@Koifarm a big thanks from my side as well for sharing your design and PCB gerber files. I was able to stuff the board with parts I had in my stash this weekend and it work on first power up! I also used a linear power supply since I had that. A couple of questions:
- The only power transformer I had laying around was 120V AC. I used the board in SRPP config with 6N6P tubes and it worked just fine with the lower DC voltage. Does the higher DC voltage provide better output / optimal voltage for the tubes? I'm just curious to better understand the benefit of the higher voltage.
- I used a TDA1541A DAC with Lundahl LL1636 input transformers for I/V conversion and fed that straight into the tube output stage. I used a 50K load resistor on the secondary side of the input transformers. Not sure if this is the correct way to do it, but it sounded pretty good to me
Any advice on this would also be appreciated.
Good to hear, that your build works oke.
With about 160v DC the workingpoint is a little different. But when having a small input voltage from i/v and higher output impedance like 10 or 100k. It can work really good. You can try 200ohm for the cathode resistors.
It is normal to load input transformers but i can not advise what the best load is. If possible measure freq. response.
With about 160v DC the workingpoint is a little different. But when having a small input voltage from i/v and higher output impedance like 10 or 100k. It can work really good. You can try 200ohm for the cathode resistors.
It is normal to load input transformers but i can not advise what the best load is. If possible measure freq. response.
Hello Koifarm,
Thanks for the Gerber files also, just got my boards. It would be a good future upgrade to do a little shifting of components, and have room for the older-style DIP relay. It should be simple enough to overlay the larger footprint on the smaller one you have used, but I haven't compared pinouts.
That would alleviate the problems some are having in sourcing the smaller relay.
Gary W
Thanks for the Gerber files also, just got my boards. It would be a good future upgrade to do a little shifting of components, and have room for the older-style DIP relay. It should be simple enough to overlay the larger footprint on the smaller one you have used, but I haven't compared pinouts.
That would alleviate the problems some are having in sourcing the smaller relay.
Gary W
Current draw is about 30mA for the two tubes. And 1.7A current for the heater supply.
Thanks to all, i've purchased PCB from JLPCB, and many thanks for the gerber files.
Exceptional universal preamplifier, the only issue that i've have to solve is the temporized muting. In my execution i've to change BC337 with BC338 and change the base resistor from 1k to 560 ohm to trigger the relay. For me voltage across the relay coil only reach 2,6volt and cause the relay not to engage...
Exceptional universal preamplifier, the only issue that i've have to solve is the temporized muting. In my execution i've to change BC337 with BC338 and change the base resistor from 1k to 560 ohm to trigger the relay. For me voltage across the relay coil only reach 2,6volt and cause the relay not to engage...
But changing R21 could change time constant and so the time to trigger the relay?
Hi Jean Paul, i do not have done "part rolling". The solution was, in fact, the use of a transistor with higher Hfe. The protection diode is on its place
i'm referring to some relay that have the diode built in and coil have the right verse. The lower value of R21 was a tentative to increase Ib for the transistor. Anyway, thanks to Koifarm for the precious work that have shared to us
If it was the wrong polarity, wouldn’t it not function?
https://www.mouser.com/datasheet/2/212/1/KEM_R7002_EC2_EE2-1104574.pdf
https://www.mouser.com/datasheet/2/164/na-914632.pdf
https://www.mouser.com/datasheet/2/212/1/KEM_R7002_EC2_EE2-1104574.pdf
https://www.mouser.com/datasheet/2/164/na-914632.pdf
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