0 Members and 1 Guest are viewing this topic. Read 9699 times.
I have a amp ( firstwatt SIT2 ) that a reviewer says with a DHT pre in front of it, it takes it to the next level. When DHT amps, preamps, or DACs are mentioned the manufacture really plays up the DHT aspect of it. So why is it so great?
Directly Heated Triodes are often lauded as being the best in tube amplification. I don't have any experience ergo I have no opinion but I'm hoping some more members can chime in that have the knowledge you seek. I think it still comes down to the circuit and it's execution that makes and amp or preamp stand out in the crowd, whether it be DHT, IDHT, or even (gasp!) SS.Maybe if you get enough information you can make an educated purchase and find this audio nirvana.
The magic is not really the DHT, but directly heated triodes in a single ended configuration. These are simple circuits that do the least amount of damage to the signal. The distortion is mostly even order. When one plays an acoustic musical instrument, even order distortion is a product of that playing. That is why no two acoustic instruments sound the same. The natural overtones determine the sound, (pitch and timbre) of the instrument. Our ears/brains prefer even order harmonics. They are natural sounds.As the drive for more power made tubes more "complicated", (tetrode, pentode), the circuit to drive them became more complicated. Simply put, the more components to complete the circuit, the more damage to the music signal. DHT's were born in the acoustic music eras. That is what they do the best.Are DHT's special, yes, when matched to appropriate music. Cheers,Geary
... but if your scenario is correct, why is it possible to create a perfect in and out component using IDHTs? (By perfect in and out, I mean what comes out perfectly matches the input, via long listening testing.)
Simple. It is not possible. IMO there is no such thing as a "a perfect in and out component" That's marketing, not electronics or physics. Think "Perfect Sound Forever" and you will understand my perspective.Cheers,Geary
I can understand your opinion, and respect it; but it is based on false assumptions and poor designs, both DHT and IDHTs.Cheers
Pretty disingenuous comment. But it explains much.Cheers,Geary
Interesting. Well, as you mention, it is just your opinion. But IDHTs can be accurate in to out, but one better know how to actually design, not copy, and perform lots of listening tests, over years, with lots of friends, even customers.If you are using SETs with DHTs, or Idhts for that matter, as your basis, I can see your point though. For the general public, Dhts in SETs have 15-35% intermodulation distortion at higher powers. With SETs, the damping factor changes not only vs signal level (power), but between positive and negative halfs of the cycle. SETs, using any triode, require chokes, to reduce hum (120hz ripple). However, a choke alters the isolation between decouplingcapacitors vs frequency etc. Xl (choke inductive reactance) equation is 2pi x F x L. The inductive reactance between decoupling capacitors will vary over a thousand times from 20hz to 20khz.So the musical signal reaching the decoupling capacitor changes as the frequency changes. It is complex, phase angle changes, but in layman's language, think of the decoupling capacitor changing value, (only the phase angle changes differently).Output transformer distortion not only rises dramatically at lower frequencies, but low frequency response drops more as well. Thus the midrange is accentuated giving that "midrange magic". However, one can do that with any amp.Running DC filaments requires more parts in its cathode circuit, thus in the signal path, than IDHT tubes. AC, well.....DHT tubes need much more signal drive, thus higher orders of distortion from the driver tube, which passes through to the speakers. Besides that the driver distortion mixes with the output tube's distortion to create higher orders. Even orders mentioned only refers to the output tube. More stages, more parts, or an interstage transformer, are required, so more distortion, less bandwidth etc.Check the high frequency response of the DHT amps. 40khz at -3db is generally about it, though some are better. That means FR is down about -.2db at 10khz. Again this causes the "midrange magic" effect.Profit is another factor for DHTs. Around the year 1997, when I got into internet, DHTs were pushed heavily. A DHT tube costs are little more than IDHT tubes, while they were charging hundreds. Quite a profit there.I can see where "20 times" profit beats "5 times" profits for IDHT tubes. I can understand your opinion, and respect it; but it is based on false assumptions and poor designs, both DHT and IDHTs.Cheers
There is, in fact, a ocean of gray in this hobby and it is accepted that one must find one's own way through it. Some try to apply purely scientific means and some don't give a damn about specs and just follow their heart. Does that make them wrong? Should they not be allowed to enjoy their music in the way they best see fit?I would ask that you just make your opinion known and not tell others what theirs is based on. That is an assumption as well and this is where you continually ruffle feathers. And where the hell did anyone call you a liar? (Reference to Steve's PM to me.) Damned if I can find any reference to you being called a liar so help me out here.I've unlocked this thread to allow further responses as I'd like to hear from more DHT advocates, hopefully ones that describe the differences they hear between DHT and IDHT and any other topology they have experience with.
OK, to start with you fully recognize and state that it is galyons (Geary's) opinion you are responding to. Thus it is assumed you understand that along with opinion comes the understanding that not all audiophiles need or try to apply science to this hobby. You know full well that, as an engineer, there is much science in the design and build of an audio electronic device but as one that has been in this industry/hobby for as long as you have there is much that we still do not understand and that opens the door for belief to be applied. I'm sure you are also well aware that hearing is subjective as are the senses of smell and taste and that is something you have historically dismissed over science which is where the trouble starts.
Geary made his statements based on his experience same as you. Thus you should accept his opinion as we do yours, and not pick it apart.
So you state that all DHT SET designs have high intermodulate distortion. Show us with screen shots of actual oscilloscope measurements of a device currently available. You state that this IM distortion is at "higher power". Is the device being overdriven when this happens?
As far as interstage chokes vs coupling capacitors there are advantages and disadvantages using either in a design. This is well documented and discussed over the past 90 or so years of audio engineering.
I agree with Geary that there is no audio device yet invented that does not alter the output vs the input in some way, however minor and even impossible to measure.
I am not going to argue your statements about OPT having bass loss due to distortion or the high frequency roll off all contributing to the "magic midrange". Some people like that! This sector of audiophiles don't give a damn about a flat output response of 20 Hz -20 KHz, or 10 Hz - 100KHz. They just know what they like because their ears tell them that. I like spicy food but many people do not, does that give me the right to criticize their tastes? No.
I certainly won't argue the marketing and markups that this hobby is subjected to but that's the nature of the world. Caveat emptor. There are those that can afford $90K turntables and $100K speakers and that's what they like. Are they also basing their purchases and opinions on "false assumptions and poor designs"?
I would ask that you just make your opinion known and not tell others what theirs is based on. That is an assumption as well and this is where you continually ruffle feathers. And where the hell did anyone call you a liar? (Reference to Steve's PM to me.) Damned if I can find any reference to you being called a liar so help me out here.
As the original poster i'd like to say thanks for the replies. And i would like to comment that i recently changed the direction i am heading in the audio world and more "following my heart". My recent changes of less power, simpler component and high efficiency have made me really excited about the direction i am heading. Just curious about replacing a Shindo pre with a DHT pre because of a six moons review of my amp.
First, the subject was what went out is what came in. That requires listening testing which I clearly stated I performed to arrive at that conclusion, along with others who were tested. So we are not discussing subjective, but what went in came out exactly the same via listening tests.His reply: "Simple. It is not possible. IMO there is no such thing as a "a perfect in and out component" That's marketing, not electronics or physics."Everyone who has seen this has told me that I was called a liar and marketer. I am not. Let's let the viewers decide.After his insinuation that I am a liar and marketer, I presented science to back up my position.Read the RCA Radiotron Designers Handbook, written by 26 engineers, 1960, 1952, who have performed the measurements, third party. It has been known for decades that IM distortion is generally around 3.2 times the HD distortioin of triode tubes. At high power ratings for example, 5% HD equates to 15% IMD. 10% hd equates to 30% IMD. One can also check out Nelson Pass's article/data. Scroll down to "Intermodulation distortion" and learn about IMD with just 2nd and 3rd harmonics involved.https://passlabs.com/articles/audio-distortion-and-feedbackTotally different components. Capacitors have different sonics true. Hum control, and keeping B+ high for those huge signal swings is about the only advantages of a choke, . Then there are hysteresis problems, distortions because of R and XL combining, frequency dependent, resonances, both self and parts around. Please show one link explaining the pluses of a single choke?I stated via listening testing over years. I never mentioned measuring down to -140db.I never stated distortion created a loss of bass, although satuation of the core tends to limit deep bass response and distortion rises. The subject was that dhts are superior, according to FMR and Geary, not preferences. If Geary was concerned with preferences, he would have stated such. Instead Geary stated it was NOT possible to design a perfect in and out component via listening tests. Two very different subjects.Again, that is not the subject. The subject is the claim by some that dhts are superior, even in SETs? I provided evidence that they are not after Geary accused me of lying and marketing tatics. Read the first part of my reply. Every single one who I have shown this to in this building thought I was called a liar and marketer. That is why I responded with facts, not general insinuations. My apologies to those who think otherwise. By the way, the last guy I rubbed wrong with; did you know his "circuit" was simply a copied circuit from the 1960 RCA tube manual, tubes and all; but I tried to be nice? I also found out later that he was not only permanently banned from DIYAudio.com not once, but twice, for lying and deception and falsely claiming "his circuit" was his invention. He has also been kicked out of other forums. I thought I was helping to protect the public, by gently correcting him. I guess not. I won't help anymore, to say the least. Please accept my apology for any waves I have created. I hope I am not banned.
First, the subject was what went out is what came in. That requires listening testing which I clearly stated I performed to arrive at that conclusion, along with others who were tested. So we are not discussing subjective, but what went in came out exactly the same via listening tests.His reply: "Simple. It is not possible. IMO there is no such thing as a "a perfect in and out component" That's marketing, not electronics or physics."
Everyone who has seen this has told me that I was called a liar and marketer. I am not. Let's let the viewers decide.After his insinuation that I am a liar and marketer, I presented science to back up my position.Read the RCA Radiotron Designers Handbook, written by 26 engineers, 1960, 1952, who have performed the measurements, third party. It has been known for decades that IM distortion is generally around 3.2 times the HD distortioin of triode tubes. At high power ratings for example, 5% HD equates to 15% IMD. 10% hd equates to 30% IMD. One can also check out Nelson Pass's article/data. Scroll down to "Intermodulation distortion" and learn about IMD with just 2nd and 3rd harmonics involved.https://passlabs.com/articles/audio-distortion-and-feedback
Totally different components. Capacitors have different sonics true. Hum control, and keeping B+ high for those huge signal swings is about the only advantages of a choke, . Then there are hysteresis problems, distortions because of R and XL combining, frequency dependent, resonances, both self and parts around. Please show one link explaining the pluses of a single choke?I stated via listening testing over years. I never mentioned measuring down to -140db.I never stated distortion created a loss of bass, although satuation of the core tends to limit deep bass response and distortion rises.Quote from: Steve on 7 May 2014, 03:32 amOutput transformer distortion not only rises dramatically at lower frequencies, but low frequency response drops more as well. Thus the midrange is accentuated giving that "midrange magic". However, one can do that with any amp.
Output transformer distortion not only rises dramatically at lower frequencies, but low frequency response drops more as well. Thus the midrange is accentuated giving that "midrange magic". However, one can do that with any amp.
The subject was that dhts are superior, according to FMR and Geary, not preferences. If Geary was concerned with preferences, he would have stated such. Instead Geary stated it was NOT possible to design a perfect in and out component via listening tests. Two very different subjects.Again, that is not the subject. The subject is the claim by some that dhts are superior, even in SETs? I provided evidence that they are not after Geary accused me of lying and marketing tatics. Read the first part of my reply. Every single one who I have shown this to in this building thought I was called a liar and marketer. That is why I responded with facts, not general insinuations. My apologies to those who think otherwise.
By the way, the last guy I rubbed wrong with; did you know his "circuit" was simply a copied circuit from the 1960 RCA tube manual, tubes and all; but I tried to be nice? I also found out later that he was not only permanently banned from DIYAudio.com not once, but twice, for lying and deception and falsely claiming "his circuit" was his invention. He has also been kicked out of other forums.
I thought I was helping to protect the public, by gently correcting him. I guess not.
I won't help anymore, to say the least. Please accept my apology for any waves I have created. I hope I am not banned.
