Enough power to drive speakers? (Audio Research vs NAD)

Hi!

I just bought the NAD C275BEE power amp, paired with Audio Research SP14, together these amplifiers drive my Dali Suite 2.5 speakers.

It sounds to my ears..wonderful! Specially since the phono input is tube driven.

Now to the question, i just saw a Audio Research VT60 for a good price here in Sweden and wonder if it will be a upgrade from the NAD C275BEE power amp? I can almost sell the NAD for the price that the VT60 is selling for.

Going from a 2x150watt solid state to a 50w tube power amp? (Will the sound be better?)

Dali recommends 30-150w 8ohm amplifier.

 

I cannot find speaker specs on 2.5, but 2.8 are 90dB sensitivity. At 90dB sensitivity 50 watts should be ok unless you are using at times outdoors for a huge dance party. Tube amps usually sound better than SS. But, your NAD 275 is no slouch in audio quality performance. But, the VT-60 is a fine amplifier. 6922 preamp tubes are very nice. I like Siemens 6922 & the 6550 is the best sounding high power output tube IMO.

 

Yes, that’s a good amount of power for those speakers. ARC would be a big step forward over the NAD unless you like to listen to music at a very loud volume. Like loud enough to make your ears ring. That’s what a 50 Tube amp won’t do.

 

Jacob

I'm familiar with the VT 60 and it is a lovely amp. However, I'm always cautious about changing things that sound "wonderful". Been stung a couple times doing that. If, for example, your NAD has deep tight bass, and you like that, a VT 60 will likely go as deep but, in my experience, won't have that tight punchy SS bass. The amp, speaker cable, speaker interface will also be different. Sometimes that will improve the sound, be the same, or be worse. That's why a good listen before you buy is so helpful if that's possible. My two cents.

Enjoy.

 

Very few tube amps can compete with very tight bass produced by 50 watts and higher solid-state amps. Tube amps than can compete with some solid-state amps are ridiculous power like 200 watts per channel. 200 watts per channel of tube power is expensive to manufacture and the large lot of replacement output tubes can cost a fortune.
The reason for tight bass from solid-state amps is the very high dampening factors from solid-state amps. Dampening factor is how fast a voltage rise comes from the amp. Fast voltage rise helps control the heavy bass speaker cone. Some bass speakers are sensitive to low damping factors and can sound bloated. However, I will accept less crisp bass if the bass is still reasonably tight & musical.

 

Damping factor describes the ability of the amplifier to resist change in its output signal.

If you know the load impedance and the output impedance you can calculate the damping factor by dividing. Transistor amps may have a low output impedance (say 0.01 Ohms) so with a load impedance of 4 Ohms you would have a damping factor of 400. Note that valve amplifiers drive the speaker through a large transformer increasing the output impedance and this lowers the damping factor considerably. A value of 20 is not atypical.

I am not convinced that damping factor and sound quality are related.

 

It depends upon your take on the system sound now. If you are not turning your preamp volume control up much past 10 o'clock now, and your system sounds a bit brighter than ideal, the tube amp would be a nice upgrade. The tube amp will improve the 3D soundstaging of the set-up and make it smoother and warmer sounding overall. If however, you find the system to sound a touch dark and fat now, then the tube amp will just soften that even more. There is some trade-off between a sweet and 3D midrange and top end with a tightly controlled and dynamic bass and treble response between tube and SS amps.
-Bill

 

Maybe not directly related to how we often define sound quality, but it is a fact that the dynamic output impedance of many tube amps working with a dynamic speaker impedance will change the frequency response of many speakers from what they would be with a typical low output impedance SS amp. Might be for the better, or maybe not.

I like my CJ tube amp, but I like some SS amps too.

 

You are right. Most tube amps have a dampening factor spec, but not the slew rate. I was actually referring to fast slew rate that usually goes hand in hand with high dampening factors. Dampening factor more relates to amplifier impedance. Tube amps are not as low impedance output as most solid-state amps.

 

I hate to be picky but I believe we should use "damping" and not "dampening" in this context.

Is it "damping" or "dampening" when referring to sound?

 

First, let me say that I am a BIG fan of ARC gear (check out my equipment profile). I would expect that the combination of the SP14 pre-amp and NAD amp -- a tubey sounding pre-amp with a somewhat complementary sounding more modern solid state power amp -- probably sounds pretty well-balanced.

Keep in mind that the SP14 and VT60 are both older products with a lot of "bloom" in their sound. You may like the combination of the two if you like a warm vintage tube sound, but it is going to be quite romantic (possibly verging on dark) and the bass probably won't have the more precise enunciation that you are currently getting from the NAD.

 

Thanks for all the inputs!

I've talked to the seller with the VT60 and the tubes are like new, the condition overall was very nice. I'm going to visit him tomorrow for a listening session and hopefully bring it with me home
The price is really good, 830 USD (If i convert the swedish SEK to USD with todays exchange rate)

Going from Harman Kardon HK980 with Pro-Ject Phono Box SE II to NAD C275BEE and ARC SP14 made the sound a little bit darker, fuller and with a lot more punch even on low volumes. (Sometimes almost to much bass since i live in an apartment) I can barely adjust the gain stepper control on the SP14 more than 3-4 steps, more than that would result with cops knocking on my door.

I'm hopeful that the VT60 will give more dynamics to the overall soundstage with more tube sound!

 

The VT60 is a nice amp and I have heard a few examples over the years. I own the more modern descendant VS60. I would have a look at the boards (top and bottom) in it for aftermarket modifications and shoddy repairs as you sometimes find both in older ARC pieces. The boards in those can also sometimes corrode if they are exposed to a lot of marine air. If you do buy be sure to check the bias when you get it home and installed.

 

Could be a change you may not like very much.......NAD is already a warm'ish sounding amp, so changing to tubes you may not notice much but as other say a slight drop in how you perceive the bottomend, can affect your overall feeling. To make up for the loss in lowend, possibly, you would have to tube roll and that can be spendy and time consuming.

The C275BEE offers 50amps of peak current output, which is a huge factor in driving speakers so they can sing their best....not sure what the AR is but I would guess in the 20-30 range, dunno. For this size amp, 50A is quite a lot......
The NAD PowerDrive circuitry is pretty sweet too.....performs above specs.

 

Thanks for your reply!
The seller checked the bias today and told me that the values on the voltmeter indicated that the tubes were like new.

I'm aware of it but still hopeful I'm not going to sell the NAD before i've had a couple of weeks of listening to both amplifiers.

 

^ Good plan

 

Good luck and keep us informed. You have us interested.

 

I agree.

Jacob, in this case I would definitely try to lend the VT60 home for a longer period if possible and evaluate if it's what you're looking for. Before I got my Bryston power amp I had a NAD S200 power amp, the synergy between the S200 and the ARC LS17 was indeed special so I would definitely evaluate the VT60 before buying it .

 

Picked up the VT60 a few hours ago.

The amp sounds fantastic! Listened to a few songs on apple music, Blondie - Parallel lines on vinyl, now moving on to Pink Floyd - DSOTM and i'm sitting here in my sofa with a big smile on my face

To be a little bit more analytical between the NAD and the ARC... I think that the VT60 (ARC) sound is a tad brighter with a lot more midrange and smoother bass, not necessarily less bass but not that distinct compared to the NAD. Definitively improvement on the overall soundstage!

Cheers and thanks everyone!

 

Beautiful picture! Enjoy

 

Congrats & enjoy. I found out long ago you just cannot beat the quality sound the better tube amps produce. Perhaps something out there in SS equals tube amp performance, but I am not sure about that.

 

BTW- if you can find early Siemens 6922, these are the best sounding 6922 per my tests. RCA 6922 gold pin with Made in Germany marked on the tube box are early Siemens. I believe these early Siemens use the .028 grid wire as used in the extra high quality, expensive and ultra rare Siemens CCa.

 

Not only that but they just look fantastic.

 

Very nice, there's something about the glow of tubes in a dark room.