the normal fuse value for a motor or transformer is 3 * watts / voltage.
If you implement soft start properly then that factor of 3 can be reduced to near 1times.
Due to the way we specify our audio PSUs. I have found that the factor can even be less than 1. I commonly use 0.8 * VA / voltage without incurring nuisance blowing when the soft start is scaled to suit the transformer VA.
I've been looking for inside the official F5 thread but I couldn't found info about matching the jfets idss (2sk170 and 2sj74). Is there anything expected to gain, performance wise?
I have seen some BOMs that recommends to match them. I think that I have to find one 2sk170 and one 2sj74 with the same idss.
AFAIK, offset is adjusted by trimming pots, so I suspect that there should be small advantages in that sense.
Can anyone apport something to this?
I have almost all my components collected to start building, only need the jfets
Thank you very much to all,
Regards
I have seen some BOMs that recommends to match them. I think that I have to find one 2sk170 and one 2sj74 with the same idss.
AFAIK, offset is adjusted by trimming pots, so I suspect that there should be small advantages in that sense.
Can anyone apport something to this?
I have almost all my components collected to start building, only need the jfets
Thank you very much to all,
Regards
oh...
I was sure that from digikey there was a limit order of 1500 pieces for this specific resistor.
My mistake.
Thank you !!!
some hum (?)
I experience some hum, or at least I think it is hum (some small multiple of 50Hz). one has to put his ear to speaker in order to hear the hum, but the target speaker is a 106DB sensitive one and the noise will be much more noticeable there. I measured the ripple of the rails while one channel is attached and properly biased (~0.59 Volts) on a scope and it is ~150mV peak to peak and similar on both rails. when the input is shorted to ground there is no noise at all. when the ground crocodile of the scope prob is attached, the nature of the noise changes.
Has anyone else experienced such noise?
one more odd thing - the rectifier bridge of the positive rail is getting hotter (by hand) than the negative one. I don't know what that hints.
Shmulik
I experience some hum, or at least I think it is hum (some small multiple of 50Hz). one has to put his ear to speaker in order to hear the hum, but the target speaker is a 106DB sensitive one and the noise will be much more noticeable there. I measured the ripple of the rails while one channel is attached and properly biased (~0.59 Volts) on a scope and it is ~150mV peak to peak and similar on both rails. when the input is shorted to ground there is no noise at all. when the ground crocodile of the scope prob is attached, the nature of the noise changes.
Has anyone else experienced such noise?
one more odd thing - the rectifier bridge of the positive rail is getting hotter (by hand) than the negative one. I don't know what that hints.
Shmulik
Attachments
catching air
some reviewers use the tarm "air between instruments" when refering to sonic qualities. isn't the best way to catch that air is with no instruments to begin with? the rest follows.
seriously speaking, this hum haunts me. several of my DIY attempts ended humming. I even had a GainClone the was perfectly mute, and after returning from a friend cought up humming I failed to remove. I must be doing something profoundly wrong, but I can not spot it.
some reviewers use the tarm "air between instruments" when refering to sonic qualities. isn't the best way to catch that air is with no instruments to begin with? the rest follows.
seriously speaking, this hum haunts me. several of my DIY attempts ended humming. I even had a GainClone the was perfectly mute, and after returning from a friend cought up humming I failed to remove. I must be doing something profoundly wrong, but I can not spot it.
if you leave the input open circuit you have effectively added a high impedance aerial to the amplifier.
This is never the way you connect an amplifier to reproduce audio.
They are both F-5, just two different board layouts form two different sources.
The Daniels boards are more compact, the Cviller boards are a little larger.
There were originally some boards that later became available from Cviller as well, that had sufficient room for 4 out puts per channel, see his blog, and the group buy threads on both the Daniels and the Cviller boards for pics and building dicussion. They are both shorter than the gigantic F-5 thread, but it is certainly worth working through, take notes along the way.
Russellc
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