One thing I have been meaning to mention. I know there isn't a lot of space but having the part # on the silk screen would be a big benefit. It would make trying different values a lot easier. This is DIY after all. 
The sound is quite good. Close to the DX Super A. Maybe not quite as open. I will try to hook up the TO-3 version along side this one so I can compare them. It will be interesting to see how they compare.
Blessings, Terry
The sound is quite good. Close to the DX Super A. Maybe not quite as open. I will try to hook up the TO-3 version along side this one so I can compare them. It will be interesting to see how they compare.
Blessings, Terry
OK, you saw it here first.
AX-14 on left and FX-14 on right. Virtually no difference in sound. I think the TO-3 version clips a little more gracefully. These amps are pretty high gain. I can get them into clipping with just my CD player. Each amp's PSU is a 200VA 30-0-30vac transformer with 3 x 4700uf per rail. The rails are +-44vdc at rest and will drop to 41V driven loud. I'm not sure but they may benefit from a stiffer PSU. I drove them pretty hard into 4 ohm and they drove it OK. Maybe lower rails would be better for 4 ohms. There is quite a boost in power when switching from 8 to 4 ohm. I may try them on +-36V and also on +-25V rails just to see what happens. It's always to know the limits. I'll keep you updated.
Blessings, Terry
AX-14 on left and FX-14 on right. Virtually no difference in sound. I think the TO-3 version clips a little more gracefully. These amps are pretty high gain. I can get them into clipping with just my CD player. Each amp's PSU is a 200VA 30-0-30vac transformer with 3 x 4700uf per rail. The rails are +-44vdc at rest and will drop to 41V driven loud. I'm not sure but they may benefit from a stiffer PSU. I drove them pretty hard into 4 ohm and they drove it OK. Maybe lower rails would be better for 4 ohms. There is quite a boost in power when switching from 8 to 4 ohm. I may try them on +-36V and also on +-25V rails just to see what happens. It's always to know the limits. I'll keep you updated.
Blessings, Terry
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+1I remember Mr. Miles mention that they can run with +/- 25V DC too
hey those heat sink look amazing man
Wow where we can find something like that
we can make an AX-14 class A version with that
My reply was in response to being asked "Can an alternative be swapped for BC5xx?"
I said don't use them for mirrors and the reason is poor performance at very low Vce.
Whereas the BC5xx has good performance at very low Vce compared to very many others.
That makes the BC5xx very suitable for mirrors.
Read Keantoken and get the message from the horse's mouth.
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OK, you saw it here first.
AX-14 on left and FX-14 on right. Virtually no difference in sound. I think the TO-3 version clips a little more gracefully. These amps are pretty high gain. I can get them into clipping with just my CD player. Each amp's PSU is a 200VA 30-0-30vac transformer with 3 x 4700uf per rail. The rails are +-44vdc at rest and will drop to 41V driven loud. I'm not sure but they may benefit from a stiffer PSU. I drove them pretty hard into 4 ohm and they drove it OK. Maybe lower rails would be better for 4 ohms. There is quite a boost in power when switching from 8 to 4 ohm. I may try them on +-36V and also on +-25V rails just to see what happens. It's always to know the limits. I'll keep you updated.
Blessings, Terry
Nice work,
Regards
If you use high-voltage transistors in the current mirror you may as well not use a current mirror, since they become like resistors at low-Vce, IE <1kR.
The BC5xx and BC3x7 however work better here than anything else I know of.
By the time the current mirror sees more than a few volts most of the amp will be burnt, so using higher voltage transistors here is not important.
The BC5xx and BC3x7 however work better here than anything else I know of.
By the time the current mirror sees more than a few volts most of the amp will be burnt, so using higher voltage transistors here is not important.
OK here we go, one more way. I build another couple boards using only the IPS and VAS. I'm driving a Slewmaster EF3 OPS. I just have it playing on the Baby Slewmaster right now so just running on +-50v rails. I swapped out the 2N5401 for KSA992A because I was out of them. I also swapped out the BC547/557 for BC 546C/547C for the same reason. I used MJE340/350 for the VAS. I've had it playing for about hour or two. Sounds very good. I hooked up the scope and got some screen shots of the waveforms. I'll try it through the 5 pair Slewmaster tomorrow with higher rails.
Blessings, Terry
Blessings, Terry
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He, he, I don't know. They were e-waste from something. Last year some time I was throwing out a bunch of stuff and decided to strip the boards of any useful looking items. Those caps have been laying in the bottom of drawer waiting for a place to go. They are .1uf 600V.
Particularly nice looking 10k and 20k test signals.
What setting did you use for the RF filter?
All resistors and capacitors are stock values except for using 100v caps for the ones that see the rails.
Hi Juan,
I was just looking over my boards as I prepare to attempt building the NX-14 amp and I noticed that the diode arrangement on your boards differ slightly from the schematic. The original shows D$ & D5 running from the output/NFB to the rails. On your boards the run from Q12 and Q14 emitters. I don't know if that matters but I thought I would point it out. I am attaching a schematic showing how the diodes attach on your boards.
Blessings, Terry
I was just looking over my boards as I prepare to attempt building the NX-14 amp and I noticed that the diode arrangement on your boards differ slightly from the schematic. The original shows D$ & D5 running from the output/NFB to the rails. On your boards the run from Q12 and Q14 emitters. I don't know if that matters but I thought I would point it out. I am attaching a schematic showing how the diodes attach on your boards.
Blessings, Terry
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