"To gain a more intuitive understanding of what we mean by “soft recovery” and why it's important, let's explore a rough analogy with velocity (v) substituting for current (I). Suppose you were considering a bungee jump from a structure 500 feet above the ground, and further suppose that you were offered two choices to arrest your plummet towards the earth: a 100-foot length of stiff rope or a 100-foot length of appropriately elastic bungee cord. Both will prevent your body from hitting the ground.
However, choosing the inelastic rope would, of course, result in a disastrous and probably fatal outcome due to the very high dv/dt change in your velocity as the rope suddenly becomes taut at the end of your fall. You would choose the elastic bungee, of course, as this would present a return to zero velocity at a dv/dt more likely to be survivable."
Fast, Ultrafast, Soft, Standard, Schottky: Selecting the Right Rectifier
April 21, 2017 by Lonne Mays
Fast, Ultrafast, Soft, Standard, Schottky: Selecting the Right Rectifier - Technical Articles
and the best part of the quoted and referenced article:
"Just as high dv/dt deceleration can damage physical systems via impact forces (because Force = m(dv/dt)), high dI/dt currents can cause high voltage spikes in circuits having inductance, because Voltage = L(dI/dt)."
However, choosing the inelastic rope would, of course, result in a disastrous and probably fatal outcome due to the very high dv/dt change in your velocity as the rope suddenly becomes taut at the end of your fall. You would choose the elastic bungee, of course, as this would present a return to zero velocity at a dv/dt more likely to be survivable."
Fast, Ultrafast, Soft, Standard, Schottky: Selecting the Right Rectifier
April 21, 2017 by Lonne Mays
Fast, Ultrafast, Soft, Standard, Schottky: Selecting the Right Rectifier - Technical Articles
and the best part of the quoted and referenced article:
"Just as high dv/dt deceleration can damage physical systems via impact forces (because Force = m(dv/dt)), high dI/dt currents can cause high voltage spikes in circuits having inductance, because Voltage = L(dI/dt)."
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Not necessarily. The subbing circuit can be placed where the diode bridges are used - this will reduce the noise to negligible levels.
But, the most important thing is to listen after each attempt to do anything with diodes/snubbers...
I get excellent results with standard diodes and only one capacitor placed across + and - on the bridge rectifier.
Nelson Pass has also written few articles saying why the standard diodes are good for analog circuitry... powered by standard 50/60Hz mains voltage.
I tried the "Quasimodo" that looked very nice on the scope, but I did not like the sound. The best sound I obtained was with a single 0.1uF BlackGate NX cap.
It would be really interesting to see if you like the noisier (old) amplifier better than the smooth-looking one, sound-wise. Please try, and let us know what the differences are.
Thanks for all your discussion...
Didn't understand at first "quasimodo"
Now I see that I will have to study this quasimodo idea.
Haven't listened to my new aleph j with the Hex Fred diodes yet...just going through and seeing that everything is as it should be before it goes into a system...
again, thanks for the reply's
Didn't understand at first "quasimodo"
Now I see that I will have to study this quasimodo idea.
Haven't listened to my new aleph j with the Hex Fred diodes yet...just going through and seeing that everything is as it should be before it goes into a system...
again, thanks for the reply's
Quick dumb question regarding mounting fets! I have some Keratherm insulators from DIY audio shop but do I need some sort of insulating bush for the screw to go through too? Also, I've seen some people use large washers on their fets and some just a screw. Any advantage to the large washer? Also, I'm guessing the M3 screw into the heatsink needs to be quite short..
No
Larger washers spread out the force over the package for a more even mount and thus heat transfer. Also, a split washer is recommended in addition.
Screw length should be no problem. A kit with various lengths may prove handy. Otherwise, you should be able to pick up appropriate ones fairly easily.
I’m very new to this and starting to get a handle on the idea of building the Aleph J. I am putting together a list of parts and materials needed for the build, and my question is what is the correct wire gauges for the build.
24+
24-
Out+
Out-
In+
Out-
And any other wired connections I’m missing.
24+
24-
Out+
Out-
In+
Out-
And any other wired connections I’m missing.
I would seriously consider buying the back panel kit if you’re thinking of using one of the chassis (4u/5u) from the Diy store. It has the rca input connectors, speaker terminals, power switch AND all the mosfet mounting screws and washers needed. I don’t believe it has the split washers though which you’d need to source separately.
@mpa - yes, if your 4U chassis has the pre-cut back panel, then I'd agree 90% with JSA1971. The reason I mention, is that I don't think the store has the proper IEC for the UK, and depending on what chassis you bought, you may have to cut all your own holes anyway.
So... YMMV. Either way, get yourself some proper M3 bolts, some big ol' fender washers, and some split washers at your local shop and you'll be in business for what you inquired about.
So... YMMV. Either way, get yourself some proper M3 bolts, some big ol' fender washers, and some split washers at your local shop and you'll be in business for what you inquired about.
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24+ 16 ga copper, PTFE (Teflon) insulation preferred to avoid melting
24-
Out+ see above
Out-
In+ thin ga solid core, such as CAT 5e twisted pair; thin coax is also Ok
Out-
Don't overthink the material used for wiring. The type of rectifiers and capacitors used in your PSU will have a much greater impact.
The big thing to plan ahead is wire routing and common (star) grounding. Focus on this.
24-
Out+ see above
Out-
In+ thin ga solid core, such as CAT 5e twisted pair; thin coax is also Ok
Out-
Don't overthink the material used for wiring. The type of rectifiers and capacitors used in your PSU will have a much greater impact.
The big thing to plan ahead is wire routing and common (star) grounding. Focus on this.
ALso DC ground (to go with +24V, -24V), power supply AC and safety ground, power supply wiring to rectifiers, etc - 16 gauge.
In addition to grounding and routing, twisting together speaker outs, signal ins, and power supply wires (AC hot and neutral together, DC +/- Gnd together) will help to keep noise/hum to a minimum.
In addition to grounding and routing, twisting together speaker outs, signal ins, and power supply wires (AC hot and neutral together, DC +/- Gnd together) will help to keep noise/hum to a minimum.
I believe the iec socket is dual fused (one for each leg or phase) and is rated for up to 250v. But you may be correct that it’s not UK spec. Here is the spec sheet as per the back panel kit link.
https://ch.schurter.com/en/datasheet/typ_6765.pdf
Just trying to help out, and trying to pay it forward. I’ve received a lot of advice and help with my projects, and am eternally greatful. My first build was in fact an Aleph J thanks to a little push from 6L6 (aka Jim) and Dennis Hui. I was petrified that the little knowledge I had wouldn’t be enough to get through the build, let alone a functioning amp. The help, advice and encouragement from the people on this forum from Nelson himself, 6L6, Zen Mod, Dennis Hui and Mark just to name a few is never ending and appreciated. Without the help I might not be sitting here as I type listening to my J. 😊
@JSA1971 - Beautifully said. My sentiments exactly. I just started into DIY earlier this year. Without the gracious help of this community, many of whom you've mentioned, there is no way I'd have been successful and had such a great deal of fun. I hope to pay it forward in any small way I can... technical advice may not be my forte. 
