Comments on: Geek Pulse by LH Labs – unboxing

By: John Reekie

John Reekie — Wed, 13 May 2015 12:37:44 +0000

Hi Stefan, just to clarify, you can’t have the DAC after the power amp, with a digital-input amplifier, the amp itself is in effect the DAC. With regard to the miniAMP, it is I2S input, there is no DAC involved. I suppose one approach to the DDX would be to just get one first and see how it sounds. I haven’t read much about it. Good luck with your project, please do let me know how it works out!

By: Stefan Koza

Stefan Koza — Wed, 13 May 2015 11:24:32 +0000

Hi John, I was eagerly waiting your response, when I eventually found WordPress links in my spam box indicated that you had already replied. Thank you very much for your reply. I only wanted the DAC after power amp(s) solution if the eventual sound would be less coloured/purer for any reason. As I’m not an electrical engineer, I think I’ll go the DAC before power amps way. The tried way. The DDX320 look very interesting though. It’s a pity mini DSP have discontinued the miniAMP because I would like all the components to be from the same manufacturer (compatibility etc). If I understand correctly, the miniAMP was placed after DAC so I presume was analogue in and out?

By: John Reekie

John Reekie — Tue, 12 May 2015 08:49:48 +0000

Hi Stefan, assuming we are discussing DIY options (i.e. bare boards not completed amps), the only digital input amp option that I know of at the moment is the DDX320 from hifimediy. The discontinued miniAMP (from miniDSP) was also of this nature. Please note however that Class D amps are actually not digital amps, they are (typically) pulse width modulated amps. And as with any circuit, implementation is key. I’d be interested to know how you go if you do decide to try the DDX amps, but I do think that perhaps separating your project into DACs and (analog input) amps is a more tried and true path.

With regard to your other questions, the driver impedance does not matter, this is one of the advantages of active crossovers. I’m not aware of B&O making any digital input amps, but I’m not familiar with everything they do – I do know that the ASX2 modules in the miniDSP plate amps are analog input.

Hope that helps 🙂

By: Stefan Koza

Stefan Koza — Mon, 11 May 2015 08:16:13 +0000

Dear Mr Reekie,
I have come across you in a Linkwitz forum. I’m not going the Linkwitz way (as I have to digest the open baffle concept and hopefully listen to a pair). At the moment I’m going the sealed box way with 3 Dynaudio drivers (per channel). I’m not an electrical engineer so when I read some of the specialist forums, I don’t understand much.

What I wish to do is get the digital music source (from iTunes in my PC or iPod via Pro ject Dock Box, digital output) to my pair of 3 way speakers as simply as possible and without using passive cross overs and just one digital to analogue conversion. Just about all the configurations on the DSP challenge forum have the DACs between the DSP and the power amps. Being very curious I ask, now that there are digital amps, can the DACs be after the (digital?) power amps? This may be ridiculous, so please bear with me as I’m not an engineer. Do B&O ICE power of Denmark do this? And what about DSP based amplifiers which generate a PWM signal directly from a digital audio signal? My idea is to keep it all digital up to just before the speakers.

Finally, as you will most probably prove to me that my idea is not viable, if I go nanoDIGI/Fiio way, my drivers are, Tweeter 4 ohms, Mid 8 ohms, Bass 4 ohms. Will this difference in impedances be a problem?

I would very much appreciate your knowledge on these questions.

Kind regards, Stefan