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Dynaco A-35 crossover question

vinylviola

Well-Known Member
Hi all -

I'm about to go elbow-deep in a fairly beautiful pair of A-35's and I just want to verify with someone more experienced that the crossover inside these Danish beauties is the same as the A-25.

Can I get a chorus of 'amens' before I order the wrong bits off of PE and have myself a very expensive fireworks display all over my landlord's cheap carpet?

Attached is a schematic from t-linespeakers that claims accordingly.
 

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Okay, I've run into an issue.

While ever schematic I've seen online claims that the A25/A35 crossover is identical, I just pulled an 8uf 50v cap out of one of the speakers, not the 5uf 250v that I have in hand.

I'm not an electrical engineer so I don't know what everything means/does... do I turn off the solder iron and re-order?
 
I think the tweeter is the H086, not the H087. This then would be the tweeter from the A25XL, not the A25. If the level control on the rear is a 3 position, rather then a 5 position, this will confirm the H086 as the tweeter otherwise you can just look at the tweeter label.

Not sure if Dynaco built an A35XL, but it sure sounds like it.....

If that is the case, it is a 12db per octave slope rather then the A25's 6db per octave slope so there is also a coil across the tweeter's + and -. The cap is an 8mfd cap, the coil will be .5mh.

Wayner
 
I think the tweeter is the H086, not the H087. This then would be the tweeter from the A25XL, not the A25. If the level control on the rear is a 3 position, rather then a 5 position, this will confirm the H086 as the tweeter otherwise you can just look at the tweeter label.

Not sure if Dynaco built an A35XL, but it sure sounds like it.....

If that is the case, it is a 12db per octave slope rather then the A25's 6db per octave slope so there is also a coil across the tweeter's + and -. The cap is an 8mfd cap, the coil will be .5mh.

Wayner
So vinyl, is there a coil in there?
 
unnamed-2.jpg
There is a 5-position switch on the back of the cabinet and I found no coil inside.
I ordered 8uf caps from PE so we wait for those to arrive...

This is what I found inside:
 
After reading more online, there seems to be a 50/50 split between those that say the A35 crossover shared the same crossover as the A25 or not.

Those that disagreed, however, DO say there should be an 8uf cap instead of a 5uf, which is consistent with what I found inside these speakers.
 
No. Most A25 speakers used the SEAS H087 driver which used the 5uf cap. I do not know what driver is used with a bare 8uf driver. Perhaps you could take one out and tell us. It might be a SCAN-SPEAK.
 
After reading more online, there seems to be a 50/50 split between those that say the A35 crossover shared the same crossover as the A25 or not.

Those that disagreed, however, DO say there should be an 8uf cap instead of a 5uf, which is consistent with what I found inside these speakers.

There were some with larger cap. Some folks claim it was a later model or tried to add the "XL" designation to the later offerings,what the truth was as follows:

Way back in the ages in a sonic period before the rantings of modern VFETs announcements from Sony the speakers companies actually did listening tests on their various products and Dynaco had to buy components parts from various suppliers. Well a certain load of tweeters came in and through their testing efforts they noticed the high end seemed a little off.

To me a set of these on some HK Citation or a Dynaco 70 or if you had the wallet a set up of a pair of MKIV amps were just bliss with a set of these aligned and set up. The early SAE products were also one of the magical matches with a good TT and Tuner.

So the old kindly engineer tried adding to the original cap and found at the magic 8uF number the originalsonic qualities were being reproduced and due to the fact Dynaco had so many of these tweeters and could not return them to the manufacturer (buying specific items tends to limit returns in some contractual purchase agreements) they decided to instead use them as opposed to reordering a new batch and hold off on deliveries using the higher value caps.

(We experiemented with a few diifferent caps and got some decent results with some 12uF caps but most didn't agree although the measurements via listeners in one of the rooms never said they sounded off and yes I know what should have been the result, just reporting what were found out. To me it sounded more pronounced and not as sweet or full but more toward the boom boom hiss hiss as opposed the the full range sound these boxes were known for.
The best SS receivers that match up were the Sansui mid to upper line as they just sounded the best out of all the majors. I think it was the smoothness ofthe way Sansui handed their power supplies as they never got to the point of straining (when running at 1/2 power or more) like some of the other brands did with more demanding pieces of music.

The Marantz separates also did a good job but the receivers were not as good as the Sansui line to the concensous of listeners. We ran the boxes for month in a comparison test and out of 200 completed surveys the majority picked receiver B out of the five majors, Kenwood, Pioneer, Marantz, Sony and Sansui. If asked people would generally pick "B"and claim that the Marantz or in many cases the Pioneer sounded best as they knew their receivers, even though it was a 771(32 WPC) Sansui verses a 40-50's WPC (2245 45 WPC) Marantz or (SX-838 52 WPC) Pioneer unit they thought was playing.

Now, whether that is absolutely true or not (about the reason for the cap changes) that is what the head of the sales department told us when we had to repair some boxes and discovered the same issue at the store. If you change the value of the cap you will notice a difference and you may like it or not but someone familiar with the true sound from an untouched A35 will notice it straight away as the high end is not as smooth and a bit brighter to the ear. The richer mid/high end leans much more pointedly than the earlier models.

So perhaps they should have changed the model but just kept the same designation. We had some customers who wanted their boxes to match their existing systems and complained until we replaced their "new tweeters" and caps to match the older circuitry. One of the other stores had some left over replacement tweeters newin box andwedid a few pairs for the purists if you will. In reality matched up and broken in they sounded the same and unless you could look at the guts in the box you wouldn't really know the difference in sound.

All measurements were basically the same with of course the difference being broken or burned in or fresh out of the boxes and still a bit stiff.

Hope that helps

Cheers
Hermit
 
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Here are the woofer/tweeter:

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As always, thanks for all the help and knowledge!
 
Either way, you could've ordered a 2.2uf cap to run in parallel with the 5uf cap. That would've been 8.2uf total, with the "supposed" musical benefit of having multiple caps with various cap frequencies for the signal to go through (it was a fad, especially during the 80's.)

As long as it adds up to 8uf, which 7.2uf is close enough in this case, you'd have been fine. Some may suggest to hit 8uf exactly, but I'd bet these tweeters would benefit from the slight shift to 7.2uf.
 
8uf caps arrived from PE today.
Tomorrow I should have time to get them in and start their burn-in before I A/B them with my A25's.
 
Cap installation complete! I already had the cabs open, so waiting for the iron to heat up took longer than soldering them in.

I've got them hooked up and I'll let them burn in for a few days before I pull the A-25's out for direct comparison, but the 35's already got a B12 shot to my ear. They felt dull and flat before and now I'm hearing so much more of the sparkle and magic that I'm used to hearing with my A-25's.

Whether there's any "sonic improvement or "refined bass response" is yet to be seen. Stay tuned...
 
A/B listening starts today!

Out of morbid curiosity I opened the A-25's before being hooked up JUST TO BE SURE they had updated caps (as the seller promised) and lo and behold, there were Jensen caps glued to the crossover board, so I took the opportunity to swap them out with these spare Daytons I had on hand. I'm not sure if the Jensens were, in fact, originals, but I decided not to risk it. I'll allow a few days' settling in on these A25's now before I seriously offer any comparison.

 
I did a similar thing that you have done, I had both 25's and 35's and recapped both. I ended up keeping the 25's and selling the 35's. To my ears the 25's sounded much better, but might be different for you.
 
A/B listening starts today!

Out of morbid curiosity I opened the A-25's before being hooked up JUST TO BE SURE they had updated caps (as the seller promised) and lo and behold, there were Jensen caps glued to the crossover board, so I took the opportunity to swap them out with these spare Daytons I had on hand. I'm not sure if the Jensens were, in fact, originals, but I decided not to risk it. I'll allow a few days' settling in on these A25's now before I seriously offer any comparison.


DAMN! I got to the end of this (oldish) thread and now I want to know how it turned out! Who won the shootout?
 
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