70 Volt Extension Speakers

[rockinrob]

I have a MM6 and the amp, a R-4359A, has 70 volt speaker capability. I currently have outdoor speakers, running out of a Sony A/V receiver, which I am thinking of changing out to 70 volt. So my question is, has anyone had any experience with doing this and have any suggestions?

[mb9513]

Rob: I haven't done it in a long time but used to be able to buy the step down transformers that you will need for each speaker. then you have to select the correct tap to get a balanced volume from the internal and external speakers. the 70 volt application was meant for large areas, think department stores or large multi room lounges. the higher voltage "pushed" the sound far away down the line. if you are not running an extreme distance, one of the other taps might work. just use heavier cable. if you have the installation manual for your juke it will probably give you the distances you can safely run. Mark

[wdln]

What Mark said ^^^^

The service manual for the MM6 has wiring examples of how other speakers can be safely connected to the stock amp with or without 70V, depending on how many there are and their impedances. It shouldn't be necessary to go the 70V route unless you are driving lots of speakers that reach far distances. If your Sony amp is able to push to them from wherever it's located, then the MM6 should be able to as well without the need for employing a 70V setup.

I'm looking at my MM6 manual now and on the output transformer, the example wiring diagram shows that you can use terminals E2 (-) and E4 (+) on each side to connect a pair of external 8-ohm speakers. If your speakers are another impedance like 16 or 4 ohms, you'll need to use different terminals.

The MM6 should have two RCA-style plugs for the amp input. You could Y-cable-split the tonearm output and either run it into the phono input on your Sony amp (if it has one) or run it through a phono preamp and from there, into any line input on the Sony amp. That would have the advantage of 1) retaining the functionality you have now with the Sony amp for the radio or audio from other sources and 2) not having to do any speaker rewiring or 70V stuff. The raw tonearm output would be unmuted though (picking up sound whether it's playing a record or not) and it could be a bit noisy between records. It is possible to rig up your own mute relay for that feed, driven off the mech's factory mute signal, but that takes electronics knowledge and a little doing. I'm happy to share how I've done it if that's something you're interested in.

Some newer amps have an aux input/output for driving blinky lights in the case to the beat of the music or connecting your own audio source to the juke's internal amp; this port could be used to take a line-level, pre-amped tap that could go into an external amp. The MM6 does not have this, I don't think... I think that's limited to the last of the Rowe-AMI phonograph juke models.

I've used these preamps for these kinds of mods. They're cheap and sound OK. You definitely want to run a preamp on the magnetic cartridge the mech uses, as it adds the correct EQ curve and boosts the signal up to a normal line level.

www.amazon.com/Pyle-Phono-Turntable-Preamp-Preamplifier/dp/B00025742A/

These are no-frills units with no adjustments of any kind. You also usually need to hook a ground wire up between the case of the preamp and the chassis ground of the mechanism. With the resurgence of vinyl's popularity, there are some really nice phono preamps out there that you can spend a lot of money on that will do more and sound better, but Pyle gets the job done.

[Ron Rich]

Dave,
Are you suggesting that someone should l@k in a "Service Manual" ?? Horrors !!! Ron Rich

[wdln]

I know, can you believe it??

:-)

[rockinrob]

Dave, you and I are actually on the same page. I had already split the tone arm output and ran it into the phono input of the Sony. Worked great, then about three days later I turn everything on and I hear a loud hum from the Sony and find out the outdoor speakers it drives have blown. Haven't determined the cause yet. I have never had any issues with the RCA cables I have but did order a shielded cable and may try again. These speakers are about 200 feet from the receiver.

The Sony does have a line level out that I am splitting to run two other receivers as slaves for other outdoor speakers. Glad you mention the MM6 line in. Didn't want to just plug things in, even though it should work, without get some other input.So I could run go from tone arm to Sony and back to the MM6 amp.

I have a pond that would be another 100 feet from my existing outdoor speakers. I know the 70 volt would give me some added options because of the distance and area I am covering. Which is why I was asking about any personal experience.

As a suggestion on flashing lights to music I currently have a Raspberry Pi with a program called Lightshowpi which is really great for customizing lights to sound. Many use it for Christmas lights. I just picked up a 7" monitor for the pi and am planning on taking out the Rowe AMI info window, to the right of the switches, of the MM6 and mount this in there. Maybe connect a camera to the pi that looks down on the turntable. It would also allow me to have mp3 songs loaded onto it and I have a line out card for the pi, so I could run it into the line in on the MM6.

As for my own experience, I was an industrial electrician/electronic tech for 30 years and currently teach part time tech classes at Lake Land College in Mattoon, IL. So I am comfortable doing anything electrical.

[wdln]

Do you think the amp/speakers blowing was the fault of the jukebox? I can't see how the tonearm would have backfed any high voltage or anything like that, especially if it was working fine for a few days. If the juke still works by itself, I'd say it was just a coincidence and the amp had some other random failure. Sounds like you have a plan for how you want to do it though.

Note, however, that the RCA inputs on the MM6 amp are not true line-level (1v p-p) inputs, so beware of plugging a line-level signal into them from your Raspberry Pi or anything else. Those jacks are expecting the phono-level signal from the tonearm, which is much lower in level. The preamp in the MM6 will also apply an EQ curve specific to it being a phono type of signal. Tapping off the tonearm plugs for an output to another device is fine, but running line level inputs to the internal amp will at least sound terrible (overdriven), and at worst damage something.

At the very least you'd need to build a resistor pad to dump the line-level signal level down to what the MM6 amp is expecting, but it still might sound weird with the phono EQ applied.

Homemade muting circuit, since you sound capable: On all of the 1100-mech Rowe-AMI units, there is a round mute plug with 3 wires in it going into the amp. On the one I'm looking at right now (an R-80), the red/white and orange wires have 30VDC across them when there is no record playing, and it drops to zero volts when the record starts. You can use a 30VDC DPDT or DPST relay, or a lower voltage relay and an appropriate resistor in series, to create your own mute function. The simplest way is to have the relay short the center pin of the tonearm feed RCA to the shield when energized (one pole of the relay for L, one for R). When the relay contacts open, the short across the RCA's will open, and the audio signal flows normally. Wire up those contacts to 2 pairs of RCA's in parallel and there ya go... it doesn't even matter which RCA's you use for input or output.

The amp does something similar internally using a multi-pole relay, although I think the muting is done on the output, not the input, so it's definitely not shorting the speaker wires across each other. I've mostly made muting circuits for when I'm putting a modern amp into a jukebox to add bluetooth capability, and I'm ditching the factory amp entirely.

Happy jukeboxing, fellow Illinoisan! ;-)

[rockinrob]

So if I'm understanding, the line in jacks on the 50w amp, not the pre-amp that the tone arm plugs in, is also phono? Didn't see any mention in the manual about it.

I do have a powered A/V switch that I currently use to split the line out of my main amp to run to other receivers so I may try it with splitting the Rowe tonearm. Also looking into some converters like ones in car audio that convert the speaker out to line in or ones that convert 70 volt to line in.

Right now I am sidetracked on a couple of Wallboxes, a WRA-200 & WRD-200, I picked up. Might try to get the WRA to work with the MM6 and convert the WRD to mp3 with a RPi.

Now I know why this board is named Jukebox Addicts. Bought the MM6 a couple months ago and now can't get enough. LOL

Thanks for the instructions on the mute relay.

[wdln]

OH, I didn't realize that amp had the aux input on the amp side. I'm not 100% sure on the specs for that, but it's probably a normal line-level input, not phono. But since it bypasses the preamp, it bypasses the volume control too. So whatever you hook up to that would have to be variable from the source, or you'd need to buy/build your own volume control in-line.

[rockinrob]

I ended up installing a car audio speaker to line level converter to the 8 ohm extension speaker connections of the main amp. The convertor had gain adjustments for the output and I set it so that when the jukebox volume is at max the line out level will be just below the Sony amp max input level.

This worked out really well.