Vintage Synth Explorer Forums

Can't wait to hear it, thanks for the update.

Ashe37 wrote:Can't wait to hear it, thanks for the update.

And I too - but all of you - please don't get your hopes up too high at this stage. Although I've tried my best to make what I can safe this this doesn't means it's suddenly going to produce wonderful noises. It's very much a gamble as to whether the instrument will be at all usable at this stage. I'm keeping a very open mind on this subject.

The hope is at the very least that the overall condition of the instrument can be investigated and that at least some original flavour of the beast captured prior to any further work on the generator chassis.

I will try to make any audio from this initial test available to all via VSE.

It is still possible that this may be as soon as this weekend.

Best of luck with it!

Todays Update:

Novachord 346's PSU Is Back In The Land of the Living!!

I've spent the last 8 hours extending and sleeving the wiring on the new HT transformers and then wiring them into the PSU chassis. This proved to be a little fiddly but it all made sense in the end. I added extra sleeving as I was a little concerned about the heat generated by the inrush limiter.

Wiring In The New Transformers and Under Chassis Choke: The Final Rebuilt PSU Chassis: Having completed the transformer wiring I very carefully checked all of the wiring against the schematic. I found a couple of silly errors - I'd forgotten to wire two of the anodes to the 270V HT rail and I'd managed to get two of the heater winding centre taps swapped over.

The Novachord was not fitted with a single fuse as standard! This I found so frightening that I added a chassis mount fuse holder to the PSU chassis. I fitted a 250mA slow blow fuse just for test purposes.

After visual inspection I connected my 100 Watt bulb limiter along with the Variac and isolation transformer to chassis with no tubes fitted and hooked up the mains. I connected a voltmeter to the main HT windings via the main 5V4 rectifier tube base and wound up the power. Sure enough I could see HT on the rectifier socket. I repeated the test for all of the tube rectifiers and sure enough all of the transformer tappings were present.

I then fitted the rectifier tube for the 50V vibrato rail and ran up the Variac again. The 50V rail is operational and actually produces over 100V unloaded.

After some similarly tentative tests I thought what the h**l and fitted all of the tubes. On running the PSU up this time all of tube heaters came up and then the fuse blew.... oops... I forgot to replace this with a more sensible fuse rating so I changed it for a 1A quick blow. Up went the variac again and after a few seconds 270V DC turned up on the main HT rail After some careful probing it turns out that all of the supply rails were up and producing their correct unloaded voltages!!

The Rebuilt PSU Running With All Tubes Fitted: Tomorrow I will run the PSU up again for a much longer period of time and also attempt to load up some of the rails. I need to confirm that the PSU doesn't run too hot and that the noise cancelling circuits on the 270 and 90V rails are operational too.

It is now looking increasingly likely that I will have a chance to run up Novachord #346 for the first time this weekend!

Fingers Crossed!...........

Cracking stuff! 8)

This Morning's Update:

Testing the PSU Noise Cancelling Circuits:

The Novachord's PSU design is very unusual. Most PSUs in audio gear of this vintage are extremely crude. They usually consist of no more than a transformer, tube rectifier and a number of dropper resistors into fairly large value, high voltage, smoothing caps.

The Novachord's PSU doesn't feature a single large value capacitor on either the main 270 volt HT or the 90 volt biasing rails. Instead it makes use of two active smoothing, noise cancelling circuits made up of 6 tubes. This is extremely impressive for a PSU designed circa 1936!

After looking at the PSU schematic I determined that the easiest way to test the active smoothing was to unplug the final power triode (6K6) which is wired directly across the 270V DC rail in order to load it with phase inverted, AC coupled hum which effectively cancels it.

The PSU Schematic: I then slowly wound the power up on the Variac and observed the 270V rail on pin 9 of the output connector with my scope. Sure enough you can see tens of volts of ripple appear as the 5V4 main rectifier heats up.

I then plugged in the 6K6 (marked tube D on the schematic) and sure enough, after several seconds, the ripple starts to decrease dramatically - in fact so dramatically that I simply had to capture the effect!

The Active SmoothingPSU Warmup Phase Captured on Scope: I'm so impressed with this vintage PSU that I did something a little mad and AC coupled the 270V rail to my PC line input via my safety attenuator box!! Here is the actual sound of the Novachord's PSU heating up!

http://www.last.fm/music/D.A.Wilson/_/N ... ?autostart

What you are hearing is the gradual change from around 24V pk-pk of mains hum to around 2 volts as the tubes come up to temperature and the hum cancelling circuit on the 270V DC rail comes into play.

I will continue soak testing the PSU and hopefully will start to apply power to each section of the Novachord in turn over the course of the weekend.

Still... fingers crossed....

HideawayStudio wrote:What you are hearing is the gradual change from around 24V pk-pk of mains hum to around 2 volts as the tubes come up to temperature and the hum cancelling circuit on the 270V DC rail comes into play.

The point where the tone drops an octave... it sounds like a Novachord tone!

Todays Update!!

JESUS H CHRIST! - IT'S WORKING!!!

After scaring myself silly trying to heat the beast up without risking life and limb it emanated a few sounds and then after running for a few minutes I shut everything down and checked the PSU for overheating. The supply rails were all to spec and the heaters running so I went for it a second time and poked a few keys - more sound - very out of tune but sound. I ran a little longer and powered down again for yet more tests. I then ran it up again but this time for 10 minutes or so and attempted to start tuning the beast. I then realised that I had wound all of the tuning cores in far too much so, with power off again, I wound out all of the oscillator tuning cores to within one turn of being all the way out. I then powered up and attempted to start pulling the thing into tune. As soon as I started to do this I noticed that more and more of the keys were starting to work. After 20 minutes or so, to my amazement, the full top 4 octaves were working. After an hour of runtime I was starting to gain a little more confidence in the monster so I started to adjust the front panel controls and to my delight every single one of them within the top 4 octaves is working. The bottom two octaves are not in good shape.... yet

After 2 hours of playing around and being amazed by how little heat comes off a Novachord (with the exception of the PSU!) I started to make some preliminary recordings to mark the event.

I will start to post some of today's random recordings but I thought I post this first because after downloading it to my PC and having a proper listen I was amazed to hear what this sounded like and then totally blown away by the sound of it through a chorus and reverb (and Marc - I will post demos minus FX too). This is a single take, no transposition or overdubbing, just an out of tune Novachord into FX - and remembering that this using an almost a totally unrestored, 70 YEAR OLD, generator chassis - I am in shock!!

Novachord 346's First Audio Demo:

http://www.last.fm/music/D.A.Wilson/_/N ... ?autostart

One thing that becomes immediately apparent is that this is one heck of a string machine! The second thing - this baby sounds FAR more like the vintage recordings than anything I heard to date. I also got some very nice oboe type sounds out of her along with some very pretty high timbres with a sharp attack. I will try and post these in a bit.

Novachord #346 Being Subjected to Mains Voltage!!

Wow - congratulations!! And 4 octaves working straight off? Pretty amazing... The demo sounds great - I'd also like to hear it without fx, just to know how much of that wonderful sound is the Novachord itself.

Well done - can't wait to hear more!

Frank

HideawayStudio wrote:Novachord 346's First Audio Demo

Wow.

And well done!

I've been quite busy as of late and it's unfortunate that I've not had time to play catch up with this thread, but it's clear to me that you've come a long way very quickly. The Novachord sounds amazing in that example - and way ahead of its time too! It's a bit of a f**k really, to think that sound is emanating from a device that's pre-WWII! Even with outboard effects it's still really impressive.

It's really great to see that you are doing Marc's old Novachord justice and it's clear both your passion for the Novachord and determination to see this project through is incredible. I dare say there's no better man for the job!

OriginalJambo wrote:

HideawayStudio wrote:Novachord 346's First Audio Demo

Wow.

And well done!

I've been quite busy as of late and it's unfortunate that I've not had time to play catch up with this thread, but it's clear to me that you've come a long way very quickly. The Novachord sounds amazing in that example - and way ahead of its time too! It's a bit of a f**k really, to think that sound is emanating from a device that's pre-WWII! Even with outboard effects it's still really impressive.

It's really great to see that you are doing Marc's old Novachord justice and it's clear both your passion for the Novachord and determination to see this project through is incredible. I dare say there's no better man for the job!

Many Thanks - it's rapidly becoming apparent this is quite a remarkable instrument for it's age. This morning I was terrified to power this beast up in all honesty. After a false attempt where it appeared that the HT rail was warming up and going negative I eventually realised this is normal as the negative rails warm up before the main HT rail. As soon as the 270V HT rectifier is up to temp the rail swings the other way and goes positive.

As I say I will post some "dry" samples too. The Novachord clearly lends itself to FX - many sounds just need a lick of reverb but some sustained sounds sound amazing with chorus.

http://www.last.fm/music/D.A.Wilson/_/N ... ?autostart

Absolutely amazing. Sounds gorgeous.

HideawayStudio wrote:

retrosounds wrote:

HideawayStudio wrote:This evening I applied power to the Vibrato Rail for the first time using a current limited bench supply. Sure enough, as I wound the voltage up to 50V DC at 120mA the Novachord's trademark ticking noise began. It's wonderful noise - you could almost imagine six tiny woodpeckers sitting inside the metal box.

Just to chime in here, you think you could get an audio or video clip of that?
This thread has got me interested in the Novachord

You can just about make out the sound of the vibrato reeds working at 6m18s in Marc's excellent video on Sonic State - which features #346 - the very instrument in this thread - she's travelled a heck of a long way since then

http://www.sonicstate.com/news/2008/11/ ... novachord/

Ah yes, I can very faintly hear that clicking.
Awesome.

HideawayStudio wrote:Novachord 346's First Audio Demo:

http://www.last.fm/music/D.A.Wilson/_/N ... ?autostart

Simply beautiful!

Yoozer wrote:Absolutely amazing. Sounds gorgeous.

Many Thanks - I know there is still a long way to go but I never thought this is what I would hear on first power up!

I have made a montage of the demos so far - this will grow over the next few days.

http://www.last.fm/music/D.A.Wilson/_/N ... ?autostart

There are several things I now need to address. Firstly I have noticed that, despite all the PSU rails now being to spec, there is still some mains hum which just might be due to a hum loop in the output transformer. Secondly I am having to run most of the tuning chokes with their slugs almost out of the bodies which means all of the oscillators are in need of slight recalibration. One thing I did notice however is that it's remarkably stable - even with 70 year old caps - there was little hint of tuning drift over the 2 hours it was running.

Things To Fix:

The bottom two octaves are not working at all - I suspect there is a global fault here.
There is at least one note which has a broken envelope generator
At least one of the oscillators is louder than the rest
One of the vibrato channels is sometimes sticking

Things That Work:

All 12 Oscillators are working
All but one note in the top 4 octaves are working
Sustain and Swell pedals are working
All front panel controls, including filters and envelope control are working!

Just amazing for an almost unrestored 70 year old monster - can you imagine most other pieces of electronics lasting this long - not least one containing 163 tubes????