Hi Charley
Sorry, didn't read the last paragraph of your post #19. Sounds like you have totally solved your hum problem with properly balanced tubes. If it was me I still would do my "fix" but sounds like you just need to buy more tubes!!! Lets get together again when everything is sorted out.
Sorry, didn't read the last paragraph of your post #19. Sounds like you have totally solved your hum problem with properly balanced tubes. If it was me I still would do my "fix" but sounds like you just need to buy more tubes!!! Lets get together again when everything is sorted out.
Bruce,
That is a great idea, although if I did go to 12V for the heaters, I might as well go for rectifying it for a few dollars more. Having seen the price of 12SN7s compared with 6SN7s, I am thinking that I could do a lot with the money that I would save doing this.
The Broskie PCB does allow for jumpering to permit use of 6V heaters with 12V supply.
What did you use to recify your 12V heaters?
Charlie
That is a great idea, although if I did go to 12V for the heaters, I might as well go for rectifying it for a few dollars more. Having seen the price of 12SN7s compared with 6SN7s, I am thinking that I could do a lot with the money that I would save doing this.
The Broskie PCB does allow for jumpering to permit use of 6V heaters with 12V supply.
What did you use to recify your 12V heaters?
Charlie
Sorry,
I do actually have 300K and 100K, which gives around 72V measured for 292VDC in. This is pretty much 1/4 B+
Now, I have this potential divider located across the final cap in my B+ supply. The 100K has a 0.1uF cap across it.
John Broskie suggested that I try putting the potential divider between B+ and the GND pad on the PCB. He has also suggested that I place two 1K 1% resistors across the transformer winding, and reference the join of the two resistors to 1/4 B+ He has further indicated that DC heaters are much better, and that 12SN7s have better bass resolution.
Bruce, if you read this, I am increasingly thinking that 12VDC heaters may be the best way in the long term, especially as I'll then be able to experiment with 12SN7s and 12SX7s as well as 6SN7s. I suppose that I could try running the heaters from the 12VDC power supply on my Heath PSU, or even a car battery. A lack of hum using these would indicate that my hum is resulting from Ac heaters.
Charlie
I do actually have 300K and 100K, which gives around 72V measured for 292VDC in. This is pretty much 1/4 B+
Now, I have this potential divider located across the final cap in my B+ supply. The 100K has a 0.1uF cap across it.
John Broskie suggested that I try putting the potential divider between B+ and the GND pad on the PCB. He has also suggested that I place two 1K 1% resistors across the transformer winding, and reference the join of the two resistors to 1/4 B+ He has further indicated that DC heaters are much better, and that 12SN7s have better bass resolution.
Bruce, if you read this, I am increasingly thinking that 12VDC heaters may be the best way in the long term, especially as I'll then be able to experiment with 12SN7s and 12SX7s as well as 6SN7s. I suppose that I could try running the heaters from the 12VDC power supply on my Heath PSU, or even a car battery. A lack of hum using these would indicate that my hum is resulting from Ac heaters.
Charlie
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