Hello,
Im new here, hope this is correct subforum. I plan to test my working integrated amplifier Marantz PM-750 DC, want to try their preamp.
I already research that its doable. I want to make sure, is this the correct signal path? Here is the zoomed schematic, and below is full schematic.
What i read is right before power amplifier board to make an output.
Red is right channel line
Orange is left channel line
Blue is where i plan to cut.
And second question, if i plan to test the amp, should i put E-CAP bipolar 10uF 25v in series each channel, just like what i see in my Marantz 1180 DC right after "MAIN IN"?
Thank you
Im new here, hope this is correct subforum. I plan to test my working integrated amplifier Marantz PM-750 DC, want to try their preamp.
I already research that its doable. I want to make sure, is this the correct signal path? Here is the zoomed schematic, and below is full schematic.
What i read is right before power amplifier board to make an output.
Red is right channel line
Orange is left channel line
Blue is where i plan to cut.
And second question, if i plan to test the amp, should i put E-CAP bipolar 10uF 25v in series each channel, just like what i see in my Marantz 1180 DC right after "MAIN IN"?
Thank you
Usually the Tape out or Direct out outputs provide the preamp output you are looking for, so surgery may not be needed.
Unless you need tone and filter control?
Also, C701 & 702 provide the AC input coupling so no extra cap is needed.
Jan
Unless you need tone and filter control?
Also, C701 & 702 provide the AC input coupling so no extra cap is needed.
Jan
@Mooly thank you for your replay. That so fast!
So i can start to my plan. Luckily i found a jumper before power amp. Make a shortcut cable that i did not use tape in and out for temporary PRE OUT.
I desolder the jumper (red circle) and put the audio cable.
Then desolder the tape cable (blue circle) then connect them to the TAPE OUT (red circle).
Will test them tonight cant wait to hear them. I like to listen music at night, nobody will annoy me lol... And no noise from outside.
Will update how it sound,
So i can start to my plan. Luckily i found a jumper before power amp. Make a shortcut cable that i did not use tape in and out for temporary PRE OUT.
I desolder the jumper (red circle) and put the audio cable.
Then desolder the tape cable (blue circle) then connect them to the TAPE OUT (red circle).
Will test them tonight cant wait to hear them. I like to listen music at night, nobody will annoy me lol... And no noise from outside.
Will update how it sound,
Yes @jan.didden that is my plan. That is exactly what i did. I still dont know yet how it sound and if its good,
Im thinking to make a hole for new RCA like and old amp that have PRE OUT and MAIN IN and a jumper. But i love it so much that i feel bad to make a hole to it... lol
Im thinking to make a hole for new RCA like and old amp that have PRE OUT and MAIN IN and a jumper. But i love it so much that i feel bad to make a hole to it... lol
Hi, if it is supposed to sound good or better please replace those 4558 for something decent (and not too fast) as well. All the coupling caps 1 µF, 4.7 µF and 10 µF can be replaced for 5 mm film caps. Larger values like 100 µF can be replaced for bipolar Nichicon MUSE BP-ES caps.
In all cases avoid 10V types but choose higher working voltages in the same physical dimensions. They have become way smaller so that shouldn’t be an issue. Possibly 25V types of today have the same dimensions.
And eh... clean both panels, cables and PCBs with a mild soap/water mix. Immediately dry with a cotton cloth. Redo with just a moist cloth. Use Isopropyl alcohol to have the boards spotless.
In all cases avoid 10V types but choose higher working voltages in the same physical dimensions. They have become way smaller so that shouldn’t be an issue. Possibly 25V types of today have the same dimensions.
And eh... clean both panels, cables and PCBs with a mild soap/water mix. Immediately dry with a cotton cloth. Redo with just a moist cloth. Use Isopropyl alcohol to have the boards spotless.
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Ahh i understand now. But that TAPE OUT, we cannot use volume and balance?
@jean-paul its a bit expensive that wima caps. what IC do you recommend better than that 4558? Im curious.
The only NJM4558D that needs to be replaced is Q747. I'm wondering why they chose a BJT input as the servo amplifier?
Best regards!
Best regards!
ReisDaddy, the Wima don't cost much when bought in numbers. For opamps I would be careful and use the better NE5532. It is simply very good. There are recent opamps with slightly better numbers that do probably not work out too well in this device. NE5532 does not create problems and it is cheap.
If you can still find it the JFET OP249 is nice. NJM4580 is also cheap and an upgrade to NJM4558.
If you can still find it the JFET OP249 is nice. NJM4580 is also cheap and an upgrade to NJM4558.
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Yes that is correct, so this may not work for you.
But you can use the connector, drilling extra holes in nice amp chassis is something I try to avoid if possible.
If never gets any better ...
Jan
Wima caps are expensive, RD???
Go look at Jupiter, MiFlex, Duelund, Mundorf - even Jensen! 😵
One better uses industry standard stuff instead of audiophile jewelry. Besides that audiophile stuff is not available in 2.5 or 5 mm pitch to replace the worst of all: electrolytic caps. The only manufacturer that was able to produce a 22 µF MKS cap in 5 mm pitch was Wima.
Sure - but:
a. there's the scarf inside the case that needs to be cleaned out,
b. there may not be sufficient space on the back panel, and
c. the holes need to be exactly the right size for the insulating washers.
Not for the fainthearted but a 15 minute job really 😀
Space enough.
Some reluctance when enlargening the RCA SPDIFs mounting hole in a brand new Denon PMA-60 though.
Space enough.
Some reluctance when enlargening the RCA SPDIFs mounting hole in a brand new Denon PMA-60 though.
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I've often wondered this as it is not uncommon to see and the only conclusion I come to is one of cost... they probably have zillions of 4558's and it makes commercial sense to stick to one part wherever possible. Provided its configured correctly its OK (equal input bias currents). I guess the cost of the extra resistor is insignificant compared to the cost of a FET opamp.
I can not think of any other reason.