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.

anthony wrote:

Yours uses all toroids, or mostly so, which are more efficient than the EI that I use.

N-set wrote:

Congratulations on the build!  anthony wrote:   Yours uses all toroids, or mostly so, which are more efficient than the EI that I use. Why have you chosen EI vs toroids? The latter emit less. Cheers, Jarek

• are smaller for the same power rating
• are more efficient transformers of power than EI
• if carefully made can have low flux leakage
• are high bandwidth devices so more noise on the power line is transferred into the circuit
• have no gap and will hum when there is DC on the mains

• are larger for the same power rating
• have a gap and do not hum when you have DC on your mains (unless there is so much that the core becomes saturated)
• are lower bandwidth devices so act as a low pass filter for mains noise (we really only need to pass 50/60Hz - the rest is unwanted)
• leak some flux so they should be kept further separated from the sensitive circuits

Romy the Cat wrote:

If you like very slow interpretation, like I do, then you might start to listen some Barbirolli Mahler…

anthony wrote:

Plenty of thought has gone into the speaker cables largely because there are plenty of them and I would prefer for them to be hidden completely from view.  Five of the six channels exit the amplifier in the well that fits around the horn stack pillar where they are nicely hidden, and the bass channel exits from the side closest to the Bass Cannons.  I've thought about different types of speaker wire from exotic to simple and in the end I have gone with simple Duelund 16GA tinned copper wire.  I've used this before with fullrange speakers and it is fine.

anthony wrote:

As discussed earlier I have gone for ammeters instead of voltmeters.  I can hit the mA target on all but one channel (F), but with exception of E (DHT Channel) they sure do wander about a bit, particularly the 6C33C channels.  Romy, is this normal?  I set them at about 240mA/150mA/150mA and they will go down over time and then they will come back up and past their original settings then they may wander down again.  Makes setting a stable current draw like herding cats.

anthony wrote:

Here is Channel F.  It won't come over about 20-25mA.  Plus the DC Offset won't trim out less than about 0.27V (yes volts).  I have a feeling that the two problems are linked and will check to see where I have wired up the input filters for each channel.