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Vellerman K4700 fitting a Bigger Relay

J

juz400

pfm Member
I recently bought a big stack of K4700 kits,
Upon opening I was a more than a little dissapointed with the relays, I`ve had bigger bits of metal sticking out my finger!

Placing it between the tranisistors that are feeding it, there is barely a quarter of the metal in one leg of the MJW`s
Should I be using Maplins doorbell wire for my speakers?
EYPJVcQl.jpg


Ive been searching for Mods and not had too much luck, the one everyone refers to no longer exists
http://www.anidian.com/audio/deconstruct/k4700.shtml

I would like to add a couple flying leads for the 12v trigger and step up from this
http://www.velleman.eu/products/view/?id=17775&country=be&lang=en

to something more like this
http://uk.rs-online.com/web/p/non-latching-relays/2111269/

The coil resistance of the dinky is 360ohm and the biggy is 275ohm
Is it just a case of adding an 85ohm or thereabouts resistor to the trigger or is it a little more complicated than that.

I would also like to add an extra Ground/0v lead to the relay so that the speaker feed is connected to 0v on both sides when protect mode is on.
(see videos at bottom of this link for nightmare situation)
http://www.halfgaar.net/dc-protection-with-relays

Many thanks for your input
Justin
 
Try here

It doesn't tell you much. I'd be very interested in how to add higher spec relays (solid state?) to the boards.
 
Well, the pins that come with the kit, the ones that you suppose to be the input of your speaker cable, are also tiny. My solution was to make an additional pcb with my favorite Omron relays (IIRC G2Rs) and added also normal tabs for speaker wires.
I must admit though that Omrons legs are smaller than your transistors ones so probably the relays with the tabs you linked are good solution after all
 
chiily said:
Try here

It doesn't tell you much. I'd be very interested in how to add higher spec relays (solid state?) to the boards.
Click to expand...

Thanks Chiily,
Thats some useful mod info right there, solid state sounds interesting, depending on price.

ramona said:
Well, the pins that come with the kit, the ones that you suppose to be the input of your speaker cable, are also tiny. My solution was to make an additional pcb with my favorite Omron relays (IIRC G2Rs) and added also normal tabs for speaker wires.
I must admit though that Omrons legs are smaller than your transistors ones so probably the relays with the tabs you linked are good solution after all
Click to expand...

Thanks ramona,
I was going to use Hackers method from the HackerNap build thread for speaker connection, then I got hold of the things. :eek:
Ya know, I didnt even look at the Manufactor of the relays!
They are Omron G2R`s! :D
I was just looking for a clear case with tabs! lol
The Base that the Relay fits into has alot less metal to solder onto, Maybe just using wire and crimp tabs would be the better way.

There have been quite a few Hackernaps built over the years with the vellemans, admittedly 0 horror stories IIRC
It just seems a shame to put so much effort into building them, and there are some beautiful examples here on PFM!
Nice thick power cables, oodles of copper devoted to 0v and then to squeeeeze all that goodness through such a tiny device.

I may be talking complete Bollo* but its not much extra expense and my Focal W-cone Midbass drivers are unobtainium
 
and while you are at it, would you think that 1V DC is a little too much, especially when you have an active system ?
Is it possible to reduce this to say 500mV or 600mV ?
K700 schematic
 
Pete MB&D said:
I have a few 30A solid state relays if anybody wants to try out some.

Pete
Click to expand...

Can these be used as a substitute for a standard 12v SPST relay? I use four RF controlled relays for my motorised volume pot, but my wife doesn't like the clicking noise!
 
This site contains affiliate links for which pink fish media may be compensated.
Best update this thread with my experiment!

I got some of these relays from RS (211-1269) they have a similar resistance on the coil to the Vellerman supplied.
https://uk.rs-online.com/web/p/non-latching-relays/2111269/

411Zufo.jpg


and have wired in a couple flying leads from the relay coil connection and the Speaker Input
The Middle leg of the relay is connected to the Speaker output, the Left from the Amplifier leaving the Right Leg to connect to your GND/0v/Center tap connection. When no voltage supplied to relay, BOTH sides of your Drive unit are connected to 0v

qzUNr1J.jpg
 
juz400 said:
I recently bought a big stack of K4700 kits,
Upon opening I was a more than a little dissapointed with the relays, I`ve had bigger bits of metal sticking out my finger!

Many thanks for your input
Justin
Click to expand...

The standard K4700 relays are rated at least 10 Amps - more than adequate for an amp of up to 100 Watts IMHO, of course if you have a more powerful amp then you may need more current switching capacity. IIRC the Velleman instructions mention amps of up to 300 Watts.

I see above that solid state relays were mentioned, these have one drawback - in essence they are semi-conductors - the problem is that they cannot fully disconnect the input/output pair like a mechanical relay can. Definitely not recommended for mains switching.
 
graham-r said:
The standard K4700 relays are rated at least 10 Amps - more than adequate for an amp of up to 100 Watts IMHO, of course if you have a more powerful amp then you may need more current switching capacity. IIRC the Velleman instructions mention amps of up to 300 Watts.

I see above that solid state relays were mentioned, these have one drawback - in essence they are semi-conductors - the problem is that they cannot fully disconnect the input/output pair like a mechanical relay can. Definitely not recommended for mains switching.
Click to expand...

SS relays are designed for mains switching! They are not suitable for speaker switching though... BUT.. ones using power mosfets and easily DIY'ed ARE suitable and can apparently work very well indeed. It seems counterintuitive, and indeed I was wrong to announce on here a few months back (and after a full 30 seconds of thought) that it couldn't possibly work well... I was steered to examples showing that it not only works but in many ways is better than a relay.
There are a fair few compromises in selection of a suitable relay. The optimum choice for AC switching (the music) is not the best for switching high DC fault currents for a start. With amps of over 2-300W full fault current can cause an arc upon switching that can maintain fault current into the speaker and which will destroy the relay contacts.
Switching under power can also cause arcing and pitting of the contacts which can result in increased contact resistance and even distortion.
A special relay for speaker switching was available from IIRC Panasonic but I believe they are no longer available.
These had two sets of contacts in parallel, one for AC switching and one for DC switching, and they were arranged to open and close in sequence rather than at the same time.
I have designed a combination of mosfet switch with relay in parallel and timed so that the mosfets take all the power and do the heavy switching whilst the relay adds a short across the mosfets when they are already on in order to remove any suspicions of a P/N junction in the signal path (the mosfets alone seem to measure as pretty much the same as a relay anyway but this makes sure). I've only done it in simulation but I'm confident it will work as expected. I have no plans ATM to do anything with it... I've bigger fish to fry, plus people are used to paying like £10-15 for speaker protection and this, made in only small quantities one at a time, would be much more expensive and I doubt people would pay that much.
 
Solid state relays or back to back nmosfets with a photo coupler gate drive is the way to go.
Even the 10A relays above have feeble inductive load breaking capacity of 5 A at 30 Vdc, unspecified but much less at 50 Vdc
 
A while back one of my Hackers went DC while experimenting, the vellerman kit worked a treat but I also think the relay helped a bit here too.
None of the 3 switched points are making contact without power to the relay. The relay had quite nice little burn mark inside as there was a fair amount of DC going through it. (500va 100v DC at 5A?)
I just had this video come up in my Utube feed, when he shows inside the two switches to compare I had one of those face/palm moments.


There are a few fishes including myself that are using a single K4700 for monoblock duties.
Im only using One of the relay contacts for protection.
Most amplifiers fail with short circuited output devices and large DC supply dumped into your speakers.

So why not use Both relays for protecting the one channel output?
 
I am intending to use both sets of contacts in parallel in my new Hackernaps, must get back on to that.

Pete
 
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