NHB-108 clone board is 1:1 and it sounds just fine for me. With original components this could be an amplifier to have. 😎
Yes, the original is well documented and easy to reproduce. The original components are nothing to write home about and can very easily be improved upon. Whether it is "an amplifier to have" depends on your speakers. It fails dismally into lower loads, which explains why the second series of the 108 has parallel transistors.
One more reason to have our European clone. What about Italian-Hungarian collaboration?
I repeat, if anyone is interested I can give the finished PCBs with all the stabilized voltages and argue their meaning and choices, otherwise I would not know what to say more
Some time ago analog_sa tipped me off that, in fact, darTZeel's "patented" voltage amplification stage is almost an exact copy of Revox A740 🙄
It turned out old Revox amp had three pairs of output transistors and the pre-amplification part was powered by separate stabilized power supply. Guess what? The A740's service manual even shows a SCR crowbar protection circuit 😀
So, instead of chasing ghosts in the "Hungarian schematic" I am more inclined to try the "source", but using Hervé's idea to take the feedback from the VAS instead of the output.
This is what I got (copied) so far in the simulator. I do not need more than 50W at 8ohms, hence the lower power supply voltages. Some resistor values can be easily tweaked to keep the circuit operating point the same.
Last year Mikey Fremmer visited again the darTZeel factory. There are some interesting things that could be seen in the video regarding the upgraded NHB-468s:
AnalogPlanet Tours darTZeel Factory in Geneva, Switzerland
One thing is certain - one can see a lot more transistors than there are in the "Hungarian" version.
😎
It turned out old Revox amp had three pairs of output transistors and the pre-amplification part was powered by separate stabilized power supply. Guess what? The A740's service manual even shows a SCR crowbar protection circuit 😀
So, instead of chasing ghosts in the "Hungarian schematic" I am more inclined to try the "source", but using Hervé's idea to take the feedback from the VAS instead of the output.
This is what I got (copied) so far in the simulator. I do not need more than 50W at 8ohms, hence the lower power supply voltages. Some resistor values can be easily tweaked to keep the circuit operating point the same.
Last year Mikey Fremmer visited again the darTZeel factory. There are some interesting things that could be seen in the video regarding the upgraded NHB-468s:
AnalogPlanet Tours darTZeel Factory in Geneva, Switzerland
One thing is certain - one can see a lot more transistors than there are in the "Hungarian" version.
😎
Attachments
many transistors in an open loop often involve as many problems: selection can become challenging
But isn’t that the main goal with the zeals? To avoid the global negative feedback 😉 Well, each approach has its downsides.
darTVox is cracking me up 😀
But why the ugly inductor at output? Do you think it is compulsory?
But why the ugly inductor at output? Do you think it is compulsory?
It depends on which version you are looking at. Shany's physical implementation appears to be using 8 transistors per rail.
I have no need for a kilowatt as well but do need 2ohm operation. Will see what the simulator thinks of 4 transistors per rail of 60v.
And yes, it will definitely be the based on the early, pre-cascoded Hungarian version with huge thanks to Shany for making it public. The open loop gain of the VAS is about 1.5 times higher than the Dartz 108 with a correspondingly lower THD and a much prettier spectrum.
I am not counting the power transistors. By “Hungarian” version I mean the one that could be seen at the screen in one of the previous videos from Dartzeel’s factory visit. I have my doubts it is genuine. Which one is the Shany’s version?
I had built an NHB-108, the soundstage, mids and high are nice, comparable to my F5, but the bass was too loose, I didn't like that.
But bass quality depends a lot of the interaction with the speakers used.
I also had a hum problem with the Dartzeel, probably due to a ground loop since I used a single transformer and PS for both channels.
Now, I have an Alpha4R playing very nicely, soon to be upgraded to the Alpha Nirvana.
Another amplifier that I'm building is the SimpelStark,
the SimpelStark is also without global feedback.
I suppose you mean schematic ?
Vzaichenko has posted version 1.1 of his amplifier,
the current version is 1.3, that schematic 1.3 is not public.
Vzaichenko has posted version 1.1 of his amplifier,
the current version is 1.3, that schematic 1.3 is not public.
That must be the worst opinion anyone has ever expressed of the Dartz. But of course we all have different tastes.
There are many, lately with a cascode. The version that appears to follow the 458 is in post #584
Perhaps. I have only tried the original. F7 was significantly better but still could not drive any of my speakers properly.
Group buy PCB 458?
Hi I trew out all my equipment for PCB production some months ago. Will it be possible with a group buy of PCB,s?
Hi I trew out all my equipment for PCB production some months ago. Will it be possible with a group buy of PCB,s?
PCB complete with components or only pCB.
Example, in the Chinese clone PCB there are errors on the mass turns