Yamaha A1 integrated amp (phono issue)

[Asmodeus2112]

Not yet. I was hoping for some ideas from this thread, but as you can see nobody replied. I am working on my M-4s, and haven't gotten to my A-1 yet. When I do I was going to do the test Clinic described, then make a few other cables and see what happens...

 

[avionic]

Resurrecting this thread. I have a new to me A-1 and very interested in how to replace the phono cables. Anyone have some pics and maybe description of what wire to use?

Can you pry those RCA plugs off of the PCB mounted jacks ?

 

[avionic]

very interested in how to replace the phono cables.

Is there and issue with the OEM cables ?

 

[Asmodeus2112]

Is there and issue with the OEM cables ?

Well, according to @clinic-audio the cables are microphonic. Which I take as they pick up interference? I was going to try his test first to see if i notice the symptoms before trying to remove the wires any other attempt at a remedy.

 

[avionic]

I see..

 

[Asmodeus2112]

I see..

The OP never followed up on this thread for closure, and nobody else seemed to confirm what Clinic was saying. Just bookmarked it for the day I can work on my A-1.

 

[redstarjedi]

Oddly the 47k phono plugs don't seem to do anything. My cartridge is 47k, and manual states that when you pull them out - and have no plugs in at all, that it defaults to 100k. Funny thing is i hear ZERO difference between the two cartridge loading, that's odd compared to my A-1000 or other external phono stages that i've used.

 

[avionic]

Oddly the 47k phono plugs

Are these the OEM supplied 47KΩ loading plugs ?

 

[redstarjedi]

Are these the OEM supplied 47KΩ loading plugs ?

They are. I can make new ones my self. I also get some strange buzz when I touch that area anyway.

 

[avionic]

I can make new ones my self.

For a 47KΩ load you would need to use 89KΩ resistors in parallel with the default 100KΩ..

 

[redstarjedi]

For a 47KΩ load you would need to use 89KΩ resistors in parallel with default 100KΩ..

Wow really? I have two 47k plugs in there which is what the manual states?

I can make a pair of 89k resistors plugs.

 

[avionic]

They are.

Measure the resistance of the OEM supplied 47K plugs.. That came with the A-1..

 

[avionic]

A 47KΩ load in parallel with the 100KΩ is approx. 32KΩ total load.

 

[redstarjedi]

A 47KΩ load in parallel with the 100KΩ is approx. 32KΩ total load.

Confused a bit. The manual states plug in the 47k, plugs. Do i only put in one? I'll check to see if they are the right resistance.

 

[avionic]

The manual states plug in the 47k, plugs.

The loading plug set that came with the A-1 ,when new," out of the box " were marked 47KΩ ,68KΩ and 33KΩ.. There actual measured resistance is not as marked. Due to the 100KΩ resistors internally installed in the MM phono input. These OEM loads are then put in parallel with the internal 100KΩ resistors when plugged into the cart load jacks.

 

[redstarjedi]

The loading plug set that came with the A-1 when new out of the box were marked 47KΩ ,68KΩ and 33KΩ.. There actual measured resistance is not as marked. Due to the 100KΩ resistors internally installed in the MM phono input.

Measured them. 91.5k and 92k

 

[avionic]

So..............Actual value.
33KΩ ---> 49KΩ
47KΩ ---> 89KΩ
68KΩ ---> 210KΩ

 

[avionic]

Measured them. 91.5k and 92k

Close enough.. 92KΩ calculates out to 48KΩ

 

[avionic]

https://www.omnicalculator.com/physics/parallel-resistor

 

[redstarjedi]

https://www.omnicalculator.com/physics/parallel-resistor

Very cool thanks. When I get in there I'm also going to check the phono input and the cartridge loading circut board. If I jiggle the phono RCA cable, I get a massive bass heavy buzz from both speakers.

Hopefully only a bad solder joint.