The Kuartlotron - keantoken's simple error-correction superbuffer

[bkdog]

Originally Posted by jean-paul

With the DCB1 someone came up with running the MOSFETs at very high currents (so called "hotrodding"). This was supposed to sound better. I haven't tried but knowing that the circuit only draws a few mA I never even bothered. In my Mezmerize samples I used small heatsinks in standard config but let's say the MOSFETs only get lukewarm at standard current even without the heatsinks. Maybe Salas can give advice on suitable TO220 devices. I would add TO220 heatsink pads for heatsinks that can be soldered on the PCB in case you will use TO220 MOSFETs.

Jean-Paul, I can confirm that running the DCB1 "hotrodded" with higher current in the supply does sound better. I assume it is because of a lower PSU output impedance. This is not the thread to go into it in any detail.

[Destroyer OS]

Originally Posted by jean-paul

Please compare to using V8 engines in cars Horrendously oversized, polluting and uneconomic but they are still used in some countries.

Says the Parisian to the Texan...

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?

[Salas]

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.

[Destroyer OS]

Originally Posted by Salas

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.

I need a legend for all the acronyms here. If I'm not mistaken you said what I was thinking.

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.

[Salas]

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.

[Destroyer OS]

Originally Posted by Salas

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.

Nice, I could still use transformers I like.

HR, hot rod, that one confused me, which is funny given how obvious it is. Got it all now

[keantoken]

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.

[Salas]

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.

[Project16]

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!

[keantoken]

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.