Its just a thought, something to think about..
If the amplifier-speaker integration were to be satisfied with 7W Class A PP, some of the demands placed on the driver could be reduced by using an output stage which biases closer to -45V. (2A3)
Driven by 2k Rp type DHT at ~25mA+ through 1:0.5+0.5 IT; low drive impedance, plenty of current, 90Vp-p required for full output, A2 no problem on peaks.
If the amplifier-speaker integration were to be satisfied with 7W Class A PP, some of the demands placed on the driver could be reduced by using an output stage which biases closer to -45V. (2A3)
Driven by 2k Rp type DHT at ~25mA+ through 1:0.5+0.5 IT; low drive impedance, plenty of current, 90Vp-p required for full output, A2 no problem on peaks.
Lynn,
I hate to even throw this into the discussion, but what do you think of Tubelab George's PowerDrive circuit, using a FET follower to drive the grid of the DHT output?
Power Drive | Tubelab
Ouch. Reading comprehension fail. I'll try again, this time with the question asked.
My experience with parallel feed is the coupling (or bypass, depending on how you look at it) cap has to be quite large to avoid LF resonances with the transformer. By "large" I mean 4.7uF or larger. I tried smaller values, no luck, the LF peak appeared, and I tried many different transformers with different values of inductance, and never was able to use less than 1uF.
That might have been workable except for one thing: for reasons I don't understand, the transformer/cap combination magnified the cap coloration. Each cap sounded different ... very different ... and none sounded neutral or even musically agreeable. I tried a lot of caps, and didn't like the sound of any of them.
After a month of futzing with the circuit, I gave up. It just wasn't worth it. Every variation stunk (a technical term for a failure), and the sound certainly wasn't better than plain old RC coupling, or even a funky phase-inverter tube.
For some reason, RC coupling seems to work OK at low levels (linestage etc.) provided the cap is reasonably coloration-free. I didn't have any luck with metallized caps of any variety, and the film-and-foils were pretty variable. The old-school caps were the best at retaining tone color while performing acceptably spec-wise.
At higher levels (driver), RC coupling starts to affect dynamics, slightly flattening them. This is to be expected with much of the tube's current doing nothing more than drive a plate-load resistor, instead of providing grid-drive as necessary. Arthur Loesch and I agreed that the grid of DHT power tubes seems to accept current in a somewhat nonlinear way, and the driver has to overcome this characteristic. This works against RC coupling at the driver/power tube level.
Changing topics, Gary Pimm measured a lot of DHTs and IDHTs, and regrettably, old-stock 2A3's are not one of the better ones. The 5th-and-higher harmonics were 10 to 20 dB higher than an old-stock 45 or new-model 300B.
We didn't measure the most recent Chinese single-plate models, which resemble 300B's with a 2.5V filament, so have no idea if they are better or not. A close examination of specifications shows a tube more like a derated 300B than a 2A3, so maybe they're in a transitional class of their own.
Subjectively, I'm not a fan of the 2A3 sound, so I wouldn't want to use it in my amplifier. I like 45's and 300B's very much, but haven't heard much in the way of 71A's.
Thats exactly where I would be looking, too.
JJ 40W '2A3' is much like the above except for not being made in PRC. Compares favourably with all manner of 2A3 IME and you can bias them a little deeper and run them a bit hotter if required.
71A is terrible tube, use 45 ;-)
So the new-production "2A3's" are basically low-emission 300B's with 2.5V filaments. The reason I mention low emission is my Tektronix friend Matt Kamna measured some early Chinese 300B's and found that some brands saturated the filament emitter around 100~150 mA or so ... while a real 300B can turn on much harder.
If the plate structure of these new "2A3's" is the same as a basic economy version of the 300B, we can safely guess they really are 300B's with a 2.5V filament, so they sit in a middle ground between the two.
Of course, Emission Labs and similar Czech "300B's" have much larger plate structures and far more emission than an actual Western Electric 300B, which really does run out of steam if you try and bias it at more than 65~70 mA. The originals get very hard and glassy sounding if you try and run them much beyond the WE-recommended 60 mA current.
By contrast, the high-performance Czech tubes are barely awake at 60 mA, and sound dull and slow. At 75~85 mA, they come into their element, and sound really good. So they're really 450B's, although nobody is going to call them that. There's not any equivalent in the old-stock catalog for these new tubes; the 845 operates at far higher voltages, and has much more extreme drive requirements.
I'm going to consult my transformer-building friends and ask if an accurately-balanced high-level SE -> PP interstage transformer is as difficult as I've been led to believe. Conventional PP -> PP interstages are not easy; they operate at substantially higher impedances than PP output transformers (the secondary is effectively open-circuit), and this works against good bandwidth.
If the plate structure of these new "2A3's" is the same as a basic economy version of the 300B, we can safely guess they really are 300B's with a 2.5V filament, so they sit in a middle ground between the two.
Of course, Emission Labs and similar Czech "300B's" have much larger plate structures and far more emission than an actual Western Electric 300B, which really does run out of steam if you try and bias it at more than 65~70 mA. The originals get very hard and glassy sounding if you try and run them much beyond the WE-recommended 60 mA current.
By contrast, the high-performance Czech tubes are barely awake at 60 mA, and sound dull and slow. At 75~85 mA, they come into their element, and sound really good. So they're really 450B's, although nobody is going to call them that. There's not any equivalent in the old-stock catalog for these new tubes; the 845 operates at far higher voltages, and has much more extreme drive requirements.
I'm going to consult my transformer-building friends and ask if an accurately-balanced high-level SE -> PP interstage transformer is as difficult as I've been led to believe. Conventional PP -> PP interstages are not easy; they operate at substantially higher impedances than PP output transformers (the secondary is effectively open-circuit), and this works against good bandwidth.
My feeling is that if you're going to use a MOSFET follower, why bother with the expense and hassle of a DHT power tube (and output transformer and filament circuit) at all? Just add another MOSFET as a pull-down current-source (and a huge heat-sink) and you get a Nelson Pass Class A amplifier.
Not being snarky or anything, but what is the contribution of the power tube in the PowerDrive circuit, except to add distortion? Why not cap-couple the speaker directly to the MOSFET, or if you want to throw money at it, through a custom-made low-impedance SE output transformer? If you used a special high-current SE transformer with a low turns ratio, the MOSFET current-source pull-down wouldn't even be necessary.
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Hmmmm.... From what I was taught, not a good something. Jean Hiraga usually said to use a pentode to drive a triode or a triode to drive a pentode, because their spectra compliment each other. Using like tubes tends to pile up too much of the same thing.
He certainly achieved good results that way.
I remember a P-P 300B project Mr Hiraga brought to the shop one day. It did not sound exactly like his SET 300B amps - similar, but not the same. It was a little fuller, not quite a clean. Nice amp to be sure, and with more power than the SE. Very pleasant to listen to. Wish I could remember the topology or even the drive tubes.
not quite sure what to make of this thread. when it started it looked like the goal was a dipole with a large coax on top, inspired by the active examples only this time a passive one was a goal, and with large format drivers/baffle for a lower wattage amp to drive them. (not quite sure why "the singular" (amp) was a must when digital bi-amp and hybrid active/passive solutions are so easy to get nowdays 
).
then this was given up for the fear of no bass?, yet Lynn later heard the Hologram which exactly fit the initial description and was able to rock a house with 20W/ch?
on the other hand here is a theatre scale solution with how many liters of volume by now (100, 200?), and what, a 4-way with a large CD needing a super tweeter on top, and a sub under a 15inch mid? at least Geddes did something appreciable and new and stretched a single 1inch CD low, and used a custom horn and a large mid with a deep cone so the dispersions matched at XO point, BUT the overall speaker kept a very small footprint!
where Ariel struck a cord with the mainstream DIY user, building up a theatre (like Harman or Klipsch does) is bound to have a very small following.
so Ok, one can get a lot of bass out of a huge volume, one can get the overall sensitivity high with tons of radiating surface, great dynamics with a CD and its directivity can be controlled with a horn, and.... not to stir the pot but please what is really new here
??
).then this was given up for the fear of no bass?, yet Lynn later heard the Hologram which exactly fit the initial description and was able to rock a house with 20W/ch?
on the other hand here is a theatre scale solution with how many liters of volume by now (100, 200?), and what, a 4-way with a large CD needing a super tweeter on top, and a sub under a 15inch mid? at least Geddes did something appreciable and new and stretched a single 1inch CD low, and used a custom horn and a large mid with a deep cone so the dispersions matched at XO point, BUT the overall speaker kept a very small footprint!
where Ariel struck a cord with the mainstream DIY user, building up a theatre (like Harman or Klipsch does) is bound to have a very small following.
so Ok, one can get a lot of bass out of a huge volume, one can get the overall sensitivity high with tons of radiating surface, great dynamics with a CD and its directivity can be controlled with a horn, and.... not to stir the pot but please what is really new here
??
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~~~~~~~~~~~~~~~~~~Big Snip~~~~~~~~~~~~~
so Ok, one can get a lot of bass out of a huge volume, one can get the overall sensitivity high with tons of radiating surface, great dynamics with a CD and its directivity can be controlled with a horn, and.... not to stir the pot but please what is really new here
Not to be a "Smart-Alec", but wasn't it King Solomon that said (nearly 2600 years ago) that "There is nothing new under the Sun." ? For Technology, that is certainly somewhat invalidated but it does retain a certain limited validity. Scientists that are exploring the cutting edge of science are, from time to time, bumping into papers that Nickola Tesla wrote a hundred years ago...
Best Regards,
TerryO
Deja Vue all over again
I'm a broken record - check my last post in this thread. Or Lynn's around the same time. Somewhere in first thousand posts or so this is discussed at length.
See #111 for example.
While you are at it, check out the background The Amity, Raven, and Aurora and Lynn's opinions on DACS
. (not quite sure why "the singular" (amp) was a must when digital bi-amp and hybrid active/passive solutions are so easy to get nowdays
I'm a broken record - check my last post in this thread. Or Lynn's around the same time. Somewhere in first thousand posts or so this is discussed at length.
See #111 for example.
While you are at it, check out the background The Amity, Raven, and Aurora and Lynn's opinions on DACS
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not quite sure what to make of this thread. when it started it looked like the goal was a dipole with a large coax on top, inspired by the active examples only this time a passive one was a goal, and with large format drivers/baffle for a lower wattage amp to drive them. (not quite sure why "the singular" (amp) was a must when digital bi-amp and hybrid active/passive solutions are so easy to get nowdays
then this was given up for the fear of no bass?, yet Lynn later heard the Hologram which exactly fit the initial description and was able to rock a house with 20W/ch?
on the other hand here is a theatre scale solution with how many liters of volume by now (100, 200?), and what, a 4-way with a large CD needing a super tweeter on top, and a sub under a 15inch mid? at least Geddes did something appreciable and new and stretched a single 1inch CD low, and used a custom horn and a large mid with a deep cone so the dispersions matched at XO point, BUT the overall speaker kept a very small footprint!
where Ariel struck a cord with the mainstream DIY user, building up a theatre (like Harman or Klipsch does) is bound to have a very small following.
so Ok, one can get a lot of bass out of a huge volume, one can get the overall sensitivity high with tons of radiating surface, great dynamics with a CD and its directivity can be controlled with a horn, and.... not to stir the pot but please what is really new here
yeah Lynn ..wtf?? you gave the finger (Ariels) than the arm (amity , raven , aurora ) than the leg (karma) why don't you give whats left and start sending out free speaker kits?? Myself I need a flat screen TV ,. Aren't you too old for that 60" plasma of yours ? Send it pronto to my flat please .
Hi Lynn,
What's the subjective difference between using 45s and 6V6s on the second stage in Karna Kay?
I said it earlier, but just in case it was missed, the 4P1L (a DHP that most triode strap, not unlike the 47) looks like another obvious choice to compare with the 45/46/6v6 choices for the driver stage. In the tube sub forum, these have grown recently quite popular likely due to Anatoly's nudge. Take a look at Ale's blog with curves and measurements. The distortion results are stunningly good, although no demonstration of the profile exists as far as I could see.
Bartola Valves | All about electronic valves and hi-fi
The beauty in my mind of these tubes is that they are cheap (cheaper than new production 6v6s even), plentiful, consistent and have close parameters to 45/46s (a bit higher gain). I haven't measured or used them yet myself, and I don't recall if the best operating points are close enough to your current circuit to be a good substitute.
The cheap and plentiful part makes it really nice when you need 4 closely matched tubes plus backups, as finding 4 old stock 45s that are closely matched these days requires deep pockets. I collected a bunch of 45s years back intending to embark on this project, but I didn't have great luck with finding good quads of them as some were quite noisy and others too far apart in condition. Another side benefit is that they are smaller than ST45s and especially globe 45s, so they don't take up as much real estate with their loctal profile. However, many might prefer the aesthetic of the old tubes.
Bartola Valves | All about electronic valves and hi-fi
The beauty in my mind of these tubes is that they are cheap (cheaper than new production 6v6s even), plentiful, consistent and have close parameters to 45/46s (a bit higher gain). I haven't measured or used them yet myself, and I don't recall if the best operating points are close enough to your current circuit to be a good substitute.
The cheap and plentiful part makes it really nice when you need 4 closely matched tubes plus backups, as finding 4 old stock 45s that are closely matched these days requires deep pockets. I collected a bunch of 45s years back intending to embark on this project, but I didn't have great luck with finding good quads of them as some were quite noisy and others too far apart in condition. Another side benefit is that they are smaller than ST45s and especially globe 45s, so they don't take up as much real estate with their loctal profile. However, many might prefer the aesthetic of the old tubes.
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SE Amp topology
Lynn, thanks for explaining why you think parallel feed amps fall short, and the issues associated with driving a 300B.
Volt Second created an Excel file which calculates how to design a capacitor and resistor in series with each other, but in parallel to the "parallel feed" capacitor, which takes care of the low frequency bump (I tried to attach this file, but could not figure out how). This allows for using smaller, and better quality parallel feed capacitors - and the second paralleled capacitor can be a very high quality capacitor which helps to improve on the parallel feed capacitor. In my amp, I high pass the signal from the SE amps (@150 hz using a Teflon coupling capacitor), so I use a smaller, and better quality film parallel feed capacitor (i.e., Rel polystyrene) which may take care of the quality issues of the large parallel feed capacitor, bypassed with a Teflon cap of course to address the hump. In my amp, the permalloy parallel feed transformer is wired as an autoformer, and the parallel feed cap "complex" is downstream of the transformer from the output tube's plate - a couple of additional improvements. You just can't do some of this stuff with series feed transformers.
Your comments about needing have a driver tube with sufficient drive for DHT tubes, particularly the 300B, is duly noted and I have heard that said by others (the 300B tube comes alive when driven correctly). I know that John Tucker designed and was using a 6N1P (7 ma current) which is shunt voltage regulated with a CCS (I don't know what he is using now) - I bought a kit from him to do that with my amps someday when I set up my main system again. My current SE amps use a 6SL7 JAN (a sweet tube) which is CCS loaded, but only drawing 2 ma. Maybe I can get by with this OK because I use these amps with efficient Lowther drivers and the demand on the amps is limited (above 150 hz, and 1 watt or less).
Pano, I see that you are skeptical of using DHT as drivers for the 300B. Andy Evans experimented with a lot of tube combinations and he found that two stages of DHT tubes was the best way to drive a 300B. I think that he was using two stages of the 10Y DHT, or something like that. I intend on trying other options and may end up with DHT as drivers in the end.
Lynn, the Karna Kay amp looks really interesting and I may try to build it someday, although it requires a big investment in tubes. I would like to build a version of S. Bench's OTL amp which uses inverted 5687 tubes (inverted 5687 tubes are very linear) - again a very interesting design and a good match for 15 ohm Lowthers. At the very least, I would have one of the few of these amp designs in the world (maybe the only one as I believe that S. Bench dismantled his).
Lynn, thanks for explaining why you think parallel feed amps fall short, and the issues associated with driving a 300B.
Volt Second created an Excel file which calculates how to design a capacitor and resistor in series with each other, but in parallel to the "parallel feed" capacitor, which takes care of the low frequency bump (I tried to attach this file, but could not figure out how). This allows for using smaller, and better quality parallel feed capacitors - and the second paralleled capacitor can be a very high quality capacitor which helps to improve on the parallel feed capacitor. In my amp, I high pass the signal from the SE amps (@150 hz using a Teflon coupling capacitor), so I use a smaller, and better quality film parallel feed capacitor (i.e., Rel polystyrene) which may take care of the quality issues of the large parallel feed capacitor, bypassed with a Teflon cap of course to address the hump. In my amp, the permalloy parallel feed transformer is wired as an autoformer, and the parallel feed cap "complex" is downstream of the transformer from the output tube's plate - a couple of additional improvements. You just can't do some of this stuff with series feed transformers.
Your comments about needing have a driver tube with sufficient drive for DHT tubes, particularly the 300B, is duly noted and I have heard that said by others (the 300B tube comes alive when driven correctly). I know that John Tucker designed and was using a 6N1P (7 ma current) which is shunt voltage regulated with a CCS (I don't know what he is using now) - I bought a kit from him to do that with my amps someday when I set up my main system again. My current SE amps use a 6SL7 JAN (a sweet tube) which is CCS loaded, but only drawing 2 ma. Maybe I can get by with this OK because I use these amps with efficient Lowther drivers and the demand on the amps is limited (above 150 hz, and 1 watt or less).
Pano, I see that you are skeptical of using DHT as drivers for the 300B. Andy Evans experimented with a lot of tube combinations and he found that two stages of DHT tubes was the best way to drive a 300B. I think that he was using two stages of the 10Y DHT, or something like that. I intend on trying other options and may end up with DHT as drivers in the end.
Lynn, the Karna Kay amp looks really interesting and I may try to build it someday, although it requires a big investment in tubes. I would like to build a version of S. Bench's OTL amp which uses inverted 5687 tubes (inverted 5687 tubes are very linear) - again a very interesting design and a good match for 15 ohm Lowthers. At the very least, I would have one of the few of these amp designs in the world (maybe the only one as I believe that S. Bench dismantled his).
Why not active and capaitors
A nuanced answer:
A multi-way system is a system where the different frequency regions have to be balanced, not only in frequency response (on-axis, first reflections between to 8 ms, clarity range to 40 ms, total range; with a downward slope above 1 - 2 kHz that is 0 for the direct sound on the listening axis and drops more for the longer integration times), but also in micro- and macro-dynamics.
A balance that slightly shifts with the loudness of the musical passage is something that the hearing system does not mask or can adapt to.
In a multi-amplification system the characteristics of the bass midrange driver + ampfier and the treble driver + amplifier have to be balanced on the above aspects. In Lynn and Gary their system the bass-midrange driver and compression driver-horn are already chosen to be very well balanced on the above aspects (I presume). So the obvious solution for multi-amplification is to use exactly the same amplifiers for bas-midrange and treble. Since one does not want to add extra active circuitry to avoid extra coloration or decrease in transparency or dynamics, one should use the power amplifiers as active element in the sallen-key configuration.
This is a configuration of an active system that has a good probability to achieve the same integration and sound quality. Most other configurations have a low probability (this is not zero probability: so this still means one could be lucky or one could try a large number of combinations until one is found that sounds the same).
(Small note: If one listens only to digital files, one can also do the filtering in the digital domain and additionally double the number of DACs and double the number of (passive or active) pre-amplifier channels. This seems less cost-effective).
What could be gained by going active this way (doubling the amount of amplifiers: Karna Kay or Reichert):
- On the amplification level: improvements can be had where the presence of low frequencies can influence the amplification of high frequencies; think power supply voltage, non-linear capacitance or gain, changing characteristics ifo dissipation. Thus looking into the concept of the Karna Kay and Reichert: very little. Only the tiny colorations from the coupling capacitors and power supply capacitors will diminish.
- For the filter components: the same quality capacitors are cheaper for the smaller values in the active filtering (and there is more choice such as metal foil/polystyrene).
On the subject of coupling capacitors and their sound:
The great inspiration for Jean Hiraga, mr. Tanaka went a great length optimizing this, see the last schematic in Visite chez un audiophile Japonais, Mr Tanaka (1977)
TriodeDick eventually settled on Audio Note Cu foil, their dielectric film has recently changed to mica.
Off topic whilst I mention Jean Hiraga and Triode Dick: in 2013 they visited together Germany to listen to a 5-way horn system with Goto drivers. Goto hoornluidsprekers
The postscript says that at a later visit to TriodeDick, Jean Hiraga told him that after having heard the German system he did not want to listen to his home system for a few weeks. He felt to have been on the wrong track and needed time to start from scratch again. Triggers my curiosity.
A nuanced answer:
A multi-way system is a system where the different frequency regions have to be balanced, not only in frequency response (on-axis, first reflections between to 8 ms, clarity range to 40 ms, total range; with a downward slope above 1 - 2 kHz that is 0 for the direct sound on the listening axis and drops more for the longer integration times), but also in micro- and macro-dynamics.
A balance that slightly shifts with the loudness of the musical passage is something that the hearing system does not mask or can adapt to.
In a multi-amplification system the characteristics of the bass midrange driver + ampfier and the treble driver + amplifier have to be balanced on the above aspects. In Lynn and Gary their system the bass-midrange driver and compression driver-horn are already chosen to be very well balanced on the above aspects (I presume). So the obvious solution for multi-amplification is to use exactly the same amplifiers for bas-midrange and treble. Since one does not want to add extra active circuitry to avoid extra coloration or decrease in transparency or dynamics, one should use the power amplifiers as active element in the sallen-key configuration.
This is a configuration of an active system that has a good probability to achieve the same integration and sound quality. Most other configurations have a low probability (this is not zero probability: so this still means one could be lucky or one could try a large number of combinations until one is found that sounds the same).
(Small note: If one listens only to digital files, one can also do the filtering in the digital domain and additionally double the number of DACs and double the number of (passive or active) pre-amplifier channels. This seems less cost-effective).
What could be gained by going active this way (doubling the amount of amplifiers: Karna Kay or Reichert):
- On the amplification level: improvements can be had where the presence of low frequencies can influence the amplification of high frequencies; think power supply voltage, non-linear capacitance or gain, changing characteristics ifo dissipation. Thus looking into the concept of the Karna Kay and Reichert: very little. Only the tiny colorations from the coupling capacitors and power supply capacitors will diminish.
- For the filter components: the same quality capacitors are cheaper for the smaller values in the active filtering (and there is more choice such as metal foil/polystyrene).
On the subject of coupling capacitors and their sound:
The great inspiration for Jean Hiraga, mr. Tanaka went a great length optimizing this, see the last schematic in Visite chez un audiophile Japonais, Mr Tanaka (1977)
TriodeDick eventually settled on Audio Note Cu foil, their dielectric film has recently changed to mica.
Off topic whilst I mention Jean Hiraga and Triode Dick: in 2013 they visited together Germany to listen to a 5-way horn system with Goto drivers. Goto hoornluidsprekers
The postscript says that at a later visit to TriodeDick, Jean Hiraga told him that after having heard the German system he did not want to listen to his home system for a few weeks. He felt to have been on the wrong track and needed time to start from scratch again. Triggers my curiosity.
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Should not compare Geddes speakers (which also require additional subs) to the BTA, two entirely different creatures. One is for profit and the other for personal use. Probably could care less about what others are looking for in his design, it's not for you.
One Karna = $35,000usd
Lynn and Gary's all analog should beat any active analog or digital for a fraction of the cost. It's complex enough without going active and appears to achieve the qualities they are seeking, sonic correctness. Which is the biggest reason this thread is as long as it is. To find just what is missing nirvana we must sometimes revisit our past to discover where the train derailed or got on the wrong track.
One Karna = $35,000usd
Lynn and Gary's all analog should beat any active analog or digital for a fraction of the cost. It's complex enough without going active and appears to achieve the qualities they are seeking, sonic correctness. Which is the biggest reason this thread is as long as it is. To find just what is missing nirvana we must sometimes revisit our past to discover where the train derailed or got on the wrong track.
4p1l is the best tube I've heard in SE with filament bias; it sounds very clean and detailed. However it has quite a bit of harmonics beyond the third, I'm not sure if it would be as clean as a 45 in PP driver. I'm pretty much relegating myself to new production 45s when it comes to finding a matched quad.
When building my 2a3pp a friend who made one for himself insisted on tube follower because he didn't like solid state. Then we made a side by side comparation and we both liked mosfet better.
You both must be from group B ....
If it's not a secret , what kind of output transformers Thom used in his Flesh & Blood 300B amps? I admit I made these amps several years ago trying to closely follow the original recipe just used custom OPT's since specified Tangos were unavailable anymore. A pair of basic ,plain vanilla Audio Note Quests crushed my mono's. I blamed the OPts but my friend measured them and said he had not seen such great measuring transformers..
re: the "no active" approach: well people here behave like they never read anything about amp-driver interaction through a passive XO inserted in between. it has been acknowledged that some of the best speakers are notorious loads.
re: the "no digital" approach: the EQ versatility and a huge choice of available filters have been overlooked. as for DACs the bits are way past being a perceivable issue and only a quality execution of the analog section merits attention. (should be easy to prove through blind testing)
re: the "tubes only" approach: even people who credit tube sound with some psycho-acoustic qualities end up proposing hybrid schemes with SS power buffers complementing on the low end (e.g. F4 amp). even Z.Z. formerly of Sonic Frontiers and a lifelong tube enthusiast is now making the "Tulip" amp for BFA in a similar topology, tubes for VAS and a fet output stage. or else one ends up building up a theater just to make it work.
>>but back to the main topic of the target speaker design: where can one see the polar plots for the end design on this thread? (even the Geddes speaker, here downplayed as a commercial effort, has that info published since it was considered one of the main design criteria).
re: the "no digital" approach: the EQ versatility and a huge choice of available filters have been overlooked. as for DACs the bits are way past being a perceivable issue and only a quality execution of the analog section merits attention. (should be easy to prove through blind testing)
re: the "tubes only" approach: even people who credit tube sound with some psycho-acoustic qualities end up proposing hybrid schemes with SS power buffers complementing on the low end (e.g. F4 amp). even Z.Z. formerly of Sonic Frontiers and a lifelong tube enthusiast is now making the "Tulip" amp for BFA in a similar topology, tubes for VAS and a fet output stage. or else one ends up building up a theater just to make it work.
>>but back to the main topic of the target speaker design: where can one see the polar plots for the end design on this thread? (even the Geddes speaker, here downplayed as a commercial effort, has that info published since it was considered one of the main design criteria).
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