Is VFet an internet influencer thing that makes no sense at all?

Jump to Latest
#41
rottalpha said:
yes, you are rightfully worried about the B-1. Unfortunately, the B-1 is the most complex rebuild and most difficult to source main filter caps for. Yamaha chose a dual-cap for filter caps and those are difficult to replace. Sony did too, for the TA-8650 and for the big dog, TAN-8550, but Sony uses a single dual-cap for main filter / PSU and the B-1 has two of them..so also a more expensive replacement.

Your B-2 also has a difficult issue to address (and still keep all functionalities of the unit), which is the front selector assembly.

The Sansui has a fairly simplified circuit and parts that are easy to replace. With the Sansui, a good old recap will get you 90% to where the amp will sound as good as new. That is a sweet sounding amp.

As far as the Sony v-fet amps sounding better, that is something you must decide for yourself and not get influenced by the internet.
BTW, I do have the amps you have and very much every v-fet amp made in the 70s, and many miles under the tires listening to them....in different restored conditions.
Click to expand...
I found out carb cleaner for car engines will work amazingly in cleaning contacts, Don't use any WD40 they will cause corrosive in the long run. If you want it more durable you can gold plate the contact by some electrolytic liquid and a DC powered cotten swab.

I love the "hot" sound from class a (or at least high idle current). I used to have a yamaha ca-1000III thats the beginning of my hifi adventures. It has a swtich to choose class A or normal working mode. I feel there is some magical happend in class a mode. It just sound right, airy lively smooth. Normal mode is just like not warmed up class a. I saw many says they couldn't hear a difference by swiching to class a. Yes sure, only after half an hour they could be different. That's exactly why I didn't get any sony vfets, I thought they are not hot enough to me.
ca-2010 normal.png
ca2010 classa.png

the lower is class A mode of a CA-2010.
credit to audiovintage.fr

The best part about ba-1000 is it can quickly reach its working temperature, so I Don't have to wait that long like yamaha's.
 
Last edited:
  • Like
Reactions: rottalpha
#43
ocer said:
I found out carb cleaner for car engines will work amazingly in cleaning contacts, Don't use any WD40 they will cause corrosive in the long run. If you want it more durable you can gold plate the contact by some electrolytic liquid and a DC powered cotten swab.
Click to expand...
OH NO, not the WD-40 and carb cleaners 🙂

no, that does not work, or at least it only works for a short period of time. The contacts in the B-2 front selector are crap and this is one area where I stay on the side of the people that bash Yamaha.
The selector contacts of the B-2 are open to air and to parasitic elements. What is worse, within the same switch bank, you have both, DC and signal switching. The cleaning lubricants in the open to air switch actually help collect dust, smoke, etc and at some point the goo becomes conductive and DC starts to leak into the signal path, straight into your driver board inputs. That is why you hear crackle and pops when operating those switches.
After cleaning a bunch of B-2 selectors, I gave up and redesigned the entire damn selector assembly, to farm out the signal switching to sealed, small-signal relays.
 
  • Like
Reactions: ocer
#44
@rottalpha
Thats the ultimate solution. Can I see some photos? But carb cleaners are good. They left nothing.
I cleaned the ba-1000 speaker selector with carburetor cleaner they are perfect now without a tiny noise, but time will tell.

btw what vfet amps do you have? how do you feel their sound?
 
Last edited:
#46
ocer said:
btw what vfet amps do you have?
Click to expand...
very much all of them with maybe a couple of exceptions
ocer said:
how do you feel their sound?
Click to expand...
I prefer not to generalize, but they stand at the top of the food chain as far as the engaging experience.
I work on my own units and rotate them periodically, then get excited all over again after I did not hear one for a while.

About Class A reference you made earlier: It is not about what class the amp is if it is executed correctly. There are crappy Class A amps and dome very good ones. I was fortunate to hear some good ones, old and new, and not so fortunate to hear some crappy ones too. I like everything that sounds good to my ears, including Class D.
 
#49
ocer said:
How could that be possible? Please tell me why by pointing out what is catastrophic in schematics. There will be some compromise in a commercial product but I wouldn't call that catastrophic. What is not catastrophic by your standard I wonder. If you mean some few watt output diy ones that cannot drive a modern speaker, I think that's more catastrophic. Why not use tubes in the first place.
Click to expand...
;-)-;
1. Task of hearing: To detect differences.
2. Every single part does modulate signal.
3. Same parts modulate audible different.
4. These circuits are very very high complex push pull (based on very very very different sounding) complementary transistors including different sounding psus: + and -
 
#53
mbrennwa said:
If you submitted the patent, your intellectual property is now protected and there should be nothing stopping you from disclosing your invention to us. It may take veeeeery long until a submitted patent gets granted and becomes public. Why wait?
Click to expand...

Only thing I can think of is if a competitor takes the patent, creates a better design (that bypasses the patent) covered with a patent-pending that then hits the market earlier and so you don't get a ROI window (just possible scenario to explain it).
 
  • Like
Reactions: Citizen124032
#55
rottalpha said:
... BTW, Most of the complexity of these older v-fet amps is concentrated in the protection circuit. That is why the are still clapping after close to 50 years 😉
...
Click to expand...
Don't mention the suicide diodes! Indicated in the 4650 picture of #19.
Three in the 4650, four in the 5650. They break by the heat in the end and destroy the V-fet's.
A serious design flaw by Sony. Other brands / models may use regular diodes instead and survive.
 
#56
rottalpha said:
with multiple components to replace one transistors you certainly thought of the likely added parasitic elements??
Also, I am thinking that the low thermal runaway characteristics of the v-fet were also considered??

I look forward to hear more about your device.

BTW, I am sensing that you might have already looked into Sonys hybrid output stage used for TA-N7 and TA-F7. Any influence from that with your design?
Click to expand...
Certainly! With two active devices there are two Ccb's (and the rest). That's unavoidable. Near same hf responses.
The circuit is thermally stable, self adjusting to the final end point, no runaway.

In the TA-N7, the V-fet's are used as cascodes of a regular 2SC1173/2SA473 emitter follower setup.
I've no circuit diagram of the TA-F7.
 
#58
Citizen124032 said:
Don't mention the suicide diodes! Indicated in the 4650 picture of #19.
Three in the 4650, four in the 5650. They break by the heat in the end and destroy the V-fet's.
A serious design flaw by Sony. Other brands / models may use regular diodes instead and survive.
Click to expand...
the suicide diodes are primarily a manufacturing part quality problem rather than a Sony design problem. Different versions of the part survive quiet well in Yamaha amps, but those are different part numbers. The ones Sony choose, do not.
Same can be said about the fusible resistors Sony choose. Those parts simply disintegrate internally and drift over time to the point where the amp stops working. But again, primarily a part quality problem.
Nonetheless, many of the amps are still around and kicking after nearly 50 years and I do not think that was ever an expectation. If you are lucky to find that has good v-fets, it is worth to give it an overhaul and then let us know what you think of how it sounds.
 
#59
@rottalpha: Ok, admitted, manufacturer. The black-with-blue dot are poor, orange-with-yellow dot are ok.
In the 4650 and the 5650 the main amplifier circuit board is mounted above the heat sink, so during use warming up and coling down after switching off.
I own a 4650 in working condition, one 5650 and two 4650's in service condition, all V-fet's ok. If one V-fet will fail, I'll replace it with my compound circuit (a high current version with a j-fet).
For listening experience see #15 3th paragraph.
 
You must log in or register to reply here.
Top Bottom