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so , schmtcs are here both Pumpkins ( meaning - what's on electronic pcbs ) are completely compatible to be used as (still MIA) Iron Pre , not yet visible in DiyA Store so , selector - pot - buffer - autoformer ( be it everything SE or Bal) is good and certainly cheaper way , even if definitely few notches down. schematics are proven , so there is one (little more complicated ) possible substitution for Toshiba/LS approach. feel free to try it , on protoboard or PtP , your choice how it sounds ? well - foot-tapping , music is there ..... no thoughts about spectrum dividing , music is simply there and - I'm not responsible for that ( even if Genius) ..... that's simply nature of Good Iron ....... remember M2, F6 , Ultrasimple BAF Sony amp ?

Mda Objavih temu na Big Diya , ali me mrzi da kucam opet na naški, pa cu samo copy/paste kontam ce se snadjete ........... 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

Now , on to Iron Pumpkin (Bal) ; block schematic similar , except few facts : -two buffers per channel -AVC/autoformer connected in differential manner ; again – there is intrinsic SUSY -error correction , whatever you choose to call it . Facts about construction written for SE, applies here also . -One AVC Iron on one pcb , so two pcbs for stereo ; Newest iteration of I. Turtle pcbs optimized for stacking , so footprint stays the same as for SE. -There is option for using any of 5 inputs as SE ; put RCA instead of XLR , mount 1N4148 diode in adequate position for energizing one additional relay and that’s it . Trick is to energize additional relay , to break connection between negative side buffer ( now being without signal ) and negative side of AVC; that way buffer’s output is not acting as virtual zero to negative VAC winding , thus not choking it. AVC is now fed solely through positive side winding , producing ( naturally) output on both sides/phases . So – you can use SE inputs from none to 4 …….. in case that you want all 5 of them being SE inputs , having Bal output …….. then either use SE amp , so choose Iron Pumpkin SE instead , or use Iron Pumpkin with your Bal input amp , but skimp on neg. buffer elements .

After successful realization of concept , I knew that few shortcomings of Iron Pre aren’t in necessity for Preputium made of parts , or Iron choice …… it is in fact of still having resistive attenuator …. and always tempting fact that somehow is possible to dispense scarce Toshibas for something you really can buy in nest Tobacco Store. So ,as a result of my day(night)dreaming, it came to prototyping of Iron Pumpkin , both SE and Bal iteration . Last one simply without suffix, while former obviously having SE as part of name. Due to intrinsic nature of balanced xformer ( fed ballanced , outputting signal also ballanced ) with necessary involvement of GND on either or both sides , it’s also having virtues of SUSY , as Papa patented it years ago. (Old Bull/Devil , always tongue in cheeks ). So , conclusion – to my ears – inductive attenuator is best sounding of all alternatives , and I really succeeded in dream of achieving (settable) gain with same device and , last but not least , natural conversion of SE to Bal , or other way around , in case of Iron Pumpkin (Bal) .

Anyway , what was main quality of (then) newly explored territory for Mighty ZM …. I couldn’t easy describe what that was , and only after few years I came with explanation how I understood it – what I was hearing ( and I hear that even after all these years) is result of important phenomena – Signal Energy Preservation. Simple – with resistive loading – efficiency of stage is always low , while with inductive loading it is way higher …… energy of signal isn’t dissipated along the chain (as with resistor) , it is being transformed in ratio of intrinsic values (voltage , current , thus impedance). Remember that I’m not formally educated in electronics , so I’m pretty much free to invent new postulates whenever I want . During the years , having direct contact with plenty of pro gear (in radio production), I started noticing signal iron in plenty of positions , my Guru discover to me how versatile can be all sorts of so called repeater coils , scavenged from old telephone equipment … To cut (some , not all ) story short – I started collecting all sorts of signal Iron , thinking how one day I should/could/would use them in something ( that behavior is , I believe , familiar to every Greedy Boy around). Besides my (very successful) experiments with xformers as main DAC I/V conversion elements , especially when used fully differential ,and numerous more or less successful attempts to include Iron everywhere in audio chain , I was (not worthy) given by pair of (so called basic ) Intact Audio 200$ AVCs; my own personal German ( known around as Golden Ear-ed Generg ) sent them as Geschenk . They’re ( realized as basic passive box) pretty good sounding , combined with papa’s Koan M2 : AVC & Input Selector for Papa’s Koan M2 ; temporary case ? | Zen Mod Blog So , What is Gain structure > What is Gain Structure? , I’m pretty happy with recippe – efficient and sensitive speakers ( not necessary synonims!) , good amp with power in regular FW bracket , few or none db of gain in box intended ffor selecting and adjusting signal source . However , during the years , playing with all sorts of signal attenuating devices ……resistive (P&G, Noble, TKD, ALPS,all sorts of stepped attenuators,blahblah) , LDR based Dropbox - PSM LS Cook Book.pdf inductive (Intact Audio , Sowter) , I came to conclusion that – besides principle of Signal Energy Preservation , impedances are also very critical , so buffer is conditio sine qua non ….. one step back , but that one step is what is necessary to achieve further two steps in front. It’s not easy to make both cheap and good soundiung buffer ; complementary Toshiba JFet buffer (see PSM LS CookBook) is becoming more and more PITA to make (money not being crucial , but hassle in obtaining them ) , while all other ones are either crude or bulky in comparison . To latest idea about no gain/small gain preamp I came by chance , already written here : What's wrong with the kiss,boy ? and Iron Pre | Zen Mod Blog , so I’m not going to repeat that.

did I forgot something ..... ? obviously - didn't uploaded some pics where applicable

bunch

more of Turtle

Iron Turtle details ....... if you see two Irons (pcb sandwiched in between) that's stereo pack Iron Turtle SE ; if you see one Iron on pcb , that's mono (Balanced) Iron Turtle

more of Bal

few pics

Time for few block schematics ; first Iron Pumpkin SE ( chinch, RCA , whatever) What’s shown are basic blocks – input selector , single buffer ( single phase , yup) fed with Good Gemini shunt reg , then AVC , with selectable input tap ; when fed to top – possible gain is odb , with chooice of tapping in to -2 to -8 db , respectively , so possible gain from 2 to 8db. Selector – simple 5-position rotary switch operating with 5 Takamisawa relays ; they’re good for industrial and medical instruments , so …. Good Gemini – simplified but also hot-rodded iteration of well known Shunty. Buffer – current mirror biased Diamond Buffer …… nothing new , but painstakingly to achieve same THD spectra as with Toshibas , luckily with even beter behavior under heavier loads. AVC – called Iron Turtle SE ,based on Toshiba Metglas (AMCC008) cores. Coil – 10H/100Rdc jobbie , as (always!!) compromise between needed Good Inductivity and several Bad Factors (known as Bad Capacitances , Bad Inductivity etc. …. in fact , using AVC instead of TVC is Bad Inductivity non existent ); insulation between layers is Teflon based , bobbins are/will be custom ones , everything PVC coated after assembly. Disclaimer – as for difference to almost all AVCs on market , these aren't intended to be Swiss Knife universal jobbies , they are constructed to be driven with buffer or , at least , pretty potent signal source apparatus. Two AVC Irons on one Iron Turtle pcb , so that’s enough for stereo. Switching again through Takamisawa relays ; flat cable going from Turtle pcb to front plate mounted 24 position Chinese Switch . Chinese Switch – even if made by carefully chosen group of Chinese Virgins , only during full moon nights , each one is gladly disassembled then greased with graphite grease then assembled again , by Mighty ZM himself.

m..pa da ...... elem gotovo i sa bal modulom ....... dakle sve je gotovo - sastavljeno i isprobano sad da se pripremi dokumentacija , otvoriza proper tema i da se objave seme i slike

Malo kasnim, evo nekih fotki od juce i prekjuce :). Tiplovanje trajalo celo popodne, tri operacije povaditi zalepljene srafove, razbusivanje rupa, lepljenje i zakivanje tiplova smirglanje...

Poceo pre neki dan da pravim kabinete za RCA LC1 drivere. 4 kabineta. Prebacio isecene komade. Ovo su fotke od pre nekoliko dana. Bice i novijih. Nabavio sam neki dobar sper od topole. Isto kako na jednom paru kabineta koji sam pravio ranije. Odgovarale su mi i dimenzije ploca koje su bile na raspolaganju. Potrebno je 4 ploce 252 x 187 cm. Materijal nabavljen u Drvopromet kula, na pancevackom putu. Sve sam to uspeo da spakujem u automobil (nesto i na paktreger) i sa sve isijasom, natovarim, prevezem i isovarim... Polako secem i izradjujem elemente pre leplenje i slapanja. Link za dimenzije i nacrt kabineta imate ovde:

https://img-9gag-fun.9cache.com/photo/aGey8WZ_460sv.mp4

Kao onaj bazen za tržište Saudi Arabie. Ili Staljinov fotošop. Gde ga je Malčenko??

^ Very impressive speech! It is filled with deep knowledge - from mathematics to marketing. Thank you very much, I even realized that myself I is made in the wrong way!

And how Your design look a like? Is there any sense, relationships, or it is totaly arbitary without any design at all? At least they, slovenans, dont hide natural, true wood. Tremendous amount of handy work does not guaranties the well soud. The goal is to impress the potential buyer at the first second and sell as soon as possible. Your "design" is wrong, your measurements with a water is wrong, that is not the real volume drivers deserves. with these numerous chambers you divide total volumes into milion small chambers. every one have own center of mass. these center of masses are farr from each other and form much smaller volume driver can see than measure simple volume. But You are unable to understand this. That is all try to find on this forum measurements and resuls that one member did with and without chambers. He cut out "bracing" and report.... cheers

Ne vidim zasto smeta da se nazire i spolja poznata konstrukcija... . A mislim da se nema potrebe ni prikrivati prirodne materijale. To se radi sa ivericomi i medijapanom... Ima jos jedna stvar imao sam samo 3 elektricne masine ubodnu pilu i busilicu. Kao i odvrtac na baterije. Keksericu me mrzelo da kupujem za 2 kabineta u 5 godina... Nisam imao ni stege. Mogao sam pozajmiti dugacke stege ali mrzelo me je da pranosim vecu kolicinu stega posto su 4 kabineta u pitanju. I poterbno je uraditi operciju u jednom danu a ne razvlaciti sto godina...

Da to moze kada je drvo tvrdje od tipla. Pa onda smirglanjem poravna. I to je super ako je potrebno da se zameni daska i da se odstafi sraf ispod tog tipla. Medjutoa ovde je sperka mekana a tipl tvrdji. Probao sam sve. ovo mi je najbolje i najbrze. Nema nikakvog smirglanja, sve legne na 0...

Relax , there is a lot of work still on the stand! Similar was the situation with the bases of the central pillars;

Mozda ovako da je deblja noga kao slovenci sto rade...

procedura za tiplovanje: tipl se namaze malo manje od polovine lepkom, tanak sloj. Najbolje ga je rolati po lepku. Ova piljevina od razbusivanja rupa se ne cisti. tipl se skuca ravnim cekicem ili izmedju cekica i tipla tvrdo ravno parce drveta. zakuca se do linije spera. Visak lepka se pokupi piljevinom. posle ide blago smirglanje. Sve bude idealno ravno. Sipke tiplova se veoma jako spoje trakom u cvrsti snop. obelezi se duzina i napravi prsten od kartona koji se pomera. Onda se sece ubodnom testerom po ivici kartona. Jako precizno se iseku tiplovi na ovaj nacin... Neuporedivo bolje deluje ngo srafovi ili gitovane rupe, a u ovom slucaju je povrsina sperke jako ravna i nije uopste cupava, pa se ne mora uopste mnogo smirglati. Mislim da nema potrebe furnirati.

Evo jos malo fotografija. Upornice isrezane i napasovane. Sledi lepljenje.

Izdrzala bi ali je ovako manje elemenata i montaze. Samo se lepo izreze, posto se sklopi ceo kabinet

Da, pa nije moguce montirati sa unutrasnje strane nista kada se kabineti zalepe...

Port ide na plocu, to je ista ona izrazana za ARU480 jedinice i to je ploca 37x25cm. Tako da moze i da se izmeni. Driveri su na sopstvenim nosecim plocama pa se samo ubace u leziste. Sve je zamenjlivo.

Nista bez sablona... Evo jos malo fotografija. Zavrsio skoro sve pojedinacne elemente sa sva 4 kabineta. Ostavio sam mogucnost da se doda Acousticaly Resistance Unit. (Samo ovaj ARU je veci za 15ina driver 37 x 25cm). Posto se u praksi pokazala izuzetno dobro. Umesto porta koji ce ici kao prva verzija, samo se promeni nosac porta... Sklopio sam 2 komada, bez leplenja, tek da vidim kako pasuju elementi. I sve je OK Sklopicu i zasrafiti sva 4 pa onda jednu po jednu stranicu odsrafljivati i lepiti.

evo nekoliko svezijih fotografija. Za veci broj komada koji se ponavljaju, neophodna je upotreba sablona. Drasticno skracuje vreme operacije, i povecava preciznost.