Carver Raven 350 Review (Tube Amp)

[milosz]

Amir measured the DC resistance (0.47 ohm for high and 0.3 ohm for low tap) but rest assured the output Z will at least be higher than that and frequency dependent.

DC resistance is not the same as output source impedance; there is a relationship, yes, but an unpredictable one. The impedance would likely be higher, but if a lot of negative feedback were used it could be lower. (But I don't think this amp likely to have that much feedback) https://electronics.stackexchange.c...ve feedback,effective impedance at the output.

 

[amirm]

DC resistance is not the same as output source impedance; there is a relationship, yes, but an unpredictable one. The impedance would likely be higher, but if a lot of negative feedback were used it could be lower. (But I don't think this amp likely to have that much feedback) https://electronics.stackexchange.com/questions/511270/how-does-negative-feedback-change-output-impedance#:~:text=In a nutshell, negative feedback,effective impedance at the output.

That would require post transformer feedback which I don't think this amplifier has.

 

[AndreaT]

Upon review of the harmonic distortion there seems to be a lot of distorted signal around and very close to the 1 kHz fundamental, similar to the “jitter” graph of DACs. Is that a sign of transformers poor quality? I would worry it adds to the harmonic distortion contributing significantly to the “soup of sound”, especially detestable on a symphonic music signal.

 

[amirm]

Upon review of the harmonic distortion there seems to be a lot of distorted signal around and very close to the 1 kHz fundamental, similar to the “jitter” graph of DACs. Is that a sign of transformers poor quality? I would worry it adds to the harmonic distortion contributing significantly to the “soup of sound”, especially detestable on a symphonic music signal.

It is intermodulation with the power supply hum. Mathematically it creates the same sidebands as jitter (but has no frequency dependency).

 

[DonR]

This is interesting to me. Are noobs with big wallets buying a $9k pair of tube mono blocks from Carver? You almost have to be into gear a little bit to even know who Bob Carver is. The doctor/lawyer profile you mention i think would lean into McIntosh or a sick Yammy integrated. Something everyone has heard of. And then tubes on top of that. My guess is their clientele is tube loyalists who refuse to acknowledge measurements or feel that objective testing is flawed OR just have enough coin that they are just jewelry.

My dentist is into tube Schiit gear. Admittedly, he considers himself a bit of an audiophile but when questioned on room modes and adjustments he seemed to draw a blank.

 

[Balle Clorin]

Should be easy to Measure output impedance , just look at the output tap voltage drop with two different resistive loads, and calculate it . Remember I=Vload/Rload

 

[theREALdotnet]

DC resistance is not the same as output source impedance; there is a relationship, yes, but an unpredictable one. The impedance would likely be higher, but if a lot of negative feedback were used it could be lower.

Yeah, the DC resistance of a transformer coil has nothing to do with the amp’s output impedance. The output impedance at the speaker terminals is the output impedance of the circuit before the transformer, multiplied by the square of the transformer ratio.

 

[GXAlan]

Tubes always eludes me. I can't for the life of me understand the reason why you'd want a heat blasting element to produce sound for you, when chips already do the job well. Sure, yes, the argument about subjective sound quality I understand, but I personally wouldn't bother with tubes when I could just EQ through software.

I think that’s the thing. “A heat blasting element to produce sound” has the sort of functional artwork / anachronistic wonder that a mechanical wrist watch or manual automotive transmission achieves.

I can say that the Marantz PM-90 tested here sounds more tube-like [to my McIntosh MC2102 and Sonic Frontiers SFS-80 (Sonic Frontiers is Anthem today] present in comparison to my Kenwood L-08m from the standpoint that the phantom center feels wider and larger than life. That width of the image really makes good but not world class singers even better (imagine Hollywood actors singing). The Kenwood is more accurate, without question, in that orchestral and actual musical instruments sound better and even with LPs which have restricted stereo data, I am able to place speakers in the “intermediate” space between phantom center and left or right.

Just as solid state silliness talks about different op-amps or digital filters having “dramatically different sound quality” (which is mostly sighted bias), tube silliness leads to super high distortion and modern tubes which design for subjective performance rather than objective performance. In those cases, modern tube designers want to increase distortion so much that you can ABX it reliably and then the uncertainty of “better” versus “different” probably sells a lot of tube amps.

 

[solderdude]

Yeah, the DC resistance of a transformer coil has nothing to do with the amp’s output impedance. The output impedance at the speaker terminals is the output impedance of the circuit before the transformer, multiplied by the square of the transformer ratio.

Looking at the output it does have overall feedback (yellow wire at speaker high Z terminal) and uses (partly) current feedback in the speaker path (blue wire). It is there to lower the damping factor instead of increasing it (supposedly to 'read' the room).
In this case, when you need to cut a cable to keep it from exploding, I suggest to cut the blue wire. (or solder the brown wire from the - speaker terminal to the red wire (effectively removing the sense resistor)

The specs say: Source Impedance: 1.7 ohms no mentioning at which frequency and load.
Not actually measured so we'll never know if that is accurate, it will be load dependent for sure (due to V and I feedback).
That said the spec 85 kHz (–3 dB) is not confirmed by Amir and is about 70kHz which really isn't that bad nor is extension well below 10Hz (-3dB).
15Hz to 35kHz +/- 0.5dB is not that bad for an OPT tube amp.
The measured DC resistance thus may well be the secondary winding + feedback resistor (I have drawn in a red arrow)
Pictures clearly show strapped 4 and 8 ohm outputs b.t.w.

picture below is from the Carver website.

 

[Palladium]

Seems like the audio potential isn't unleashed until we replace with all the $4/meter internal wiring with $1000/meter ones.

 

[Balle Clorin]

Yeah, the DC resistance of a transformer coil has nothing to do with the amp’s output impedance. The output impedance at the speaker terminals is the output impedance of the circuit before the transformer, multiplied by the square of the transformer ratio.

Plus the DC resistance of the transformer coil

 

[theREALdotnet]

Looking at the output it does overall feedback (at speaker high Z terminal) and uses (partly) current feedback in the speaker path. It is there to lower the damping factor and this increase the output resistance (supposedly to 'read' the room).

Hehe, as far as output impedance is concerned, this makes for a very complex calculation

It’s much easier to just measure the output impedance.

 

[solderdude]

Plus the DC resistance of the transformer coil

+ the measurement resistor ... unless overall feedback is used (which it is, just very little of it) but that all is nothing compared to the 'room reading technology' (ahem DF worsener circuit)

It’s much easier to just measure the output impedance.

Yes it is, at various frequencies and load impedances in order to fully characterize it.

That said, it is intentionally a high output Z as Bob does not care how it measures just how it sounds and it must sound different than regular amps.
If the harmonics don't do it the 'room reading circuit' will for sure.
I figure plenty people (Bob Carver fans) will like or even prefer it over 'regular' amps.

 

[Mart68]

+ the measurement resistor ... unless overall feedback is used (which it is, just very little of it) but that all is nothing compared to the 'room reading technology' (ahem DF worsener circuit)



Yes it is, at various frequencies and load impedances in order to fully characterize it.

That said, it is intentionally a high output Z as Bob does not care how it measures just how it sounds and it must sound different than regular amps.
If the harmonics don't do it the 'room reading circuit' will for sure.
I figure plenty people (Bob Carver fans) will like or even prefer it over 'regular' amps.

They will. Also they will partner it with some 'designed by ear' loudspeakers. Then go round telling people that as their system has become more revealing so many more recordings have become unlistenable.

 

[JimFarrell29]

Why not both? No rule that says you only have one system,

There is a circle of confusion that is well established. Sometimes the music you like is not the best recording, or the music you like isn’t the best performed. I really enjoy listening to the La La Land Soundtrack, but Emma Stone and Ryan Gosling are not professional singers. When it’s too transparent, it quite simply does not sound as good as when played back through perhaps less resolving or euphonic gear.

At the same time, with a wonderful recording like the Steinway & Sons sponsored Nutcracker Suite rearranged for solo piano, transparency is rewarded.

Exactly. I use a 12.5 watt SET 300b amp for jazz and acoustic music and a 215 watt solid state amp for rock and classical. Why ? Because I love how they sound and I am in the lucky position to be able to afford to run two amps. I am less concerned about fidelity to the "as the artist intended" argument as many artists like highly compressed shit versions of their own work. What concerns me is how they sound when I listen and some music just sounds better to me on tubes. I guess I am just a distortion junkie.

 

[DMill]

My dentist is into tube Schiit gear. Admittedly, he considers himself a bit of an audiophile but when questioned on room modes and adjustments he seemed to draw a blank.

I get that. I hope he’s a better dentist than he he is a student of electronics. That said Schiit stuff is nowhere near $9k for a pair of amps. But your point is well taken. Someone must have told him Schiit was good. Not like he got talked into it at Best Buy. Ask him how he heard of them next time you get your teeth cleaned.

 

[EchoChamber]

I just love those tests… All that distortion drives the traditional audiophile market so you are always looking to upgrade to that other distortion from that other tube amp that just sounds sweeter because of the tube, or the transformer, etc, etc…

I’m happy I have my boring pro audio gear and shielded from the audiophile hype.

 

[theREALdotnet]

Yes it is, at various frequencies and load impedances in order to fully characterize it.

Indeed. The dependency of the output impedance on frequency is intuitively understood, the dependency on load probably less so. But it doesn’t take a lot of effort to measure either.

 

[Mnyb]

Well besides performing terribly , this carver actually produces power , which the other one amir tested did not , so it actually is an power amp .
And that's the most important factor with today's inefficient speakers.

is not fr response the most deciding factor in audio , so can one assume that the random fr response modifications due the output impedance vs speaker impedance colors the sound more than distortion components ?

I've never experienced distorsion making anything sound better imho ( except guitar amps ) I'm starting to thinks this also is an myth .

Also what about IMD no one likes that . As i learned the nonlinerity in the amp the causes the THD also causes IMD so you really cant have one without the other

 

[pma]

I've never experienced distorsion making anything sound better imho ( except guitar amps ) I'm starting to thinks this also is an myth .

It is a myth. With the exception of hard clipping and severe crossover distortion. Most people in fact have no idea how the polynomial nonlinearity sounds like.