Equalization for vinyl nirvana

Nice list of equipment, you should be in Vinyl Nirvana without additional EQ.

I like adjustable preamps. I am still suspicious of your preamp settings, and now also wondering about your amp settings. Options are terrific, UNTIL they aren't.

It is easy to check and verify correct or adjust them on both pieces.

Your phono preamp has internal adjustable settings: 5 optional load settings; 5 optional gain settings. Note: separate settings for each channel, verify they are set identically.

https://sutherlandengineering.com/wp-content/uploads/2021/03/Sutherland-KCVibe_Mk2-OwnersManual.pdf

they don't say what the factory defaults are.

For MM cartridges, like your Clearaudio Virtuoso,

the preamp setting recommendations are: Load: 47k; gain: start with 45db (see if enough volume, more gain if needed). I suspect you need more gain, see below.

Sidebar 1: Specifications

Description: Moving-magnet phono cartridge. Stylus profile: Not specified.  

Output voltage (1kHz, 5cm/s): 3.6mV. 

Frequency range: 20Hz-20kHz. Channel separation (1kHz): >30dB. Channel balance (1kHz): <0.2dB. Trackability: >90µm. Recommended tracking force: 2.0-2.5gm. Electrical impedance (1kHz): 660 ohms. Coil inductivity: 0.42mH. Load resistance 47k ohms. Load capacitance: 100pF. Cantilever: aluminum.
Weight: 6.0gm.
Serial number of unit reviewed: V00873.
Price: $750. Approximate number of dealers: 160.
Manufacturer: Clearaudio International, Weberackerweg 10, D-8520 Erlangen, Germany. Tel: (49) 9131-57702. US distributor: Musical Surroundings, 5856 College Ave., Suite 146, Oakland, CA 94618. Tel: (510) 420-0379. Web: www.musicalsurroundings.com.

Note: Your cartridge output: 3.6mV is lower than many/most MM. I suspect, after you verify correct load settings: a higher gain setting in the preamp will improve things. Not enough phono gain requires more gain down the line, perhaps a boost in the preamp gain will move another component back into a more compatible setting.

Your Integrated Amp is like an identical twin of my Cayin A88T

https://www.stevehuffphoto.com/2020/12/23/hifi-the-willsenton-r8-integrated-tube-amplifier-is-a-no-b...

You have the advantage of rear switch for KT88 or EL34 tube types, AND Bias meter and bias adjustment screw (they even provide a screwdriver).

You also have optional Triode or Ultra-Linear. I much prefer the sound of KT88's to my optional 6550's; and much prefer the fuller and more impactful sound of ultra-linear mode. Note: you can change modes while playing. You don't hear/have a volume jump when switching (as I expected); you hear the differences of frequency presentation. I realized, the power difference shows up at the far end, the speakers ask for the same amount of juice at mid volume.

The review has a video showing the bias procedure, but first verify the rear switch is in the EL34 position.

PS: that stylus

https://www.stereophile.com/phonocartridges/737/index.html

has a LONG cantilever. Rarely, but worth checking: that can lead to trouble if it gets 'bent', as my friends high priced Grado is (and a prior stylus of mine was). His plays, he never checked. I had a good look, found it bent. To keep using it 'bent', I had to make a big adjustment to his arm height, raising it to adjust the stylus VTA properly. The darn thing sounds pretty good, certainly better, but it is time to get a new cartridge.

I stand firm: you should have Vinyl Nirvana with your current equipment.

One last thought: the 6SL7 and 6SN7. We think the Power tubes make the big difference, but when I changed a set of my 6SL7's the amp sounded thin, cold, thank god it sounded great before so I knew it was the 6SL7's. Brent Jesse let me finish breaking them in then return them for a pair I love the sound of.

Tube rolling is a rabbit hole to go down. Do you have the factory KT88's? I would suggest using KT88's, rear switch in KT88 position, warm up, adjust bias, change to Ultra-Linear mode. 

After I first checked/adjusted the preamp.

Phono preamps definitely sound ok, good, great, and I advise having the option of return for any phono preamp. However, what you are describing/intending is far from normal.

I agree, something else is wrong, additional eq after RIAA phono eq should NOT be needed, especially for all LP's.

RIAA phono equalization 'curve' grew into the standard for the LP recording/playback industry. ALL modern LP's are cut using reduced bass and boosted highs as per the RIAA spec. ALL modern Phono preamps boost the bass and cut the highs as per the RIAA spec. Minor, very minor differences result, by random parts deviation, or by designer's intentions, repeat very minor.

Prior to that, various recording/playback equalization 'curves' existed. Some phono stages, like the Sunvalley you mentioned, offer the RIAA standard, AND optional curves, intended for playing ancient lps recorded with those historically optional eq curves. Yes, you can use them with modern LP's but that is not their intention. This exists for Reel to Reel tapes also, early eq curves until a standard emerged.

LP, ' long playing' records, getting more content on a disk, was made possible by cutting the bass during recording (thus physically smaller width grooves were needed), and, like Dolby later, boosting the highs helped to reduce noise on playback.

Is your cartridge MM or MC?

Perhaps your Phono Eq has internal optional switches, resistors, settings for various cartridges, and current settings are 'bad' for your cartridge.

I would check with the manufacturer, and, go to eBay or Amazon, pick something you can return, try it, all should be well. If not you have problems down the line.