I have to admit that I personally care less about powerful full-range SET amplifiers. I do not take their sound seriously, in fact I do not believe they are cable to do “right full-range sound” and what I see then I always imagine them with huge, barrel-size out transformer driving LF only.

It looks like HAT announced this new Magna – 160 Watts of Single-Ended Class A mono-block amplifiers.  The 160W is already a serious power. I never heard the amps but juts reading the specifications and speculating on its features I have more doubtful, common sense, questions then answers.

Frequency Response : 10 Hz to 100 kHz; -3dB  
Power Output : 160 Watts @ 4 & 8 ohms; 1 kHz  
Input Sensitivity : 2.7 V RMS for full power output  
Gain : 22.50 dB at 8 ohm  
Rise Time : 5 microseconds  
Noise : 105 dB below rated output  
Tube Complement : 1x 6N1P-EV, 1 x 6N30P-DR , 1 x Eimac 450TH  
Dimensions : 11.8"x 25.2"x 14.2"  
DC coupled all tube circuit (only output transformer without capacitors)
Low global feedback configuration with damping factor of 20
High capacity in power supply resulting to over 500joules of energy storage
Full double stabilization of high voltage for driver tubes
6N1P-EV & 6N30P-DR long life military grade tubes for driver purposes
Full automatic bias with automatic-adjust (no any adjustment).
Variable bias (two mode with 40W & 160W of output power)
Balanced DC power to supply filament of output tube
Balanced regulated DC power to supply filament for driver tubes
Both input and output WBT connectors
Input wired with pure 6N silver (99,9999% of silver purity)
All aluminum modulated chassis

The Eimac 450TH is a very interesting tube with low filament voltage and 450W of plate dissipation. I question the sincerity of the drivers those people used. The 6N1P is horribly sound tube. That entire army of the 6N1..1,2,3 tube were so disgusting sounding that only based upon the fact that Audio Magna used this tube I feel that this amps should not be used for anything more than sound re-enforcement in a public restrooms.

Then it has 6N30P. The 6N30P is mid gain mid current driver. I am not a big fan of an amplifier running in A2, but 450TH operated ONLY in deep A2. Let live aside the objective or imaginary problem of A2 operation but… if the out stage is in A2 then the driver stage should be able to supply the necessary current to maintain this operation.  I really would like to see the top and bottom of the sinusoid at that 6N30P driver while the amp I caring 2.7 V RMS of full power output. The 6N30P should be melting in there… unless it used as a cathode follower….

The response. The claim 10 Hz to 100 kHz; -3dB  … or something that I call “Fuck You Response”.  Sure, this amp might be able to care 10 Hz to 100 kHz at 2W of output power … but who cares? When manufactures inform about frequency response then they must indicate it at FULL pout power, or in that case it would be 160W. No one care that .00000012W this amp can even to drive a video signal!!! I peroalsy do not think that 160W Audio Magna will be able to go lover then ~70Hz… but it is me.. The truth should be known to the manufacturer.

Anyhow, another silver-wired, direct coupled, powerful SET… Most likely it is a bogus amp, so far it is with defiantly bogus description….

Looking again at the NAT Audio Magna amp, the amps around the 833A, GU81, 50TH, 1000TH, GM100 and many other SETs that try to use powers transmuting tubes I feel that the entire endeavor of powerful SETs shoot itself in a leg.

If a person has too dead loudspeaker or a large listening room then a person might feel that need more power from him SET (it is not always correct). However, s it possible to get more single-ended full-range power out of SET without fundamentally compromising the performance of a SET? I am very much not expert on amplification topologies but my common sense suggests me that it is imposable and pursuing more power we unavoidably but voluntary screw up our SETs.

More power from transmuting tubes = higher voltage on plate. Higher voltage = less current. Less current = higher plate impedance. Higher plate impedance = more turns in the output transformer. With all excessive isolations and windings capacitance due to explainable needs to care high voltages, the  increase of power in any SET amp shoot against the HF extension and the quality of HF as high voltage (via increasing capacitance) dehydrates higher frequencies

Then there is a subject of transformer saturation at LF – it directly proportional to power – with more powers more and more inductance the transformer shell care. The NAT Audio Magna amp from my post above in order to pump full 160W power out of that 450TH tube (let presume that the drive it at 1000V that would make it to have ~ 7K plate impedance). This way it would need at least 250H inductance to go down to relatively low number of LF cut off (~30-40Hz). Can you imagine the size of 250H transformer able to care 160W? It is obviously not what the Audio Magna has under the hood. I would not mention what would happen with capacitance in oversized that transformer.

That all brings the subject of a necessity of powerful full -range SET. I personally feel that any powerful full -range SET is an aberration. SET should be up-to <10W and then if more power is necessary from then SET might be split to DSET. This would assure a topologic and implementation absents of any compromises.

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=5344

People should not be under impression that more power can cure low sensitivity acoustic systems. Sure with more power lower sensitivity acoustic systems WILL perform much better but it will NOT be equal to higher sensitivity acoustic systems driven by a moderate power.

So, what high-power powerful full – range SETs prove? A celebration of wishful thinking over the sense of reality?  The Audio Magna has two operational modes: 40W and 160W. If the Audio Magna operates (electrically) well-enough at 40W then can you image how much compromised the sound of that amp is at 40W if the amps stages and magnetics were designed to care 160W?

Completely agree... but there is one possibility to get the inductance up without increasing the turns; use a smaller airgap in the OPT.
This will tend to saturate the thing sooner for a given current. BUT there is a trick that has been successfully employed to get around this, which involves using the filament current to offset the dc flux in the core - a few turns running 10-20A of dc should do it here.

But I don't think they are doing this here. What I would bet is that that they are running the thing in A2 with a much lower Z primary, using a lower B+ and high standing current. They are also using feedback which will help the bandwidth.

Btw, what do you mean by "dehydrated" highs?! I've heard you use that one before...

Cheers
cv

cv wrote:

But I don't think they are doing this here. What I would bet is that that they are running the thing in A2 with a much lower Z primary, using a lower B+ and high standing current. They are also using feedback which will help the bandwidth.

cv wrote:

Btw, what do you mean by "dehydrated" highs?! I've heard you use that one before...

That is my permanent pain with all high voltage (>500V) tubes. I do not like their sound. The excessive space for OPT dielectric in those amps creates excessive capacitance that not only rolls HF (there is a way to fight with it) but also make HF that merged differently with the rest audio bandwidth. That entire army of amp makes HF unfertile – their HF “are there” but their HF are meaningless. Their HF usually have different “stickiness” then the rest of the bandwidth – I call it different moisture of tone or dehydration…. That all crates something that I call the “elephant sound” – when the high voltage tubes internally kind of “burn” the ability to discriminate the tiny details and minute HF events. Those tubes usually “impress” the Morons with “large” sound trading the delicacy and sophistication as fine information is burned out by the high-power tubes (I presume that in capacitance of OPT and perhaps in the excessive dimensions of electron cloud). That Sound looks like a painting that was made with a 10 feet brash. That minting looks fine if you look at it from one mile away but it you care about the fine details and subtle play of shadow then it is moistly way beyond the resolution of high-power tubes. They are juts an elephants run over the bushes of blueberrys, not even acknowledging what they step upon…

Hi Romy, KR audio is making high power SET and parallel SET amps using tubes designed by them specifically for low frequency amplification (read as in not radio frequencies).  They are getting the power with lower voltages and higher currents than from transmitting tubes and their output transformers are some of the only ones I have seen measurements for that show essentially no core saturation.  The VA350 model I have is down about 1 db at 25khz and -3 db at 40Khz, so a wide enough bandwidth and bass to 5 Hz...at about 5 watts of power.

morricab wrote:

Hi Romy, KR audio is making high power SET and parallel SET amps using tubes designed by them specifically for low frequency amplification (read as in not radio frequencies).  They are getting the power with lower voltages and higher currents than from transmitting tubes and their output transformers are some of the only ones I have seen measurements for that show essentially no core saturation.  The VA350 model I have is down about 1 db at 25khz and -3 db at 40Khz, so a wide enough bandwidth and bass to 5 Hz...at about 5 watts of power.