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Dynaco Photo Gallery 1


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Hi there;

We often talk about something and there is no photo for reference.

Here is the start of the Dynaco Photo Reference Series.

I have posted some of Dynaco's classic equipment.

More to follow if there is an interest.

Note the very rare mirror image pair of Dynaco A-25's.

There is one more photo but the limit here appears to be 10 photos.

I'll post it next time rather than just for one photo.











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Hi Vern nice pictures,


The A-25s that I have are also mirror image, and I know that this was not the norm. They look as if their from different production runs, or was it planned that way with them sold as pairs. Do you know any more about the mirror imaged pairs?


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Guest matty g


Brilliant! I, for one, think the Dynaco photo gallery is a great idea. When I get ahold of a camera I'll have a few things to post, too. I only wish I hadn't chucked my old Scan Speak A-25 with the vent under the tweeter. The magnet on the tweeter was huge - much larger than the Seas magnet. It was pretty much the same diameter as the outside circumference of the driver. It was part of my first "HI-FI" system when I was a kid. An Allied tube amp, Garrard turnatable, a Wollensak reel to reel (also tube) and that A-25. Crude as it may have been, it sounded great. Who needed stereo!

Can you fill me in on the connection between a Danish speaker company and Dynaco of Philadelphia? I never quite understood that. Which came first?

BTW - what is the first picture of? Looks like a radio receiver?

Dynaco electronics show up all over the place. I once had a B&O open reel tape machine with Dynaco amps in it. Also once had a Sonab (of Sweden) amp/receiver unit with Dynaco built circuits in it. Leads me to believe they are a Scandinavian based electronics firm?


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Good idea. Can add some stuff later. Matt's observation made me realize that not everyone can identify the various pieces. Maybe if multiple pieces are posted, include a list organized by attachment number of what models and pieces they are if the photos are not imbedded in the post.

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Hi Matt and James;

Thank you for the feedback.

This was my first try.

There is a limit of 10 photos plus a write-up.

I am not sure which way to go next time.

Perhaps just to try it out, I may just add to this Gallery 1 topic and see how it appears on the main menu.

By adding a new topic to the Dynaco site the order would get lost again.

The original name gets lost upon it being accepted on this site as a number.

That dark box is the Dynaco Quadapter Mark 2 which was a later version of the successful original.

I can see now that a brief, one or two line description, was needed for each photo.

Someone else may know the complete Dynaco/Scan/Seas story, I only know bits and pieces of it.

? may offer some insight as well.

Greg Dunn's Dynaco site has a very informative layout, well worth the visit.

Briefly, Dynaco either approached or was approached by Scan or Seas perhaps about the A-25 prototype.

It was a 4 ohms system, but was spec'd at 8 ohms by a Dynaco engineer.

Scan versions appeared to be the first out the gate with the vent above the tweeter.

It used the Scan tweeter and woofer.

At some point early in production the Seas version was produced, Seas tweeter and woofer.

There was not information as to how, why or when this transformation happened.

I worked at the local Dyanco warantee depot here and I saw a Scan version in a store, the warantee depot had no notice.

As warantee repairs started rolling in, the replacement woofers were only ever the Seas woofers with the horns.

Those woofer replacements required a chiseling of the cabinet to allow the horns to rest on the recessed lip.

Before Dynaco bought the speakers form Denmark there was something like hundreds made a week I believe, I wrote previously about this number.

One semi-trailer load a week went through the Dyanco factory, with sales over one million total for the A-25's alone.

The Scan versions are less seen for sale used, as is their drivers.

More later.

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Hello, Vern. I've been looking in for the last couple of months and I can finally make a contribution. Here a couple of photos of my

A-50. The 1884.jpg is as it is in the bookcase (right speaker) and the 1885.jpg is with the grill removed. Now to get to why it does not look like an A-50, at least with the grill in place.

Several months ago I spotted a Craig's List offer of two A-50s. I went to look at them. The condition of the cabinets was terrible. Not much in the way of dings or scratches but the wood was completely bleached out. Pulling the grills showed the woofers to be OK. The price was OK, so I took them home (acceptibility subject to a listening at home).

I took a gamble that some Danish stain would make them look good again. I was right. The first coat got soaked right in, the second coat brought out the color, and I topped it with another coat. The grill material was in quite good shape, very dusty but OK. However, I knew it would not pass the wife-acceptance test and I promised her I would do something about it.

I (we) settled on using caning material that would match the cane used on a hutch and six chairs at the other end of the room. I put as much money into the caning material and the 3M products used for the gluing (a very messy job) but the results are worth it. The material is acoustically transparent and will withstand poking children's fingers which the original material will not.

Besides, they sound great (listening as I type this).

John Jensen

San Mateo, CA



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Hi John;

Excellent photos, thank you.

When I tripped over my pair of A-50's I didn't recognize the cabinets or grille cloths.

Cabinets were painted an aweful black and the cloth was dirtier than the floor they were standing on.

If the Dynaco logos were not present, I wouldn't have looked any closer.

For $100.00 I couldn't help myself but to carry them home, sound familiar. lol

When I close my eyes, so as not to look at them, I cannot do anything but enjoy the music coming from them.

A very authoritive speaker system.

The cloth is not restorable to any resemblance of when new but I may approach the paint and strip it down to, I'm hoping, walnut veneer, at some future date.

I locally picked up a pair of spare woofers (16 ohm) last year, off ebay, not that I plan on overdriving them.

I would recommend that you fuse your speaker system.

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>Dan, how much was the ebay price for the two woofers (just



>I've read your comments re fusing. I've got 60W/channel

>Williamsons. What fuse value would you recommend?



Hi John;

As with anything else on ebay the prices go up and down like a yo-yo.

The raw woofers are usually rare, after a seller trys to sell the complete speaker system first.

The shipping usually kills the sale.

Disregard your amplifier output, it is the speaker that requires the fusing protection.

I could not find a recommended fuse size for the Dynaco A-50 at this time, it may be 1 1/2 or 2 amp.

Dynaco recommended fast blow 1 amp for the A-25 speaker systems, slow blow FNM/FLM type was never mentioned, not that by trial and error a suitable size could not be found.

This would be a good starting point for moderate sound levels, fuses are cheap, at least the fast blow ones.

This would be the open style fuse holder as well.

The FNM/FLM style are expensive and difficult to obtain.

Possibly a slow blow fuse, similar to the AR-2 series speaker fuse size of 8/10 amp might be a safe start if going the slow blow route.

Go to, the OTHER Forum and read the fast blow fuse topic completely to better aid you.

I copied the best visual aid we have here from James, the draftingmonkey.

It is the slow blow fuse and holder but the details are the same.


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Hi John;

As the photo from James, the draftingmonkey shows, no allowance was made for any special connectors that may be factory installed, such as banana plugs.

Using fast blow fuses at a value of maybe $.25 cents each is certainly less painful to replace than an accident happening and a woofer or two burning out or tweeter as well.

There is no guarantee with a fuse, if oversized, in the case of the A-50, I would suggest a 1 amp fast blow for starters with an open style fuseholder.

Buy some spares.

A chassis style fuseholder is not the preferred type, as the heat is not allowed to vent itself with the cap seal.

Until such time that the recommended fuse size from Dynaco is found, I would stray not far above 1 amp.

Upward experimentation will determine the limit of the fuse size, music and your amp, not until something burns will you know that you went to far, too late.

Even when the correct rated fuse size is found, it is still in our best interest to keep to a lower rated fuse than was recommended 25 plus years ago.

I am sure that somewhere there was a review where a large amount of power was used in a listening test, for the A-50's, I have not read anything that comes to mind in this regard.

That would have been with them un-fused as well.

As a side note, in the AR library, under fusing, there is a brochure for fusing and the, "Lil' MightyMite", AR-7 was referrenced as passing well over 1,000 watts, briefly, with it's small rated slow blow fuse.

All of the AR fusing information is well worth keeping a copy of for future reading and reference even though some sheets have different figures printed.

The fast blow fuse is the 1/4" x 1 1/4" standard whether it be Littlefuse or Bussmann.

Another issue is whether to install the fuseholder at the amp or speaker.

If your amp has externally accessible speaker fuseholders then you have no issues at all.

I mention this only as an after thought, pinching of the cables between the amp and the speakers, under the carpet for example.

Another issue which we haven't even tackled for any of the brands on this site is, individual driver fusing.

This is far too complex for most readers to attempt, at least at this time.

If you have more questions, please post them.

In one of my previous write-ups I mentioned that ? would also probably come to add to Dynaco's history.

I had my brain on hold then and I forgot to put his name in, it was Klaus that has helped me with some information, sorry Klaus.

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Hi again;

I seem to remember reading a comment years ago about 500 - 600 watts being used in a review and how robust the speaker system was.

I really don't know where I either dreamed up or read this one.

Earlier in this topic there is a artists speaker enclosure cutaway view of the A-50.

The partition is drawn at a fixed position inside the enclosure.

I have seen another artists drawing with that partition at a much different angle, I do not know which was correct in production.

The partition has a rectangular hole cut through it, my guess at 1" x 5" with a cloth felt material covering it, at least on the one side I do remember seeing.

There may or may not be this felt on the other side and there may or may not be fibreglass in that separate section, I don't remember exploring that enclosure any further.

I have never opended the pair I own either.

This was about 1970 so I made a drawing, as best as I can remember, of the A-25, A-35 and the A-50 internal enclosure dimensions.

As a side note the A-25's were highly discounted a few months after they arrived here in Vancouver, being mainly available from only 2 stores, part of a chain.

They were down to $52.00 each, with only 2 pair available on door opening, my bros told me this.

With the heavy discounts, other stores would have been foolish even trying to sell them at such a loss.

Working here at the local Dynaco warantee depot, I did see that they did sell kazillions of them, a very high percentage of these required replacement woofers.

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>Good idea. Can add some stuff later. Matt's observation made

>me realize that not everyone can identify the various pieces.

>Maybe if multiple pieces are posted, include a list organized

>by attachment number of what models and pieces they are if the

>photos are not imbedded in the post.


Hi James;

I never took any of these photos myself, by the way.

One of the problems I ran into early on, is, the file name becomes a number when uploaded here.

Most photos I save have self explanitory appropriately descriptive names.

I will, next time, make a brief note as to what is pictured.

I will also sort the files on my hard drive before uploading to keep the items matching.

Thank you for your input, I appreciate that very much.

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>Hi there;


>We often talk about something and there is no photo for


>Here is the start of the Dynaco Photo Reference Series.

>I have posted some of Dynaco's classic equipment.

>Note the very rare mirror image pair of Dynaco A-25's.

>There is one more photo but the limit here appears to be 10


>I'll post it next time rather than just for one photo.

This is to assist those with my first posting on this topic.

Attachment #1 is the Dynaco 410 basic stereo amplifier, simply put, a Dynaco 400 stripped down to the bone basics, reputedly sounding slightly better than the 400, beats me.

A Dynaco 400 minus Dynaguard, power switch, fancy front, a humungous heatsink assembly, and several other features, to keep the cost down.

The 410 even included a temperature controlled fan stock as well, which helped keep the heat sink requirements down.

#3 is the rear of a Dynaco speaker focused on the speaker connections and 5 position switch.

The numbers are product ID - year - week, of manufacture and then the 4 digit serial number.

19B247660 is product number 19, year '72 because of the 2, 47 is the week, last 4 digits is serial number.

In this case it is the A-25 speaker.

I will NOT post the Dynaco product list for reference in the future.

This was quoted from Gregdunn's website and you can go there and see and copy it yourself.

#4 is one artists concept of the A-50 with different internal partition location than another I have seen.

One is straight across and the other is diagonal.

I will post the other artist's drawing if I can find it in the future.

#6 is one view of the Dynaco Quadaptor Mark ll sold much later in Dynaco's history.

Note there is substantial differences between the original and series ll.

I own one but I have been unable to get hold of an owners manual so far.

#7 this is another view of the Quadaptor Mark ll.

#8 this is one of several mirror images A-25 speakers that I have seen photos of, but do not know why there was no publicity or reports on them at the time.

#9 a view of the original Dynaco Quadaptor for 4 dimensional sound.

With this box and just 4 appropriate impedance matched speakers, not only 8 ohms rated either, only one stereo amplifier was required for the 4 dimensional sound enhancement.

I own at least one, which I will write about another time, about a modification, no gutting or butchering of any kind, to make the unit a more friendly cable ready and safe enclosure.

#10 same item different view.

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Does anyone know if these "red front" SEAS Dynacos came before or after the regular "black front" SEAS A-25s that I had in high school? I notice that the red ones tend to have silver screws, rather than black, and that the drivers tend to look really clean. This leads me to think these were later (1973-1974?) A-25s, but I really don't know. I also notice that the material quality of both the early Scanspeak screens and red front screens tends to be high; they fray less when I soak them and tend to re-attach more easily.

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Hi there;

Those photos were taken off ebay, I'll see if there was a date mentioned in that auction.

I just checked ebay and my files and there is no more photos for the serial number, etc.

My habit is to usually save a photo of the speaker terminal area as well when I save any.

If figure #3 is the rear of that same cabinet, I am not certain that it is, then 1972, week 47.

Back again;

I just had a quick look at those fig #3 speakers again.

Each of the plastic vents has shiny but different staples.

The right side appears to be the typical staple style but the left one appears to be shiny pins.

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Hi again;

Here is a set of Scan woofer and tweeter for an A-25 or A-35 speaker system.

Note the nuts and bolts protruding from the magnets, which the Seas drivers do not have.

The woofer also has a round perimeter rather than the horns at each screw point on the Seas frame.

If you were to replace one of these woofers with a horned Seas woofer, you would need to chisel a small piece of cabinet wood allowing for the horn to sit in the woofers routed recess.

This is not a big job but is necessary for the woofer to fully seat in the recess for a proper cabinet seal.

To replace a horned woofer with a round one would require no alteration to the woodwork.

I went and copied that reddish front Seas version A-25 here so that the screw horns can be seen clearly.






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Hi there;

Just when you would think everything is worked out, this happens.

I would have bet money that only the Scan A-25 had the vent over tweeter position, then this auction comes along to disprove that.

This unit houses Seas drivers.

The seller states that the other unit for sale has the vent below the woofer, typical of what we have come to see.

This cabinet has the reddish coloured front panel and different shiny staples fastening the plastic vent to the cabinet.

Too bad the terminal connection of both wasn't photographed to see if there was labels.

There is all of the screws in the tweeter holes, which is not normal and these are shiny heads, not black.

Same as the woofer, shiny screw heads.

The fit and finish of the vent and insulation is less than businesslike, compared to the Denmark made speakers.

I'm feeling that this was a USA made speaker.


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Dan, I just acquired several audio reviews about the A-50. This one is from High Fidelity, May 1971.

Describing it, they say "...A-50 is housed in a completely sealed walnut enclosure. I employs twin 10-inch woofers mounted in one chamber that vents internally (via an acoustic impedance system) into a second chamber." This is information we already know. Later in the paragraph it reads that "..it will produce a level of 94 dB (at 1 meter on axis) when powered by as few as 3.5 watts, yet is robust enough to take continuous input power of up to 100 watts without distorting or buzzing. In fact, the A-50 can handle an instantaneous pulse of 250 watts average power (500 watts peak) without distorting." I wonder where that came from, their testing or info from Dynaco?

What was also interesting is the picture of the unit showing the grill off. Typically we see it with the two woofers at angle to the rectanular shape, one being in a corner, the other angled away from it. Well, the picture shows the two woofers centered equidistant from the edge. The speaker box looks like an owl looking at you with a third eye in the center of its forehead (that's the tweeter). Perhaps the manufacturer was experimenting with layout before finally settling down with the design as we know it.


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Hi John;

Thank you for the feedback.

I've seen several artist's conceptional drawings that showed at least 2 different mounting methods as you have described.

Also the internal board divider at 2 different mounting angles as well.

There was only one Stereo 400 amp announced but there was about 5 different versions not including fan and meter variations.

Sad you can't post the photos.

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Hi again;

Here is a few A-50 photos.

The photo with the grille cloth on has a light streak at 45 degree angle on the lower section, this is a wooden strip to support the grille cloth.

I suspect if the grille cloth was off these units, they would have the drivers on the same angle as photo 3, rather than, "Owl like".

I did not take these photos.

The third photo was from another thread.

The 4 th one is a sketch, one of the several variations, un-documented about the partition and driver locations.

Note the tweeter is also below the woofers.





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