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05-25-2015 Post does not mapped to Knowledge Tree
anthony
Posts 236
Joined on 08-18-2014

Post #: 1
Post ID: 21667
Reply to: 21667
Planning my DSET
fiogf49gjkf0d

Hi Romy,

I am planning my own DSET build.  I have based my speakers on your Macondo and am busy turning MDF horns in my spare time.  Once that is over I will move onto amplifiers.  I plan to build a fullrange Melquiades for a friend and then if that works out the DSET 6 or 7 channel version for myself.

Of course I have read the threads and am reasonably familiar with the evolution of DSET Melquiades in the context of your system but there are still a few questions.  The question at the front of my mind is the following hypothetical: 

“How would you proceed with another DSET build knowing what you know now?” 


If you are willing I would like to work through this in stages.  This is a project that will evolve with time as I build the speakers and move them into the new room.  Initially there will be 5 Channels:

Raal Lazy Ribbon - Direct Tube Drive
S2 into 400Hz tractrix
S2 into 250Hz tractrix
Fane 8M into 115Hz tractrix
Scanspeak 25W/8565-00 towers – 8 drivers each

Then, if the results are satisfactory and the final position of the speakers in the room permits I will experiment with:

K15/40 Midbass Horn
Injection Channel

A very familiar system to you indeed, and I hope you don’t mind me using it as my starting point.  I don’t want to spend a decade or two trying to develop a satisfying horn system from scratch so I am using your documented experiences to make a strong start so that with any luck and a measure of persistence my system is matured within a couple of years and I can let the whole diy thing pass for other endeavours. 


So, to start, I am unsure of a few things regarding the operation of your amps.

  • Bias adjustment in the first stages.  Looking at the final 6 Channel circuit diagram the bias for Channels A, B and C are all fixed and non-adjustable.  How do you manage the varying gain of the 6E5P tubes?
  • Gain structure.  What is the output from your pre-amp?  Mine is 1.5V RMS and 33 Ohm.  I am trying to get an idea about my required size for the 30K input resistor.
  •   ULF through the Scanspeak line array.  My calcs are that at 15W, the SPL at the listening chair would be about 98dB at 20Hz, and much higher at 100Hz.  This is loud enough for sure, but in your experience is the 6C33C/Scanspeak combination good near the amplifiers maximum power?  


Regards,

Anthony

05-26-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,623
Joined on 05-28-2004

Post #: 2
Post ID: 21668
Reply to: 21667
Answers....
fiogf49gjkf0d

 anthony wrote:
I plan to build a fullrange Melquiades for a friend and then if that works out the DSET 6 or 7 channel version for myself.

That is very good approach in my view. The problem is in this approach that you have to have high sensitively speakers that you would be able to use with that test full-range Milq. The behavior of the Full range Milq win this other speaker might be not the same as it would be with Milq.  So, generally I would suggest to have a Milq (or any other amp the you might like) to drive your particular acoustic system with all passive filtration and spend at least 6 month to feel comfortable in this configuration and to figure out your crossover strategy. (Or to develop new listening objectives and consequential frustrations). Then you can slowly to do DSET and line filtration.
 anthony wrote:
If you are willing I would like to work through this in stages.  This is a project that will evolve with time as I build the speakers and move them into the new room.  Initially there will be 5 Channels:
Raal Lazy Ribbon - Direct Tube Drive 
S2 into 400Hz tractrix
S2 into 250Hz tractrix
Fane 8M into 115Hz tractrix
Scanspeak 25W/8565-00 towers – 8 drivers each

Naturally I “endorse” this configuration and I think it might do very well. My only concern is that I feel that Raal Lazy Ribbon are a bit too wide and too midrangy for use above 12K. The standard Raal Lazy Ribbon drop 10dB at 6K that is not bad but if you made Alex to make the ribbon twice more narrow then it will have steeper drop and you have a bit more “punchier” HF with the lower filter order.  The standard Raal Lazy Ribbon as I understand are meant to be used in two-3 way acoustic system where tweeter is crossed at 2.5-3.5K, so you would need to run 3-rd or 4th order to get the result you want. BTW, I very much might be wrong about it but I do think that the narrower ribbon would be beneficial. Does it worth to pay to Alex extra for a custom job and to be able to get “some” improvement? I do not have the answer to this question.
 anthony wrote:
Bias adjustment in the first stages.  Looking at the final 6 Channel circuit diagram the bias for Channels A, B and C are all fixed and non-adjustable.  How do you manage the varying gain of the 6E5P tubes?

Yeas, there is no bias adjustment in this driver stage nether I see a need to do it. You need to adjust bias if it going away and in some other occasions but in this amp it is not necessary.  The amp is set to get 200V on the driver stage and it would mean approximately 4.3V in grid. Yes, some of the tubes have a few DB leas or more gain but you do not change “gain” by setting bias. If you have on place 190V or 210V it truly goes not make any difference. Keep neat 200V on place and near 15K load and it would be fine. Saying it I would like to note that nothing shall prevent you to add your own bias adjustment if you feel so. Just be informed that any dealing with bias line is supper affective to sound, in fact ever more then dealing with grid in my mind.  You might gain some questionable benefit by having bias fine-dialed but you would need to put a trimmer in the bias line. Well, I find it is to be at least debatable…
 anthony wrote:
Gain structure.  What is the output from your pre-amp?  Mine is 1.5V RMS and 33 Ohm.  I am trying to get an idea about my required size for the 30K input resistor.

My pream has no gain. My frontend have high output and can swing I believe 3.5V. I think Bidat at 0dB digital can push 5V but this would send the Milq grid to plate currents and you do not want to be there with indirect heating. You can calculate the gain of the amp. The driver has average of 33dB, +- a few DB. The output stage has I believe 3-4times. Then you need to subtract whatever you OPT consumes. You will not have a high gain with this amp as it is two stager. If you have a Macondo-like configuration and very large room (let sat over 800-1000 sq foot) and low output frond end and no active preamp then you will feel that you have not enough volume sometime.  The whole beauty of Milg that you have let say 4V in the input and to have the am on A1 you might run a wide range of the frond end, including high output.  The 30K input resistor is kind of less relevant in Milq DSET as the input impedance of other channels will screw all input impedance picture.
 
 anthony wrote:
ULF through the Scanspeak line array.  My calcs are that at 15W, the SPL at the listening chair would be about 98dB at 20Hz, and much higher at 100Hz.  This is loud enough for sure, but in your experience is the 6C33C/Scanspeak combination good near the amplifiers maximum power?  

You will be able to drive Scanspeak line array from Milq ONLY in case you have VERY small room, you are very lucky (as I was a few years back where the arrays were at active location of the room) and if it were not a full range but 18-22W LF only amp. Otherwise I would go for a different amp. It need o be said that it is very hard to prognosticate anything,


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-26-2015 Post does not mapped to Knowledge Tree
anthony
Posts 236
Joined on 08-18-2014

Post #: 3
Post ID: 21669
Reply to: 21668
Getting hold of Alex is not easy...
fiogf49gjkf0d
 Romy the Cat wrote:
 
That is very good approach in my view. The problem is in this approach that you have to have high sensitively speakers that you would be able to use with that test full-range Milq. The behavior of the Full range Milq win this other speaker might be not the same as it would be with Milq.  So, generally I would suggest to have a Milq (or any other amp the you might like) to drive your particular acoustic system with all passive filtration and spend at least 6 month to feel comfortable in this configuration and to figure out your crossover strategy. (Or to develop new listening objectives and consequential frustrations). Then you can slowly to do DSET and line filtration. 

I will have the fullrange Milq for a few months after it is built, so I had better be quick getting the system in some sort of shape in that time.

 Romy the Cat wrote:
My only concern is that I feel that Raal Lazy Ribbon are a bit too wide and too midrangy for use above 12K. The standard Raal Lazy Ribbon drop 10dB at 6K that is not bad but if you made Alex to make the ribbon twice more narrow then it will have steeper drop and you have a bit more “punchier” HF with the lower filter order.  The standard Raal Lazy Ribbon as I understand are meant to be used in two-3 way acoustic system where tweeter is crossed at 2.5-3.5K, so you would need to run 3-rd or 4th order to get the result you want. BTW, I very much might be wrong about it but I do think that the narrower ribbon would be beneficial. Does it worth to pay to Alex extra for a custom job and to be able to get “some” improvement? I do not have the answer to this question. 
  
I have tried to contact Alex a couple of times in the past six months with something similar to your suggestion in mind.  Both times he did not respond to my email so I figured that either I was too small a fish or that he was too busy.  Seeing no better HF option, I have recently ordered the Lazy Ribbons and I doubt that Raal would have started building them yet, but I have contacted the distributor in my country this morning to see if he is able to prompt Alex into a conversation with me about this.  We will see how it goes I suppose.  I certainly would prefer a ribbon that is dedicated to HF, but if I can't talk to the man I can't get anything special.

 Romy the Cat wrote:
Yeas, there is no bias adjustment in this driver stage nether I see a need to do it. You need to adjust bias if it going away and in some other occasions but in this amp it is not necessary.  The amp is set to get 200V on the driver stage and it would mean approximately 4.3V in grid. Yes, some of the tubes have a few DB leas or more gain but you do not change “gain” by setting bias. If you have on place 190V or 210V it truly goes not make any difference. Keep neat 200V on place and near 15K load and it would be fine. Saying it I would like to note that nothing shall prevent you to add your own bias adjustment if you feel so. Just be informed that any dealing with bias line is supper affective to sound, in fact ever more then dealing with grid in my mind.  You might gain some questionable benefit by having bias fine-dialed but you would need to put a trimmer in the bias line. Well, I find it is to be at least debatable…
  
Ok, thanks for this information.  I will follow your lead in this regard.  

 Romy the Cat wrote:
My pream has no gain. My frontend have high output and can swing I believe 3.5V. I think Bidat at 0dB digital can push 5V but this would send the Milq grid to plate currents and you do not want to be there with indirect heating. You can calculate the gain of the amp. The driver has average of 33dB, +- a few DB. The output stage has I believe 3-4times. Then you need to subtract whatever you OPT consumes. You will not have a high gain with this amp as it is two stager. If you have a Macondo-like configuration and very large room (let sat over 800-1000 sq foot) and low output frond end and no active preamp then you will feel that you have not enough volume sometime.  The whole beauty of Milg that you have let say 4V in the input and to have the am on A1 you might run a wide range of the frond end, including high output.  The 30K input resistor is kind of less relevant in Milq DSET as the input impedance of other channels will screw all input impedance picture.
 

I have talked to a fellow that has built the fullrange Milq and he has had issues with Milq gain in his system and had to dial up the gain from his preamp, which is why I asked the question here.  Looks like I may need more than 1.5V SE from my dac if your sources have at least 3.5V and your gain structure is well thought out.  My dac will give 2.7V balanced so perhaps I will need to look at a balanced input to the Milq.

 Romy the Cat wrote:
You will be able to drive Scanspeak line array from Milq ONLY in case you have VERY small room, you are very lucky (as I was a few years back where the arrays were at active location of the room) and if it were not a full range but 18-22W LF only amp. Otherwise I would go for a different amp. It need o be said that it is very hard to prognosticate anything,

My room is 285 sq ft (6.08m x 4.35m) with a vaulted ceiling (with the peak running along the long axis of the room).  It will be interesting to see where the horn stack ends up in the room and also where the bass array will be positioned.  I am not sure if this qualifies as a very small room, but it certainly is not large.
05-27-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,623
Joined on 05-28-2004

Post #: 4
Post ID: 21670
Reply to: 21669
A dangers zone?
fiogf49gjkf0d
Make the full-range and then you will see where you are. Still, I feel that for MF channels it is beneficial for do with a good DHT output stage instead of 6C33C and perhaps it is a good idea to use DHT driver as well. So, when you strategy your 5ch DSET do consider that you might want to do non-standard Milq for MF. The  Lazy Ribbon vs narrow  Lazy Ribbon… that is not a big deal. I would not spend too much effort to find Alex or whoever it might be. You might even chose to go for another tweeter if you would like, like some kind of exotic Japanese of not the contemporary cancroid type.  You cannot make the judgment of what you need as you do not know what kind MF amp will be driving your S2 and consequentially you do not know what tweeter will “work” for you. Remember, you do not chose the tweeter YOU like but rather you chose the tweeter that your MF channel loves. So, I would advise do not worry about the tweeter and build the system without it. Yes, you shall leave a room for it on your frame and you shall dedicate an amp to it but do not lock on the amp topology at this point as you do not know if you will be driving 16R or 0.0001R. About the amp gain – it is what it is. I do not think that 2.7V balanced will help you as converting it to single ended you will be losing the dBs. In realty I do not know what output voltages I have. I do know that with 0.5V I have a “normal” sound in my room that some people would consider too load. I think that friend of yours who has Milq sound too soft has ether too low efficiency of the acoustic system or too large room. In your case, if you have Milq driving the line away of 8 25W/8565-00 towers drivers in the room of near 300 sq and tall ceiling I would predict that you will be in a "dangers zone" and will be running out of gain.

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-27-2015 Post does not mapped to Knowledge Tree
anthony
Posts 236
Joined on 08-18-2014

Post #: 5
Post ID: 21672
Reply to: 21670
DHT in the DSET
fiogf49gjkf0d
 Romy the Cat wrote:
Make the full-range and then you will see where you are. Still, I feel that for MF channels it is beneficial for do with a good DHT output stage instead of 6C33C and perhaps it is a good idea to use DHT driver as well. So, when you strategy your 5ch DSET do consider that you might want to do non-standard Milq for MF. 

My interest is mainly in the 10Y/801A/VT25 tubes on one hand and the 45 on the other hand.  The YO186 also interests me a lot especially after reading your impressions of it in your circuit and system, but it is a very difficult tube to get a hold of and is quite expensive.  The 10Y etc. seem relatively reasonably priced and quite available, however I don't have a ready-made circuit or even knowledge of how they work with Macondo, so I am tempted to just follow your DHT lead with the 6E6P and DHT MF, especially considering that I don't want to be testing/developing amplifiers for much longer than I have to even if I may end up with a better result going the longer route.  

My primary concern about a DHT driver is the low gain of those tubes (10Y is about 8x compared to 6E5P of 32x) and having to use an input transformer to improve gain and its effect on the crossover for MF.   
 Romy the Cat wrote:
In your case, if you have Milq driving the line away of 8 25W/8565-00 towers drivers in the room of near 300 sq and tall ceiling I would predict that you will be in a "dangers zone" and will be running out of gain.

I thought I might be pushing the limit.  Do you think it would be possible to increase gain by using an input transformer on the DSET ULF channel to boost signal level?  I am not sure how this would mess with the low-pass filter.

Otherwise I could add a decent SS amp or maybe even push-pull 6C33C. 

Regards,

Anthony
05-28-2015 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,623
Joined on 05-28-2004

Post #: 6
Post ID: 21673
Reply to: 21672
You will see.
fiogf49gjkf0d
 anthony wrote:
My interest is mainly in the 10Y/801A/VT25 tubes on one hand and the 45 on the other hand.  The YO186 also interests me a lot especially after reading your impressions of it in your circuit and system, but it is a very difficult tube to get a hold of and is quite expensive.  The 10Y etc. seem relatively reasonably priced and quite available, however I don't have a ready-made circuit or even knowledge of how they work with Macondo, so I am tempted to just follow your DHT lead with the 6E6P and DHT MF, especially considering that I don't want to be testing/developing amplifiers for much longer than I have to even if I may end up with a better result going the longer route.  

There are tons of very cool DHT out there and for sure 10Y is one of them. Mind you that all “publicity” of good DHT come from full-range amplification and no one know how this particular DHT will behave with your specific drive in DSET configuration. I do hear your concern about you not wiling “to be testing/developing amplifiers for much longer than I have to”. That is VERY valid point.
 anthony wrote:
My primary concern about a DHT driver is the low gain of those tubes (10Y is about 8x compared to 6E5P of 32x) and having to use an input transformer to improve gain and its effect on the crossover for MF.

Well, do not discard the  3-stages topology for MF. You need to understand that 6E5P in a way unique for 2-stages scenario and no transformers, when you need a lot of gain and a lot of voltage on grid to keep the tube in class A. Pretend that you have some kind of 12AX7 at input, this tube 0.5V bios will be very fast flooded by input voltage and you will be obligated to rise the cathode on feedback.
 anthony wrote:
I thought I might be pushing the limit.  Do you think it would be possible to increase gain by using an input transformer on the DSET ULF channel to boost signal level?  I am not sure how this would