I'm writing this reply in hopes that ultimately, maybe the forum owner will kindly remove this review from his website (or at the very least fix the errors and remove the hateful replies towards Bob). If what I say seems offensive, well please understand that I am trying to say it as politely as possible but there are things that I am going to say that won't be pleasant to hear and there is nothing I can do other than to speak the truth, and the truth needs to be told.
I am a long time owner of Carver equipment, I have owned his components for over 30 years. Now, before you label me a 'fanboy' please hear me out. This post has nothing to do with my affinity for Carver gear. It has to do with righting a terrible wrong that is/has happened on this website.
The problems as I see them are the following:
1. The amplifier tests were done incorrectly.
2. The concern over the grounding of the amp is misplaced/unwarranted
3. The issue with the use of bonding adhesive of the meter and rectifier board is a non-issue
4. The concern over undersized transformers on the output stage are unfounded and incorrect
5. Nobody who has has tested the amplifier has actually listened to this amplifier and judged it for it's sound quality
6. The amplifier -IS- mildly over-rated in terms of how much direct wattage it can deliver, and how much low frequency wattage it can produce.
7. The Bob bashing here is horrific, and pretty sad IMO considering the lack of knowledge people have about him and his products.
I'm going to discuss these issues as I go along, but also understand that I know a bit more in terms of the background on this amp than most people here. I have not seen anyone else come forward about it. I'm going to so the record can be set straight and let the chips fall where they may.
The Crimson 275 was an amp that Bob was developing to be an 'affordable' version of his $10k 350W tube monoblocks. Now before you ask why Bob is building/selling tube amps, please understand that Bob's an amp designer, he has always had a passion for tube amps and their sound, but the cost to build them with ample power has always been the limiting factor. If you care to research this, look up his Silver Seven TUBE monoblocks, which were the reference for his Silver 7t, Silver 9t, and and TFM series amplifiers. All of those solid state amp designs worked to mimic the sound of the Silver Seven Tube amp which was the reference. Below is Bob's original Silver Seven design from the 1980's:
In recent years, he developed a way to get more power out of a tube amp without running it hot enough to fry eggs on. This is an adjunct way of using his Sunfire amp designs (bias regulation) applied to a tube amp. The amp bias is variable with the audio signal, so the power tubes are not running at full throttle at all times. This was how he developed the 350W monoblocks that only run 12 power tubes total instead of 40 power tubes in the Silver Seven monoblocks.
The Crimson 275 was a down-scaled 2-channel version of the 350W design. His intent was to capture the sound quality of the Crimson 350's in a single 75WPC 2-channel amp. For the most part, he accomplished that goal. Now you might think $2500-3000 is a large price for them, but compared to over 10k for the 350W monoblocks it's a bargain. Bob wanted to do a similar thing for his high-end tube amps as he did with the SS amps of the past, make an attainable version for more people who were not in the market for the high end amp.
Bob designed this amp while in preparation to attend Carverfest 2018. He worked on it's design tweaking the components for so many months in 2018 that he almost missed the deadline to ship the components from WA to NC (yes across the entire USA) so they would arrive at the festival in time. The amp components arrived late in the festival, and there were only a couple of days to get the components assembled into kits to deliver to attendees. Bob orchestrated the kit assembly, spent many hours working on assembly directions, helping people with builds, and testing some amps that did get built before the festival ended. The kits were sold to attendees at cost, and they were not intended to be re-sold for profit, as Bob had requested, and he placed a limit of 2 amps for each attendee. Now I'll ask all of you the question: Do you not see the kindness and generosity of a person like Bob who would do this for the people who hold/attend an audio meet in his honor? Why am I going on about this? Because you all need to know the BACKGROUND of this amp, and what type of person that Bob is.
Bob also wanted the amp to go into production before the end of the year, so once Carverfest was over, he moved ahead to getting it ready to ship to vendors. But some problems were cropping up with builds, and since people did not have time to assemble them at Carverfest, Bob offered anyone who could not finish their build to send it to him and he would assemble, bench test, and ship the completed amp back to them. At this time, some testing was being done by some of the electronics techs who had bought/built their amps. Also there were people at Carverfest who were concerned about the size of the output transformers and their "15W" labeling. I asked Bob directly about this, while on my way home from Carverfest, and his response was the output transformers are a custom design, they are designed to minimize the copper winding mass which minimizes latency of the transformer. These transformers are much more capable than their labeled rating by Edcor.
The problem with the net measured output as was that they only delivered about 50-60WPC, when both channels driven, instead of their 75W rating. But that's under a continuous 2-channel load into a resistor, not a dynamic speaker load. When I heard about this in October 2018, I -tried- to bring this to the attention of the people who would be marketing it during the holidays because I was afraid it would become a problem like it has on this forum. I asked Jim Clark to contact Frank and Jordon about it and make sure that the production amp met or exceeded the design spec, because the festival amp clearly did not meet the spec on a bench test setup.
Jim Clark became worried that I would damage his sales of the unit by discussing it on his website chat forum, and I was banished from his forum for what I believe is this reason (I won't get into the exact details of this it's not relevant). Needless to say Jim and marketing knew about the issue before it fully went to market. Jim tired to cover up the issue by bench testing a production unit himself, stating they met the power specs, and citing that the output transformers in the production unit were different than those in the festival amp.
The truth about the amplifier's capabilities are the following:
Each channel on it's own is capable of about 90W. This far exceeds any spec of the small output transformers, so the limitation is not the output transformers.
Both channels driven are capable of about 100-120W. The limiting factor here is the mains transformer, it can't deliver the full power when both channels are driven to their max.
The amp can probably deliver the RMS 75WPC of a musical load, across everything but the lowest frequencies. Keep in mind that this amp is primarily designed to run with a modern 2.1 or 2.2 channel setup with powered subwoofer(s). The powered subwoofer will easily cover any loss of low-end output of the amp, and this may be why a low-end output deficiency was overlooked.
Please understand that in recent years Bob designs amps for his personal enjoyment, he came out of retirement to design these tube amps for the love of audio design, and he's not doing it to rip anyone off. That's why he had offered a refund if you can't live with any of these perceived problems.
The question about the grounding being unsafe is unfounded. If you look at the amp inside, the common ground is tied to the chassis, so if any B+ or supply voltage shorted to the chassis (which is ground), the amp fuses will blow, shutting it down. It's a different way of preventing an electric shock, but if you think about it, it's probably best that the unit shorts itself if there is a fault. Regardless, Bob offered to add a ground to the 3'rd prong IEC if anyone wants it.
The use of adhesive to hold the meter and the rectifier board does not affect the performance of the amp. It was done to make the unit fit in it's footprint, and easier to assemble. Does it matter if some glue needs to be de-bonded 20 years from now to re-cap? You are going to throw away the caps that were used as bonding points to the chassis when that time comes anyway, just as you would caps that were hot-glued into a crossover on an audio speaker.
The use of 'thin' wires from the main board to the speaker terminals is a non-issue also. Have any of you noticed how thin the wires are in an output transformer? Or how thin the traces are on an amp board? The wires going from the board to the terminals easily have more cross section than either of those two signal carrying components.
Now, let's get to the issue of testing. If the tests were done incorrectly, this whole 'scientific' article becomes pretty non-scientific. I was told that the reason this testing shows such bad results is that putting test equipment leads on the ground terminal of the speaker output will cause the amp to feedback incorrectly, and the negative feedback error will cause the amp to become unstable. That's the reason why the tested results show such low numbers and high distortion compared to the 'actual' performance. It has nothing to do with the amp, it's transformers, or anything else inside it, it's the result of a testing error.
I'm just going to say, aside from any higher end unit Bob has designed (because I have not owned them) the Crimson 275 is one of his best sounding and most affordable amps for the money. I didn't pay the retail price for mine, but that does not mean I don't think they would be worth it. I have driven Carver Amazings with them for 3 years on one amp and never had a bit of trouble or lack of power/ability to drive them including low note reproduction. Compared to my TFM-45's the Crimson 275 does have a fair bit extra sparkle/live sound that I just don't get from the SS amp.
To hear all of the negative words that were said about this amp, and Bob, makes me feel sad. It's not the legacy he deserves, he has given much more than you know to the audio world with his innovative designs. And while I don't condone Jim Clark's actions before or on this forum in response, I don't think people here should base their opinion of Bob's designs or decision to buy something of his based on Jim having some interest in the business of selling Bob's amps.
I hope people reading this thread can put aside the 117 pages of hammering on the Crimson 275, and Bob in general, to listen to what I'm saying, and listen to some music from something Bob designed, and give an audio legend the benefit of the doubt. Bob is in the twilight of a 60+ year career designing audio and making it affordable, please show him a little respect.