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04-18-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	121
Post ID:	23169
Reply to:	23168

Filter Caps

Below are some images that show the locations of the various filter caps within the amplifier chassis.

The big cap for the First Stages is located directly below the 6E5P tubes...

Filter Caps 1.jpg

The big filter cap for the Bass Channel is adjacent to the Bass OPT (peeking through a hole):

Filter Caps 2.jpg

The filter caps for the DHT Channel, Upperbass Channel, Injection Channel are immediately below the respective OPT's with enough room between to make the panel meter connections...

Filter Caps 3.jpg

Below you will see the clusters of smaller caps for the Bias string (11 caps) and the Single Stages (4 caps including one yellow)...

Filter Caps 4.jpg

Below can be seen the relative position and orientation of the 5 OPT's.

OPT Positions.jpg

I will look into placing shielding between the OPT's and the tube sockets. There are a few options and I need to think about the best way to implement them.

Thanks for the help so far.

04-18-2017

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Romy the Cat

Boston, MA
Posts 10,156
Joined on 05-28-2004

Post #:	122
Post ID:	23170
Reply to:	23169

Very good

Agree, it is very good. For the vibration isolation, I would worry only about the driver tubes. If you have some money to waste then you might look for ALNIC made tube sockets vibration dumpers. They are VERY effective and if you buy them in bulk then they are not too cost prohibitive. Be advised that the driver tubes are very microphonic when they are cold. As you just turn the amp it will be latterly ringing for a first few mins. It should be dead quite after 5-10 mins. The good question would be if I hear the sonic difference with and without the sockets vibration dumpers. It might be but I think it is more done for intellectual satisfaction. You might rubber recouping via the stand-off for the top tube-caring platform. To make is absolutely crazy you might find (I have seen them) pneumatic inserts in the standoffs and then to use very light wires if loos wires to connect the tube sockets. This will be a great engendering treat but I am not convinced that it will give you tangible sonic advantages.

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

04-18-2017

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	123
Post ID:	23171
Reply to:	23162

Nichicons

Gentlemen, I can only hope to be wrong on the air-borne feedback.
Actually your project Anthony made me think of coming back to my Staxquiades
project - a Milq inspired monster amp for my Stax headphones.
Do you have a source of big PSU Nichicons at a good price?
I'd need 10.000uf/500V

Thanks,

PS I have been practicing a big deal of this extreme acrobatics myself in my end of life phono construction,
just not on such an execution level as yours. I do recognize quite some methods I used myself, although I look
like a dirty DIY-er compared to you. I reached the understanding the sandwitched chassis should be the
best (I even wrote it here somewhere) but have not executed it so far. Vibroisolation is another story.

Cheers,
Jarek
STACORE

04-18-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	124
Post ID:	23172
Reply to:	23171

DigiKey

Jarek, the best source for these big Nichicon electrolytics that I could find was Digikey. They were substantially less expensive than other sources that I tried but do ship from the US which is an added freight cost. I purchased these a couple of years ago so things may have changed and there may be less expensive sources, but I will not buy that sort of stuff from eBay or smaller vendors because I want to know that I am getting the genuine article.

04-19-2017

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	125
Post ID:	23173
Reply to:	23172

Iron?

Thanks! And who is winding your signal iron? Pieter?

Cheers,
Jarek
STACORE

04-19-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	126
Post ID:	23174
Reply to:	23173

No, no Pieter

Lucas Cant from Black Art Automation in Melbourne. I cannot recommend him highly enough.

04-23-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	127
Post ID:	23182
Reply to:	23166

EM Shielding, do or don't?

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.

I've talked to my advisers here about the potential EM induction at the tube sockets from the various OPT's situated beneath. It is not easy to see on the sketches, but absolute minimum separations are 60mm for the smaller, high frequency OPT's and 75mm for the huge Bass OPT. Basically, because the voltages are relatively low at about 200VDC those minimum separations are expected to be "plenty".

If this was a 211 amp with 1800V on the plate then there would definitely be an issue even at 40cm...shielding would be essential.

So I am going to go without shielding in those locations for now. If I have problems then I should be able to retrofit something, but fingers crossed that will not need to happen.

Thanks for bringing it up guys.

04-23-2017

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	128
Post ID:	23183
Reply to:	23182

Mock-up

That's good news, Anthony; no sense doing something like that just to do it. If you really wanted to, you could fire up the trannies and measure the fields.

Best regards,
Paul S

11-23-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	129
Post ID:	24574
Reply to:	23183

Some more DSET photos..

My DSET amplifiers are starting to go together (slowly).

Bias string and bleeder relays/resistors...

Bottom Floor Done 1.jpg

The remainder of the filter caps.
Bottom Floor Done 3.jpg

The middle floor goes on and the filter cap for the First Stages (6E5P/6E6P).

2nd Floor in place 3.jpg

Then the OPT's go in place and the shelf that has most of the bias pots and lpads...
A wee bit more.jpg

The big Bass OPT is finalised in place but the other OPTs are just sitting there and awaiting more wiring.

02-14-2018

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anthony
Posts 338
Joined on 08-18-2014

Post #:	130
Post ID:	24695
Reply to:	24574

DSET labels

I am making steady progress putting together my DSET amplifiers. Life and work gets in the way but I am chipping away at it, taking my time, not rushing, enjoying it. Wow, it is a lot of work and an enormous task for my first complete amplifier build but I'll get there in the end.

Today I picked up from the signwriter some little stickers for the ammeters on the amplifier. There is even a spare sticker just in case I end up with a Midbass Channel rather than the Injection Channel.

In Place 1.jpg

I hope to begin power-on testing of the first DSET in the next week or two...it's getting close...

Almost ready.jpg

02-15-2018

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Romy the Cat

Boston, MA
Posts 10,156
Joined on 05-28-2004

Post #:	131
Post ID:	24696
Reply to:	24695

Some thoughts.

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.

The whole thing looks like very well thought out. A few comments I would like to pass.

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

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.

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.

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

02-16-2018

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anthony
Posts 338
Joined on 08-18-2014

Post #:	132
Post ID:	24697
Reply to:	24696

They are for mA

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.

The ammeters that I have here are quite inexpensive but were one of the few that I could find with a specified coil resistance. It is 3000ohm. So I use a 0.6R resistor to set the ammeter scale to 250mA, 0.75R resistor for 200mA and 3R for 50mA at full deflection. All are quite low values so I think it should be ok.

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.

Yes, I built both amplifiers to the same stage (about half finished) and once things got a bit murky regarding the limitations of the wiring I left the second one at a sensible stage and have gone on with the first. In particular I am hoping that the 6.3V filament wiring for the first and single stages is far enough removed from anything that matters. I am not sure if it is but that will show up in the measurements. I have an audio analyser here that I will use to assess and fine-tune the noise levels so hopefully my preparations have been thorough and not to much will need to be altered.

Romy the Cat wrote:
BTW, did you do it as two identical or you went full-throttle and made it mirroring?

Yes, the amplifiers and the power supplies are both mirrored.

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.

Yes, the filters are very easy to get to and hopefully relatively easy to alter.

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.

Thanks Romy, I'll do that.

12-31-2018

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anthony
Posts 338
Joined on 08-18-2014

Post #:	133
Post ID:	25212
Reply to:	24697

Finally firing up the DSET

Hi Romy,

What a busy year just gone! Finding enough time to just sit down and get the DSET's going has been impossible, but I have time now and have started the process.

At the moment I am introducing some high voltage to the first amplifier chassis, only the Bias and First Stages (for A, B, C channels) - no HV yet for Second Stages, Single Stages or DHT Channel (my DHT has its own power supply). All tubes for all channels are in their sockets. It is confounding me. 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?

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.

Romy, are you able to think of something that could be causing these problems? I think it likely that they are both linked to the same fault, but I just cannot put my finger on it.

Happy New Year,

Anthony

01-01-2019

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anthony
Posts 338
Joined on 08-18-2014

Post #:	134
Post ID:	25213
Reply to:	25212

The bias

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.

Regards,

Anthony

01-01-2019

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Romy the Cat

Boston, MA
Posts 10,156
Joined on 05-28-2004

Post #:	135
Post ID:	25215
Reply to:	25212

Try to debug more.

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?

I think it takes around 60 seconds on my amps. I have 2 minutes delay for high voltage, so it all within the limit. Do not be too hurry, for the first 30 minutes the amp do not sound so great anything. Those 6C33C need some tome to burn in and to reach the cruse operation state. I think after 30-45 min they are fine. If you did not use the amp for let say a week then burn the tubes for 2 hours at least to make the amp so sound “soft” again.

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.

I had it many times and it was always that I found in the end that that I did something wrong. If the channels A and C do give you 200V but C does not then C is not wire in the same way. You should have 400V on plate, 3.5-4V on grid, the heater should be up, the pun 5 and 2 have to be shunted by a small resistor and you should have quite hot plate loading resistor. There is a remote chance that a pin your tube socket got broken and the tube pin does not get voltage…

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

01-01-2019

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Romy the Cat

Boston, MA
Posts 10,156
Joined on 05-28-2004

Post #:	136
Post ID:	25216
Reply to:	25213

A bug in negative supply chain on channel B

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.

Anthony, it is OK. The voltages at all channels are near OK (with exception of C). The bias voltages are irrelevant as all that you care is to get near 200V on plates. It is depending from the tubes you got. It might be 3.5V of 4.5, it is truly irrelevant. You do not want to be at 1.5V as some of other types tubes do as it will be flooded by input voltage and you will clip the driver stage. This amp has no feedback, so no voltage injection into cathode is applied. In our case we have 6E5P that has a relatively high bias and with over 3.5V you will hardly be able to drive the first tube out of A1 operation.

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

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

01-01-2019

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anthony
Posts 338
Joined on 08-18-2014

Post #:	137
Post ID:	25217
Reply to:	25216

Damn crossovers

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.

That is good to know Romy. It was quite frustrating when I though I had a major problem in the Bias Supply that I was unable to diagnose. My power transformer is probably a little smaller than yours and just takes more time to fill all that capacitance.

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

Thanks for your thoughts Romy. Last night I roughly wired in some random crossovers (the same values as in your schematic) and my troublesome Channel B came closer to the fold. It now sits at -7.3V bias and is pulling 290V which is at least conducting something now. This morning I will check again the correct resistor values in that string and then adjust a value so that it pulls roughly the correct voltage.

DSET First Stages 5.jpg

01-02-2019

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anthony
Posts 338
Joined on 08-18-2014

Post #:	138
Post ID:	25218
Reply to:	25217

Six Channels are UP

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.

Initially the gas regulators were only drawing about 9mA each, which is a bit low, so I paralleled the 5k 12w resistors leading in to the tubes and have ended up with 15mA for both 0A2's. This has actually helped the slow startup problem and the negative tube now starts about 30s earlier at about 65 seconds after the bias supply is energised.

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.

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. I think that I will figure out a way to install some test points to make everything easier. They can stay under the covers and out of sight when the amp is closed up. It may also be useful to be able to easily check the anode voltage of the first stage tubes when they get changed out in the future...I have some nice digital voltmeters here that could be run off the service supply or even a battery...I'll look into it.

Cheers,

Anthony

01-02-2019

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	139
Post ID:	25219
Reply to:	25218

Test Points/Trim Pots

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

01-03-2019

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anthony
Posts 338
Joined on 08-18-2014

Post #:	140
Post ID:	25220
Reply to:	25218

Shot too early...

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.

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!

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.

On the schematic at the DHT tubes you have annotated a couple of red voltages and I am unable to measure the 184V at the cathode and the grid is measuring very low (without a DHT tube in the socket) at 148V where 224V is required.

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.

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