[js1955]

Thanks FullRangeMan that Rouge looks interesting. Also an Dynaco ST35 was just listed on USAudiomart https://www.usaudiomart.com/details/650200752-dynaco-st-35-stereo-tube-amplifier-beautiful/ No easy choices in this hobby.

That ad is from Chris Keller in NC.  For years he has been rebuilding vintage amps, mainly Dynacos.  Unfortunately, he has some health issues and has slowed down recently.

4 years ago I bought a rebuilt Dynaco ST-70 from him.  In a word, the whole experience was fantastic!  Amp sounds amazing, dead quiet and reliable, and looks great too.   His prices are more than reasonable.  Chris is a true gentleman with great technical and communication skills.  His 8 pages of stellar feedback says it all:

https://www.usaudiomart.com/userfeedback.php?user_id=52467#feedback_as_seller

From there you can also click on the listings and see his beautiful work.   He also did a great job rebuilding my Scott 222B. 

Glow in the Dark Audio reviewed his ST-70:

http://www.glowinthedarkaudio.com/chris-keller-st70.html

Chris and his work get my highest recommendation.  If you are fortunate enough to come across one of his products, do not hesitate, buy with confidence!   

PS:    I have no affiliation or association whatsoever with Chris and his business.  Just a satisfied customer.

[novice]

I'm leaning towards a Dynaco ST35 or ST70.

I started out with an ST70. Had ST35 on loan too. Ultimately I liked the ST70 more, especially in bass authority. Downside now is 7199 front-end tubes no longer made and originals getting pricey. For what it is it's a great tube but now would want an ST70 with a modified front-end using commonly available tubes. There are a boatload of front-end options now. Recently picked up another ST70 (At a yard sale!) but not dug into the current faves.

All that said... the Lintons are 90dB efficient. Depending on your music & listening tastes most tube amps OK there as 90dB highish. There is an issue with using the ST35 however. It has 8 & 16-ohm connections only whereas the ST70 has 4, 8 & 16. Linton's listed as 6-ohm nominal, 3.5-ohm minimum. You'd put them on a 4-ohm connection which eliminates the ST35. You could use it but bass will suffer and likely sound "flabby". Whether you decide on an ST70 or something else, make sure it is 4-ohm compatible.

[Andrew JC]

Quick update:

I did receive a reply from tubes4hifi. There are backed up with orders and new orders are on hold until they clear their back orders. That's a nice problem to have but I grew inpatient.

The good news I was able to pick up a Dynaco ST-70 that was made by Chris Keller! I was only recently able to hook it up and listen. It did sound really good but it does hum. I don't mean when I have my ear pressed up against the tweeter. I can hear it from my listening position around 8 feet from the speakers. It's not totally distracting but I can hear it nonetheless. It does stop when I touch the amp. I'm going to set it up in a different room to see if it's the amp or is it the outlet. If anyone has any troubleshooting tips I would appreciate it.

[js1955]

Quick update:

I did receive a reply from tubes4hifi. There are backed up with orders and new orders are on hold until they clear their back orders. That's a nice problem to have but I grew inpatient.

The good news I was able to pick up a Dynaco ST-70 that was made by Chris Keller! I was only recently able to hook it up and listen. It did sound really good but it does hum. I don't mean when I have my ear pressed up against the tweeter. I can hear it from my listening position around 8 feet from the speakers. It's not totally distracting but I can hear it nonetheless. It does stop when I touch the amp. I'm going to set it up in a different room to see if it's the amp or is it the outlet. If anyone has any troubleshooting tips I would appreciate it.

My Keller built ST70 is dead quiet.   Eerily so.  Like a SS amp. 

The hum may be an interaction caused elsewhere in your system, not necessarily the amp itself.  Many times in this journey I have had hum problems.  They can be pesky to figure out.  Sometimes simply disconnecting then re-connecting all the cables solves it.  Sometimes moving the gear around on the rack does it.  Sometimes plugging gear into different outlets.  Sometimes using a cheater plug to convert 3 prong into 2.  Sometimes I take a piece of cheap lamp cord,  alligator clips on each end,  and clip it onto 2 different pieces of metal in the system.  Sometimes attaching one clip to an unused RCA input, and other clip onto a metal case somewhere does the trick.   

Since touching your amp solves the problem,  maybe try the cable / alligator clip thing.  Attach one end to ST70 metal case, other end to another metal case in your system.  Or even the rack.  Or even plug it into ground hole of the wall outlet.  To accomplish this you may need to stick a nail or other piece of metal into it (be sure it's the ground hole!!) and attach alligator clip to that.

Ya just gotta play around!    Good luck.     

[mick wolfe]

Agreed. A cheater plug is a good starting point. This provided the amp's power cord has a grounding lug. FWIW, my VTA ST70 bought years ago only featured a 2-prong plug with no ground. Failing that, try the cheater plug on the pre-amp. Then it becomes a matter of unplugging source components to see if any of those could be the issue. If the grounding issue is solved with a cheater plug, consider a Hum-X as a more permanent solution.

[Andrew JC]

Another update, and there's quite a bit to cover.
I reached out to Chris Keller for help, being upfront that he had absolutely no obligation to assist me. However, Chris was a total gentleman, answering my questions and generously sharing his time and knowledge. He requested some pictures of the amp's interior, which gave me the opportunity to move the amp to a different room. There, I hooked up my desktop speakers and used a Wiim Ultra as a preamp – more on the Wiim later.

Nervously, I turned the system on. To my surprise, it was quiet. There was a slight hum on startup, but it quickly dissipated after a few minutes. Embracing an audio cliché, I even had my wife listen to confirm there was no amp hum or speaker hiss. I took pictures of the amp's interior for Chris and sent them over. I didn't see anything out of the ordinary – no burnt resistors, bulging capacitors, or disconnected wires.
Chris also didn't see anything unusual, though he seemed less than impressed with the conversion work from tube rectification to solid state. I had mistakenly thought Chris performed that modification, so I learned something new there. Knowing the amp was fine, I spent the weekend on cable management for my main system. I also decided against plugging the tube amp into the NAD integrated.

Full disclosure: even getting past the amp hum and speaker noise, I felt the ST-70 was underwhelming. Was the amp better sounding? Yes, but barely. This "upgrade" felt more like an expensive "side grade." I felt a little sick to my stomach, having spent the money and getting so little in return. Simply stated, if this had been a new gear purchase, I would have boxed it up and sent it back.

Remember the Wiim Ultra? I put the ST-70 back in my main system and paired it with the Wiim Ultra, driving the Wharfedale Lintons. I switched the amp on – no hum, no hissing. I put on Radio Paradise to stream some background music. What did I hear? A wide soundstage, impressive dynamics, holographic sound, and deep, articulate bass! I thought I'd read that tube amps had difficulty producing bass, but not this amp. I've never heard my speakers sound so good. I tossed on some vinyl, and the results were consistently excellent. I'm not trying to insinuate the Wiim is some sort of reference piece of gear; in this case, it just works. I'm not sure why the NAD "kneecapped" the sound, but it did. I'm more than happy with the outcome.

[I.Greyhound Fan]

It is all about system matching.