AVA Mod Dyna Pat-4....WOW

EV-MAN · « **on:** 16 Mar 2006, 03:04 pm »

Built a Dyna Pat-4 kit back in the Mid 70's. Used it for 10 to 15yr's. Put it with the rest of the junk sorta forgot about it. It was a OK little preamp. Went to a friends house that has a system that he put together. Walked out his house with the fever..... So here I am again. Went to surfing the web looking at the new stuff & vintage. Ran across Van-Alstine started reading on his web site. Found where he had done some mods back in the 80's for the Pat-4. Replaced the caps on the boards. Built the new power supply which is much more powerful & did the other things he recomended. And now the good part. This little preamp that was OK is now FANTASTIC... You would have to pay several hundred dollars to get one as sweet as this one. Talked to Frank several times on Phone & email. Asked a lot of dumb Questions About this old junk. Frank thanks for making it fun for me again. Well it's off to the next project. HAPPY SOLDING

markjohnson22@comcast.net · « **Reply #1 on:** 19 Mar 2006, 02:03 pm »

Greetings EV-Man, Great story. I have been using my Van Alstine Modified PAT 4 for the past year. I had it modified by Frank in 82 (I do not even remember what he did to it). It is very very clean sounding but I have been looking for a newer preamp and have listened to several other units.

Based on recent auditions of other units my PAT 4 seems to have great low frequency performance (nice and tight) but does not deliever in terms of imaging / and depth in the mids (cannot get a good center sound, not as musical as the others).

Did you perform recent modifications on your PAT 4? If yes what did they include?

Thanks

avahifi · « **Reply #2 on:** 19 Mar 2006, 06:11 pm »

You guys are talking about what is essentially a "patch" to the original Dyna Pat-4 circuits I did 25 years ago.

Although it was nice and helped the original circuits a lot by fixing some of the worse case problems, it is not remotely close to any of our modern preamplifiers.

Frank Van Alstine

markjohnson22@comcast.net · « **Reply #3 on:** 19 Mar 2006, 07:16 pm »

Frank, Thanks for the response, I happened to turn over the unit and found the Super FET PAT 4 Preamp, 10/82 sticker. Inside I found Transcendence Boards, bypassed tone controls, origional transformer, etc. It is all starting to come back to me.

I agree with you comment regarding the difference between older stuff and the new designs and I am considering a new OmegaStar SL.

MJ

Listens2tubes · « **Reply #4 on:** 19 Mar 2006, 10:26 pm »

Mark. you should be looking at the Transcendence 8. IMO

skrivis · « **Reply #5 on:** 20 Mar 2006, 02:35 pm »

Quote from: Listens2tubes

Mark. you should be looking at the Transcendence 8. IMO

The OmegaStar SL is also a very nice preamp.

avahifi · « **Reply #6 on:** 20 Mar 2006, 02:50 pm »

If that old Pat-4 has our "Transcendence" boards in it, then it is a lot more than a "patch", it is actually a first generation set of our complete new solid state preamplifier circuit boards installed, our own circuits, discarding the Dyna originals. It will be a very nice preamplifier indeed and probably has our original series of Noble precison volume and balance controls too.

Frank Van Alstine

markjohnson22@comcast.net · « **Reply #7 on:** 20 Mar 2006, 11:36 pm »

Frank, You are correct, it does have the upgraded volume and balance devices. Are there any "practical" upgrades for this thing (power supply, bypassing all of the other non-essential filters, mono stereo switches etc.) thank might give it some life.

As I mentioned (based on comparisions with other units) the lower end seems to perform fine but separation, and mid to high frequencies are just plain flat (no depth or imaging).

Thanks for your thoughts.

MJ

avahifi · « **Reply #8 on:** 21 Mar 2006, 04:12 pm »

You are looking at design limitations of that 25 year old circuit design, not parts quality or power supply capacitor values. It was excellent for its day, but its day is pretty much long gone. Tacking "better sounding parts" in will be just a waste of money. Snakeoil still is very very big out there.

If you want better, you would need our new OmegaStar audio circuits installed. The upgrade price is $599 for any Pat-4 or Pat-5 with any of our previous generation circuit sets. The upgrade includes all new internal audio circuit boards and parts (new design) and lots of rewiring.

Frank Van Alstine

avahifi · « **Reply #9 on:** 21 Mar 2006, 04:15 pm »

You are looking at design limitations of that 25 year old circuit design, not parts quality or power supply capacitor values. It was excellent for its day, but its day is pretty much long gone. Tacking "better sounding parts" in will be just a waste of money. Snakeoil still is very very big out there.

If you want better, you would need our new OmegaStar audio circuits installed. The upgrade price is $599 for any Pat-4 or Pat-5 with any of our previous generation circuit sets. The upgrade includes all new internal audio circuit boards and parts (new design) and lots of rewiring.

Frank Van Alstine

EV-MAN · « **Reply #10 on:** 23 Mar 2006, 05:15 am »

Bought a Omegastar2 off ebay about a year ago. Sorta strange nobody was biding a whole lot. It was going to sell at about 2 in the morning. It was getting late had to go to bed. Did not think I would win it, so before I went to bed I bid $55.00. Got up the next morning checked and I won it. It has the first generation boards & noble pots just like Frank said. It really sounded good until lately. It still sounds clear but you have to turn the volume up much more now.. It just does't have that killer power anymore. Sure it sounded better than the Pat-4 with the early mods. So the old Pat-4 with early mods will do till I get the extra cash to get one of Franks latest models. But if you got a old Pat-4 & want to have some fun. MOD it. Compared to the stock Pat-4 it made a huge difference.

skrivis · « **Reply #11 on:** 23 Mar 2006, 02:13 pm »

Quote from: EV-MAN

Bought a Omegastar2 off ebay about a year ago. Sorta strange nobody was biding a whole lot. It was going to sell at about 2 in the morning. It was getting late had to go to bed. Did not think I would win it, so before I went to bed I bid $55.00. Got up the next morning checked and I won it. It has the first generation boards & noble pots just like Frank said. It really sounded good until lately. It still sounds clear but you have to turn the volume up much more now.. It just does't have that killer power an ...

Maybe you should send the OmegaStar back to AVA and have it checked out? The OmegaStar circuits really are excellent, and even if you have to pay for repair, you've still got quite a deal.

I just sent my OmegaStar SL preamp back to have phono circuits added. I had toyed with the idea of moving to an Ultra preamp, but I just keep thinking how happy I am with the OmegaStar and wonder if I'll be $1500 happier with an Ultra.

With all of my previous AVA equipment, I certainly liked it, and it worked as well as anything else out there for far less cost. But... I also kept waiting to see what Frank would come up with next. I got the feeling there was more to be had.

With the OmegaStar equipment, I'm continually amazed at how good it sounds. There's a lot of "wow" factor. And it's not as if its adding anything or accentuating anything to grab your attention. It's very neutral and lets the music through. I'm just pleased as punch with my OmegaStar DAC, preamp, and amp. They're some of the best purchases I've ever made. I got them 5 years ago, and I'm still happy with them. I know people who have gone through dozens of components in that time. I just smile and keep on listening to the music.

daveshel · « **Reply #12 on:** 13 Apr 2006, 04:25 am »

I have an extra PAT-4 I would be willing to part with. It works and sounds fine, but has a bad stop on the volume control. I was going to post it in the marketplace section but thought it would look silly amongst all those expensive gizmos, and all the people who cared were reading this thread anyway. Hope nobody minds. It is also posted on www.classicspeakerpages.net but nowhere else yet.

This unit is stock and a prime candidate for upgrades like the ones in Frank's 1986 Audio Basics article and I'm thinking $50 plus shipping. I'm more interested in passing this on to another Dynaco enthusiast than making money so I would be open to trade for accessories or?

prrtraincow · « **Reply #13 on:** 30 Nov 2006, 06:58 pm »

I just stumbled across this forum. Hello, everybody!

I have an old PAT-4 I built in the 1970s, and I still use it. Maybe it's not the greatest thing that ever lived, but I'm still perfectly happy with it. It makes no funny noises, and the pots and switches still work fine (no scratch, noise, failures, etc) except I did replace the volume pot, which had become scratchy, but what the heck, the thing is 30 years old!

I hunted down the 1986 Audio Basics article from Frank Van Alstine's website
at http://www.avahifi.com/root/audio_basics/index.htm. You can download the whole
1986 archive and search for "PAT-4" in the pdf file to find his upgrade article. It basically
amounts to replacing most of the ancient capacitors, and bypassing the tone controls.

I am going to go ahead and do it. I don't have the money to drop on a modern-era Van Alstine creation. Cringe if you must, but my old PAT-4, ST-80, and AR5 speakers still suit me just fine.
There is a faint whiff of hum when the phono input is selected and the volume is cranked up
past about halfway. It's not very noticeable, but maybe new power supply caps will get rid of it?

I already sent a direct email to the Van Alstine website on their "contact us" link, asking a series of questions about his choice of component values in this old mod. I'd like to know more about why he chose the values he did. Most of the signal-path caps get replaced not just by better caps, but by DIFFERENT VALUE caps.