markusw wrote:If the heater winding has a center tap you simply leave it unconnected?
Yes, exactly.
Pay attention to Andy's thoughts as well though, as you have to ensure that you are careful with how you wire this, as you really don't want the DC ground coming into contact with the chassis!
paulster wrote:
Pay attention to Andy's thoughts as well though, as you have to ensure that you are careful with how you wire this, as you really don't want the DC ground coming into contact with the chassis!
Argh, just when I thought I understood it....
In Andi's example: if the heaters are referenced to gnd (via center tap or resistors) and the relay supply is floating I understand that accidentally grounding the DC side via e.g. the footswitch will cause troubles since both AC and DC side would be referenced to ground.
But if AC heaters are floating and only relay supply is referenced to ground why does it hurt if the DC ground gets in contact with the chassis?
I used a 100 Ohm resistor to connect my rectifier bridge to ground.
Like when you need a faux-centertap on the 6,3V, two 100 Ohm to ground.
My builds have two 6V relais that get about 5,7V.
They've never failed.
phsyconoodler wrote:Is there a way to wire up the filament supply to operate my existing 5v relays?
I realize that i'd have to rectify it,but how would I wire up a voltage regualtor?I don't have a 5v winding on the transformer I'm using.
Thanks in advance!
you don't need a regulator, since most relays can take a variance of a few volts (check your relay data sheets for max operating, pickup and dropout voltages). Just rectify and filter the filament voltage.
mbeldyga wrote:So if we use separate transformer (no CT) to get voltage for relays do we have to connect rectifier "-" with chassis ground or can it simply float?
It's usually quieter to connect it to the chassis, or you can get noise induced in the relay itself from the coil if it is floating.
Noise issues with using the filament taps to power the relays aside - I hear you Andy , can anyone comment on using the voltage doubler circuit shown in figure a) in the first part of the document below. I'd like to use this with 1/2 of the filament supply, mine is center tapped and the CT is grounded, the relays and relay supply would all be referenced to chassis ground. Looks like the first series capacitor is what keeps things from blowing up, and allows point 1 in the circuit to drift up and provide the voltage doubling...
What makes this interesting to me is that it uses the heater coil center tap which would provides the heaters with an AC ground reference and also kicks out lots of voltage to support a regulator for the relays. (A well regulated relay supply is essential to keep the noise at bay).
Has anyone tried this one?
"Let's face it, the non HRMs are easier to play, there, I've said it." - Gil Ayan... AND HE"S IN GOOD COMPANY!
The 12V relay power circuit shown in the schematic uses a voltage doubler and the filament voltage as a source. However the schematic doesn’t show the shunt diode across the coil. I’ve used this amp for over 50 gigs and No noise issues using this circuit.
What makes this interesting to me is that it uses the heater coil center tap which would provides the heaters with an AC ground reference and also kicks out lots of voltage to support a regulator for the relays. (A well regulated relay supply is essential to keep the noise at bay).
Has anyone tried this one?
Used that one before. Not in an amp though.
Worked fine, seemed like a solid supply. I regulated it and had more than enough Vin.
When I settle down to build my 100w ODS, I'll just do it like HAD did on #124.
Seems to be a well thought out amp.
Unless the PT I use has a 5v tap, I will just use a separate filament transformer like he did.
If you stray too far from the reservation you may end up with problems that are difficult to track down.
The 12V relay power circuit shown in the schematic uses a voltage doubler and the filament voltage as a source. However the schematic doesn’t show the shunt diode across the coil. I’ve used this amp for over 50 gigs and No noise issues using this circuit.
Bob,
Your circuit may work okay for a single OD relay, but it suffers from some the problems Andy describes - it has to be isolated from the rest of amp, no reference to a common ground on the coil side, poor regulation. If you cascaded a couple more relays, in particular a PAB relay or mid boost relay which are in more sensitive areas of the circuit, I bet it would buzz.
"Let's face it, the non HRMs are easier to play, there, I've said it." - Gil Ayan... AND HE"S IN GOOD COMPANY!
When I use the D'Lite method using the 5v rectifier taps,the relays work flawlessly,even when you add a third relay.
But using the filament supply,it was fraught with trouble for me.I ended up using a separate filament transformer and all the problems disappeared.
Using the filament supply added noise like you wouldn't believe.And the LED's in the foot pedal were hard to get working too.
Both of the other methods work perfectly with zero issues at all.
I don't have time to waste trying to make it work.
, can anyone comment on using the voltage doubler circuit shown in figure a) in the first part of the document below. I'd like to use this with 1/2 of the filament supply, mine is center tapped and the CT is grounded, the relays and relay supply would all be referenced to chassis ground. Looks like the first series capacitor is what keeps things from blowing up, and allows point 1 in the circuit to drift up and provide the voltage doubling...
