New chassis for the Ultimate 70 Tube Amplifier?

orthobiz · « **Reply #20 on:** 2 Jan 2006, 06:43 pm »

A short term and long term question:

Short: There's an AVA mod Dynaco available on eBay, auction ends tomorrow...

http://cgi.ebay.com/Dynaco-ST-70-with-Van-Alstine-Mod_W0QQitemZ5847345783QQcategoryZ50593QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

It has a "Van Alstine" mod, which brings up the question: how many mods are there, or better yet, can any prior modded Van Alstine be brought up to Ultimate 70 spec with your kit?

Long: Is there a guide to buying a used "wired and working" Dynaco amplifier? Any tips? Prior modifications that are good or bad? Areas of rust that will jeopardize the rebuild? I am making a New Year's resolution to buying a used Dynaco and putting in your kit. Appreciate any help!

biz

skrivis · « **Reply #21 on:** 2 Jan 2006, 07:07 pm »

Quote from: orthobiz

A short term and long term question:

Short: There's an AVA mod Dynaco available on eBay, auction ends tomorrow...

http://cgi.ebay.com/Dynaco-ST-70-with-Van-Alstine-Mod_W0QQitemZ5847345783QQcategoryZ50593QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

It has a "Van Alstine" mod, which brings up the question: how many mods are there, or better yet, can any prior modded Van Alstine be brought up to Ultimate 70 spec with your kit?

I think I've seen this amp up for sale before... ???

It's hard to tell just what it is. I think I'd advise just getting a stock amp if you can.

I also just noticed that somebody is selling new chassis for Dynas. The ST-70 is here: http://cgi.ebay.com/NEW-Dynaco-Dynakit-ST-70-Chassis-Free-Shipping_W0QQitemZ5846499710QQcategoryZ50593QQcmdZViewItem

avahifi · « **Reply #22 on:** 2 Jan 2006, 07:16 pm »

There were essentially two previous generations of AVA upgrades to the original Dyna St-70. The first was as detailed in the 1982 Audio Basics issues available as a download at our web site.

The second was the Super 70i rebuild with our own PC card design that replaced the audio, the B+ and the bias supplies. This has been in production for thirty years of so and still is a nice sounding amp.

The third and final upgrade to the Dyna St-70 chassis is the Ultimate 70 rebuild, which includes a new audio board with significant improvements to the audio and power supply and which seems to provide world class performance. Ellis Audio at their site here called it the best amp they had ever heard price not an object until some furren amp striked their fancy a bit more.

For the Ultimate 70 rebuild we suggest a correctly wired and working stock Dyna St-70 as that lets you know that the expensive big chunks, such as the transformers, are working OK. Units modifed by others may have holes drilled in wrong places, and we do not have a hole remover tool available. In general, since everything ahead of the output tube socket wiring is going to be removed and trashed, a unit with some other previous modification should work, as long as it can still accept the full Ultimate 70 tube compliment (4 x 6CA7, 2 x 6GH8A, and 1 5AR4).

There is no savings in starting with a Super 70i as the new Ulltimate 70 audio board is completely different and there is nothing to economically salvage.

The mechanical shape of the chassis is up to you and how much work you want to put into cleaning it up.

And yes, a complete new AVA Ultimate 70 amplifier is coming soon. The engineering drawings for tooling a complete new chassis went to our sheet metal fabricator today. It has all the features and functions discussed earlier herein.

Frank Van Alstine

orthobiz · « **Reply #23 on:** 2 Jan 2006, 08:07 pm »

Thanks for the replies. Frank, if a new amp is in the works, I'll probably just wait it out and see if a kit version will be available. So much for New Year's resolutions!

Although, new chassis or not, it will still need a working Dynaco, right?

biz

skrivis · « **Reply #24 on:** 2 Jan 2006, 08:49 pm »

Quote from: avahifi

Dogs, cats, kids and vacuum tube burns. I checked with other vacuum tube amp manufacturers and asked if they ever had any feedback on anyone being burned by

I was once shocked by a Heathkit W 3M, but I was an _extremely_ inquisitive kid, plus I don't think I ever grabbed any hot (temperature) pieces.

The B+ caps were 2-section can caps and the sections were in series to up the voltage rating. This meant that the can was live. They provided little cardboard sleeves to cover the caps. I was evidently intrigued with the sleeves and pulled one off. I must have touched the bare can, and got zapped. I do know it was the last time I went near the hi-fi cabinet for a long time.

skrivis · « **Reply #25 on:** 2 Jan 2006, 08:51 pm »

Quote from: orthobiz

Thanks for the replies. Frank, if a new amp is in the works, I'll probably just wait it out and see if a kit version will be available. So much for New Year's resolutions!

Although, new chassis or not, it will still need a working Dynaco, right?

biz

No, Frank indicated it will be an all-new amp.

avahifi · « **Reply #26 on:** 3 Jan 2006, 01:31 am »

The new Ultimate 70 will have everything new, including transformers. No orignal Dyna parts necessary at all.

The design will not have anything electrically hot available for anyone to touch, not even prying kids. Hot tubes will be there though, this has been discussed earlier herein.

The circuit board will be below the chassis and out of sight.

Frank Van Alstine

skrivis · « **Reply #27 on:** 3 Jan 2006, 02:16 am »

Quote from: avahifi

The new Ultimate 70 will have everything new, including transformers. No orignal Dyna parts necessary at all.

The design will not have anything electrically hot available for anyone to touch, not even prying kids. Hot tubes will be there though, this has been discussed earlier herein.

The circuit board will be below the chassis and out of sight.

Frank Van Alstine

Sorry, I wasn't implying this was or would be a problem with your amp.

The amp I was shocked by was completely different from any AVA product, is around 50 years old, and this incident happened over 40 years ago. (I still have the amp though...)

orthobiz · « **Reply #28 on:** 3 Jan 2006, 02:37 am »

skrivis:

looks like you still have the amp AND the memory!

biz

audiojerry · « **Reply #29 on:** 3 Jan 2006, 03:41 am »

If you do go ahead with this, I hope you will have a demo model with an opportunity to audition one.

Feanor · « **Reply #30 on:** 5 Jan 2006, 02:35 pm »

Quote from: avahifi

We are considering tooling a new chassis for our Ultimate 70 Vacuum Tube Amplfier so that it can be produced without needing an original Dyan St-70 chassis. It would be available both factory wired and in do it yourself kit form.

We would like your comments and suggestions for it's design.

...

Frank, I would very much someday like to build a tube amp kit in the spirt of the Dyna Stereo 70. Many years ago when I was young I opted to build a Dynaco Stereo 80 (solid state) kit instead of the Stereo 70 -- I came to regret that decission. I have lived with solid state ever since but how different it might have been!

In terms of form factor, I'm not a huge fan of the glowing-tubes-on-top look. I'd rather have a box (like the FET/valve): controls and adjustments on front; connections on back, i.e. 4, 6, 8 ohms.

skrivis · « **Reply #31 on:** 5 Jan 2006, 02:45 pm »

Quote from: Feanor

Frank, I would very much someday like to build a tube amp kit in the spirt of the Dyna Stereo 70. Many years ago when I was young I opted to build a Dynaco Stereo 80 (solid state) kit instead of the Stereo 70 -- I came to regret that decission. I have lived with solid state ever since but how different it might have been!

In terms of form factor, I'm not a huge fan of the glowing-tubes-on-top look. I'd rather have a box (like the FET/valve): controls and adjustments on front; connections on back, i.e. 4, 6, 8 ohms.

I actually do like glowing tubes in plain sight. It reminds me of when I was a kid.

Watson · « **Reply #32 on:** 5 Jan 2006, 03:29 pm »

I wouldn't buy an amp where the tubes weren't in view. The glowing tubes, especially in the dark, are a big part of the intangible romance that tube amps have.

Feanor · « **Reply #33 on:** 5 Jan 2006, 06:25 pm »

Quote from: skrivis

I actually do like glowing tubes in plain sight. It reminds me of when I was a kid.

Everyone to his own, I guess

elcaptain88 · « **Reply #34 on:** 22 Feb 2006, 10:29 pm »

Any updates on when the 'new' Ultimate 70 might become available? I almost pulled the trigger on a new Fetvalve amp - but waited when this product was announced. I'm resigned to replacing my Bryston amp - which is good but sounds a bit on the lean side with most speakers I've tried for my tastes. The 70 sounds like it may be just the ticket.

WEEZ · « **Reply #35 on:** 23 Feb 2006, 12:25 am »

elcaptain88,

a tubed amp will almost certainly not sound lean- unless it has tons of feedback- but even then...it won't sound like a transistor amp.....

You're thinking along the same lines as me at the moment.

Frank- any chance that a demo model could be sent around to interested parties?- even at a nominal fee?

WEEZ

avahifi · « **Reply #36 on:** 23 Feb 2006, 02:16 am »

Hey wait until we get the new prototype sheet metal (due near the end of this month) and put one together and debug it, OK?

Questions to be answered:

Will having a front panel power switch increase noise? AC has to run up to the front past the circuits to do this.

Will having rear panel RCA inputs increase noise? They will be closer to the power transfomer and the shielded input leads will have to pass closer to the transformer.

What is it going to cost us to build it? Parts, labor, and normal "headaches" time? Estimated cost to do a kit manual (time I would like to get paid for eventually), cost effective to even offer it at a do it yourself kit?

All these dear friends remain to be determined. Will it be just another good idea that doesn't get where we want it to, or will it be the awesome tube amplifier we are hoping and planning for?

We will be building the first one up in March, I suspect, available skilled help pending (lots other things to do like fill your existing orders, thank you).

Frank Van Alstine

Frank Van Alstine

EMM801 · « **Reply #37 on:** 26 Feb 2006, 04:51 am »

I have a question about this project: According to an interview with David Hafler in "Vacuum Tube Valley", Dynaco amplifiers had an unusual output transformer winding arrangement for which they took out a patent. I wonder what if any role this may have had on the performance and sound. I knew a guy who worked in the patent office and he couldn't obtain a copy (strangely, the same was true of a couple of the Dynaquad patents too, but I digress). AVA have any thoughts about this?

P.S., Im also recalling not much nice to say about tube amps in the old "Audio Basics"... This seems an interesting change of mind. The economics are better answered by someone else. But I know companies like ASUSA went under trying to offer reasonably priced tube electronics. It would be a real adventure.

avahifi_lj · « **Reply #38 on:** 26 Feb 2006, 05:27 am »

Hi:

Good questions, and I'm sure Frank will have a bit more input....

From what I have heard, the Dyna 70 transformers are indeed a bit unique. Most everyone puts them in high regard as one of the finest audio output transformers made. The power transformer, on the other hand, is not near as good.

As for the patent, I don't know the status of it. I do know, however, that there are at least two companies making replacement transformers. One of the manufacturers (if not both) claims their transformers are virtually an exact duplicate of the Dyna 70 transformer.

In the past, we have been a bit reluctant to design a tube amplifier. One of the reasons is the higher maintenance/service needed to maintain the tube amp. With solid state amps there is virtually nothing to service, and they run for a LONG time. Even our Hybrid FetValve Ultra amps run for years with very little maintenance because the output devices are not tubes. We were not convinced that our customers would be willing to deal with buying new tubes and adjusting the amplifier as the tubes aged. Since the introduction of the U70 upgrade for the Dyna 70 we have received a lot of request for the amp from those who do not have an original Dyna 70. This is one of the reasons we are looking at introducing the amp in an AVA chassis.

Another key reason we were not too keen on tube amps was the inability of the amp to sound anywhere as good as our OmegaStar and FetValve Ultra amps. Part of the problem with the old tube designs was the availability of parts. Today we have access to a much wider selection of high quality parts that have greater capacity and much tighter tolerance. These new parts have allowed our engineering team to look at tube circuits in a way not possible 10-20 years ago.

I continue to be amazed at how nice the U70 sounds. In comparison to the Super 70i, the U70 has much much more to offer.

Thanks for your interest in AVA products!

Larry

EMM801 · « **Reply #39 on:** 26 Feb 2006, 01:45 pm »

Quote from: avahifi_lj

Hi:

As for the patent, I don't know the status of it.

The patent was issued at the start of Dyna's life (1953-1954), so even if Dyna renewed it, it would have long since expired. So other companies could very well have been copying them since. I was just curious whether they had any unusual electrical characteristics as a result of this that would have had an effect on performance. Evidently Dyna thought so, since the basic design was used on all their tube gear. Buit then, McIntosh has some funky scheme for winding theirs too, which they think is best...

Does thinking about a question like this make me an audio nerd? Naaah, I was already an audio nerd...