No. Because it negatively effects the sonic audio performance in the main audio frequency range. Having said that, if you have speakers with very large cones then a little local feedback can help the low frequency performance.
Klipsch Cornwalls and Amps I've Tried
- Thread starter Juancho
- Start date
No. Because it negatively effects the sonic audio performance in the main audio frequency range. Having said that, if you have speakers with very large cones then a little local feedback can help the low frequency performance.
The only totally quiet zero negative feedback tube amps I’ve had were indeed non ready to buy commercially produced ones.
I once had a a pair of one off Audio Innovations 2nd Audio push pull monoblocks that used only two ECC88s per monoblock . They used a different circuit to the usual four ECC88 or four ECC82 per monoblock models. They also had far less gain than the high gain originals. Solid state rectified. They had humbuckers, but I never needed to adjust them. They had been designed to match a very high gain custom built Audion Preamp and a pair of Audio Note Es.
The others were a pair of Welborne Terraplane DRD 300B SE monoblocks (choke loaded DC coupled). Once available as a DIY product before Welborne went out of business. Solid state rectified. They only used one 6n1p driver per amp and were also low gain (although not quite as low as the 2nd Audio were). The chap that built them (Greg Drygala of G point Audio) told me he tried building both valve and solid state rectified version, but only the solid state rectified versions were totally quiet with horns.
Obviously having fewer gain stages helps with noise but one issue with both of these low gain tube amps is that they aren’t so universally useable, as due to the low gain it’s difficult to get enough volume level with some material with speakers of lower sensitivity, unless you match to a v high gain preamp etc. I guess that’s why you don’t see production zero feedback tube amps that are low gain like this and are totally quiet with horns. The Welbornes were nearly ok gain wise but with the 2nd audios were too low for universal use.
SS amps are indeed quiet. Thanks for the reasons why. Didn’t quite clock that (most of them having a lot of negative feedback. 40dB is typical from what I remember. Makes perfect sense.
I do usually prefer the top end of valve rectified tube amps. Is it possible to build a valve rectified zero feedback tube power amp that’s quiet enough? Or is it v difficult?
I once had a a pair of one off Audio Innovations 2nd Audio push pull monoblocks that used only two ECC88s per monoblock . They used a different circuit to the usual four ECC88 or four ECC82 per monoblock models. They also had far less gain than the high gain originals. Solid state rectified. They had humbuckers, but I never needed to adjust them. They had been designed to match a very high gain custom built Audion Preamp and a pair of Audio Note Es.
The others were a pair of Welborne Terraplane DRD 300B SE monoblocks (choke loaded DC coupled). Once available as a DIY product before Welborne went out of business. Solid state rectified. They only used one 6n1p driver per amp and were also low gain (although not quite as low as the 2nd Audio were). The chap that built them (Greg Drygala of G point Audio) told me he tried building both valve and solid state rectified version, but only the solid state rectified versions were totally quiet with horns.
Obviously having fewer gain stages helps with noise but one issue with both of these low gain tube amps is that they aren’t so universally useable, as due to the low gain it’s difficult to get enough volume level with some material with speakers of lower sensitivity, unless you match to a v high gain preamp etc. I guess that’s why you don’t see production zero feedback tube amps that are low gain like this and are totally quiet with horns. The Welbornes were nearly ok gain wise but with the 2nd audios were too low for universal use.
SS amps are indeed quiet. Thanks for the reasons why. Didn’t quite clock that (most of them having a lot of negative feedback. 40dB is typical from what I remember. Makes perfect sense.
I do usually prefer the top end of valve rectified tube amps. Is it possible to build a valve rectified zero feedback tube power amp that’s quiet enough? Or is it v difficult?
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Would be v interested in some mods for the Welbornes (which I still have) . Let me know when/if you have a spare slot! If there was any way to convert them to being valve rectified too that would be great, but I’m unsure they would be as quiet with high sensitivity speakers as when solid state rectified.There's pretty well always room for improvement-even for one of yoursBut you don't know what mods I've done and that's not what this thread is about so I will resist going down that rabbit hole.
Back more on topic. I’ve heard the Cornwalls IVs too and think they are incredible for the money. Maybe the cone bass driver doesn’t quite blend perfectly with the mid and tweeter horn units, but for the money….
I sold a 300B amp to Jimmy Hughes (famous Hifi Mag Journaist) last year. He has a pair of Cornwall IVs in the long lounge of his Barbican flat (which also houses the largest amount of CDs I’ve seen anywhere!).
I thought the Cornwalls were really good. Effortless dynamics and impact etc. Superb with classical. From what I understand the all horn La Scala model is more integrated but the bass extension isn’t as good as the Cornwalls (limited to around 50 Hz)
I heard that for horn purists who like Vitavox drivers the Klipsch horns are not considered high end, but we can’t all afford or house a pair of Living Voice Vox Palladians or Vox Olympians! (£250k and 500K although likely higher now)
The 300B amp I sold Jimmy was a push pull design with humbuckers. It gave a slight bit of hum near the speakers but he said it was far less hum than other tube amps he had tried.
I sold those one off 2nd Audio monoblocks to Chris (thebiglebowski on forums) who has Living Voice Tone Scouts (with a Vitavox midrange driver) in a small living room. 103 dB sensitivity. Those custom 2nd audios were totally silent when we turned them on, and I put my ear right up to the drivers and couldn’t hear anything. In comparison his Border Parol 300B SE power amp (valve rectified) had quite a bit of hum with the Tone Scouts.
Sounds good. I remember those monoblocks built into series 800 chassis. Those are the 1st audio monos (not 2nds) with two tubes a side instead of four.
Not had a pair of those but I did have a pair of very early production 2nd Audio 6B4Gs monos which sounded good but really had terrible hum (this was even with normal sensitivity speakers, not horns. David Wright told me it was something inherent in the early design and to get rid of them and get later ones. Then had the later 2nd audio versions with 2A3s a few times but despite being quieter they never sounded as good as the 6B4G ones (including the very quiet one off low gain version)
Never tried the 1st audio but it should sounded better despite being lower powered, and I think it’s possible in that kind of zero feedback push pull amp that 6B4Gs sound better than 2A3s for some reason. So the 1st audio monoblocks might be good to mod. Didn’t you change them to being tube rectified too?
After Graham mentioned it, i wondered that perhaps one reason tube amps that are very quiet with horns are difficult to find is that they generally need to be low gain (like the ones I’ve had), which limits preamp and speaker compatibility. So not mainstream.
The Quad IIs use some negative feedback and are quite low gain too. Both those things help noise.
The one off low gain 2nd Audios and Welbornes monos had zero feedback and low gain. Totally quiet with horns. (I mean nothing). Both solid state rectified too which might help the noise floor further.
Fourlegs
Trade: WAVE High Fidelity digital cables
Just on the subject of the 2nd Audio 2A3 Monos, I had a pair of these that I bought new from Kevin at Definite when he was trading from his terrace house in West Bridgford. I bought the 2nd Audios after comparing them to a 1st Audio. It only took about 10 minutes of listening to decide to go for the monos.
About two years later I bought a pair of Border Patrol power supplies to go with the 2nd Audios, again from Kevin and they were a big improvement. At the time I was using an AI L2 pre amp but in reality that was a bit too high gain for the 2nd Audios even though I did like the sound. Things got much better when I swopped to a lower gain pre amp. I had the 2nd Audios plus BP power supplies for about 25 years, only changing when I went for a pair of Icon Audio MB845 Mk2 monos. Now they really were great amps.
As an aside, for many years I did the art work for the Definitve Audio hifi magazine adverts featuring PhotoShop altered photos of vintage trucks with huge horn speakers added to them. All mostly fake.
Mastersound 845PSE monoblocks: The trouble with Parallel Single Ended amplifier designs is they don't perform as well as a Single Ended Triode design with a single output valve per channel. The problem is that 2 output valves in parallel are not electrically identical, so each valve will amplify the signal slightly differently. You can correct this to some extent by applying some feedback, but that makes a mockery of using a single ended triode design in the first place. I suspect this is not done in the Mastersound, but relies on the matching of each pair of output valves. Paralleling output valves also reduces the audio performance considerably. The best results are achieved using a single triode output valve per channel.
Ming Da 805 monoblocks: This design is Class A2 and not a proper Class A design. You can achieve more power from Class A2, hence the "quoted" 45 watt spec, but I bet when you measure them into a real load they won't produce anything like 45 watts, or if they do it will be at something like 10-20% distortion. Class A2 amplifiers do not sound anywhere near as good as Class A amplifiers. You can tell Class A2 amplifiers by the extra power tube required (6L6 in this case) to drive the 805 valve. A good proper Class A SET design should be able to consist of a driver valve driving the triode power output valve, so just 2 stages. Done correctly with 2 stages and 2 valves per channel and interstage transformer coupled, it really doesn't get any better than this, especially into some high efficiency speakers like the Cornwalls....
Ming Da 805 monoblocks: This design is Class A2 and not a proper Class A design. You can achieve more power from Class A2, hence the "quoted" 45 watt spec, but I bet when you measure them into a real load they won't produce anything like 45 watts
, or if they do it will be at something like 10-20% distortion. Class A2 amplifiers do not sound anywhere near as good as Class A amplifiers. You can tell Class A2 amplifiers by the extra power tube required (6L6 in this case) to drive the 805 valve. A good proper Class A SET design should be able to consist of a driver valve driving the triode power output valve, so just 2 stages. Done correctly with 2 stages and 2 valves per channel and interstage transformer coupled, it really doesn't get any better than this, especially into some high efficiency speakers like the Cornwalls....
Radford Revival
Trade: Radford Revival
My new design has taken low noise into account - in fact it's so quiet you have to have the tweeter literally in your ear to hear the noise residual. The hum is only measurable via an audio analyser because it's in the microvolt range, you can't hear it with your ear touching the woofer in a silent room in a rural house! It's actually so low that the speaker cable can often pick up more hum than the amp itself gives out.
Not bad considering it's a valve amp using a conventional open framed mains transformer!
Not bad considering it's a valve amp using a conventional open framed mains transformer!
Sounds interesting. So the small tube on each monoblock was changed to one or two 5687? Or a mix of one 5687 and a different second small tube?
I once had a pair of Audion Silver Knoght push pull 300B monoblocks. They used one 5687 and one ECC88 per monoblock. Not sure which tube did what.
The Audions don’t have as good parts as some amps and the PP design isn’t as pure sounding as a single ended but I liked the musical sound, and they could drive quite a few more speakers due to the 25 watts available.
I once had a pair of Audion Silver Knoght push pull 300B monoblocks. They used one 5687 and one ECC88 per monoblock. Not sure which tube did what.
The Audions don’t have as good parts as some amps and the PP design isn’t as pure sounding as a single ended but I liked the musical sound, and they could drive quite a few more speakers due to the 25 watts available.
I remember those definitive adverts in Magaiznes! Didn’t realise it was photoshopped though! Nice.
Not tried the L2 before but it’s indeed quite high gain so not so good with the 2nd audios. It might have been a good gain match with the one off low gain pair of 2nd Audios I had that only used two ECC88s per monoblock.
Never tried Icon Audio amps. Have generally heard good things though.
Not really sure what point you're making. With the Ming Da you've got the wrong tubes. And the measured data is way different from your guestimates. You've probably never heard the Mastersounds........and all this incorrect data has very little to do with amps I've tried with the Cornwalls!Mastersound 845PSE monoblocks: The trouble with Parallel Single Ended amplifier designs is they don't perform as well as a Single Ended Triode design with a single output valve per channel. The problem is that 2 output valves in parallel are not electrically identical, so each valve will amplify the signal slightly differently. You can correct this to some extent by applying some feedback, but that makes a mockery of using a single ended triode design in the first place. I suspect this is not done in the Mastersound, but relies on the matching of each pair of output valves. Paralleling output valves also reduces the audio performance considerably. The best results are achieved using a single triode output valve per channel.
Ming Da 805 monoblocks: This design is Class A2 and not a proper Class A design. You can achieve more power from Class A2, hence the "quoted" 45 watt spec, but I bet when you measure them into a real load they won't produce anything like 45 watts
According to the information on the web from several sources including the UK distributor, the valve line up in the Ming Da 805A is 6N8, 6N9, 6L6, 805. As I said the 6L6 drives the 805, unless of course you have a different amplifier, or you have fitted different valves. My point in highlighting the fact that it isn't a class A amplifier, it is Class A2. The two sound very different. The 805 is an RF valve and needs to be driven by a power valve like a 6L6 (as in Ming Da's spec sheet) or a triode like a 2A3 or 300B. Lukasz Fikus (Lampizator) had to do a number of improvements to the 805 design to get them to work properly. But that is what you often have to do when you buy Chinese equipment.
Mastersound have had numerous UK distributors over the years. I have been approached several times about representing them in the UK. Each time I told them they should stick to their current distributor. Due to them changing their distributor over the years their products have had little support, hence we got involved trying to fix and repair Mastersound electronics, hence we got to test, measure and listen to most of their models.
My point in highlighting these facts is to make people aware who don't understand the technical aspects of certain designs and to debunk manufacturers marketing. As I said earlier, if you use a Mastersound SET amplifier, or a Ming Da 805 which came standard from the manufacturer, you will have gain and noise issues when connecting them to high efficiency speakers like the Klipsch Cornwall.
And yet the reality is you don't get any noise issues so I doubt you've tried these amps with Cornwalls. You also assume without asking that my Ming Das are the standard 805s. They are not: they are the Cavatinas measured by HiFi World at circa 1 % distortion at 45watts, no negative feedback unlike the model you incorrectly cite.
Have you tried Lucas Fikazs mods? If not I don't think your comments have any legitimacy. I have done them for a client and the results are definitely not as he posts so we went with other mods. Anyhow, this is all along way from the subject of my post: amps that work well with the Cornwalls.
Have you tried Lucas Fikazs mods? If not I don't think your comments have any legitimacy. I have done them for a client and the results are definitely not as he posts so we went with other mods. Anyhow, this is all along way from the subject of my post: amps that work well with the Cornwalls.
Pity you couldn't have confirmed your model at the off. A number of posts about your Ming Da "model" 805 amplifiers and it turns out you have a different model. Well done!
Peter McDermott
pfm Member
I have looked at this thread a couple of times but have no technical knowledge whatsoever.
I am interested in the Forte 4 speakers but have two solid state amps (Denon PMA2500NE and Gato Audio Dia 250s) so assume that neither of these would bring out the best of the Fortes?
Best wishes, Peter
I am interested in the Forte 4 speakers but have two solid state amps (Denon PMA2500NE and Gato Audio Dia 250s) so assume that neither of these would bring out the best of the Fortes?
Best wishes, Peter
Best to try them Peter. The listening result will be up to what you think. You should get more out of the Forte with a nice valve amplifier, preferably something not made in China as these tend to be fraught with problems, like incorrect mains transformer ratings. Like "Juancho" found, he had to modify his amps to get them to work with the Cornwalls and the Forte is very close on efficiency. The Forte is 99dB efficient and the Cornwall is 102dB.
