Archive for My construction

Iron Pumpkin ; line preamplifier , SE and Balanced iterations

Iron Pumpkin(s) and other smaller vegetable animals

Well , it started long ago …. when I was really young(st)er, full with naivete and BS , came to pretty novel idea to make xformer loaded tube line stage …
Result of first tests , hardly optimal ( using two halves of 6SN7 in parallel and loaded with ancient xformer from vertical section amplifier of ancient B-W tube TV set) , I was blown with ‘till then unknown dimension of sound – everything was so alive ….
Later I made several iterations of line stage with same approach , being so proud for reinventing boiled water , until I got some xerox copies of Sound Practices , where I found that even in boiled water reinventing I wasn’t first ….. boyz from Italia already made Euridice preamp ; anyway , intermediate iteration was with two halves of 6DJ8 in parallel , latest one being with ubiquitous EC8010 and custom made xformer . That being even published on my old site – WOT preamp and battery charger

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Iron Pre

Well ,it started as solution for two customers; both having my Babelfish amps, both driving Dynaudio Contour 1.3 with them.

Whatever solution they had for preamplifier in that time, they weren’t on par with amp quality ….. so logical development of situation is to mate  amps with line stage simple enough but not simpler than necessary …… simply put -preamp made in same manner.

After some chat , consensus was that “plain” buffer (so , no gain ) is adequate,so I decided to make a quick mockup with buffer pcb I had from yore,as part of Poor Serbian Man Lightspeed project.

Frankly – not “plain” buffer anymore , but I simply couldn’t go with less .

Basically-4 separate buffer cells , and simple but witty bipolar (+/-12V) shunt reg on board.Cells are made of scarce and expensive Toshiba JFets (2SJ74BL , 2SK170BL) as source follower. In this case , just two buffer cells are populated, as not needed more for unbalanced operation. For more details, it’s easy to check my signature on .

Schematic sketch and first proto , conveniently put in dreky casset deck case :

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Babelfish J , v2

As any named Babelfish – my iteration of Papa’s gadget .

This one is iteration of Aleph J , v2 means made as adaptive base for making almost entire power range of Aleph amplifiers .

Naturally – JFet input , cascoded to prevent poof from excessive rail voltage , additional Daughter boards for additional output mosfets.

More info here .


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Babelfish J2 , pair of them , for Denmark ……. (Blast from the Past)

Two and half years ago , my fluffy friend Magura asked for sort of favor – wanting me to make two (stereo) Babelfish J2 amps (one of Shameless First Watt Iteration by Mighty ZM )   for his friend , intended for biamping some Gargantuan speakers; after some time , we agreed about parts and everything , and adventure followed …..

They acquired heavy artillery – cases from HiFi2000 , Rifa caps , some heavy NTCs , Semisouth outputs , power On/Off switches , Cardas posts , XLRs , RCAs …. while mains xformers (500VA per stereo case) and pcbs with small parts and few other itsybitsies were mine to complete.

Then entire shebang was smuggled to my (non-EU) country and work begun .

Cases are 5U/400mm deep .


Semi-assembling and first markings for drilling and tapping:

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Big Tannoy Open Baffle fun …… playing with test xover

Continuo from here ;

Still without measurements , just playing with data from various web sources , LTSpice and bunch of parts