TruePath: fine tuning

[chris4916]

Hi folks,

If you are as lazy as I am, [:I] you may want to use this small excel like sheet (in fact OpenOffice) to ease choice of resistors when it comes to fine tune your TruePath depending on preamp and power supply values.

http://christian.bonato.free.fr/Chri...elect_gain.xls

In case it helps...

Christian

PS: although I don't think it's totally wrong, I didn't perform neither extensive tests...

[thomaseliot]

Very good job!

We can work on it for further calculations:

Transformer, overcurrent, heatsink....

Lazyness never ends

[chris4916]

Adding overcurrent limitation should be quite simple (I'll do it, based on AMP2 inputs).

For transformer and heatskin, I'm not sure this is as easy...

power supply : for not too accurate figures, that's ok. Having said that, when it comes to take in account different potential implementations, I'm not sure simple but nevertheless generic excel sheet is useful.

For heatskin, any idea is welcome. Frankly, this is not my main concerns with class T but I may change my mind once Truepath will run :-)

Christian

[ChrisM]

Tend to agree - the tuning resistors around gain etc. are straightforward enough and the xls saves pounding away on a calculator - thanks for that.

Transformer and heatsink have more variables especially around intended use. For example i do not need oodles of power, 10 clean watts is fine (am looking at this amp cos its got that awesome PCB with room to make mods). So I am looking at a PS voltage in the low +/-40 volt area, 300va and will not be worrying too much about heatsinking.

So, anybody made the jump and bought one yet or better yet built one?

Chris

[chris4916]

well.... initial goal was only to avoid simulation generating some potential errors.
I'm not going (and not able) to develop any complex control, meaning benefit over manual computation is only marginal.

However, as a matter of game, I updated this file with some (small) improvements:
- new power supply section computes Vdc and filtering capacitor (very basic design) size
- result is used to fill up "gain" section that now shows (through conditional formating) whenever you are clipping depending on PS
- voltage and current limiting is spilt in another but not yet updated

Thinking further about power supply, assuming we restrict it to simple (standard) design, it should work quite well.

ChrisM,

I bought 2 Truepath. not yet built. I do not expect to be ready before this summer because I'm also working, in parallel, on my active filter and, furthermore, have to find solution for power supply (I would prefer SMPS). I'll let you know once it work.
I already built AMP5 that provides the 10 clean watts you are looking for (with 2x22V 300VA transfo in 8ohm speakers)
Straightforward to build

Christian

[ChrisM]

Thanks Christian, about to order a Truepath myself - maybe I will beat you to the build!

For the PS I will be going straightforward linear supply, toroid for +/- supply with separate tran for 10v and 5v. I will use a super regulator of some sort for the 5v supply. To me part of the beauty of the Truepath board is that the PS regulation is not on the main board and there is plenty of room to build your own regulated supply very close to the chip. It is a really awesome looking board - very welll laid out. I have just complete modifications to the regulation of the 5v supply on my dual mono Amp11 and (as per my post on the Amp11 thread) it was torture. the board has no room for mods and removing components often damages pads and tracks - thus the appeal of the Truepath.

I think an SMPS supply would be very hard to implement, +/- voltages as well as the 10 & 5v. I have 2 AMP6 one with SMPS, other linear supply. Hard to say which I prefer but maybe the linear. Amp6 and SMPS is a no brainer - used a laptop supply with 19v.

Am I pleased with Amp11 - you bet, its awesome! Do i need another Amp (ie a Truepath) - no, not really. Can I stop myself building and trying these amps - not at all!

Chris