Oh yeah! You definitely know your stuff! 
And it had to be a special green marker. Which cost a lot of course.
Coming full circle, there were those who painted the interior of CD players with a certain green Pactra paint to obtain the same outcome, I guess.
New thing is shaving CDs.
I tried the below with green and blue LEDs, but I didn’t hear any difference.
Cool.
I did Technical Tape Mastering for Philips/PolyGram later Universal Music Group at a compact disc/DVD facility. If one’s “ears” had the ability to hear the difference in digital recordings both of our main studios were more than capable demonstrating the sonic ability.
The idea that “LP’s” are the pinnacle of “sonic fidelity” is laughable in my experience in a high quality studio listening environment IF the digital source was correctly mastered.
LP’s are cool, I like them and still own a lot of vinyl.
What made any media format shine was a master audio engineer. We had the pleasure of working with several of the finest.
Rare top notch audio engineers at the pinnacle of their game could work magic for any format.
It’s always about the guy running the board. Their ear and mixing abilities may not be the greatest.
I find there is sometimes too much compression or the mids are too scooped in CD’s which muddies the overall sound. I am by no means an audiophile however I do appreciate analog a bit more than digital. I can’t stand the audio of Beats headphones they enhance the sound too much which to me is not what was recorded. I prefer and use Audio-Technica ATH-M50x as I find them quite neutral, great for tracking when I’m play guitar.
As for vinyl, a heavy needle puts a deep groove which you loose some of the harmonics. @M70 have you experimented with other pre-amp tubes in the 12xx7 line-up? I know mixing them up in guitar amps they can make quite a difference in the tone and gain stage in break up.
The 12AU7 preamp is specific to that type, though I have used 5814s some, which are basically the same.
Different brands sound different of course and I do like the old RCA clear tops.
Another preamp has Directly Heated 2J27S tubes, a Soviet tube. I am liking this.
I use Mullard 12AX7s in my old Marshalls. Sublime!
Of course, no amount of tweaking will fix brickwalled poorly (re)mastered CDs. Very frustrating. One time, got a new CD of a favorite band and played it on the way to the supermarket.
While listening, I thought, sonuva, sounds like [redacted] got his mitts on this. Get to the parking lot, look at the booklet, yep, exactly who I thought remastered it. What is wrong with him??? Ruined it. No one should be able to discern who remastered a CD by how crappy it sounds.
Another example: remaster of first Van Halen. HORRIBLE.
Of course!
Wouldn’t be a profitable business otherwise.
Remember that famous quote attributed to P. T. Barnum about one being born every minute …
I would like to get some Mullards for a Blues Junior (BillM mods) I have. I need to warm up the mids. I run it as a head through two cabs; 1x12 with a Jensen, 2x12 with Celestions. It’s not my go to amp however I would like to get it somewhere more usable.
I tried that once. Didn’t hear any difference.
Obviously. 
The digital ones and zeros are distinguished by the time differences for when the reflected laser light comes back to the receiver. Nobody cares if 10% or 20% of the light goes off somewhere else.
Scratches on the surface of the disc though, that’s big trouble …
That stupidity must have been dreamed up by someone who didn’t know anything at all about digital technology, error correction algorithms, fault resilient codes et.c.
Same difference with analog vs digital radio.
If you own a modern mobile phone you carry a device which can reconstruct a signal from something that is essentially background noise
Speaking of CD’s, the whole green 
magic marker on the edge of the CD makes them sound better is hilarious 
.
However, if the bottom (unprinted side) of the CD has a scratch in the polycarbonate, a tiny bit of oil to just fill the scratch in some cases can allow the laser to focus again. This is just a band aid of course but in some cases it proved effective enough to eliminate otherwise uncorrectable, E32, massive C2 errors to allow playing the music or transferring data.
Sound like most of the work calls I have - all “background noise”…
olive oil usually has a slight greenish tint …
just saying …
Yes, but Popeye won’t take kindly to you spreading her on your CDs… 
Wow, you guys are smarter than me . . . what was the question?
Cajun 
I think the idea about green markers was also to prevent ambient white light from getting into the polycarbonate.
Again, nothing happened, positive or negative.
Regarding blue or green LEDs on the transport mechanism shining on the CD, I did find this comment interesting:
“I spoke to one of our optical engineers about the physics of this issue. We make very sensitive laser equipment that measures protiens through diffraction. Anyway he stipulated that there may be some benefit of flooding the CD surface with a green or blue incoherent light to improve the performance of the laser pickup. The benefit he stipulated was the reduction or elimination of white light reflections which are significantly noisier than the green or blue light off of a good source. The discriminator circuit can filter the green or blue light much easier than white light.
“The net result maybe a lower noise floor from a technical perspective, how an Audio Fanatic may describe the effect is totally subjective of course.”
So I removed the lid on a CD player, turned off the lights in the garage and tried both blue and then green LEDs in various directions.
Big surprise, I know: not a dang thing.
I thought it would be fun and easy to try. And occasionally, I have run across something that shouldn’t work but does.
On the flip side, you have those who breezily pontificate that different opamps cannot possibly sound different.
Like the guitar pedal guru who via a video with no small amount of fairly intense peer pressure plus a guitarist just bashing an open G chord with different opamps installed “proves” opamps all sound the same.
Of course they can.
The inner physical characteristics of the silicon (or geranium or something else) based circuits have different impacts on the amplified signal. Since there are several components inside (transistors and resistors) there are many sets of characteristics to fine tune or make a mess of.
The inner workings.
Then there can be external circuits to achieve a desired behaviour.
Plenty of opportunities for real physics to influence the behaviour.
Vacuum tubes also have their own quirks and behaviours (they also look cool poking up through the top of an amplifier).
Refinery/Factory where sound is amplified:
In a CD-reader there is just the speed of light which doesn’t change much and the depth of the little divots. Very little chance for variation.
The CD-unit behind the “pickup” can have any number of non-desirable behaviours but those are the same regardless of what an audiophile with an overpriced Sharpie tries to do. Transmission of analog signals can be degraded due to contact resistance in cheap/bad plugs et.c. Disturbances can be picked up by unshielded cables et.c.
Edit:
The suspense is intense.
What will Wade write in his post?
I just like a good fuzz with a treble booster 
Those tubes look pretty. Are those CD laser LED’s illuminating the tubes?
I know… [sigh] We know… I met the guru twice and foolishly broached the topic. He immediately interjected, “Have you seen my video?! I PROVE all opamps sound the same!” etc., etc.
I just let stuff like that go. There’s no point in arguing. I know darn well that different opamps sound different.
Haven’t got the foggiest, I simply googled for vacuum tube amplifier and picked the prettiest photo
MacIntosh 240 (whatever that means to those who know about these things)
It seems that this guy knows about it: https://www.kenrockwell.com/audio/mcintosh/mc240.htm
It cost $288 back in 1960 so it is older than the CD-technology and older than I am so it has been around.
Still looks gorgeous though …
I’m really liking the Movall Absolute Zero Fuzz.
I also have a Keeley Java Boost in purple. I believe that’s the only one he built in that color.
I started a Hornby-Skewes treble booster clone ala Blackmore a while back. Need to get back on that.
