Modify integrated amplifier as preamp

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#61
Mooly said:
The 2068 is an interesting one, similar to the 5532 in many ways. The 4560 has a much higher than usual output current capability (not needed here) and is often used to drive headphones. The 4580 is good in that regard too. Try them all and see what you think.

One thing to mention... always always buy from reputable suppliers as there are so many fakes around from the usual suspect outlets 😉
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Thank you for the input.

Yes, thats always make me headache when i must find electronic components, and the shipping fee is high, so must carefully buy important things first, then put notes if the things that not available in current shop, but exist in another. Like i must skip OPA2134 or 2132
 
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#63
Mooly said:
If you are swapping these opamps just put the sockets in and try a TL072 which is a FET device and (imo) sounds really really good.
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Mooly said:
I have to disagree on that Jean Paul but I'm not going to force any opinions 🙂 besides saying to listen over a long enough period of time and give it a fair go.
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Agreed. On top of this, guess what's to be found in renowned mixing consoles from Neve and the like? 4558's all over the place in line level circuits, simply because they're just good enuff here, and, yeeks, those bad, bad 'lytics between them. Makes me ask to which level audiophools try to improve the music that is already on the CD or LP?

Best regards!
 
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#64
ReisDaddy said:
Ordinary: use audio device to hear music
Audiophile: use music to hear audio device.
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True! Was member of the latter but saw the light and became member of the first group. Hallelujah!

If audiophiles would design DACs we would see 8 channel DACs with a zillion features, very informative multicolor displays telling all kinds of totally useless superfluous information (ballast) and programmable/configurable by pc and all parameters changeable without too much thought how it sounds playing ... a simple 16 bit 44.1 kHz FLAC album in stereo. Oh wait.....

Never seen a Neve but the mixing stuff I saw/repaired often had many opamps. So many that energy efficient types needed to be used and NE5532 with 8 mA was already too power hungry. Only saw 4558, 4560 in older Japanese consumer stuff really. NJM4580 can be found in stuff like Behringer. The electrolytic caps in mixing consoles thing is not as valid as in consumer stuff where the lowest possible cost stuff is used.
 
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#66
We always run after 'superior sound quality & performance' but forget to enjoy the music. That is not in my case. I like OPA2134 but sometimes 4558 too. I don't know why but i like analog radio tuner over DSP type. Maybe because it's me!


Regards to all
 
#67
Here is the process...

Sketch with pencil

IMG_20240812_124254.jpg


Center tap

IMG_20240812_124548.jpg


Stepped drill first 4mm diameter

IMG_20240812_131757.jpg


After 6 , 8 and last 10mm diameter, then put marking.
I should wait longer, my hand shaking after drilling the metal, so the handwriting PRE OUT and MAIN IN looks bad.
Cannot find fine tip, only bold marker available here.

IMG_20240812_142437.jpg


Then the RCAs.
Actually i dont like that white plastic ring. But no choice...

IMG_20240812_160219.jpg


Then the plug...

IMG_20240812_162603.jpg


Voila... Marantz PM-750DC SE
Special Edition 😆

And waiting for the ICs
 
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#68
Hi I hope you deburred the holes. Can be done with the stepped drill turned lightly by hand. This to avoid sharp metal cutting the insulation washers. Those insulation washers are available in red too. Normally L is white and R is red.

The connection pins are unshielded. You know what the consequences can be.

Good job, I like the lettering.
 
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#69
jean-paul said:
Can be done with the stepped drill turned lightly by hand
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Dohh... I cannot think that simple. But i did pull them using hand plier.

jean-paul said:
You know what the consequences can be.
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No. I dont know. I just follow the old Marantz like 22xx and any other old amplifier do like that. Do you mean the grounding? That rca plastic ring does have lip, so it doesnt touch the body?
 
#70
Even an old dull 13 mm drill will deburr excellently. Officially a good stepped drill will deburr almost automatically.

There is no shielding when using the old fashioned wire bridges. These are from a time that the air was clean and cell phones were still a fantasy.
 
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#74
Lucky did not throw away that low quality rca, i get that free from a cheap dac, i think that was HDMI to rca? or bluetooth to rca?

IMG_20240813_094121.jpg


Indeed disrupt the sleek, vintage aesthetic of those classic amplifiers 😕
Next time ill make better one.
 
#76
ICs just arrived, Please help me, just want to make sure, this IC does not need to modify resistor or film cap or e-cap around right?

Here is Q747 stock is 4558D

Q747-schematic.png


And QE01

QE01-schematic.png


ICs to try (each ic will tested in both location Q747 and QE01

  • JRC 5532
  • L4562 (SOIC to DIP converter, see photo below)
  • TL072
  • JRC 4560
  • JRC 4580
  • JRC 2068

Here is L4562 SMD to DIP

IMG_20240813_122722.jpg


SMD pin 1 to DIP pin 1

Each IC's PDF attached.

Thank you very much.
 

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#79
It keeps the DC offset of the power amplifiers output to 0V DC. You separated pre and power amplifier to be able to us the preamp part with another power amplifier.

This would mean that changing anything in that PM750DC power amplifier is useless as it won't be used. Changing stuff because of the changing is indeed the audiophile way of working 🙂
 
#80
I will keep it as an amp when i'm done playing around to the preamp. That is why i put the jumper so i can use it as pre or for power amp or as an integrated. So the most important thing is just in EQ01? So i'll remove the dip socket there in Q747 ... lol.. sorry for stupid idea.

jean-paul said:
Changing stuff because of the changing is indeed the audiophile way of working
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That was a great joke, you really got me laughing 🤣
 
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