Archive for the 'technical department' Category

NRU broadcast mixer


this is a five microphone input – one line level output mixer. made by NRU ( Nederlandse Radio Unie ) netherlands in the early 1960s… i think. it was a super high end specicfication /price unit made for any outside broadcast application of the day.
if in NZ … NZBC concert programme recordings i imagine,
right thru to televised rugby matches.
and ‘ it’s in the bag’.
i saw this on trademe a month back. and surprise ! my tauranga client and friend damian lunson got it. so i get to play with it for a while.


so far it seems like the building block 2 tube amplifiers are the gold. there are 8 of them – mostly the same. except their individual input and output topologies are messed with according to the functionality design. 5 are channel amplifiers with switched input mode and selectible amplifier gain. one is a mixture amplifier. one is an output amplifier. one is an afl (cue function) amplifier.
the thing to do is to reverse engineer a module – draw one out – get it going – see how awesome it sounds. get familiar with the rest – draw out an overall layout – test the theory. and finally decide what the freak to do with it.



inside the cat visconti

the cat visconti gogo prototype channel is completely rocking. but it looks a bit strange.  it is just the  test bed of amps so far. even with its all unshielded looopey connecting wires and floating switches,  the sound is crystal clear and clean of noises or interferences.  the trident tsm 4 way -with filters eq  design is turned backwards and inside out.  now the H.F  has new mojo from coming first on top.  the L.F needed  utter lobotomy. the old chip band pass sweeping eq is changed out for a simple tough and tight 5 freq shelf eq. (neve 1080)  much better bass control with no lumps.

the  all transistor channel amplifiers are on this motherboard along with the jensen input and output trafos (ex of other parts of the trident console) . theres two gain controlled amps in series as the mic/line amp.  the series gain controlled preamps push the signal so long far forward with no noise – effortless big gain.  and then a fader and  post fader amp. theres also  an amp for the extra input section to feed the extra stereo output buss. so many extras. and then one other dual amp board that creates an isolated clean monitor send for a headphones system and a meter . ah. feed the meter. the other mother  (r.h)- board is a stereo twin inverting stage buss amp and control room amps and stereo line buffer amps  designed to be a recording and monitoring unit for andrew’s loungeroom desktop computer set up. more pictures to come.

multiecho hh twins

these twin spunky HH multiechos are NOT having sex. its just so rare that beauties like these could possibly be in the same room. so i just let them play around. and wow. they are good. they are gutted that they just missed out on a threesome! no further sexual innuendo intended. cos i JUST sent MY old HH to jonny boinkin of mank industries in queensland. ive had that  HH for years and years and it has never failed to do the stupid good push button echo-ing thing. ive made a heap of cool sounds with HH and this writhing track is pretty good too.


it features the HH doing multihead switching and regen blurpomatic interrupting stuff.  so HE can make a wild freaking hit LP record from one of his stonking fat songs with his new HH  . if not then i’ll be eating of my BOOT.

grampian 636 spring reverb schematic

heres a drawing of my modified grampian 636. parts of it mite look a bit weird. without delving back into it (where i was for ages already) i can say that it works very sweet. theres several opotunities inside the circuit for gain changing. the mic stage gain control is very strange. i might be wrong about that part.goes well tho. when the gain is low (-) not much mic amp noise gets thru to the next stage.  the board is a messy one. badly planned out on variboard. my one anyway. it was a mission to draw it. all good tho.  note the power supply end.  im not absolutely sure ive drawn that right. i remember having issues when using a centre tapped supply.  i think it went ok when i had two seperate 9v supplies – stacked.  18 volts from ground to hot. and a clean 1/2 of that fed just for the tank driver.  the 2000 uf probably arent even needed if you using batteries? anyway. try some things out. have a think. youll work it out.
also note that this is a positive earth unit.  good luck.any discuss about the circuit is welcome. germanium sounds so good. its all kinds of noisey but so so juicey. wow.

ugliest amplifier ITW nominee

classic! this true beaut 1964 nz made jansen 6 twenty had a party life. until 10 or 30 years ago flooded with a few brandy and cokes . he got left in a really dusty garage all opened up and has attracted all manner of dusty vegetation.  finally given up to the the local hospice shop . where i happened to ride past and noticed it on the footpath.  what a find.  this jansen is perfect to be the new amplifier for a  live rig.    i can  match it to a bin of four collected  rola 12″ speakers. then plug my valve mixture of instruments/fx into the jansen #1 input  and then. crikey  theres a #2  input still .  for another whole thing.  vocal mix or dj or guitarist chain .. anything.  and it has tremelo. woof!  hes up for the ugliest award of course . he  clearly makes it into the disgusting and creepy category too.

up underneath the 300-3U

i love this type of point to point construction , where the back of the valve socket extends backwards  and tags are riveted to that tube up the length of it so as build that particular valve stage right on the valves base. beautiful and simple. at their age these amps have plenty of leaky hi voltage caps. they work and sound good ..  but you can tell they are on the edge of crapping out completely. the leaky coupling caps cause the controls to be extra noisey , also can cause the amp stage plate resistors to burn out , and usually false bias the following stages to the point of almost cut off. the power supply sags and the whole thing goes about 25%.  i’m using french made solen brand parts to repair these amps. ive had only good experience with them. they dont leak d.c at all and are not physically oversized.

ampex 300 oozes dean martin

a client has delivered these ampex machines – ex of capitol studios L.A. – to me -  for to reclaim them up and into a new professional life. first thing has been  to strip them free of their remote control and varispeed switching wireing. to return their control back to personal only. and to bypass the signal tone injectors from the input circuitry. then to clean the decks down careful lube clean up check over electro mechanical features of the tape  transporters.  chunky old school stuff . from another world of engineering long ago long in the past .  the cleaning and clearing has revealed -  one very  munted capstan shaft – one bubbled rubber shot pinch roller – and one scratched up feed idler wheel surface . so far.   braking and control functions seem  good. a bearing bit gummy. so carefullydismantle – clean – lube – refit – quick beer.

i have  to focus now on getting one single stereo machine going all good inside the next two weeks. so the 300 transport deck 1/4″ 2 track with stereo model 300 – 3  octal tube record playback amplifiers. capitol#54 . the total yummy valve tape machine.  it actually oozes dean martin. just today ive swapped out the 60hz capstan motor for my 50 hz spare. so as to get the speed of this master machine as close to an actual 15 inches per second as possible. with that sorted and after a feed idler overhaul  – this transport should be sweet. then to dismantle – recap the amps ,  check thru and prep for full tape recording alignment and greatness.

ekadek is actually saving the planet

my want and need for a few days last week was to dissembowel an AUDIMAX  4440A.  ive appreciated  the quality of the line sound sound of these . they are all transistor. no chips. made well. fat sounding. hi class parts.  made expensive for 1980s FM RADIO broadcast mixer insert and transmitter output stages.  but the dynamics of the thing doesnt have much  to offer a modern studio context. the long hardly changing average level adjusting functionality doesnt fit with any useful requirement that i know of. ok. well just maybe… to keep one thing absolutely the same. huh wtf etc. ( wait a minute. isnt that a whole new music genre?) . anywhoo.. this audimax is kind of made to be an  “AVERAGiNATOR” ….  ..good for making overall levels incredibly hi quality average. sounds  like the eighties to me.

so ive ripped out the “MEMORY UNIT” .  this expoxy potted mystery thing contains live electrical memory that judges how ‘loud’ a track is overall and then compares that knowledge with another sensed and evaluated voltage doubled  judgement of whether the newly adjusted overall level is moving upwards .. or downwards.   brilliant…?  it then makes an external  transistor and fet act against eachother to make that prepostperceived judgement into an overalled averaged representation -  as a dc sucking blowing potential that operates on the balanced patented varilosser signal attenuating circuit . averaging the averaged control signal to make everything extremely average.

so  i was saying..  ive ripped this average brain  right out of the picture. (and fully intend to gore out the epoxy, plunging into that waxy juicyness))  and have transplaced it with an awesome workaround to recreate these puppies into very good working almost brick wall limiting amps. they are way more like a punchy solid state compressor now. still more experiments to do tho.

all without wasting all that energy that originally went into their 1980 manufacture.  just another fine example of how ekadek and its minions works so hard to save the planet. so other news is that IGOR is working up a top secret design for extra sensitive single cycle  transient suppression.  he wants to bring every dominating inth that computer functionality has …back  out of the box and into the sunlight… (cue  manic-al laugh)

revox heaven for swiss dairy cows

i been working on a flood of repairs for the past month plus.  all of a sudden. five revoxes. from three clients. one is a really cool dairy farmer who runs 1/4 inch tapes thru a quad 303 sound system system .. to his cows!  now ive heard everything. maybe it makes the milk better..  Ian  says they love the good sound.

2 beaut G36. the all tube ones. lovely. and so smooth and so wobble free after a good complete inside out clean. they both had transport functional problems. around the motor switches are very inductive loaded circuits which cause hi voltage spikes across the switch contacts. to prevent this reality from causing damage to the switches – big caps with series resistors are wired there. to soak up the spark and discharge the energy slowly. these little SPARK SUCKERS get hot. and leak direct current and then get hotter and short out and burn smoke /smell terrible. blowing  a fuse. they are not easy to replace. awkward. youve pretty much got to take the whole therm o nuclear reactor apart to get behind those particular go switches. there were so many other small operational issues so it was just a case of making it from one to the next and slowly getting to the point where everything is working just as good as it can or was meant to.

next on the couch  was a shiney revox PR99 with logic control issues. a dozen or so tantalum capacitors to change out. holy exploding chassis tho. man. what a hell of thing to take apart.

27 circuit boards all cross wired to the others mounted in 17 different directions. some of them are connected at right angles into a mother board that has un-get-at-able components, links, and switches connected to,and worked directly onto . how did they even do that?  it must have been so hard to make them this way.

next in line was a 2 of revox B77.  and one of A77. they all required a heap of careful cleaning. and completely swapping out the whole  compliment of electrolytic s and tantalum s. shame is that only about 1/3 of them are actually friked . but theres no way of telling that without taking them out. and once they are out … then why would would put the old ones back in. so change them all and it does work out that about 1/3 of them show leaky faults. tell u what .. the overall difference in the sound is definitely worth every penny and if the heads are reasonable the recordings are great.

the A77 is my preference to B77.   the A77 first transistorised machine by revox maybe. but ALL transistor. no chips and definitely the cleanest quietest most brightness blasting sounding electronics.
but the G36 has even more fantastic audio sound of course. i just love valve tape recorders. apart from lp records and needles of course,  and of course ‘being there’ – valve tape recorders are the most analog u can have. the playback signal is completely one new thing . completely fresh extolled up from only nanowebbers of magnetism stored in analog representational waves of aligned-up microscopic iron magnets. and made to line level thru vacummed gaps of space – voltage – and time. dont get me started. anyway the revoxes are foxes. great machines and can be made to go surprisingly well.

i recommend to NOT replay any old tapes more than the ONCE.. it takes to make a copy of said tape. the amount of shed from ageing tapes will only ever increase and dirty up the ol tape path.  time to stock up on new tape stock and more revoxes to re- record all those old radio broadcasts and live to air concerts.

new ekadekatron model

the ultimate & uber non portable 16 channel valve amplifier. after a fair while drilling every holey hole – it took only a day to final construct these 2 basic chassis skeletons. milled & cut & folded 2mm aluminium custom rack mount trays-  32 valve sockets – 16 tag strips – eight threesomes of hi voltage caps -  saddles of input & output connectors – 16 of  MB1  16k/600 output mofo trafos – and  obtusely massive  power connectorators .  this build is well underway now . it was a good day.

ampex story


this machine has taken an age to rebuild and modify. finally it has brand spanking new 1/2″ 2 track heads. thanks jrf magnetics. the recordings are very fat and clear. great to mix with. very kind to transient peak levels. you can drive more sound signal at him. and he never really breaks up … just gets more glued. the playback is awesome. really big and solid. ultimate analogue really …hugh from goldbaby recorded and resampled his TR808 drummer from this machine.

mine was original a three tracker with another channel of course and a simul sync switcher. it had been modified to be a 1/2″ quarter track stereo machine with low impedance heads. i stripped that all away. the top space will be a monitor / headphone / alignment tone box. i want the machine to be kinda self sufficient. much easier to use in the studio.

AMPEX_300.JPGampex photo 1ampex 300 deck photo 2
ampex photo 3ampex photo 4
got rid of all the record and playback eq on the internal bracket chassis. ive put the record monitor level (input monitor) pot there to ease its adjusting. the vu meter has a kill switch too. this means that i can run any kind of input overloading – tape saturation effects – or whatever and can always set the input monitor correct against playback level. u know what i mean. very convenient.

ampex photo 5ampex photo 6

the record eq is now only 1 vari cap mounted right in the record amp.simple and no extra wiring sensitivity noise. same with playback eq. the hi freq set is now mounted direct at the pb amp.

ampex diagram 7ampex diagram 8
ive cut out a whole preamp stage. i go direct in unbalanced (unless im recording mics of course)the heater grounding was noisey crappy angry sounding mess so i fitted hum balance control.
ampex photo 9

this aint pretty but its a picture of my star earth modification.this circuit board design must have been ampex’s first attempt…at circuit board design. and i reckon they got it all wrong. the negative line went kind of like in a chain thru all the different amplifier and filter circuits. frigging mess. so i cut prints and removed the several grounding spots and generally separated all those negative/to be grounded/shields circuits and then star earthed them to a tag fitted just by the playback amp. plain ugly … but hey!. the sound is quite a heap cleaner and fatter. with no hum and ‘hard’ buzzy noises. with a’no input and full! volume playback amp listen’ the (very low) noise is now airey clean and friendly. uite a lot different from the bitchy grubby crackling buzzing that was. the whole machine now sounds so much more fat. really impressive dynamics and is very black. and when you decide to overblow/saturate… it is effortless and large. the electronics doesnt distort. only the tape.heres the ampex virtual museum if you’d like to find out about ampex history.

ghetto blaster from hell

an artist client wanted my old leak 20 system. bad. and ive had it sitting upright whilst fixing the preamp . and ive grown accustomed to the new vibe. the power amp has a custom dual trafo power supply right at the bottom there. and the amp chassis … with the original single power trafo removed … looks like it’s got great big golden balls.  the point one stereo preamp has new bass and treble controls which improved the sound action adjustment effects  hugely of course. no small feat. the bass  is a  5 meg lin dual!  try and buy that from the dairy. i found  5meg board mount pots and some other dual pots by the same manufacturer & swapped out the resistor elements. he has a new balance control circuit too. it attenuates on the input circuit now, rather than the output. the overall sound is much alive with that preamp output loading left off. the wharfdales are my workshop throwaways but you can tell that pumping up some longlegged altecs with extra horn bossoombas is going to rock it. woof!. (i definitely have to get out more)

famous neumann cmv 563 microphone

this is a neumann cmv microphone im fixing up for a client. it came to me all messed around with and not going. somebody had attempted to modify it from its original ec92 amplifier into an ef86 without a clue as to how valves actually work!. the thing could never have gone. they were just guessing. so after some careful brain surgery it goes beautiful now with a nice simple circuit . all new components. but still has a strange spurious noise issue to solve.  the noise only occurs after bassey tones and comes up in the background for about 6 seconds. and then the mic goes perfectly quiet again. what the? so after repeating and checking everything im now resolved that the capsule has a fault. it still sounds great tho as long as you dont heavy breath close up. wouldnt suit darth vader.

plate reverb further up the garden path

new driver
new driver

this strange little thing is a  new reverb plate driver element.  essentially its a speaker magnet and voice coil assembled with a double inverted spider (which holds the voice coil in the magnet gap) and without the normal basket frame and paper/poly speaker cone. a naked motor to vibrate the sprung steel plate.

old broken driver

old broken driver

this is the old blown up dilapidated one. see the handmade brass cone with the little nut retainer on the top … thats the kind of thing i need to make next for the new driver element. shaped from thin brass sheet and soldered.

vortex reverb

vortex reverb

i have two types of pickup device ready to go. a barcus berry hotstuff – hotpoint – hot&hard(?) … and a PZM contact mic. these plates are close now. ive yet to make any driver or pickup amps yet of course. for the get going i’ll use my vortex spring reverb – chassis. its got the right kind of amps to fire up the plate. just for the meantime. im thinking of making the amps into old radios (with internal speakers). so for to allow double life as occassional penthouse apt salon/saloon valve mojo playback unit. or room reverb amp. or office ipod playback amp.

plate reverberation machine

heres some details of my newest obsession. a pair of old plate reverb frames were to either come to me, or left to rust utterly.  they need complete rebuilding. starting with the spring wire tensioner bolt arrangements. they are all rusted and weak. the plate verb sound is all about the plate being tensioned just right. so that the transducers can do their business. ive found some new spring wire and the hardened tags are being made. spring steel needs special tools. guilotines and hi speed diamond drills. i have made new tensioner adjustment bolts myself though. its quite a large project. the plate drivers have to made custom and the pickup devices to be sorted. there are driver amplifiers and pickup amps to make.  and i have to work on them to sell now. or i fear they would probable get chucked out in the way-future for whatever dam reason. so my obsessive compulsive gear junkie tweaking and geeking brain gets another good smacking. i will make some sound tests of the plates once they work. in the meantime please enjoy a smidgen of lulus latest number entitled microphone

six vu meter bridge

today i needed to veer off track to prepare final fitment for the new made meter bridge attachmentisation to the control panel. its gone to the painters now for a transformer grey coating. the meters & the spare are old masters instruments sydney  vus. seventy mm cut out. fast like bullets. its an awesome looking thing. with just right angles and fatness shape.  it looks like a hot rod air scoop. dam expensive.

gogo circuits

these are the new boards for the klangenschmitt gogo model2. there are 16 preamps. 20 post fader amps. 9 virtual ground mix amps. ten single end output amps.  6 floating balanced hi level amps.  and 6 meter amps. its been a busy week and my eyes are completely magnified out.  ive been a freaking factory.  rechecking each circuit for every detail at every component attachment moment   .. and ive just spent the afternoon testing all the amps. and discovered only a couple o faulty circuits . a solder bridge splot and one small piece o wire missing. one completely bad transistor. not freaking bad.


these photos are of the neve ten81 i finished making in june09. believe me it was quite a mission. not only for its complexity but also due to the instructions being incomplete and sometimes incorrect. the ten81 has a mic/line input and an equalizer in four separate frequency sections and a powerful high and low filter section. a truly fabulous sounding tool. a surgical sword and sonic sledgehammer in one.  heres some conversation between my australian client and myself post delivery (he loves it and its his favorite toy) Hi Eke, Well some of the controls are still as deeply lost to my understanding as hieroglyphics– I mean I want to understand it with my right brain ( or is that left?) but my left ( or is that right?) tells me to just go with it and play into it like a saxophone. Between the different clunks and turns seems the ability to do with sounds what I have been wanting to for ages. There is so much right about the sound of this pre/eq that I don’t know where to start. Is it possible to make it sound bad?? How?? Every combination I’ve tired for the last few hours just seems to work. I think I want to just learn to understand it instictively – that my hand reaches for it and with a few turns the lighting on the sound sweeps over the different clefts and niches of the sound.  Dull sources get this kind of beautiful ancient light shone on them.  ( my reply) “hey. so glad you are loving that.  shes a powerful axe and best treated with care tho.. for she will.  as is womanly want .. bite you when you least expect it.  recording too much boosting of frequencies as to shine a sound up sooo much. as then when mixed in with all the other shined up sound morsels. the soup will be all brightened tastes with reduced depth. too many shiney things for anything to shine gently anymore.  delicious miso mixes uncomfortably with ice cream. miss neve is very good at wipeing away a sound into a lovely murky background too . setting the mysterious glorious black back wall of fat black big blackness” Wise words on the soup recipe, chef. the new shining powers it holds might just burn my eye out occasionally. It’s a chainsaw and a scalpel. hilariously powerful and being able to go so far as adding 18db seems like it should bust some law of audio. but it doesn’t. I’m just about to get going on another dive in …  am finding that I have fallen in love with things like acoustic guitar all over again – it just sounds so good through that pre. everything really. I just tuned up the pianos as well to give them a workout on them over the week end. that overdrive is legendary for front end boosting and they pair wonderfully well with the fat ladies as well for maximum girthosity. ah.. they really have kicked me off and I have a few new tunes brewing.”

well .. theres not much as satisfying than a satisfied and inspired client. perfect for me AND a great ad for rupert neve actually . thanks man. you designed a good thing and the challenge of repeating your work was so enlightening and confidence building. thankyou!

mix sessions

i been busy with this album mix of 11 tunes . they all more or less fit into this patched analog set up from an 8 output soundcard (001 for this project). the fat ladys, milli amps, and brian are all limiter amplifiers. klau, ekai, ekat, pev, and astor are equalisers. german is a germanium transistor line amplifier i have. it loves very smooth sounding instruments. seems to give the string parts extra bite! with no added top end. hmmm good ol harmonic distortion. we’ve been well pleased with the results. mixing all the songs thru the similar outboard chains made it so easy to make a great sound for all the songs. and. even tho all the songs feature different musicians and cultural styles, the album doesnt sound chopped up like a  compilation album.look for the PEOPLE IN YOUR NEIGHBOURHOOD record (i’ll link more detail later) and performance at WOMAD.  new plymouth march 13 14 15 .

this is ray the delay (hanging off aux send A) and K-TEE is my Klark Teknik analogue time processor. the Vortex Verb is a valve spring reverb. totally old school.

fatlady twins have left the building

a west australian client Ronan Charles is awaiting delivery of this fine pair of FAT LADY varimu limiting amplifiers. i built these two (and three others) in melbourne 1998. they’ve been in my recording mixing rig since about 2004 and have just received plenty TLC ready for their new situation. of course i got a new set underway, a dual chassis this time (because i have several emptied ones) . heres the design and a panel layout. i have most/all the electronic parts here too. the studio is quite busy coming up to christmas so i got next to no time to make my new twin fatlady.

meanwhile.. back on the w.a ranch… Ronan’s fat ladys arrived fed ex friday afternoon. and his first response . “Seriously – WOOWOO-F-ING-HOOHOO.They are here and blowing my head off! Been running a drum machine as a test for the fast transients and trying all the positions. So much power in these babes – huge huge. Subtle and smooth as well.They blow my drawmer out of the water for depth and range – and pure sex appeal.They seem to love attitude – do lovely things to a distorted signal. Bass is massive – nice and clear if you wanna or dirty it up. so good! Can’t wait to track real drums with them and plug in the moog.” (and the next day) “Just can’t stop playing with ‘em.I’m drunk with sonic pleasure- jeez the distortion is so juicy on NO and especially NO out to GO just sounds amazing.Thanks again for such an inspiring piece of gear with so much to offer.” i cant (dont want to) shut this guy up. heres more enthuising a few days later “Those big juicy dials just help a lot in general exploration and zeroing in what sounds good. I tracked some drums over the weekend to experiment with them a bit more. Found some great bass drum sounds with the NO setting – which of course kinda compresses anyway.  GO is plenty fast and made for snare.  Definitely my new GO-to chain for vox as well. I really love it. what a bloody magnificent beauty. I hope I do them justice. Metering is excellent. I can really see what is going on at the different attack and release speeds. “

venn fender blues deville. two heads in one.

david (venn prod. & karretta) had been playing two blue devilles for a while and wanted to join/control them together somehow. so i made a new plywood cabinet – strapped the amps together – added the stereo controls – added a stereo power soaking line output device. the whole kit sounds fantastic … the speakers sound has improved from not having the chassis in them too. they have rounder fuller tone.. more resonant.