anthony wrote:

...you've got me thinking about this now.  I'll talk to some people here and see what they think, but it should be easy enough to place a shield between the OPT's and the tube bases. Thanks for bringing it up.  I am looking for other angles to view the design, and yourself and Jarek have been very helpful.

Romy the Cat wrote:

You decided to go with mA or are they mV against 1R resistors? I prefer the second approach personally and I feel that I can moderate the quality of resistor and I can’t moderate the quality of the milliampere meter coil.

Romy the Cat wrote:

You are right now in a very interesting state when you do the internal wiring. The internal wiring. Is to a degree is an art form and it might be very interesting. There are low and high voltages, AC and DC, twisting and not, crossing with minimum angles, some transmission line considerations, signal wires, grounding, approximations, shortening wire paths, maintainability, ease to access and many other considerations that you need to keep in perspective. It is very interesting and creative phases, do not harry to go through with it, spend some time and do it better and methodological. Do the same wiring schema for both R and L amplifiers. When you will be doing the second amp you will find better way to wire it. It is debatable if you want to improve the second one or to the second one as a direct replica of the first one.

Romy the Cat wrote:

BTW, did you do it as two identical or you went full-throttle and made it mirroring?

Romy the Cat wrote:

Also, if everything is works fine then the only part that you might need access it future will be the input filters in case you want to experiment with drivers or do channels adjustments. Make it accessible. Do not forget to do a full sweep of the individual channel after you will be done. You need to make sure that the channels and the filters are working properly.

Romy the Cat wrote:

The last thing. Do buy for yourself a Phase Testers. This is absolutely mandatory tool for your speakers. They call it “Speaker polarity tester”. I use the track #23 from Sheffield Labs     https://www.amazon.com/Sheffield-A2TB-Test-Disc-My/dp/B000V93NKY     Depends what tester you use you might not have a sensitivity of you tester to test at LF. There are some techniques how to deal with it. Anyhow, even a cheap $10 tester for Car Audio is better than to spend half of life to worry where is black and where is red binding posts.

anthony wrote:

Firstly, the -200V Bias supply takes ages to come up to voltage but it does get there...no issues for the +200V side, it charges is 200uF caps almost instantly, but 9,000uF on the negative side takes almost 90 seconds to get to -200V, and the negative 0A2 does not light up until about 90 seconds after the bias supply starts to power up.  There is an issue there...how long does it take your negative 0A2 to ignite Romy?

anthony wrote:

Secondly, and these issues may be related, the First Stages 6E5P (for Channels A, B, C) are not behaving as I would expect.  I've checked the wiring a number of times and as far as I can tell it matches the schematic, and while A and C sit at about 200V at their anodes, Channel B sits at 400V or so and its 15K 12W resistor is staying cool and not drawing any current which means that the tube is not conducting.  I've checked resistances from the tube socket to other parts of the circuit and swapped tubes and nothing changes.

anthony wrote:

Hi Romy, Further to my earlier message, I've measured the bias voltages for the driver tubes in all Channels. A -4.3V not adjustable B -13.82V not adjustable C -4.8V not adjustable D -4.2V (ran out of potentiometer travel...may have to adjust a resistor) E uses fixed cathode bias...not measured this round F -4.3V (adjustable with pot.) Looks like something is going on with A/B/C.  B is the worst and is the 6E5P that is not conducting (has 400V at the anode).  I've not installed the crossover components in this channel yet (the 12.1K resistor and 0.043uF cap to ground) but perhaps I should install something even though the crossover point will probably change...I'd not have thought they would make a difference at this stage.

Romy the Cat wrote:

I think it takes around 60 seconds on my amps. I have 2 minutes delay for high voltage, so it all within the limit.

Romy the Cat wrote:

Your channel B bias is 13.82V wish is the problem. The tube is closed with such high bias. As you will bring the bias doe to near 4V the tube will open and the plate current will flow. You nned to debug your negative supply chain on channel B

anthony wrote:

Hi Romy, So, six channels are now operational in the first DSET.  By up I mean the anode voltages on all tubes is about right and the currents are in the ballpark of where they need to be.  I am yet to check the DC Offset so hopefully that goes ok.

Paul S wrote:

Anthony, congratulations on getting your project to this point!  I mention without referring back to your schematics, I think you will be glad to have test points, along with variable resistors (trim pots) to re-set operating points, as needed, if only for normal drift. This can help avoid insanity down the road, and it also give you the chance to "dial in" your operating points by ear, when you are ready to do this. Again, I am not sure what's called out. In any case, ESR changes with X/O changes would make VRs useful there, as well. Best regards, Paul S

anthony wrote:

Thanks for your thoughts Romy.  Last night I roughly wired in some random crossovers….

anthony wrote:

So, six channels are now operational in the first DSET.  By up I mean the anode voltages on all tubes is about right and the currents are in the ballpark of where they need to be.  I am yet to check the DC Offset so hopefully that goes ok.

anthony wrote:

The Channel B is still an issue of sorts.  I have reduced R5 from 12k to 5k to get down to 200v at the anode of the 6e5p.  For the life of me I can't figure out why because all components in the bias string are the correct value and the cap is polarity correct.  Channels A & D also operate from the same arrangement for the positive bias and they hit their targets first time, so to my thinking it must be an issue in the negative bias string, however that string is correctly installed.  So, I have a decision to make.  In Channel B, assuming that I use a similar first order  RRC Low Pass filter at the start, do I reduce the 30k resistor by 7k, or do I reduce the 12.1k resistor that sits closer to the grid by 7k?  I am leaning toward changing the crossover resistor, and am not even sure either will make an audible difference.

anthony wrote:

One thing has become very clear to me while sorting out this first DSET...the crossovers in Channels A-D affect the operation of the bias, so when changing filters I may have to re-tune the bias for that channel.

anthony wrote:

Looks like I spoke too early.  When I made that statement I'd only tested the voltages in the DHT Channel and they were pretty close to correct...but when I put a tube in there it glowed a little too hot so I quickly shut it down.   Bugger!

anthony wrote:

Romy, without any DHT tube in place, I have 403V coming out of the big filter cap for the DHT Channel (separate power supply) and 147V/8.3mA at the anode of the 6e5p which is a little higher/lower than the 140V/10mA on your schematic.  I am wondering if this lower current could be the problem?  I added some more resistance to drop the anode voltage and although I thought it was going to drop it 9V it only dropped it 3V, and the anode current remained at 8.3mA.  Tomorrow I will drop the anode voltage further so see if that raises the current.

anthony wrote:

It would be great if you could remember some of your time with the DHT Channel.  I've only just got my head partially around your IDHT Channels and this circuit is almost entirely different again.

anthony wrote:

I woke up this morning to have the brightest thought that my DHT issues are probably caused by how I have wired up the filament transformers.

anthony wrote:

I woke up this morning ….

anthony wrote:

Then I swapped the used YO186 I purchased just for this testing stage and put in a NOS 1939 vintage tube and the circuit worked straight away with all voltage and current targets just perfect.  Put in a 45 and it was just as perfect.

anthony wrote:

The DC Offset would not trim to zero and 0.1mV was as low as it would go before running out of trimpot.  The pot from one end to the other would only adjust the DC Offset by 0.7mV, which is much less than I thought it would.  My 0A2 are quite closely matched for voltage and are within 0.3V of each other.  Swapping the tubes had no effect on the DC Offset so I might have to play with another tube to cancel that offset to zero.

Romy the Cat wrote:

anthony wrote: I woke up this morning …. It was funny that you named it “In my dreams”. Whan I was “designing” and building the Milq I had a lot of dreams about the problem I had. I am not am amplifier designer or some kind of DIY evangelist. In fact I had no truly DIY audio experience before it. I did my phonostage and the power amps because I did not had around me somebody who would do it for me at the level I want to do it. So, when I start to do the damn soldering I was learned a lot and for some period of time it become a very much become full time labor, not time wise but mind-wise. There was a period when Milq took so much time in my life that stopped do anything, literally anything but making Milq to sound right. In the epicenter of that period there was six months when I stopped working, stopped dating, stopped socializing with other people. I woke up 7 AM and went to beg at midnight, all time working on the amplifier and having 100% of time dedicated to thinking about the amplifier. My mind was so saturated at the time by the applier need that I have dream about Milq circuitry, Milq’s problem, Milq’s need… It was a lot of Kafka like dreams…. very certifiable. I am not sorry about that time and I even then had very defined feeling that after I do it I am not planning to do it anymore. So, nowadays if I need to dive into Milq to make some changes then I feel that I am rereading the dairies of my life… very interesting…

Romy the Cat wrote:

Your chasses design look spectacular by the way. In many year what your will dive back to that amps you will not believe you did it.

Romy the Cat wrote:

Generally speaking I would be interested to know how you like to change the crossovers. I feel that sine you have the same configuration as I do I know that result you should be getting and there is a HUGE amount of time invested into this thing to do experimentation, listening, testing, measuring etc and there is not a lot known to me room for improvements. Trust me it has  nothing to do with ego  and I will LOVE to learn if you fine any better way to organize what has been organized, unless you use other compression driver…

Mains power here is 240VAC.

It's a 4 minute startup protocol.  It briefly draws an amp when plugged into the wall and the Services LPS fills its capacitors, then settles down to virtually nothing, less than 20w.  Then I hit the power foot pedal and the AC filaments/heaters are all lit up and being direct AC there are no caps or other electronics so not much of a spike.  The bias and 1st Stages are powered 45 seconds later (just past 1m on the graph) and there is a 5A spike as the power supply caps are filled.  That sits at about 150w until three minutes later the DHT, 2nd Stages and Single Stages power supplies are energized.  The DMM logs once a second and managed to capture about 11A, which is as much as the mains supply is rated, maybe a little more...perhaps I should put in a soft start.  Anyway, after that the amp sits on a pretty neat 400W power draw at idle.  Being Class A that should be where it stays even when playing music.

So, 400 watts power draw to light up a combined total of 30w-33w of output power.

anthony wrote:

To mirror your obsession, but not as the instigator of the project, rather as the duplicator, it has been my plan for some time to take off all of January to get my Melquiades/Macondo installed in my room.  Being self-employed with too many clients to keep satisfied that is not really going to happen but I do plan to be able to operate with the emphasis towards leisure rather than work for the next couple of months as a compromise, perhaps something like week-on week-off, but something at least very flexiblle.  My wife is with me completely in the desire to have this project finished, but I suspect for slightly different reasons than I.

anthony wrote:

I listened exclusively to Bruckner symphonies for almost 6 days straight (I discovered Celibidache and was transfixed by the slow phrasing in particular of the 8th).

anthony wrote:

..the closer I come to a realisation of my efforts the more I understand and appreciate just how colossal yours has been.

Anthony wrote:

It's a 4 minute startup protocol.  It briefly draws an amp when plugged into the wall and the Services LPS fills its capacitors, then settles down to virtually nothing, less than 20w.  Then I hit the power foot pedal and the AC filaments/heaters are all lit up and being direct AC there are no caps or other electronics so not much of a spike.  The bias and 1st Stages are powered 45 seconds later (just past 1m on the graph) and there is a 5A spike as the power supply caps are filled.  That sits at about 150w until three minutes later the DHT, 2nd Stages and Single Stages power supplies are energized.  The DMM logs once a second and managed to capture about 11A, which is as much as the mains supply is rated, maybe a little more...perhaps I should put in a soft start.  Anyway, after that the amp sits on a pretty neat 400W power draw at idle.  Being Class A that should be where it stays even when playing music. So, 400 watts power draw to light up a combined total of 30w-33w of output power.

Romy the Cat wrote:

I was also self-employed, running consulting s-corporation and taking 6 month off I once calculated how much money I lost turning down some lucrative contracts. It was a lot! Well, it was juts money… Saying that I need to admit that if I were married that time I do not think I would be able to pull it off. My compliments to you wife patience

Romy the Cat wrote:

Now we are taking!!! Celibidache certainly would do it. A few years back I caught live performance of the 8th in London with Vienna and late Mazel. They did a very nice slow version of adagio, not as slow as Celibidache did during his slower concerts but still quite slow but Mazel did some absolutely mind boggling poses and some amassing prolonging phrases that went against all rules of physics. That all make the performance absolutely beyond believe. If you like very slow interpretation, like I do, then you might start to listen some Barbirolli Mahler…

Romy the Cat wrote:

It is not the numbers that I got. I had if I member correctly 330W draw after the amp hit the cruse temperature, the I initial inrush of current was I think about 10A and I use 8A slow blow fuse for the whole amp. The 4 minute startup protocol is kind of slow but it for sure protect the amp's parts well.