[sfox7076]

Looks like the board has changed a bit from mine.  Wonder if there were any revisions of note, or just part changes.  Anyway, I am not getting the $750 for mine, so it is going to sit in a closet for a bit.  No way I am selling it for less than that.

[avahifi]

No changes in the Ultimate 70 board but there have been some changes in parts vendors.  Same values, same quality, but some parts different in color and/or external shape.  No big deal.

Frank

[Rocket]

Hi Paul,

Thanks for posting about the restoration process of your rebuilt amplifier.

Cheers Rod

[orthobiz]

I'm on vacation but that didn't prevent me from ordering some Blue Jeans cables. I may set them up temporarily at work just to see how everything meshes together. I bought a demo pair of Neat Acoustics Motive 3 speakers and Sound Anchor stands. I'll post some pics when it all happens.

Paul

[HollowJane]

I'm on vacation but that didn't prevent me from ordering some Blue Jeans cables. I may set them up temporarily at work just to see how everything meshes together. I bought a demo pair of Neat Acoustics Motive 3 speakers and Sound Anchor stands. I'll post some pics when it all happens.

Paul

I love the robustness of the Sound Anchor stands, good choice

[orthobiz]

I love the robustness of the Sound Anchor stands, good choice

Jim Pendleton of Osage had them made, custom tops to fit the speakers. He said if I didn't put the speakers on them, I could use them to hold up my car instead of jacks. I think he's right!

Paul

[simon wagstaff]

Rather than start a new thread and since this seems to be a U70 thread I did want to post something from the Hoffman forums. This guy presumes to speak for Frank, and I would like for Frank to see this and perhaps comment, if you like. I don't want to stir up any trouble, well, maybe a little, but I think if somebody is posting "Well, this is how Frank thinks" then i would sort of like to know if in fact Mr. Van Alstine does in fact think this way. I think the main point of this fellow's thread is that the Dyna transformers are not that great and there are better ones out there. I think certainly that may be true, but you can't deny that the U70 is a mighty fine sounding amp and equal of anything modern at it's price point and above. I still love my U70 and the magic it can produce.

From the thread "dynamo once more" on the Hoffman forums.

he said

"Much of the criticism, and much of the fame of Dynaco is actually based on its most (commercially) successful product, the Stereo 70 tube amplifier. Dynaco made many other products as well, but the ST70 was probably produced in volume greater than all the others put together, and was sold for at least thirty years. Variants are still being sold by multiple vendors in kit or finished form.

Plus which, no matter how much time and new parts you put into it, a ST70 will never equal the performance of many newer products."

Me
"I respectfully disagree. I have an Audio by Van Alstine U70. Depends on how you define new parts and time. Does the U70 qualify? It's basically an Ultravalve, which has been favorably reviewed by the Absolute Sound. My U70 is as good as anything that I have heard out there currently, and still seems, to me at least, to have some sonic magic in there as well. I love my U70!"

he said

"I have spoken with Frank and his daughter Vanessa, who wrote a paper that is fairly good on amplifier design (will find a link on request), they are nice people, but I don't get why he chooses to keep using these old circuits and especially the old Dyna output transformers. I think he secretly feels that the solid state stuff is really the way to go and if people want tube amps with output transformers the Dyna is good enough: or it could be price: he can get the Dyna parts cheap."
 

[Lefty052347]

I worked next to Frank for 5.5 years.  I have had the U70 and Ultravalve amps in my home system.  (I did the builds on both.)  To my ears they are virtually identical.


he said

"I have spoken with Frank and his daughter Vanessa, who wrote a paper that is fairly good on amplifier design (will find a link on request), they are nice people, but I don't get why he chooses to keep using these old circuits and especially the old Dyna output transformers. I think he secretly feels that the solid state stuff is really the way to go and if people want tube amps with output transformers the Dyna is good enough: or it could be price: he can get the Dyna parts cheap."
 

I say

Bulls#!t.

Regards,
Dean

[avahifi]

Obviously that guy has not spoken to me in years and he certainly does not speak for me at all.

By the way, I have a prototype Ultravalve amplifier running with Magnaquest output transformers and a high current Triode power transformer.  Aside from making a few more watts, 40 per channel vs 35, we can hear no difference at all between this amp and a stock Ultravalve which uses new Dynakitparts supplied transformers to our specifications.

The reason for the sonic excellence of the Ultravalve (and U70 too) is not the parts quality (although quality parts are selected), it is the circuit design.  The main "secret" to the design is multiple regulated power supplies, a separate one for each plate of each small signal tube along with a very stiff output tube supply.  This, combined with a design philosophy that does not allow any stage to be driven outside its linear bandwidth capabiity at any frequency short of output clipping, yields in essence a screw up proof amplifier.

By the way, our test speaker for burning in Ultravalve and U70 amplifiers are a pair of Janszen zA2.1 electrostatic speakers, about as high definition as anything out there.  The amps better sound great on our Salk and Philharmonic speakers too, and they do.

Regards.

Frank Van Alstine

[rcag_ils]

Sadly, in today's market, it's always "look" comes first, and "sound" second.

[orthobiz]

Getting back to my rig, I hooked up the Ultimate 70 Frank just redid to the PAT THREE I bought from him. I have a pair of Neat Motive 3 demo speakers I bought, so I made a system for my office. I have the Sound Anchor stands custom cut at the top to accommodate the size of the speakers.

Unfortunately, I need to get a turntable in the office and so far I've only hooked up my iPod so the sound is not that great...bad source MP3 for sure! Also, the speakers are 85 dB sensitive so I think a little bit more power would help. In the meantime, I hooked up another AVA amp I have, also built into an old Dyna chassis and it has 100 watts per channel, it gets better sound from the iPod for sure presumably because of better headroom.

Anyway, I just bought a pair of A25 Dynaco speakers on eBay and will report back on the Ultimate 70 in a few weeks, hopefully with a few pictures. BTW, I'm happy with the AVA stuff, I'm just tweaking and fiddling right now!

Paul

[dB Cooper]

The A25 is not all that sensitive but is noted for its flat impedance curve which makes it very easy to drive. Should be very simpatico assuming ear splitting levels aren't on your want list.

[sfox7076]

Mine has made it to work.  No sense in giving it away...







Shawn

[sfox7076]

And not to raise the ire of the masses, buy an old Mullard rectifier.  Not sure why, but it really makes a difference.

[avahifi]

Your NOS Mullard rectifier tube really made a difference?

Interesting, because in an Ultravalve amp or factory wired Ultimate 70 amplifier the rectifier tube really is not doing the rectification at all!

The work is being done by a pair of 1N4007 diodes ahead of the rectifier tube.  The rectifier tube is retained essentially because is provides a useful soft start circuit and as a dropping resistor to keep the B+ voltages at the appropriate level for the circuit.

The only place I can understand a "good sounding" rectifier tube making any difference at all is if the old one was aged or out of spec and providing too low a rectified voltage output.

Sadly, anticipation bias drives way too much of this hobby.

Frank Van Alstine

[simon wagstaff]

I installed the diodes just 2-3 years ago. I had issues with the rectifier tubes until I put in the diodes. Maybe the above poster has an older amp? The choke thing REALLY improved the sound and all I had to do was move a couple of wires. Love my U70!

[heiba]

I love mine too!

Ola
Norway

[sfox7076]

No affiliation with this sale, but here is a place to start http://www.audiokarma.org/forums/showthread.php?t=661836 if someone wants a similar project.

[Wayner]

No affiliation with this sale, but here is a place to start http://www.audiokarma.org/forums/showthread.php?t=661836 if someone wants a similar project.

Why did you drag me into this?