Rauland W-819

[Racing]

Now. This is already a sort of story with a twist. For those not in the know Rauland were manufactured in Chicago Illinois USA. Their reputation are..above average. They´re all PA or radios.

So. Ran into that there unit in Holland. Picked it up for a song...when the seller told me he had a few more....



In contrast to the one in the pics there the other one was claimed to be basically as fresh as can be,seing these amps were made in the -40´s.

Well,"Mr Handyman" sure as hell has a field day with what could best be described as british racing green and a brush. In short..looks like crap. Amps are from the -40´s in turn as Rauland changed their design in a rather vivid way as the -50´s arrived.



Yep. It sure sports a myriad of tubes. That much is for sure. All octals as can be seen. Please be adviced that some of these Rauland sported all in all 14 tubes!



Uhu. A 5U4 as rectifier and then a pair of 6L6G´s.



Seller told me the unit is working,and true enough. A man of his word.



So. Both amps showed up,and in one piece. Thank yooooooou... The "green monster"...uhu. For lack of better description i´d say that the amp has sure as hell been handled. Mr Handyman and all of that...



Oh,they are all there alright. Just took the rectifier and powertubes out as i took the pic. Finish of the ENTIRE amp/chassis is "messy"...not that it bothers me all that much TBH though.



Transformers for the amps sure LOOK a lot different,while the OT´s seems to spec the same. 4/8 Ohms..then for 200 Ohms and 500 Ohms. Some of them taps will,as you could expect,get deleted.



Within the wings of time. Looks alone sort of verifies the age of the amp.



Yep. Even sports a fuse,both of the amps. That socket will all them colorful wires is speaker out.

With a twist.
Yeah. With a twist cause see...



The one aimed for my friend indeed looked a TON better. Beautiful design even.



Faceplate is lit through two small slots. One for each side. Neat... Lights are regular small bulbs run off of heater voltage.





Uhu. Duly noted.
Both amps share tube setup 100% btw.



Nicer nick? Yeah,that and then some! Most likely made in 1948 and clean enough to eat off of!
Notice the placement and proximity for the two transformers.



Uhu. Completely untouched,complete with old fashion pulldown resistor and what not.

So.
What about that twist? Well. My friend could care less for that beautiful old chassis so..i happily accepted his offer and took the thing under my wings. That means that what´ll happen here is a chassis swap.

That simple.

Now. Guitar amp time.

[Racing]

Bench always turn into a disaster as i scrap amps. That green monster,chassis is guess would be usable but to what avail really? The one chassis that my friend handed me will come out 100 as i hit it with some paintcleaner and a buffer.
The output transformer in my case has been replaced by a Dutch Amroh. No worries,and as it turns out the specs for it were available online. No harm no foul in other words.



The powertransformer is absolutely MASSIVE. Guess it won´t budge all that much even at wide open throttle. That said,as you can see the chassis is built up as sort of modules. For the better IMO as that sure as hell makes it easier to build the thing as well as clean the paint out.



..and that absolutely glorious faceplate. TALK about art deco! Yeah. This´ll turn out real nice with a little work.

[Racing]

Drilling into the FP was inevitable. That simple. For modern day n era use coupled with the fact of a firm installed mains wire that brings that i NEED a mains switch that cuts both phase and zero and done deal. Of course this also entails the install of a safety ground.

The hole left in the FP after the stock mains switch...well,what can be more correct than the PPIMV pot taking it´s place?



So. Hit the chassis with my buffer and sure enough...it downright sparkles now... Install of the two transformers were rather straightforward. Nothing to write home about really. The aftermarket ooutput transformer by Dutch "Amroh" had be a tad worried for a while but...as it turned out all the info ever needed was available online! Talk about homerun huh? Seing the transformer isn´t exactly of todays date...hello.
As it turns out though Amroh has been in business for quite a while,dating back to the -20´s even.'

Still pondering the layout for the circuit tho and..closing up on a decision being needed....

[Racing]

Yep. Yes,i´m a nerd. So shoot me. Why´s that?
Well...i took to stripping the 70yr old octal sockets down and cleaning them out completely. Retensioning each pin.
Them old ceramic sockets in short got a new lease on life and for lack of better words it just feels right to keep some of the parts the amp was originally made up of.

The transformers came to fit rather well as you can see. Had to open the cutout up a bit for the PT all said and done,but no harm no foul.

Then per usual i´d say. Fuse holders and "saver diodes" vs the tube rectifier and so on.

[Racing]

Sittin´ here debating with myself ATM as far as circuit and tube layout.

The 5U4 and the 6L6G´s are a given. From what i saw as i hooked the thing up first thing what we´re talking here is a healthy like 410-0-410 out of the HT secondary in volts AC and..that´ll make for a rather powerful amp. Even with oldies like the 6L6G.

The 6L6G was introduced back in 1936 and caught on the "horsepower wars" that were all the rage at the time. Rated at a mere 19 watts tho,compared to for instance 6L6GC of today that is rated at 30 watts.
However. All is not that simple as output power will vary with B+ voltage and powertransformer capacity in VA. Hence why i bring them approx 410VAC up as that will shove the envelope out of spec a tad for the 6L6G oldboy.
These were never rated at more than 360VDC..and we´ll surpass that with ease in this case,making for a more powerful amplifier no doubt.

Pushing the envelope on ONE count is USUALLY ok when it comes to specs out of datasheet for a tube. ONE...and USUALLY. I know for a fact from previous experience that the 6L6G will take the heat without breaking a sweat even and i´ll make damn sure i keep voltage for the screens/g2 under tight control via use of zener diodes.
So.. Guess we´re all covered there.
The 5U4 in turn is a rather powerful tuberectifier and will suffice at powering this amp with ease.

So. What´ll be the magic then?
In a word,the octals. Often these days we have come used to using noval tubes,or similars,why the many a time older design octals get overlooked. This in the same manner as we´ve come to focus on maximum amplification factor more than anything else.
Well.
This is wrong. Uncalled for.

First up many of the older octals have their equivalents in novals. No argument. The 6SL7 vs ECC-83. The 6SJ7 vs the EF-86..and so on.
What i´ve got at hand here IS a few 6SJ7´s and as i´m no newcomer to using them one will be deployed. The small signal pentodes as a whole have a LOT talking for them if you just take care in setting them up.
The 6SC7´s then?
Well. This is a twin triode tube alright and a medium gain such but...it kind of falls on its face as the two triodes have a shared cathode. In short that will "disarm" me and my options as to how to set the amp up.
In short the 6SC7´s are out.

Then for the 6SN7. A low gain tube which carries a few similaritys to for instance 12AU7/ECC-82. Now..that might be a good idea,so i´m currently giving thought to using that for a phaseinverter. Its primary advantage is that it can handle way more current then the high mu triodes.
IME the old 6L6G´s crave quite a lot as far as voltage swing to hand us what they´re made of so.. Is all that voltage amplification from a phaseinverter needed? In short,no.
At the time the signal hits the PI most of its job should be done anyways so... We normally see an amplification factor of approx 30-35 or so with an ECC-83 and a 6SN7 i guess will hand us maybe half of that. Haven´t done the math for that yet... No matter,it´ll suffice and then some.

Preamp then?
Well,the for me common James network is a given. That little stunt that i´ve developed over time is just TO good to leave be. Question thus becomes how many gainstages and of what content?
A 6SJ7 up front,yes Sir. A 6SJ7 setup even conservative will hand us a much wider bandwidth,it´ll hand us an amplification factor a triode can only dream of and what´s more it is indefinte more controllable as far as what we´re asking out of it.

Then...a 6SL7 or an ECC-83? ATM i have to come clean and say...i dunno. Thus far all of the onboard glass is easy to dig up when the time comes for replacement,the most expensive of them being the twin 6L6G tubes IF you want to stick with "old glass" (read-NOS).
If you opt for chinese made replacement...not so much.
Summary of that is that we´ve got economy under control.

That said an ECC-83 install (or several for that matter) is way cheaper and more common then a 6SL7 will ever be. What´s more nothing tells that the amp has to be ALL octals.

Hm.
Decisions

[Racing]

Hm. Yeah.

[Racing]

All is not well in wonderland.

Fired this thing up yesterday albeit just with the 6L6´s in place and... That 6L6,the 6L6G included,takes a whole lot more plate voltage that stated by datasheet i guess is all clear. However,this time out...a little toooooooo much.
Dialed in as far as anode loss in idle the thing settled at approx 520VDC. Then with zeners in place vs g2 that REALLY makes the voltage takes a dive. None the less..520VDC IS to much to ask.

Mind you. These amps,as many others of the time,use what´s known as a pulldown resistor vs B+. This mainly to keep voltage surge during startup in check,while it of course acts as a pulldown under use too.
In the case of these amps a rather hefty 4,7k unit which amounts to,seing the voltages present,that the resistor sees a tad over 40 watts being burned up in heat. That is a shitload no matter how you regard it,and power that could be put to good use elsewhere.

Amp uses a 5U4 stock,and still does,and a 5U4 hands us a rather heavy voltage drop already as is. Few tube rectifiers will present drops all that much more. Ergo,the pulldown in its own right but it DOES impose on those approx 250mA available out of the 5U4.

So. I opted to install a couple of heavy duty ceramic resistors inline with the AC secondary,which sure works. B+ was now all in at approx 470VDC,adjusted to approx 30mA per 6L6G. All good i guess,however...Q is how it´ll make the amp react as i lean into it.
Only one way to find out i guess.....

[Racing]

My old laptop went belly up and it seems the new one ain´t able to "shake hands" with the program that runs my picture server.
Pics are coming tho,rest assured.

Lots has happend. In fact from an electrical perspective the amp is up and running,and thus.... i have settled on a layout.

So.

A 6SJ7 is global and works as an entry stage. In other words that small signal pentode is involved no matter what. Now. From thereon signal is either routed to YET another 6SJ7 or into a couple of triodes of an ECC-83.
This´ll be a first to me when i try to shove a small signal pentode into overdrive by the use of a small signal pentode. Going to be interesting to say the least!

That much for the preamp,and case scenario distortion capability. In short this amp will NOT be a highgain monster but more a rocknroll amp full of a character of its own. Two channel jobbie in other words? Yes. Yes it is,just with a global entry stage.
Of course both sockets for them 6SJ7´s are rubber suspended. Channel select via H11 optos of course.

This is where the signal is headed for the James network,and then in a config you´ve seen me use a lot lately. That rather elaborate one,and reason for this is simple. It works and works very very well.

Outbound it heads for a gainpot that in turn sends the signal for the loop. A loop based on a 6SN7 where it outbound is setup as a cathode follower. This of course to lower output impedance and..a 6SN7 in turn as it can carry loads of current need be. Inbound in turn a regular gainstage,and before being let any further...a 1M Ohm gainpot,which under normal circumstances would be called a master volume buuuuuuut..as i always use a PPIMV control that pot in reality is a gainpot for the phaseinverter.

Now. The phaseinverter i settled for a 6SC7. Mainly as they were there. Never worked with them before but i expect them to behave per normal standards,as far as being a high mu/twin triode octal. The 6SC7 stands out a bit as it uses a common cathode. Hence why it opted to use one as phaseinverter in form of a longtailed pair.

From there in turn...for YET another 6SN7. This time both triodes as cathode followers.....to lower output impedance in a rather dramatic manner before letting the signal hit the PPIMV pot and in turn...head for the control grids of the two 6L6 powertubes.
Complex?
Nah. Not really. It DOES however make good use of half a crapload of tubes though. That much is true.

Gonna be a hoot to see what comes out of the bag. Amp,as noted,is up and running from an electric perspective and i have adjusted the values of the drop resistors of the voltage rail a tad here and there to make voltages dial in approx where i want them.

[Racing]

Time for a more substantial update then.



Yep. As it turned out all them sockets were put to good use. In fact,one was added. Lot of tubes? Yeah,but for a good reason.



Socket description is about on par,apart from the one where a 6SN7 has replaced that 6SC7.



We´ve touched upon the importance of vibrations vs small signal pentodes. Well. This is about as awkward as that has to be. A pair of regular grommets and done deal.



Sure enough. One socket has been added,a noval. This to hold an ECC-83/12AX7



Here we go! A picture is starting to evolve at least. Where the former input jacks used to be we now find the jacks and pots for the loop.



To preserve board space i´ve set anything "cathode" as a point to point bundle and simply run a wire from there to where it needs to go. It is very rare,IME,that you need to replace or service cathode components so..



Uhu. ECC-83.



Might be that that there needs a bit of an explanation.
Yes. There´s all in all 4 coupling caps and these are aimed for use with the PPIMV control.

Try n keep up.
This is in essence a two channel amp. Both channels aimed at rocknroll use. Ie;clean work is of lesser importance. Entry stage for both channels is one of them two 6SJ7´s. After that the signal is headed one of two directions.
Either vs yet another 6SJ7 or vs the twin triodes of that ECC-83 i mention above. The latter i´ve tried many time with VERY good results while the idea of pusing a small signal pentode WITH a small signal pentode is new to me... Previous experiences from this is very limited to me,and the little there is...well,let´s say that the jury has come up hung.
Routing of signal is controlled by H11 optocouplers.

From either preamp the signal then heads for the tonecontrol,which is of the type you´ve seen me fiddle around with lately. Ie; a rather intricate version of the James network. This works SO well that it puts regular stacks and what not to shame so there really is NO excuse not to use it.
Outbound of that James in turn the signal heads for a gainpot,and this gainpot is to control amplitude for the cathode follower triode of a 6SN7,which is the buffer/driver stage for the loop.

Inbound of said loop the signal then hits the other triode of said 6SN7,which is setup as a regular gainstage and heads for yet another gainpot that controls amplitude before signal hits the phaseinverter.
The phaseinverter in turn is a 6SC7,which again is a new acquaintance. Remains to pass judgement on that.

Outbound of the PI the signal then hits the twin triodes of yet another 6SN7,and these are setup as cathode followers...and see this is where the pic above enters as that is one pair of them 4 coupling caps. Signal then heads for the PPIMV pot before being returned and sent on its way vs the powertubes.



In playing around with the drop resistors of the rail and which wire to head where i kind of F-d up a bit and need to clean them bundles of wires up a bit. Comes with the territory i guess.



I guess you can all appreciate the logic behind the loop and how it´s placed.

[Racing]

Humble pie.

So.
I got to start this thing up right. Full of hopes and all of that,and the thing fired up alright. No worries what so ever. However....sounded like a load of crap.
So there i was. Jumping around like a one legged chicken,WTF was going on? Issues with a brand new setup´s one thing,THIS tho?!? WTF?

Checked it all! Tubes fired..all of them. Tossed around wiring and jumpered to left and right just to be able to pinpoint the issue. Nope. No dice. No matter what i did it was there.
At one point i thought i had a bad output transformer even,jumpered another one in there and as that showed the exact same behavior i brough the probes for the scope out. Signal looked like crap! WTF? ALL over.

Started looking into if i had a really die hard tube issue. Most of them are used after all but hey...! They all checked out A ok and better than that even.

Checked railvoltages and what not. It was ALL on the dime. Then i put the guitar cable straight into the loop return and lo n behold...sung like a canary ! Ergo. Had a preamp issue.

Mind you,amp as well behaved as they come. No ills what so ever,apart from it sounding "broken",for lack of better description. What the HELL was going on?!?!?

Concluded that the signal looked like crap right off the bat. Even out of the entry stage 6SJ7,however how would be possible if it WASN´T a bad tube as all components were fresh? So..swapped BOTH 6SJ7´s for others,nope... Crap.

In a state of almost dejection i then brought the DMM out once again for a final round and started measuring around.

Biiiiiiiiiiiiingo!

I had set both them pentodes up with resistor values from memory and see...apart from EF-86,which i use a lot,i believe one of the "other" last ones was an EF-12 right. In other words,220k plate resistor and then a 470k resistor vs g2. All good right?
Wrong.

What that handed me was like 40 surplus VDC vs the screen alright but...6+VDC for the plate,as the 6SJ7...well an EF-12 it is not . Right. That´s not right so out the solderpen came and i just jumpered a 1M resistor in series with that 470k one vs the screen for ease of install and...presto.

An amp that does what it´s told.
This was really late tonight tho so i didn´t get to do the other one,which means that the jury´s still out on pushing a small signal pentode with a small signal pentode. Rest assured though that it´s first thing on the agenda come tomorrow.

Humble pie. You live and learn.

[mackerelmint]

duuuuude. So pretty.

[budda12ax7]

Thread of the year....I don't know half of what you are talking about, but could you work on my amp?? I read this like an adventure novel.

[Racing]

*takes a bow*
Thank you Sirs.

[Racing]

Uhu. Coming full circle i´d say.



As i was to put the bottom lid back on i saw this piece of paper taped in place.



Sure enough! Unfolded was the stock schematic from -46/-48 somewhere! Cool as snot!



Uhu. Still needs a block-off fabbed that´ll keep the channel switch footjack. That and a couple of chicken heads for the controls for the loop.


However.
I got to terms with them two 6SJ7´s right. Goofed around with the amp a bit and found it low on power. That..and it still distored a bit odd. So,took to checking output power and the thing handed me like 20 odd watts or so. That sure as hell ain´t right!
So disconnected the OT entirely and hooked a 12VAC transformer to it to get an idea of turns ratio,did the math and...hooked up like Amroh claims 3800 Ohms primary into an 8 Ohm load i saw like 2000 Ohms..
In other words the thing was arcing.
So much for the Amroh OT sry to say so took to installing a fresh one and...duh! 47 watts with ease out of the pair of old 6L6G´s. Happy camper in short. What´s more i bet there´s more to be had.

So.
What about "a pentode heading into a pentode" then? Well folks...that sure WAS a treat! Or..is! By now i guess you´ve read how the preamp is setup and a mere fact is that this shit works wonders.
The two channels REALLY are apart! I´ll tell ya that much! The pentode channel possess way more attitude,bandwidth and attack. Distortion amounts to about the same (have the way higher amp factors of pentodes in mind here) albeit the pentode channel "just" being two stages.
More treble,more "in your face" in short.

As you can gather amp still isn´t done per se. Gonna toss yet a few hrs worth of tweaks at it,but suffice it for now to say that this little stunt was worth the effort all said n done.
Yep.

[Racing]

Installed 1M Ohm trimpots as so called reostats in series with a 470k resistor to be able to dial idle current (bias) in for the two 6SJ7 small signal pentodes.
Amounted to zip from a practical POW to be honest.

Worked...worked...worked...turned to mush.

Well. Then we know the value of doing that i guess.