GoodSoundClub - Romy the Cat's Audio Site

06-11-2013

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	61
Post ID:	19482
Reply to:	19481

Oh, no!

It shall not be $50 per piece. You need to go to Electocube web site and they have a very good inventory find tool. It does shoe the actual inventory belong each of their retailer. Then call to retailer and ask the price, it will be about $5-12$ pre 2uF cap, depends how much they have in stock. Usual price was around $7. I have seen the situation that they have some odd 10-12 pieces left over from a large order and if I you get all of then they gave some sub $3 price. BTW, if you need juts 2 caps then tell to Electocube that you are building a prototype and they will send you 2-4 caps for free, juts a testing parts, if they have them in stock. Do not feel bad about it – you will not be abusing them: if you like the caps you will buy more from them. It is what I did. Do not buy any but 950. The 30 and the rest of them are very bad caps.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

06-11-2013

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	62
Post ID:	19483
Reply to:	19482

International pricing?

Hm...it may have been that the retailers I found who shipped internationally overcharged: I must say I did not investigate in detail, but I know others have got similarly unreasonable quotes. The sample request is a good idea: I will do that.

07-21-2013

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DA
Posts 12
Joined on 04-10-2012

Post #:	63
Post ID:	19711
Reply to:	19483

Electrocube 950 ......

decoud , have you managed to find the Electrocube 950 2uF ? I ask because ,I have been trying for the last few months to find a pair,but with no luck.Nothing on EBay ,most retailers do not carry them or shipp internationally .So if you or anybody else have any information that may help or you have a pair of this caps that I can buy please post here or email me ( dandan9 at gmail.com ).

Anyway I'm 2-3weeks from finishing the Milq full range amps.when done I'll post the construction process .

Regards
Daniel

07-21-2013

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	64
Post ID:	19713
Reply to:	19711

Electrocube

Quest Components have cheap 0.68uF 950s in stock, which is what I am using (the SH50s I am driving need a high pass). I have not been able to find 2uF but have not tried Roman's idea of ringing up the factory: they should send you a couple for free without too much fuss.

11-19-2013

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	65
Post ID:	20270
Reply to:	19713

Troubleshooting full-range Melquiades

Hi Romy,
One my channels started emitting intermittent loud popping sounds, once every few minutes or so, and on inspection the current (set at 240mA) was in excess of 300 (my meters top out at 300). Assuming it is a tube problem I replaced the 6c33c, but I still get the occasional pop despite the current now being in range. It seems clear I need to check everything, and I was wondering what parameters would be key to examine here.
bw, d

11-19-2013

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	66
Post ID:	20271
Reply to:	20270

Debugging.

Hm, it is interesting. The loud popping pings in the lower MF and upper bass region are unmistakably signs of the 6C33C be gunner. Then you replaced the tube and the pings are still there. It is very highly unlikely. You might burn a cap that intermittently sorting but it is VERY unlikely. If the pings are in the frequency region that I said above then most likely that your new tube was defective or you accidently put the old tube back to the amp. Do not feel that I consider you an idiot – I did it a few times myself. When the tube is cold go figure which one is old. So, when I pull the old tube from amp I cool it doe and put immediately into trash. In your case your old tube might somehow find its way back to the amp.

If the pings that you have are at slightly higher frequency then you might have a corona in your output transformer. Some transformers are not properly varnished and even as low as 200V that Mils has might create some temp shorts between the turns with time. Take the tubes from the another amp that has no problems and if the amp still does the pinging then disconnect the OPT and plug in any other transformer. A regular power filaments transformer for 12V will do. It will give you an idea if the pings are still there. If not then contact the transformer maker – they shall replace it from free.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

11-19-2013

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	67
Post ID:	20272
Reply to:	20271

Exploration

Many thanks, Romy; I was careful to put the old tube to one side, but it may be the new tube I put in was a defective one. I will explore with the tube from the other channel, which I know is fine.

11-25-2013

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Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006

Post #:	69
Post ID:	20309
Reply to:	20308

The Odds on Tubes

decoud, as I have mentioned before, over the years I've always gotten about 25% bad ones of tubes from all sources, including those that were supposed to be hand picked, triple-tested, high-spec, precision-matched tubes that (of course) cost extra for all the assurances. I once had one each new driver and output tubes from a set that wound up bad at the same time in the same channel, and it took me some time to track down the problem, since it did not immediately occur to me that two new tubes could/would go bad at the same time that way. To top this, one of the two bad tubes was a new replacement for one of a "precision matched pair" I'd just exchanged because it had arrived DOA.

Best regards,
Paul S

11-26-2013

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	70
Post ID:	20315
Reply to:	20309

The lottery

Perhaps we expect too much of these things, from a different era, and very different context of application. And I imagine the cost of the EV version would exceed the 25% attrition rate of the regular versions.

11-26-2013

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	71
Post ID:	20317
Reply to:	20315

An accident.

You need to know that I consider Paul’s finding absolutely ridicules. The 6C33C are very reliable tubes with surprisingly low for Russian tubes defect rate. You juts was unlucky or most likely the person who sold to you your party of tubes sold you bad or used up tubes. The tubes from 196os were slightly better sonically but inferior mechanically. Stay with tube from 80s and you will be very rare seeing any problems.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

11-26-2013

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Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006

Post #:	72
Post ID:	20319
Reply to:	20317

Fail Safe

True enough, the 80s 6C33Cs had a much better percentage of acceptable tubes. Not so lucky with other tubes. The point, however, is that one should always try the tube before taking more drastic action, since tubes can and are known to fail in succession, in pairs, etc., ad nauseum. Another point is that tubes can fail regardless of seller assurances.

Paul S

03-23-2015

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	73
Post ID:	21606
Reply to:	20319

Melq maintenance

Romy, now that there is more than one Melq in the wild, may we have some tips on your approach to maintenance, i.e. what parameters/tubes you generally check/replace and how often? I know the 6 channel version will be different, but there are nonetheless commonalities... For example, there has been talk about the output tube and the gas tubes, but less on the grounds for replacing the driver.

03-27-2015

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	74
Post ID:	21607
Reply to:	21606

No maintenance per se....

Hm, it is hard to say. The gas tubes last long time as I observe. I did change a few versions of them and the last that that I like last for many years. The output tubes are the ordinary suspect, I said a lot at the site about the life expectancy of 6C33C and how identify the candidate for replacement. The drivers are not very long lasting in my view. If you use the amp a few hours each day then I would change them one-twice a year. There is not a lot maintenance per se that I think this amp should have. Nowadays I a worry more not about maintenance for performance but rather a hypothetical possibility for the amps to explode for whatever reasons. I have a baby sleep right between the amps – so it is kind of a subject for me. Thankfully Milq is topologically is not the explodeable amp…

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

03-27-2015

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anthony
Posts 338
Joined on 08-18-2014

Post #:	75
Post ID:	21608
Reply to:	21607

Nice photo

I've seen snow from a distance whilst travelling abroad but never touched it. One day...

Romy, how do the YO-186's last? It would be nice to think that such an expensive tube lasts quite a long time. Have you had to replace them yet?

Regards,

Anthony

03-28-2015

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	76
Post ID:	21610
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I can’t say anything about YO-186

I can’t say anything about YO-186. It looks like it is fine and the bias voltage or plate current did not move since I started to use it. I do not know how YO-186 edges however, it might be possible that she loose the cathode emission while holding the plate current. Subjectively the sound is fine and since the tube is being used at a very conservative operation point I doubt that it somewhere at alarming cathode exhaustion. I wish I was able to test it with objective tester but I never was successful with DHT. I have a very interesting tube tested that might do it, the Royce Rolls of the tubes testers – the Russian L3, but I need to spend a good few days to become comfortable with it…

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

03-28-2015

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	77
Post ID:	21611
Reply to:	21607

Component drift

Thanks, Romy. What about drift in the driver bias, etc?
I suppose the liveliest component, in terms of dramatic breakdown, is the electrolytics. I have been thinking of changing to film, but in that size they are hard to find at reasonable prices.

03-28-2015

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Romy the Cat

Boston, MA
Posts 10,184
Joined on 05-28-2004

Post #:	78
Post ID:	21612
Reply to:	21611

Sure, why not.

decoud wrote:
Thanks, Romy. What about drift in the driver bias, etc?
I suppose the liveliest component, in terms of dramatic breakdown, is the electrolytics. I have been thinking of changing to film, but in that size they are hard to find at reasonable prices.

I do not have any drift in the driver bias, it is dead stable in any Milq I tried. The electrolytic after the gas tubes is a very finicky subject. What I learned what I experimented with it that this last cap to ground after the gas tube does impact sound very dramatic. The selection of 10uF was not an accident but a result of many trials. A 2-3uF up or down did make difference in making sound more relaxed vs. to be more stringent. I do not remember if I tried film, most likely I did and I did have large film caps. I however do not remember the result of film application. It might be worse to try different types of film not or to try to bypass the electrolytic with good film. I am saying it despite that I am not a huge fan of electrolytic bypass but of somebody want to experiment with it then the opportunity is there.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

03-31-2018

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decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #:	80
Post ID:	24773
Reply to:	21613

Snubber

Apologies for the primitive question, but has anyone optimised a snubber for Romy's full range circuit? My implementation does not have one, and I am for some reason now starting to get ringing on start-up of one channel.

	Target	Threads for related reading	Most recent post in related threads	Forum	Replies	Views	Started
»	New	Melquiades For Dummies™ - step by step...	Amp still open...	Melquiades Amplifier Forum	28	214687	08-29-2007
»	New	Building Melquiades: Chronicle of full-range..	VR2 issue leading to jump in current on 6C33 tube...	Melquiades Amplifier Forum	44	435534	06-09-2006
»	New	Building Melquiades: questions and answers...	PeaceMAT XS™...	Melquiades Amplifier Forum	96	569082	10-09-2007

	Target	Threads for related reading	Most recent post in related threads	Forum	Replies	Views	Started
»	New	Melquiades For Dummies™ - step by step...	Amp still open...	Melquiades Amplifier Forum	28	214687	08-29-2007
»	New	Building Melquiades: Chronicle of full-range..	VR2 issue leading to jump in current on 6C33 tube...	Melquiades Amplifier Forum	44	435534	06-09-2006
»	New	Building Melquiades: questions and answers...	PeaceMAT XS™...	Melquiades Amplifier Forum	96	569082	10-09-2007