Continuing my quest for quality music, I ordered a Dynaco VTA ST-120 tube amplifier kit from Bob Latino at www.tubes4hifi.com. I’ve built many complex electronic kits over my lifetime, and although it’s been many years since I’ve built anything, I still have the necessary soldering skills and tools to do so.
Bob makes kits for 35 watt and 60 watts per channel tube amps. I could have ordered the 35 watt version, but I’m a power junkie, so for an additional $190 I decided to go with the 60 watt version. I also like the look of the KT-88 output tubes, but I guess you can get them for either version. The only other upgrade I ordered was the 8 power supply and hand-matched Russian K40-Y PIO coupling caps.
Although I could have obtained the tubes from other sources, I purchased this first set from Bob knowing they would be quality matched Russian made output tubes.
I received the 40 pound package via UPS Friday evening. All components were well packaged and identified and it came with easy to read instructions, drawings and photos. This is not a kit for the inexperienced kit builder. Although everything is well labeled and identified, and the instructions are excellent, it does require some skill in solder techniques, wiring, and general electrical and mechanical knowledge (for instance, you have to know the difference between 4-40 and 6-32 screws).
The manual says it takes 10-12 hours to build. It took me 11.5 hours total after I double checked all my connections, so his estimate is about right.
I followed Bob’s instructions by installing the tubes in the pre-amp and turning it on. The filaments lit up as expected so I went on to the next step and installed the rectifier tube and power output (KT-88) tube on the left channel and connected the speakers. The tubes lit up and I proceeded to set the bias voltage on the left channel. I then did the same on the right channel. There was no hum in the speakers and the bias adjustment was easy to set. The next step was to hook up my Integra pre-amp outputs to the inputs of the ST120.
I turned everything on and played my favorite CD that I converted to FLAC (16/44) – Super Session by Mike Bloomfield, Al Kooper, and Steve Stills. Wow, I couldn’t believe the quality of tone and clarity coming out of my speakers! I thought I’d lost much of my hearing having worked in a newspaper press room for many years and attending many ultra-loud concerts, but I could easily hear the highest of highs and lowest of lows coming out of my speakers. The tone from each instrument sounded discreet and separate from all the others and the voices sounded like they were right there on stage. I then played some 24/96 HD FLAC files with equally fantastic results.
I know sound quality is subjective, and I have no way to measure the sound quality benefit of using my new amp or of using HD FLAC files except with my ears. Is it really better than just playing a CD through my Integra receiver? All I can say is, I don’t think it can get much better. And if it were to get any better, I probably wouldn’t be able to tell the difference anyway. I’m extremely happy with what I’ve accomplished and, if nothing else, I’ve had fun doing it.
One last note…the amp has an option to use the output tubes in Triode or Pentode mode. I’ve only used it in the Pentode mode so far which supplies full power and apparently has a wider range of frequencies. The Triode mode is often used for Jazz and vocals where you might want a roll off of the extreme upper and lower frequencies.
Hi Russ,
thank you a lot for the prompt and solid response: you helped me a lot and now I am seriously considering going for the VTA-120. I feel my solid state amp is a bit harsh and missing a bit of bass with some digital recordings, and having the Dynaco compensate a bit seems to be the ideal match.
Side note: I also use my Onkyo mostly for playing hi-resolution FLAC files, but from an attached USB drive and not via network. I noticed the latest firmware update for the unit (December 3, 2013) improves the quality of the playback of the hi-res FLAC files, eliminating that random “click” when playing music sampled at 24 bit. If not already done, have a look if there’s a firmware update for your unit too (there should be, it’s the same hardware): it might not solve your network issue but it could help. One last thing about the Onkyo: if it would have been able to play gapless (no pause between audio files) I would have rated it 10/10 for the price.
Cheers
Aldo
How great.
I have an Onkyo TX-8050, which is (at least from the specs POV) the exact equivalent of the Integra DTM 40.4 you have. You know, Integra stands to Lexus as Onkyo stands to Toyota.
I dream of building my own Dynaco ST-70 or ST-120 one day, and since I am pretty sure about the tube amp quality, I am more interested in the matching between the two units. So, my question is: how good is it the Integra in acting as a pre-amp for the Dynaco?
Furthermore, what differences in sound do you perceive when using the Integra directly connected to the speakers in comparison to when you use the the Dynaco as the final amplification stage?
On a scale from 1 to 10, how strong would you recommend me going for the equivalent setup?
Cheers
Aldo from Italy
Hello Aldo,
I do not have any diagnostic equipment to give you a definitive answer, but from my purely subjective hearing perspective, I found the Integra to be a great preamp for the Dynaco. I do not hear any distortion and the Integra pre-amp output level seems to be able to drive the Dynaco amp as expected.
As far as comparing the output through the amp, again very subjectively, I find a smoother sound with deeper base particularly with analog or high definition digital music.
Probably can’t compare it to a high-end audio system. But I would give it a 10 for a system in this cost range.
The only drawback I’ve found is a limitation in the Integra when it come to “pushing” high definition digital (FLAC) music from a music server. It just can’t do it.
Russ
Kevin,
I’m still very happy with the results of the amp. I doubt that the amp or my B&W 683 speakers are yet fully broken in as I only have about 20-30 hours listening time. But then we know sound quality is very subjective and depends largely on the preamp quality and source of the audio. I primarily listen to analog (LP) and hi-def (FLAC) sources. I used Russian KT88s as the finals in my amp which provide plenty of power for me, but the size of the transformers Bob supplies in the ST120 I would think would be able to handle the larger tubes.
Russ
Russ,
I completed my VTA ST120 I bought from Bob Latino at his site. I followed his instructions as far as the start up procedure and zero problems! I biased the tubes and hooked up a Yamaha preamp. I did add the soft start kit,the pio caps and the KT 120s Matched quad Sovteks. The amp sounds great. I do recommend the soft start kit. Much easier on the tubes. Great build. I am planning a tube preamp kit next.
Kevin
Russell
Thanks for the write up and photos of your Dynaco VTA ST 120 amplifier build. I am considering a purchase and I am looking to see how others are enjoying the sound of this amp. It appears to of good quality parts and relatively easy build. I am already thinking of trying a few mods of my own. I asked Bob about using KT120 tubes. He said there is plenty of power in the power supply to use these tubes. I may be able to eke out a few more amps from this beast.
After a few weeks of listening how is it sounding?
Thanks,
Kevin Hurst