v-fet SONY ta-5650 modification

[mesut BALCI]

It may be as simple as 15 minutes of work, or it may need additional complex circuitry due to overall circuitry design. My aim is that I dont need a muting stage at preamplifier output, also I dont need more gain to turn the volume down more. Possible feedback at toneamp more probably does not do better than simplifing the circuit getting rid of 3 stages all of the buttons all of cabling around. All of these crowd are connected with a socket to the "flat amp with its unique volume pot". Nothing will be ahead of cap C205 after flat amp but only a pre-out rca to get signal out. And before volume pot, stereo mono switch is not on the path but a paralel line to combine channels only in simple way, also mute and loudness are not exactly on the path. Thus before volume pot, there is nothing but only my external adapter inputs for my line inputs just connected by ext-adapter switch. Using them result in sonic difference with serious improvement. This job even will give no harm to originality. I will remove the socket, then I will put my own socket to get signal out of flat amp to outside of the amp by a cable with female rca's soldered to the tip of cable. Returning back is as easy as putting original socket to its place and screw the cover of amp.

This much dream is enogh, now my problem:
I dont have knowledge to analyse if flat amp output is suitable to use as a preout to fit standards or at least fit in the limits. To do this simplification, what kind of addition is necessary to use at the point of socket 71 which are simply connected to capacitors C205/255 on equaliser amplifer board? I will add the modificational parts on the fly to my socket not even a solder to pins or anywhere.

Rather than getting signal out by a cable, a "direct" switch at the back may be used to by-pass this gain stages and its feedback, muting stage, all tone tone controls, all filters and preout jumpers. Source is already direct enogh with external adapter inputs. An up to date 5650. Using external adapter inputs already make serious difference with their shorter path eliminating big switches. This mod makes it smoother than anything around with strict control and staging properties.

Thank you so much
I attached the schematic

mesut

[Unda Maris]

Mesut,

The flat amp is quite low impedance (<1kOhm), but is not built to drive longer cables (capacitive loads).
I would recommend to use Q205 as output buffer as already realized. The mute switch Q206 is not harmful, since it is extremely high impedance, while switched off. You can reduce R233 to 100 Ohms in order to optimize output impedance. This would perhaps reduce muting capability but if you already wanted to eliminate it ...

Take a look on my modified schematics !

What do you think, does this meet your requirement ?

The balance pot is still in the path, but if you don´t like that, you also can set the patch directly to the flat amp output (before C205).

C205, C218 and C230 should be foil capacitors for ultimate performance !

[mesut BALCI]

You are really wonderfull, a kind of veil started to disappear on the schematic.

-No need to exaggerate the effect of muting.
-C230 coupling is also necessary.

*But, is not one of the purposes of R233 to prevent output from being shorted when muting is on? So by elimination of muting circuitry, C230 +pole can thus directly be connected to preout? Or 100k R232 aims to decrease total output impedance too being paralell?, thus only 1k R233 can be eliminated rather than directly coupling??

*If flatamp output is lower than 1k(why?), and able to drive poweramp input reliably(any danger to flatamp and poweramp?), so i measured that it will take only 11cm of cabling to connect flatamp output directly to poweramp input. Much shorter than the cable connecting the same point to next point at tone amp board.

So after your reply, removing poweramp input socket from poweramp, also remove signal output cable("1" tone cancel) coming from balance pot, from its socket on its board, I will connect flatamp output after point C205, to directly poweramp input. If you see any inaccuracy, your solution will be really an optimum way of optimisation.

*What are R205 and R206 for? It seems tone amp is always running and R206 is feedback resistor when only tone is canceled state, and when again in tone canceled state signal passes through R205 before coming to tonamp. But there is no resistor at tone on state. I could not understand yet exactly. Will I need an additional 10k to C205 flatamp output before direct connection to poweramp?. I attached the pre part of main diagram, shows this.

--What can be the worsenings? I think drive may decrease, noise ratio may decrease, distortion due to lack of feedback may increase.
--What can be the improvements? Overall control will increase to a terrific degree, directness and sonic purity will increase to passive pre level, due to lack of many sockets, buttons, cables, and active parts, distortion will decrase very noticably(i hope eliminates lack of feedback).

[Unda Maris]

Hello Mesut,

I simulated the circuit of the Flat Amp in PSpice ! It´s output impedance is only 60 Ohms, so it´s suitable as a driver !

If you want to use it directly as a driver I would recommend to add a serial resistor of 100 Ohms to prevent oscillations.

Nevertheless, I improved the thing a little bit, by adding a J-Fet, two resistors, one capacitor and changing a resistor value.

Take a look on the schematics, it´s dead easy, but ultra low distortion !

Old Flat Amp: 0.068% THD, New one 0.0026% !! :yes:
Power Supply Rejection improved by about a factor of eight ! :yes:
SNR = 110 dB (at 1V output) :yes:

The 100pF and 15pF should be silver plated mica types.

Believe it or not: I modified my TA-N7 with such capacitors and it´s a big difference to the used ceramic capacitors.

[mesut BALCI]

:scratch2: when I added the picture of my amp as awatar, I remembered 2 years of tring to get working original good condition vfet 5650. My try to insert a 4650 vfet poweramp module to nonoriginal 5650 resulted with blown vfets with blown speakers although every voltage looked correct. This is maybe the newest 5650 available on the world came inside original box with original manual, warranty paper, even a cleaning cloth, all inside their original bags. All my friends talked to me wishing me not to touch it and when I asked help my engineer friend said he wont touch that amp. Ok, hands up, it will not be practical to make amp integrated because i commonly try devices with it. When I use your way of modification, only thing I get rid of will be stage with feedback and 2 buttons. I will postpone modification until I try sony tae88 and 5650 is still gets to be my preamp to use. But as you also insisted on caps(look better way of modification now), when I examined amp I saw 2 weak solder point signs. thus it is time to make a general check, resolder and while doing them a recapping in addition to replacing resistors later modified by Sony. Even a bigger heatsink replacing small earlier one, pads, soldering of socket points removing sockets.

So lets do this thread common to all

What brand and type of parts for what position? An overall refreshing,
all black gate, all vishay?:

-all caps
-relay
-bias pots
-diodes(special brand for 1n4148?)
-vfet termal pads
-spk terminals, (i will replace some input terminals)
-input transistors?
-any resistor on direct path
-solder brand for common use inside amp
-any cable replacement inside
-others

[Unda Maris]

Mesut,

I can only repeat, what your friends said:

Please don´t touch that unit !
It seems to be really a unique piece !

Let the really needed modifications (like recapping) being done by someone, who has already done some work on V-Fet units like "ilimzn" (Zeljko) or myself.

If you need a unit for your own experiments, I currently sell a part of my collection, including 2xTA-5650 and many other interesting stuff ...

kind regards,

Mirko

[darko]

Hi Friends of the TA-5650 Series,

My Name is Darko. Iam from Switzerland. So, please remember this, when You find "lustig-english-words".

I have 2 Sony TA-5650 in mostly working Conditions. 1=ok, 1=69%ok.
1 Wega V-4810. Defect and 2 2SJ18 are missing ... EPay ...
Than is here a TA-5550 Poweramp. He is defect. The Fuses blow up when powered up. Have not much Time to fix now.


My Question is:

How relevant is the Bias of 90mV?? Is 70mV to little? I cant see a difference
in the Soundpicture. Have Yamaha's NS-1000 Monitor Speakers.

Iam very happy to can say: Yes, its a S..., BUT V-Fet :)

Darko Vagenhofer
near Zurich, Switzerland

[mesut BALCI]

Hi Darko,

When I adusted the bias voltages when the unit came, I was using tannoy speakers, not a very good model. And I noticed a kind of realism lack at one channel, only a feeling, and saw that this channel was cold, i saw also that it was 55mV. So I tried to adjust biases then. Possibly due to my speakers at that time, I could not see noticable diference between 70 and 120mV. However I adjusted bias so that sound was smoothest to me and luckily it was in the region of 85-100mV for the channels, i remember one is 92 the other is 87s(not sure), then I never touched the pots because it was too hard to make right channel stop at a voltage, after adjusting, i monitored the voltages for a couple of hours and let them at that stable and to me smoothest point with a kind of realism. Then I tried the amp at some really good systems, even an aer-mk1 fullranges, with all my later units, it was always fantastic, I still never touched the biases. After 1,5 years it is always fantastic with mysystem which is much more extended at response and amp always responded to all the changes, never falls under any limit.

[darko]

Hi Mesut,

Thank You for the fast Answer :)

At the time, when the first Unit comes, i was checking him and cleaning out in the Garden. It was a big Surprise for my Ears. Wow !
The Sound was so natural and clean. I was aligning the FM Front End of a old Pioneer Tuner TX-9xxx. I dont remember the Modell now.
The Speakers was from Dual. Little and Handy to take them Out in the green.

What Experience .. great !

Is it possible, that the one Bias Current is pushing up or down the other ( Channel ) ? I hook up two identical DMMs, to see both in Action.
When the Left Channel was about 89-92mV, the other comes down to about 73-86mV. Ok, i look for the Right Channel to be in same Range - and -the Left comes up or down. Can this be a malfunction of the Power Supply Board??

Have You replaced the both suizidal Diodes yet?


Greetings,
Darko

[Unda Maris]

Hallo Darko,

na endlich einmal ein V-Fet-Fan aus der Schweiz !

Crosscoupling of bias current adjustment is normal, because there is a thermal crosscoupling via the heatsink between the power devices and the bias setting diodes, which share the same warm air. These effects are always slowly moving.

Another coupling comes through the supply rails. The idle supply voltage goes down, when more current is drawn by the amplifier.
A V-Fet amplifier´s bias is inherently dependent on supply voltage.
There is a compensation circuit implemented to eliminate these effects, but due to aging of the power devices and/or the bias diodes, this might behave not perfectly.

[darko]

Hallo Mirko,

Yesss - und was für einer ...

Thank You very much for this good Informations.

My "Today-comming-In" Unit ( 506'935 ) have a strange Issue.
I know this from the nice Gentleman from Italy, the PreOwner.
This TA-5650 is not yet powering-up here. I wait till Tomorrow.

Need some Thermal-Silicon-Grease and new Diodes 1N41?? to replace the old ones.

I read about some "funny" Updates for the earlier Production Numbers.
Very nice Posting :) Thank You Mesut.


- The Issue is, that only the "Tuner-Inputs" are in Function.
Aux and Tape-In not. Great :-/ But, it sounds like a Switch Problem.
I hope i can fix this nice and smooth.

All Pioneers, Sansuis and Marantz Units here, sound good too.
But, they have not so sweet Sound for my Ears, like a V-Fet from Sony.
Ok, i do not have a nice Yamaha B-2 or B-1 (not yet). Maybe, one day, when iam in Good Luck..?

Here in Zürich-Area is in the few past Days a nice Summer. Hot and busy.
Even now at 00:07, its pretty warm here.
I thinking about some big quiet Fan's for the V-Fet's.

Greetings to good old Germany too,

Darko

[mesut BALCI]

Wait at least 10 minutes of warming up. This is not a very noticable issue with my current speakers, I only get step by step sonic jumps in 45-60 minutes while warming up, sometimes something stops holding music and a relief, relaxing, smoothness jumps with stage widenings, depth increases occure, "BUT" when the amp was connected to AER mk-1 fullranges of my friend, up to 10 minutes unit was really bad, a bad trebles with a nonspecial sound. We stopped listening it preferring radford sta25. But to try something we turned back to already warming up 5650. We got excited hearing the sound, and it continued to get better and better at trebles, trebles got life, lost distortion, had huge details, sound gained life and then at stage inside a couple of minutes started to get bigger and bigger and bigger coming close to us and ooops room disappeared and I even got afraid of a possible attack to me by the amp, terrific spatial state with increase in speed, timing, realism, resolution... Some sonic holograms here and there. singers consisting of head only body and some drums popping in the volume, when cd ended, my friend looked at me and me to him only frightened lookings, This is a true 3-D shocking experiment I got 3 times, one with aers, one with my monitor audio speakers that i bought them when i heard with my amp at my friends home, but got similar result only one time at home yet in 8 months. Room to me effects things too seriously, flooring had hundreds of spike holes finally by coins under spikes a huge increase in clarity and depth, still no help. Due to bias with new room voltages? I always afraid of loosing this already available sound so i never touched the amp but no help with anything i tried. When this sound gets stability and continuity it is the end for me. nothing can be like this. Now i try some other preamps to strengthen available properties to get this sound. Neither single alps pot or ladder vishay dale pot didnot help, glass, eraser, some materials under speakers cdplayer or costly cabling didnot help. Even I thought a serious modification inside the unit. Change of home??, one day my wife will kill me or my amp :scratch2:

[darko]

Hi Friends,

I got it fixed !

He works nice and clean.

- un-mounting all V-Fet's
- un-mounting Isolator Pad's
- cleaning V-Fet's and Aluminium Socket-Plate

- applying Thermal-Compound, easy and only a bit with a old SD-Card
- mounting new Isopads TO-3
- cleaning all Holes from Thermal-Compound
- applying a second overlay Thermal-Compound, very small amount
- INSTALLING cleaned V-Fet's back - fixing Screws nor to hard

POWER UP !

- Checking first the 20 Volts - TR401 at Q403 Emitor, was 21, now 20VDC
- Checking than the 100VDC - was 99,7VDC - should be 100+-3
- BIAS Adjustement - WOW, cold: 47mV - hot: 89,8-91,3mV
This was a huge Up-Flow ... Powerrd up:47, than in several Min's to over 90
- Checking DC-Offset, should be in PlusMins 50mV about ZERO Volt DC !!
Was first L: 13,? and R:4,? mV - half houer later: both +3mVDC - Great :)

Almost done..

I was today in the City, parking in bad place. Police was there ( bad Accident at the Electronic-Shop Side) No big Time to shopping Diodes 1N4148 .. grrr..

Back at Home, i done the Job at the Kitchen-Table. My Wife helps me to clean the V-Fets from the old, brown-colored Thermal-Compound.

I dont have very good Speakers in the Kitchen. Only little Canton for my Akai Vintage Receiver. Sound is ok.

But to hear something, i connect the old EV Wolverine Something. Very old Spekers with genuine parfum of a "Kuhstall" ( Cow-House?). From Luzern ..

But they have big impressive Bass-Chassis and a nice Horn-Driver.
The Sound was incredible clean an tuff in deep Areas. Ok, they are more on the Floor, for making something like a Side-Board-Speaker-System.

Yes, iam satisfied, hungry and need a cool Shower.
The TA-5650 works in both Channels - this was only a Contact Issue at the Terminal Board ( veeery weak, lausy Chinch-Constructions .. )

Thank You for all good Tips and Infos about this magnificent Amplifier !

:tresbon:

Have a nice Weekend
( and Mesut, hear at Your Wife .. ;), Women have better Ears ! Fact! They Younger they better hear too )

Greetings,
:music:
Darko