Nobsound 6P1 6.8W * 2 Vacuum Tube Power Amplifier; Stereo Class A Single-Ended Audio Amp Handcrafted (without Headphone Amp Function)

Excellent seller! Great piece of kit! Highly recommend

This is a great little Valve/Tube amp. I sad the manufacturer for the schematic and they sent it to me much to my surprise as I haven’t found it anywhere online. The 6p1s are paralleled up in the output stage, which is not a common design, but it’s a cheap way to get reasonable power output using inexpensive valves/tubes. It sounds great, I’m an engineer that grew up with these amps not an audiophile and it sounds a lot better to me than many of the 1950s amps I remember. My only criticism is it desperately needs treble and bass controls. I could retro fit this circuitry as there is a 1k resistor on the input so plenty of scope to do this. However I have decided to buy a valve preamp instead. Even once you can turn up the bass, don’t expect a lot of it!

So I am first of all running super efficient 1985 Klipsch Cornwalls, and this is in a simple 2 channel mostly analog setup. In all the forums they say that Cornwalls LOVE the Dynaco ST70 power amplifier and PAS3 Pre-amp. So I found a museum quality example of said amplifier and paid a guy to recap it and beef it up. Well the amp took months and came back with all sorts of problems. I pretty well publicly swore off tubes and found a great deal on a nice eMotiva power amp and matching pre and a reference CD player. So now we get to the Nobsound amplifier, I was very happy with the eMotiva but still longed for tubes. I snagged this amp a few weeks ago and totally LOVE it. Its an easy swap from the eMotiva power amp to this one and its about 90% of the eMotiva….I use this amp for quieter music like Jazz and singer/songwriter stuff. I love it!!!

Los bulbos se usan únicamente en las etapas preamplificadoras donde tienen muy poca relevancia. La etapa de salida es un clase AB común a transistores.Cuando se solicita un amplificador a base de bulbos, es debido a que en su etapa de salida producen una curva de distorsión/potencia con un codo no muy agudo por lo que es poco notoria al oido humano en el caso de manejarlos en alto nivel. En el caso de los transistores se nota ese cambio brusco en distorsión a un aumento de la potencia máxima.

This will be a multi-part review as the amp burns in. I will edit the review over time.Part i - Unboxing, setup and integration with existing equipment and sound characteristics during initial 14 hours.BackgroundThis is my first tube HiFi amplifier. It is not my first tube amp. I have owned several guitar tube amplifiers and a Hammond M3 Organ which had a tube amp inside it. I am very familiar with guitar tube amps having owned and played professionally over 35 years. I know how tubes are suppose to sound and can recognize the various differences in tubes by different manufacturers and age. I have also modified guitar tube amps.ArrivalThe box was simple and heavily taped. The amp came bagged and taped and was suspending in a framework of foam. The tubes were bubble wrapped individually and inside a bubble wrap bag then tapped to the amp bag.The inside of the box and amp itself smelled of chemicals. I understand this to be insecticide commonly used in industrial shipments from China.The Tubes shipped were 4 Chinese 6P1 two marked 81.4 and two marked 80.4 one had "J 06" in white hand drawn in a diamond. I Split the pairs to keep both sides equal. 80.4 in front, 81.4 in back. The rectifier tube is a Chinese 5U4C. Power Tubes (2 ea) are Chinese 68HC.After full tube burning I do intend to roll power and pre-amp tubes. The Rectifier tube I am going to leave alone. As it appears the manufacturer swapped the stock 5Z4P tube for the 5U4C. There were some failures noted a few years back that may have facilitated this change. I am adding a APC LE1200 voltage regulator set to 110 volts. (a good thing to do for this amp in this old house) Read Stephe Koontz review for more info on tubes and mods she has made.No manual. Tube install was easy. I wore white gloves when handling the tubes and gently pushed them into place.The insecticide smell goes away after a day or two.On power up I let the amp warm up and settle in for about an hour before sending it a signal.Set Up and Initial Sound QualityI am using a Fosi Box X2 Phono /Line Pre-AMplifier with GE tubes. My initial signals I sent were from a Lenovo tablet running USB Audio Player Pro with Tidal and MQA enabled. Through a ifi HipDac to the FOsi pre-amp, signal splitting the output to monitor VU with DOUK audio LED VU meters configured L and R with peak hold (see picture). True to other reviewers the first several hours of music (playing a ambient playlist on Tidal) the audio was murky, and slightly muffled. After four hours I turned it off and came back later that night, and listened to MQA albums by Dr. Lonnie Smith and Crosby Still and Nash and some beaty electronic music. The sound was coming to life slowly. (fully expected) The highs and midrange came in first and the bass has slowly gaining in presence.Listening room is my small home office 12x12 with 10 ft ceiling (small old house) so I do not listen at a very high volume at all. Typically around 50-60 db max. This equates to about 10 o'Clock on the volume knob for my bi-wired 88db Sensitivity rated Wharfedale 80th Anniversary Denton bookshelf speakers. At this volume as of this morning and another three hours of listening I have no audible noise. The sounds is smooth. Detailed....remarkably musical and dynamic. I have about 12 hours on the amp now. Particulalry the midrange and upper is very detailed but soft. Vocals are particularly...for lack of a better description, perfect. I cannot hear any issue with vocal presentations. They are rendered clear and natural, depending of course on the quality of the recording. Oscar Jerome's track Gravitate is one in particular that highlights that quality.The soundstage is wide and tall, and more open than my Class D amps I have been listening to. The sounds literally comes from behind me, above, and behind the amp. You are transported to the room with the musicians in some recordings.Temp wise, the amp is quite warm but not hot. I would not touch the tubes. (I never do without them cool and wearing gloves). Given that heat increases resistance I wonder about high room ambient temperature and the amp's performance. Here in the northern U.S. I don't have much worry about that but might consider a small noiseless fan to move air over the amp. So far listening the amp sounds it's best after it warms up but I notice it does work a bit harder. Something to watch if the room is in the upper 70's.I also use a 4 band EQ from Bellari in the audio chain between the amp and pre-amp. (because of the dual purpose nature of the FOSI preamp, phono and line in pre-amp)Many commented that using a pre-amp really makes this amp shine. I concur. (I find the FOSI X2 a brilliant piece of kit and a perfect match for this amp DOUK/Nobsound makes a similar if not the same version as well I may buy one just to say this rig's power is all nobsound...)I put tape over the blue power LED. It is overly bright. Replacing it with a red jewel light would be a nice upgrade. If possible. the volume knob and power toggle both feel solid. The volume is notched.Esoteric Sound ImpressionsOverall thus far I feel this amp is presenting the recorded material in a rather musical yet transparent manner. It does not artificially bloom the bass and in many older recordings you will hear the kick drum where it should be...just above the bass guitar or double bass lowest frequencies. This observation may lead some to declare the amp lacks bass. I disagree. You are hearing what is truly there. Many old and modern speakers artificially bloom the lower frequencies purposely. Because....it is "all about da bass"...For a generation raised Hip-Hop and EDM in cars with subwoofers that reach blocks, shake windows, crumbling mortar in chimneys and brick facades of old buildings...I can see where one might declare this amp lacks bass. I disagree. I hear plenty of bass right now.`See the spectrum screen shot and sampling sonogram of Jorja Smith's track, Rose Rouge. The bass extends to 30hz and the primary frequencies are clearly seen at in the pink sonogram. The sound of the electric bass notes and kick drum are well balanced with the rest of the track and are not lacking at all. The notes are rich and dynamic with a bouncy push tubes are known for. The Dentons are vintage voiced so they do roll off the top end a bit but they are also still breaking in.I purposely chose this tube amp for low volume listening in a small space with mid-sensitivity vintage voiced speaker like the Denton. The cost and point to point, tube rectified, two channel class A was what I wanted and was well within my budget.So is this amp a rock and roll power dream? No of course not.There were moments listening last night to Dr. Lonnie SMith's live album, Breathe that were (pun intended) breathtaking. Not only is that recording one of the best live recordings ever made, the amp brought it into my room. Marvelous....I have not listened to an vinyl yet. I am reserving that for after 30 hours of burn in. So far...I am delighted and quite impressed at this clever amp listening to it I get those gushy feels and I just ooze into the music.This amp...already is probably the best sounding amp I have had the opportunity to audition. (apart from some of my guitar tube amps which is not apples to apples.) More to come....

I’ve only had this amp for a bit less than one month as I write this review, but that may be enough to capture some impressions for anyone else interested in this product. I considered this amp for quite a while against some other amps in this general category and above, particularly the Reisong A10. I had also bought some other Nobsound/Douk Audio products on Amazon with good results. This amp continued to stand out as a strong value and seemed like a safe choice. I have not been disappointed.I have been resisting the temptation to roll the tubes and have stayed with the supplied tubes so far, in the interest of giving the tubes due time to break in. My initial impressions will be based on using the stock tubes, which seem to be decent but I do expect to roll the tubes eventually based on consensus of using US 6SN7s for the input tubes and Russian 6P1Ps for the output tubes. Interestingly, Nobsound chose to provide a Russian 6H8C for the input tubes which are well regarded. Also note that this amp uses tube rectification, which is unusual for an amp in this price class. I’m not clear on how much the rectification tube affects the sound but tube rectification keeps this amps as a true tube amp and s generally only found on more expensive tube amps.The fist thing I notices on unboxing was the heft of the unit relative to its fairly small footprint, owing to the weight of the transformers. Build quality is impressive as has been the case with other Douk products that I own. Otherwise the presentation is nothing elaborate - just the amp, a power cord, and carefully packaged tubes are included. There was an odd smell of newness upon unboxing but this dissipated with the first use. There is no owner’s manual and no indication on the amp as to which tubes go where. However, looking at a picture on Amazon is all the guidance one needs to install the tubes. The rear panel connectors, fairly standard for Douk products, are high quality. The front panel volume knob has a nice machine feel to it, is sized well, and moves in stepped intervals. The power switch is larger than expected and also has a robust, quality feel to it with very positive actuation. The amber backlit VU meters are also a quallity touch and seem to work well. As others have mentioned, the power LED is very bright and curiously blue in color. I’m not sure why Nobsound didn’t opt for an amber LED to match the VU meters and tube glow, or even chose to include a power LED at all since it is not really necessary given the VU meters and tube indication that the amp is on. Quite frankly, over time I have not found it to be much of an issue. Being a class A SET amp, this amp gets very hot and radiates heat during operation, as expected. Being that no cover is supplied, it is advisable to keep this amp on a location where it cannot be touched.Sound quality matches up with my favorable impression of the overall build quality. While some may wonder if 6.8 watts is adequate, with my 98 dB efficient speakers, it is well adequate. With the volume know at roughly half way of its full travel, this amp plays loud. Power is just not an issue but, as with any low power SET amp, satisfaction is contingent upon using efficient speakers. I may eventually try this amp with other less efficient speakers as a curiosity but I bought this amp specifically for these high efficiency speakers. Sound is strong, articulate, detailed, and punchy. If there is one characteristic that stands out relative to other tube amps that I have experimented with, this amp has a very clear and neutral sound unlike the warm dark coloration I have come to associate with tubes. In that regard, the sound seems to have the bass bloom characteristic of tubes with a more neutral midrange. Highs have a bell like quality without being too forward or harsh. For guitar players out there, a tone wood analogy I would use is that, where most amps offer a complexity akin to rosewood, this one sounds more like mahogany. Considering my preference for the clarity of mahogany guitars, this character in an amp is favorable to me. Imaging is pinpoint with good center fill between the speakers. There is no noticeable hum and moments between songs are silent. In short, this amp does everything well thus far in my short ownership experience. I expect sound to improve somewhat given that I have only perhaps 100 hours or so on the tubes so far. The tubes are probably still breaking in. I also expect to eventually roll them as indicated above, with the expectation of taking the sound to a higher level, but that is yet to be determined. For right now, I am experiencing a level of sound that command my recommendation of this product to anyone who might be considering this amp. For completeness I should also mention that I am using a vintage Counterpoint tube preamp going into the Nobsound and an FX-Audio DAC going into the preamp. Since the Nobsound is an integrated amp, the use of a preamp is not necessarily required but may factor into my favorable impressions. All of my listening has been via streaming, much with high definition audio via Amazon Music HD, direct connected over USB and also using Bluetooth.Compared to an even lower powered but surprisingly great sounding Miniwatt N3 SET amp, the Nobsound has a different character. Again, it is one of neutrality where the Miniwatt seems to have more of that dark tubey tone. I have not A/B compared the two, nor do I intend to get too involved in such comparisons at the expense of just sitting down to enjoy music. Many reviews of the Miniwatt, also sold under the name APPJ or Tube Cube are available as a product that may be of interest to the Nobsound customer. Bear in mind that at 3.5 watts per channel, that product is only for the most efficient of speakers where the Nobound is considerably more powerful with its 6.8 watts. Suffice it to say that the Nobsound comes across as high quality and perhaps merits comparison with some higher priced gear. My adventures in Chinese made high fidelity gear has taught me that high quality is possible at tenable costs where early on in my pursuit of high fidelity in the 80s, a tube amp such as the Nobsound was just not an option. The caliber of sound I am getting would have required a substantially greater investment. The law of diminishing returns seems to be very much in play, to my ears, in audio. For the cost of the Nobsound, I believe most would find the value to be high, as do I. Consider my impressions to be preliminary given my short period of ownership, but this amp is meeting all of my expectations so far as a quality, high value product. I must also underscore that these results are predicated on use with a high quality, high efficiency speaker. With that context, the Nobsound does everything it promised well and begs for comparison with other tube amps on the market. As far as I can tell, this product comes in at a price to quality ratio that is unique, for a true tube amp with tube rectification, hand soldered point to point wiring, a quality of build that seems destined to last, delivering the detail and presentation expected of a tube amp.

Just got it today and as I type this I'm listening to a video on Youtube of the O'Keeffe Music foundation. Before that I listened to a Tellarc CD of Rhapsody in Blue. I'm actually hearing things I had simply not heard on my other audio system. Not even broken in and yet shows its well worth the price of that amp. Now I'm thinking of getting the tube preamp of the same series.It's been basically a week for that amp to burn in its tubes. Yesterday I blew the socks off of a friend that is an audiophile. His conclusion is that it's awesome and well worth the cost. In the next few months I plan on getting better tubes. I'll keep you posted.Oh, about the high temperature? I'm wondering if some aren't simply unaware as to how hot tubes electronics runs.Now a month later. Got my hands on a few direct cut LPs and also Russian pressing and this is where I learned that less is better. Don't try to listen to this amplifier full blast. It's not made for that. Set it to comfortable room level and rediscover your music!