Reissman KR-56

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Reissman KR-56

Postby Racing on Sun Jul 12, 2015 12:09 pm

The story here is that i´ve seen these for sale on German ebay on occasions,and came to put them "on the list" as i think they´re rather odd looking and half cool.
For some mysterious reason tho they always end up being half expensive? What had i missed here? Then...just last week there was one rather sorry looking KR-56 up for grabs with a given BIN..so..

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Sorry looking. That´s being polite in my book. This one has certainly been to WWIII and back..
Well? What´s the deal? Reissman amps were made in former Eastgermany in the town of Dresden. Correct..what we´re looking at here is bonafide communist stuff from way back. According to legend made back in 1960. A true "kofferverstärker"(suitcase amp) in the true meaning of the word. Rather compact in size and weighs in at 12kg.

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Whoever picked the colour plan must have dropped acid,but that aside.."kofferverstärker". Indeed.

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Chassis is out of simple folded aluminium. Amp has most likely been dropped a couple of times,and seing the involved combined weights of the three transformers..the poor chassis didn´t really have a chance.
On the positive side tho,it´s all there. Down to the stock knobs.

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The reason for having been dropped...it evident to all i guess :mrgreen:

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So. The amp is of a claimed 20 watts. All powered through this EZ-12. Have used EZ-12 before on occasion,and it about seems right as what we can get out of it is approx 100mA+. IOW,to get more power out of this piece that there either needs to go or needs to be assisted.
As of current i´m thinking along the lines of one of the octals. Mainly as i by choice of octal can set B+ due to their differing voltage drops.

That said the powertransformer sports various taps to cater to different wall voltages too.

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´N here then what really caught my attention. The EL-12N. Read online a while back about this bloke that extracted 40watts+ from a pair of them and..that would do it. In fact a "mere" 20watts would too seing the compact size of this thing...none the less..
Apart from the normal EL-12 there was the EL-12N,the EL-12 spez and the EL-12/375. From what i´ve come to understand the latter EL-12 models then toobs that lend themselves to guitar use as they are sort of EL-34 soundalikes. Just with an even more disbahaved ability of distortion.
One of the powertubes were missing why i got me a replacement from out local radiomuseum.

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Amp sports a rather old standard as far as inputs why that there funky looking thingy in short is a converter. From old school backelite no less. Eastgerman engineering at its finest i guess...
Speaking of which the amp as a whole tho strikes me as well and sturdy built. Thought through in short.

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It also sports what i came to understand these two mic trafos. No need for them tho so...

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The small round hole next to the DIN jack is a socket for linking amps together. Ground.
The DIN plug in turn is a real peculiar solution to speaker out.

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Internally tho is another matter. Amp looks about like new almost. Upper ledge...are yet three of them about universally used German "tower" e-lytes. The two that takes first hit and the screens for the powertubes are outside the chassis.

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Yep. Sports a choke,and that resides within too.

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Again. As a general whole the hardparts of the amp strikes me as of high quality. No argument there.

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Inbound voltage is set by losening that setscrew there and rotating that black plastic thingy. Inbound jack will of course be replaced,that there is an obsolete standard by any measure. Got a few of them sockets buuuuuuuuut...no. Just no.

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Bent to hell n back. You could say that again! Anyways. That there are the sockets for the EL-12N flasks.

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Yep. Microphone transformers. Have no need for these as this will become a guitaramp so..

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Intent was to fire the old warhorse up. Doing so ment that i cleaned her out from the last 50yrs of dustbunnies and nicotine residue and what have you not AND took to check all the elytes out with an ESR meter.
As it turns out the last in the row was shot. I sure didn´t have any 8uF tower lytes on the shelves so..installed a make do one just to get by on initial startup.

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Again. Chassis really IS that busted. Out of aluminium tho...so no reason to fret. As i work with metals on a daily basis straightening that thing there out is the least of my concerns to be honest.
No matter...that there is as i fired her up,and indeed..the thing works. Hip-hap wired a tele inbound and one outbound and let her do her thing. Checked voltages all over asf.
As a whole...we were good to go.
So? What it sound like then? Naaaaaaaaaaaaaaaawt all that hot IMO. I guess i would second that this thing makes like 20 watts or so at full power. Might be. Sound out of it with a guitar is nothing short of dreadful tho.

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That brings that a decision or two needs to be made. Mainly choice of rectifier. Amp hands a rather precise 400VAC between each tap and chassis..bringing that a starting point i guess would be a 5U4GB or similar. Mainly as we KNOW what voltage drops to expect from that series. Issue at hand is that it takes something the transformer lacks.
5VAC heater... Now. On the other hand then this piece sports a myriad of 6,3VAC ones...and it might very well be that i can use one of the UNUSED such to power a 5VAC tube. We´ll see i guess.

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Then,to wrap this story up for today,a picture of what the final product is supposed to look like. There were two versions of it. The one above that uses the EL-12N powertubes,and a later one that uses an EZ-81 and a pair of EL-34´s.
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Re: Reissman KR-56

Postby Racing on Sun Jul 12, 2015 7:36 pm

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It would without a doubt have been WAY faster to just fold a fresh chassis. As i picked it clean..it was bent n skewed all over. Not ONE flat surface left...daaaayyyuuum this thing had seen some harsh handling.
Spent the better part of three hrs straightening the thing out,and it got decent at least. Sorry to say some of the paint chipped,but that is to be expected i guess. No matter,now i´ve got me a chassis that let´s me put things back in order.
´N yep. That pesky EZ-12 has been replaced. For starters with a 5R4GYB. That way there´s at least ample wattage to be had...if it amounts to to large a voltage drop i guess we´ll take it from there.

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Yep. Even got the sockets for the EL-12N´s installed. Will have to dig up a fresh pair tho..

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As stated. The mere job of making it look like that was a real chore. IEC jack installed as can be seen...we´re getting there gentlemen.


As i took her apart it became real evident that there was a plethora of solderjoints that were downright broken. Cracked. It had wires installed that could to the letter be lifted out of the prongs in case.
In turn the mains jack..don´t get me started. No matter...we´re heading in a way different direction now,that much is for sure. Need to figure out where to make another noval fit tho..
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Re: Reissman KR-56

Postby Racing on Mon Jul 13, 2015 8:45 pm

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Old amps... Credit where credit´s due. As is often the case older stuff was made with an entirely different mindset. In short..them pots,just pick ´em apart and hand them a good clean and they´re good for another round of 10+yrs or so.
Quality.

That said i scavenged my own stash and came up with a nice looking mains switch,that i of course installed.

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Right. Serviced and good to go.

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For better for worse parts of the wiring loom had seen better days. So..replacement time,and in doing that..a few pieces of shrink sleeve and tiewrap anchors does for a way more sano install.
The pot in turn...this amp sports a downright crapload of heater windings,and thus..the pot is for heater balance for the powertubes. Something most likely not needed (it usually suffices to just ground one side when talking powertubes as they´re that late in the chain) but...better safe then sorry.

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So. I scrapped the stock EZ-12 right and replaced that with a 5R4GYB. That rectifier carries with it ample amperage capacity while handing me a rather hefty voltage drop. IOW..that choice wasn´t sans afterthought. If it turns out that the voltage drop is over the top..i can always replace with a different type,as long as we stick to a maximum of 2A heater.
The 5R4GYB states rather low capacitance for first hit. One way of cheating that is by the use of a large capacity resistor. This will work as sort of a buffer for how much inrushing current can load the rectifier. In this case the amp was set with a wirewound 82 Ohm resistor from the onset,so that got reinstalled.
The smaller,also wirewound,green coloured resistor in turn is a 1 Ohm resistor placed in series with the to high a voltage heater winding. Net result? Juuuuuuust shy of 5VAC. IOW..perfect match.
The 82 Ohm resistor in turn is "locked"in place by surplus pieces of component legs and hence..it ain´t going anywhere soon..

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Cab in turn. The handle for it was broken right,so i took to repairing that with some "bear thread" and glue. Ditto for the still intact part of it,glue..with hopes that it´ll reinforce the "bearing" surface.
Still need to clean that real UGLY tolex out tho..
Various fittings in turn...gets hit by the rotating wire brush. Rust..ain´t no fun. At all.

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Here´s where we come to understand that the amp is old. I strongly suspect that there to be old Eastgerman asbestos!!! Not for the faint of heart! IOW..Reissman handled that there with inherent heat by the use of...asbestos. Uh....yeah. Now. As an,by default,aeronautic engineer i know a thing or two when it comes to thermals. So.. What really needs to be done is an opening the other side of the cab. That..and to keep the cab itself intact maybe a couple of small pieces of "welders rug". Just staple that stuff in place and be done with it. Sort of.
That STILL doesn´t deprives of the need for a slit or whatever high on the cab. It friggin needs it. Think about it for a sec. Tubes´ll survive..that´s the least of problems,however stuff like resistors/e-lytes and what have you not DO take a beating from high temps. Period. Ergo,this needs to be adressed.

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So. Starting to get an idea of what´s to come. A couple of things are for certain. First up i need to install yet another noval to reach what i´m after,and TRUST ME...space is limited.
Second of all, i need to do something about that lower stretch of the faceplate. Got no need for all them holes and it looks ...less then satisfactory.

Space limitations will make for the glass running hot. No argument. Implementing yet another noval sure as hell won´t alleviate that by one bit. Screens/hats will of course be used for the small signal novals,but i wonder if that´ll suffice. If not i guess i´ll have to cut some sort of heatshield to size and take it from there.

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Yup. Same boards i always use :mrgreen: . Bias circuit setup and works like a charm... The 3 pronger is in place and kicking.. In fact,as a whole we´re about good to go.
Only thing lacking ATM is a fresh pair of EL-12N´s. Will import them,too,from Germany..
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Re: Reissman KR-56

Postby Racing on Tue Jul 14, 2015 8:18 pm

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K. So the amp got an additional noval. Not only that,but seing that as i of lately have come to use EF-86´s a lot V1 got rubber suspended too. Point being that EF-86´s don´t take kindly to vibrations,as none of the small signal pentodes. Suspending the socket like in the pic certainly helps,and if one was to go the full 9yrds...linz wire should be used too i guess.

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One of the more boring chores of putting a toober together is by FAR laying down wiring for heaters. That said this Reissman sports a downright c*apload of heater windings and what that brings is that the two ECC-83´s get one and in turn the EF-86 one of its own. Main point being that this way we can control any and all hum with way better resolution. Or at least...that´s what i hope.

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Yup. Coming together.That there gives you an idea how cramped for space it has become seing the install of that last noval.

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So. Two boards will be used. This one then sports all that´s needed for the three novals. Main e-lytes included. Major components in turn have been granted a dab of glue to stay put. Rather safe then sorry in short.

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Right. Whoever picked the colourscheme for this thing must have been on ´rooms..cause DAAAYYYYUM that an ugly cab! No matter,all the trimmings got hit with a wirebrush and the actual tolex in itself i cleaned out with washing acetone. Yup...diehard style,but tolex was in that bad a shape that there really was no other way..and it came out ok at least.

That said a pair of fresh n matched EL-12N´s has been ordered and should show up beginning of next week. At least i hope they will. That brings that i´ve got ample time to finish the rest of it i guess.
As far as the lower part of the faceplate,i really need to adress that and what i´ll try is the same approach as i used for the Geloso G-27. In other words a cut to size piece of anodized 1mm aluminium...mainly to hide all them unsightly ugly holes i´ve got no need what so ever for.
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Re: Reissman KR-56

Postby Happy Face on Wed Jul 15, 2015 2:30 am

Krikey!!!
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Re: Reissman KR-56

Postby Racing on Thu Jul 16, 2015 11:41 pm

:jam:

Well. Seing that the powertubes won´t touch down ´til next week as stated i´m in no real hurry..really.

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Saved as many of the OEM pots i could. Setup a James network..

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Installed a pair of jacks out back.
Then. Swung by my metal wholesaler today..closed for vacation :? . Well.. No wonder. This country basically closes down for a month mid summer... In other words that there with a fresh piece of sheetmetal for the faceplate will have to wait.

That said i´m pondering if to make this thing relay controlled.? Have also played around with the idea of implementing some FETs to "kill" grids as the actual swap in/out takes place.
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Re: Reissman KR-56

Postby Racing on Sun Jul 19, 2015 11:37 am

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...and now we wait... :D
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Re: Reissman KR-56

Postby Racing on Tue Jul 21, 2015 10:04 pm

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Well,the powertubes arrived and...who was i to route the last couple of wires in an orderly fashion?! I mean...HELLO! Time to check this badboy out!

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...and i´ll tell you what. The wait for them EL-12N powertubes...worth every second. Every penny. The few that have used them for guitar work basically all attest to that they´re more "raw" to the attitude then EL-34´s ´n ...yes. Yes they are. In a really really good way. In short,should you run across an EL-12N equipped amp pick it up and make the MF roar. It for once IS worth it!

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The choice to swap the EZ-12 for a 5R4GYB in turn..also on the money. As the amp settled,it is cathode biased stock remember,it came to rest at just a tad over 440VDC@32mA per tube. Just what the doc ordered.

Had a few issues..it hummed a bit. My bad as i hadn´t hooked the internal screens of the EF-86 up to ground...that said tho...this amp is one SERIOUS performer!
It carries with it a kind of "jagged edge" attitude to the sound that i´ve rarely encountered before and i attest that to the EL-12s. Now,work remains. Of course it does.
In doing so..i´m debating if to make this one relay/opto controlled. In this case loops and what have you not are out. My thinking with this badboy is rocknroll is its absolute most basic form,and a 2 channel (sorta) setup that works they way this thing does....done deal. Really.

In turn,having leaned on it rather hard for like 20-30mins or so..that thing there gets warm. Hence i can appreciate the use of the asbestos cards that were stapled to the roof of the cab. Asbestos tho is of course out,and will be replaced with small pieces of "welding blanket". However..stock or no i will most likely also cut a "rail" of sorts rather high in the actual cab to enhance airflow through the thing. The stock setup...20watts,and the heat it brings..already there i´d saw we´re on the ledge.. So,with the increased power out of the EL-12´s..and in turn having added a noval.. Nah. It needs a vent cut into it. That simple.
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Re: Reissman KR-56

Postby Racing on Tue Jul 28, 2015 1:10 am

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Been a while since an update.. Pilot light from an old Dynacord,but more importantly....the microswitch for channel switching. Or..it really isn´t channel switching,it is a matter of putting yet another ball in play.
The relay engages an EF-86 atop the already running preamp.

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As the chassis sports sort of crossmembers underneath i took to installing aluminium tape across the entire floor of the cab and thus make it all into a shield of sorts.
As it turns out this rather compact amp got plagued by interference. I´m guessing to the rather cramped space,after all,within. So. I moved the relay around a bit and tossed a few other trix at it and..presto. Silent in idle.

As you can clearly see i still lack the pieces of sheetmetal for the faceplate as well as an actual "grille". Going to look into that as soon as my vendor opens their doors again.

No matter. As is..i´m getting accustomed to the amp. You can certainly push it into compression,which is rather rare with my amps,but that is more a matter of how you dial the tonecontrols then anything else.
What that brings is that by backing off on bass...we enter hardrock territory in EF-86 mode..while at the same time..back off a bit on the gain from said EF tube and increase bass...and we´re in bluesrock mode.

One thing i still need to figure out is where to place the jack for the footswitch. In turn..don´t get me wrong,the amp absolutely sounds da bomb,i´m giving thought to implementing a presence control of sorts.
As of current,IF i do,my thinking goes back to the german made Klemt amps..and be more elaborate by setting it up as a reverse run Twin-T filter.
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Re: Reissman KR-56

Postby Racing on Fri Jul 31, 2015 7:17 pm

Hm.
One of my old dragrace camaros had a sticker. It said...
"Get in,sit down,shut the F up and HOLD ON!"
Well.

This is where ol´ bonafide communism runs into someone like me. :mrgreen:

https://www.youtube.com/watch?v=5OA-UqD9ufE&feature=youtu.be

Yup. Bad guitar day...yadda yadda yadda...but u guys get the idea at least. :jam:
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Re: Reissman KR-56

Postby Racing on Mon Sep 07, 2015 10:42 pm

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So. Finally got my ass in gear and handled the missing pieces. Still need to do something about that lower piece of aluminium tho...looks way to "bare".
All in all though.
One rather cool performing old communist... :mrgreen:
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