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I wound up with two emulators with defective audio amps so I decided to order a couple of mini amplifiers to see if I get them working. They’re PAM8403 chips direct from China, just like the ones they came with. I took the headphone out into the amp and they sound just like the others now. I had to break the traces on the PCB going to the speaker lugs but otherwise it was pretty simple. The pre-amp output seems a little high to me. Great for headphones but a bit high as a line out.
Now to find two more jukeboxes to go with them…
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Hi Sooner
I remember Andy saying something similar to that about the pre amp & lineout.
Do you still get the background hum when using these amps?
So now you have them working what wallbox are you going to do next ? Anything in mind?
Am guessing you should have plenty to choose from over there. I keep looking at Rockola’s as so far I have not had one but they demand some high prices over here, so may have to stick with the Seeburgs.
Cheers Scudie
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The background hum in all of mine isn’t too bad. Hardly noticeable unless the volume is very low. I haven’t really compared to see if it’s any different with the new amplifier.
What I notice on all units is that the tone changes significantly with volume level. As volumes is reduced from max the high frequencies are noticeably reduced around 80% and below. It’s also kind of odd that the line out varies with the volume control. Make me think the circuit was adapted from a design intended as a headphone out.
I saw on the facebook group someone had done one in a Coke theme. It looked pretty nice so I’m thinking about that if I can find one with poor chrome for a good price that I wouldn’t feel bad about painting.
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I saw on another post where Michiel mentions he has buzzing in his left channel speaker but not through the headphones. If that the case then it sounds like the left channel buzzing problem is in the power amplifier stage? If so you might be able to cure that by making this mod to your units too.
It take a long time directly from China but the amplifier is cheap!
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Klaatu – I know a line out should be feeding the PAM8403 on the unmodified emulators but I think the headphone out is what’s actually feeding it. The max volume is the same on my modified emulator as it is on my other emulators that weren’t defective. I wouldn’t expect that if a much lower line out signal was feeding one of them. Also, I haven’t studied the PC board closely enough to figure out what the circuit looks like but the volume pot output appears to go directly to the headphone output. Bottom line is that the modified amp sounds identical to the others but without the buzzing.
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Something else I notice. The volume control on the emulator cuts the high frequencies when the loudness is reduced below about 80%. The volume control on the external amplifier doesn’t do that. On my SC boxes I’ve been keeping the volume at about 60% and using the built in buttons to control the volumes. With the external amp I can keep the emulator volume at 100% and adjust the external amp volume to 60% and I don’t get the cut in high frequencies. In that respect it actually sounds a little better to me.
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I’m sure there are better amps available if you have room to fit them in.
The PAM8403 amps actually sound pretty good to me with better speakers. I hooked one up to directly to my hifi stereo speakers and was impressed with the volume. The sound quality was similar to what it sounds like when I use a Bluetooth transmitter connected to the headphone output.
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Ok so the Buzzing on the left speaker is GONE!!!
I have found time this week to have a go at the amp and emulator.
After removing the speaker / audio connector block as advised by Sooner, I cut the traces that lead from under the audio connector block to four of the connections of the on board amp, according to Klaatu’s post of the amp they are 1-3 & 14-16.
I ordered some of the PAM 8403 amps back in September of last year, but have since been busy with other projects. Finally this week I found the time and parts to have a go at replacing the onboard amp with one of the new ones.
Got it wired up this afternoon, the good news is that if there is any buzzing at all it is so very slight that I can’t audibly detect it through the left speaker now, it is a total transformation to how it was beforehand.
I may be being over critical as I am paying particular attention to the sound, trying very hard to listen for anything that should not be there.
As you can see in the photo it’s only a trial at the moment connected to the SC1 that I fitted the LED’s to, that are still going strong.
Have been sat listening to it now for an hour or more now and I believe all selections so far have been buzz free. I am convinced that it’s cured it. Very Happy & well worth the effort! Thanks to Sooner & Klaatu for the information in previous posts.Cheers Scudie
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Hi Klaatu
I think that the photo makes the led’s look brighter than they really are, just look at the ones on the emulator, the ones in the photo are the cool white colour, I have not tried them with a cover on yet to check what they look like, if they are too bright I will fit some higher rated resistors. These have been on now for weeks & weeks.
Cheers Scudie
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