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Dynaco ST70 based on original PC3 circuit


Idontknow

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I just acquired one of Kenny Russell's all new ST-70's https://getdynaco.com/products/ready-to-ship-dynaco-st-70-tube-stereo-amplifier  based on the original circuit using 6GH8A military grade input tubes and EL34 NessTone output tubes. It's got the latest, best transformers and solid state rectifier which have several advantages. The unit utilizes the best components and after hearing this unit for the first time, I dropped my jaw in disbelief at the performance. The differences between this model and the Bob Latino and Will Vincent ST-70's are incredibly striking. This model Kenny did for me has a noticeably more classic, vintage sound signature as David Hafler intended it to be. It's silky, warm, lush and velvety smooth with jazz while the bass is tight and clean, even at the highest possible volume levels with my Heresy and Forte's with classic rock.

 

There's no doubt that most  of today's modern tube amps have lost the vintage sound signature with overly analytical, bright and brittle sound signatures, particularly those pouring in from China that most only seem to talk about. At first, it all sounds exciting, but over time with smooth jazz, I just found it to be a bit too ear fatiguing over longer listening durations and too forward. This ST70 Kenny did is the most amazing amp I've compared to date along with the ST35 and I think it's because both remain as close to the original circuit but with higher quality, more premium components available today. The famous review by David Gillespie here http://www.audioregenesis.com/documents/ST-70 Base Line Testing.pdf was adamant about retaining as much of Hafler's vintage ST70 sound signature as possible and this is the reason he's used it as a reference/benchmark. The issue of original vs modern was also covered here by Alan Acuff here

http://santafemusic.blogspot.com/2008/09/tube-be-or-not-tube-be.html and I agree completely. 

 

Bob Latino addressed some of the issues with the original ST70 here https://dynacotubeaudio.forumotion.com/t465-traditional-driver-circuit-designs-versus-modern-all-triode-designs against his Triode Circuit that also has Pentode but I never enjoyed the Latino pentode circuit as much. It just sounded too lean for some reason, unlike the dedicated Ultra Linear circuit Kenny uses which simply tromps all over my Latino ST-70. The differences are mind blowing. 

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1 hour ago, Idontknow said:

... a noticeably more classic, vintage sound signature as David Hafler intended it to be.

Hafler built for a specific price point, that also sounded great. I would compare the original ST70 to the H/K 430. They were and are great pieces at their price point, but not the be all end all amps/receivers.

 

I know, I've got both. I have an ST70 that I bought from a friend in the early '70s. He built it from the Dynaco kit. I used the oeiginal tubes until I put in a Curcio front end in 2005. I kept the tube rectifier, bur replaced the power transformer with one from Triode Electronics. I've currently got it disassembled to try another front end. We'll see how it goes.

 

Glad you like what you got. That's all that really matters.

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Thanks for sharing. I haven't had the pleasure of hearing the HK 430 but I checked it out online after you mentioned it. My audio buddy has an integrated amplifier by HK from the 70's and I can't recall which model it was but it amazed me and it was solid state of all things. 

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10 minutes ago, richieb said:

I owned a 430 once upon a time and although it hadn’t been “freshened up” I just never saw/heard what the fuss was all about.

Hence my comment about 'not the be all end all amps/receivers.'

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4 hours ago, Idontknow said:

In case you were asking me. 

 

Sorry, yes I was asking you.  

Thanks for sharing, I have a stock ST-70 with the original 7199 driver tubes and a older PAS-2 with the gold faceplate.
Kenny's amps & pre-amps are enticing. 

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It has been awhile since I compared the Pioneer SX-1980 to the Dynaco since I use the Pioneer to drive the woofers on the Forte's and the Dynaco to power the mids & tweeters.  I did this to get the chest thumping bass from the SS amp and the tube sound for the horns.  The Dynaco could not produce the tight low end like the Pioneer, maybe because it has a tube rectifier and is only 35 wpc. 

 

My music choice is classic rock/heavy metal but I appreciate any good recording regardless of music style.

 

Back in my college days (early 1980's before CD players) I compared my SX-1980 head to head with a higher end Yahama receiver (200wpc).  The Yahama sounded "sterile" meaning that it didn't add any "warmth" to the sound which was their signature sound back then.  The SX-1980 had more of a "live" sound meaning that you felt a double bass drum kick you in the chest and acoustic guitar/violin stings resonated like the artist was in the room.  My speakers back then were Speakerlab S30's which produced really low accurate bass. 

 

I also have an older Pioneer SX-990 receiver for my smaller 2-channel system that has a nice warm sound, almost tube-like, for a SS amp.

 

My HT system is an older Pioneer Elite HT receiver that I use with my Klipsch RF-7 HT speakers.  The sound is very clean and detailed with plenty of power.  I mainly use this system for blu-ray movies/concerts and SACD's.

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Thanks for sharing. The current ST70 and ST35 I'm using have provide extremely tight and controlled bass with my Heresy and Forte. Both use solid state rectifier's. I've had a number of solid state amps here but the Dynaco's bass performance are every bit as good if not, even better. 

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