PART TWO: Reliving the 1976 sound of Dynaco PAT-5 preamplifier and SWTPC power amplifier!

Gentle reader,

I have received the single Dynaco A-25 speaker I found on eBay for a bargain price. It turns out to be the "VW" model, although not marked as such, but does have the vinyl walnut veneer which is much darker in color than the older model's real walnut veneer looks like. It is in remarkable shape with only a slight flaw on the top left corner. So much smaller than I remember them being. But then again, they are "bookshelf" speakers.
Gretchen is checking it out. Behind it is one of my Cerwin-Vega! LS-12 speakers for size comparison. 
It even still had the small Dynaco badge. The glue that held it to the small screw had failed. But after carefully scraping off the old glue, I re-glued it with Super Glue. I always listen with the grilles off. Someone, perhaps the original owner added these picture hanger brackets. Putting speakers right on a wall or in a bookshelf produces poor sound quality. I plan to remove them.
I don't know if anyone can deduct something from the serial number. I can't.
I bought a pair of A-25 speakers from Dixie HiFi in Richmond, Virginia in 1976. They were demonstrator models and had a few nicks and scrapes. But at $99 for the pair, they were a bargain. I was still using them them well into this Century. One day, I noticed a buzz coming from one of them and pried off the grilles. THAT'S when I noticed that one had non-Seas drivers! Of course I'd had them for decades, which proved my ears are not "golden". I removed the offending drivers and tossed them and found they had stuffed the box with fiberglass as well. Since the cabinets were so beat up, I decided to sell the Seas drivers from the other genuine unit. This was around 2008, I think.
They certainly appear to be the same units as in the VW model, don't they? Moot point, OR as my ex-wife used to say, "The point is mute." I learned early on not to correct her. SO glad my spine finally fully developed and I divorced her. Second best decision of my life. Best one was asking Nancy to marry me. That was 21+ years ago. We are truly soul-mates and best friends. But I digress.
 
After testing the the PAT-5 and SWTPC 215/A here in this room with the two BOSE 301 speakers that Nancy bought new for me. The sound was brilliant! Especially highs, the 301s are quite impressive speakers if set up properly. As can be seen in this post from a few years ago:   
 
As you may recall, I scored a LUXMAN PD264 turntable via eBay. The problem I'm facing is where to put a second stereo's components. I researched folding wooden shelves and chose this one from Orolay:
Unlike most folding wooden shelves out there, these from Orolay are solid wood. NO particle board or MDF at all. This one is deep enough and more than wide enough to hold the turntable and allow it to have the cover open fully. It is very sturdy and perfectly level in all directions.
It comes in two pieces, the second being the upright portion seen above. It has two pieces of dowel poking out of it and there are corresponding holes in the section that fastens to the wall. That section and all the pieces are factory assembled. I elected to glue and clamp the vertical piece on to main unit. I wanted solidity. 
 
I located a wall stud and the center of it. Using the upper hole of the vertical piece, I marked the spot it would attach to and screwed it to the stud but not all the way in. Using a level atop the shelf, I marked the bottom hole the same way. I also marked the four holes of the horizontal piece. I removed the assembly from the wall and drilled the second hole as I had the first. Then I drilled larger holes for the expanding plugs that came with the shelf. Inserted them and hammered them flush. Once again, I installed the shelf assembly and tightened all six screws. NOTE: The screws that come with the shelf are not long enough to securely sink into a stud. I used ones that are about an inch longer. I highly recommend this method should you choose a similar shelf. At $30.00 they are a FRACTION of dedicated turntable shelves. I realized after mounting it, that I wanted to drop the AC and sound cables through the wood, rather than each going down one side. Sadly, I realized that there was no way to get the AC cord through without much more work. The audio cable went through fine, though.
 
I was then faced with where to put the PAT-5 and SWTPC 215/A where I could hook up the turntable and speakers and realized that I needed a small shelf or table below the turntable. However, with the Klipsch speaker there, there really wasn't room. I was not deterred.
 
So, I decided to remove the Panor-era Dynaco Stereo 200 amplifier and it's ancillary components from the system and to place the  PAT-5 and SWTPC 215/A in it's place. I left the PROTON 1100 preamplifier in place as eventually I would be using it again.
One thing about the PAT-5 I am concerned about is the somewhat flimsy pair of RCA terminal boards mounted inside the rear panel. Not only do they flex when pressing in cables, the terminals are so close together that modern quality interconnect cable's plugs are too wide to fit well. Although this classic PAT-5 does have enough inputs, I would have to use thinner cables. As you will see in a photo later on in the story.

Yes, that IS a Swiffer 360. It is great for cleaning LPs that are just dusty.
I added some rubber isolation feet under the PAT-5 and rubber and cork isolation pads under the 215/A amp. A small New England based audio and music company sells these for CRAZY prices! If you google or look on eBay for Air Conditioner isolation pads, they are SO cheap to buy. Companies count on the potential buyers being unaware of the web they weave to capture your money. I once had all the components mounted as such. Looked silly and I couldn't hear any difference. I have the cork/rubber pads under my subwoofer to give it a little more room since it is bottom firing. Plus, I have it on a board so that sound is not lost in the carpet.
These Liberty Cable Z-500 audio cables were causing drop outs so I replaced them with the thinner Z-500 video cables I was using to test it. I believe it is the PAT-5's terminals fighting the tight grip of these quality RCA interconnect plugs. Sounds were happier now. I used to use these Liberty Cables for the turntable as they are very low in capacitance. Once rearranging, however, I decided to use them from preamp-to-power amp.
While this portion of the photo above is blurry, you can see how tight the space is.
I was using an old Audio-Technica TR430E cartridge on my Denon Dp-23F turntable, I've tried numerous models of cartridge on it. My favorites were Shure's M97XE and Ortofon OM-40. The removable head makes it easy to try different ones. I'd bought a replacement stylus from Needle Doctor that was an upgraded unit. However, after a time, the sound was suffering. A close examination revealed a bent cantilever. I put the old A-T original stylus back on and the sound greatly improved. So much for "generic" stylus!
 
I wanted to try the Ortofon 2M Red that everyone is raving about. Got an "open box" unit from Music Direct for $89 and free shipping. I too am very impressed with the Red's sound! Yet, I wanted a better cartridge for the LUXMAN too. A search on eBay found a NOS genuine  Audio-Technica stylus for their ATX12E cartridge at a great price and another seller was selling just the AT12XE body for $19.99. I bought both and a new Denon cartridge head. Combined  all three and tried it on the Denon. Of course, I had to reset the stylus force. You can see all I have just told you in the two photos above. The sound is much better than the less expensive TR430E A-T cartridge. Anyone have experience with the Audio-Technica AT12XE cartridge?
 
BACK to the Dynaco A-25. Although BOSE does not publish specifications on their speakers, the 301s are very efficient. Very little amplifier power drives them to very loud levels. I hooked the A-25 to the left channel and placed it atop on of the LS-12 Cerwin-Vega speakers to get it closer in height to the right BOSE 301 which is up near the ceiling. The A-25 is much quieter than the BOSE, so I ran it in mono mode and listened for quite a while. To listen in stereo, I had to have the balance control at around the 9 o'clock position for a good mix. Nonetheless, I like the sound of the Dynaco A-25. They were highly praised by the experts and consumers at the time they were new in the late 1960's and early 1970's.
 
Yesterday, I did all the changes seen at the very top of this article, hooking the power amp directly to the Klipsch KG4 speakers with the commercial speaker cables. While I've been typing this, I played Telarc's SACD of the 1812 Overture (I bought it originally on LP, no cartridge I've tried could handle that 1st cannon shot) and kept the volume low. When I detected the first shots were about to happen I ran into the den and watched the meters on the power amp. I kept turning it up until I saw the needles edging into the red. Klipsch's handled them fine as did the little 215/A amp. Once that SACD was over, I switched to the two SACD set of the rock version of The War of the Worlds which I'd also originally bought on LP. If I set the volume control at the 9 o'clock position on the PAT-5, it is too loud to be in the room! And the meters aren't even approaching the 5% area! That is how efficient these Klipsch speakers are!
 
I am still going to get another Dynaco A-25 speaker, one as close to specs as the one I have now, or if not, then a matching pair and keep this one as a spare. There is no hurry as there is no room, right now!
 
Conclusions: The sound is amazing from these 40-year-old components, especially through the BOSE 301 and Klipsch  KG4 speakers. The one drawback of the PAT-5, and ONLY one is the aforementioned RCA terminals situation. Nothing I can do to the PAT-5 to fix that. Without investing in thinner RCA interconnect cables, I cannot use very many sources as there just isn't physical space to fit fat plugs.  The Southwest Technical Products Corporation 215/A 25 watts-per-channel power amplifier is more than adequate to meet my sonic and audible needs. I'm very pleased with the sound. Who knew? Would I like to get my hands on a pair of SWTPC Tigersaurus 200+ watts-per-channel power amplifiers? You bet! But with efficient speakers, this small 215/A is awesome.
 
I see so many of my fellow audio lovers in the various FaceBook groups that I belong to with huge stacks of components that they can't possibly be able to use all of them. Let alone the multiple stacks of speakers. Like miniature Grateful Dead "wall of sound" setups. If I had kept every component that I've bought over the decades, I wouldn't be able to walk into that room! I have striven to get better sound all these years, yet this exercise has shown that had I been able to, or been able to afford to pay someone else to, repair my original PAT-5 and two SWTPC Tiger 60 watt mono amplifiers, I would have had excellent sound all along! Oh, the irony. As it is, since I've retired, I no longer haunt thrift stores, yard sales and flea markets (it never occurred to me to visit estate sales) looking for LPs, CDs and stereo and A/V equipment and vintage cameras. As it is, since I've retired I've sold almost everything I can part with on eBay in order to afford to recreate my 1976 stereo. When I have a second A-25 speaker and have figured out how to have two systems (I once had a six-channel SACD dedicated second system in that room) in the same room, I will post another chapter in my blog. 
 
To see three iterations of that dedicated system, the various cables I have used, rubber isolation feet and more, feel free to look at the progress and eventual dissolution of that SACD system here:
 
By the way, this is my 199th post! Just the other day, page views passed 110,000! The jump from 50,000 to 100,000 took far less time than zero to 50,000 and from 100,000 to 110,000 only took a matter of a few days! I have YOU to thank for that! Don't get me wrong, I am not spending so much time creating these posts for numbers. No sir, this is my passion, one of many that I choose to share with you. I am always grateful for your kind comments, either here or on FaceBook.
 
Thanks for looking! 
 
Scott
 
August 18, 2017 

  

Reliving the 1976 sound of Dynaco PAT-5 preamplifier and SWTPC power amplifier!

Gentle reader,

Thanks to the world's largest flea market, otherwise known as eBay, I have been gathering vintage stereo components to recreate my very first stereo I built from kits in 1976 when I was 19-20 years old.

I had bought 32 year old Klipsch KG-4 speakers at a thrift shop and seeing all this vintage equipment people are enjoying in the various FaceBook groups I belong to, AND seeing all the awesome vintage equipment at HiFi Heaven in northern Virginia, I really wanted to experience that "vintage sound".

I first wrote about it here:
BACK to: My First Stereo 1976 Dynaco PAT-5 SWTPC Tiger 01  and also showed photos of various Dynaco equipment I have owned since having a digital camera, here:

The original Dynaco PAT-5 preamplifier that I built as a kit was a bit newer than the one you are about to see. The faceplate was not gold-hued like so much Dynaco equipment of yore. And the PAIR of Southwest Technical Products Corporation 60 watt mono amplifiers I built after completing the PAT-5 are long gone. They stopped working and eventually I gave them to a coworker. 

I have bought, enjoyed and passed on to others countless pieces of stereo equipment over the decades since 1976. Not buying my first CD player, a used early model one, until 1996. I bought it only because I could not find a certain Jazz album on cassette. But I digress.

So, I have these Klipsch speakers from 1985 and a LUXMAN turntable from I don't know when and really no where to put them all together! Oh, and I am also acquiring a pair of my very first speakers too: Dynaco A-25s. I just bought one via eBay for a great price and will eventually find a mate for it.
So, here we have my latest PAT-5. Got it for $99 via eBay. Was told it works and it does. Aside it is NOT a SWTPC 207 Tiger .01 60 watt mono power amplifier, but a later model called 215. It uses a smaller (lighter) transformer and smaller less powerful power transistors all enclosed in what normally houses just one Tiger mono amp. It puts out 25 watts per channel and uses the same circuitry as it's big brother seen below in a scan from the original instructions:
 
Below is the same company information sheet for the smaller, yet stereo amplifier:
 I have periodically looked for SWTPC equipment on eBay but they were always listed as not working. To my delight, I saw the 215 listed as working at $60 or best offer. So, I offered $50 and the seller accepted it! 

Here is a photo of my original PAT-5 that I sold once one channel stopped working. See the differences in the faceplate?



Someone in the past replaced the power switch with a light, above.
Seeing the insides of this PAT-5 brought it all back to me all the work it took to complete it.
I came across this photo I made some years ago of the inside of a modified PAT-5. It was NOT a Van Alstine mod, but the eBay buyers recognized the name of the man who did the work.
Quite a number of changes now that I have a stock unit to compare it too!

The seller of the 215 power amp showed photos of the inside and they were accurate! Here are my photos once I got the cover off.




It's a very strange dust, the color and texture. Below are the "after" photos:





As you can see, although the dust is gone, corrosion and even rust on a steel piece that runs between the circuit boards, abounds. I cleaned metal bits with Dylek contact cleaner and DeToxit too. I found one wire had broken off and located where it attached to one of the big capacitors. Other than that, it all seems whole.
Below is a photo of a Tiger amp's rear panel. The heatsink shown above is used throughout the entire SWTPC audio line, even the amazing TIGERSAURUS 200 watt mono amps. The Tiger uses two sandwiched with T03 type transistors.
Above photo was found via a Google image search. I could not find any photos of the inside of a Tiger to show you.
Quite a bit different, aren't they? All the fuses are inside the 215. Note the normal RCA inputs, but 1/4" mono plugs for the speaker cables. I had to buy a pair of professional speaker cables which had the 1/4" plugs on one end and dual banana plugs on the other end via eBay:
As I discovered some time ago, the standard 3/4" spacing for banana plugs as seen on the PAT-5 and many speakers isn't followed anymore. So, I replaced those that came with these Seismic Audio cables with the ones seen above.

Another Google image search netted me these fine images of the inside of a very pristine 215 power amplifier.  Yet despite the age, this thing is working perfectly!
Note the board atop the big capacitors is vertical as were the ones in my Tigers.
I suspect this amplifier was factory wired, where the one I have clearly was not! Yet, after forty-some years, it and the PAT-5 are still rocking away!
Yes! Even the meters still work!


I've only played CDs so far via the SONY WALKMAN portable player.

First Dynaco A-25 speaker has arrived. Amazing condition. It is the "VW" model which means vinyl instead of real walnut veneers. Am now searching for a matching one. I always play my music with the grilles off.
  
I came across the idea of wall mounting a shelf to hold the Luxman turntable. There are many available ( for a fraction of the cost of a "real" shelf to hold a turntable!) but I wanted one made of real wood, not particle board. Bot this via Amazon. Very well made. Now, where to put it!

Stay tuned for an update once it is all located and when I have two A-25 Dynaco speakers too!

Thanks for looking!

Scott

The 500th Article Of The Robb Collections! Thanks To All Of You! Indexes To All Categories!

  October 24, 2024 #500 Gentle reader, First of all, THANK YOU for taking the time to read my writing and viewing my images! This article, s...