Carver Raven 350 Review (Tube Amp)

[Hipster Doofus]

Listening to 1960 tubes now , amazing …. they have built in equalizers and great speakers, better then my topping pa5

Hmmm is that why when I used a Denon audyssey sweep on my tube mono locks it was way too loud

sorry about posting twice

 

[GXAlan]

One of these days Amir is going to measure a tube amp that measures decent, and maybe exposing this type of money grab is a good thing.

So yeah someday our host is going to measure a respectable tube amp, because I know it can be done.

The biggest problem is tube amps are disproportionately heavy and disproportionately fragile so shipping is hard.

Second, the tubes built in the era where quality was important because they may be used in instrumentation are not the tubes that have stable supply chain (for pricing). Even Sidney Corderman, who came from the school of thought that tubes should be clean, has suggested that the best tubes are 6550A’s but not practical to use, which is why they ship KT-88’s

I still don’t think you will get into the 80’s for SINAD though.

Does anyone have a 6DJ8 based product for Amir to test? I will supply my stash of JAN Sylvania 6DJ8’s to the effort.

 

[lhimelfarb]

I'll do some scans as evidence. Nice sound is one thing, -40dB distortion is quite another and believe me, some of the expensive tube based preamps they did were effects-generators/sonic processors if compared to a straight-through source... The Reference 2 preamp I remember was awfully coloured, as was an LS25 and lord knows how they measured. Early ARC power amps didn't care for UK voltages either and VERY EXPENSIVE blow-ups were common at one time if not now. Seriously, a collection of WonderCaps or whatever they use these days is no substitute for proper design, but audiophiles aren't so interested in the latter as long as it's a conversation piece to show off to their pals. I admit I went off the brand and now regard them as male jewellery, the same as a lot sold by Absolute Sounds in the UK.

Carver products were always poor in my opinion... just cheap per watt. Most tube amplification sounded syrupy back then compared to the newer technology of solid-state. So? I repaired Carver and Phase Linear solid-state amps left and right. They shorted more than tube amps... and when they went, unlike tube amps, so did your speakers. That was then, now it is different. Don't believe for a moment that ARC products only have a 40 db s/n ratio and lots of distortion... they don't. They are clean and noise free, unlike most of the tube stuff on the market today. The best sound for your money comes from solid-state... but you can design tube circuits to sound and test really well too. The problem with tubes is more about the available tubes than about the technology. Thank goodness there is no need to buy tube circuits any longer. Related to this site... well... they test what they can afford and what their followers can afford. Amir knows his market.

 

[Deleted member 50971]

The biggest problem is tube amps are disproportionately heavy and disproportionately fragile so shipping is hard.

Second, the tubes built in the era where quality was important because they may be used in instrumentation are not the tubes that have stable supply chain (for pricing). Even Sidney Corderman, who came from the school of thought that tubes should be clean, has suggested that the best tubes are 6550A’s but not practical to use, which is why they ship KT-88’s

I still don’t think you will get into the 80’s for SINAD though.

Does anyone have a 6DJ8 based product for Amir to test? I will supply my stash of JAN Sylvania 6DJ8’s to the effort.

In my opinion the tubes are not the weak link, and maybe one of the more knowledgeable people would comment about this. I think it’s the technology that they’re using, or misusing, and their goals are skewed. In my opinion they’re doing some of this on purpose, because there’s no reason for these kind of measurements in this day and age.

Level match them with something solid state, and you’re more than likely going to hear the difference. It’s that difference in sound that they are going after, instead of making it transparent like most of the solid-state gear is. That should be the goal to make them transparent… but then maybe they wouldn’t sell so many. Just listen to that euphoric distortion, only they don’t tell you it’s distortion.

 

[Thermionics]

Now this is 1958 technology. Nostalgiacs should wallow in it. These were the measurements we battled back then; it brings a tear to see them back again -- from the mud in my eyes and ears. By the way, the DC resistances of the output windings of a tube amp are almost meaningless.

Expensive as a good used car, and for that you get boatloads of harmonic and intermodulation, a gaggle of glowing tubes, and a space heater. It may even make a flute sound more like an oboe. A Bourdon more like a Posaune.

This is like stick shift and 4 carburetors on a straight 8, but in an amplifier. Nostalgic! 1958 muscle.

Unless you are physically incapable of using a manual transmission (or it is an EV), a stick shift is *always* the right answer.

 

[Thermionics]

Hard to know -- it's where it would make sense to test.

The EL34 and 6550a are identical sockets, so you can use the same exact amp and just swap tubes. If you ran both tubes at the lower EL34 bias or both tubes at the higher 6550a bias, the question is if there is the same sound quality? Maybe. But if the EL34 wears out faster because you are running too much current through it, then it's going to change the sound and then it's like comparing a worn out tube versus a new tube.

Is there a difference in sound between worn out and not worn out tubes? definitely. Some of it is as simple as gain/volume.
Is this difference slow/steady or a cliff? Not sure.

It's not just bias - you are also going to have different optimal OPT primary resistances between 6550 and EL34, depending on B+.

 

[pablolie]

In my opinion the tubes are not the weak link, and maybe one of the more knowledgeable people would comment about this. I think it’s the technology that they’re using, or misusing, and their goals are skewed. In my opinion they’re doing some of this on purpose, because there’s no reason for these kind of measurements in this day and age.

Level match them with something solid state, and you’re more than likely going to hear the difference. It’s that difference in sound that they are going after, instead of making it transparent like most of the solid-state gear is. That should be the goal to make them transparent… but then maybe they wouldn’t sell so many. Just listen to that euphoric distortion, only they don’t tell you it’s distortion.

Tubes are a "limitation". Most tubes are single transistor, anode-cathode stuff. Kinda hard to build advanced circuits with feedback and correction based on tubes, solid state allows you to print a zillion transistors and advanced logic and what not. Tubes also operate at much higher voltages than transistors - makes them easier to be a heat and even fire hazard. Tubes' longevity is also so-so (think incandescent bulbs and how happy many of your are with LED bulbs), hence plan on keeping spares... And tubes also have quite significant manufacturing inconsistencies (manual stuff going on, really), making matching key... which often manifests itself in channel measurement inconsistencies. And your need to keep spares that match.

I am not saying the limitation is an unsolvable problem for enjoyable audio experiences. There have been some great tube designs, but engineers with that core expertise have long retired. Personally I don't trust tube designs these days, it's build on the "vinyl and tubes are a match made in heaven" mystique without the infrastructure to back it up: tube manufacturing is a niche, tube design practices weren't even taught in engineering school when I studied in the 80s, so who really has access to know how or top manufacturing?

When people bring up tube designs that measure "well" (which is always merely OKish at best), it's some vintage gear that probably doubles as a fire hazzard in your home.

That said - I have a friend with a tube amp that I thoroughly enjoy listening to with certain types of music. :-D

 

[Thermionics]

Anything is a fire hazard when the magic smoke gets let out.

 

[Steve Dallas]

Unless you are physically incapable of using a manual transmission (or it is an EV), a stick shift is *always* the right answer.

You are close. A stick shift Miata is *always* the right answer as evidenced below:

Miata
Is
Always
The
Answer

 

[Deleted member 50971]

Tubes are a "limitation". Most tubes are single transistor. Kinda hard to build advanced circuits with feedback and correction based on tubes. Tubes also operate at much higher voltages than transistors - makes them easier to be a heat and even fire hazard. Tubes' longevity is also so-so (think incandescent bulbs and how happy many of your are with LED bulbs), hence plan on keeping spares... And tubes also have quite significant manufacturing inconsistencies (manual stuff going on, really), making matching key... which often manifests itself in channel measurement inconsistencies. And your need to keep spares that match.

I am not saying the limitation is a necessary problem. There have been some great tube designs, but engineers with that core expertise have long retired. Personally I don't trust tube designs these days, it's build on the "vinyl and tubes are a match made in heaven" mystique without the infrastructure to back it up: tube manufacturing is a niche, tube design practices weren't even taught in engineering school when I studied in the 80s, so who really has access to know how or top manufacturing?

When people bring up tube designs that measure "well" (which is always merely OKish at best), it's some vintage gear that probably doubles as a fire hazzard in your home.

That said - I have a friend with a tube amp that I thoroughly enjoy listening to with certain types of music. :-

I will agree that they are a limiting factor, but they are not the only thing limiting this amp. My point is that manufacturers can do better than this, and make something with better specs.

 

[Cars-N-Cans]

Oh no, it is quite easy and safe. I made dozens of such tests without a single damage. Of course you have to use resistor voltage dividers or stepped attenuator to keep the right voltage span. But it is easy to do, is not it?

Some care is required with single-ended amps, though. The usual arrangement is for the input and speaker common to be tied together in a star-point inside. This means that if the amp is hooked up backwards, it’s output is shorted to the common signal ground if the amp and ADC will be sharing a common reference. The other method would be to use a ladder and tap the ADC off if it can be kept floating relative to the amp. But what is referenced to what is an important consideration so you don’t burn things out. I’ve done exactly the same thing, but when everything has to share one common ground reference I’m sure to ohm things out before applying power to be sure or PCB tracks will be blown off all over the place. Edit: You could also use a signal transformer, but then you have to find one that doesn’t introduce its own distortions.

 

[pablolie]

I will agree that they are a limiting factor, but they are not the only thing limiting this amp. My point is that manufacturers can do better than this, and make something with better specs.

I agree - but clearly, why would they when their target market doesn't care and basically prefers the visual psychoacoustic effect of the glowing tubes (why doesn't anyone keep them really protected :-D)? Furthermore, tube supply is very limited, its manufacturing standards doubtful (especially with the Russian situation), and implementation know-how in industrial design a forgotten art... ? Just check the review results of every recent tube design tested in here....

 

[BDWoody]

it's some vintage gear that probably doubles as a fire hazzard in your home.

With some high power amps having a plate voltage upwards of 600v, you can add electrocution hazard to the mix.

Some of those old boxes scare this non-expert.

 

[dougi]

I am actually going to try a tube amp again after a long break. I had a Rogue audio Cronus integrated in the 2000s (original EL34 based one) that was always noisy and blew up the rectifier bridge and PS caps out of warranty. (I did use it as my main amp so a fair bit of use, but it probably didn't help the 85 deg rated only caps quite near an output tube). I fixed it, modifying to accept 105 deg caps and sold it a year or two later.

The "new" one (well old demo stock, who knows how old given made since 2010) will be an ARC VSi60. With a JFET front end it will be quieter than the Cronus (it had better be) with a bit more power (KT120 in 6550 circuit but capable of at same bias). Distortion expected to be better than this Carver (going by tests) and quite flat v freq. Why did I buy it? 50% off original RRP helps. But just to try it really and don't expect to be blown away (except when a tube fails and I have to replace a protective resistor apparently). New ARC prices are pretty silly now. Getting spare tubes at the moment, of course, is a different subject.

 

[pablolie]

With some high power amps having a plate voltage upwards of 600v, you can add electrocution hazard to the mix.

Some of those old boxes scare this non-expert.

They scare me.

I know of 2 instances when tube amps caused house fires. Admittedly, it was due to user mistake (I didn't rub the fact in).

The electrocution hazard also exists with solid state devices, too, so each and every one of you be mindful of that and use best practices when opening up any electronic device. Big capacitors in solid state designs and digital power supplies can eff u up...

 

[Thermionics]

You are close. A stick shift Miata is *always* the right answer as evidenced below:

Miata
Is
Always
The
Answer

Miatas are fine (especially the first generation MX-5, but I'll stick with BMW (not the new rubbish they're flogging, the old E-series stuff).

 

[DonR]

Miatas are fine (especially the first generation MX-5, but I'll stick with BMW (not the new rubbish they're flogging, the old E-series stuff).

M539 Restorations. All the classics, none (or very little) of the new garbage.

 

[BDWoody]

Miatas are fine (especially the first generation MX-5, but I'll stick with BMW (not the new rubbish they're flogging, the old E-series stuff).

Gotta agree there...I'll 'stick' with my e92 m3.

 

[Steve Dallas]

Miatas are fine (especially the first generation MX-5, but I'll stick with BMW (not the new rubbish they're flogging, the old E-series stuff).

Why hold back? Have one of each!

And one of these for good measure!

 

[amirm]

True, but this reasearch only shows that many forms of distortion are even less audible. I did the Klippel Test and managed to hear abour 53dB on test tones, which is already much more than the average (maybe I got lucky). On music material it is much less audible. So in fact 1% distortion, which is 40db, should be quite save to be inaudible in music.

Let's not go overboard with these statements. Here is a published ABX test showing differences between amplifiers: https://www.audiosciencereview.com/...ts-did-show-amplifiers-to-sound-different.23/