captainbeefheart Posted January 7, 2022 Share Posted January 7, 2022 16 minutes ago, michaelwardjones said: This is an interesting post from a Carver owners on Audiogon: "i just had my amp in for a check (some tube noise and transformer hum) at wyred 4 sound - w4s is the exclusive contract manufacturer for these crimson amps had a friendly chat with their senior tech who worked on my amp - i know the w4s guys reasonably well, like them, have several pieces of their gear (digital, power supply, class d amps), w4s is a good company, well designed well built, good sounding high value gear, good reputation, and straight shooters in my book i was told that based on their bench experience, the crimson amp can make 75w driving one channel... (didn’t ask for frequency range spec, sorry), can’t in both channels though (’more like 60 thru both channels’), but this isn’t due to the output transformers as limiting factor, but rather, the power transformer, which can’t quite deliver the juice for 75 wpc asked how such a small light tube amp makes that kind of power, was told that the reason is the kt120’s are pretty strong, plus ’the neat feedback circuit employed from the output, holds the distortion in check, other guys don’t do this, we were kinda surprised it can do that through those small output transformers...’ " https://forum.audiogon.com/discussions/peeking-inside-a-carver-crimson-275-tube-amplifier?lastpage=true&page=3#2314379 Nothing in that statement makes any sense. No tube on earth can magically change the laws of physics of output transformers. The amp has a very simple global feedback circuit just like almost all tube amps have, there is nothing 'special' about it. I believe he is confused about the 'DC restorer' circuit which has nothing to do with the feedback, it is just another name for sliding bias where he uses some 1N4148 diodes at the control grids to slide the bias more negative at higher output power keeping the tubes running cooler. When testing amplifiers on a bench almost all techs use 1kHz, some I have seen use 400Hz but the industry standard is 1kHz, yes the amp can produce 75 watts at 1kHz at 2.8% THD, the problem is they obviously never tested the amplifier output at bass frequencies which is where the problem lies with this amplifier. Of course these people have to try and cover this up, they are in business with these amps and need to make profits. Regardless of that whoever wrote that has no idea what they are talking about proven by the ridiculous things said in that statement. "neat feedback circuit" and "kt120's are pretty strong so the amp can be light" These statements should make any engineer or anyone that knows enough tube amps to just cringe. It's actually quite sad this company lets this person make a public statement like that as it's completely ridiculous. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted January 7, 2022 Share Posted January 7, 2022 I suspect a lot of people don't know or understand topologies and they buy the equipment and listen to it and enjoy it. In Yogi Berra style lingo "I don't know what I like, but I know what I like". Quote Link to comment Share on other sites More sharing options...
Curious_George Posted January 7, 2022 Share Posted January 7, 2022 Yep... I don't think I'd be taking anything to W4S or at least their senior tech. 1 Quote Link to comment Share on other sites More sharing options...
Curious_George Posted January 7, 2022 Share Posted January 7, 2022 22 minutes ago, captainbeefheart said: When testing amplifiers on a bench almost all techs use 1kHz, some I have seen use 400Hz but the industry standard is 1kHz. 1kHz is best especially if you have your 400Hz high pass filter on to eliminate power supply ripple and other low frequency junk for testing. I test with and without the 400Hz high pass to ensure there is no ripple. Quote Link to comment Share on other sites More sharing options...
Khornukopia Posted January 7, 2022 Share Posted January 7, 2022 I am learning a lot about tube amplifiers because of the Carver Crimson 275. 1 Quote Link to comment Share on other sites More sharing options...
jjptkd Posted January 7, 2022 Share Posted January 7, 2022 2 minutes ago, Curious_George said: I suspect a lot of people don't know or understand topologies and they buy the equipment and listen to it and enjoy it. In Yogi Berra style lingo "I don't know what I like, but I know what I like". I own half a dozen Sunfire components and before that was a huge Carver fanatic-- I've had all of the big boy Carver amps and Sunfire amps for that matter never really had any problems with any of it. My Sunfire gear has all been serviced updated re-capped and bench tested I know the amplifiers I have exceed factory spec so when I considered buying the Carver 275 I never even considered the possibility it would be so far off in its power rating. I used to own the much smaller VTA-20 the 20wpc EL-84 tube amp he sold about 10 years ago and it is half the size physically as the 275-- the 275 does seem louder than the 20wpc amps I've owned (Carver and Jolida) in the past as they would always run out of gas where the 275 never seems to. Quote Link to comment Share on other sites More sharing options...
captainbeefheart Posted January 8, 2022 Share Posted January 8, 2022 3 hours ago, Curious_George said: Yep... I don't think I'd be taking anything to W4S or at least their senior tech. I seriously was cringing while reading what he wrote. I mean if that's their 'senior tech' which I always took that title as the head honcho that knows their stuff then that is pretty scary. That is extremely embarrassing for the whole company for that to now be posted and quoted on these forums forever. Not a good look. Quote Link to comment Share on other sites More sharing options...
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