impedance matching and solid state amplifiers

[theaudioengine]

so i'm not new to electricity but i was recently thinking about how i am going to wire my 2x12, and it came to mind that I'm not really sure how impedance matching really works with a solid state amplifier, being how there is an output transformer and no power amp tubes. So I thought I would reach out for some insight.

does Z(s)=Z(l) still result in maximum efficiency?

how does it impact the reflected load of the transformer? I can obviously do a simple calculation to get a quantitative answer, but qualitatively how does it really impact my circuit?

i've got a stereo head, but its wet/dry, with the wet coming from the built in chorus (Ampeg SS140C), however i don't play with chorus and i would have to install another jack plate on my 2x12 to run it 'stereo'. outputs are nominal 8ohm it says, but again what does that mean for a solid state? 2- 16ohm speakers in parallel... 2- 4ohm speakers in series... 2 8-ohm speakers in series because it doesn't matter... put in the jack plate and drive 2-8ohm speakers independently and figure out the chorus situation... i dunno.

seems that a lot of you are tube guys, but your input and experience are appreciated,,

 

[racerevlon]

With solid state, lower impedance is better, as there's no OTHER to damage. Going with a higher resistance will only lower your volume; you have no power tubes to saturate. Wire for 4 ohms if supported, if not, least supported.

Higher resistance is used with tube amplifiers so that you have to push the amp harder to achieve the same volume, driving the power tubes into breakup as well, so tube amps like to see 8-16 ohms. You CAN run a tube amp at 4 ohms but the sound character will be different as you are much less likely to drive the power tubes into breakup.

Hope this helps,

 

[theaudioengine]

makes sense, get the most current i can::get the most power from the system, thanks.

P=VI!

 

[JerryP]

Run the correct impedance or you risk damage. With solid state if you run lower impedance you will fry shit. With solid state if you run higher impedance it's safe, less power. With tubes if you run higher impedance you get flyback voltage and you fry shit. There's really no safe mismatch and nobody can predict how your gear will react to a mismatch. Guys will tell you they ran a mismatch for years and some manufacturers will tell you a mismatch is safe, as a guy that repairs amps I can tell you a mismatch will cause damage and it's always expensive to repair.
Jerry

 

[theaudioengine]

as a guy that repairs amps I can tell you a mismatch will cause damage and it's always expensive to repair.
Jerry

I appreciate your response, the confusion on my end comes from having 4 different speakers outs on the head (2 for dry 2 for wet) and what it says under the jack "4ohm minimum"

what I was curious about is if that is the minimum how will the circuit be affected at different loads, especially in regards to the reflected load. I went back to the manual and read up again on all the different outputs and its telling me 8 or 4,

So is "matched" 8 or 4? that's my confusion, I can literally hook up 4-8ohm cabs to the head and it will drive them because the "int" and "ext" outputs for each channel are parallel. But I don't want to do that, I have only 2 speakers I want to drive. So do I really try to get 4ohm speakers and send an output from each channel to each speaker for it to be "matched" and what does that even mean anymore?

 

[racerevlon]

No. I'm not advocating mis-matching (running out of the 4-ohm tap into an 8-ohm load, e.g.). Always match your load to the correct output tap or setting on your amp.

Question now is, what impedance are your speakers? With a solid state amp an ideal situation would be to have two 8-ohm drivers and run them in parallel for a resultant 4-ohm load. If you run them in series you will get a 16-ohm load. Same math applies if you have 16-ohm drivers.

 

[steve_k]

as a guy that repairs amps I can tell you a mismatch will cause damage and it's always expensive to repair.
Jerry

I appreciate your response, the confusion on my end comes from having 4 different speakers outs on the head (2 for dry 2 for wet) and what it says under the jack "4ohm minimum"

what I was curious about is if that is the minimum how will the circuit be affected at different loads, especially in regards to the reflected load. I went back to the manual and read up again on all the different outputs and its telling me 8 or 4,

So is "matched" 8 or 4? that's my confusion, I can literally hook up 4-8ohm cabs to the head and it will drive them because the "int" and "ext" outputs for each channel are parallel. But I don't want to do that, I have only 2 speakers I want to drive. So do I really try to get 4ohm speakers and send an output from each channel to each speaker for it to be "matched" and what does that even mean anymore?

Mismatching? Just keep the resultant load above the minimums. Holds true for SS power amps in guitar rigs and PA systems. The resultant load is for each side of the stereo output as they behave individually. So, for each side you can run a minimum of a 4 ohm impedance.

For parallel outputs for A or B channels:

2 x 16's = 8
2 x 8's = 4
1 x 16 + 1 x 8 = 5.3
1 x 8 + 1 x 4 = 2.7

 

[theaudioengine]

it's a 2x12, andi want to utilize its minimum impedance, because of exactly what that picture is saying (that was my screen saver for awhile)

I started another thread called "false loads" where I'm wondering about putting a load in parallel with each speaker that dissipates in another manner, so that I can run 1 speaker out of each channel and the output transformer will see 4 ohms on each channel, but I can still use my 8ohm drivers.