Sony TA-4650 V-FET Amplifier (Part 5 - Review + Benchmarking)

[@petermaurer323]

If you want to do a full resto, it's no one's business to question as to why. I've followed all 5 parts and great outcome. Looking forward to future projects.

[@timomy8]

Well done stick to your guns only you need to be happy, no compromises unless you so desire. Thanks for sharing.

[@countdebleauchamp]

I had one of these in my youth. Loved it, eventually replaced with ARC SP4 preamp and a variety of different amps. It had a very unique Class A amp type sound. Definitely better than the Marantz 1030 it replaced.

[@bst8733]

Just love the transformer(s)/headphones idea. Brilliant!

[@paulstubbs7678]

Interesting your comments about replacing all the transistors, I have a Toshiba SC330 amp kind of on the bench, having fun finding suitable transistors, one of the channels input stage - long tailed pair was starting to 'go', it would cause the amps output to spike up to the full supply rail, took out my test speaker, which surprised me as the spikes were quite narrow. So yes, old transistors are a problem.

[@whatcouldgowrong7914]

They seem to become more problematic with age, I don’t recall it being such an issue a decade ago, the HK330B was really bad also

[@Roudaki677]

I own several of the VFET family, in fact one of the 4650 since brand new. The 4650 has always been the sweetspot of the range. I own a bunch of vintage items from Sony’s golden era. If you ever run across a TA-2244 or a more widely available TAE-86 or TAE-88 you will find preamps that rival modern preamps after some minor restoration.

[@whatcouldgowrong7914]

I shall keep an eye out for them!

[@adaboy4z]

Been waiting on this video!! Parts list!! Thanks.

[@whatcouldgowrong7914]

It’s in the video :)

[@PeterMilanovski]

When it comes to finding what's causing the noise floor, a single tracer is your friend, especially if it has the RF mode where you can hold the probe above individual components and hear what's going on... Paul Carlson of the Mr Carlson's Lab channel showed how a bad carbon resistor was adding noise (sounded like a thunderstorm was going on inside the resistor). Sure you could have found it via an oscilloscope but the signal tracer was so much faster and easier to use since you don't have to keep looking up at a screen! I personally don't have one but I have always wanted one since I first saw one being used! It's a pity that Heathkit doesn't make the kit anymore! Or at least I think that they don't, haven't checked their website in ages, they are re- making their digital clock though.... Every workbench should have one!

[@whatcouldgowrong7914]

Never had any luck with any of my tools as my those headphones are so sensitive that it is generally beyond the noise floor of my oscilloscope etc. That said I’m quite sure it’s normal for the era and minimal. Never heard a preamp or integrated preamp that had an SNR high enough from the 70s and 80s except maybe the Sansui Alpha’s. Probably some Yamahas also that would pull it off knowing how well they usually measure…

[@PeterMilanovski]

@@whatcouldgowrong7914 on the topic of the signal tracer, you can gain a similar effect using an old cassette deck head, using the playback function, it's pre amp is pretty high gain, with the head removed and attached to a piece of dowl, you can make a probe that simply by placing it near a component, you can hear what is going on inside... I'm not sure if it will work as well as a proper signal tracer like the one's built in the 1940's in America, Mr Carlson's Lab KZbin channel has built his own modern day version of it, he has videos of the build plus all the details behind the patreon wall.... It's an indispensable tool that will make problem solving so much earlier and faster. It's a whole other world going on inside each and every single component but we unfortunately can't hear it without help..... I don't personally have one yet even though I have wanted one for years, I will either make one by cascading a few opamps or if I'm lucky enough and have the money, I would get an eiko or Heathkit that has the RF signal tracer ability and have it delivered from the US! It's a bucket list item for me!

[@bpalpha]

Thanks man. Handsome unit there.

[@mattiamanc]

I find it surprising that it has a noticeable noise floor. I restored a few of the Sony V-FETS (about5-6 TA-5650, 2 TA-4650, a TA-8650 and a TA-F7), nowhere near your level (apart from killer diodes, recap and the usual for these I tend to leave semiconductors alone), and the only one that I found was noisy (hiss) was the TA-8650 (from a noisy pre-amp section, but it is likely because it uses very early ICs). The only thing that I noticed was that the TA-5650 and 4650 tend to buzz a lot if you use noisy inputs (desktop computers, mobile phones) because they are very sensitive to EMI. Not sure whether the noise floor you describe is a hiss or a buzzing noise, but maybe worth checking whether it has something to do with EMI.

[@whatcouldgowrong7914]

The headphones I used are very very sensitive and pick these things up easily, it’s not an issue for my speakers or electrostats but definitely present. Not unusual for a 70s or 80s preamp-amplifier either. It could be the jfets but not as easy to substitute.

[@horaciorecalde1689]

Excelente videos. Mirè los 5 y estan muy buenos. Hace muy poco, comprè un 5650 y tiene un sonido muy bueno. En los costados tiene una madera con vinilo que no me gusta y quiero preguntarte, que madera usaste? Se vè muy linda y el color tambièn.Muchas gracias...

[@whatcouldgowrong7914]

Im not sure what the wood is sorry as I got it years ago but it was from the hardware store and some sort of laminate. Not an exotic wood as it wasn’t expensive :)

[@horaciorecalde1689]

@@whatcouldgowrong7914 muchas gracias por tu atención. Esperamos vídeos nuevos.