Thanks prazza1, the tubes are both 6N6P. I bought a few of these about 5 years ago always planning on a preamp of some kind one day. This seemed the perfect use. I read another poster here used 6N6P so I thought I'd try them. One tube is the driver section for both channels, the other tube is for the cathode follower section. Since the cathode follower cathode is at about 135V, I elevated the heater for that tube 100V. I have not put it on a scope yet, but the output of the tube section should be about 40VP-P with a 2VRMS signal.
Thanks e_fortier. When I get this hooked up to my Altec 604 cabinets I'll post my impressions. I also want to run an FFT analysis and see what the distortion levels look like.
MEPER, the tube stage uses a 1uF output capacitor, so that connects directly to the junction of R1, R2, & R3 on the MoFo. I deleted the 2.2uF C1 cap from the MoFo. I don't think the tube stage output cap needs to be greater than 1 uF in this case. I'll know more when I measure the frequency response.
Thanks e_fortier. When I get this hooked up to my Altec 604 cabinets I'll post my impressions. I also want to run an FFT analysis and see what the distortion levels look like.
MEPER, the tube stage uses a 1uF output capacitor, so that connects directly to the junction of R1, R2, & R3 on the MoFo. I deleted the 2.2uF C1 cap from the MoFo. I don't think the tube stage output cap needs to be greater than 1 uF in this case. I'll know more when I measure the frequency response.
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Test results
I took measurements of my build. These measurements are through the tube preamp section.
The MoFo power supply voltage is 22V. Amp biased at 2A.
With 2VRMS input @ 1KHz:
28VP-P output or 9.9VRMS right before clipping
9.9^2 = 98/7 ohms (dummy load) = 14W
The plots are from Rightmark Audio Analyzer.
I had a thump at power-on so I installed a speaker delay relay. Problem solved.
Listening on my Altec 604D cabinets, sounds good, I like it. Plenty of detail. Separation good. Listening is so subjective it's really pointless to try to describe. It's amazing to me that 2 heat sinks that I pulled out of the trash, with IRFP250 already mounted on them, can sound this good. Really the only thing I had to purchase to make this work were the 2 chokes.
I took measurements of my build. These measurements are through the tube preamp section.
The MoFo power supply voltage is 22V. Amp biased at 2A.
With 2VRMS input @ 1KHz:
28VP-P output or 9.9VRMS right before clipping
9.9^2 = 98/7 ohms (dummy load) = 14W
The plots are from Rightmark Audio Analyzer.
I had a thump at power-on so I installed a speaker delay relay. Problem solved.
Listening on my Altec 604D cabinets, sounds good, I like it. Plenty of detail. Separation good. Listening is so subjective it's really pointless to try to describe. It's amazing to me that 2 heat sinks that I pulled out of the trash, with IRFP250 already mounted on them, can sound this good. Really the only thing I had to purchase to make this work were the 2 chokes.
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I may be wrong in recalling, but Herb Reichert once said (In Soundpractices, "Flesh and Blood"?)
"There is no such thing as too much iron"
I also have this impression. And yesterday I got some complaints from my neighbours about too much bass while I was enjoying my M
Fs.
Hyperacusis
That would be me. Since a few months I have a bad case of hyperacusis (don't know if that is the English word) in my left ear. I cannot listen to music at the moment: it hearts too much. I hope it will disappear again (but I doubt this).
That is why I don't check this forum as much as I used to....
That would be me. Since a few months I have a bad case of hyperacusis (don't know if that is the English word) in my left ear. I cannot listen to music at the moment: it hearts too much. I hope it will disappear again (but I doubt this).
That is why I don't check this forum as much as I used to....
I plan to build a low power mofo round 5w reducing psu to 9v and bias at 0.5A
at such low bias the irfp140 has low transconductance Yfs and with 8v high capacitance between G S and D
can you advise on a good mosfet (ideally P channel) with high transconductance and low capacity operating at 8V 0.5A?
at such low bias the irfp140 has low transconductance Yfs and with 8v high capacitance between G S and D
can you advise on a good mosfet (ideally P channel) with high transconductance and low capacity operating at 8V 0.5A?
FQP27P06
marconi,
this one could be a good for your need.
Suchbegriff: fqp27p06 | TME Germany GmbH - Electronic components
FQP27P06 ON Semiconductor / Fairchild | Mouser Deutschland
I have running it on "Mighty F5"- on 18VDC biased to 0,5A proper since any
days in test now.
The FQP28N08 is the N-Partner.
Give it a try if you like.
marconi,
this one could be a good for your need.
Suchbegriff: fqp27p06 | TME Germany GmbH - Electronic components
FQP27P06 ON Semiconductor / Fairchild | Mouser Deutschland
I have running it on "Mighty F5"- on 18VDC biased to 0,5A proper since any
days in test now.
The FQP28N08 is the N-Partner.
Give it a try if you like.