External Speakers to USC2

I'd like to hook up some external speakers to my Seeburg USC2. I searched the forums and found this:

"Try connecting an external speaker to the terminals on the amp front. use the "16" watt and "GD" ground terminals. "


My question is, what type of speaker should I hook up as far as ohms go?

Thanks,

Torin

Hi Torin,
Seeburg fully explained what/ how to attach speakers in the model's Service Manual, and/or the I and O manual.
Ron Rich

Torin, the machine speakers are stated to be a 5 ohm load, so based on that an 8 ohm speaker will consume approx half the power stated on the taps.

The actual TPO/RMS per channel is around 28watts at the beginning of clipping and the AGC gain structure will not let those amps to be driven into clipping (if working normally) so the power will be lower still.. Make sure the externals are efficient.

Rob/NYC

Thanks guys. I will consult the manual and hook some up. Looks like the 8ohm external speakers should work if I'm reading your response correctly Rob.

Just don't want to blow the amp, of course.

Yep, 8 ohm will be fine.

Rob

Would it be safe to wire two separate 8ohm speakers to that 16 watt terminal?

I got one speaker working great through that but wasn't sure about hooking up two.

Thanks for you help.

Torin

Torin, I'm not sure what is being asked. But, I assume you want to connect one 8 ohm speaker to each channel of the amp,,,,,Correct? That is fine. You can use the "16 watt" taps or the "40 watt" taps but put the machine speakers on the low wattage taps (if you wish to use them).

Rob

Ok, I get where to put the external speakers now. Thanks a ton Rob.

So I should move the machine speakers to the low wattage terminals due to an overload situation?

Well, I hooked up my external speakers and all is well. I found the best sound for me was to hook the external speakers to the 4 watt terminals and the machine speakers to the 16 watt terminals.

I figure as long as I keep the load for each channel to below 50 watts, I am doing ok. I don't know much (obviously) about the amp situation but it sounds nice. The external speakers are ceiling speakers that have their own volume control in the other room. Seems to be working fine.

Until now, the machine speakers have been hooked up to the 50 watt terminals.

Just thought I'd post my setup in case anyone reads it and wants to tell me why I shouldn't be doing it this way.

Thanks!

OH,O--- By any chance, has someone installed a SHP type amp in that USC-2 ??
Ron Rich

Yes, it is a SHP3. What is oh oh about it? Now you've got me worried.

Well, A USC-2 was not designed to run the SHP series amps--it was designed to run theTSA10B. If running a SHP Amp the heat sink is mounted in such a manor as to prevent air flow, which causes the outputs to over heat--and worse- if someone has not done so, remove the black plastic "funnel" attached to the rear wall, and be 150 % SURE, nothing is blocking the upper vent "hole". SAVE that funnel, as it MUST be attached if/when, a TSA is installed. Ron Rich

Ron, Torin, prior to Rowe product becoming dominant in the late 80's NYC was pretty much Seeburg with the USC series being the most popular. Of the few dozen I saw and worked on, about half had SHP series by then. There were two that had an earlier amp with integral volume control and an RVC was mounted on the back.

From an electrical standpoint, if the amp does not idle hot (bias) and isn't driven flat out, the poorer ventilation won't itself cause a failure. However this being New York, loudness rules and those amps took a beating. I thought about offering to install a muffin fan in place of the chimney and tied to the motor power to exhaust the cabinet. I decided not to get involved as that would just suck in the filthy air in those places and the CD machines were about to be available. For home use it might be a viable solution.

For Torin, the SHP series sell for a higher price than the TSA so you could sell the amp in there for the correct one, get a recapping kit and still come out at least even. FWIW: I'd keep the SHP,.Make sure the basic mod's (jumpers, 100 ohm flame-proof resistors and correct bias) are done Despite it's 'original sins" it is a good, strong amp with all silicon devices.

Rob

Wow, thanks for the great replies Ron and Rob. This place is great.

Rob, that must have been something working in that industry in NYC in the 80's!! I'm sure you have many stories. I will keep the SHP for now and make sure the mods are done. I have adjusted the bias already but will check on the resistors and jumpers. Thanks for the feedback. I might look into putting a small fan in there too.

Ron, I looked and the funnel/horn thing is gone from the back of the cabinet. I guess if I ever switch the amp out, I'll have to look for one. As for the upper vent hole, I'll have to check to make sure it is unblocked. Thanks again.


On a side note, do you know if it is possible with the SHP3 to hook an external turntable into the amp?

Torin

Rob, Torin,
A SHP-3, will have had all of the mods done in production--unless one of your Geppetto friends removed them !
Yes--you will need to build some sorta switching unit, but an external audio source can be used.