Well, I feel a bit like a mouse in a room full of tigers but if nobody is averse to a question from the peanut gallery . . . .how much of what is being suggested here is intended to deal directly with the OP's complaint and request, and how much has to do with other judgments of the circuit in general?
This question is entirely for my own benefit, I admit . As the OP seems open to trying things it seems like a good opportunity to learn while looking over his shoulder. If the circuit undergoes a fundamental change to something else the opportunity to learn about the cause of harshness is lost, unless of course the source is in something else, like the cartridge or even as far away as the speaker.
The OP states that he likes what he's got but for this occasional harshness at a guesstimated window of 3-5 Khz. If in general the circuit sounds good to him is it possible that something triggered by transient peaks can be the culprit?
This question is entirely for my own benefit, I admit . As the OP seems open to trying things it seems like a good opportunity to learn while looking over his shoulder. If the circuit undergoes a fundamental change to something else the opportunity to learn about the cause of harshness is lost, unless of course the source is in something else, like the cartridge or even as far away as the speaker.
The OP states that he likes what he's got but for this occasional harshness at a guesstimated window of 3-5 Khz. If in general the circuit sounds good to him is it possible that something triggered by transient peaks can be the culprit?
The main problem, sometimes, is the fact that when someone build a circuit doesn't test it with a minimum of equipment.
Now it is easy to do with a proper sound card and a sw with the accuracy to set a right chain to see what happen.
This can be a start point to understand what is happening
Now it is easy to do with a proper sound card and a sw with the accuracy to set a right chain to see what happen.
This can be a start point to understand what is happening
Agreed, We're quibbling about a circuit which is pretty good, could be tweaked. I would still check out the tone-arm, cartridge mechanical setup first.
I would also check for a microphonic tube -- either the C3g or D3a. Helpful if you have a soundcard FFT. @waltube you did some research in this area a few years back.
Article on microphonics: https://www.dalmura.com.au/static/Microphonics in valves.pdf
I would also check for a microphonic tube -- either the C3g or D3a. Helpful if you have a soundcard FFT. @waltube you did some research in this area a few years back.
Article on microphonics: https://www.dalmura.com.au/static/Microphonics in valves.pdf
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C3g, passive RIAA, C3g, D3a as CF spectrum.
I built it as demonstration -more than a decade- on breadboard, so mains harmonics are visible ... at 80-90dB lower, than carrier.
Neither tube are prone to microphonic.
C3g, C3o, C3m built as tank.
I built it as demonstration -more than a decade- on breadboard, so mains harmonics are visible ... at 80-90dB lower, than carrier.
Neither tube are prone to microphonic.
C3g, C3o, C3m built as tank.
Thank you hearing space. I am very appreciative of everyone's input and have some things to action. I have the following equipment (having gone out yesterday abd finally buying one) USB Oscillosope with tone generator I have a laptop, fluke multimeter. My problem is time but if someone could kindly list what else i need i will start measuring as soon as I can(I am not ofe with oscilloscope use in general- i have an idea but basic) The interface twixt amp and computer requires a sound card- if someone could recommend what I need i shall get one.
Once again I am very thankful to all of you and feel I am close to sorting this because it does sound good- i feel the high end is off skew as in too bright but without measurement that is guesswork.
Which inverse RIAA circuit should i buy/make?
Nick
In #52 post I recommended this:
Hagerman iRIAA
Put it in metal box (shielding).
p.s.
Up to 20kHz Hagerman is enough precise, over it alters from the ideal curve.
Hagerman iRIAA
Put it in metal box (shielding).
p.s.
Up to 20kHz Hagerman is enough precise, over it alters from the ideal curve.
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Why does he need the Hagerman? Isn't it fine to measure the raw output and see that it conforms to the RIAA curve?
Or use a computer file source etc.
Or use a computer file source etc.
Much easier to measure with inverse RIAA.
Generator (or soundcard output)->iRIAA->phono->RMS voltmeter (or soundcard input).
On the generator you set the level (phono input level 7mV as MM), measure phono output at 1kHz (this will be the "0" dB) and just roll the frequency.
This can be done manually, or with appropriate program (sweep).
The deviation from ideal curve shows itself as output discrepancy from "0" in decibel.
Generator (or soundcard output)->iRIAA->phono->RMS voltmeter (or soundcard input).
On the generator you set the level (phono input level 7mV as MM), measure phono output at 1kHz (this will be the "0" dB) and just roll the frequency.
This can be done manually, or with appropriate program (sweep).
The deviation from ideal curve shows itself as output discrepancy from "0" in decibel.
The easiest way, as long as you can measure dB, is to measure at 1kHz, call that 0dB, then 20Hz should be +19.91dB and 20kHz should be -19.91dB. If these there points are accurate, every other point must be as well.
What I suggest is to measure each one of the gain stage one at time without riaa network to see if they are linear
Taking care on Zload if you use the sound card
It is not a quick job but you can stay safe about the quality of the stages
It is my opinion
Walter
Taking care on Zload if you use the sound card
It is not a quick job but you can stay safe about the quality of the stages
It is my opinion
Walter
Just for info
The test set, with a beautiful McMurdo socket anti-vibration
Sweep 20-20kHz; using tha AP System Two + power amp and loudspkr
I took a lot of analysis, very interesting results and the use of O-ring for high temperature in the middle of the glass helps a lot.
In case I can send the results but are many images
Walter