Concerningly loud pops in vinyl playback

Thanks again all, really good ideas here!

Replaced the 2 regulator tubes in Ref 6. Greatly enjoyed my music yesterday with no incident, though I didn't budge the Ref 6's volume past 40 max (if I'm in the mood I might like to go up to ~ 42 :)). Other than this issue the small room system has really exceeded my expectations; so nice. 

I did order an AQ Niagara 3000 from TMR; the gear in here deserves it, even if this isn't a power issue. 

Also have the Hudson Hifi brush/wand thing on the way - these devices never really appealed to me, but it's cheap enough to buy & try. Got a humidifier too; just need to hook it up. 

I hooked up the "optional" bearing ground wire to my Clearaudio, but it's not clear to me where the other end (small spade) goes. I've put it on the phono stage for now (along with tonearm ground) BUT being a Hagerman Trumpet, it takes DC from a SMPS wall wart that's 2 prongs. So there's no connection to earth ground. So I guess that's kind of a bummer if the intention of this bearing ground is to earth it? Any ideas what else I can do with this ground wire, or whether it might actually help at all? The Herron has a linear PSU with 3-prong cord, but quite frankly the Hagerman is the better sonic match here so I want to use that. 

Any ideas if clamp and mat can affect the static issue? I have a Synergistic Research UEF mat I can retrieve from the loft. When I've had the POP issue I'd been using the bare delrin platter with a Stillpoints LPI weight that fits loosely over the spindle. I've started using a Clearaudio Twister clamp that gives a tight grip on the spindle and should be conductively connected to the metal tightening knob. 

I've put it on the phono stage for now (along with tonearm ground) BUT being a Hagerman Trumpet, it takes DC from a SMPS wall wart that's 2 prongs. So there's no connection to earth ground. So I guess that's kind of a bummer if the intention of this bearing ground is to earth it? Any ideas what else I can do with this ground wire, or whether it might actually help at all? The Herron has a linear PSU with 3-prong cord, but quite frankly the Hagerman is the better sonic match here so I want to use that. 

Its OK that the phono section isn't grounded to the wall. What is important is that the ground of the 'table is the same as that of the phono section.

IME the platter pad can have a big effect on static. I've never used a delrin platter though.

Its OK that the phono section isn’t grounded to the wall. What is important is that the ground of the ’table is the same as that of the phono section.

IME the platter pad can have a big effect on static. I’ve never used a delrin platter though.

Thanks for the info, @atmasphere - I went ahead and connected it that way.

So certainly, this case appears to be a complex problem with a lot of variables. I got the Hudson Hifi arm brush for static dissipation - easy to use, and a nice product for cheap. I’ve been very careful to eliminate any sources of static - and yet the problem still persists (on average once every several records or so). So I think we can eliminate static discharge itself being the primary factor. The common point here is the preamp (as Ralph surmised earlier).

So I dug up my Rogue Athena preamp and subbed it in. This is a more traditional design with analog attenuator up front (motorized stepped attenuator), and it also uses Jensen line transformers for I/O conversions (SE to balanced). I swear the surface noise & pops/ticks seem a bit quieter, and no "mega POP" has occurred yet. If this holds, then perhaps it points to the Ref 6’s digital attenuation not fully blocking the circuitry from overload conditions in all cases (I’m no circuits engineer, just stretching here)? I didn’t face the issue with this same Ref preamp in my main rig - but yeah there are a lot of variables at play - for one, the main rig speakers are 6dB more efficient. Thinking back I’ve certainly noticed that the Ref preamps in general (I’ve had two now) do seem to "enhance" the record surface noise a bit versus traditional attenuator-based designs like VAC. Other than that, they sound absolutely specular with vinyl...but I just can’t keep subjecting my tweeters to this when Tannoy doesn’t supply the parts anymore...catch 22 :-/

** Again thinking back a few years, I remember a humble little system I put together with NAD C368 integrated used as the preamp (digital volume control) that also faced the mega POPs issue with vinyl. Is this a general issue of using digital volume controls with vinyl for loud playback?

So I’ll enjoy the Athena preamp for a while, hopefully get used to its sound (some pros, some cons versus the Ref 6), hopefully not experience a mega-POP again, and report back :)

Thinking back I’ve certainly noticed that the Ref preamps in general (I’ve had two now) do seem to "enhance" the record surface noise a bit versus traditional attenuator-based designs like VAC.

@mulveling 

If the preamp seems to enhance surface noise, the volume control likely has nothing to do with it. This problem is usually caused by high frequency (in the case of LOMC cartridge, Radio Frequency energy) overloading the input of the phono section.

Sounds for all the world like a noisy LP surface. But swap in a different phono section and its gone or noticeably reduced.

I've written about this a lot in the context of 'cartridge loading'.

Its one thing to read about it though; quite another when you encounter it.

Welp I’m now 100% certain this case has a very simple explanation: power amp clipping. The 2 amps I’d been using were very similar in power: 100 Watts/ch tubes and 120 Watts / ch SS. Swapping in the 250 Watts/ch Rogue Apollo Dark, and it sails through everything. IIRC the Rogue also has much more dynamic/transient power reserves than usual (Rogue has previously mentioned 800 - 900 Watts?!), which applies here

I’d started to notice the issue was happening on certain spots of certain tracks. And yes, it was related to volume - it would always play clean at lower volumes. I just didn’t expect amp clipping to manifest a singular POP at so much of a higher level than any music the tweeter was playing. No grungy, hazy distortion or harshness or any other warning signs - just a hugely loud single POP occurring within otherwise perfectly CLEAN music playback.

So my educated guess is there’s an awful lot of subsonic low frequency energy getting into the system, even with good rack & isolation platform. From record warps (etc) and feedback. Yes, the tonearm & cartridge compliance is in "good" range. Unfortunately it’s a small room with a very bouncy suspended floor. So I suspect a huge LF waveform (that I can’t even fully hear) pushes the amp too hard, and boom - now it’s a clipped waveform with both a LF and HF component (the not-so-neat part of clipping a LF waveform). The HF component is very transient, but at a much higher level than all combined HF content from the actual music (because energy content in actual music decreases as you raise frequency), and of course it sounds just awful (edge of a square wave). It really did sound like a mega-loud singular surface POP. Weird that it usually seemed to come from the right side, even once when I had the MONO switch engaged (can’t figure that out). Tannoy’s tweeter is tough, thankfully - all OK there.

Anyways I think it’s best to have more power on tap to keep the LF crap from clipping and splitting into LF & HF crap. Long term I need to experiment with rack position and isolation tweaks to reduce feedback. Maybe even bass traps etc. Yes I’ll keep a lid on the volume, too. I know I play loud, but it really shouldn’t be clipping at these levels for just music without the (suspected) LF crap going on.

Many thanks everyone for your contributions, it helped me think through all possibilities :) The system sounds phenomenal now, btw. Very happy and glad to have an answer.

I went through all possible avenues, and the following definitely had zero effect:

• Anti-static measures
• Audioquest Niagara 3000 power conditioner
• Different cartridges (tried Benz Wood, Ortofon A90, Shelter Harmony)
• Different preamps

What’s interesting is I never reproduced the issue when using my VAC phono stage with EAR SUT (both borrowed from main rig). But the problem occurred with both Hagerman Trumpet MC and Herron VTPH-2A. My guess is the VAC + SUT simply filters out more of that LF energy. The Herron and Hagerman both use a JFET MC stage.