Bought a Dynaco ST-70... Need Preamp and tube upgrade recommendation

dneu201

dneu201

Well-Known Member
I bought a restored Dynaco ST-70 from Jimi55, but need to upgrade the output tubes and get a different preamp. Currently, my setup is a a Technics sl-1200mk2, Yamaha CA-1000iii(current preamp), Dynaco ST-70, and Yamaha NS-1000ms.

I love the sound of the Dynaco over the Yamaha CA (as my amplifier). With the yamaha the sound was too bright and metallic sounding. The Dynaco has really mellowed the speakers out, but I need to upgrade my tubes and get a new tube preamp. Here are options I have considered for each:

Tubes ($200 budget): JJ Tesla EL34, Mullard Reissues EL34, SED Winged C (current tubes are unknown Chinese EL34), or something else??

Preamp ($500 budget): Dynaco Pas2 (at local store, has some upgrades for $250 & includes Dynatuner), Counterpoint SA-7 (on Craigslist new transformer and serviced $400), Bottle Head Smash ($500 and would be my first kit), or something else???

Any input would be great! Thanks.
 
If those Chinese EL34s are the same Shuguang tubes as the Valve Arts- they're not bad at all in a ST70. I have used several sets in those, with very good results. They, to me, are better than the current production JJ or Winged C tubes in that amp.

I haven't done a comparison with the reissue Mullard EL34s, so I can't comment on that, unfortunately. That said, the EH 6CA7 (fat bottle) tubes also sounded good in those amps. I haven't used a set in a while, so I can't comment on whether they still stack up that way (other EH output tubes have had some consistency issues, but I'm not sure how the 6CA7 fares there)...

I have a possible suggestion for a preamp- but it will be better if I send you a conversation message about that...

Regards,
Gordon.
 
Have used the JJ E34L and liked them. Currently have EH 6CA7 and like them a lot too. Personally I have always used Bottlehead preamps with mine and been very happy. Don't know anything about how the Smash would be. I would wait for a a Foreplay II or III on ebay personally.
 
Any of the tubes will do, but make sure they are well matched at proper working voltages. Some vendors
do this, other uses some old tubetester that test at low voltages, that won't work. Also make sure
the vendor is reputable and well regarded, that's worth more then a low price! ( in case of problems). Even better
is a matched quad as you can mix and use the remainder in any combination if one or two goes south.
 
peterh said:
Any of the tubes will do, but make sure they are well matched at proper working voltages. Some vendors
do this, other uses some old tubetester that test at low voltages, that won't work. Also make sure
the vendor is reputable and well regarded, that's worth more then a low price! ( in case of problems). Even better
is a matched quad as you can mix and use the remainder in any combination if one or two goes south.
Click to expand...
+1 Dneu- adhere to this.

Also if you tubes ARE Shuguang, dump them. Only decent Asian tubes anymore are PSVane.
Wonder if you can bias up a great new set of Genalex Gold Lion KT77's in lieu of any EL34. Ive had great luck with the Lions.
 
KKnight said:
+1 Dneu- adhere to this.

Also if you tubes ARE Shuguang, dump them. Only decent Asian tubes anymore are PSVane.
Wonder if you can bias up a great new set of Genalex Gold Lion KT77's in lieu of any EL34. Ive had great luck with the Lions.
Click to expand...

There isn't a brand on the tubes; they only say EL34. As far as the Gold Lions are concerned, it looks like I can get them for $184 from mcshanedesign.net. These look to be at the top of my price range and I think I will pull the trigger. How do these compare to the EL34 version?? I was told the EL34's are great for my Yamaha NS-1000m's; will the KT77's be that much more of an enhancement? I'm all for making the purchase if I can get them biased correctly and it will make the Yamahas sing!

Thanks for all the feedback!!
 
Paully said:
Have used the JJ E34L and liked them. Currently have EH 6CA7 and like them a lot too. Personally I have always used Bottlehead preamps with mine and been very happy. Don't know anything about how the Smash would be. I would wait for a a Foreplay II or III on ebay personally.
Click to expand...
No foreplays on ebay right now but I would love to build one of these kits for experience. It would be my first and I would eventually want to build a Bob Latino ST-70 but would need practice first. How are the instructions for a newbie building the Bottlehead?
 
A grounded cathode, 12B4 can comfortably run from a B+ around 200V. 300 is easier. The heater can be done with a DC wall wart( solder post-switch onto the wall plugs, and run the output to the right tube socket pins. A volume pot and good coupling caps round out the rest of the circuit. 12W, wire wound Mills resistors do quite well for plate loads. a 300-0-300 Hammond, a choke, and a big pile of capacitance( rigged as a L-C filter ) will do a fine job. One of the new 5AR4's or cheap 6W4 damper diodes will do for rectification...:) A foot square chassis plate should leave plenty of room.
cheers,
Douglas
 
I use a lot of Valve Art EL-34s in anything from guitar amps to hifi never had a failure or complaint on the sound. They're inexpensive to boot.

Craig
 
peterh said:
Save your money ( or buy some records) that enhances your listening experiencemore then changing one set of
EL34 to another set of EL34
Click to expand...

I really agree with Peter here. I have some NOS unknown Chinese tubes in my ST70 now and they sound very good. I have Mullards, Philips and other tubes I could use, but the Chinese ones are performing fine.

If you play vinyl, spend your cash on the best tube phono stage you can afford and experience a really audible upgrade. But, YMMV.
 
You would probably get more bang for your buck replacing the driver tubes

KKnight said:
Also if you tubes ARE Shuguang, dump them. Only decent Asian tubes anymore are PSVane.
Click to expand...

Right, and all the places that use Shugang as OEM suppliers don't know what they are doing ...
 
Dandy said:
Three different reviewers on TNT Audio have reviewed Shuguang tubes at different times in the past and found them to be high quality. See here for example: http://www.tnt-audio.com/accessories/shuguang_6l_e.html
Click to expand...

You are quite correct.Presently. But I remember (old fart here!) back when Shuguang power tubes had more in common with flashbulbs than amplifying devices.

My guess is that demand,time,and probably most importantly,competition,are the reasons for their newfound reputation.Unfortunately,back in the day,this company had an absolutely dismal reliability record.
 
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