[cel4145]

Not the normal type of question for this forum, but I knew that the people that know the most about plate amps hang out here

Two questions:


1) What is the impedance of the speaker level inputs on a plate amp? Specifically the kind that doesn't have any pass through for speaker level output?

2) Is it reasonable to run a pair of 8 ohm speakers in parallel with the sub--connected by the speaker level inputs--of a 2 channel amp?


Sorry for the oddball question, but here's the situation. I have an old HK 35 AVR that all the DSP burned out. Only the front L/R are left, and it still sounds great with a pair of speakers in a budget computer 2.0 setup. The HK can run 4 ohms no problem.


I'd like to hook a sub up to it. But since the sub line out is gone on the receiver and there is on the L/R out, that limits my options to budget subs that have speaker inputs and outputs, which is very limiting on the choices. On the other hand, if I can hook a sub with speaker level inputs in parallel with the speakers, that opens up my options a lot.


I've seen this kind of problem pop up in other budget 2.1 setups.


Thanks!

 

[garciab]

Yes, it is reasonable. It is typically a high-resistance, voltage divider network. Whether it has a pass-through is a matter of convenience, as the pass-throughs are usually equipped with a simple 6dB hp filter. I just looked at a Klipsch BASH amp schematic. It looks like the high level inputs will present roughly a 220ohm load. In the electronics world, any parallel, resistive load that is 10x higher can safely be ignored. Hope this helps.

 

[cel4145]

Cool. I was wondering if it would be that high. I wonder if the plate amps on all commercial subs are likely that high?

 

[garciab]

I'd guess so, since most are expected to be run with front mains as well. I wouldn't think they'd include high-level inputs, if they didn't make sure it would not be a significant load on your amp or receiver.