Common ground amp & SDA's

Bikerduck

Does anyone know if the Kenwood KA-801 is a common ground amp?
I would like to try out that amp with my SDA's but don't want to blow the speakers

Thanks

thsmith

+1, I have ran a TFM-25 with great results on my SDA-1Cs and currently running a TFM-45 with even better results. I would not pay more for a TFM35 orver a 25 and same for 55 over a 45.

Try to find one recently service with paper work for proof if possible. I highly recommend Rolland at Carveraudio for any service work.

heiney9

I see you have a KA901, probably the same design as KA801. If you have the amp already you can use a VOM to measure between the (2) negative speaker terminals (with the amp off of course). This will tell you if the amp has a common ground config.

H9

p.s. Why is it whenever someone asks a specific question about a specific piece of equipment people always chime in "you should get this". It gets old <end rant>

erniejade

I have a kenwood ka8006 top of the line from 1973 that amp sounds great!!!! The one you have is a bit newer then mine but should still sound as good if not better as it is a different design.

Now are you going to use the connect cable on your SDAs'? If not, then you do not have to wory.



If you do though, I thought that one was a dual mono... If people do not know on here, i would post on audiokarma. they have some big kenwood fans there.

Bikerduck

I did read that some int. dual mono amps are common ground but the 801 is not one of them.
I am getting tired to the point of selling the SDA's. I got 12 amps and can only use 2 M2a's with them, the rest is either not common ground or don't have enough wattage plus they are a pain to place right.
I like to switch things around

F1nut

Simple solution, build yourself an AI-1.

Oops, just noticed that you have 2A's, never mind.

george daniel

in that case, your only hope may be a tube amp,,say 40-75 watts of sweetness.

Schurkey

When I contacted Polk (about 1992) about using an Aragon 4004 with SDA 1B speakers, they suggested building a short jumper wire with appropriate terminations on each end to connect the black (-) speaker connectors together.

As long as the amplifier isn't bridged, you've then guaranteed that it is common ground.

Later, I contacted Aragon and they told me the "Dual Mono" 4004 is in fact separate on the positive side (including separate power transformers and storage capacitors for each channel) but the ground side was common--and so I then removed the jumper wire between the negative speaker posts.

davidfmartin

Correct me if I am wrong but I thought all you had to do to test if an amp is common ground is to take a multi meter and check continuity between the negative (black) speaker posts on the amp?

heiney9

Schurkey wrote: »

When I contacted Polk (about 1992) about using an Aragon 4004 with SDA 1B speakers, they suggested building a short jumper wire with appropriate terminations on each end to connect the black (-) speaker connectors together.

As long as the amplifier isn't bridged, you've then guaranteed that it is common ground.

Later, I contacted Aragon and they told me the "Dual Mono" 4004 is in fact separate on the positive side (including separate power transformers and storage capacitors for each channel) but the ground side was common--and so I then removed the jumper wire between the negative speaker posts.

Just to keep this factual.............not all non-common ground amps can have their neg terminals tied together. It's always best to contact the manufacturer to see if this is possible. There are even a few mono bloc's that can have their terminals tied, but ALWAYS check with the manufacturer or someone else with the knowledge that has done it before.

ShinAce

You need better than continuity, it needs to be a straight short for it to be common ground.

Adding a jumper could, in some cases, cause trouble. Not something you should try just **** and giggles.

Systems

ShinAce wrote: »

You need better than continuity, it needs to be a straight short for it to be common ground.

In some designs there may be a few tens of ohm's resistance .A resistor is sometimes added to isolate the grounds of both channels from each other and chassis ground.It would still be safe to strap the grounds.

bsoko2

The other choice is to build a "Dreadnaught" (http://www.polkaudio.com/forums/showthread.php?t=74472&highlight=dreadnaught). A DIY job is 150 or so and to have one built is more. ben62670 on this forum can do it if you want one.

Bill

danger boy

heiney9 wrote: »

If you have the amp already you can use a VOM to measure between the (2) negative speaker terminals (with the amp off of course). This will tell you if the amp has a common ground config.

H9

p.s. Why is it whenever someone asks a specific question about a specific piece of equipment people always chime in "you should get this". It gets old <end rant>

what kind of settings and what kind of readings will you get on the VOM? I need to find this out also in my amp. I don't know anything about VOM.. so please explain it like you were talking to a 5 yr old.

Systems

danger boy wrote: »

what kind of settings and what kind of readings will you get on the VOM? I need to find this out also in my amp. I don't know anything about VOM.. so please explain it like you were talking to a 5 yr old.

Use the ohm's setting and place the meters probes on the 2 negative binding posts.If the resistance reads less than say 20ohm's your good.

Systems

bsoko2 wrote: »

The other choice is to build a "Dreadnaught" (http://www.polkaudio.com/forums/showthread.php?t=74472&highlight=dreadnaught). A DIY job is 150 or so and to have one built is more. ben62670 on this forum can do it if you want one.

Bill

According to this poster it will not work with that speaker.

F1nut wrote: »

Simple solution, build yourself an AI-1.

Oops, just noticed that you have 2A's, never mind.

Schurkey

davidfmartin wrote: »

Correct me if I am wrong but I thought all you had to do to test if an amp is common ground is to take a multi meter and check continuity between the negative (black) speaker posts on the amp?

Correct as far as I know provided "continuity" means "very low resistance". Lower is better. Not everyone has an ohmmeter, though.

heiney9 wrote: »

Just to keep this factual.............not all non-common ground amps can have their neg terminals tied together. It's always best to contact the manufacturer to see if this is possible. There are even a few mono bloc's that can have their terminals tied, but ALWAYS check with the manufacturer or someone else with the knowledge that has done it before.

I respect your opinion; and in truth I am NOT an electrical engineer...but...if the amp is not bridged, how can it be hurt by a jumper wire across the negative terminals?

I'm not saying you're wrong. I just don't understand the problem if the amp isn't bridged. I won't state an opinion about strapping the negative terminals of two non-bridged monoblocks except to say that some folks have done it and not burned their houses down--so you're correct, it must work in at least some instances!

If the amps ARE bridged, there will be hell to pay if the negative terminals are strapped together!

Systems

Schurkey wrote: »

...but...if the amp is not bridged, how can it be hurt by a jumper wire across the negative terminals?

It shouldn't be a problem with any CG unit,even with amps using dual mono construction that have completely separate power supplys for each channel.

ShinAce

Designers and engineers almost always use the metal case as a ground or earth ground. There is the odd chance that this has not been done and the grounds are not common. For this exotic amp, you might be able to jumper the grounds, but do not short them to the case.

I'd guess that over 95% of amps are common ground with another 4% that can be jumpered.

Again, ditch the continuity and read resistance. Touch the probes together and you'll get maybe 0.2 ohms. This is the resistance of the probes. Now read between the negative terminals. If you get 0.2 or 0.3 ohms, it's common ground.

heiney9

Schurkey wrote: »

Correct as far as I know provided "continuity" means "very low resistance". Lower is better. Not everyone has an ohmmeter, though.

I am NOT an electrical engineer...

If the amps ARE bridged, there will be hell to pay if the negative terminals are strapped together!

I'm not either, but I do believe if an amp is truly a balanced design the neg terminals cannot be strapped in all instances. For instance Adcom 55xx series CAN be strapped since they are not common ground; Pass Labs "X" series amps CANNOT be strapped to create a common ground.

I won't state an opinion about strapping the negative terminals of two non-bridged monoblocks except to say that some folks have done it and not burned their houses down--so you're correct, it must work in at least some instances!

Yes this is correct as far as I know......some can some cannot.

If they are stereo amps run in bridged mono they CANNOT.....

Always check with the manufacturer first

H9

ShinAce

Schurkey wrote: »

If the amps ARE bridged, there will be hell to pay if the negative terminals are strapped together!

My prescription must be too strong.

To bridge two channels, you must first short the negative terminals and take your signal from the positive terminals. A bridgeable amp is already common ground.

heiney9

ShinAce wrote: »

My prescription must be too strong.

To bridge two channels, you must first short the negative terminals and take your signal from the positive terminals. A bridgeable amp is already common ground.

It is in stereo mode but certainly isn't as a mono block. How can 2 completely separate "black boxes" share a common ground when they aren't even connected to each other?

If you hook up bridged stereo amps and run them as mono bloc's with SDA's there will be damage to amp, speakers, or both. I guarantee it. I don't know of any bridged mono blocs that can have their negative terminals strapped together between the left and right mono bloc.

H9

Systems

ShinAce wrote: »

Designers and engineers almost always use the metal case as a ground or earth ground. There is the odd chance that this has not been done and the grounds are not common. For this exotic amp, you might be able to jumper the grounds, but do not short them to the case.

An amp will be common ground when the neg speaker terminals and power supply grounds are tied together.They may or may not be connected to chassis ground.
Even amps with full time bridged output stages ( not with a switch) can have a conection to chassis ground the difference being that the neg speaker terminal is not connected to the power supply or star ground so there is no problem doing so.

Systems

ShinAce wrote: »

To bridge two channels, you must first short the negative terminals and take your signal from the positive terminals. A bridgeable amp is already common ground.

The neg terminals will already be connected internally.But when you bridge you use the pos terminals only,so it is no longer common ground as both outputs will be hot.

shadowofnight

This wil help to visualize the outputs....

ShinAce

GV#27 wrote: »

The neg terminals will already be connected internally.But when you bridge you use the pos terminals only,so it is no longer common ground as both outputs will be hot.

I guess that's where I go astray, terminology. I would not speak of a bridged amp as common ground, since you're running it without a ground. A monobloc amp might still have a ground. However, I don't consider my bridged stereo amps as monoblocks.

edit: both amps shown above are bridgeable. The limitation within the second layout is that the input signal hasn't been inverted for one channel.

Marty913

Somewhere between post #20 and post #27 my head exploded.

Systems

ShinAce wrote: »

I guess that's where I go astray, terminology. I would not speak of a bridged amp as common ground, since you're running it without a ground.

Using a bridgable amp in non bridged mode, both of the negative terminals and power supply grounds will be at the same potential or common.
When you bridge it the negative terminals are still common(connected) but the negative half of the waveform is taken from the second channels pos terminal which is not at ground potential.There is a ground just neither of the output terminals are connected to it.
You cannot strap the outputs of two bridged amps together,but you can strap the outputs of two mono blocks that do not have bridged/balanced output stages because when strapped their grounds will all become common.:D

Bikerduck

I measured the resistance today between the 2 neg outputs and it came to 01.6 on the 200 ohm setting. According to some posters here, that would mean it's a common ground. How can that be?

Thanks
Donald

hearingimpared

Bikerduck wrote: »

I measured the resistance today between the 2 neg outputs and it came to 01.6 on the 200 ohm setting. According to some posters here, that would mean it's a common ground. How can that be?

Thanks
Donald

So would that be 1.6 ohms or 160 ohms?

Systems

Bikerduck wrote: »

I measured the resistance today between the 2 neg outputs and it came to 01.6 on the 200 ohm setting. According to some posters here, that would mean it's a common ground. How can that be?

Thanks
Donald

If you are getting 1.6 ohms then it is common ground.
As Shinace pointed out earlier the probe leads will have a small amount of resistance as will any wiring that may be used to connect the neg terminals internally.Touching the probes together will tell you how much of that 1.6ohms is in the test leads.