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Preamp to use with Dynaco ST-70?

Magnolia Tom said:
He stated it was looked at by a technician and passed with flying colors
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That may not be very meaningful. Did the seller say who did the work and what they were paid to do? I see older tube gear on eBay all the time that's been "serviced" or "refurbished," but interior photos say otherwise. In any event, I agree with mrwood200 that it should be checked out before use. Much of the amp appears to be original, and those parts have a lot of years on them.

Jack
 
TriodeLuvr said:
That may not be very meaningful. Did the seller say who did the work and what they were paid to do? I see older tube gear on eBay all the time that's been "serviced" or "refurbished," but interior photos say otherwise. In any event, I agree with mrwood200 that it should be checked out before use. Much of the amp appears to be original, and those parts have a lot of years on them.

Jack
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This was an impulse purchase after a few adult beverages. I’ll check it out before using it and go from there. I feel like I got a decent price on it compared to others listed in similar condition. If it needs service, so be it. That’s the consequence for impulsive buying lol
 
TriodeLuvr said:
That may not be very meaningful. Did the seller say who did the work and what they were paid to do? I see older tube gear on eBay all the time that's been "serviced" or "refurbished," but interior photos say otherwise. In any event, I agree with mrwood200 that it should be checked out before use. Much of the amp appears to be original, and those parts have a lot of years on them.

Jack
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Judging by the pix, I see new coupling caps and some fresh electrolytics underneath. Looks like the selenium rectifier is still there, and a lot of the old carbon comps, but it's clean underneath. I'm going to guess that whatever was left in there measures okay. And hell, the OP got a quad of Mullard EL34s, a Mullard 5AR4 and two original 7199s! Nothing looks toasted or even particularly worn, except for the weathering on top. I'd say he got a good deal, probably sounds great.
 
Magnolia Tom said:
I just made an impulse buy of an ST-70 and should be getting it delivered next week. I bought it because of all the reviews praising the mid range and how the music has a 3D (holographic) quality. I’ll mainly be listening to Jazz. My question is on a preamp.

I planned on using my pioneer sx-838 as the preamp. Speakers are some Klipsch floor standing with 96dB efficiency. I will be playing vinyl mostly. Will this setup work well? Or should I look into getting a tube preamp?

I’m a complete novice on tubes, tube amps, etc so any guidance would be greatly appreciated.

Btw, pictures are coming once I receive the amp. I had a saying on RV forums….”Pics or it didn’t happen”.lol. Not sure if that’s a thing here but I’ll be sure to post some when I get it.
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you may want to consider one of the Chinese clones of the Marantz 7 tube preamp. Its a great match for the ST-70.
 
I’ve been researching Dynaco preamps and one video I watched stated the phono stage not being that great. Can’t remember if it was a PAS3 or PAS2. Any validity to this?
 
I modeled the PAS phono in SPICE a number of years ago. I seem to remember there were several shortcomings. I'm sure this has been thoroughly addressed in various forums and websites, either through modifications or replacement boards. I don't buy vintage preamps or integrated amps myself due to the lack of replacement controls and switches. In your situation, I would probably buy Bottlehead, as someone else suggested.

Jack
 
Magnolia Tom said:
I’ve been researching Dynaco preamps and one video I watched stated the phono stage not being that great. Can’t remember if it was a PAS3 or PAS2. Any validity to this?
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A lot of unwarranted criticism of the PAS has been propagated on various forums over the years, and especially in regard to the phono stage. A comprehensive technical review of the PAS is presented in these articles:



And for the ST-70, Dave Gillespie's excellent Base Line Testing article:

 
Magnolia Tom said:
I’ve been researching Dynaco preamps and one video I watched stated the phono stage not being that great. Can’t remember if it was a PAS3 or PAS2. Any validity to this?
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There are upgrades available. Other options are from Van Alstine. He did several upgrades and lots of Dyna-like preamps that can be found used. Phono stages are better in all variations I would think.
 
TriodeLuvr said:
Norman Koren has posted a complete write-up of the PAS phono preamp online. This is the most complete technical evaluation anywhere, as far as I know.

Norman Koren PAS Phono Analysis

Jack
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Unfortunately, his model contains numerous errors including both schematic and supply voltage, resulting in misleading conclusions. Furthermore it should be noted that there are significant variations in modeled response, particularly low end, among the various available 12AX7 subcircuit models, as applied to the PAS phono circuit. You can't just "Spice" it and proclaim a result in this case. You need an actual unit, plus a selection of good tubes, and real measurements.
 
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All of this technical information is way above my pay grade. I think for now I’m just gonna go with the Pioneer as the preamp and start learning more about the world of tube gear. I need to hear how it sounds before I start looking for a tube preamp. Heck I may check out a cheap Chinese brand like Fosi or douk to experiment with before buying a vintage piece. Thanks everyone for your input! This place is a wealth of knowledge and I hope to be able to contribute to it
 
Masonavenut said:
I’m sorry but I don’t understand this sentence. Need? :dunno:;)
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Fair, I just know it wouldn't be likely to get a lot of run time, so I have a hard time justifying money for a shelf queen. I'd still pick one up if it was cheap enough but I have no reason to shop for or pay going price for one currently. I already have 2 el34 amps.
 
So I bought a Fosi phono “tube” preamp and just got it delivered a little while ago. All I can say is wow! Everything sounds much clearer and cleaner now. Almost like I had pillow cases over my speakers that got removed. Even my wife could hear the difference. I can’t wait to get the ST70 added to the mix to really get that sweet tube sound. I always thought the phono stage of vintage receivers were top of the heap but this cheap phono preamp puts the pioneer phono stage to shame. I’m really shocked at how good it sounds. Getz/Gilberto (Girl from Ipanema) never sounded so good!
 
audioregen said:
Unfortunately, his model contains numerous errors including both schematic and supply voltage, resulting in misleading conclusions. Furthermore it should be noted that there are significant variations in modeled response, particularly low end, among the various available 12AX7 subcircuit models, as applied to the PAS phono circuit. You can't just "Spice" it and proclaim a result in this case. You need an actual unit, plus a selection of good tubes, and real measurements.
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Tweaking a phono pre for perfect response is one thing, but checking basic functionality is something else. I don't have a PAS, nor do I use feedback phono EQ, so my take on this product isn't as highly refined as some. Also, I don't remember all the details after more than 10 years. Nevertheless, I'm pretty sure my model showed it to be lacking in dynamic range, and I seem to recall Norman Koren (whose work I read later) said the same. I have no wish to revisit any of this at this point, but I think it's sufficient to say performance of the original is less than stellar, and that modifications or upgrades (or replacement altogether) are worthwhile. It definitely wouldn't be my choice for a preamp as-is.

Jack
 
Got the ST70 today. Did a quick look over and it’s in pretty good shape. Plugged in all the tubes and powered it up. 1.55 V at each channel. Hooked it up to the pioneer sx838 and played some vinyl. Damn this thing sounds awesome!

One annoying thing is I bought some nice RCA cables and they don’t fit because the jacks are too close together. So I had to use the el cheapo cables
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Congrats on getting a nice ST 70 and glad it is sounding good!

I am using a Mac C41 Preamp for my 2018 Dynakit ST 70 build. It sounds very good to my ears. I also have a modern Dynakit tube preamp built by the same person who built and owned the ST 70. Have not paired them together yet but will in the future.
 
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Glad to hear it's working well!
Magnolia Tom said:
One annoying thing is I bought some nice RCA cables and they don’t fit because the jacks are too close together.
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Many older preamps and amps were designed that way, it was before the days of boutique cables. The cables you're using should work just as well, but I would spray a little Deoxit on both ends and probably try to replace them every two years or so.

Jack
 
There is a new input jack with slightly wider spacing. I think they come from Triode but if not it's the other vendor I cant think of for ST70 stuff that escapes me right now

Or diy some with switchcraft 3502a plugs. They fit the old spacing
 
gadget73 said:
There is a new input jack with slightly wider spacing. I think they come from Triode but if not it's the other vendor I cant think of for ST70 stuff that escapes me right now

Or diy some with switchcraft 3502a plugs. They fit the old spacing
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Got mine from Tubes4hifi.com
 
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