OK here's the calculation.
Looking at the input transistor. The input impedance of that transistor is given by its gain, which will be around 200, multiplied by the unbypassed emitter resistor of 22k. So the transistor itself will have an input impedance of 4.4M-ohms. Very high indeed.
The only other resistor contributing is R411, 100k. For AC that is connected to ground via C111 (47u) (or a cut at 0.035Hz). So the combined input impedance is at all audio frequencies is 100k.
The -3dB frequency as a result of the 2.2u input capacitor and 100k input impedance is 0.72Hz. The -1dB frequency is twice that, or 1.4Hz. All way beyond audible frequencies. A bass guitar goes down to 44 Hz and the largest organs go down to 16Hz.
The load resistor R401 looks on the face of it high at 82k. But that is in parallel with R411 100k - giving 45k. In other words within 4% of the usual 47k load.
So whoever designed this phono stage actually did his or her sums.
The schematic in the original post does not show what is connected downstream of C415/C416, or even (if I have not missed it) the manufacturer and type number of this preamp.
Looking at the input transistor. The input impedance of that transistor is given by its gain, which will be around 200, multiplied by the unbypassed emitter resistor of 22k. So the transistor itself will have an input impedance of 4.4M-ohms. Very high indeed.
The only other resistor contributing is R411, 100k. For AC that is connected to ground via C111 (47u) (or a cut at 0.035Hz). So the combined input impedance is at all audio frequencies is 100k.
The -3dB frequency as a result of the 2.2u input capacitor and 100k input impedance is 0.72Hz. The -1dB frequency is twice that, or 1.4Hz. All way beyond audible frequencies. A bass guitar goes down to 44 Hz and the largest organs go down to 16Hz.
The load resistor R401 looks on the face of it high at 82k. But that is in parallel with R411 100k - giving 45k. In other words within 4% of the usual 47k load.
So whoever designed this phono stage actually did his or her sums.
The schematic in the original post does not show what is connected downstream of C415/C416, or even (if I have not missed it) the manufacturer and type number of this preamp.
39Hz, 45Hz - who cares about that small difference. It is of no importance to the point I was making.
And show me a speaker that can produce a useable output down to 8Hz, let alone reproduce the diaphragm shaking physical assault of a pipe organ in full flight.
And show me a speaker that can produce a useable output down to 8Hz, let alone reproduce the diaphragm shaking physical assault of a pipe organ in full flight.
Well google is your friend. There are only two organs globally that have a 64 foot pipe to produce 8Hz. One at the Midmer-Losh organ at Boardwalk Hall Convention Center in Atlantic City, and Sydney Town Hall Australia. Also in the wikipedia entry https://en.wikipedia.org/wiki/Boardwalk_Hall_Auditorium_Organ where it says "The organ possesses a unique stop in the organ world, the 64-foot Diaphone-Dulzian in the Right Stage chamber (Pedal Right division), one of only two true 64-foot stops in the world. (The other 64-foot stop is the Contra-Trombone reed stop in the Sydney Town Hall Grand Organ."
These 64 foot 8Hz pipes weigh around 1.5 tons
So my assertion of 16Hz lowest frequency, with the exception of two organs worldwide, still stands.
These 64 foot 8Hz pipes weigh around 1.5 tons
So my assertion of 16Hz lowest frequency, with the exception of two organs worldwide, still stands.
Looking at the overall schematics that the OP posted, the load on the phono stage, assuming loudness is not engaged, the two pots, the output of which is in parallel with 470k input resistor for the tone control amp, in parallel with the 220 k resistor at the output of the phono stage.
Assuming balance control centred, and volume control half way. so the bottom half of the volume control is in parallel with 470k. So 125k//470k = 100k. That is connected from the middle of the balance control, 250k. 250k//100k ~70k. Add that to the upper half of the balance control to get 250+70k = 320k. That is in parallel with the 220k on the output of the phono stage of 220//320k = 130k. The 0.47u output capacitor on the phono stage with therefore give a low frequency -3dB frequency of 2.6Hz, or a -1dB frequency of 5.2Hz.
There is nothing to be gained by increasing the value of the 0.47u output capacitor on the phono stage. The only thing that might be worthwhile is changing it for the same value in polypropylene, something compact, like a Wima MKP2 in either 100V or 250V with 5mm pin spacing. From Mouser and other suppliers.
Don't fiddle around too much, because the circuit board will be single sided, and getting traces to lift off is very easy to do. Needs soldering skills to prevent an unholy mess.
Assuming balance control centred, and volume control half way. so the bottom half of the volume control is in parallel with 470k. So 125k//470k = 100k. That is connected from the middle of the balance control, 250k. 250k//100k ~70k. Add that to the upper half of the balance control to get 250+70k = 320k. That is in parallel with the 220k on the output of the phono stage of 220//320k = 130k. The 0.47u output capacitor on the phono stage with therefore give a low frequency -3dB frequency of 2.6Hz, or a -1dB frequency of 5.2Hz.
There is nothing to be gained by increasing the value of the 0.47u output capacitor on the phono stage. The only thing that might be worthwhile is changing it for the same value in polypropylene, something compact, like a Wima MKP2 in either 100V or 250V with 5mm pin spacing. From Mouser and other suppliers.
Don't fiddle around too much, because the circuit board will be single sided, and getting traces to lift off is very easy to do. Needs soldering skills to prevent an unholy mess.
There are many more that produce it synthetically. One is right here in Melbourne, Australlia.
For some reason the Quote feature does not appear in the above post
Anyhow - please educate us. What do you mean when you say that (pipe?) organs generate 8 Hz synthetically?
Anyhow - please educate us. What do you mean when you say that (pipe?) organs generate 8 Hz synthetically?
It’s a well-known practice in organ building. You provide a 32’ and a 21-1/3’ pipe, which produces the G above the 32’ C for example, and they intermodulate to produce a 64’ C an octave lower. It’s done all the time to produce a synthetic 32’ from an organ that doesn’t have pipes longer than 16’.
it should also be noted that you can produce 8Hz from a 32’ closed pipe, or a reed pipe of various lengths.
it should also be noted that you can produce 8Hz from a 32’ closed pipe, or a reed pipe of various lengths.
All this talk of low notes and organs makes me wonder if stained glass windows are affected by the infrasound these mamoth machines make?
I have an organ LP which has 3 'test tracks' as a filler: 8Hz (64' pipe), 12Hz & 16Hz (32' pipe).
The 16Hz is first - then it segues into the 12Hz ... and then the 8Hz. When the 16Hz track is playing ... I can actually hear something from the subs. 😵 But when the 12Hz & 8Hz tracks go on ... I can see the cantilever wiggling violently from side to side - but no sound comes from the spkrs!
You should check the line level (phono out, line in) signal at that mode - is anything being passed or is the content filtered out on the way.
Even a soundcard scope could do that.
Violent wiggling I would suspect to be mechanical resonance (and dangerous as such if the stylus is not following the groove).
I could do that (as I have a scope) - but I strongly suspect that my phono stage is not up to passing 8Hz ... or 12Hz. 🙁
I see it more as what happens, the lower you go in frequency. Normal LPs do not have much below 16Hz - maybe even 20Hz - recorded in the grooves.
I would be a bit more optimistic - I have not seen that many rumble filters in phono stages (at least older ones) - these are usually applied in a preamplifier module. What phono amplifier do you use?
It would be interesting to see all these signals - 4, 8 and 16 Hz.
The phono stage I am using atm is a Hagerman "Euphonia" (one of Jim's prototypes, to get used to using press-button input selection - it allows for 2 pairs of phono cables - gain and loading, which he later used in his top phono stage).
No, it doesn't have a rumble filter but - from my experiments with my own 'Muse' phono stage - RIAA equalisation causes a roll-off at frequencies lower than 20Hz.
I presume you mean 8, 12 and 16Hz? 🙂
There is the odd exception. The (in)famous Telarc 1812, where the cannon shots can throw cartridges clean out of the groove. I don't know the spectrum of those shots, and it may be that it is simply extreme amplitude.