of people read it, but they might perhaps be
satisfied with just reading about your findings withoug making
any further comments. Having been involved myself in the
thread and trying to help you, I appreciate that you report
the results.
Monsterle said:
perhaps you neighbor in Aachen has one:
http://john.ccac.rwth-aachen.de:8000/telefunken/tr550/index.html
I always like to follow up with what I did/what I found, although it seems no one ever reads it.
Anyway, reworked the regulator to supply +/- 16V, and built my own adapter since I couldn't get ahold of the guy who apparently has some premade ones. Replaced the inverting and non-inverting input coupling caps with a new Panasonic FC caps of the same value, and popped in a OPA2134. Seems the 2134 is as good as the 2604 for DC precision, as offset at the output is under 1mV. So I replaced the output cap with a jumper wire.
Sonically, the 2134 sounds peachy. But what is most noticeable about the change is how much quieter the 2134 is than the original Hitachi part. Truly a dramatic difference.
Again, thanks for the help guys. Got a great bunch of transistor geeks here.
Hello, I just found this thread. I know it is old... but I have a similar project. You guys gave good ideas here. Thanks. But what happened to the 20 pF capacitor connected between pins 3 and 5 in the original HA1457 (pic attached)? I understand it is ignored / unnecessary. Thanks.
Attachments
"It's in there".
The HA1457 required an external compensation cap. The OPA2134 has the compensation built-in.
There's history behind this change but you don't need to study it.
Attachments
Ok many thanks. That explains well. I've seen that diagram in OPAx228 (it is very low noise 3nV/SQRT(Hz) but doesn't use FET inputs). I will use the OPA134 to replace the HA1457. Thanks.
There is an HA1457 to OPA134 Upgrade Adapter here for those interested:
HA1457/HA12017 Upgrade Adapter | BrownDog 140901 | Cimarron Technology
You could use two AD797s, it's rather low noise. Although I don't know how much these cost
No, its not low noise, its low _voltage_ noise. Alas the current noise is correspondingly poor making it a mismatch for a MM preamp where the impedances are much higher than the AD797 is designed for.
NE5534A will perform better, as will any good JFET or CMOS input opamp.
I'm not sure WHAT datasheet you are reading, but the one I have shows the NE5534 to be VASTLY superior to the HA1457---an order of magnitude less distortion and noise. I don't see any listed spec for slew rate, but I'll bet it's WAY worse than the 5534's 13v/µSec. AND, the 5534 is an absolute BARGAIN at 97¢ each!! That is an order of magnitude less $$$ than SOME of the opamps advocated here.
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