ohms mismatch in SOLID STATE amps

[ruger9]

I've seen so many conflicting opinions on this... hoping a tech could chime in...

All I want to do is put a speaker out jack in my little DA5, which is no problem. The problem is it wants to see 8 ohms and all my cabs are 16 ohms. SAFE OR NOT???

[rockon1]

Safe. You will lose a bit of power output at 16 ohms. Only when you go BELOW safe minimum rated load will there be a problem ,not higher.

[unklmickey]

..The problem is it wants to see 8 ohms and all my cabs are 16 ohms. SAFE OR NOT???

hi Ruger,

for solid-state having a higher impedance load than specified is no problem at all. you will get less power transfer, but there is no danger to the health of the amp.


installing the jack is where you might create problem.

in many solid-state amps, neither of the wires to the speakers are, or can be grounded. if this is the case, you will need an insulated jack.

[ruger9]

installing the jack is where you might create problem.

in many solid-state amps, neither of the wires to the speakers are, or can be grounded. if this is the case, you will need an insulated jack.

Yeah- i caught that on the schematic. Actually got instructions from a guy who did this to a Microcube, DA5 shouldn't be much different. Here's a question: he said to use a mono "grounding jack"... I've heard of a SWITCHING jack, is that the same thing? (the jack will disconnect the internal speaker when used.)

I was at Radio Shack tonite, and they had 2- and 3-conductor mono jacks, but nothing that said "grounding jack".

[unklmickey]

no, that's a whole 'nuther issue.

disconnecting the internal speaker is one thing. that's the switching part.

having a plastic bushing, that prevents the sleeve connection of the jack from making contact with the frame is another issue.

you should definitely get a schematic of your amp, so we can determine if this is necessary.

if it IS necessary that neither wire is grounded, but you use a standard switching jack with a metal bushing, your amp will be damaged.

[fadetowhite519]

insulated jacks will either be made out of plastic, or have plastic washers, ect..

[ruger9]

I've got the service manual for the DA5, incl. schematic. The instructions I have from the guy who did it to a MC specifies that the jack has to be insulated from the chassis, I got that part.

Just need to find out where I can get a switching jack. Apparently, Radio Shack does not have them. Seems like I need a switching jack that I THEN have to isolate from the chassis with a plastic or rubber washer?

Here is what the guy did with the MC:
So far I've only added the External Speaker Jack. I opened the amp, disconnected the speaker wires from the
speaker. I then used a plastic bodied shorting stereo jack and installed it where you will see on my bmp. picture I will attach.
The jack has 6 terminals. I will draw a little picture of the circuit (crudely) and show the wiring for both the ext speaker AND the line out jacks. There is a slight problem though...if you plug anything into the REC OUT/PHONES the signal to the new jacks is broken. As I'd like to be able to run an extension speaker OR a clean line to a bigger amp without the speaker cabinet compensation of the REC OUT jack, I need to find another point in the circuit to tie in the new jacks.
Get the plastic body jacks Marshall and others use. Mono shorting jacks or stereo shorting jacks are suitable.


I've got .pdf files of this guys mod, complete with his homemade schem, as well as the DA5 service manual, also a .pdf file. I don't have a way to host the files, tho... I'll email them to anyone who's interested or wants to help! Thanks!

[ruger9]

MORE INFO...

This amp doesn't have a chassis. LOL. I'll be mounting the speaker out jack to the wood/tolex cabinet. NOW does it matter if the jack is a grounding jack or not?

Seems like all I need is that switching jack mentioned above. I've never worked with switching jacks- I assume there's no way to wire a "regular" mono or stereo jack to pass signal when nothing is plugged into it?

my idea is simply to put the switching jack in-line on the speaker wire.

Nothing plugged in = jack passes signal to internal speaker.
Something plugged in = jack sends signal ONLY to what's plugged in.

Seems simple enough, unless I'm missing something about how a switching jack needs to be wired...?