Hi all...
I faced with a concern. I have ordered some high priced transformer and one of them is the mains transformer for a tube HiFi-amp.
The order was placed in august last year and due to working abroad I haven't had the time to take a proper look at them but when I did I saw that the 50VAC tap was missing. I told the producer (who is, by the way, a very good guy) who told me there has been a misunderstanding in the communication between the two of us.
That said I still miss the 50VAC tap for the Bias circuit and as I see it there are two solutions but I don't which one is the best suited?
First I can tap from the HT+ and lower the voltage by using a resistor... I must confess that I am not sure about current draw... the amp is planned to use two pairs of 6550 power tubes. The resistor might be huge and/ or very warm? I have calculated to draw some 140mA - 150mA per pair.
Second is to get a small transformer with suitable secondaries to get the desired 50VAC. Problem with the transformer option is size which is limited in this build... it needs to be less that 70mm i diameter.
I have an idea if it works?... to get a small transformer with dual 24VAC secondaries and connect them in series... would that give 48VAC?... still a bit concerned about current draw to determine the VA of this small transformer? And still I have the issue with placing this small transformer inside the chassi... on the outside is not an option due to lack of space.
Thoughts?
Best regards
/John
I faced with a concern. I have ordered some high priced transformer and one of them is the mains transformer for a tube HiFi-amp.
The order was placed in august last year and due to working abroad I haven't had the time to take a proper look at them but when I did I saw that the 50VAC tap was missing. I told the producer (who is, by the way, a very good guy) who told me there has been a misunderstanding in the communication between the two of us.
That said I still miss the 50VAC tap for the Bias circuit and as I see it there are two solutions but I don't which one is the best suited?
First I can tap from the HT+ and lower the voltage by using a resistor... I must confess that I am not sure about current draw... the amp is planned to use two pairs of 6550 power tubes. The resistor might be huge and/ or very warm? I have calculated to draw some 140mA - 150mA per pair.
Second is to get a small transformer with suitable secondaries to get the desired 50VAC. Problem with the transformer option is size which is limited in this build... it needs to be less that 70mm i diameter.
I have an idea if it works?... to get a small transformer with dual 24VAC secondaries and connect them in series... would that give 48VAC?... still a bit concerned about current draw to determine the VA of this small transformer? And still I have the issue with placing this small transformer inside the chassi... on the outside is not an option due to lack of space.
Thoughts?
Best regards
/John