Hi Gents,
Question for the experts, which opamp within the Denon PRA-1100 preamp would you consider upgrading first? IC301 or IC302 or both (don't care about phono or headphones)?
Looking to see what kind of improvements I can achieve with this mid-fi superstar..
Question for the experts, which opamp within the Denon PRA-1100 preamp would you consider upgrading first? IC301 or IC302 or both (don't care about phono or headphones)?
Looking to see what kind of improvements I can achieve with this mid-fi superstar..
I've heard that sometimes that's done on purpose to thwart people trying to copy the circuit.
Those values being wrong would certainly do that.
Those values being wrong would certainly do that.
Check visually what is fitted. 7.5k and 75k equate to 6818 ohms when viewed as being in parallel and that essentially equals the 6k8 of R317 and R318 and that is what is needed to equalise the opamp input bias currents.
This really haunts me...a lot of people trying to replace dip op amps supplied at +-18v with smd modern expensive op amps that have a max supply of +-18V .The original op amps allowed a max supply of +-22v. Try first to see which of the modern op amps allow at least +-20v , then which are found in dip form because at such high voltages some heatsink might be needed and the drnon pcb might not allow you to mount a heatsink!
To my knowledge the only available replacement able to hold both supply and heatsink capabilities is the old ne5532....
Just touch the smd op amps found in modern behringer crossovers supplied at +-15v and see how hot they are when on...
To my knowledge the only available replacement able to hold both supply and heatsink capabilities is the old ne5532....
Just touch the smd op amps found in modern behringer crossovers supplied at +-15v and see how hot they are when on...
Those are good quality, my Kenwood has 5218 or 6556 in the service manual
And Denon is overall well regarded.
I see no need to change the op amps.
And Denon is overall well regarded.
I see no need to change the op amps.
A few presumptions here, I have a few in mind which are up to +-24v, curious to explore benefits.
I repeat: slew rates of 15 V/uS are about the limit for audio.
Changing op amps means redesigning the circuit, such as changing resistors and capacitors as well, not just swapping the chips out and having a miraculous improvement.
And repeated soldering can damage PCB tracks.
If you really want to experiment, build a new breadboard type, and if happy, solder it up and put it in a proper housing.
Some OPA series go above 40 in slew rates, totally too much for audio use.
Can cause oscillations, which may damage your amplifier.
Think it over, it is your time, money and effort.
Changing op amps means redesigning the circuit, such as changing resistors and capacitors as well, not just swapping the chips out and having a miraculous improvement.
And repeated soldering can damage PCB tracks.
If you really want to experiment, build a new breadboard type, and if happy, solder it up and put it in a proper housing.
Some OPA series go above 40 in slew rates, totally too much for audio use.
Can cause oscillations, which may damage your amplifier.
Think it over, it is your time, money and effort.
Oh, one more thing...check out the slew rates of various famous / common chip amps, you are after all going to drive a power section in the amp.
Most are below 12, so a faster pre will achieve nothing.
Transistor circuit data is not available with me..
Again, I advise caution in op amp rolling.
Most are below 12, so a faster pre will achieve nothing.
Transistor circuit data is not available with me..
Again, I advise caution in op amp rolling.
Note that M-5238 (IC301) has Jfet input, which limits the options for suitable replacements. Perhaps OPA2134 would work well, but have no idea if it will be an actual improvement.
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