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Old 17th Jan 2016, 4:13 pm   #81
Lucien Nunes
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

If I get off work at a sensible time tonight I'll write up the final episode, but in the meantime I have just more or less consented to it going on another outing. This means we might have some better video. It also means it has to continue working. Hmmm.
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Old 23rd Jan 2016, 7:53 pm   #82
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

The final instalment was getting rather long - it's become two...

Show day PM, cont'd.

Once the crew had helped to stand the generator rack upright and position the console on the stage, I started connecting up. Console and rack plugged together and to the mains, temporary heater PSU for the 6.3 volt valves and there was audio in the headphones. Next job was to tie in to the PA, so I went up to the desk and said hello to the sound engineer. Having once worked full-time in live audio, spending many happy hours behind last generation analogue desks (I moved into a different sphere of work just as the need to lug Yamaha PM3500s up the FOH stairs came to an end), it always feels odd asking someone else to line me up some inputs, instead of the other way round. The crew were really efficient and helpful; even while we were nudging things into place they had run main and backup DI boxes out from the stage-box ready to plug in the preamp output cable. Let's have a listen...

MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM!

Nasty hum. Controllable by the swell pedal therefore generated before the final stage, i.e. not obviously to do with the hookup to the DI box which was the only new factor. Also, quite pure 50Hz, so not HT ripple, stray pickup or open-circuited preamp / pickup loops. I couldn't resist checking that it wasn't bottom G of the flute stuck on! Considering it likely it to be heater related, I had a twiddle of the humbucker pots two of which made it a bit worse, so k-h fault(s) which had caused trouble before seemed a reasonable explanation. The sound man offered to notch it out for the moment so we could put the problem on the back burner pending a sweep of all oscillators during note testing and tuning. With the hum partially suppressed, we also heard a high frequency tone that seemed to be coupled in from elsewhere as it remained even with the oscillator HT supplies off. Likewise, we left it for later, expecting it to change with the lighting state or some external factor that would help us locate the source. A quick blast on the console proved that we had good gain and EQ settings, the 16' pedal tones really shaking the venue and the quiter voices coming over nicely too. Then the sound crew had to move on to other things, we had a quick production meeting, then I was back to my headphones.

It was now around 3.30pm; I had been working non-stop for 31 hours. We had two out of four ranks tunable (and still reasonably in tune, only a few coils had been knocked on the journey) but two still awaiting capacitors. We already had hum and whine, now we had competition. The dance rehearsals began in earnest, complete with ear-splitting vogue / house music. This was the reasoning behind the fullrange PA that we would later be using to good effect, but for now it was a problem. How would I tune? Luckily I had good heaphones and a good monitor amp to drive them. I put in earplugs (to reduce the overall SPL) and clamped the cans round my head with gaffer tape, cushions compressed as tightly as possible. With the amp turned right up I could hear the tones fairly well and began tuning. From now on, any spare moment was used this way. Two HT clipleads and torch in hand, I went over the Diapason and Flute before making inroads into the uncharted areas of the String / Trumpet, heterodyne beat accompanied by the insistent drum-beat of the dance music as well as the ever-present background hum.

MMMMMMMMMMMMMMMMMMMM.... BOOM, BOOM, BOOM, BOOM, BOOM, wahwahwahwah, BOOM, waaahwaaahwaaah, BOOM, waaaaaahwaaaaaah, BOOM, Waaaaaaaaaaaaa, BOOM, move the clipleads, BOOM, BOOM, BOOM, brbrbrbrbrbrbr, BOOM, this one needs its cap changed, BOOM....

Pleasantly, there were few capacitors needing replacement this time around, so by the time David the organist arrived, there was a steady cycle of tuning and checking and almost three playable ranks. After getting most of rank 3 right, I peeled the cans off my head and asked for some rehearsal time when the dancers went for a break. Soon enough, the whole place went eerily quiet, then up came the organ channel complete with hum for David to try a few registrations and pieces. 'That's not bad at all' he said. They had a quick conflab about styles and order and crashed through the intro a couple of times with the stage manager. Relieved of the other audible distractions, the sound engineer and I agreed that it was becoming increasingly important to cure the hum. Once David had explored the instrument and given a thumbs-up, while we still had some peace I tried disconnecting all the voicing filters from the preamp, which by itself was reassuringly quiet even with the wick turned up at the PA desk. Reconnecting ranks in turn revealed each one to be contributing some of the hum, yet their completely independent HT and heater supplies made it almost impossible for one fault to affect them all, other than maybe a lost shared ground. The other possibility was that there were multiple identical faults, not very likely either, but one has to begin somewhere. With only the Diapason connected I went on an octave-by-octave search for the source of the 50Hz.

As time went on with nothing gleaned, an old reflex kicked in from my live event days: If you haven't devised a workaround by the time the waiting staff have their briefing, you're in trouble.

TBC - sorry it's another cliffhanger.
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Old 23rd Jan 2016, 8:33 pm   #83
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

OMG, I really can't stand this...... ;-)
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Old 23rd Jan 2016, 11:23 pm   #84
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Red face Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Parallel earths / ground loop........? Come on, Lucien - spill the beans!



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Old 24th Jan 2016, 12:10 am   #85
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

This realisation prompted a strategic break with phones off, to depolarise the thinking chemicals like a Leclanché cell resting after heavy discharge. After grabbing a can of drink, I found Eloise; we shared our hopes and fears (other people were apparently having technical snags too!), returning to our respective tasks somewhat refreshed 10 minutes later. While re-jigging the test leads, something caught my eye; the 6.3V supply leads trailing from one of the filter panels down to the floor. You'll remember my quick fix for a lack of usable 12SN7s when first firing up the generators at the workshop - I put in good 6SN7s and reconnected the appropriate heater leads to an external supply. It was a regulated DC bench PSU that I trusted, there was no particular reason to think it had hum on its output - it didn't when testing back at base - even if it did it would probably be 100Hz and in any case the heaters ought to be able to work perfectly well on AC. But I could not deny that it formed a circuit common to all ranks prior to the swell light gate, which I had forgotten about because under normal conditions all supplies for each filter chassis are derived from their associated oscillator ranks.

When rigging at the venue, I had tied one side to ground with a clip-lead from valve base to HT -ve, so I checked this lead was still in place which it was. This was not exactly how it had been at the workshop - the cliplead had connected the PSU terminal to the main power chassis star point - although it was difficult to see how the position of the lead could make a difference. The connection was needed because the PSU has a floating output, thus it could not have caused an earth loop and should only have been carrying minute DC leakage currents, but reverting to the original configuration seemed worth a try. I temporarily grounded the output stage, removed the cliplead from the filter chassis, poked an extra wire in the PSU socket and hooked it round a fixing screw in the cabinet. Unmuting the output, the hum was gone (almost, as I had left the humbucking pots maladjusted but this was soon corrected). Racing excitedly back to the control position I asked the sound engineer to get rid of the notch filter and give it some welly. The whine was still there faintly in the background (we never did find its source) but we had glorious hum-free music.

[After the event I proved that the PSU DC output, although well regulated and free of ripple, rides on quite a hefty common-mode AC voltage at 50Hz due to the layout of the internal wiring. There had been no metallic earth loop but the relatively high stray admittance of the connected parts had resulted in enough current in the signal grounds to couple into the audio circuit. I am still surprised how severe the effect was.]

The dancers returned for their final rehearsal, I strapped on my cans, had a quick tweak of a few iffy contacts in the matrix relay, swapped a suspect ECC82 and carried on tuning until 10 seconds before the opening fanfare. Still not having enough of the Twelfth in tune to make it usable throughout the compass, David simply avoided it altogether. I lurked behind the generator cabinet just out of sight, armed with meter and hot iron, but the rest of the instrument remained spot-on throughout the evening of tuneful tunes - we had vintage pops, novelties, selections from musicals - until the dance performance finally obliterated my hearing altogether and brought us to a close.

By the time the last guest left and the organ power was off, I had been working non-stop for just under 40 hours. It was only 127 hours since the generator rack left the church.
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Old 24th Jan 2016, 12:42 am   #86
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Amazing

Don't know what else to say

Cheers

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Old 24th Jan 2016, 12:47 am   #87
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Pheeewww!

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Old 24th Jan 2016, 1:27 am   #88
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

I'm left recalling days of supporting a mid-engined rally car out in the field and swapping a gearbox by the side of a wet road in 30 minutes, that would take a day in a normal workshop. At least Lucien wasn't working in the rain. "You've no quint or nazard, but we'll get those at the next service halt..."

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Old 24th Jan 2016, 1:31 am   #89
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

I couldn't take many pics of the show from my hidey-hole behind the generators but take a peek at some nice coverage by Dan Weill:
Pics of ICA Gala by Dan Weill Photography
Valvey and bulby things are not much in evidence here but if you look carefully at the programmes on the set table you'll see a picture of a mercury-arc rectifier on the front cover.

I'll try to edit something vaguely watchable from my mobile phone video clips when time permits.

Credits:

Campbell: Starting the whole process to prevent the organ being scrapped.
Bill (AC/HL): Making the initial connection and putting us in touch.
Mary: Negotiating, facilitating, cajoling, recruiting, lift'n'shifting and providing essential sausage rolls.
David: Finesse, efficiency, Herculean strength and not dropping it on my fingers.
Removal crew: Working as a tight team in an even tighter stairwell.
Petrina: Official record of the removal. The extracts and downscales of her pics in this thread don't do them justice.
Dan: Being in the right places at the right times, cheerfully cracking on while putting up with Eloise and me.
Beth: Having faith in our scheme and making the show fun.
David: Remaining 100% calm and knocking out some great tunes.
Eloise: Don't do it again!
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Old 24th Jan 2016, 1:40 am   #90
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Thanks Lucien for a very interesting and entertaining thread.
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Old 24th Jan 2016, 2:29 am   #91
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

You might be intrigued to watch this video of a related organo-visual performance by Eloise, using a Compton Melotone (the original cinema-organ add-in from the mid 1930s using electrostatic generators, explanation here: Melotone)

Those eerie echoing tones are being played live by Peter, generated by spinning discs inside the oscillating circular bakelite housings on the upright metal chassis and issuing from the Vitavox dual-driver horn speaker on the floor. Valve line-up behind the three chrome bars includes a pair of DA30s. Unusual place to find a pair of big prewar audio triodes, no? More on this soon.

Er and Other Conductors - Eloise Hawser & Kara Mensah
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Old 24th Jan 2016, 8:19 am   #92
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

I'm speechless. Wow!
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Old 24th Jan 2016, 8:30 am   #93
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

I think I found the image:

https://www.ica.org.uk/join-support/ica-gala/2015

If that doesn't work, google ICA Gala and click on 2015.
I wonder how many people thought that glassware was an arty piece in homage to c'thulhu?

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Old 24th Jan 2016, 12:02 pm   #94
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Good job it doesn't have eight legs though its contents are fairly poisonous anyway
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Old 26th Jan 2016, 12:17 pm   #95
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Hi Lucien
extremely good and entertaining write up and well done for saving it.
May I ask a question? As an ex organ pipe voicer I can remember when voicing 16ft and 32ft pipes that you can walk into and out of the standing waves,thus the sound getting louder and quieter as you do so,made by those pipes. Does the effect happen with the electronic version too?
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Old 26th Jan 2016, 12:54 pm   #96
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Absolutely incredible, Lucien. Your exploits would make a fantastic book.

What next for the organ? And for your next project?

Nick.
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Old 26th Jan 2016, 1:44 pm   #97
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Brilliant write-up Lucien, and congratulations to you and the team for achieving what many would have deemed impossible given the timescale.

Keeping one of these organs working is akin to maintaining a steam locomotive - financially unsustainable without skilled and willing volunteers!
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Old 26th Jan 2016, 2:18 pm   #98
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Brilliant Lucien, would you do another?
My father is a church organist, now retired, he has said that he could get a 32' 'feel' by mixing two 16' stops a certain tone apart thus generating a difference frequency.Do that make sense? Can this be done with an electronic organ?

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Old 26th Jan 2016, 2:49 pm   #99
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Thank you to everyone for all the positive comments and encouragements - it seemed like an ideal candidate for a fuller write-up because nearly everyone on this forum will be familiar with the technology. I'm going to try doing some similar blow-by-blow accounts of the more industrial stuff on our own forum as power station control panels and the like don't really fit in here, but anything TV/Video/Audio/Radio will air on this forum. TBH we're not big in radio collecting yet because such a good job has been made of that already... there will come a time when we have to catch up! I am also being urged to do some project reports in video format on YouTube but as always it's limited by available time.

What's next for the Miller? I would like to say it is taking up its final position in the display but Eloise will be showing it and the Melotone at an event at the White Cube gallery next week, details TBC. You can come and see/hear it in real life although I am not sure exactly what kind of music will be played on it!

Next project? Shelves! The Miller was fast-tracked because it was a commissioned project, otherwise it would simply be in the queue of things to set up at Electrokinetica. We've still not wrapped up the CP TX project yet, in fact that, the Miller and finishing the control panel recovery from Littlebrook were the highlights of last year. We urgently need to make make inroads into displays, there's 14 rooms and a hundred tons of stuff but it's all boxed up so not much of an exhibition. We've dozens of electric kettles going back to the very dawn of electric kettles, but the only one I can actually show you is the modern one we use to make tea in the messroom! 2016 is the year of the shelf; if Dave and I could do nothing more than put up 100 feet a day for two days a month we'd be delighted. Eloise is probably not going to settle for that and will be taking open-day bull by the horns this summer, the same open day that I have been not getting around to for the last few years. The timeline for that includes 'Make bits of analogue computer work so it looks exciting' and my old nemesis 'Erect Theatre' that we started on once and then had to move due to unexpected expansion. There is nothing in the world that I am looking forward to more than welcoming intrepid visitors to browse our kettle-filled theatre or wherever we've got to when the doors open.

Steve - yes, the standing waves behave in the same way, as they are dominated by the room resonances. Historically one of the selling points of the better electronics was that individual notes could be voiced in-situ to account for such acoustical variations. Some of our organs can do this, including the Miller (to an extent) and the Compton 348 (which has a resistor for setting the amplitude of every 'equivalent pipe' that would exist in an extension pipe organ.) Others cannot; you might be able to change the character of a rank but not compensate for one booming note where a resonance is excited.

Malcolm - yes, it was an official method both for pipes and electronics: Play two harmonics of the note you want and the human auditory processing fills in the fundamental. Some pipe organs have a Resultant 32' stop which does this for you, by combining a louder 16' with a quieter 10 2/3', or ditto for 64' if you are lucky enough to have a real 32'. Electronic organs don't have the same limitations of size and cost for low pitched tones - a 16Hz oscillator is little different to a 16KHz one, but the limitations of practical speakers (especially in the past) made it pointless to provide them. 32' stops were thus often resultants of higher tones that stood a chance of making it through the output transformer and drive units.
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Old 26th Jan 2016, 10:48 pm   #100
Lucien Nunes
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Default Re: 193 valves in 5 days - rescuing the Miller Classic IV organ

Here you are, some video! Laughably bad due to low light, general shakiness and the phone mic being overloaded by the sound level, but it gives an impression. Worth playing through the big speakers as the bass is the best bit. The YouTube clip is unlisted; you'll only reach it from this link but please don't share the link outside this thread as it's not really suitable for public distribution.

Miller at Gala Dinner - YouTube
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