Currawong

the thermionic watercooler

Currawong

Postby soundbrigade » Thu Sep 03, 2015 7:46 am

Time for a new (yet another project) project ...

The ....

Image






... Currawong according to a design found in the Australian journal Silicon Chip. Info with pictures to follow.
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby soundbrigade » Thu Sep 03, 2015 8:29 am

s OK, the Australian journal Silicon Chip isn't known as a friend of electrons swimming freely in vacuum, but a few tube projects have been published among them a simple preamp (12AX7), a very strange PF-amp and this Currawong 10W 6L6 pushpull amp.
10W!!!!??? with 6L6??!!!

Well reading the articles it's understood that the Aussies goes for a budget version using cheap (dirt cheap) 15W 100V line transformers and cheap all-purpose mains transformers. The amp is built on a BIG single PCB (I tend to like that).
Four 6L6 and four 12AX7 are needed for the amp and of course the usual suspects of Rs and Cs. And LEDs (blue!) and ICs and transistors. The silicon stuff ais used as turn on delays, automatic headphone/speaker switching.

Here's the PCB
Currawong_01.jpg
Currawong PCB
Currawong_01.jpg (197.45 KiB) Viewed 7023 times


here are some hard-to-find components I also ordered
Currawong_02.jpg
Currawong - hardtofindstuff
Currawong_02.jpg (49.75 KiB) Viewed 7023 times


Schematic? Well, in this case I ask you simple to wait until someone has let it out on the web. The articles are protected ( :/ ) by copyright and I prefer not to show you. Hope you can live with that.
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby soundbrigade » Thu Sep 03, 2015 8:30 am

One more thing, Currawong is the name of the amplifier AND the bird. I mean, what the bird in the pic is named or called I don't know, maybe Charles or Bertram or Biswanath. I just meant the species are called Currawong. The same goes for the amp - that kind of breed is called Currawong, but I would prefer name it according to my standard - Russian cities.
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby soundbrigade » Thu Sep 03, 2015 1:58 pm

Well, a few more bones for the dogs:

I have to mention that I started to dig into my boxes of assorted components, hoping to use up stuff I else wouldn't. What's left was to order from local shops.

Transformers use, as I wrote earlier were cheap transformers used in totally different applications and I really wanted to use cheap but dedicated iron (read Edcor). After some consideration, a few mails to the journal's technical advisor and reading a follow-up article in wwhich the cheap Altronic's transformers were compared to Hamamatsu-something $1000 transformersI decied to go with the Altronic's: M1115.
Mains transformer is a universal kind with several windings that are added to 116V and then run through a voltage doubler. I decided to order a special made toroid from Germany - that will be the project's most expensive part.

God, I should order some more of the Altronic X-formers. They could be useful in other projects where smaller tubes are used ...

I should add that I will not rush this project (but the PCB is already almost fully populated). The ieda was to add componets and parts littel by little but apart from some PCB connectors and a quadruple 470n/630V capacitors (I made a mistake when I order them and ordered TWO instead of FIVE =:o ). I also miss a box to house the amp but I had two ideas. One wwas to use some golden sheet metal lying at my job, but that was thrown out before I said STOP. Another is to use a wooden box, either made to the measurments in the original article, or make something personal.
This is the original design:
Image

Finally a word on PCBs. I prefer point-to-pint technique when wiring tube amps, but in this case I found it very handy to use the board to see how the project advances, what is needed for the next step (missing components) and most of all the board makes a good base. When everything's in place, I just hook up the mains transformer to test that everything is working.
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby EWBrown » Thu Sep 03, 2015 6:17 pm

My all-time favorite Russian City name is Magnitogorsk / Магнитогорск .

Perhaps an all-tubes version of the Currawong, minus all of the ICs, and flashy blue blinky LEDs, point to point hand wired, would earn the right to be named after
this mystical city of secretive Soviet-era technology.

I see that five blue LEDs are included, and one is used for the power-on light. That would probably mean that the other four are employed
for the extremely vital task of underlighting the four 12AX7s, and with the CMOS IC and four transistors located in the right front corner (???)
they probably blink annoyingly from left to right, continuously :'( =:o

With 12AX7s for the drivers and LTPIs, feeding the 6L6s, this design should have fairly standardized PP amp circuitry. [:)

Of course, in order to qualify for the title of Магнитогорск it should use all Russian made tubes, 6N2Ps and 6P3Ss O:)
Last edited by EWBrown on Wed Sep 16, 2015 7:09 pm, edited 1 time in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Re: Currawong

Postby Geek » Thu Sep 03, 2015 11:41 pm

Very cool, Magnus! (y)
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: Currawong

Postby soundbrigade » Fri Sep 04, 2015 12:48 am

My black-and-black 12A6 amp is named Karaganda and my two-tube 5998A Omsk. The other (in the project line) 5998A amp using three tubes must be Tomsk. (b)

On the Halbleiters (semiconductors in European): B+ is regulated, hence the many transistors and a powerFET. The IC (CD4093) and some transistors make up a softstart, a LM317 regulates Vheater for the 12AX7 and some more transistors automatically switches the headphone relays.

The amp is made up by two 12AX7 anode followers, all feedbacked pretty much. Another 12AX7 makes up a LTPI. The 6L6 are propably run very conservative to keep power low. Output transformers are rated just 15W. Floating biased is used - anode current is approx 67mA.

I couldn't really understand the idea of the blue leds, placed on the board next to the transformers, but see now that they together with a resistor acts as bleeders to the PSU caps. The power LED is a red/green one. I wonder when it will glow green and when it will glow red. (???)

Else, I must say the much of the ciruitry looks a lot like what is found in the Dutch journal Elektor Electronics, where a two-tube amp is supported by three PCBs filled with digital circuitry and some Arduinos to take care of switching ins and outs ... I just have to live with it. It may be cool also. :|

The material is available online, though the paper magz can be ordered separately. The online articles are in some Flash-format and rendering takes TIME. If you're on a copper line with a 32kbaud modem - forget it. :'(

http://www.siliconchip.com.au/Issue/2014/October/Currawong+Stereo+Valve+Amplifier%3A+A+Preview
http://www.siliconchip.com.au/Issue/2014/November/Currawong+2+x+10W+Stereo+Valve+Amplifier,+Pt.1
http://www.siliconchip.com.au/Issue/2014/December/Currawong+2+x+10W+Stereo+Valve+Amplifier,+Pt.2
http://www.siliconchip.com.au/Issue/2015/January/The+Currawong+2+x+10W+Stereo+Valve+Amplifier,+Pt.3
http://www.siliconchip.com.au/Issue/2015/March/Modifying+the+Currawong+Amplifier%3A+Is+It+Worthwhile%3F

http://www.siliconchip.com.au/Shop/8/2884
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby soundbrigade » Sat Sep 05, 2015 7:35 am

Some more pick-tures.

There is/was plans from the designer to use a motorpot with a self-designed remote controller. However I have several such controllers and driver modules and, of course use my own stuff. Some boards from Chian came without potentiometer or relays so I simply bought a pack of motorized potentiometers from a small Swedish company, paying some USD5 each.
However I disassempled a board with a potentiometr before I discovered my mistake - the potentiometer is attached underneath the board. Smart move, Magnus! :/

currawong_04.jpg
currawong_04.jpg (56.52 KiB) Viewed 6938 times


That MUCH better! (y)

currawong_06.jpg
currawong_06.jpg (83.83 KiB) Viewed 6938 times


Here's the smallish driver board.

currawong_07.jpg
currawong_07.jpg (420.31 KiB) Viewed 6938 times
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby Geek » Sat Sep 05, 2015 11:31 am

Oops! =:o

I think all us old tech's sill make the odd "oops" like that :$
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: Currawong

Postby soundbrigade » Sat Sep 05, 2015 2:28 pm

There's is one BIG oops more to come. It's about the choice of tube sockets. I have always looked at sockets and how the tabs with screw holes for mounting as something carved in stone. The mounting holes in an octal socket is between pins 1 & 8 and 4 & 5. An for noval sockets between 1 &9 and opposite pin 5.

Well, have a look at this:
currawong_03.jpg
currawong_03.jpg (67.62 KiB) Viewed 6927 times


(???) =:o (sick)
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby Geek » Sun Sep 06, 2015 2:47 am

Chianese sockets? (???)
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: Currawong

Postby soundbrigade » Sun Sep 06, 2015 5:43 am

A picture says more than a lot of words ...

currawong_10.jpg
currawong_10.jpg (103.09 KiB) Viewed 6909 times


When looking at the pic now I suddenly become so very confused. Maybe I am simply stupid?? (???) Now I am not! Just checked. There are this kind of sockets (from Russia and propably from Chian too) with a ceramic socket and a loose retainer that can be shifted 90 degrees. Like this one:
https://www.tubesandmore.com/products/P-ST8-801

Image
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Re: Currawong

Postby EWBrown » Sun Sep 06, 2015 1:37 pm

If you examine the PC board closely, the octal mounting rings are connected to circuit etches, (possibly these are connected to signal / power ground? ) maybe their intent is to use sockets without these mounting rings. Also check the orientation, they appear to be one 45 degree "click" off axis (???)

Image

I'd use this kind of socket, but without the mounting ring(s).

Image

Also, double check the PC board to ensure that the octal socket "keys" and pin-numbering silkscreens are properly oriented .

Apparently the Russo-Chinese type octal sockets are the way to go, according to this pic on the Alltronics webpage:


Expand picture to full size for maximum clarity O:)

Image

/ed B
Last edited by EWBrown on Wed Sep 16, 2015 7:14 pm, edited 3 times in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Re: Currawong

Postby EWBrown » Sun Sep 06, 2015 1:56 pm

Image
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Re: Currawong

Postby soundbrigade » Sun Sep 06, 2015 2:21 pm

@Mr Brown: I will have a look at that, but it may also be that the sockets used for this project are of different design. Where's the parts list ...???

Here it is! This is the socket used: http://www.altronics.com.au/p/p8501-el34-8-pin-shielded-ceramic-socket/
Magnus

"It is always more difficult to fight against faith than against knowledge."
User avatar
soundbrigade
KT88
 
Posts: 1758
Joined: Mon Jan 28, 2008 4:57 am
Location: Little Paris, Sweden

Next

Return to diy hifi

Who is online

Users browsing this forum: No registered users and 2 guests