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07-03-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 41
Post ID: 21753
Reply to: 21752
The LPADs....
fiogf49gjkf0d
What do you mean the example of inductive Lpad? All speaker level Lpads are inductive. The speaker level Lpads work with low voltage and high current and therefore they use wire wound restive elements. Any wire wound components are inductive by nature. In fact most of the non wire wound resistors are inductive and you need to pay premium to get not inductive resistors if you need it. I do not know if cheap Part-Express Lpad would be more inductive then some kind of super-expensive Lpad from other brand. They are inductive not by "bad or cheap making" but by topology of restive wire wound restive element. BTW, I had a few vintage German and British LPAD that I fished on eBay and they were way more inductive then the contemporary LPADs. They were not better sounding ether.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-03-2015 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,103
Joined on 10-12-2006

Post #: 42
Post ID: 21754
Reply to: 21753
Like This?
fiogf49gjkf0d
The usual "trick" to "stop inductance" of wire wound resistors is the "old double-wound trick", like those offered by Mills:
http://www.soniccraft.com/index.php/resistors-mills-c-29_53

(and I think it is much the same for capacitors, for that matter...)

Shallco makes acceptable attenuators, if this is what you are looking for:
http://www.shallco.com/attenuators.html

I thought part of the "fun" of audio electronics is that any "element" in an active series/circuit is part of a "reactive element"...

How I love DIY!


Best regards,
Paul S


07-09-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 43
Post ID: 21767
Reply to: 21753
Now that I have had a good look at them...
fiogf49gjkf0d
 Romy the Cat wrote:
What do you mean the example of inductive Lpad? All speaker level Lpads are inductive. The speaker level Lpads work with low voltage and high current and therefore they use wire wound restive elements. Any wire wound components are inductive by nature. In fact most of the non wire wound resistors are inductive and you need to pay premium to get not inductive resistors if you need it. I do not know if cheap Part-Express Lpad would be more inductive then some kind of super-expensive Lpad from other brand. They are inductive not by "bad or cheap making" but by topology of restive wire wound restive element. BTW, I had a few vintage German and British LPAD that I fished on eBay and they were way more inductive then the contemporary LPADs. They were not better sounding ether.

...I see what you mean.  I found some images of the insides of some of these speaker level L-Pads and they certainly do look like they are inductive.  I understood the wiring technique used to make wirewound resistors non-inductive and I assumed that this was available for speaker level L-Pads as well.  

One question that I still have regarding the L-Pad on the MF Channel is why you did not lose more gain at the filter before the MF driver stage?  By my reckoning a resistor change here would shunt more signal and you would possibly not need the S102 resistors at speaker level.  Of course you may have just experimented and found a solution that worked well enough and left it there...or I may have missed something.

Romy, I see that you are a fan of the air-capacitor at high frequencies.  It has been interesting reading about where you have been successful (or not) with them and what you have had to do to get them to work.  Intriguing even.  If you don't mind me asking, what do you look for when selecting an air-capacitor?  This is all foreign to me.  There are variables such as construction material, number of gangs, air-gaps and voltage ratings.  I would assume that it is important not only to shield them from RFI but to seal them so they remain clean.  Would you care to reveal your source for these caps?

Regards,

Anthony 

07-09-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 44
Post ID: 21768
Reply to: 21754
DIY
fiogf49gjkf0d
 Paul S wrote:
The usual "trick" to "stop inductance" of wire wound resistors is the "old double-wound trick", like those offered by Mills:
http://www.soniccraft.com/index.php/resistors-mills-c-29_53

(and I think it is much the same for capacitors, for that matter...)

Shallco makes acceptable attenuators, if this is what you are looking for:
http://www.shallco.com/attenuators.html

I thought part of the "fun" of audio electronics is that any "element" in an active series/circuit is part of a "reactive element"...

How I love DIY!


Best regards,
Paul S



Thanks Paul.

I get the feeling that when/if this DSET build gets across the line that I will have more energy for further refinement of the amplifiers than Romy did at the end of his endeavours.  Unfortunately I will not have the benefit of the "thousands of steps" that he has taken and the benefit of hindsight they afford so my efforts are likely to be more wayward than Romy's, but it will be interesting nonetheless.  I really don't want to DIY just for the sake of it...I want to get a good result and then be done with it...figuring out what I need to do to achieve an objective is the difficult part because of, as you say, the "reactive" nature of audio electronics and their interplay with what comes out of the speakers.

Cheers,

Anthony
07-09-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 45
Post ID: 21769
Reply to: 21767
Better air-caps?
fiogf49gjkf0d
 anthony wrote:

One question that I still have regarding the L-Pad on the MF Channel is why you did not lose more gain at the filter before the MF driver stage?  By my reckoning a resistor change here would shunt more signal and you would possibly not need the S102 resistors at speaker level.  Of course you may have just experimented and found a solution that worked well enough and left it there...or I may have missed something.

 
Sure, it is completely makes sense to put a Lpad before the Milq driver. There are two “conditions” however. The impedance before the driver is used for bias, so you would need more resistors to separate bias and load-constant attenuation. And the last is that in my situation, with my MF tube and my S2 driver I still feel that mild” but very well controlled inductance is beneficial to my sound.
 anthony wrote:
Romy, I see that you are a fan of the air-capacitor at high frequencies.  It has been interesting reading about where you have been successful (or not) with them and what you have had to do to get them to work.  Intriguing even.  If you don't mind me asking, what do you look for when selecting an air-capacitor?  This is all foreign to me.  There are variables such as construction material, number of gangs, air-gaps and voltage ratings.  I would assume that it is important not only to shield them from RFI but to seal them so they remain clean.  Would you care to reveal your source for these caps?

 
I look only for size per volume and ability to hide them. There is some belter air-capacitors, some of them silver with holes, just open some top of the liners HP, or Textronics of RS from 80s. I don’t try them however for sound.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-23-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 46
Post ID: 21795
Reply to: 21769
Top Plate Draft #1
fiogf49gjkf0d

I got some time on the PC to start to think about how to layout the DSET.  I plan to build it a little like a skyscraper:  multiple levels separated by component groups and functions.  
 
 
So mains transformers, AC socket and perhaps time delay relays on the ground floor wrestled into their own sarcophagus that will use some sort of low frequency suspension/vibration management in an effort to keep mechanical vibrations from reaching the rest of the chassis.  Then the AC-DC conversion on the first floor, filter caps and output transformers on the third level with the amplifiers sitting proud on top.  I don't want to see any caps or transformers...just valves.  
 
 
By attacking it this way I think that I will be able to build each "floor" on the bench and the hook them into place with minimal in-situ soldering.  Over the top will go a nice wood or metal facade that will leave the valves exposed but cover the workings.
 
 
So in an effort to see just what sort of footprint I can get away with (prefer small footprint and tall height) I took to SketchUp and produced the first draft layout for the amplifier plate that will be the very top level.  As can be seen below I can get everything to fit in about a foot square...which is great...but I doubt that I will be able to get the iron below into such a small footprint without splitting it over more levels...but we will see.  I have tasked well regarded local fellow to produce all the iron that I will need:  mains transformers, filament transformers, chokes, inductors, output transformers.  We will see what he comes up with but I have not made a final decision regarding this stuff and I certainly as yet do not have dimensions of the gear, so laying out the lower levels is not quite possible at this time.
 
 
Here are a couple of images...notice that I have tried to keep the 6C33C's about two to three inches from the smaller tubes and about two inches separated from their brethren.
 

Top_Plate_Draft_1.jpg

Top_Plate_Draft_2.jpg
07-23-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 47
Post ID: 21797
Reply to: 21795
Many options are available.
fiogf49gjkf0d
 anthony wrote:
 Then the AC-DC conversion on the first floor, filter caps and output transformers on the third level with the amplifiers sitting proud on top.  I don't want to see any caps or transformers...just valves.
Possible, even I like more the idea of separation of PS and control circuit on the different chassis. The vertical towers work very well with SS amps. With tube and particularly with input choke DSET you will have a lot of LF vibrating high mass element and you won’ be able to quite them down. But this is juts might personal take. What is non-personal and absolutely certain is that you can’t put the last cap in your PF at the different floor then your tubes. The caps need to be right there in very close proximity to tube. If you chose to have large caps then the accommodations need to be made. If you have unlimited heights then you can make the 2 floor of the caps and the third of the tubes. 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-29-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 48
Post ID: 21818
Reply to: 21797
Fleshing out the design a little more...
fiogf49gjkf0d
 Romy the Cat wrote:
 anthony wrote:
 Then the AC-DC conversion on the first floor, filter caps and output transformers on the third level with the amplifiers sitting proud on top.  I don't want to see any caps or transformers...just valves.
Possible, even I like more the idea of separation of PS and control circuit on the different chassis. The vertical towers work very well with SS amps. With tube and particularly with input choke DSET you will have a lot of LF vibrating high mass element and you won’ be able to quite them down. But this is juts might personal take. What is non-personal and absolutely certain is that you can’t put the last cap in your PF at the different floor then your tubes. The caps need to be right there in very close proximity to tube. If you chose to have large caps then the accommodations need to be made. If you have unlimited heights then you can make the 2 floor of the caps and the third of the tubes. 

Yes, I think that the separation of the PS and amplifier is very important to make this all work to properly.  I have fleshed out the design a little more.

First of all the footprint has been increased from about 300mm square to about 400mm square as there was just no way to get all of the OPT's close to their power tubes with the smaller size.  As it is now there is spare room up top with the valves and I am considering whether to introduce a curved roll-off from the top surface to the sides rather the the square "industrial" look.  I am not sure.  I will have to draw it to see what it looks like.

As drawn below, each mono-bloc will stand somewhere around 1m tall.  I think that this will work well when you consider that the Upperbass Horn will stand about this tall and I plan to snuggle each mono-bloc in behind and immediately beside the horn stack, and with the speaker cables coming out at a little under that 1m height I can keep the speaker cables very short.  If I keep the amps in nice and close to the horn stack perhaps all I will see of the amplifiers from my seat will be the tubes thus helping to make a visually large audio system seem a little smaller when seated.

Notice that not all of the components are shown in these sketches.  The OPT's (in an off-yellow/light brown) have not been chosen so I do not have exact dimensions and have used cuboid of approximately the right size.  All the filter caps are shown, but the smaller caps for the bias are just randomly placed in their approximate positions along with a few of the associated components.  There should be plenty of room under the top plate for amplifier components (caps ans resistors) and if necessary I can spill into the vacant space of the layer below for parts of the crossovers.


DSET Tower - Early Days #1.jpg


You can see that I plan to use vibration management in two places on the amplifier:  firstly under the entire amplifier with a constrained layer platform sitting on springs so that hopefully vibrations above 5Hz or so are not transmitted from the floor to the amplifiers;  secondly using the same system internally for the power supply which I intend to keep highly isolated from the amplifier section above it.  The brown three layer sandwich is the constrained layer platform but I have not drawn the springs.


DSET Tower - Early Days #2.jpg


In the shot below you can see the placement of the OPT's.  They are very close to the centrally located large filter caps and only a few inches from their respective tubes keeping the B+ voltage lines short.  You can also see the Bourns potentiometers (in blue).  I plan to have these situated behind two little drop down doors.  This way I keep the knobs out of eyesight.

DSET Tower - Early Days 3.jpg


Lastly, this shot shows the location of the smaller filter caps for the bias and a little more of the location of the large B+ filter caps.

DSET Tower - Early Days 4.jpg



AC and DC wiring may be able to be transported from the power supply section to the amplifier section inside one or more of the eight chassis columns.  Perhaps run a PVC tube up the centre of the column and glue some rubber grommets at the entry points and the wiring would be neat and tidy.  I am not sure sure of the electrical consequences of running the wire inside a number of steel bars, but hopefully it will be ok.

Opinions and insight are appreciated.

Regards,

Anthony
EDIT:  Not sure why the images are not showing up properly.  Romy?
07-31-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 49
Post ID: 21821
Reply to: 21818
Interesting but….
fiogf49gjkf0d
Generally I like it but I have some concerns, whatever rubber feet and decompiles you will be using you will not defeat the vibration if you have a few transformers and a few 500A input chose sitting at the bottom. You will take a statoscope and you will clearly have the vibration on the tube floor. Well, you will have noise on the tube floor but how will affect sound is very hard to say. A common sense would suggest that you should not have any vibration in there, and in particularly because you use very fast and relatedly microphoneic tubes (when they cold) in driver stage. But in reality it is not so simple and I have seen when vibrated control unit sounding more stage then fully isolated. Still, I would go for fully isolated control unit (tube floor). 
 
The biggest concern that I have if you have a single chasses with PS at the bottom is that your caps at the mid floor is that your caps, like the rest of your components inside will be greatly over heated. The transformer and choke will be getting hot and your entire amp will be a basic chimney with hit-sensitive caps in the middle. I think it is one more argument to put PS to a separate chasses. You still cat stack the PS and control unit one above another, in the way how I did it: 
 
http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=2715#2715 
 
…but this way you might have more effective heat and vibration decupling. You will be going over the hell of dealing with connecting cables but you might outsource it and order the connectors and cables to be made for you.

 anthony wrote:
Not sure why the images are not showing up properly.  Romy?

Do not use “#” in the picture names and the will be shown


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-04-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 50
Post ID: 21834
Reply to: 21821
Heating is an issue...
fiogf49gjkf0d
 Romy the Cat wrote:
Generally I like it but I have some concerns, whatever rubber feet and decompiles you will be using you will not defeat the vibration if you have a few transformers and a few 500A input chose sitting at the bottom. You will take a statoscope and you will clearly have the vibration on the tube floor. Well, you will have noise on the tube floor but how will affect sound is very hard to say. A common sense would suggest that you should not have any vibration in there, and in particularly because you use very fast and relatedly microphoneic tubes (when they cold) in driver stage. But in reality it is not so simple and I have seen when vibrated control unit sounding more stage then fully isolated. Still, I would go for fully isolated control unit (tube floor). 
 


Yes, I considered running an separate isolation platform for the amplifier section but could not think of an easy way to incorporate it into the design as it stands.  Thinking about the weight of these things it will probably be a good thing to be able to break them in two to have some chance of shifting them by hand so I will revisit the design.  
The isolation platforms are spring mounted.  The springs will be loaded by the components that sit on them and the weight of the platform itself so that when you give it a nudge the unit slowly oscillates at a very low frequency, say a couple of hertz.  I dare say that the idea is not so different to the Silent Running Audio stuff that you use.  The stethoscope is a very good idea.  Much more simple than the accelerometer that I was considering to sort this stuff out.

 Romy the Cat wrote:
  
The biggest concern that I have if you have a single chasses with PS at the bottom is that your caps at the mid floor is that your caps, like the rest of your components inside will be greatly over heated. The transformer and choke will be getting hot and your entire amp will be a basic chimney with hit-sensitive caps in the middle. I think it is one more argument to put PS to a separate chasses. You still cat stack the PS and control unit one above another, in the way how I did it: 
  
http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=2715#2715 
  
…but this way you might have more effective heat and vibration decupling. You will be going over the hell of dealing with connecting cables but you might outsource it and order the connectors and cables to be made for you.


I was going to seal off the power supply section at that thick platform that is about halfway up the tower and either chimney or fan force warm air out the sides so that it does not affect the amplifier section.  This will keep the warm air from the internals of the amplifier section.

 Romy the Cat wrote:

 anthony wrote:
Not sure why the images are not showing up properly.  Romy?

Do not use “#” in the picture names and the will be shown

Understood.  Thanks Romy.
08-08-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 51
Post ID: 21837
Reply to: 21821
LPad in Channel F
fiogf49gjkf0d
Hi Romy,

I am calculating crossover scenarios for the HF Channel (Channel F) and am hoping that you can remember a reasoning for using a 20K LPad instead of a larger value such as 30K or even 50K?  As the larger impedance is used the value of the capacitors reduces and the size of the inductor increases, which I would have thought to be a good thing in terms of the actual performance of the inductor compared to its design specifications.  Unless your aim was to minimise the inductor size or you were just using the LPad that you had available?

I am not sure how increasing the LPad from 20k to 50k would affect the operation of the filters in the other channels.

Regards,

Anthony
08-10-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 52
Post ID: 21839
Reply to: 21837
It does not matter.
fiogf49gjkf0d
 anthony wrote:
I am calculating crossover scenarios for the HF Channel (Channel F) and am hoping that you can remember a reasoning for using a 20K LPad instead of a larger value such as 30K or even 50K?  As the larger impedance is used the value of the capacitors reduces and the size of the inductor increases, which I would have thought to be a good thing in terms of the actual performance of the inductor compared to its design specifications.  Unless your aim was to minimise the inductor size or you were just using the LPad that you had available?

I am not sure how increasing the LPad from 20k to 50k would affect the operation of the filters in the other channels.
  
There is no aspects of minimization of the inductor size. You can go to 30K, or 50K, or 100K input LPAD. The LPAD (which is not inductive switched attenuators with good resistors) anyhow sites behind the filter, so the input impedance of the attenuators will be “visible” by other channels only at HF, so the value of the attenuators is semi-irrelevant. The reasons why I went with 20K is because I would like to keep the value of the resistors that formed the attenuators lower. If I use S102 resistors that have no inductance of any kind then the value of the resistors would be absolutely irrelevant. I use very good resistors for attenuator (RN/CMF55/60), they are metal film and non-indicative but they still have “some” residual inductance and my presumption was that higher value the more inductance. I warn you that this is such an irrelevant minor thins that we can talk about it but I very confident that it has no practical impact to the sound you will get out of it. So, in term of the input attenuators for HF you can do anything you want.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-12-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 53
Post ID: 21847
Reply to: 21839
A few power supply changes
fiogf49gjkf0d
 Romy the Cat wrote:
 
There is no aspects of minimization of the inductor size. You can go to 30K, or 50K, or 100K input LPAD. The LPAD (which is not inductive switched attenuators with good resistors) anyhow sites behind the filter, so the input impedance of the attenuators will be “visible” by other channels only at HF, so the value of the attenuators is semi-irrelevant. The reasons why I went with 20K is because I would like to keep the value of the resistors that formed the attenuators lower. If I use S102 resistors that have no inductance of any kind then the value of the resistors would be absolutely irrelevant. I use very good resistors for attenuator (RN/CMF55/60), they are metal film and non-indicative but they still have “some” residual inductance and my presumption was that higher value the more inductance. I warn you that this is such an irrelevant minor thins that we can talk about it but I very confident that it has no practical impact to the sound you will get out of it. So, in term of the input attenuators for HF you can do anything you want.

Thanks Romy, that is just the information I was after.


I am planning to add an extra power supply just to run the DHT channel.  In the course of things this lets me scale down the power transformer and choke for the first stages of Channels A, B, C (that choke is a monster!) and it eliminates the 56R resistor on the DHT B+ which may or may not be affecting things.  

Also I am scaling down the power transformer for the second stages of Channels A, B, C to roughly half of the specified current rating.  I have a feeling that that trafo is rated 3A because at the beginning of the 6-Channel project there was the potential for 6 x 6C33C, but in the course of development that is now reduced to three.  The smaller power transformer should operate closer to its nominal voltage rating as a result and the chokes that follow will probably operate closer to their rating as well.

Regards,

Anthony
08-12-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 54
Post ID: 21850
Reply to: 21847
The opportunities are endless.
fiogf49gjkf0d
Anthony, there is many areas for power supply scaling down if you want to. You can put an extra 440V coil on your power transformer that driver output stage and have PS for driver stage and perhaps bias. Do not forget that this high voltage do not suck a whole a lot of current, so it will not drive VA and price for the transformer too much up. You can have one dedicated high voltage with filter and from it to power the driver stage AND bias. So, you will effectively have juts 3 transformers: filament, 220V and 440V. It is not to mention the PS for MF-DHT that you will do. I do not know what it will be. It would be nice to have your DHT to be driver by Milq’s driver but it allow would be nice to have a complete departure from Milg for MF and to have DHT driver for MF.
 
With all thing consider it is possible to make one large toroidal transformer to power all amps demands. Call to Maryland or Plitrone and they will give you a price. How affective would be sonically I do not know. 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-13-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 55
Post ID: 21861
Reply to: 21850
The power supplies
fiogf49gjkf0d
At this stage I am looking at running the two 440V supplies from separate secondaries of the same transformer and likewise for the two 240V supplies.  The guy that is making the transformers thinks this will be the most effective way for my particular scenario.  So all up that will make 3 power transformers (440V + 240V + DHT420V) and two filament transformers.  I will leave some room in there for later on just in case I want to add another DHT channel or two.

I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like.
08-13-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 56
Post ID: 21865
Reply to: 21861
How did you do it?
fiogf49gjkf0d
 anthony wrote:
I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

Hm, it is depends how stupid you are. The 3000uF is an average level of stupidity. In my amp I went for 36000 I believe that was accessibly stupid. In some amp DIYers make SETs with 8uF that is unsufficiently stupid. It is about how much you wiling your transformers, chokes and the rest PS and filter to be impactful to sound. Some folks make vintage tube rectification, use super-duper components in filtration and use very small last cap of a special type, let say paper in oil… Then the sound of the amp is 50% of the sound of PS. I do not say that it is bad and with proper tweaking all of it you can get fine result. I do not like this approach and I prefer to use large electrolytic to cancel out any sonic PS contribution. In my amp it is not about the contributive sound of passive elements but rather about unadulterated sound of active elements. Use the filtration to drive ripples to let say 1-3mMv and it would be good start.
 anthony wrote:
On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like. 

It is nice to hear BUT: if you heard the Tax's installation then how you concluded that sound you heard was result of “good Melquiades” but not the result of Tax’s heavily modified AG horn system? What I am asking is how you in the sound that you heard you were able to attribute what you liked to the amps but not to numerous other aspects?


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-13-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 57
Post ID: 21872
Reply to: 21865
Two things I really liked...
fiogf49gjkf0d
 Romy the Cat wrote:
 anthony wrote:
I am not sure how large to make the filter caps for the DHT channel.  At this stage I think I will start at 3000uF and perhaps try altering it a little up or down once the system is stable.

Hm, it is depends how stupid you are. The 3000uF is an average level of stupidity. In my amp I went for 36000 I believe that was accessibly stupid. In some amp DIYers make SETs with 8uF that is unsufficiently stupid. It is about how much you wiling your transformers, chokes and the rest PS and filter to be impactful to sound. Some folks make vintage tube rectification, use super-duper components in filtration and use very small last cap of a special type, let say paper in oil… Then the sound of the amp is 50% of the sound of PS. I do not say that it is bad and with proper tweaking all of it you can get fine result. I do not like this approach and I prefer to use large electrolytic to cancel out any sonic PS contribution. In my amp it is not about the contributive sound of passive elements but rather about unadulterated sound of active elements. Use the filtration to drive ripples to let say 1-3mMv and it would be good start.


When I read your text above I instantly realised that the '3000uF' filtering caps that I was talking about were for the two single stage channels and not the DHT channel.  In your DSET schematic you use a 8000uF filter cap that shares the load for three first stages and the entire DHT channel, so perhaps a value around there is a better place to start.  Driving the ripples as you suggest is what I will do.  For a power supply that is driving the DHT channel alone, would you stick with one large filter cap or would you go for multiples of say 1000uF?


 Romy the Cat wrote:

 anthony wrote:
On another point, I got to Sydney a couple of weeks ago and listened to Tax's 'Koshka' Melquiades running a heavily modified AG horn system.  I did enjoy my visit and am now quite confident that the Melquiades will suit my objectives.  Of course this is a few hours listening in a new room but I heard a lot of things that I like. 

It is nice to hear BUT: if you heard the Tax's installation then how you concluded that sound you heard was result of “good Melquiades” but not the result of Tax’s heavily modified AG horn system? What I am asking is how you in the sound that you heard you were able to attribute what you liked to the amps but not to numerous other aspects?


Although Tax has tuned his system to his tastes which are close but do not _exactly_ align with mine the system was capable of playing many genres of music which tells me that it was not a one-trick-pony tuned for a particular 'sound'.  This system-wide determination reflects on the amplifiers as well, because I have heard several SET amps that blatantly impart their signature on the music from all genres particularly when used on lower sensitivity speakers (which Taxes are not).  I don't want to hear the same sounds in all my music and I did not get that from Tax's system even though there were a couple of 'tunings' that I would like to do to align it properly with my tastes.

My biggest take home from the visit was the systems ability to swing in a balanced and cohesive way.  The night before I had been to see Bruckners Eighth at the Sydney Opera House and as you are well aware this piece has large swings in which it seems as though the entire orchestra must throw caution to the wind and just 'do'.  Even in the systems that I have enjoyed there always seems to be a 'compression' with these large swings, and this compression seems to be mostly influenced by the amplifier (and sometimes the source) that is driving the speakers, whatever they may be.  With Tax's system the swing from light to dark to light and the way that it handled the transients in general was always composed and balanced and comparatively non-compressed.  The fact that these transients were handled so well even with Tax's midrange that is a little 'heavy' or 'dark' for me tells me that the amplifier in use is very capable indeed. 

10-18-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 58
Post ID: 22101
Reply to: 21693
Splitting the DSET
fiogf49gjkf0d

So I am currently working towards this concept for my Macondo (see below) and I have just the Upperbass horns left to turn and prep. 
 My Macondo 1.jpg

My Macondo 2.jpg
I am thinking about how to best integrate the DSET with Macondo and have come up with something like this…

My Macondo Aerial 1.jpg

Perhaps it will be possible to build the amplifiers as part of the frame of Macondo and then package the power supplies so that they will fit under the Upperbass Horn.  This will hide them from view and reduce the footprint of the entire audio system in the room. 
Romy, the thing that worries most is heat.  I am concerned that the 6C33C’s and other tubes will cause the drivers above to warm too much if I snuggle the tubes in too close to the frame and I am hoping for your input here.  Are you able to give some indication from your experience with this gear?

I thought that I would set the amplifier section on a platform to the inside of the horn stack (because the bass will go on the outside of the stack, and run cables from the hidden away power supply up to the platform.  Some effective vibration isolation will be installed for both the power supply and the amplifier.

With this arrangement I could hard-wire the speaker cables and the only cables in or out would be a power cord and the interconnects.
I had also thought about splitting the amplifier section into three as follows:  6C33C x 3 Channels down with the power supply;  DHT channel right next to the MF horn;  two single stage channels up high next to their drivers.  However I thought it best to have the crossovering all in one place.  A split amplifier section would require setting up two more bias supplies but I am sure that is achieveable. 
 

Regards, 

 
Anthony
 
10-18-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 59
Post ID: 22104
Reply to: 22101
I do wish you to come up with something in this direction.
fiogf49gjkf0d
Anthony, yes, it is a perfectly legitimate question and I asked myself this question many times. I do think that if you make horn from wood then heat will damage them but if your upper bass horn is from concrete  (like Jessy did) then it does open some possibility. I did not do anything in this direction. As a partial consideration of the subject you might consider to locate the binding post on the amp on a very strategic side to accommodate the location of the horns. There are cons and pros for this solution as you would never know what life prepared to you and where yoou will be moving to a new listening room.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
10-20-2015 Post does not mapped to Knowledge Tree
anthony
Posts 186
Joined on 08-18-2014

Post #: 60
Post ID: 22136
Reply to: 22104
The heat issue
fiogf49gjkf0d
I am certainly looking into an integrated solution.  The first thing that I need to do is determine a safe distance to keep those 6C33C's from the wood or drivers.  I have listened to Tax's fullrange Melquiades once but was not thinking at the time about the proximity to other things as I am now, otherwise I would have made my experiments at that time.  I am still waiting on some final parts to arrive before I build a fullrange Melquiades myself.  In the meantime it would be nice to decide if this could be implemented or not and whether the idea should be dropped.

Romy, are you able to give me some advice on what you think is a safe horizontal separation between 6C33C and the timber?  It would be much appreciated.  Perhaps just use your hand and estimate what you think would be a safe distance so as not to disturb paint or make something too hot in general.  Or perhaps use a thermometer or temperature sensor on your multimeter to get some idea of the temperature gradient from the valves.

I will give Tax a call and ask the same of him, but of course he is just running a single 6C33C.

Regards,

Anthony
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