ericdube
New Head-Fier
- Joined
- Mar 29, 2010
- Posts
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- 11
I’ve been doing a lot of tube rolling in my Cary SLI-80 lately, and thought there must be an easier way to bias the left and right channels of this amp without having to plug/un-plug for each channel until you get it right. While it's not difficult to do, it's a bit more time than I'd prefer to spend when swapping between different pairs of tubes.
So I decided to build a dual channel biasing meter to substantially simplify the process. Using this setup, I can bias both channels simultaneously just by plugging in two separate cables (one for each channel.) The best part is that it’s all self-contained and uses a regular 9V battery to power it (which is externally replaceable along with the channel protection fuses.)
It will handle from 0-200mA’s since that’s all I needed for the SLI-80, however you can build one which will operate at a greater range if needed (0-1.999A would be the next range up.) Also, based on my testing, the accuracy seems to be identical to what my Fluke says so it's fairly accurate. The total price (including shipping) was somewhere around $55 for all the parts (not counting the time to build it), although I'm sure you could cut some corners here and there and assemble one for somewhere near $40 or less for all the parts.
Anyway, I just wanted something that was easy to read and relatively cheap which is why I choose this simple LCD-based design. I also looked at using two Analog meters (like the Cary meter), but they required a lot of depth for mounting and the decent analog meters where about twice the price of the LCD's.
I thought folks might like to take a look at what I did, and while it's nothing special, it does cut the time down considerably during biasing (which leaves me more time to listen and enjoy the music!
) While it was designed for a Cary amplifier, I'm sure it will work with other amplifiers that use a 1/4" phone jack for taking readings.
If anyone has any questions or needs a parts list, please let me know. Thanks!
Regards,
Eric
So I decided to build a dual channel biasing meter to substantially simplify the process. Using this setup, I can bias both channels simultaneously just by plugging in two separate cables (one for each channel.) The best part is that it’s all self-contained and uses a regular 9V battery to power it (which is externally replaceable along with the channel protection fuses.)
It will handle from 0-200mA’s since that’s all I needed for the SLI-80, however you can build one which will operate at a greater range if needed (0-1.999A would be the next range up.) Also, based on my testing, the accuracy seems to be identical to what my Fluke says so it's fairly accurate. The total price (including shipping) was somewhere around $55 for all the parts (not counting the time to build it), although I'm sure you could cut some corners here and there and assemble one for somewhere near $40 or less for all the parts.
Anyway, I just wanted something that was easy to read and relatively cheap which is why I choose this simple LCD-based design. I also looked at using two Analog meters (like the Cary meter), but they required a lot of depth for mounting and the decent analog meters where about twice the price of the LCD's.
I thought folks might like to take a look at what I did, and while it's nothing special, it does cut the time down considerably during biasing (which leaves me more time to listen and enjoy the music!
If anyone has any questions or needs a parts list, please let me know. Thanks!
Regards,
Eric
