ampsandsound Ovation review

A few notes on toob rolling for those getting this amp, but some disclaimers:

1. First of all, I do not consider myself a tube roller. I hate tube rolling.
2. If an amp needs good or exotic tubes to sound great, then it is a piece of shit.
3. I prefer to roll transformers, so FU.
4. It's not that I don't roll tubes. I will try different stuff over time. It's just in the time I may try something different, most people (in this hobby are finicky) will have sold their amps. When I roll and hear something I like, I keep it. I don't keep rolling in the hopes that I will get something better.
5. Rolling tubes is not conducive to enjoying music. Listen to music. Don't listen to tubes.
6. If you listen to tubes and wear out the tube sockets, Justin will probably think you are an idiot but not say that to your face. I will say to your face that you are an idiot.

That being said:

5751
New Production Tung-Sol or JJ. Don't wade into the morass of exotic vintage 12AX7. That is unless you really know what you are doing. All of the good stuff is gone or well used. All the good stuff for that is available probably has serious channel mismatching. High gain 9-pins can be very problematic. I have a fancy Amplitrex tube tester so I know. You really don't want to know. Tung-Sol serves it more straight up and is higher quality (bell curve applies still). JJ sounds more tubey, but that's because their quality isn't as good.

1626
I preferred the vintage RCA over the vintage Tung Sol. The RCA was more full bodied and more relaxed. The Tung Sol was leaner with sharper transients. Wasn't huge difference, but notable. Go bonkers on Ebay. They are dirt cheap. Price in a 25-30% fail / unacceptable rate. Trying out a few different brands and types would be a good idea here. Wearing out the tube sockets is not.

 

2V input to simulate full range output from a typical DAC. Volume control adjust so output is 0.850Vrms (it's a stepper, so hard for me to get an exact 0dBU or 0.775Vrms). This is enough to drive an HD650 to 100db.
1kHz into 300-ohm load. Low Z secondary output tap. 0dbR normalized to 0.850Vrms.


Thoughts:

• THDN is about 0.04%. Second harmonic is under -60db down. It's fine. Consider that Amir the self-proclaimed audio scientist could NOT HEAR the distortion in the plate amp of the JBL305X which was MUCH WORSE and he even said the of the JBL305X "It gives a smooth, very realistic sound impression, beating many "hi-fi"...It is hard to believe such great performance can be had for so little money in the form of XXX. We get it because of research and measurements like I have been showing that resulted in the XXX." (https://www.superbestaudiofriends.o...audio-science-review-review.9827/#post-316078)
• The pattern of the distortion is a good and typically seen in SET. Each successive harmonic is lower than the prior. We don't see odd level harmonics that go on forever and remain high. With some SET amps, the higher harmonics drop faster. Here they stick around and contribute to what is commonly associated as a "rich" sound.
• AC mains hum is -80db before the fundamental. That's Dolby C NR on a high-end tape deck with the best metal cassette tapes back in the day. You ain't gonna hear this (HD650 use case). The hum on the L channel is a bit higher and probably attributes to contribute to the grass and IMD with the 1kHz sine and its harmonics. I don't worry about this. Hum grass with a regular pattern up the range doesn't sound like shit. The kind of grass that sounds like shit is the uneven spurs from 5kHz onwards - often seen with bad switching power supplies.

Similar to above, but with 100-ohm secondary tap (second highest to high Z). 0dBr normalized to 0.725Vrms


Note: volume knob is adjusted down a bit from the higher Z taps to maintain somewhere close to 0.775Vrms. The output is higher. As is the output impedance which will affect bass to varying degrees of dynamic headphones depending upon their impedance curve and also transient response of headphones.

 

For Grado test case, let's set output to about 0.075Vrms (0dBr). 32-ohm load. Low Z output tap.


L channel 60Hz hum is -60db down from full output. I would have liked to see the left channel down to -75db to match the right channel. It's iffy and borderline here at -60db on the L side. However, I will reiterate that I did not hear any hum with the Grado RS2s. I would not say that I am the most sensitive person to hum though (turntables, vinyl, and all). Younger ears and those who grew up with digital and ProTools processed recordings with noise-reduction plug-ins or inside anechoic chambers may be more sensitive to this.

The grass (hum harmonics) are present throughout. I don't think this is problematic because it looks a lot worse than it really is. (Speaker amps tend to be like this and no one has bitched about it for decades). The grass is -90db down. No one can hear this shit. You'd have to be blasting music at 100db and be able to hear a pin-drop. (And remember, the limit of 16-bit audio is 96db - and much of "Hires" is upsampled 16/44).

 

A final note in closing with respect to tube rolling. Some of the green lettering has faded, but a what I think is a Sylvania JAN 5751 in the photo below. If you want something different (and I think better) than the new production Tung Sol. This tube is just slightly dark sounding, but has a more robust presentation in the direction of an octal (6SN7). The downside is that they are harder to find and are getting pricier. As another owner mentioned, lots of tube rolling options here. I actually just bought a pair of these myself.



Pro tip: if you buy from EBay, look for sellers with no less than 99.9% rating. Also, sellers with an Amplitrex or other capable tube measurement to make sure the gain is as close to possible for each triode in the tube. Another method is to find the same plate and internals but branded differently. Sometimes deals can be had here for the same tube.


Skull Pyrate poses in victory over Pink Panther, showing once again the limited and often misconstrued nature of SINAD