DAC project completed

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#383
SY said:
That describes most of diyAudio members.

I'd certainly like to see some backup evidence on your assertions about discrete versus IC op-amps. May I assume that you've done some controlled listening tests or have some measurements to support that conclusion?
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Good point SY. Although I must confess that I do tend to prefer discreet to opamps! Why? Because I have no real experience of opamps. What does of course come to mind is that even John Curl has not successfully defended his apparent preference for discreets 9see Blowtorch thread). So where do we poor mere mortals go for help?.😕
 
#389
The main difference between discrete design and op-amps is of course the theory of operation.
An ideal op-amp has infinite gain, which can be eliminated by NFB, which then ultimately changes into unity gain and infinite bandwith.
That is the basic idea of op-amps.
Then a lot of very clever engineers made a lot of circuitry to either eliminate the sensitivity for various external factors or internal behavior. Such as noise in the supplies, different loads, DC offset common mode rejection and even more.
Discrete circuits are not compensated from their births, so you have to pay attention to theese problems, which means solve them at the source rather than compensate later. That is both difficult and time consuming, and you will never reach the measured values for the op-amps.
But you arenow reproducing directly instead of compensated. You can also choose yourself if you want to utilise NFB or not. If no NFB is chosen, you´ll have to deal with DC stabillity either as caps in your signal path or as DC serco circuits. The DC servo is the better approach, but it is very difficult and time consuming to design. Our servo will not even compensate 1/100 Hz, if cut of frequency is higher, you hear it.
The upside of NFB is dynamic, powerfull, neutral and very realistic sound, the downside is difficult design and you´ll have to accept some diversion between units caused by tollerences in the components.
In the contrary NFB designs are very equal sounding, they are easy to design, they are very stable, often very low noise, the downside is restricted behavior when speaking of dynamics and transient response, and if NFB has been used as a linearising factor they are not sounding linear at all.
So one cannot damm NFB to hell, because it isn´t just bad, but NFB used the way you have to when using op-amps is probably the worst thing ever invented for audio.
Take a look at David Spiegels design, he knew excactly what op-amps could be usefull for, and I think he also knew why.
 
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#390
NicMac said:
Kurt von Kubik said:
the gear used for auditions are class A amps @ 40.000$ build on the same basic idea as our DAC is.
Hi KvK,
I had a look at your class A amps (http://profile.imageshack.us/user/kurt_von_kubik) and I was wondering where you spend the 40.000$? Could you clarify?
Nic
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The 40K was for both pre and poweramp, and as you obviously cannot see that for yourself, I think you ought to consider your future as hardcore DIYér participating in threads like ours. You are publically outwitted.
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#398
Bernhard said:
Well, I was just wondering as it seems you are trying to impress everybody with your ultimate $40k flagships.

The shortcomings of relays, anybody ? 🙂
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Well!
First we´ve been accused to try marketing something that is not for sale.
And now for trying to impress.
So lets just go on.
The amp you are looking at is THE AMP.
Discrete NFB design with DC servo´s, no caps in the signal path at all, and it delivers full power into 0,5 Ohms 60 dgr. off phase with ease from now to christmas, without any voltage loss.
In addition power bandwith from DC to 300KHz, that is indeed an amasing amp, and just the size of it is striking to the eye. Still it runs @ 55 dgr C.
It is a 100 Watts pr. channel class A amp @ 6 Ohms, designed as if it was intended for 1000 Watts pr. channel.
It is amasing what it can do to any speaker you can think of.
I still am amased of the job the engineer accomplished doing this power amp.
Luckily he was a nerd, but he was also clever, so he designed very reliable security for it, so if it ever might fail it will not eventually blow up the entire building.
Hooking this amp up with large speakers makes of course a predictable result, but the very funny thing is to hook it up with a pair of smaller ones. That really makes one look silly😀, its simply magic how this amp can handle a normally boomy bookshelf speaker.
 
#399
Kurt you and your partner must stop your poor attitude here, and stop attacking other products in an obvious effort to promote your own. We don't like members with aggressive attitudes and they tend to not last long..
This is an official moderator notice.

Variac
:captain:
 
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