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#491 | |
diyAudio Member
Join Date: May 2005
Location: in a house
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Quote:
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#492 | |
diyAudio Member
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Quote:
Also, is hot rodding not the same thing as lower noise in CSS for class A amps? It could increase the benefits of mutual inductance of the grounds as drain/shield? |
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#493 |
diyAudio Chief Moderator
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Think in terms of class A amp CCS loaded. HR ups gfs & lowers Zo. Ohmic division between SER & PAR sections increases. Rail AC modulation by load current swing decreases. That residual uV AC on rails also shows less THD. TO-247s mount easier and sturdier on case floor as sink. Silpad is enough to isolate. No weird grommets. Take HR heat gracefully. Need analogous TO-220s? Use IRF9630 & 630. On board sinks won't allow fanatical HR level though.
Disclaimer: DCB1 was "voiced" as a whole. I.e. the audio part and the psu part were meticulously evaluated and tweaked for values and devices to sound synergistic to my ears and taste. That's highly subjective, was done after the technical groundwork. Thus no suggestion was ever made that the psu part is the best mate for just any other preamp. Don't blame me if you will not like it in this preamp in other words. |
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#494 | |
diyAudio Member
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Quote:
How much current is the hot rod running? I'm wondering about transformer size. This design makes me more curious about resistor choices and bypasses (not that Gerhard has replied), for voicing. |
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#495 |
diyAudio Chief Moderator
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HR=Hot Rod gfs=MOSFET transconductance Zo=output impedance SER & PAR= series CCS circuit & parallel voltage circuit of the reg. 600mA bias is rich enough hot rodding in this reg. 200mA is passable.
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#496 | |
diyAudio Member
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Quote:
HR, hot rod, that one confused me, which is funny given how obvious it is. Got it all now ![]() |
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#497 |
diyAudio Member
Join Date: Aug 2006
Location: Texas
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The MOSFET gets faster at higher current. Also you take it out of subthreshold conduction which makes it less like a BJT and more like an FET.
According to simulation with accurate models, the regulator resonates around 5MHz. Higher current makes this much, much worse. So here is more info suggesting that people actually prefer resonant rails or even oscillating regulators in some situations. It also means the decoupling needs to have a certain amount of inductance to keep it stable, which means the ground plane could cause problems.
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The Kmultiplier rail filter! -=- The Simple Kuartlotron Superbuffer! Need something built, repaired or modded? PM me and ask what I can do! |
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#498 |
diyAudio Chief Moderator
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It does not resonate in real life. That one was designed in 2008 on the bench and tested with oscilloscope on the rails. Put together a prototype and measure it before proceeding if in any doubt. At least if concerned for possible trouble in another layout.
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#499 |
diyAudio Member
Join Date: Nov 2012
Location: Cognac
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Hello everyone!
This is what I offer and I think keep this provision of components, but a double-sided circuit is required. Now I will: - Move the RCA by following your proposals. - Import a supply. Regard's! |
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#500 |
diyAudio Member
Join Date: Aug 2006
Location: Texas
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I just threw one together on the breadboard. I just happened to have a single IRF630. Testing with an SMPS at ~75mA I see resonances at 20MHz (seems to be from the SMPS) and 1MHz.
__________________
The Kmultiplier rail filter! -=- The Simple Kuartlotron Superbuffer! Need something built, repaired or modded? PM me and ask what I can do! |
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