Comments?
DECWARE / ZEN MYSTERY AMP model ZMA
Also, no negative feedback UL.Output impedancemust be pushing into current amp territory.
dave
DECWARE / ZEN MYSTERY AMP model ZMA
Also, no negative feedback UL.Output impedancemust be pushing into current amp territory.
dave
If I was paying even a quarter of that price I would expect a serious effort to have been made to hide all of the tube socket fixing screws! They also claim that individual tube bias adjustments allows the use of unmatched tubes. It doesn't. It allows tubes with different bias needs to be set to the same level of bias, but it does nothing to adjust for any differences in the slope of the curves. Matching of tubes would still be needed. So, persionally, I am not impressed by the marketing material.
Just my 2 cents... 🙂
Just my 2 cents... 🙂
This is sad. You need to develop a taste for "liquid honesty" (which is likely lifted from a whisky ad)
I particularly enjoyed the part where the absence of chokes was so convincingly explained with the addition of big caps.
Big caps, but only for a while. If they are where I think they are in the pictures, they will be very quickly cooked by their proximity to the output tubes... Once they have degraded sufficiently, the noise from the charging spikes will be no worse than many lower cost amplifiers. 😀
Much more affordable class A and you could use KT-66 tubes. Not 40W though, but for sure all class A.
K & K Audio - Lundahl Transformers, audio DIY kits and more
K & K Audio - Lundahl Transformers, audio DIY kits and more
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Read the rest of it carefully.
Somehow a vacuum tube regulator drops voltage without generating any heat....magic? "The first tube amp power supply in the world" with such design????
We have all seen voltage regulators of several kinds on these page. As far as I know ALL linear regulators will dissipate at least as much heat as the resistor they replace, UNLESS it is a switchmode regulator. A switcher will still dissipate heat, just less than the resistor it replaced. Yes, tube based switchers exist.....or existed. The TEK 504 scope used one.
I will go with George's 6L6GC AB2 route in triode mode. 40 something watts still with big chunk of money in your pocket.
Sidney
Sidney
According to published specs: +Ub = 410 V, Iidle = 40 - 60 mA,
this is unexceptional AB1-class amplifier.
this is unexceptional AB1-class amplifier.
Why dont you have a look at this?
OddWatt
Or if you want to diy these amps (which can use any tubes from kt66 to kt88)
OddBlocks - Class-A Push-Pull KT88 Tube Amplifier (12SL7 Driver)
You can build one that takes kt120 tubes but I am opting for the kt88 one (the difference being poer and OPT's for the kt120 version)
The oddblocks are simple and have a great forum for help
I am currently starting the build.
I went for these cause of ss rectification, and due to its unique topology very small parts count. Have a look at the square wave responses at bottom of page on the diyaudioprojects link. Class A PP. You wont get 40w out of kt66's, kt120's yes, kt150's too but then that ties you to one manufacturer so you cant roll tubes
Good luck
Nick
OddWatt
Or if you want to diy these amps (which can use any tubes from kt66 to kt88)
OddBlocks - Class-A Push-Pull KT88 Tube Amplifier (12SL7 Driver)
You can build one that takes kt120 tubes but I am opting for the kt88 one (the difference being poer and OPT's for the kt120 version)
The oddblocks are simple and have a great forum for help
I am currently starting the build.
I went for these cause of ss rectification, and due to its unique topology very small parts count. Have a look at the square wave responses at bottom of page on the diyaudioprojects link. Class A PP. You wont get 40w out of kt66's, kt120's yes, kt150's too but then that ties you to one manufacturer so you cant roll tubes
Good luck
Nick
To confirm, KT66s must be pushed to the limit to reliably give 40W/pair in class A. [And if I read one more time about "pure" class A @#%$! Their is nothing cleaner about class A than .... sorry; not to start something off topic.]
This more the region of 6L6GCs or the less efficient KT88s - but that is another story.
This more the region of 6L6GCs or the less efficient KT88s - but that is another story.
At one stage he claimed to be using a gas voltage stabiliser but in series, so that 'none of the ripple gets through'. Not an exact quote but lifted directly from another amp that he was making which was using two SE OPT for a PP output stage (where my interest came from - and still does).
I thought the "Doc" was one of the good guys? He is an early proponent of the DIY movement, so why all the hate? Besides well known for the "creative" ad copies, does he know how to design amplifiers or not (besides the Mystery, since no schematic is available)?
Jazbo8,
Regarding myself, I made my comments purely on what was mentioned in this thread - no personal offence uttered or intended (I do not know the inventor from Adam). Surely some of the things mentioned by himself and referred to others cause doubt to say the least? That is basic electronics!
Ceglar,
Both have been tested - the face-palm often at myself. Mercifully not observed by others, but the ego took a jolt every time.... 😱
The amplifier: A class A UL output topology using 43% UL taps: The almost identical 6L6GC cannot do that unless at an h.t. of 500V and dissipating 35W. (That was calculated and tested.) But the total dissipation rating for a 6L6GC is 33W, for a KT66 only 27W (although one source says 33W ... at what ambient?). That is taking the OPT efficiency at a high 90%; it hardly ever is.
These days one reads about 'special ruggedised' versions with higher maximum ratings etc. - should that be used in this amplifier .... But such are promotional claims. I go by ratings published by GEC, RCA and such.
The other mentioned practices ... [facepalm] again.
Regarding myself, I made my comments purely on what was mentioned in this thread - no personal offence uttered or intended (I do not know the inventor from Adam). Surely some of the things mentioned by himself and referred to others cause doubt to say the least? That is basic electronics!
Ceglar,
Both have been tested - the face-palm often at myself. Mercifully not observed by others, but the ego took a jolt every time.... 😱
The amplifier: A class A UL output topology using 43% UL taps: The almost identical 6L6GC cannot do that unless at an h.t. of 500V and dissipating 35W. (That was calculated and tested.) But the total dissipation rating for a 6L6GC is 33W, for a KT66 only 27W (although one source says 33W ... at what ambient?). That is taking the OPT efficiency at a high 90%; it hardly ever is.
These days one reads about 'special ruggedised' versions with higher maximum ratings etc. - should that be used in this amplifier .... But such are promotional claims. I go by ratings published by GEC, RCA and such.
The other mentioned practices ... [facepalm] again.
Supporting the DiY movement was a good thing. Selling snake oil to gullible audiophools is a very bad thing. Promoting pure ignorance is not good. And he is right up there with those con men who sell the magic stones, the "miracle" goop that you smear on ICs and transistors to make them sound like VTs, the magic cables etc, ad infinitum, ad nauseum.
I would say not, based on what he describes here: Zen TORII
I'd say this is a very dangerous piece of equipment. What if you disappear and don't come back? 😕 😱 😀
How can there possibly be a "measurable vacuum gap" when he's discussing GAS regulator tubes? What he's written here is either pure ignorance or pure bovine excrement. Either way, it's unforgivable. If you have a gas regulator connected in series with a load, and you have ripple and/or voltage fluxuation, where does it go if the voltage across the regulator tube can not change? It shoots right through and appears across the load. There is no other place for it to go, and last I heard, Kirchoff's Laws had not been repealed.
He is either lying like a Persian rug, or he is ignorant of a very basic fact of electronics and is hoping you don't understand this. I'd like to see the actual schemo to see if he really did connect the VR tubes in series, or if it's an actual voltage regulator of some sort.
I don't keep up with "who's who" in the audio business, or even pay attention to other peoples amp designs....I don't know DEC or "Doc" from jack.....
I do know and understand electronics and vacuum tubes. I do know that if you drop voltage across a linear device, be it a resistor, a vacuum tube including a VR tube, a semiconductor, or a piece of Kryptonite, there will be heat dissipated. The amount of heat will be the product of the voltage across the device times the current through it, plus any added dissipation from additional support circuitry like tube heaters. No amount of ad copy can repeal Ohms law.
This practice will exist in every industry as long as there are willing customers to buy it....Look at all the fat busting pills pushed on TV....Same difference...there is an app for that, it's called the delete button.
I tried this (Miles is right), AND it has been used commercially before. Look at the schematic of a vintage Allen Organ amplifier in post #4 of this thread:
http://www.diyaudio.com/forums/instruments-amps/253049-new-project-big-bass-amp-4x6l6.html
There is an 0C3 in series with the screen supply to drop the B+ since the metal 6L6's used in this amp can only eat about 300 volts on the screens.
The theoretical limit of efficiency of a class A amplifier is 50%. I have achieved 45% with a tube amp, but I used an 845 and deep A2 to get there. A 6L6 type will usually achieve 30 percent due to the high plate to cathode saturation voltage. I have little experience with the KT66, and they were Chinese, maybe they do better.
If we assume the more generous 33 watt per tube plate dissipation rating (66 watts for a pair), we can stuff 66 watts of DC into a pair of tubes at idle, putting the tubes at 100% of their maximum rating. This is not recommended, 75 to 80% is more like it, but lets go with 100%. If this amp is then pushed to 40 watts output, the tubes must still draw the same average current as at idle (definition of class A). So 66 watts input gives us 40 watts of audio output, for an efficiency of 61% (theoretical maximum is 50%).....You can't get there from here!
The spec sheet shows 410 volts and 60 mA max per tube..... Thats 50 watts input for 40 watts output.....not possible in class A, the current must be increasing as the power goes up, which is class AB.
You are not in class A if the meters "dance".
There was a discussion in a guitar amp thread about class A 6L6GC's. We came to the conclusion that 20 Watts from a pair was possible. The amp in question ran from about 400 volts to make 20 watts in "class A". This is possible, but would require a plate to plate load impedance of about 15000 ohms. Possible, but not likely.
I have achieved 20 watts from a pair of Chinese 6L6GC's in a guitar amp. I used a 6600 ohm OPT and a B+ of about 300 volts and 70 mA per tube.
Thanks for the reply Tubelab. In my mentioned example I must then have gone somewhat into clas AB with the test; did not check (was long ago). Correction accepted.
The dancing I would accept if it meant that the meters were 'stationary' until maximum class A was reached, in which case the meters would then start to 'dance' as one goes into class AB. But earlier explanation is still valid.
Again not to lambast the guy, but jeepers - look at what he claims! As Miles said, Kirchoff's Laws have not been revoked. If so, where is his Nobel Prize?
The dancing I would accept if it meant that the meters were 'stationary' until maximum class A was reached, in which case the meters would then start to 'dance' as one goes into class AB. But earlier explanation is still valid.
Again not to lambast the guy, but jeepers - look at what he claims! As Miles said, Kirchoff's Laws have not been revoked. If so, where is his Nobel Prize?
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