Dynacord Hall-Jazz

For those building and repairing amps on their own. Learna and share ideas.

Dynacord Hall-Jazz

Postby Racing on Fri Sep 14, 2012 9:15 am

Over here in Sweden you run into old german Dynacords every so often,and at that more often than not at nickle n dime money.
Having fooled around with a number of them over the last couple of years i normaly find them full of good iron as well as tubes,albeit basicaly lacking any and all connection to the various sounds of rocknroll-being childs of their time.
In essence these amps are more directed at orchestra ditch work... In short they´re imo great basis for remodeling.

In this case then a rather light old 18w cathode biased combo of approx 14kg with a very "german" design. The package being date stamped march 22nd 1966.

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Got the amp as a no-go which was quickly traced to a ruptured resistor within the voltage divider setup. That taken care of and a common telejack jumpered in there,these units are usualy old DIN connector equipped,i fired her up..and sure enough. It all worked. Mind you the "Hall" designation then being german for reverb.

Most of the old Dynas carry a concertina setup "the old way" and what´s more the actual HJ amp in case carries all in all three inputs rendering basicaly one gainstage of each channel and then heading for the concertina driver. This brings that each of the stages carry the anode resistor that satan basicaly rejected to push ample amplitude and swing...

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Set her up that way and let her rip...and mostly came out laughing :mrgreen: . As usual. As stated...there´s absolutely nothing rocknroll about these old warhorses. Further,the onboard approx 10" speaker is something Dyna must have picked up surplus from the war as they sound like something that have been sitting on a wooden pole to work as part of a PA...
Well.
Baffle was ripped out of there and the scroll saw put to good use...and soon enough it had been replaced with a more contemporary 12;er. All good i guess.

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The "Hall" part of it deems a little attention tho. It is a stand-alone unit placed at the bottom of the cab. Driven by half an 83 and a full ECL82 and it is IMO one of the nicest sounding spring reverbs i´ve ever come across. For once a reverb that isn´t intended to mimic a hall room...but more so to be dialed enough to simply "wet" the signal to make it sound larger than life. This is a REALLY nice sounding reverb...

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As you can gather this is a PCB based unit,in contrast to for instance the Dyna Twen which is hardwire built,but don´t fret....the PCB is basicaly built to be tossed out a moving bus doing 60mph without any ills.
Lytes as well as various voltage diving highpower resistors were replaced and altered as far as values. At the same time i opted to cascade two of the channels to at least reach upon a platform where i could design rocknroll into the equation.

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The values for the preamp triodes were completely reset. Entry stages ingoing caps were tossed out of there aso,and as you can see a master was installed,and that was set to work between the concertina driverstage and the actual concertina. A 1MA pot.

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Likewise bias was reset with a slightly lesser ceramic and the decoupling of it was enlarged somewhat. Replacing various signal caps followed...

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These machines are tuberectified...and as stated they often hold "the good stuff" as far as tubes.

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Powertubes i tried a variety and ended up letting these Philips ones reside in there. They´re from approx the same time n era.

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...and then the final product. A small very portable combo...that carries distortion ability enough to give a JCM800 and run for the money...just at a lesser wattage. A bluesrock machine for the gigin musician all in all. Two channel,where the one channel truly is a "clean" ditto.

Main point of this post tho is that these often overlooked old tubers are anything but scarse and make for a tremendous platform to build something way more contemporary,and that at a very reasonable cost. What´s more...there´s way more brands that Dynacord out there that fits the bill.
This amp..just got sold and is being delivered to its new owner right now. Next build up on my behalf will be a "big brother" to the Twen/Jazz crop in as much as a Dynacord Rex. Very similar looking combo,just this time with a couple of EL34s out back and being a 212 at approx 20kg. Ie;none of that Fender Twin folly of 40kg+.

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Indeed... :lol:
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Re: Dynacord Hall-Jazz

Postby PeterS on Fri Sep 14, 2012 12:14 pm

Hot stuff. How big is the reverb tank?
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Re: Dynacord Hall-Jazz

Postby Racing on Fri Sep 14, 2012 8:36 pm

Rather small really,and it isn´t a tank per se...in fact it is suspended mid air and the springs...basicaly subjected to whatever.....
The thing is that the amps rear "lid" kind of make any and all interfere...a moot point.
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Re: Dynacord Hall-Jazz

Postby PeterS on Fri Sep 14, 2012 8:41 pm

Interesting that they managed to make the reverb sound good with a tiny 'tank'.
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Re: Dynacord Hall-Jazz

Postby Racing on Fri Sep 14, 2012 9:12 pm

Agreed.but a fact is that is sounds a million bux. It makes a Fender ditto come up second best.
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Re: Dynacord Hall-Jazz

Postby Doghousebass on Tue Apr 02, 2013 9:30 pm

Hi, good to read this stuff. I still have mine, it was my first amp, bought it somewhere 'round 1978. It's an early model built in 1961. When i bought it, the reverb was (and still is) missing as well as the reverb power supply. I want to get it working again, cn you tell me the specs of the reverb power supply so i can try and find one, or have it made? Thanx so much for helping out!
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Re: Dynacord Hall-Jazz

Postby Racing on Wed Apr 17, 2013 5:42 am

Sorry to say no as i sold the amp a while back. Never took notes of the specs for the reverb.
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