Using monoblock amplifiers with SDA's

lilwaun

I am aware that you cannot use non-common ground amplifiers with SDA's, but there must be a work around for monoblocks. Any tips?

ben62670

A1 cable. What amps are you using? I am using Adcom mono blocks and you can tie the grounds with them. No special cable needed.
Ben

lilwaun

Normally I have been using an Adcom GFA 555mkII, but I recently picked up some really cool vintage Kenwood L-07M monoblocks that I wanted to try on the SDA's. The Kenwoods have a grounding terminal on the back of both, would it make sense to use a wire of some sort to connect them?

ben62670

Hopefully someone who knows will chime in. I do not know old Kenwoods. IF you can tie them together you need to tie the negative speaker terminals together, and you may also want to tie the cases together.
Ben

lilwaun

Thanks Ben. I have the original owners manual, but all it says about the ground connections on the back of each amplifier pertains to reducing or eliminating a 60hz hum if it occurs. I want to be sure I don't wreck anything.

Chris

ben62670

If you have an Multi Meter tie the two chassis ground connectors, and measure the resistance from the negative speaker terminals from amp to amp. Let us know.
Ben

heiney9

First of all which SDA's do you own? Only later generation models can use the AI-1 interphase. If your's can't no use in researching it.

I am not familiar with the old Kenwoods other than wanting to hear a pair myself. My best guess is they can't be strapped. Can't remember do those L-07M's use the Sigma Drive circuit Kenwood used in early Basic Series stereo power amps.

H9

P.s. I'm at work and don't have my SDA Compendium handy but list the SDA model you have and/or pics and I or someone else will get back to you.

P.s.s. Sigma Drive amps have an extra set of speaker terminals that run to the speakers as well. I've forgotten the theory but it has to do with damping or something along those lines.

heiney9

ben62670 wrote: »

If you have an Multi Meter tie the two chassis ground connectors, and measure the resistance from the negative speaker terminals from amp to amp. Let us know.
Ben

Of course this is wioth the amps powered off and I'd even unplug them.

lilwaun

I have the early SDA 1's with the two horizontal SL 1000's (silver face) tweeters. I'm not sure regarding your amplifier questions, but I recently downloaded a schematic and I do have the original owners manual. As I mentioned previously, there is a ground terminal on the back of each amp but not sure if this will accomplish the common-grounding I need. No extra speaker terminals. I'm excited to see how the Kenwoods sound with the SDA's, they are supposed to be a decent amplifier for their vintage.

Chris

lilwaun

ben62670 wrote: »

If you have an Multi Meter tie the two chassis ground connectors, and measure the resistance from the negative speaker terminals from amp to amp. Let us know.
Ben

I don't have a meter to test, but I will borrow one and give it try. I'll let you know the results. Thanks.
Chris

heiney9

lilwaun wrote: »

I have the early SDA 1's with the two horizontal SL 1000's (silver face) tweeters. I'm not sure regarding your amplifier questions, but I recently downloaded a schematic and I do have the original owners manual. As I mentioned previously, there is a ground terminal on the back of each amp but not sure if this will accomplish the common-grounding I need. No extra speaker terminals. I'm excited to see how the Kenwoods sound with the SDA's, they are supposed to be a decent amplifier for their vintage.

Chris

Using the AI-1 is not possible with those older SDA's. You will need to determine if those amps can be strapped to create a common ground. If you post the schematic here someone might be able to help, as well as doing the "meter" test.

If you have the schematic it might be best to contact Ken Swauger at Polk Customer service. He will have an answer for you.............or a place to get the answer.

I doubt Kenwood could be much help at this time.

H9