@DF96
Thanks for answering my question. I think you are the first poster to clearly state whether you would buy this amp; or not.
So far then, we have 1 vote against this purchase.
That said, it seems below, there is not that much enthusiasm for this particular amp design.
Thanks for answering my question. I think you are the first poster to clearly state whether you would buy this amp; or not.
So far then, we have 1 vote against this purchase.
That said, it seems below, there is not that much enthusiasm for this particular amp design.
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@Andrewbee
Congratulations! It appears that you have mastered the art of a GOOGLE search.
Do you have any input to this thread?
Congratulations! It appears that you have mastered the art of a GOOGLE search.
Do you have any input to this thread?
No, not yet and have been trying since Googles inception. They keep adding to the search function😀
Already posted it, it is what prompted your obtuse response.
I am of the opinion that if you comprehended other responses, you would understand I was merely pointing to information to the product. There have been posts regarding waveforms looking off and the use of KT88's.
I was merely providing the source of the information so people could gather more information on the subject of discussion should they be so inclined.
My apologies for offending you SONDEKNZ.
Have a Wonderfull weekend!
@Andrewbee
No offense taken.
I am hoping that other members can offer opinions on this amp based upon the merit of the measured facts - as presented below, but evidently somewhat incomplete - without being swayed by additional factors like the designer's enviable reputation, other previous successful designs, etc. etc.
Let's see!
Yes. A wonderful weekend planned, with my wife treating me to a Birthday lunch outing, today. So, no complaints here.
Enjoy your weekend too...
No offense taken.
I am hoping that other members can offer opinions on this amp based upon the merit of the measured facts - as presented below, but evidently somewhat incomplete - without being swayed by additional factors like the designer's enviable reputation, other previous successful designs, etc. etc.
Let's see!
Yes. A wonderful weekend planned, with my wife treating me to a Birthday lunch outing, today. So, no complaints here.
Enjoy your weekend too...
There is appreciable 2nd harmonic present. I'd estimate it at over 1.5% and lots of 3rd - close to 5% at a guess, THD at full power could be an unimpressive 5% or more, pretty poor considering the presence of some feedback.
The FFT is not as useful as it could be due to window choice , I would have liked to see the residual mains related spectra which tells you a lot about the adequacy of design in terms of shielding, ground loop mitigation, and supply filter design.
Note that 5dB is just about useless as far as feedback goes. The figure of merit says the guy who usually uses none in his tube designs is about 20dB.
I often wonder if the preference for low feedback is due to an inability to properly compensate for phase shifts inside the loop (both LF and HF) - most significant of which originate in the output transformer. I don't use GNFB in SE amps or triode PP amps but THD of 1% at 25W using a PP pair of 300B without GNFB is not too hard to achieve - it can be done with PPP EL34 and a pair of 6550 as well.
I would consider this a 20W or so amplifier as designed and I would spend the extra money for the Lundahl outputs if you were to go this route..
Considering a decent chassis, transformers and all of the other parts required it might not be the worst choice you could make if the intent was to modify it in the future.
Should you decide to go DIY or start with this kit you'll get plenty of help here.
The FFT is not as useful as it could be due to window choice , I would have liked to see the residual mains related spectra which tells you a lot about the adequacy of design in terms of shielding, ground loop mitigation, and supply filter design.
Note that 5dB is just about useless as far as feedback goes. The figure of merit says the guy who usually uses none in his tube designs is about 20dB.
I often wonder if the preference for low feedback is due to an inability to properly compensate for phase shifts inside the loop (both LF and HF) - most significant of which originate in the output transformer. I don't use GNFB in SE amps or triode PP amps but THD of 1% at 25W using a PP pair of 300B without GNFB is not too hard to achieve - it can be done with PPP EL34 and a pair of 6550 as well.
I would consider this a 20W or so amplifier as designed and I would spend the extra money for the Lundahl outputs if you were to go this route..
Considering a decent chassis, transformers and all of the other parts required it might not be the worst choice you could make if the intent was to modify it in the future.
Should you decide to go DIY or start with this kit you'll get plenty of help here.
@kevinkr
Indeed a bravura response, Kevin! Thank you.
Much of what you have discussed is above my head, but appreciate that you have cast a very well
-informed vote.
FROM THE AMP DESIGNER’S OWN PROMOTIONAL NOTES: “...It has been designed around the magnificent KT120, one of the toughest tubes available. The amp can also handle the even more powerful KT150. Other tubes from the 6550/KT88 family will work, but the best overall sound can only be obtained from the KT120.”
This is an interesting comment by the designer of this new amp. Despite fully defendable claims (below) that the KT88 tube has lower distortion than the KT120 type, the designer maintains that the KT120 tube will provide the finest sound quality, in this circuit.
Could this mean that the circuit has been purpose-tuned for KT120 - distortion and all?
Clearly, KT88, 6550 and KT150 tube types will also operate well within this circuit, but could it be that the designer’s ears chose the KT120 tube simply on superior sound quality grounds - despite any additional distortion?
Can anyone shed some light on this surprise recommendation by the designer?
LATE UPDATE FROM THE AMP DESIGNER: "The circuit has been stabilized around the Edcor [OPTs]. It might not be stable with any other transformer and could oscillate or have other problems.
So sadly, it looks like LUNDAHL OPTs are not an option at all. It's EDCOR all the way.
This leaves the new KT120 amp under discussion here, looking quite similar to the (kitset) ODDWATT High Output Series 1 amp, which also features two KT120 tubes per achannel; the latter amp appearing to have greater power and provided in monoblock configuration.
It appears that DIYAUDIO has had plenty to do with the ODDWATT amps, but I have no idea which amp might be the better. ODDWATT provides no Scope Measurement views, that I could find at least.
Indeed a bravura response, Kevin! Thank you.
Much of what you have discussed is above my head, but appreciate that you have cast a very well
-informed vote.
FROM THE AMP DESIGNER’S OWN PROMOTIONAL NOTES: “...It has been designed around the magnificent KT120, one of the toughest tubes available. The amp can also handle the even more powerful KT150. Other tubes from the 6550/KT88 family will work, but the best overall sound can only be obtained from the KT120.”
This is an interesting comment by the designer of this new amp. Despite fully defendable claims (below) that the KT88 tube has lower distortion than the KT120 type, the designer maintains that the KT120 tube will provide the finest sound quality, in this circuit.
Could this mean that the circuit has been purpose-tuned for KT120 - distortion and all?
Clearly, KT88, 6550 and KT150 tube types will also operate well within this circuit, but could it be that the designer’s ears chose the KT120 tube simply on superior sound quality grounds - despite any additional distortion?
Can anyone shed some light on this surprise recommendation by the designer?
LATE UPDATE FROM THE AMP DESIGNER: "The circuit has been stabilized around the Edcor [OPTs]. It might not be stable with any other transformer and could oscillate or have other problems.
So sadly, it looks like LUNDAHL OPTs are not an option at all. It's EDCOR all the way.
This leaves the new KT120 amp under discussion here, looking quite similar to the (kitset) ODDWATT High Output Series 1 amp, which also features two KT120 tubes per achannel; the latter amp appearing to have greater power and provided in monoblock configuration.
It appears that DIYAUDIO has had plenty to do with the ODDWATT amps, but I have no idea which amp might be the better. ODDWATT provides no Scope Measurement views, that I could find at least.
The 25W FFT shows a third harmonic 28dB down, that's 4% distortion, not "just under 1%". The FFT has been performed without a window so there is severe spectral leakage completely masking the lower peaks and mains harmonics. The 1W plot also lacks windowing, but shows about -43dB H2, or about 0.7% distortion, not "less than 0.5%". With a proper window function the 25W FFT might show intermodulation with the mains harmonics, and other stuff, which is why a window must be used. For accurate measurement of harmonic levels and distortion a flat-top window is required, for a good overview with slight error in peak heights the Hann window is popular. 4% is complete unacceptable under any circumstances for music reproduction.
The triode graph shows a certain amount of 3rd harmonic of opposite phase much higher than 300b can do . The spice model I found is LTspice not compatible with my simulator Tina . If a gentleman can simulate it to see how much is the opposite phase distortion . The circuit can deliver 32W without transformer loses , so not exactly the same Vcc/ bias/ load , but it can give an idea .
Attachments
What does Mr. Heran have to do with diyAudio? AFAIK, most comments from here were quite negative about the OddWatt designs in general.
From the Transcendent Sound Bruiser sales page, first paragraph:
As if that is a big problem that this amp is the perfect solution to? Give me a break. If I had speakers like that, and I wanted a tube amp, well color me stupid, but I think I'd be shopping for speakers that were a better match.
Further, what is "reactive current" anyways and what does that have to do with this amp? I'd call that word salad, and that's just in the first paragraph.
Others have already addressed the THD and performance - no need to double up.
Lastly, at this price point I would expect to see $15 covers on those toroid transformers.
No I would not buy this amp.
As if that is a big problem that this amp is the perfect solution to? Give me a break. If I had speakers like that, and I wanted a tube amp, well color me stupid, but I think I'd be shopping for speakers that were a better match.
Further, what is "reactive current" anyways and what does that have to do with this amp? I'd call that word salad, and that's just in the first paragraph.
Others have already addressed the THD and performance - no need to double up.
Lastly, at this price point I would expect to see $15 covers on those toroid transformers.
No I would not buy this amp.
Reactive currents are those that aren't in phase with the voltage (i.e. inductive or capacitive loads).
Best regards!
Best regards!
The comment in the designer's response about the design only being stable with the Edcor output transformers and nothing else is a huge red flag, it means the design is completely seat of the pants, which on the face of it is confirmed by both the measured performance and the description of measured performance which do not match.
At this point, sadly I would say walk away.
You might want to consider a kit from Japan, shipping should be less and there are great offerings from Elekit, Triode, Sun Audio and others. Some of these choices may limit speaker choices to the more efficient end of the spectrum.
Depending on budget these guys may be able to help you procure a good Japanese kit configurable for 240V operation. I used them 20 yrs ago in dealings with Japanese transformer makers. EIFL EXPORT HOME PAGE,vacuum tube,valve,amplifier,speaker,mail-order sales
At this point, sadly I would say walk away.
You might want to consider a kit from Japan, shipping should be less and there are great offerings from Elekit, Triode, Sun Audio and others. Some of these choices may limit speaker choices to the more efficient end of the spectrum.
Depending on budget these guys may be able to help you procure a good Japanese kit configurable for 240V operation. I used them 20 yrs ago in dealings with Japanese transformer makers. EIFL EXPORT HOME PAGE,vacuum tube,valve,amplifier,speaker,mail-order sales
None of this is near as important as what the impedance curve of your speakers are — with the very high output impedance (for a PP amp) and the low impedance output taps (we do not know if the number i the same for both taps) if you are using a nominal 2Ω speaker then the 2.5Ω output impedance means that his is dipping into the current amp class (AmpR>SpeakerZ).
The relationship of the speakers FR (driver by a low output impedance amp) and the speakers impedance becomes very important.
Can you post an example impedance curve.
A triode PP amp with an output impedance akin to a SET is very unusual. But i love the look of the KT150 (which can also be used) and the idea of triode PP i am a fan of.
A link to the amp’s web page?
Edit: Thanx Andrew B Bruiser 35W Triode Amp for 4 ohm speakers
dave
With the 99.9%+ of speakers that don’t care about their impedance it will not be very suitable, but with a propery matched loudspeaker it could be a fantastic piece of hifi.
I’d say that the distortion at full power is not all that meaningful when listening at typical levels.
dave
Nowhere on this page can i see the amp called PP or SE?
dave
Based on power rating it pretty much has to be PP, noting that a pair of KT120 in PSE could make 20W, but the distortion spectra shown is very typical of PP amps.
PP 0fdbk amps generally have pretty high output impedances, the fact that this one has roughly 2 ohms output Z with 5dB of feedback says something is odd about the design of the output stage. (I would have expected 1 ohm or so)
Except that it might be an indication of relatively poor linearity at lower power levels as well. It's very hard to determine without listening to and measuring one.
The designer is well known and lots of audiophiles do like his designs, and there are enough of them out in the field that there is a relative level of assurance that it will work.
Judgment call for the buyer. I had not realized the price quoted included the shipping to NZ, but apparently it does since the prices quoted are much lower.
The chassis, transformers and other odds & ends included probably make it roughly worth the money asked. OTOH you could import a set of transformers from Japan or the US and get a chassis fabricated locally and build one of many good designs, including the classic 5-20 which can also be scaled to 60W using KT88s and 30W in triode. There are many variants that have been discussed here.
Yeah, not providing a cover for the toroid power transformer does give it that unfinished look.
PP 0fdbk amps generally have pretty high output impedances, the fact that this one has roughly 2 ohms output Z with 5dB of feedback says something is odd about the design of the output stage. (I would have expected 1 ohm or so)
Except that it might be an indication of relatively poor linearity at lower power levels as well. It's very hard to determine without listening to and measuring one.
The designer is well known and lots of audiophiles do like his designs, and there are enough of them out in the field that there is a relative level of assurance that it will work.
Judgment call for the buyer. I had not realized the price quoted included the shipping to NZ, but apparently it does since the prices quoted are much lower.
The chassis, transformers and other odds & ends included probably make it roughly worth the money asked. OTOH you could import a set of transformers from Japan or the US and get a chassis fabricated locally and build one of many good designs, including the classic 5-20 which can also be scaled to 60W using KT88s and 30W in triode. There are many variants that have been discussed here.
Yeah, not providing a cover for the toroid power transformer does give it that unfinished look.
The TRANSCENDENT SOUND BRUISER stereo kit is priced to sell for $999 - without tubes.
For pricing purposes, earlier in this thread I simply added the extra $300 to allow for the full (new stock) tube contingent.
I did not include additional costs for shipping to NZ, import duties, tax, etc.
Hopefully this makes sense.
And I have trouble selling valve headphone amps on ebay for £15 !
I am obviously massively too cheap.
The designer of this particular amp has a lot more name recognition than any of us... 😀
It does, and I looked at the teaser and still it did not register... LOL I never sold a single amp without tubes when I was actively pursuing the business.
I need to pay more attention! LOL
If you can source a chassis or several chassis in NZ at a reasonable price you could scratch build using one of many proven designs. Hashimoto output transformers from Japan are another option I failed to mention previously.
It does, and I looked at the teaser and still it did not register... LOL I never sold a single amp without tubes when I was actively pursuing the business.
I need to pay more attention! LOL
If you can source a chassis or several chassis in NZ at a reasonable price you could scratch build using one of many proven designs. Hashimoto output transformers from Japan are another option I failed to mention previously.
That's right. Take them off a while, then relist them at 2-3 times the price.
I bet they'll sell then.
Certainly. The measurements given aren’t enuff.
And with 2.5Ω output impedance great care with the speakers used. With the right speakers it could be a match made in heaven.
Rosenblitz has a certain talent for offbeat designs.
High current, designed for low impedance, could this be one of his Output Transformless designs and adapt it to use a low turns output transformer?
dave