I am really amazed. It's the only amplifier ever that is dead quite. Absolutely no hiss and no hum with the ear totally in to the speaker. And I have made many amplifiers. I wonder why.
Bias 68 ma in each transistor pair.I'm glad you changed your mind
Describe your tricks you did to do so. What is the sound quality of the your Dartz amplifier from the audiophile point of view?
It's LF 353 in the servo. All transistors are on the same Aluplate. I have a downstairs and a upstairs. I use the circuit as told with 2.2 kohm, 100 nf and antparralelled rectifiers between the input ground for the two channels capacitor PCB. Two 500 w transformers 2 x 40 vac. Rectifiers for AC/ DC is Mur 3020.
I'm glad you changed your mind
I don't think he has changed his mind. The 108 is not a universal solution, even with the parallel outputs. It will never do proper bass per example. It will never be low distortion. If it suits your system and musical taste it can be very enjoyable but as with all other amps it just offers a set of compromises.
I remmeber once, Hervé, from Dartzeel, told in an interview that they modified the circuilt with the supercap, they got less drift and the sound changed to the better, so a win, win situation according to him.
What would you recommend as a universal solution, which amplifier?
Since I have an amplifier power supply in a separate box, the transformers 2 x 650 VA have leads every 5 V so they can have all voltages from +/- 18 V AC to +/- 50 V AC.
I can drive most amplifiers that way. I just need to make just the amplifier board and adjust it.
If you can list a few amps that are worth making I will be very happy to try them out when time allows.
Not a good idea as far as sound goes. The virtual ground provided by the DC offset network is much better, at least with the ground plane the original board uses. Combine several such improvements and you can run the sound this amp makes into the ground.
From the manual. Priceless
Yes, we now have servos which suck. Good news is for a nominal fee they can be disabled.
Are you shure Mr Deletraz is referring to the Servo boards?
I think he is referring to the Supercaps (but calls them a circuit).
This I know for sure:
There is confusion in the naming.
NHB 108 version A had physical XLR connectors but no input balance transformers, NHB 108 Version B added a balancing transformer behind the XLR connectors.
NHB 108 Version 2 is a totally different design, a downscaled version of NHB 458 and has no relays, no switches, no contacts in the entire signal path.
What I do not know is when a Supercap was added.
Also I do not think Dartzeel uses the Servo board, at all! That sub board is a Chinese design, an alternative to the Supercaps.
Last edited:
Ok then I will try with and without the 20 kohm
Thank you very much analog_sa. But it seems more "relaxed". The DC network never worked properly in my amp.
I have many Diy amplifiers and some very expensive. From 30 w class A to 100 w class A. And up to 700 W class AB. The sound is different on all. Got PS Audio Direct Stream Transport and Dac. Expensive Diy loudspeakers with Steen Duelund (DCA) parts. So if I don't like the Dartzeel I will sell it cheap to a friend or as a gift to family.
I don't believe such an amp exists. Speakers, taste, power expectations are all different. Taste evolves.
What used to represent a SOTA amplifier sound 10-15 years ago today is generally considered as sounding slow, undynamic and unexciting.
So disappointed this evening in Copenhagen. With signal -not shorted- as earlier there is huge hum. So have to work with it. Sound is to the dark side. One little speaker only wich I always try before using my expensive Duelund speakers.
One channel with no signal there is no hum. So maybe 4.7 - 10 ohm on the ground inputs.
One channel with no signal there is no hum. So maybe 4.7 - 10 ohm on the ground inputs.
Last edited: