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Dartzeel amp schematic - build this?
Dartzeel amp schematic - build this?
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Old 19th September 2020, 01:19 PM   #1631
domenico80 is offline domenico80  Italy
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ok.
I do not know what could or could turn in the brain of Mr. Delatraz, I just say that if you like the 108, you can replicate it as you see it and, afterwards, proceed step by step as I did.
Then you can go further, again as I / we did, another input voltage generator, 4 pairs, polarization changes. stabilized power supply etc etc.
but in the face of such work, then, I go in the other direction with another scheme where I can use LT3092 and have an objective increase in performance.
Ah, I forgot that the 2 signal ground resistors, the ones with the supercap, to understand, if I replace them with films and foils I have interesting results.
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Old 19th September 2020, 01:27 PM   #1632
domenico80 is offline domenico80  Italy
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@analog_sa
mah,
when I see
- similar extra Dartzeel variations
- the zener as a stabilizer of the entrance
- the Wima in series entry
- the ceramics as in my PCB, identical to the original, I am increasingly convinced that the 108 is a summary of a few but confused ideas.
But will it really like it?
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Old 19th September 2020, 02:28 PM   #1633
bogdan_borko is offline bogdan_borko  Serbia
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Quote:
Originally Posted by analog_sa View Post
And here is Damir's circuit as a possible replacement for the diamond.
And it works in real life without thermal runaway? I doubt that.
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Old 19th September 2020, 03:08 PM   #1634
analog_sa is offline analog_sa  Europe
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Dartzeel amp schematic - build this?
Quote:
Originally Posted by bogdan_borko View Post
And it works in real life without thermal runaway?
That is a pretty good question. You reckon having all the transistors sharing the same sink won't be enough? Because of the darlington?
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Old 19th September 2020, 03:26 PM   #1635
bogdan_borko is offline bogdan_borko  Serbia
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Quote:
Originally Posted by analog_sa View Post
That is a pretty good question. You reckon having all the transistors sharing the same sink won't be enough? Because of the darlington?
Output bjts without degeneration even with vbe multiplier for thermal tracking are very tricky task. Maybe with higher value of base stoppers like in the original circuit...
It sould be tried in real life with lot of experimentation.
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Old 19th September 2020, 04:26 PM   #1636
Paroxod4 is offline Paroxod4  Russian Federation
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The original dartsil is full of mysteries, what do we see? Capacitors Wima MKS, ceramics AVX CK (in Chinese clones, judging by the information, silver mica Philips), resistors are not the steepest MRS25, and I think the transistors are not very good, and they just put a supercapacitor. But judging by the reviews, it plays (original), and even as. And what was impossible at such a price to cram normal parts?
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Old 19th September 2020, 04:59 PM   #1637
marigno is offline marigno  Italy
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Quote:
Originally Posted by analog_sa View Post
And here is Damir's circuit as a possible replacement for the diamond.

I knew the original idea, base of Damir's topology, that I didn't know by itself. I'm not sufficiently skilled to place a comment on the modded diamond. For sure the collectors of front-end transistors, now, bring a portion of the signal that injects in the emitters of (originally) back-end transistors (here middle transistors), resulting in a subtraction, being in phase. I do not know if this is a good or bad thing but, perhaps, some of you do, please, share!
The main improvement by Damir, IMHO, resides in adopting one more stage between the diamond and the load, then the diamond's behavior improves for two reasons:
- the diamond is 1/hfe(last pair) influenced by the load with respect to the original condition;
- the output impedance in no more dependent from the CCSs (upon their limit - that is more than plenty in full driving capability for any load in this world) and you can use as many pairs as you want in order to lower it.
The VAS's behavior too improves of the same 1/hfe factor projected back by the diamond.
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Last edited by marigno; 19th September 2020 at 05:21 PM.
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Old 19th September 2020, 05:33 PM   #1638
analog_sa is offline analog_sa  Europe
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Dartzeel amp schematic - build this?
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Originally Posted by marigno View Post
The VAS's behavior too improves of the same 1/hfe factor projected back by the diamond.
Not really in the context of the 108, where the VAS is a discrete, high bias opamp. Loading is a very minor effect.

Here is the simulated distortion of the output stages alone. Both at 20W, 4ohms. Damir's has more than 3 times lower thd and the spectral distribution looks much healthier. Same bias current through the outputs.
Attached Images
File Type: jpg 108_20W_dist.JPG (110.9 KB, 100 views)
File Type: jpg Damir_20W_dist.JPG (88.4 KB, 97 views)
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Old 19th September 2020, 05:38 PM   #1639
analog_sa is offline analog_sa  Europe
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Dartzeel amp schematic - build this?
Here is the 108 output used in the comparison.
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File Type: jpg 108_output.JPG (83.4 KB, 99 views)
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Old 19th September 2020, 06:05 PM   #1640
marigno is offline marigno  Italy
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A lot better!
The two "patented" diodes placed to the bases of the second stage, paralleled to the Rs, do switch. So we expect some distortion from them. Try the simulation removing diodes and remaining at a power so low that the voltage on the Rs will be lower than diode's threshold. Then lower the Rs and try again to find the best distortion with the highest Pout. Forget about the idle bias, it is a simulation.
My NSCB has switching diodes too but their distortion should be a lot lower than the distortion from a switching transistor.
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Last edited by marigno; 19th September 2020 at 06:10 PM.
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