Jump to content

Dynaco ST-70: Good 1st Power Amp w/Khorns?


fini

Recommended Posts

  • Replies 70
  • Created
  • Last Reply

Top Posters In This Topic

Fini, I got the ST70 back from Mike in perfect order(chalk one for the good to UPS.) The hum in your Fisher could be from a cap or a transformer, but it probably wouldn't be a good idea to use the Fisher preamp side with an amp- kinda skating on thin ice.

If you want, I could repack the Dynaco and turf it out to you along with either a Creek passive preamp(with only a single line stereo input...no turntable) or a '70s Nakamichi 420 SS preamp. Both preamps are solid and would not embarrass the wife when she has a tea. Just send the preamp back when you locate one that follows you home2.gif

As Mark noted, it is a slippery slope trying to drag vintage iron up the repair hill. I don't think you'll have worries with this one, and it has a good cage so you won't have to curtail playing hai alai in your library...

Link to comment
Share on other sites

fini, I am no expert, but that Fisher will give you good sound and will also clean up your rack. (No jokes here, okay?)

I have an 800-B and, from what I have read, your 500 is a comparable unit.

The reason the ST-70 is modded, is because it NEEDS to be modded. The bass of the ST-70 in stock condition is flat, boring, dead, dull, made for 50 year-old speakers. The Fisher will give you a terrific tuner as well as a terrific amp just with some upgrades. No circuit REPLACEMENTS, as is often the case on modified ST-70's. I don't even think the ST-70 looks that great. I had one. I also sold one. I am working my inventory down and the Fishers are staying. It's kind of like Volvo owners can't afford a Mercedes. i.e., I can't afford McIntosh.

Link to comment
Share on other sites

With all due respect, Klipschfoot, I beg to differ. The 70 when brought back to specs has a bottomless pit for bass. Fast, bouncy, deep, well-controlled, well-defined bass. Just brought back to specs, mind you, not modified beyond recognition.

Care to venture a guess as to why a 40 year old stock, un-restored 70 has no bass?

By your logic, then a MkII should have flat, dull bass, and so should a McIntosh MC30, and even a Fisher 500.

After all, *ALL* speakers of the era were bass-deficient, right?

Someone forgot to tell PWK that, someone forgot to tell JB Lansing that.

Link to comment
Share on other sites

Yeah, I know. But at least it's not a bastardized hack, and still uses the original ckt.

The bass came back bigtime with a fresh can cap, but a little problem remained -- when running near full throttle, the most extreme low end would flutter. (Flutter is the best i can come up with.) Funny thing is, after I did all that I ran across a review from High Fidelity, 1959, where they graph the same exact thing -- at full throttle, from 20 to about 30hz it dips. It was indeed very thin on the psu from Day One. Mind you, that's at 35 watts.

Then again, I was testing into really in-efficient speakers, on purpose, to see the limits. The cap upgrade removed that flutter.

If you full-throttle a 70 into Klipsches, you'll likely get blown into the back wall.. 3.gif

It just irks me that so many folks (it's not bad here, but in AA it's way bad) think the 70's bass-light.. it ain't. That can cap goes flat a lot faster than whatever McIntosh and other builders of higher-priced gear used. That flat can-cap is what gives it its tired, flat, flabby, thuddy sound... once it's replaced, the amp is no longer a warm, cuddly, gentle amp -- it has fangs. I wrote a review on AA about the 70 after restoration to enlighten those who parrot other's opinions / experiences without actually restoring one themselves.

The board I use keeps the section just after the 5AR4 near-stock (60uf, I think? Maybe even 30) but just about triples everything after the choke. The diff between a flat can and a new can was night-and-day. The diff between the new can-cap and the sds board was oh so much subtler.. but appreciated.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...