Correct speaker load

[TIMBO]

Hi guys, I got a SS amp that I think was made in the 80's and as usual no info.
It's in sorta working order, scratchy pots.
It has had a speaker change and they have used a 4ohm 350w sub woofer.
This seems to work but I have no way of knowing if 4ohms is the correct speaker load or power rating.
It has 2/2N3773 power transistors.

I could guess that it's about 65w as the model is PS65 

[shooter]

IIRC most transistor amps were designed to handle speaker loads down to 2ohms.  I don't know about "optimum", without docs, it's probably trial n error.

[pompeiisneaks]

Here's an item that has 2n3773's and seems to imply it uses 4w impedance. 

~Phil

[smackoj]

I agree with Shooter; SS amps are usually stable at 4 ohms or even less. If you look at any modern SS bass amp, they always label the output with something like: "160 watts into 4 ohms"  and  "100 watts into 8 ohms"

[TIMBO]

Thanks guy's, I'm sure it's a bass amp.
Sounds OK with guitar plugged in.
I'm going to replace all the pots, some have real problems.

Found a date of may 83 on the PCB.
Trying to find a cheap 100w 4 ohm speaker.

[TIMBO]

Hi guys, Found this in the schem library.
http://el34world.com/charts/Schematics/files/_Miscellaneous/HH%20MA100.pdf

Not exactly the same circuit but pretty close.

Maybe an 8ohm will drop the output to a more useable wattage.

[pompeiisneaks]

Here's an item that has 2n3773's and seems to imply it uses 4w impedance. 

~Phil

Weird my link didn't seem to show up and I've lost it now, /sigh I probably forgot to paste it lol.

[TIMBO]

All good. Thanks mate

[TIMBO]

Thanks guys, converted this bass combo to guitar.

Cab cleaned up well

All original components, reverb tank at the back.

A few fancy knobs.

Passive FX loop.

Some new pots.


An Eminence 100w 8ohm seems to work well.
I wasn't sure what a Solid State Bass would sound like for guitar use, a great result.
Both channels are clear without any flabbiness or muddiness.

A very usable amplifier.

[smackoj]

That is a nice piece. I like the liberal use of shielded cable. Looks first rate. Have you tried any effects with it? Just curious.   

[TIMBO]

Not yet, will do