PSU for M49 build

[Greenie]

I am sourcing stuff for a M49 build and I am looking for a Toroidal power transformer with these specs, anyone with a link to one?

Toroidal power transformer: Secondaries 7-9VAC/100-120VAC.
230 V // 9 V / 0,5 A + 110 V / 0,05 A

 

[johnchantler]

I got mine from toroidy.pl as a custom order but they spec’d it for ,5 for both secondaries so I think it is bigger than it needs to be

 

[Greenie]

How much did you pay for it?

 

[johnchantler]

~56 euro each — this was for their 'audio grade'

 

[Murdock]

Yep, can also highly recommend them! Got all my Mic PSU transformers from them. Really nice guys, fast shipment, good quality and good prices.

 

[Greenie]

Since I am on to the PSU from the vintage microphone pcb guy. I have transformer for it that has 230v volt primary, but secondary output in series 230v 0.11 A and parallel 115v at .22A. What is to be used for the board? I read somewhere that the U47 uses only one voltage connection, so is that the case here? I have mainly been building tube amps, so the norm there would be different secondary voltages. (Voltasge in red on the pic, the green seems to be for the pilot light?

 

[Murdock]

Isn’t the 230v and 115v for european or US use? I think that’s your primary winding and you wire it either in series for European 230v or in parallel for US 115v.
And the other 230v winding is your secondary for B+?

 

[Greenie]

Isn’t the 230v and 115v for european or US use? I think that’s your primary winding and you wire it either in series for European 230v or in parallel for US 115v.
And the other 230v winding is your secondary for B+?

Seems about right. But seems a bit too simple?

 

[Khron]

Most tubes nowadays will need a (most often) 6.3v to power the heater filament.

 

[Greenie]

Most tubes nowadays will need a (most often) 6.3v to power the heater filament.

Do you think theres as need for an xtra transformer?

 

[Khron]

Well, unless the transformer you have now has a 6.3V AC winding, capable of delivering the 2-300mA most heaters need... And unless you've discovered some method of pulling that amount of energy out of the ether somehow... Yeah, you'll probably need an additional transformer

But since you seem to need this much advice about these things... And as much as all of us here, i'm sure, appreciate your enthusiasm... Is it really that great of an idea for you to be messing around with mains wiring?

 

[gyraf]

+1 for toroidy.pl custom power transformers

/Jakob E.

 

[Greenie]

Well, unless the transformer you have now has a 6.3V AC winding, capable of delivering the 2-300mA most heaters need... And unless you've discovered some method of pulling that amount of energy out of the ether somehow... Yeah, you'll probably need an additional transformer

But since you seem to need this much advice about these things... And as much as all of us here, i'm sure, appreciate your enthusiasm... Is it really that great of an idea for you to be messing around with mains wiring?

Don't worry about that, I am not "messing around", that's why I am asking. I have built 25 tube amps these later years, including Dumbles, Marshalls, Fenders, Trainwreck, Soldano, Hiwatt and more. So I am well aware of voltages and tube heaters. My problem is that the Toroidal transformer recommended for this build doesn't seem to have the heater voltage. Seems strange, so I am asking.

 

[rock soderstrom]

My problem is that the Toroidal transformer recommended for this build doesn't seem to have the heater voltage. Seems strange, so I am asking.

This is because the heating voltage is obtained from the B+. This is also how it was done in the original U47. The high wattage capacity of the specified resistors in the PSU also speaks for this. Normally, you don't need 5 watt types for 1-2mA current that a microphone needs.

It's honestly not clear to me what you're building. MK47 or M49 (which version?)?

The PSU schematic you provide is for this microphone. Here you can also see why the transformer has no heating coil.

 

[Khron]

The marking of that power supply reads "MK-47". Looks like it's meant for a U47 replica of some sort (which, indeed, had no separate heater voltage).

Not so much with the M49 though... I know the numbers are just 2 off, but...

Where exactly is THAT particular transformer recommended for this M49 build, though?

 

[rmburrow]

Clone a Neumann NKM type supply. I like the way the 150B2 (or American OA2 with socket wiring change) 150 volt regulator tube receives HT off the rectifier bridge through an 8 k resistor; this minimizes surge voltage on other components in the PSU and the mic. The heater DC voltage can be controlled using a 7806 regulator (for 6 v tubes) or a typical series pass transistor circuit. I use AA size rechargeable batteries in place of the old stabilytes. (You need 3 batteries in series for a AC701 heater, or 4 batteries in series for 6 volt heaters like the 5840, 6S6b, etc.). The batteries act like regulators in addition to high capacitance similar to large electrolytic effects. The heater voltage must be regulated (and perhaps crow barred for added protection) to protect expensive mic tubes.

 

[Tubetec]

Definately following that approach RM .
4 nicads might be even better for 4 volt heaters , with the addition of cathode connected centre tap and some extra passive LC differential smoothing , then any garbage picked up in the wires also cancels to a higher degree , Im not sure of the heater construction of sub minis , probably has reversed helix , Im not smashing any of my good specimens open ,
Anyone have a dud they can disect?

 

[Greenie]

I am sorry for the confusion, I am building two mic's at the moment, one M49 from Vamisound, and Vintagemicrophonepcbkit.com, with the twin 6028/408A Pentode Tube in parralelle. The PSU in question is for the D47. The PSU gtransformer is the vpt 230 110 from Triad.