TGMC - a modular control pre-amplifier

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mjona

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Joined 2007
mjona said:
As far as local supply rail decoupling is concerned I see only one on the RIAA stage C3 at 100n and none at all on the buffer board.

If you want to short some supply line rubbish away from sensitive circuit input points - you would install them where there is a short distance between such and the decoupling capacitor. You can use a modern electrolytic for this - said Guido Tent an EMC engineer at Phillips 20 years ago.
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From post 255 - you should have researched this at the time in which case you would not be raising so many probing questions about the detail now.
 
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AndrewT

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Joined 2004
I went back to your post255 and the preceding post from Bigun said this:
Maybe my simulations are flawed somewhere but I'm not seeing any issue with PSRR for the shunt+phono combination. No need to add complexity. However, my criteria, admittedly a quick-think suggestion, isn't about channel separation.
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especially this sentence:
It's about keeping voltage drop from signal currents off the power rails and keeping them inside the amplifier.

Stability does require care and simple capacitance on the rails addresses it easily but of course output impedance increases with frequency but not to an extent that it's no longer attractive.
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nigel pearson

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Joined 2007
Funny thing it this preamp came from the NAP140 clone kits. I was always surprised how unwilling people were to do a better NAP140. Here we have something so removed from Naim as to make me wonder. Perhaps that's right and the right way to think about improving the NAP140. That is the classic Naim idea of nearest the front-end needs to be best.

Here is the PE Orion of the era. I suspect it is a better Naim. Not saying it should be considered. Just to say it exists. The amplifer has interesting ideas. 37V phono rail. Phono THD <0.1% 100-10000 Hz at up to + 30 dB. 0.005% @ 3mV 1kHz.

Happy Birthday.

A Paul Kemble web page - Practical Electronics Gemini and Orion amplifiers.
 
M

mjona

Member
Joined 2007
Bigun said:
Am I fired? and on my birthday too :eek:
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No, you have put in the effort to learn SPICE and EAGLE and the images of your hardware show you are capable of a professional result.

A decent library should have some of the books by Self if not Cordell. I have seen excerpts of Self's books are available online and suggest you check these out, and, if you like what you see, give yourself a birthday present and buy the hard copy.
 
Bigun

Bigun

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Joined 2009
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Monte McGuire said:
Aluminum electrolytics have a self-resonant frequency, like all other caps, but resonance looks more like a big, broad, non-resonant trough in its Z vs. F curve. IIRC, some 470µF 35V caps with cans around 7 x 15mm have self resonant frequencies around 400kHz - 600kHz, and caps with smaller cans will have SRFs around 1MHz or 2 - it's usually more of a function of the physical size of the cap, and less related to the capacitance value or voltage rating.
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Thanks Monte - have used a pair of smaller sized caps per rail.
 

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Bigun

Bigun

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nigel pearson said:
Has anyone used this? I am told it works better than Easy PC and Eagle.

Robot room copper connection free download (Windows)
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I chose Eagle initially because I use an iMac at home and Eagle has a freeware version. After becoming familiar with Eagle I'm lazy to change - and most choices would mean using a PC. I have a PC laptop somewhere but it's old. So I prefer to stick with Eagle simply because it works and is free. It's not the easiest to use if you need to customize parts. And the free version is limited in functionality which adds a couple of annoyances.

On an un-related topic: a free e-book on analogue design from TI recently made available: http://www.ti.com/lit/sg/slyt701/slyt701.pdf
 
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nigel pearson

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Joined 2007
Whilst not where we might want to go. No one seems to have any interest in batteries or whatever. A friend has lead acid types with 1 uF across them. I often doubt them any better than a LM317. We have them on hand to use and they are the chargers also. This makes me doubt much of what is said about all DC supplies. Why should a lead acid type with 1uF be less than perfect? The Lithium types even more so. A charger and change over switch as the road to perfection. No noise brought in from the mains if careful.
 
Bigun

Bigun

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That's an interest idea. One might not have selected shunt regulators if the idea was to conserve power, but overall power use isn't that high. A battery is rather like adding a very large capacitor. The challenge is likely space constraints as the chassis has already been purchased. Actually, it arrive recently. Needs a lot of holes cutting /filing to shape.
 
Nico Ras

Nico Ras

Member
Joined 2005
nigel pearson said:
Whilst not where we might want to go. No one seems to have any interest in batteries or whatever. A friend has lead acid types with 1 uF across them. I often doubt them any better than a LM317. We have them on hand to use and they are the chargers also. This makes me doubt much of what is said about all DC supplies. Why should a lead acid type with 1uF be less than perfect? The Lithium types even more so. A charger and change over switch as the road to perfection. No noise brought in from the mains if careful.
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Nigel, I have some experience with your suggestion.If you have an extremely low noise requirement , it is a good idea but there exist chemical noise although a very slow process - nothing is noise free.
 
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