Dynaco A50 - help and information needed

[clogsmith]

Hello all,

I just procured a set of Dynaco A50s, they were less than ideal but I have been looking for a while now and these were what worked out to get so far. I hooked them up to two different amps and have been having problems with them.

What I know from previous owner: Both tweeters were replaced with ones from a set of A25s. (I know that the A25 tweeters were not the same ones on the A50, but I have read that the tweeters from the A35s should be the same.) One woofer was replaced at some point.

The problem I am having with the speakers is that when they are hooked up and played, they are significantly quieter than any other speaker that I connect to the same amp. (I tried them with a 55 watt MCS receiver as well as a 100 watt Fisher CA amp, the fisher rocks a pair of Yamaha NS-9393 to ear splitting levels no problem.) This surprised me because a 55 watt amp plays my set of A25s louder than I would want them. The other problem is that one of the speakers plays noticeably louder than the other. They also produce a very small amount of muffled bass, and turning up the bass on the amplifier just turns the sound all mushy. I don't know if it was the one that was replaced, but one woofer appears to have slight coil rub when lightly pressing on it evenly. At this point I am feeling that there has to be something seriously wrong with this pair of speakers, I always loved the A25 and have lusted after the A50s since I got my first pair of A25s, but have found nothing but disappointment. Does this sound like a crossover problem that needs to be recapped? Could the wrong tweeters be throwing everything off? Any ideas or suggestions are welcome.

Thanks.

 

[avguytx]

Make sure those contacts are clean on the tweeter attenuation knob...if they have them like the A25's. Those contacts can get nasty. Also, do they have the stock electrolytic capacitors in them? If so, spend the little amount of money to put something better in them like Dayton poly caps or Solen caps at minimum. That alone opened mine up more than anything. Also, if they do have the tweeter level controls on them, there have been cases where those resistors were shot and can be either changed to new resistors or bypassed altogether. Resistors are cheap, too.

it could always be drivers going south....they are quite old, you know.

 

[wlhd1610]

I have two pairs of A 50s.
They use two 16 ohm woofers instead of the 8 ohm that's used in all the other Dynaco single 10" woofer speakers.

Bob

 

[gdmoore28]

Go at this methodically. It sounds like there may be more than one problem to deal with, and a logical approach will help you find them. As Avguytx noted, you can almost be sure that if the caps and resistors haven't been replaced, they should be. Easy and cheap.

While the caps and resistors are on order, remove the woofers and tweets from the cabs and give each a good inspection. Check the woofs for proper movement and vc problems. Check the woofs' and tweets' resistance with a digital multi meter.

Grab the A50 wiring diagram and make sure that whoever has been inside them in the past didn't screw up the wiring order. Very important. There's no telling who's been inside or what they did to them.

Once armed with the results of this, come back and tell us what you found. We'll go from there.

GeeDeeEmm

 

[clogsmith]

Thank you all for the information so far, would any of you know where I can find the specs of what caps and resistors to order for this project? Or do I just need to take it apart and read the ones that are in there now? I have never done a recap before, but am comfortable with soldering, but don't feel confident in identifying and ordering the new parts.

Also, gdmoore28, where might I find a good wiring diagram for the A50?

Thank you all for you your time.

 

[gdmoore28]

I cannot find a wiring diagram for the A50. Unless one of the members here have one, you will need to read the numbers on the caps (might be only one) and the resistors. If you have questions, just post the images here. Make sure the numbers are readable.

If I were guessing, I would bet that the A50 uses the same wiring diagram as the A25, but with two 16 ohm woofers in parallel to yield an 8 ohm load.

We need some A50 owners to give us some info. I'm working in the dark and trying to give general info as best I can under the circumstances.

GeeDeeEmm

 

[sinewaver]

For what it's worth, I'm not there to hear what you're hearing but your description leads me to believe you have a phasing problem. From their past, it's very possible. I'd bet they haven't worked well since the last tinkerer was in there. I don't have the diagram in front of me but it's a simple affair. The one driver that has some rub might be addressed by remounting it in another position as sag may have happened. Rotate it and see if that cures it. Do the battery thing and make sure both cones move in the same direction. Should only be one cap in there. You'll get it, but undo it yourself projects are a PITA. I've wanted a pair of 50's for years, don't know where I'd put them, kinda' large. Keep us posted.

 

[Pete B]

There is a schematic here but with an error in the tweeter section that I point out:
http://www.classicspeakerpages.net/...d-xo-schematic-newbie-to-classicspeakerpages/

 

[gdmoore28]

Clogsmith,

Thanks to Pete's post, you now have nearly all the info you need to bring your A50s up to snuff. Good on you, Pete!

Now you need to pull each speaker and check it's condition to make sure you are starting out with functioning drivers.

Keep us informed of your progress, and we're here to help in any way we can.

Oh, and a belated welcome to AudioKarma!

GeeDeeEmm

 

[clogsmith]

Hey, thank you Pete! And thank you to you all! Unfortunately family health has gotten in the way of this project, but it is at the top of my list to work on when I can. If there is any hope for these I would love to be able to enjoy them. My garage work space is in desperate need of some Dynaco. I definitely plan to return with updates, and appreciate the good info and warm welcome.

 

[clogsmith]

Are we allowed to post links to big online auction sites? There is an auction for a Dynaco speaker from Canada for a fair price labeled "1- Dynaco driver .. SEAS H336 tested" but I cannot determine if it is the 8 ohm model or the 16 ohm. Been thinking having at least one spare on hand would not be a bad idea...especially since I know one woofer is already rubbing, although I haven't tried turning it yet. Will have to do that when I dig in to these.

Nvm Disregard. A closer look showed a smudged red 8 ohm printed on the magnet.