Microphonics in VF14 and U47

[k brown]

I wonder if people were actually aware that masters for LPs are way different.

Indeed.

 

[Tubetec]

On some tube amps you see the sprung metal tube retainers , guess what, when your tubes get old and tired they pick up the vibration of the springs and it can give the tone a hint of reverb/decay on the peaks.

 

[Whoops]

I was always puzzled by how little attention there used to be to the sound of tremolo bar springs in strat style guitars.

My first guitar was a Fender Strat, I remember taking off the plastic plate that covered the tremolo bar springs because I preferred the sound that way. I think Hendrix and other Strat musicians also did that, so I guess more people were sensitive to it. I remember that it was a well known thing (I was a kid in the 90s) and there were discussions about it, so I'm not sure it got little attention, personally it was obvious to me and I always felt it was obvious to other people. but maybe I'm wrong.

 

[Whoops]

The theory was put forth by audiophiles and audiophile magazine editors, not by record labels - and was way before the CD era. Folks were theorizing about why in many cases LPs sounded better than the same releases on R2R tape (despite the surface noise).

Vinyl was dead by the mid 90s, with audiophiles theories or not, no one cared about it for 25 years, maybe longer. That didn't wake up Vinyl from the dead.
I was talking about the new found hype surrounding Vinyl that started somewhere around 15 years ago, hype that made Vinyl production start again, it was not done by audiophiles and audiophile magazine editors, it was done by commercial record labels as a way of still selling some records when CD sales went down the drain. There's also some nostalgia effect here from the consumers part.

I'm a Mastering Engineer, and Kingkorg is totally correct, mastering for Vinyl and CD releases or Digital Streaming is not the same. The divergence among Audiophiles has to do with the Over Limiting used in some CD releases, and it actually got to a point it was over the top, extremely limited and squashed... Loudness Wars.... The source material for Vinyl can't be as limited as it would not cut well.
But saying this Mastering for Vinyl has also a lot of drawbacks and shortcomings, there's much more information in the Digital mixes I receive, and that we can hear, than what's possible to cut on a Vinyl, so to do the Pre-Mastering for a Vinyl cut you have to actually degrade the original sound quality like limit Low end extension and high end extension for example and also change some artistic decisions in the mix like the need to have the low end in mono for a Vinyl cut.
So overall, taking the amount of limiting out of the equation, the Vinyl pre-masters (send to the Cut) are always smaller (smaller frequency response) and degraded compared to the Digital Mixes I receive, the mixes that were approved by the artists, producers and labels ARs.

Off course a normal consumer don't know anything about this, and from the people I know that on the top of their minds say that "Vinyl sound better" none of them actually did an A/B comparison (a proper one) between the CD or high quality streaming and the Vinyl release. But I did and do it all the time, and the Vinyl is always much worse.

My 2 cents

 

[Tubetec]

I believe Angus Young kept an amp he recorded a few of the earlier records on untouched for decades , never changed the tubes never tried to fix it , just used it the odd time in studio .

 

[Tubetec]

I added an extra high gain stage to one hifi amp I converted for guitar , I placed it in its own aluminium box with about 6 inches of cable from the main chassis, jack in/out
I mounted up the tube sub assembly with an antivibration mechanism , it made a big difference , not only are you away from the chassis and its spurious currents and funky vibrations , it ensured great clarity when the amp was driven full throttle with very much reduced interaction from the speaker.

A few times in the repair shop guys have brought me in amps , they tell me every thing is fine until they hit a certain note at volume , then all hell breaks loose,
9/10 times I'd find a red label Shuguang 12AX7 was the issue .
theres a really unpleasent mechanical vibration that conicides with the note where it occurs , again tapping the tube in circuit or out reveals the trouble.

The other thing is ,say a customer brings me some tubes he's ordered and wants me to install ,
I want to put the best performing (microphonically and noise)12ax7 up front and in decending order towards the PI ,
No way of knowing the electrical noise of the tube until its energised , but you can evaluate the likely peformance with regards vibration easily without an FFT .

 

[Gus]

I was always puzzled by how little attention there used to be to the sound of tremolo bar springs in strat style guitars. People were ranting about some very questionable aspects of guitar sound for decades. I can hardly remember anyone mentioning super obvious "built in spring reverb" in these. Nowdays people seem more aware of it, probably because of the obsession with gating, and overproducing guitars.

IIRC I have memory of a Ry Cooder article I read about the reverb effect from the strat springs. I don't remember if I read it in a magazine or on the web it was some time ago.

 

[Tubetec]

I think the right word for what microphony in tubes or any audio equipment subject to vibration does is 'smudge' the attack on the peaks ,
It happens just as well in the control room if your blasting your monitors at 25,000 lytics in a metal box

 

[Tubetec]

How about as an experiment , open all the channels on your prize possession to the master bus , max out the input gain on each channel , and set the faders to 0 . Set the monitors as loud as they go sweep up from 10hz , inspect console spectra in REW from a remote location

The bigger more powerful the monitors and the more super complex the mixer the worse the effect , its measurable !

 

[Tubetec]

Once I saw the getter ring at the top of an EL34 had broken away on one side the screen grid was litteraly flapping , it caused a horrendous din when excited by any vibration.
other times Ive seen tubes with RT60 times in the region of a second until the electrodes stop droning .

 

[vitopower]

Has anyone opened a VF14 and can share pictures ?

There is a pic from the facebook user "Neumann U47", posted on September 8th 2017.
Bottom left in this pic claims to be the inside of a VF14.

 

[Tubetec]

Seems to be an issue with the link , a screen grab would be sufficient.

 

[gyraf]

here's what I've found over the years..

 

[rock soderstrom]

here's what I've found over the years..

How do you open German steel tubes so that you get them back together nicely? Are they glued or just clamped by these small notches?

 

[Tubetec]

If you desolder the pins and pull out the notches the metal part should lift away from the base .

 

[rock soderstrom]

If you desolder the pins and pull out the notches the metal part should lift away from the base .

How do you do that? From the outside, all at once?

 

[Tubetec]

Id try clamping the tube gently in a vise , push out the metal tabs all around ,
Go round with the solderig iron and vaccum desolder pump , one by one,do the pins ,
once you have most of the solder off go round each pin again with the iron ,pull the base up a small bit each time , repeat as required until its off.

Maybe place the tube horizntal so the solder doesnt flow down inside the pin and make the job harder for yourself .

 

[Tubetec]

Cutting out the tube and leaving the external metal part intact looks like a bit of a challenge ,
Covering the outside in masking tape before you start work might be a good plan , prevent any marks or scratches to the painted metal .

 

[rock soderstrom]

Cutting out the tube and leaving the external metal part intact looks like a bit of a challenge ,
Covering the outside in masking tape before you start work might be a good plan , prevent any marks or scratches to the painted metal .

Thanks for your feedback. I tried it once 2 years ago, completely without a plan. It ended in a disaster for the tube. I will try it again when the time comes.

 

[tomas.borgstrom]

@tomas.borgstrom , do you have a rough SPL figure of the level you tested this at? If you have a spl meter maybe you can give me spl at 1k? Also distance?

I have a mic with EF14, i'd like to replicate the test.

Sorry, I forgot to reply. The microphone is 24cm from the speaker 108dB at 1k.