Hi, deerhunt! Here's what I think:
1. It would not be wise to replace BJTs with lateral MOSFETS without any other change, even though the Vgson is around 1.5V.
2. The easiest way to increase bias is to increase the value of the two transistors in the bases of the MJE's driving the output transistors.
3. Go for it! SQ would also benefit if you replace the resistors in the feedback with better ones.
4. Those supercaps would degrade the SQ, not improve it 😉
1. It would not be wise to replace BJTs with lateral MOSFETS without any other change, even though the Vgson is around 1.5V.
2. The easiest way to increase bias is to increase the value of the two transistors in the bases of the MJE's driving the output transistors.
3. Go for it! SQ would also benefit if you replace the resistors in the feedback with better ones.
4. Those supercaps would degrade the SQ, not improve it 😉
The front end is more or less a medium gain opamp, which without the feedback would provide ample gain for a phono stage. Blame it on the Revox engineers, Herve never touched this part, he just added the diodes.
Peter, I was not aware Revox designed the voltage amplification part. How interesting! Just wonder how Herve defended its patent he brags so much about 😀
Wow, looking at the Studer Revox A740 service manual it seems he even copied the crowbar circuit! However, A740 employs global negative feedback and the darTZeel doesn’t. Is that really the secret of darTZeel “magic”... or it’s just another marketing trick similar to the use of a single pair of output transistors.
Guys, someone tried the Dart with global negative feedback?
Guys, someone tried the Dart with global negative feedback?
I believe Herve has excellent ears and not much prejudice. A rare combination. He has obviously heard and been impressed by the Revox. How important is the diamond output and whether it is better than an EF i have no idea and am too lazy to try out.
As patents are defended: by paying the requisite fees. The circuit is patented in its entirety and there is also a claim the diamond topology itself is a "novel design".
Attachments
Hi Deerhunt,
No, you can't due an diamond output is not fit for lateral MOSFET. Using MOSFET as output requires to change all output stage components.
Cuong Nguyen,
No, you can't due an diamond output is not fit for lateral MOSFET. Using MOSFET as output requires to change all output stage components.
Cuong Nguyen,
@selfy and Walkalone
Thanks for your replies! I’ll skip the latfets!
Might have a look at those resistors later on!
Thanks for your replies! I’ll skip the latfets!
Might have a look at those resistors later on!
Looks like they stopped selling it. Before modyfiing check if it is working. Half off Chinese products do not work at all - oscillating
I see 3 pairs of endings per channel:
- check the zener value for polarization and relative resistances, the Chinese are always - optimistic -.
I see the servo circuit to limit the offset:
it is a circuit that makes the ending sound bad and is not needed if you use the 22millifarad super cap which is even better and even better if bypassed with a good model.
Better to attack the 4 transistors input to TO92 and check their selection: the Chinese do not do it and this circuit requires an accurate selection of all the active ingredients.
The 2 x 3.3 micro input caps play from Wima MKP, closed and dark
