VTA ST-120 Amplifier Review and in Depth Tour 

Did the auto-bias boards make any changes to the sound quality?

@@jebcamaro absolutely none! Just hassle free tube enjoyment!

You bet! There are plenty of options out there for truly wonderful hifi at affordable prices, both in the new and used markets. Thanks so much for watching.

hahaha, you must have owned one, mine is a winter only component

Glad you are liking it. Do you have the solid state rectifier, or valve type? Mine is valve and I blew it up in the first week by cycling the power too quickly. I therefore made the "Yellow Page" mod to add a diode in series.

Good point. BTW, the current version of this kit runs both the 4 & 8 ohm taps to speaker posts on the rear. As you note - a good thing to have!

Thanks for watching - let's hope those valves continue to be available...

The ST-70 and ST-120 have PLENTY of power if matched with high efficiency speakers such as Klipsch Forte

@@jx8912 Sure do!

Wonderful! Are you going with the tube or solid state reg? If going tube make sure you make the Yellow Page mod, otherwise you WILL blow it up sooner or later.

@@audionautica6843 I’m going with the solid state for now with the trd, I was really thinking of going with the tube but would like to hear someone’s opinion who has had both! I have the yellow page mod saved if I go with a tube rectifier. I think it may be a while before I try the tube as they have just skyrocketed over the past week. Do you have an opinion on the two options? Also I noticed the power cord is two prong, I have a feeling that I may not be able to run the power through my power conditioner?

@@kastlrock557 Mine came without a power cord, as I had to provide my own Australian power cord, and the directions gave the option of earthed or unearthed. I would imagine you could have it earthed if you wanted to by changing the power cord. I went with the tube rectifier simply because I thought that a solid state rectifier is a bit counter-intuitive in a tube amp! That's the only reason. But then, you really need the yellow page mod, which is a silicon diode in series with the tube rectifier, so it isn't so purist any more, is it? There should be no difference in sound quality whatever. I'm an electronics engineer and I think people who talk about tube rolling rectifiers are on jungle juice. Given the shortage/price of tubes you have identified I think the solid state option is the right way to go. I have plenty of rectifiers on the shelf for my own use, but time again I probably would have gone S/S. Also, many people report that for high output levels they go through rectifier tubes pretty quickly.

@@audionautica6843 For high output levels, I could see someone going through rectifier tubes! For my klipsch belles at 103db sensitivity, a tube rectifier might last a touch longer. It’s hard seeing a spot for a tube and not putting a tube there 😄 it’s definitely not purists, but it’s all relative right? Some purists might say it’s not a real tube amp cause it’s not point-to-point wiring!!! Solid state makes sense, and I will run it for now with the timer delay, but it’s a open spot for another beautiful tube and maybe when things become normal, I will try the tube. For now I gotta build it mate.

@Audio Nautica Regarding tube rectification, there are those who say that changing the rectifier tube makes no difference and others who swear by it. Here's the skinny: changing the rectifier tube is not an "Oh my god!" moment. Not like changing speakers or even like changing output tubes. The differences between tubes is subtle. It all comes down to how well trained your ears are. And just like anything else, training your ears can be learned. I first started working in audio in the late 80s and when I started I simply didn't know how to listen and my ears were not sensitive to subtle differences. But I learned and at one point I could tell when tone controls were switched in or out of a circuit, even when they weren't engaged. Thirty five years later, I doubt my ears are still that sensitive. BUT, changing rectifier tubes does make an audible difference, it just may not be worth the expense for such subtle changes. For those with very trained listening skills, to them the differences will seem much more obvious and worth the expense for the enjoyment of getting different results. They are not crazy - not by any stretch - they just have higher sensitivity and appreciation. One thing that virtually anyone who is into audio can listen for as they tube roll the rectifier is for differences in the soundstage - holographics, width, depth, etc. The most obvious changes can be heard there.

Glad you're liking it

The rectifier tube couldn't support el34s at full power, this was always the weak link.

@@tedcollins4684 right. You'd get sagging

Thanks for the comment - I'm sure you'll be fine in a storm with the "yellow sheet mod".

Sorry, I don't know.

These: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_XiimqeZXfQ.html

I see what you mean, I think it's just the light. Discolouration is usually heat related and means going darker.

@@audionautica6843 Cheers! It’s really a thing of beauty!

I will make a measurements video one day. I think it will be interesting to do a comparison to the Sansui AU-X11, but I also want to compare square wave response, and I currently do not own a function generator, so until I do...

@@audionautica6843 look forward to it.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-F9yAAcDKl1g.html

Thanks for your comments and experience on long term use. I generally don't listen loud. My speakers are very efficient JBL studio monitors, so I can't go near the power rating of the amp. I am still on the original (well, second actually as I flashed the first one) rectifier tube and KT120s. Can't remember what bias I am running, but I would think a KT120 would have longer life at the same bias compared to a KT88.

@@soulnik I do use a Bellari phono tube preamp. My main control is an analog ten channel mixer! Two channels for each device, that way I can control tone and levels for each and it gives master volume at mixer. Lets me play vid games and records or tuner at same time.

Not sure where you live but I live in Australia where the nominal house voltage is 240V AC. I bough tthe 240V kit. During the build I went through a couple of rectifiers and when I measured the house input voltage it was around 255V. I have solar panels on the roof and I'm told that they need to have an output voltage > line voltage if power is to be transferred to the grid,. This could be the reason i went through rectifiers. Not sure if this is correct . However I now run my ST120 with a variac that I have set to 230V. Its been 3 years now since i had to replace a rectifier. I'd have to honest and say that it is not driven hard or frequently however so far so good. I'm very pleased with it.

Yes, that would make sense. I am in Australia, and here the line voltage is bang on 240, but I do the same as you, variac it down to 230.

www.tubes4hifi.com/amps.htm#ST120

Wrong, my kit was just delivered today! The communication as been unbelievably great, and so is the packaging.

@@audionautica6843 Great , thanks so the 70 is available now, and the 120 is due to be available in April. Thank you for the link.

I built the VTA ST 120 last year, specifically to pair with my JBL L300 clone speakers. Agree 100% with your review and assessment, and highly recommend the product. Sadly, Bob Latino has retired... I benefited greatly from his assistance with the few issues I had. I am confident, however, that brand is still well supported. I run mine on an inexpensive variac, to reduce my 121v line voltage to 117v, per Bob’s recommendation.

@@briansilcox5720 You could also wire in a small bucking transformer which many do when running higher voltages than recommended.

I've added a link in the description.

I guess they are usually hidden under the chassis, although the Dynaco ST70 always used the arrangement that you see here.

@@audionautica6843 I run a decware tube amp ...its old school...no circuit boards

Yes, tube amps are generally more expensive than solid state, however this kit is a pretty cost effective way to get into tube.