Stange und Wolfrum LVM-30

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Stange und Wolfrum LVM-30

Postby Racing on Mon Aug 03, 2015 10:03 am

You old timers might recall that this is a sort of revisit.
Revisit in as much that i´ve done a LVM-60 a while back,and true enough this LVM-30 is out of the same series of offerings.

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Just bought it over german e-bay friday past. Where the 60 is a physically rather half large,and heavy,amp the 30 is of slimmer proportions alright.

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Knobs,fonts asf asf are the same.

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As usual when it comes to the german made offerings of the time a rather thought through piece of kit. A PA amp of course.. For some reason it´s rather rare to see the LVM´s run into the ground?
Dunno why that is.

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So. On one side the DIN entry jacks. ...

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...n the other side exit jacks,voltage selector,mains fuse and what not.
Yes. The sticker ain´t no lie. As is half common with older Philips amps and what have you not it´s also marked for output in volts.

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Underneath resides three trim points. No idea what so ever what for thus far.


So. Stange und Wolfrum.? So what?
Well. These were made by SuW alright in the mid -60´s in Berlin. The sidekick in all of this is that they were also produced with the Telefunken logo,and that is saying i bit i guess.
True point to point amps of REAL high quality.
The LVM series seems to have started out with an even physically smaller LVM-8. An amp that runs ECL tubes for power. Then the LVM-15,which shares chassis with the LVM-30. The 15 and 30 basically the same amps just..2 or 4 powertubes. Then we jump ahead to the 60,and see the 60 is a REAL powerful amp where the plates of the powertubes sees inxs of 700VDC...and then its bigbrother the LVM-120.
The 60 with twin EL-34´s and the 120 with a quad of EL-34´s. Seing how loud the 60 is...i for one have a hard time taking to heart who in his right mind really needs a 120.
Anyways.

http://www.creapromedia.fr/lesdocs/telefunken/lvm%2030.pdf

That there is the schematic for it in PDF form. Note the tonecontrols..and the 1M Ohm plate resistor for the concertina driver stage.

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Within in turn..no surprises. German "ordnung",as simple as that.

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As you can see it sports sort of "boxes",which i guess is to shield the thing off. 4pcs of EL-84´s as mentioned..and in turn a selenium rectifier. The latter..will have to go. I always replace them when i run into them,mainly as a blown selenium rectifier is toxic as hell and hence it´s always a good idea to replace with regular silicon as you run into them.

So. Current thinking of mine here is a sort of AC-30;ish kind of deal. Seing the quality of the unit..it´d be a hard act to follow IMO.
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Re: Stange und Wolfrum LVM-30

Postby Racing on Mon Aug 10, 2015 10:03 am

Been on vacation for a few days and that means that although the LVM showed up i wasn´t there to pick ut up.
So-
Did last night and...it´s in a real nice nick. REALLY nice. Basically all that is at fault,from that perspective,is a layer of nicotine. That´s it tho.

The actual cab/shell (which is out of sheet metal) slides off sideways as you´ve removed the cast metal end pieces. Rather neat solution!
´N yes..the amp is certainly "german" to the build.
Alll hardwired,per nomer,but be that as it may...still in an orderly fashion.

Any and all preamp components resides within that forward "box". Rather neat.

Preamp tubes,and PI,are all Tfk´s. Powertubes in turn are Ultrons,and that can mean about anything as Ultron basically just put their label on anything out there that was up for grabs.

So. What to do with it? Or more to the point,what to make it fullfill? :jam:
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Re: Stange und Wolfrum LVM-30

Postby Racing on Thu Aug 13, 2015 5:07 pm

Right.
So a few days off certainly made for a world of difference. :D Gonna repeat that shortly...but,for now...back ontrack.
´N see..as this thread is worthless without pics.. :mrgreen:

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The only real issue with the amp was that the first in order 22k resistor for the voltage rail was shot to kingdom come. Remedied that alright and...presto. Working amp.

Checked each of the main e-lytes out for capacitance and ESR and they all showed the same...36uF and approx 0,38 Ohms. IOW...good to go.

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Amp is built...different. I for one will attest to that. That brings that the actual solderstrips used to cater to the 4pcs of EL-84 for power and the sole ECC-83 used for PI are bent to become horizontal. Brutal and to the point. Profile of that part of the chassis is rather low so...again. Smart thinking in short. Now..this will be modified in a number of ways to cater to the amps new needs...but i will stick to the idea of regular supports for this..just remodel topology.

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That trimpot there is where the amp sways away from the schematic. Accordning to schem that there is supposed to be a 33k resistor,which it is obviously not. IOW..the amp sports adjustable bias voltage from the factory...all good.

That shield there tho...over the pot. That is to shield the rest of the amp off from...incoming AC. The mains switch resides within the treble pot..and by no means do i come down on that per se,however..i do on the fact that it doesn´t cut both neutral and phase. See..here in Scandinavia we can turn the plugs either way...hence the law states that a mains switch needs to cut both lines. Ergo..it will be replaced by a more common day n era switch.


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Recall them three holes at the bottom of the cab? Well...here´s why. To the left an "entbrummer",ie a balance pot for the preamp heater circuit. Next to it are two pots to alter tone for two of the channels. No need for those tho so...bin time.

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Socket centers has them protruding deals...and as can be seen a groundbus of sorts. This i´ll keep...however the grounding of the components for the PI will be moved to where they need to go. That brings that powerground can be routed as i see fit,which is always a good idea.

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Obsolete. Yep. Them stock DIN input jacks has all met their new home. My scrap bin.
Furthermore...i see no reason to keep 4 entry points. Haven´t decided thus far tho if to run the amp relay/opto controlled. Guess it would be the wise thing to do tho.

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Here in turn the speaker out jacks. Again completely obsolete and just as obvious as far as being replaced by what we use today..
In turn the voltage selector...and mains fuse.

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Ah! Yes! The selenium rectifier. This dear friends..should be replaced as soon as you run into them. Thei current capacity is limited and their wear properties...not so good. That brings that you have no idea what so ever what it has been through during its life cycle..and thus how worn any of the tiles within has become. Now...it just so happens that the gas omitted when they go boom is toxic...and as such they should be clipped out of the circuit and put in a sealed bag with due notice to the scrap boys taking care of it.

Then again. German. Rectifier sealed vs the "working end" of the amp by a rather hefty piece of sheet metal...it´s as always in the details isn´t it. :mrgreen:

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Uhu. Uhu. That´s where i left the amp the other day. Yep. Basically clean slate... Giving a bit of thought to how to go about this.

I guess most would cry out "AC-30 done right"...mmmmyeah. Maybe so. Maybe so. It´ll get a loop tho. That much i´ve decided on. Rest of it tho...
Personally i´m rather fond of the EL-84´s. Think they bring a "rawness" to the sound i like.
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Re: Stange und Wolfrum LVM-30

Postby Racing on Thu Aug 13, 2015 7:11 pm

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Well. Sometimes it´s nice to be wrong! Hadn´t turned the switch around had i...and as it turns out it IS of the twin breaker type. Well..that´s one hole less to handle! :mrgreen:
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Re: Stange und Wolfrum LVM-30

Postby Racing on Sat Aug 15, 2015 11:31 am

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Hardwiring. No matter what it always looks like a major cluster F.... The PI reset to a longtailed pair. Regular component values as far as topology. In other words nothing all that much to write home about.

Added a few rubber grommets where wiring is to pass through the chassis sheetmetal...

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This tho...another matter. This is where i get to eat my own words cause..this was NOT especially "german". Why? Well,for those not in the loop them electrolytes there are fastened by the use of that plastic nut for each of them.
Then there´s supposed to be an insulating fibre washer,a sheet metal washer-which is there to act as a solder lug,and in turn a wave washer to act as form of a "lock" for the plastic nut.
This done...each e-lyte hits ground via the use of a wire soldered to the actual lug on that sheet metal washer and hence grounding for them can be routed to hearts desire.
Not so in this case. What we´ve got here is a bonafied band-aid solution,cause each e-lyte carried no insulator what so ever but three of them wave washers a piece and this to "shim" the e-lytes upwards in the chassis to keep them from bottoming out vs the sheet metal cab!
This ALSO means that the e-lytes basically hit ground all over the place...

No more of that so fibre washers were added..and i had to "shim" them still...piss ass solution IMO..but the only reasonable one seing the parameters.. and that in turn from a purely electrical POW made it possible to control ground at least. As you can see i came to replace a bit of the wiring too....

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No. No,it isn´t done. A work in progress where i opted to "build" the thing first. What i´ve got in mind is to secure the thing by the use of small pieces of shrink sleeve. Anyways. That there is a zener in series with a 100 Ohm resistor heading for each g2 of the powertubes. A setup i´ve come to use a LOT when working on "lower power" amps lately. It works and it works a million bux worth. End of story. In this case,as i see rather hefty voltages already as is,BEFORE i replaced the selenium rectifier with a modern day n era silicon one...i opted to drop voltage for the g2´s in a rather severe manner. 47V a pop..
Mainly do make sure that there will be a rather large difference in potential between the screen and the plate at all times. Have in mind that datasheet states 300VDC maximum for EL-84´s...

While at it i opted to play around the full 9yrds with the bias circuit. So..replaced the e-lyte and added one..replaced the trimpot with a new one and in turn rerouted it´s ground (bias winding is cmpl separated)
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Re: Stange und Wolfrum LVM-30

Postby Racing on Sun Aug 16, 2015 12:06 pm

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Pushing forwards gents..pushing forward. As it turns out the stock mains switch could handle both phase and zero. For the better as it makes the thing more i line with Swedish legislation.

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Ah! Yes. The grounding of the main e-lytes. By the install of them insulating fibre washers i´m no able to control how routing of ground goes down. For the better as the stock setup was mainly one major chaos.
This way i´m in control of the "power circles" at hand and hence..set out to make the best of what´s at hand.

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I´ll need to reinvestigate this a bit,but no matter..that there is the 4/8/16 Ohm output jacks.

Then..got to redo them "homebrew" setups for the g2´s...shrink sleeve indeed. I started out populating that "Vox" board for the two front end noval sockets..
Started to take the stock pots apart to clean them out.. Getting there...bit by bit.

Sorry to say tho something hit the "nipple" of one of the Ultron EL-84´s thereby ruining a complete quartett of powertubes. Pity...
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Re: Stange und Wolfrum LVM-30

Postby Racing on Mon Aug 17, 2015 11:34 am

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I know...i know.. Going hardwire always looks more or less clustered all said and done. However as one approaches it there´s at least some sort of logic to the insanity.

Am i saying that the amp is up and running?
Yep. Exactly what i´m saying. :mrgreen:

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As stated i kept with them solder supports and the principle of hardwiring. That in turn left ample room onboard that "Vox" board.

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The thing here,which we mainly see in mainland European amps,is one of afterthought. Huh?
Yeah,well... As you can see the working end of the amp,for lack of better words,resides within a sheetmetal cage. Sort of. Also take the actual cab into account when regarding this fact.
What it in short hands us is a very effective shield...and indeed,after sorting out a few errors upon fireup...the amp is as well behaved as they come.

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The stock pilot light was a damn joke. Found a replacement in my parts bin....but the thing here is that i also needed room for a microswitch. Ergo i drilled a fresh hole for the pilotlight and that next to the treblepot/on-off switch.
Worked like a charm.

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Right. German made. Period.
All said and done this is a rather compact made amp,weighing in at approx 12kg,seing its output power. One thing to note is the orientation of the two trafos. Placing them like that put tremendous demands on control of magnetic fields omitted...n....German made. Period.

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For some reason the voltage selector lacked any and all reference markings. Not the end of the world,just a matter of DC measuring the primaries,but none the less rather "non German". As i´ve replaced the selenium rectifier with modern day n era silicon B+ voltage jumped,and that a fair bit actually.
So.
Played around with the amp in 220VAC and 245VAC mode both. Came to settle for the 245VAC one.
That renders me approx 380VDC in B+ all said and done. The powertubes in turn...right. One of the stockers was AWOL. Replaced them with a nice set of old General Electric ones.

Issues. Yes. I fired the amp up in its new guise and was greeted by a working and by any means functioning amp alright,but one plauged by a minor hum.Now..that simply isn´t right as i could alter it by the use of the amps gain knobs. What´s more...50Hz ditto.
So.
Out the DMM came and i started to reference everything in sight and what showed its face was yet another "non German" flaw. This amp sports dual heater windings. The one runs for two of the powertubes,the PI and the front end. The other...for the two remaining powertubes.
The former´s got that balance pot...so no issues there. The other just states that one of the windings taps be grounded. Well,guess what. It wasn´t.
That brings that the heaters for the two powertubes has most likely been left floating since birth of the amp....not espically German to be blunt.
Well. Took care of that..fired her up again and set the balance pot for the OTHER winding for minimum hum and we were in business.

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As stated the actual "cab" slides onto the chassis from the side. Rather nifty setup. End pieces are missing in the pic,but you get an idea at least.


As is a few things remain to be done. As the amp is relay controlled i´ve put another of them PSU´s together. What i plan to this time tho is to implement an optocoupler or two.
Or..the jury´s still out on that one.

That said.
I again want to recomend anyone out there in the market for a "DIY" platform amp...the LVM series of PA amps. They ARE very "German" to the build and what that brings is that the mainstay of what´s needed from a design POW is already taken care of.
The LVM-30 in this case being...sturdy built.lightweight and powerful.
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Re: Stange und Wolfrum LVM-30

Postby Racing on Mon Aug 17, 2015 11:32 pm

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Yep. Homerun. Sorta.

As some of you know i´m sort of partial to the James network. In general i feel that way to many that fool around with putting tube amps for guitar/bass use together..seems to completely jump the fact of the James.
For gutiaruse...you´ve heard clips i´ve put up..midfocus.

Now. This amps sports sort of a Baxandall stock. A setup related to the James alright and one where i´m limited as far as experience. My mentor tho..is not,so part of the drill here was for me to evaluate the Baxandall and at least form an opinion of my own.
Aleks sent me on my way with a basic setup idea..and i took it from there.

As much as i really find that the James network has merit in the application....It carries with it properties no other generic "tonestack" does..for guitar use. By simply altering component values you can in essence go from mild to wild...
Now..enter Baxandall...and the whole thing goes into orbit. i´ve really really tried to come to terms with the Bax today n... I´m here to tell you that there IS such a thing as to active tonecontrol setup.
In compartion really slight alterations as far as component values can push a Bax into something unusable. A lesson in its own IMO...

Be that as it may i opted to challenge the James even further due coarse.

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So what i did was add yet another capacitor to the normal James via a microswitch,and presto..we had ourselves midshift. A real active such too. In fact it came to be so effective i´m giving thought to adding more microswitches...just for the hell of it.

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Added a bright switch too. Them two switches together makes for a WORLD of difference,let me tell ya..

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Hm. I got to install pieces of sheet metal to cover up the old holes and what not..and got to install all the jacks needed. The PSU for the relaycontrol...asf asf.
So. In short we´ve got us sort of a staged/twin channel setup that can roar from just a tad shy from crunch all the way into -90s metal.

...more to come tho so stay tuned.
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