[Jukebox-list] AMI R145 Amp Modification

[WHITE, JAMES P]

Dave,
I'm in the dark about impedance matching.

As far as feeding two sources... I plan to use a switch so only one
source at a time will feed into the next stage.  Actually the switch
will be a two pole - one side to switch between the two input signals
and the other side to deenergize the muting relay in the amp for mp3
play.

"will the MP3 match which ever way you connect it?"  I have no idea -
but I'm glad you asked.     

I hope you are correct about the hum being to feint for the amp to
notice.

As you can see mostly in the dark on this mod so your comments and
questions are appreciated.

JP    

  






James

What about the impedence matching - feeding two sources into the next
stage? Come to that will the MP3 match which ever way you connect it?
However I would have thought that most hum will be well below 300MV and
too
feint for the Amp to notice.

Dave H


Hi Karl,
I too wonder what kind of sound this will result in.  I'm hoping for
just a good quality momo sound - with lots of volume of course!

Going from a stereo signal to a mono amp is not one of my concerns -
only because I have had some success with this.  The last machine I
restored was a Seeburg 222 which had a stereo cartridge but a HFMA-2
mono amp.  I wired the tone arm cable as recommended by one of our list
members and it sounded fine.  I could be missing something here however.


I see the bigger challenges as:
1) Finding the right spot in the amp to inject the 300 mV signal.  (I
need to jump past the first couple stages of amplification and try to
avoid the RIAA(?) equalization circuit)

2) Inducing Hum with all this extra input cable.

3) What happens in the amp when the signal path is switched to the new
line level signal?  Will the voltages go wild?

I have the cap kit and hope to start rebuilding the amp tonight.  I'm
slow so this will take a while.

JP
_____________________________________________________________________


JP,
Wow......MP3's through a mono G amp? I'm not the resident expert here by
a
long shot but I can't imagine that sounding anywhere near what I'm
guessing
your intentions are ( lots of cool music coming out of an old restored
jukebox despite the small selection of records in it).

Karl
Columbus Coin-Op Shop
2061 S. Lumpkin Rd.
Columbus, GA 31903
(706)507-2963