I have my M2x completed with the Ishikawa input buffer. I hooked it up with a preamp from Doug Self (Elektor 2006) just to see if it was quiet and would make music. It was so compelling that I listened through a complete Daniel Hope album. It's a wonderful amp! Thanks to all who made this happen: Mr. Pass; Mark Johnson, and 6L6!
Now I just need to get my BA-3 preamp working. Right now it has a substantial hum, so back to the workshop. But the Self preamp is very nice.
Now I just need to get my BA-3 preamp working. Right now it has a substantial hum, so back to the workshop. But the Self preamp is very nice.
Last edited:
First test run today. After letting the amp run for a couple of hours on the workbench and set the offset I placed the amp in the living room. First thing I noticed was the hum..hmmm, not good. Sq is great but the hum was to loud. So back to the workbench again for more testing. I came to the conclusion the noisy 500va toriod is the biggest problem. It’s a relatively cheap one from Reichelt gmbh brand RKT type 500.18. I replaced the big toroid for two smaller 120va Amplimo toroids, one for the positive- and one for the negative voltage rail and the hum is now so marginal that it’s almost not hear able. My speakers are sensitive IMF TLS50’s
Not sure what to do now, keep it this way of go for a new better quality 300va toroid. Any advise?
Not sure what to do now, keep it this way of go for a new better quality 300va toroid. Any advise?
That's awfully hot for a transformer, I wouldn't run one there. I'm new, so take it for what it's worth.
EDIT: Did some searches here and looks like maybe 60 max, so I guess you might not be all that bad. I know mine are all much cooler than that though.
JT
EDIT: Did some searches here and looks like maybe 60 max, so I guess you might not be all that bad. I know mine are all much cooler than that though.
JT
Last edited:
That’s why I was thinking about a higher rated toroid. These two 120va’s where laying around in the Radioshack.
Although the transformers are about the minimum you can get away with, there is no real advantage in running a bigger transformer.
If it remains 50C or thereabouts and you have no hummm noise, I'd keep them, smile, and enjoy the music.
If it remains 50C or thereabouts and you have no hummm noise, I'd keep them, smile, and enjoy the music.
Also take into consideration if the case is closed, or open to air and don't forget about the increased ambient in summer time. 😎
What is max rail voltage for these, I know I know it depends on heat, but I don't see a spec on the print.
I'm using 22V dual trans and dual SLBs, unloaded I'm seeing 28.9V, but haven't dialed it down with the resistor yet. Give me something solid between XV and XV please.
Thanks
JT
I'm using 22V dual trans and dual SLBs, unloaded I'm seeing 28.9V, but haven't dialed it down with the resistor yet. Give me something solid between XV and XV please.
Thanks
JT
With that transformer and the standard output devices in the CFP, you will probably see about 25.5V. Since this is a ripple reducer, and not a regulator, the output voltage will drop under load. There isn't much adjustment available with that trimmer resistor. This is a little over the recommended voltage for some of the IPS boards. Those are the limiting factor. The bias circuit in the output stage will maintain about 1.3 A quiescent current regardless of the rail voltage. It's nifty that way.
I definitely recommend adding some bulk capacitance on the outputs of your SLBs. From 10,000 uF to 24,000 uF will make a noticeable improvement in the amp's control over your speakers.
I definitely recommend adding some bulk capacitance on the outputs of your SLBs. From 10,000 uF to 24,000 uF will make a noticeable improvement in the amp's control over your speakers.