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DISCLAIMER: Vacuum tube circuits work with dangerously high voltages. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.

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Thursday, March 27, 2014

ShellacSavor, Part 3 : The Preamplifier

Hi!

The variable EQ preamplifier for reproduction of 78rpm shellac and also vinyl mono records is finished.






I also just got my new Scheu turntable set up with a mono cartridge and 78rpm platter speed to test it.

The preamp has separate controls for Bass Turnover frequency and Treble Roll Off as described in part 2.




The inside of the preamp:





The different EQ networks sit on the right side right behind the faceplate. Signal tubes in the middle and power supply in the back.




I am now enjoying some beautiful 78rpm records. The mono cartridge is brand new and still needs some break in, but the sound from those Shellack discs is already amazing.




I will go more into details about the entire 78 rpm setup in part 4 after adjustment of the turntable and break in of the new cartridge are complete. Some of the EQ settings also need some fine adjustment.

Stay tuned!




Best regards

Thomas

Friday, March 21, 2014

Pure 45 Bliss, Part 2

Hi!

In the first part about the all silver 45/45 amplifiers I showed the assembly. In this part I will show photos of the finished amplifiers and give some sound impressions.





The complete set of 4 chassis consisting of two independent power supplies and two mono amplifiers:










Front view of one of the power amps:






Side views:






The amps in operation:




So how do these silver 45 amps sound? I have reported about the impact of silver in transformers in an earlier post. In these power amps the silver brings the biggest improvement so far. The silver wire transforms these transformers into something new.





The 45/45 amps shown earlier are already stunning performers. But the silver 45 amps caught me by surprise. Especially when equipped with globe tubes the sound becomes frighteningly real. EllaFitzgerald’s Let No Man Write My Epitaph looses it’s vintage character and just sounds ‘there’. The voice is crystal clear and full of emotional impact.




Also modern electronic records are reproduced at a new level. When I listened to my favorite track ‘Scandalous’ on the Faithless album The Dance, I heard sounds which I didn’t hear before. Electronic sounds are projected into space and seem touchable. Every sound has a shape, surface and color.




Especially remarkable are the qualities in the bass department. Lows are extended and extremely well defined showing nuances which I haven’t heard with other amps before.




These amps are like time machines in several ways. No matter how old a recording is they just beam it into the present or put you back there. The combination of the modern silver transformers playing in conjunction with ultra vintage 80+ year old globe tubes brings together the best of the old and new times.




The previously shown 45 amps with Tango transformers are already on a very high sound quality level. But these silver amps are in another league.





Please forgive me if my enthusiasm seems to be getting out of hand. I am usually more reluctant with superlative sound descriptions. But these amps deserve it. Too bad they will be leaving to their new home.


Best regards

Thomas



Tuesday, March 18, 2014

Field Coil Power Supplies

Hi!

Two field coil power supplies just finished:




Both contain two independent supplies for left and right speakers. One will power Kilimanjaro woofers:




And the other will be used for GIP laboratory midrange horn drivers:




The power supplies are passively filtered using Lundahl LL2733 filament chokes. I used my filament transformers to supply the AC. Rectification is done with Schottky diodes.




Some means of adjustment is provided by a set of switches:




The two switches on the right allow aadding or subtracting about 10% by selection of different transformer taps. In addition +/- 5% fine adjustment can be done with the left switches which select different primary taps of the transformers.

Digital LCD displays show voltages and currents for left and right:





Best regards

Thomas



Friday, March 14, 2014

Pure 45 Bliss, Part 1

Hi!

This months posts will be mostly about the 45 triode. I already presented a pair of 45 mono amplifiers earlier and the tube itself got intensive coverage as Tube of the Month. This post is about the 'Pure 45 Bliss' amplifier. This is an amp which uses a 45 to drive a 45. No alternative tubes can be plugged in, no switching. Pure 45 magic.




Part 1 will show the assembly of this pair of monos. As the previously built amps this is a 4 chassis affair. The power supplies have been done in the same design, but the signal section looks a bit different.

This amps use silver transformers throughout! A Lundahl LL7903Ag silver input transformer which provides some extra gain to compensate for the low mu of the 45 as driver. The first 45 is transformer coupled to the output tube through a LL2746Ag and the output transformer is a LL1682Ag. Here a photo of the top plate with the interstage and output transformers mounted along with the oil caps:





The other side showing the improved solder terminals of these transformers:




Unfortunately these beautiful blobs of silver need to be hidden under transformer covers due to the exposed terminals.

All the signal wiring is done with teflon insulated solid core silver wire:




The top platte carries pretty much all the parts and wire through which the signal travels, except the input transformer which is placed inside the chassis.

A close up of the wiring to one of the transformers:




Besides the input transformer, B+ and filament chokes go inside the chassis. Both tubes are DC heated for zero hum operation:




The connection between input jack and input transformer is also done with a twisted pair of the silver wire which runs in the white sleeve from front to back. The there side of the chassis:




Connecting the top plate to the chassis:



Wires between the two parts are mostly filament and power supply wires. The only signal wire between the two is from the input transformer to the driver tube grid and the ground connection to the input transformer.

The power supply is done in a similar fashion as previously shown PSUs. The top plate carries the high voltage transformer, B+ smoothing caps and the rectifier bridge. Here a photo of the prewired PSU plate:



B+ and filament chokes are placed inside the chassis along with the separate filament transformers for driver and output tube:





Stay tuned for part 2 with photos of the finished amps and some sound description of this all silver 45 / 45 amp.




Best regards

Thomas



Thursday, March 13, 2014

Music : Ry Cooder, Paris Texas Soundtrack

Hi!

A great aspect of demoing gear to visitors who come to audition an amplifier or preamplifier is all the different music they bring along. This is a good way to discover records which I was not aware of before. A few weeks ago some nice chaps visited and brought Ry Cooder's Soundtrack of the movie Paris, Texas.





Ry Cooder's score of the Wim Wenders movie is dominated by his atmospheric acoustic guitar play. Mixed with some sound effects and lot's of echo this album is a great journey.

Most of the tracks are instrumental. With the exception of the title 'Cancion Mixteca' which is a beautiful ballad with spanish vocals by Harry Dean Stanton who is an actor in the movie. A very touching song, even though I don't understand spanish. Very different is a track on the second side called 'I knew these people'. This opens with an extensive dialogue from the movie between Stanton ans Kinski which is then complemented by Cooder's guitar and a piano. Very cool track. The record ends with an instrumental guitar track similar to the opening piece. If you liked the movie, this record is a must have. Even if you haven't seen the film the soundtrack is worthwhile to get.





Best regards

Thomas

Saturday, March 8, 2014

Tube of the Month : The 45 (revisited)

Hi!

The 45 has already been covered in a Tube of the Month post. Two sets of mono blocks with the 45 got finished recently and it is one of my all time favourite tubes. So it deserves a revisit. This post will mostly be about the different variants. For all technical aspects about the 45 see the original Tube of the Month post. Now get ready for some 45 porn.





The 45 was introduced in 1929  as UX245. It was very popular as output tube in radio sets and has been manufactured in an abundance of varieties by many manufacturers. Probably the most famous is the RCA:





This is the more modern ST shape, with printed base:







Earlier tubes had engraved bases:




RCA Victor 45 with the Nipper box:




Cunningham made by RCA:




Beautifully engraved base:




Different version:




This heap of RCA Cunningham 45s look the same at first sight:




But some are slightly different in their internal construction:




Many tubes have labels from the stores which sold them:




The earlier Cunningham CX345:








RCA globe shape 45:




The top:




Slightly different version with a little glass piece for adjustment of the electrodes:




The base:





Tung-Sol 45:



Westinghouse:




Different Sylvania 45s:





Sylvania globe UX-245:





Philco, made by Sylvania:




Zentih, probably also made by Sylvania:




General Electric:




Delco:




Fivre 45 made in Italy:







Two australian 45 radio tubes made by Amalgamated Wireless Valve Co:





Arcturus 45 in the beautiful boxes with the observatory motif:




Ken-Rad:




Raytheon:




Majestic G-45:




Two different ST shape Silvertone tubes:




Earlier Silvertone UX-245:






In this tube the getters starts to flake off a little. This can be an indication that somebody tried to reactivate the getter by applying heat through a flame from the outside. It can also came off all by itself. The tube tests fine:




National Union ST shape 45s:





NU produced the 45 over a long time, which is apparent from the changes in styles:




Engraved bases on the older types:





Printed on the later tube:



Also differences in internal construction:





Globe shaped National Union NX-245:





Now let's have a look at the internals of a 45 tube. Don't worry, I wouldn't salvage a good tube for this. This unfortunate Philco 45 got dropped on the floor:






Removing the remaining glass:




Close ups of the top showing the suspension of the filament:




Bottom of the electrodes:




The holder of the getter material:





Removing the plate:




Since the top suspensions got cut off the filament lost it's shape:





Close ups:







Next some odd brand tubes.

The first one is quite peculiar and I only ever came across one of these. A ST shape 45 with  ceramic base:




Not sure if this is genuine and was manufactured like this or if somebody rebased a 45. It bears no brand markings. Could be RCA, here a photo of the top:




Gold Seal 45:




Wards Super Airline:



Globe shaped 45 with Super Airline branding (without the Wards):






This one is shorter then the typical globe 45, here a comparison:




Commander 45:





De Forest 445:






CeCo:





Sonatron 45:




Lafayette:




Hy Ray:




Speed:






Perryman:



Champion:




And finally the most peculiar brand name which I came across: 'OK':





I'd like to finish this post with some 45s in operation:






Here a 45 in a new amp which will be shown in an upcoming post:




Stay tuned!

Best regards

Thomas