[rcag_ils]

http://cgi.ebay.com/Dynakit-Dynaco-Stereo-70-Tube-Amplifier-and-preamp-/230593877459?pt=Vintage_Electronics_R2&hash=item35b07755d3

I should have posted this on the Dynaco board, but thinking that there are more Dynaco experts here. Can anyone tell me if this will blow up like a powerful bomb once someone flips the switch to on? I have never seen any Dyna 70 in this configuration.

[AVnerdguy]

YES! Yes, it's going to go off like a nuclear device! Sorry, had to do that. 

It appears someone made a very large power supply & pre amp combo. At least that's what it appears to be. There are obviously RCA inputs on the side of the mystery box but since they didn't show that side I can't tell if there is any volume control (or anything else for that matter). They have to be mated together via the socket/pin arrangement so it will definitely take up some room. Also, those caps on the 70 look very old (original) and most likely need attention. In addition, the AC cord to the amp is pulling out of the strain relief - use caution there as well as it appears to be round which means it's most likely a 3 conductor - the amp originally used a simple 2 pronger. Mullard tubes though (again might be original) could be good or could be junk.

[rcag_ils]

There are also diode rectifiers in use, and who knows what the owner plugged into the 5AR4 socket.

[AVnerdguy]

Indeed. I'm usually adventurous and love to fix/mod these but this one scares me!

[avahifi]

This one would scare me too.  At least it is not being advertised as being an AVA unit. 

Regards,

Frank Van Alstine

[avahifi]

This one would scare me too.  At least it is not being advertised as being an AVA unit. 

Regards,

Frank Van Alstine

[rlee8394]

7 bids on it though. My guess is that it is wanted for the iron and Mullards.

[rcag_ils]

7 bids on it though. My guess is that it is wanted for the iron and Mullards.

Here's my analysis, judging by the dust, corrosion and the kind of caps used on the extra power supply, it looks to be it was built a long time ago, might not have been as old as the amp, but old, chances are it had been plugged in and turned on at one time. Did it work, or did it do damage to the amp, your guess is as good as mine.

8 bids and up to $260, and quite possible that it'll go over $300 when the auction ends. Buying this just for the tubes and iron, the risk is very high. For that kind of money, you could buy new iron, and cost another $100 for new tubes, so is it really worth it to buy this and get the possibly non-working Mullards or iron?

I think people are buying this piece think that they are getting some kind of exotic good sounding audiophile vintage mod by some audio guru.

[avahifi]

It looks like me to add a huge power supply section to an original Dyna-70 by plugging in the second power supply box into the Dyna chassis via its original PAM preamp power supply front panel sockets.  I would guess the the input jacks on top of the second big box are simply pass throughs for the input signals, as the original front panel sockets were masked by the big supply box.

It is a rather pathetic attempt at making the ST-70 better. A little thought into better power supply management would have been so much more useful than this brute force attempt.  Yah, we did that too way back then with the extra 100,000 uF capacitor box for the Dyna St-400.  It seemed like a good idea at the time until I obtained the full time services of a good electrical engineer.  He showed me the math of the capacitive - inductive effects of the long supply cable leads and how the wildly underdamped resonances they caused actually left the amp with no power supply at all at some frequency combinations. It is pretty amazing how a little engineering math will trump audiophlake ideas, even my own.

Regards,

Frank Van Alstine

[rcag_ils]

SOLD for $340.00 + shipping wherever the lucky winner might be. I hope the buyer will have fun with it.

Thanks Franks for his input on amplifier power supply.

[mark funk]

I would like to be there when they plug that bad boy in!