Jan, I believe the exact phrase is: Put the pedal to the metal, meaning driver as fast as you can.
You can catch the pharse in for example Sam Peckinpah's movie "Convoy", or the movie "Smokey and the bandit", with Burt Reynolds, Jerry Reed, J, Gleeson, Burt Young, et al.
So you can see who our Richard identifies with.
I never expected just one spec to describe trafos in total, Richard, just wondered. AS for shieldong, I tend to shield them anyway. Might not have any gains, but I shure won't have any losses either.
That Brad is a quote of George Bernard Shaw, who so responded to a poor review of one his works in London's Times.
Britain's history is full of wonderfully witty responses. During WW2, a lord from the House of Lords, by the name of Lord Railing, in one of his frequent arguments with Sir Windston Churchill, exclaimed: "Sir Winston, you're a dog!", to which Sir Winston replied: "Lord Railing, you know what dogs do to railings."
Yep - the change in pitch is limited to the tuning of the individual instrument as the assumptions used at the time of initial tuning may have changed. But this effect is only really observable or apparent when you get into large swings in temperature, say going from 18 or 19c to 5c, where it goes "flat" and has nothing to do with the transmission of the sound once the change is accounted for by the individual player... so it was OT for the most part.
Richard
I have measured various RIAA preamps. At 10Hz, response varies from +2dB to –20dB rel RIAA curve.
I mention the 10Hz as to comply to your second question.
The strongest subsonic electrical signal at the cartridge output is at the frequency of arm/cartridge resonance, usually around 10Hz.
How strong this signal is, depends on:
1. The amplitude of excitation signal, i.e. vinyl record condition
2. The degree of arm/cart resonance dumping. The resonance can achieve an 12-20dB signal amplification at the region of resonance peak
For a vinyl record in good condition, a 1mV per 1cm/s MM cartridge and a moderately dumped arm/cart installation, expect 3mVrms from the cart at around 10Hz . (I can provide data for these numbers if you are interested but the post will be lengthy).
For your second question.
A case as described in the previous paragraph and a RIAA preamp (33dB/1kHz) with a moderate LF roll-off achieving -8dB at 10Hz, as in the attachment (it has three caps affecting the LF roll-off, C1, C8, C9)
10Hz voltage across the input coupling electrolytic cap (C1): <3mVpp
10Hz across the shunt electrolytic cap at the feedback circuit (C9): 110mVpp
10Hz across the output coupling electrolytic cap (C8): 2.5Vpp
When the RIAA preamp embodies steeper LF roll off, the AC will increase across some caps and decrease across some others, depending on the circuit and the LF filter implementation.
In any case, I don’t think that this range of AC signals across the caps will cause distortion.
I find far more important to reduce the likelihood of overloading.
Many RIAA preamps have very small (or nonexistent) overload margins at subsonic frequencies
George
Attachments
Agree, George I have modified an MAudio 0204 USB for DC coupling (non-audio use) and I was trying it to capture phono. I got about 20 min before somehow it froze my machine (Win 7). I will continue my experiments when I sort it out, but I think taking minimal gain up front and digital filters would be best. The trick of running IIR filters backwards and forwards (net linear phase) looks interesting.
On what? On the cap distortion due to AC across it or on LF overloading?
If the problem does not appear when you reduce the recording resolution (or happens at a longer recording length), most probably it’s the buffer size that your program is using.
Keep us informed Scott, but I don't understand this backward-forward trick.
We have read that digital RIAA filter has to be implemented through IIR filter for to preserve the phase behaviour of the (complementary) analog filters used in the master's cutting process, no?
George
Guessing is not allowed as fact. Distortion across the cap could be significant - esp 2.5v p-p. However, the 1972 IEC standard is to cut at 20Hz...... making the situation worse than your example.
Overloading at low freqs is easy to obtain with less than SOTA turn tables and phono stages using non-perfect records (warp, rumble, flutter, wow etc)......
It is what most of us have that is a problem -- we dont have those massive TT and super arms etc. But, I agree the over load margin at the low freq end to be of sota caliber would have to be improved over what is/was common in average gear. Or roll it off. And, I agree with JC..... if you have a clean enough TT/arm non-rolled off would sound better.
THx-RNMarsh
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That’s correct Richard.
I don’t know how high distortion can be at 2.5Vpp across the cap. Maybe you can give a number.
But it is certain that with a steeper LF roll-off upstream, the AC voltage across this cap will reduce.
1972 IEC is 4dB down at 10Hz
My example is 8dB down at 10Hz (a steeper roll-off )
From what I’ve seen so far, I can not expect anything less that 1.5Vrms at 10Hz from a 1mV per 1cm/s MM cartridge. So the successful step is to build a phono stage with an adequate OLM
“Sound better” may be attributed to some other factors as well
The only way to say if subsonic cut filters cause phase issues an octave and beyond above at acoustic frequencies, is to compare two digital filters with same slope and turn-over frequency point but the one with linear phase response. Scott?
George
Let's talk about the practical use of subsonic filters in a phono system.
I personally prefer NO rolloff in my phono preamps and there have been many successful ones. Not DC, mind you, but well below 10Hz, if possible. Usually I do it with a servo., below maybe 2Hz.
However, it is well known that 'inappropriate' phono combinations and warped records, can cause chaos at the low frequency end, and even seriously modulate your woofers. Not good! So what to do?
First, find the problem:
Is it warped records?
Is it too low of a mechanical resonance between the arm mass and the cartridge compliance? 8-12Hz is considered optimum, but many MM cartridges have too HIGH a compliance for the inexpensive tonearm used, and this resonance might go lower to 4Hz or so, and easily pick up and easily amplify the record warps from the record. This is bad, and you will never get the best performance, even if you put a serious hi pass filter into the phono.
Is it the DAMPING of the mechanical resonance? A Q of 2 is pretty optimum, for various reasons.
Sometimes, it just isn't possible, or affordable to have an optimum combination, so some sort of filter is necessary. I personally prefer a single QUALITY cap coupled at about 10Hz, that is switchable, and not used if not needed.
The 20Hz added rolloff in the 'RIAA' is something that I just ignore. It is only a band-aid for poorly engineered phono playback, and I am pretty sure that you will never get that 3dB at 20Hz back from the recording itself. I may be wrong but I suspect the disc recording electronics ignores it too.
I personally prefer NO rolloff in my phono preamps and there have been many successful ones. Not DC, mind you, but well below 10Hz, if possible. Usually I do it with a servo., below maybe 2Hz.
However, it is well known that 'inappropriate' phono combinations and warped records, can cause chaos at the low frequency end, and even seriously modulate your woofers. Not good! So what to do?
First, find the problem:
Is it warped records?
Is it too low of a mechanical resonance between the arm mass and the cartridge compliance? 8-12Hz is considered optimum, but many MM cartridges have too HIGH a compliance for the inexpensive tonearm used, and this resonance might go lower to 4Hz or so, and easily pick up and easily amplify the record warps from the record. This is bad, and you will never get the best performance, even if you put a serious hi pass filter into the phono.
Is it the DAMPING of the mechanical resonance? A Q of 2 is pretty optimum, for various reasons.
Sometimes, it just isn't possible, or affordable to have an optimum combination, so some sort of filter is necessary. I personally prefer a single QUALITY cap coupled at about 10Hz, that is switchable, and not used if not needed.
The 20Hz added rolloff in the 'RIAA' is something that I just ignore. It is only a band-aid for poorly engineered phono playback, and I am pretty sure that you will never get that 3dB at 20Hz back from the recording itself. I may be wrong but I suspect the disc recording electronics ignores it too.
Thanks for that John.
I have been listening happily to LPs through a stepup stage I did in a flash for a friend, and for which it was desirable to use up some of his 2SK170BL parts (who I doubt has used it as he never asked for details of the power supply, which in this case is fairly complex). A high-mass tonearm and an Ortofon MC15 super II and a Heybrook TT2 turntable. The odd thing is that I can't find any warped records in my collection, although I recall them as ubiquitous in the old days. The rest of the signal chain is pedestrian by comparison, an old NAD budget separate preamp, and I don't know what choices were made for low-frequency extension---certainly there is no infrasonic filter in/out switch.
I have the sense that driving the input of the NAD with a lower impedance than an MM cartridge has improved the audio quality---but this is a perilous judgment when I know that there is the stepup stage in the works.
Very possible, since some phono stages interact significantly with the source impedance. Tom Holman did some of the earliest work on this.
http://www.davidreaton.com/pdfs/holman_aes_paper.pdf
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