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Peeking inside a Carver Crimson 275 Tube Amplifier
So, I just had to pop the hood on the Carver Crimson 275 tube amplifier. I was so curious as to how this little guy weighs so little and sounds so lovely.
Does the sound quality of this amp bear a relationship to the fact that there’s not too much going on in the unit? There are very few caps--from what this humble hobbyist can tell--in the signal chain. And, none of these caps are even what many would consider decent quality--i.e. they aren’t WIMA level, just generic. This amplifier beat out a PrimaLuna Dialogue HP (in my room/to my ears...much love for what PrimaLuna does). When I explored the innards of the PrimaLuna, it was cramped, busy and had so much going on--a way more complicated design.
Is it possible that Bob Carver, who many regard as a wily electronics expert, is able to truly tweak the sound by adding a resistor here or there, etc.? Surely all designers are doing this, but is he just really adroit at this? I wonder this because while some parts quality is very good to excellent, I was shocked to see the Suntan caps. They might be cheaper than some of the Dale resistors in the unit. I should note that Carver reportedly designed this amp and others similar with Tim de Paravicini--no slouch indeed!
I have described the sound of this amp as delicious. It’s that musical and good. But, as our esteemed member jjss [ @jjss ] pointed out in his review, he wondered if the sound quality could be improved further still. He detected a tiny amount of sheen here and there [I cannot recall his exact words.] even though he loved it like I do.
I may extract the two .22uF caps that look to be dealing with signal related to the 12at7 gain tubes and do a quick listening test.
- The layout is simple and clean looking. Unlike the larger monoblocks (that cost $10k), this model uses a PCB.
- The DC restorer circuit is nicely off to one side and out of the way. It doesn’t look all that complicated but I’m no electrical engineer. Why don’t more designers use this feature? It allows the power tubes to idle around 9.75w. Amazingly efficient.
- The amp has very good planned out ventilation and spacing. No parts are on top of each other.
- Most of the parts quality is good. There’s a host of Dale resistors, what look like Takmans, nice RCA jacks, heavy teflon hookup wire, and so on.
- Some of the parts quality is questionable. There’s some cheap Suntan (Hong Kong mfr.) film caps coupled to the power tubes and some no name caps linked to the gain signal tubes. I was not happy to see those, but I very much understand building stuff to a price point.
Does the sound quality of this amp bear a relationship to the fact that there’s not too much going on in the unit? There are very few caps--from what this humble hobbyist can tell--in the signal chain. And, none of these caps are even what many would consider decent quality--i.e. they aren’t WIMA level, just generic. This amplifier beat out a PrimaLuna Dialogue HP (in my room/to my ears...much love for what PrimaLuna does). When I explored the innards of the PrimaLuna, it was cramped, busy and had so much going on--a way more complicated design.
Is it possible that Bob Carver, who many regard as a wily electronics expert, is able to truly tweak the sound by adding a resistor here or there, etc.? Surely all designers are doing this, but is he just really adroit at this? I wonder this because while some parts quality is very good to excellent, I was shocked to see the Suntan caps. They might be cheaper than some of the Dale resistors in the unit. I should note that Carver reportedly designed this amp and others similar with Tim de Paravicini--no slouch indeed!
I have described the sound of this amp as delicious. It’s that musical and good. But, as our esteemed member jjss [ @jjss ] pointed out in his review, he wondered if the sound quality could be improved further still. He detected a tiny amount of sheen here and there [I cannot recall his exact words.] even though he loved it like I do.
I may extract the two .22uF caps that look to be dealing with signal related to the 12at7 gain tubes and do a quick listening test.
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https://redirect.viglink.com/?format=go&jsonp=vglnk_162576198114510&key=098b477826d9c73180a2... Here's a link. Photo will expire in a few weeks I think. I don't have a good photo sharing account. |
Ha! Yes, I think I can get it back together! The PrimaLuna was difficult to mod Because there was so much going on inside that amp, but I was able to do it. This guy has lots more room yet it’s just going to be difficult to find a place to secure larger caps. I have some ideas. But, most likely, I will remove the cheap caps I want to upgrade and just start with a listening test. If I don’t see a substantial improvement then I’ll just go back to the Suntan caps. I will not be modifying the circuits. |
I have heard that amp many times nice little unit but as you already know - cheap parts and circuit boards. Change out the caps and resistors Nichicon and some Amtrans or Audio Notes would be much better options. Neatness does not count but the separation of higher voltage power wires from the lower voltage wires is the way to go. Happy Listening. |
If it sounds good to you i would not mess with the caps at all because you can completely change the balance of the amplifier and you may or may not get better sound an easier way would be to swap new old stock tubes into the existing circuit and see if you like the change with different tubes instead of messing with the innards. |
I don’t see a problem with swapping out capacitors. Listen and evaluate what you hear. The original capacitors can simply be re-installed if no improved sound quality was obtained. In some circumstances the capacitors (Resistors as well) in the signal path may influence the component sound quality as much or more than swapping out tubes. Charles |
I used to own the Black Beauty, It ran very difficult speakers and can handle difficult loads, Unfortunately Bob carver setup Distributors globally and got everyone to buy and market the amps for some time and then dropped all the distributors within an instant. Nice Amps but the people running the company have no idea. If you need allot of power these make sense. |
Guys it’s not the caps that are the biggie. Resistors are where GREAT quality comes from. Good caps Russian PIOs Mundorf MCap and Vishay copper resistors.. AND yes WiMa would have been a heck of a better build... But the guy that voiced that amp is NO DUMMY.. He can really come up with GREAT sound on the cheap.. Carver was a transformer genius. He use to teach classes, 45-50 years ago.. Worked with a few apprenticeship programs to get your requirements.. I did a 3 day class with him. Had a pair of forearms like an APE, from hand winding transformers.. Great guy back then.. SMART very different approach to sound too.. I was a serious Mac guy.. Do you see a problem.. He sure did.. LOL Really though, you should see Carvers Point to Point.. pure art.. The 275 reflects his voicing BUT really NOT his ability to lay out a beautiful valve amp.. Two different things.. Good units.. the 275.. Tinkers delight for the price.. COOL running, lighter.. I like um.. |
Hello jbhiller! Bob Carver is a superb designer. He sells his company every ten years or so and starts another one to keep from getting bored. The man is an audio genius. If you replace those "iffy" capacitors, don't use anything less than Mundorfs with the appropriate rating. Since there are only two, go for the fanciest ones. Be sure they will fit. The Duelands for that rating are HUGE. Enjoy! |
Guys, great comments above are making this thread! Yes, I fully realize that swapping out coupling caps can change things for the better, not at all, or for the worse. I would, however, like to do the experiment. I'll likely test two types--WIMA and ClarityCap CMRs. I've used Audyn, Mundorf, VCap, Auricap, MultiCap, ClarityCap, and others in the past. I'm very tempted to call up Bob the man himself and ask him if I could visit him for an afternoon. I bet I'd learn more in 3-4 hours than I have tinkering, reading, and assessing on my own. I'm very, very curious to see inside the 350 monos. |
From above..."Go ahead and chase your tail. Knock yourself out! Placebos and sugar pills will make it sound “sublime!"" Hmmm.... Not only is this not a very fun spirit you cast on this experiment, but I cannot agree. Why is it do you think Bob himself says the 275 gets about 75% of the sound of the 350 monos, which cost $5k each? I think it’s because he worked really hard to keep cost down. Take Don Sach’s post about upgrading the crossover in the Klipsch Cornwall IV. Roy Delgado likely knows a bit more than Don about speaker design. That doesn’t mean Don is wrong. It means Don can be right that better caps and resistors can improve the speaker. It also, arguably, means that Don’s upgraded crossover parts come to $900 retail, and if Klipsch bought those parts the build cost would certainly elevate and perhaps drive down demand. I see this being the situation here. Bob Carver--the madman designer--put the 275 together with an eye on budget and end user price. And finally, I have real confidence in my ears and listening. I’ll even admit that something expensive or "better" doesn’t sound better when it doesn’t. When I put VCap CUTFs in my Primaluna at the gain and phase split area they helped and it sounded better. When I added in Audyn True Coppers and some better Mundorfs in as coupling the power tube section and filtering power they didn’t do much if anything--but cost me money! Wanting something to be better and actually making it better are different pieces. To each his own. Thanks for dropping by! |
Carver was a transformer genius. Bob carver learned how to wind output transformers from David Hafler. <<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>> Your point is? He learned and then improved as any GREAT student should. He became the "Teacher" vs student.. It happens ALL the time.. A true teachers goal, is to make those they teach BETTER because of the WAY they teach. I sure had some good teachers.. Weather they rubbed off that is a different story.. :-) Carver made some hotrods for sure with LONG valve life.. He always had a hat on too.. Hafler was cult like, still is probably. I did some board changes for a buddy he was a BIG Hafler fan (1995 or so) I was more of a Pass and Mac guy at the time.. Cary wasn’t even on my radar, back then. They have one I fell in love with. V12r gosh what a great amp.. 3 years now. It’s an OLDER amp design BUT a Great idea.. EASY to repair voice too.. 12 to 200 watts. Add or subtract valves and bias.. That simple.. It was made for planars.. 4 EL34s Ruby or GL KT77 or 6V6s, it don’t care.. Put 12 valves in, bias, flip to UL and look out.. The little Carver is no V12r but it's been voiced to please for sure, with LONG valve life.. 1/2 the weight too. Regards |
on the caps in the Carver... Everything is built to a price point. If they charged $500 more for the amp they could use better coupling caps. I am sure it is a very nice amp. I prefer octal tubes in the front end, but anyway, changing the coupling caps to something better will not hurt the amp and will probably sound better. If you don't like it, put the old ones back in. Warranty voided though, you have to take that into account. |
Status Update-- I have all of the power tube coupling caps in, which consist of 4 .68uF and 4 .1 uF Clarity CMR caps. I have yet to touch the two .22uF caps near the gain/phase section of the circuit--arguably those could do more to signal preservation (I'm waiting on VCap CuTFs to arrive for that section). I also replaced the four resistors linked to the larger .68uF coupling caps with Kiwame 5watts, .39kohm and .36kohm. I'll spare you the audiophile shopworn terms, and we are only 8 hours into break in. The new caps make things sound more relaxed and less tense. I don't mean relaxed in the sense of more laid back, but rather less uptight. I know this amplifier, very, very well. With the cap swap, on Johnny Hartman's "I Just Dropped by to Say Hello," things don't sound as intense. There's a bit of strain in those old caps (Suntan, brand anyone?). The Clarity's are clearly more detailed and it's easier to pick out the space around instruments and voices. Piano sounds like the recording was voiced better--mics placed more correctly--when it's the same recording. The originals had more a feeling like we were driving at breakneck speeds and while we never drove off the guardrails, a sense that we could was there. That made the amp exciting, and even though it was pretty darn smooth, I'm now seeing where it wasn't. Here's a summation-- Old/Suntan Caps (<$1 ea) and Bargain Resistors (~pennies):
New Clarity CMRs (~$225 upgrade) + 4 Kiwame Resistors on the Coupling Caps:
From a subjective estimation perspective, I think this makes things sound 5-10% better and break-in has just begun. Notes for DIYers or Techs: Holy cow--I'd never desoldered lead free solder or at least like this. I had my Hakko up to 890 degrees and there were times I couldn't melt the stuff. I obviously used audio-dork solder (Cardas Eutectitc solder), which is way easier to work with and looks great. I actually had to carefully drill out some of the through holes on the PCB (not my first choice), as whatever is in the solder used by Wyred4Sound in construction is insane. There is virtually no room on the board to install these caps. I was sensitive to size when selecting. There are way larger options. After break in, I'll be adding silicone to adhere the caps down, and I may add some bracing to hold them. Honestly though, they are so snugly fitted that they aren't moving now. This was a tough surgery for me. I'm no hack, but I'm no pro either. I've built one point to point EL34 amp, 3 kits, and done plenty of mods in the last 5 years. This required a bit more patience. Carver could easily draw the board bigger as there's room in the chassis for this, which would accommodate bigger parts. He has massive real estate on the board for the big resistors but virtually none to upgrade those Suntan caps. Now, I cannot wait to do the VCaps and get through equipment break in and subjective break in. PS. Voltages measured better with the new caps too--for the objectives out there! There were spots where it looked like some DC was slipping through a cap on its output. Not much, but it was there. None with the Clarity Caps. Many more hours of listening to go though. I'm happy. |
One more EARLY listening note.... On Walter Wolfman Washington's "Lost Mind" from the album "My Future is My Past" (opening track): The opening soliloquy where he's pouring a glass of bourbon (presumably) sounds creepily authentic. I can hear the room he's in much more. I had to listen to it many times out of curiosity and pleasure. The acoustic guitar now sounds to recorded properly. Before I thought it was buried a bit too much and not defined enough. Now it's right there. Let's hope these caps don't make anything sound worse--especially poorly recorded stuff. ;) |
jjss, I think you deserve MVP of Audiogon's forums! You have great knowledge, are a team player, and oh-so-hilarious! I used to be single malt guy. Now bourbon and a touch of the green scene. But, Sir, (assuming you are a sir), this was a tricky little upgrade! I would take 2X the time if I was doing this on someone else's amp! I actually called a woodworking friend to see about making a sub-unit plinth so I'd have more room. |
FYI--I'm actually considering setting up a swap out station for testing the .22 caps hooked to the phase and gain area of the circuit. The listening tests could prove to be worthwhile at getting this little guy to his full potential for me. Or, I'd drive myself crazy. Clarity CMRs are a wonderful cap though. They really are. |
Blasphemy--I know.... The VCap CuTFs arrived as I was only <12 hours into coupling cap break in, and I just moved forward. I don't want to wait weeks to go back into this amp again. The VCaps are in and there is a much bigger improvement swapping out the literally pea sized .22uF caps hooked to the DC phase inverter output to 12AT7 gain tubes (or at least that's how I read the board (again--I'm no pro). We are looking at a $500 modification total. I'd project the Company would have to charge an extra $1500 to do this. It sounds glorious. I hope the VCaps get better not worse. I know Chris specifies up to 400 hours break in. I'm not hearing that any is needed. So if it stayed here I'd be happy. |
'Johnny Hartman's "I Just Dropped by to Say Hello,"' @jbhiller, ahh yes! You have excellent taste. I'm not surprised by your improved sound quality. Not sure why some are skeptical about capacitor and resistor upgrades. In my experience they can be quite worthwhile if chosen wisely. Congratulations. Charles |
Charles, you are a guy that I've always wanted to have a beer or coffee with! Most of the folks who are skeptical lack experience in doing these things. I think Don Sach's word is valuable and it is without question he has such experience in spades. This little Carver amp is so lovely. I'm quite pleased. |
@jbhiller , Your post "Bob Carver, if you're listening, how about we collaborate on a Signature Edition of the 275? Woahhhh, where's my humility. Get back to your day job dude and let Bob work his magic. :)", You need to ask EJ Sarmento of W4S and Glass Audio America who is manufacturing the 275 about making an SE version of the Stereo 275, W4S makes hot-rodded versions of their gear so a Stereo 275 SE should be a shoe-in. |
@klh007 , That's a brilliant idea. Here's what I would think could be viable-- 1. Lighted Meter 2. Add Balanced Input option 3. Upgrade gain and coupling caps 4. Upgrade key resistors 5. Use Leaded Solder 6. Enlarge PCB slightly to accommodate caps--there's plenty of space in the chassis. 7. Add more substantial feet I'm thinking that would increase the price of entry by $1500-2000. From a business perspective, it would get the cost into the $4500-$5000 range, and I don't think it would step on the market for their 350 monos at $5k each because not everyone wants or needs that power. I have 100dB efficiency speakers in a sizable room (at least to me). I need one amp to do its best. I couldn't use the power of the monos if I tried. |
Wow. This thread is like a breath of fresh air. Gentleman posting really interesting and helpful information. Well done! @jbhiller Great job on the upgrade and pics. My OCD kicks in on these types of things so I can imagine some angst at removing the original caps without destroying the board. I have had time with a Primaluna HP integrated in the past but never heard the Crimson. Could you comment on how these two sound relative to each other? |
@jbhiller, I have to tell you that those proposed amplifier modifications/upgrades for a final product cost of 4500-5000.00 USD seems very reasonable and doable. This would be a high quality very good sounding tube amplifier with a price that is assessable for a fair number of people. @corelli +1 regarding the demeanor of this thread . Reminiscent of how this forum was when I joined about 12 years ago. Charles |
