K4700 in monobloc configuration (not bridged)

Kits Audio Hi Fi Projects
1

Hi,

I’m building a triple channel amp with completely independent power supplies (floating ground) using quad 405II/III boards (each channel output consists of Channel+ / ChannelGround where ChannelGround is independent of the other channels) and want to add K4700 speaker protection. I already bought two kits intending to use only half of the second kit for the third channel, but I see that the - is shared ground on the K4700 so I loose my channel independence.

What would the correct connection be for such a setup?

Many thanks for your help.

On second thoughts I should be more specific:

Each channel ground is based on the centre tap of its respective transformer, which is also grounded to chassis (and mains ground) through the following filter:

                  Chassis ground_   -diode+     _  Transformer centre tap
                 Chassis ground _   +diode-     _  Transformer centre tap

Mains ground _ Chassis ground _ 10R resistor _ Transformer centre tap - Channel ground
Chassis ground _ 100nF cap _ Transformer centre tap

Similar to the earth/ground arrangement here:

2

It would be best to use one K4700 unit per amp, to avoid all ground connections and troubles.

3

That sounds good, but what should the connections be?

4

It look like your amp is supplied with a symmetric supply, so please follow the instructions for symmetric supplies.

5

So for each channel:

Left (or right) PA -> AMP channel out
Right (or left) PA -> N/C

Left (or right) LS -> Speaker+
Right (or left) LS -> N/C

GND -> Channel ground

One K4700 for each channel and it doesn’t matter that one channel (one PA and one LS) on each K4700 is not connected to anything.

6

Yes, as shown in fig. 5
Make sure that the resistors on page 7 step 11 are NOT mounted.

7

Yes. Thank you. I see that they are not required for symmetric supplies.

Also, in answer to my intial question I found this suggestion on a French forum for keeping the floating ground integrity for each channel:

Simply mount a 100R 2W resistor between channel ground and the common ground of the K4700:

Is that a viable approach?