Okay, so it would make sense to find something closer to 0-165V then I guess. Maybe I will just go for that ebay R-core..
Yes, but I'd avoid the RCore
They have again just been reported to me as being out of spec.
lol.. This is becoming more difficult than I thought to find an appropriate power transformer in Canada.
Maybe I will contact Plitron to see what they would charge to do a custom wind for me. I believe they're in Canada.
If I am asking for a custom wind I might as well get exactly what I need.
Does it make sense to have a touch of headroom built in?
I'm thinking, should I ask for one with the following secondaries:
0-165V @ 150mA
9.5-0-9.5 @ 1.5A
?
Maybe I will contact Plitron to see what they would charge to do a custom wind for me. I believe they're in Canada.
If I am asking for a custom wind I might as well get exactly what I need.
Does it make sense to have a touch of headroom built in?
I'm thinking, should I ask for one with the following secondaries:
0-165V @ 150mA
9.5-0-9.5 @ 1.5A
?
Last edited:
It's usually the case that this build needs a custom Traffo, as no one yet has linked to an off the shelf option.
Torroidy.pl will ship to Canada, as will Audiophonics, but they take 2 months minimum.
There are eBay sellers who will custom wind transformers too. I use "Pinshule" and they have been superb every time. However, that would be an EI transformer and needs to be 10" from the Phonostage or you'll get hum.
I am going to contact Plitron in Canada. Given the discrepancy I've seen between winding recommendations, I just want to confirm what I should ask for.
Is this ideal:
0-165V @ 100mA
9.5-0-9.5 @ 1A
should I get more VA headroom built in?
EDIT: Crap looks like they only do larger orders.. Still want to confirm what windings are absolutely ideal if I'm getting a custom job done.
Just order this:
Primary (your voltage)
Sec1: 175v @0.1A
Sec2: 9.5-0-9.5v
It's got bags of headroom anyway, so no need to go further.
Honestly, that's all you need!
I'm just concerned about my mains variation. During the day it measures exactly 120VAC, at night it measures 124VAC.
If wound for 120VAC mains it would measure correct during the day, but 181VAC & 9.8-0-9.8VAC at night.
I'm not used to having such a narrow window to work with. What is the lowest AC voltages that this circuit will operate correctly at, and what is the highest?
I don't think we've ever found out!
If you have peaks like that, do 165v to be on the safe side.
Okay. As long as that won't put me too low.
And I suppose for the heater winding, higher AC voltage will just mean more heat dissipated in the rectifier / regulator, so that shouldn't be a problem right? The output for the tube heaters is fixed because of regulation?
And I suppose for the heater winding, higher AC voltage will just mean more heat dissipated in the rectifier / regulator, so that shouldn't be a problem right? The output for the tube heaters is fixed because of regulation?
Yes, 165v is what mine is running with, as is around 20 others, so I have no concerns at all about that.
And yes, more heat...*should* be ok, but as I say we haven't really ventured off the spec for Traffo purposes and technically @Vivant would be better placed to answer rest lol
He'll chip in when he sees this, I'm sure
There is a very easy way to accommodate a higher voltage on the HT, although if it is only as high as 180V that is OK.
The circuit has a good tolerance to the range of HT that can be expected with mains variations.
My particular build uses a 155V transformer, this is on the low side and needs a change to the bias potential divider feeding the first stage.
What transformer(s) do you have ready access to?
The circuit has a good tolerance to the range of HT that can be expected with mains variations.
My particular build uses a 155V transformer, this is on the low side and needs a change to the bias potential divider feeding the first stage.
What transformer(s) do you have ready access to?
I just wanted something off the shelf that I could get relatively quickly, so I'm looking at these two Antek power transformers.. And while they're rated much higher than necessary for VA, they're the closest to the voltages I need, and the pricing doesn't change much for 50VA vs 100VA from Antek.
Anyways I'm looking at this for the HT:
AS-1T175 - 100VA 175V Transformer - AnTek Products Corp
With 120VAC mains, it shows that the VAC output is 181V @ 0mA. And 168VAC @ 560mA.. So I would guesstimate that maybe I'd be around 180VAC with the low load that this circuit uses. This would then be about 186VAC when my mains is at 124V. I'm worried that's too high.
For the Heaters I'm looking at this:
AS-1209 - 100VA 9V Transformer - AnTek Products Corp
With 120VAC mains, it shows that the VAC output is 9.5 - 0 - 9.5VAC @ 0mA.. So probably somewhere between 9 and 9.5V realistically with my mains variation with a bit of a load on it. So this I think would work okay.
What do you think about using these two power transformers for my application?
Anyways I'm looking at this for the HT:
AS-1T175 - 100VA 175V Transformer - AnTek Products Corp
With 120VAC mains, it shows that the VAC output is 181V @ 0mA. And 168VAC @ 560mA.. So I would guesstimate that maybe I'd be around 180VAC with the low load that this circuit uses. This would then be about 186VAC when my mains is at 124V. I'm worried that's too high.
For the Heaters I'm looking at this:
AS-1209 - 100VA 9V Transformer - AnTek Products Corp
With 120VAC mains, it shows that the VAC output is 9.5 - 0 - 9.5VAC @ 0mA.. So probably somewhere between 9 and 9.5V realistically with my mains variation with a bit of a load on it. So this I think would work okay.
What do you think about using these two power transformers for my application?
No problem. Once built measure the voltage on the first HT capacitor, anything up to 250V DC is OK. If higher let me know and I'll calculate the required resistor.
Okay sounds great. Thanks! Is this 250VDC before I've inserted tubes? Or with the tubes in?
Also, just curious, for the heater power supply, rather than the 100VA version, if I got this 50VA 9 - 0 - 9V version AS-0509 - 50VA 9V Transformer - AnTek Products Corp
Which lists the voltage output at 9.4 - 0 - 9.4V @ 0mA current draw and 8.7 - 0 - 8.7V with 4.3A (So likely right around the 9 - 0 - 9V range with the current draw I'd have from the tubes), would that be okay? How low can this AC voltage be for the heater circuits to operate okay?
The 50VA heater transformer sounds ideal, there is a bit of headroom on the regulator circuit.
The 250V DC shouldn't be much different with tubes in or out, generally it is around 245V with transformers that have been used. Just want to check it isn't a lot more than this, there is no problem with the rectifier and capacitors, any extra voltage can be dissipated in the Fet filter by adding a resistor across the Fet filter cap.
The 250V DC shouldn't be much different with tubes in or out, generally it is around 245V with transformers that have been used. Just want to check it isn't a lot more than this, there is no problem with the rectifier and capacitors, any extra voltage can be dissipated in the Fet filter by adding a resistor across the Fet filter cap.
Great! Thanks for the info. It'd be much nicer to go with that 50VA version, so I'll do that. And I guess depending on how this goes, this is a ready to go off the shelf option. It does require extra space for rather large transformers, and 2 instead of 1, but not a bad trade off in my opinion.
Well... Another question has arisen in my mind. I just re-read through every post in all the threads, and I don't think I missed what I was looking for.
With regard to loading, in this post Bigbottle MM/MC Hybrid Valve Phonostage PCB it was mentioned that you could either use resistors or capacitors to get your loading correct.
And in this post Bigbottle MM/MC Hybrid Valve Phonostage PCB it was mentioned that by default there is 150pf of capacitance in the circuit.
Now, if I wanted to increase this capacitance as well as use a loading resistor, would I just connect both a resistor and capacitor in parallel over each of the Load connections?
Ideally I need 220pF & 40K.
Lastly, as far as a ground connection for my turntable, is this just as simple as connecting a wire from whatever connection terminal I install in my chassis to either the InR or InL negative connection?
With regard to loading, in this post Bigbottle MM/MC Hybrid Valve Phonostage PCB it was mentioned that you could either use resistors or capacitors to get your loading correct.
And in this post Bigbottle MM/MC Hybrid Valve Phonostage PCB it was mentioned that by default there is 150pf of capacitance in the circuit.
Now, if I wanted to increase this capacitance as well as use a loading resistor, would I just connect both a resistor and capacitor in parallel over each of the Load connections?
Ideally I need 220pF & 40K.
Lastly, as far as a ground connection for my turntable, is this just as simple as connecting a wire from whatever connection terminal I install in my chassis to either the InR or InL negative connection?
Last edited:
R4P and C3P are to do with powering the relays, so no relays and they aren't needed.
They are between the relays at the input end of the board.
Yes you can connect a resistor and capacitor in parallel for the loading.
Read further in the builders thread and you will see a diagram showing where the two links are required per relay, for MM only.
They are between the relays at the input end of the board.
Yes you can connect a resistor and capacitor in parallel for the loading.
Read further in the builders thread and you will see a diagram showing where the two links are required per relay, for MM only.
Somehow I missed it the first time, I editted the question about the diagram out of my post once I found it. Sorry about that.
I am also curious now though about the loading, you said built into the circuit is already 150pF of loading for MM operation. Is there any built in resistive loading with MM operation? Or if I wanted 40K load I would use 40K resistor?
Last edited: