I agree that the cart response is only part of it, but its a part that causes a lot of people a lot of problems. Partially I think because almost no phono stage sellers actually publish the input capacitance of their offerings. A tube MM stage could have 500pF input C. I see a lot of threads on other forums of people complaining that X cart is bright and usually its down to too much capacitance somewhere. So my goal for the cart-pre interface is to get it as flat as possible to above the audio band. Tone controls can be handled elsewhere.
But we then get back to how can I tell if I have succeeded without a totally trustworthy test record.
But we then get back to how can I tell if I have succeeded without a totally trustworthy test record.
The best way to go in case of an MM is to make the transfer independent of the cable and amp input capacitance.
This can be done by implementing the 75usec with a proper termination resistor and leave this time constant from the Riaa correction network.
Lcart/(Rcart+Rtermination) should be 75usec.
By using a small pot for Rtermination it will be easy to do some fine tuning in the high end of the FR.
One drawback is that if you change Carts frequently, that each time the optimal Rtermination has to be selected.
The other effect is that noise will be increased, but in most cases this won’t be a problem.
If really needed, this loss in SNR can be cancelled with a special additional circuit.
Hans
This can be done by implementing the 75usec with a proper termination resistor and leave this time constant from the Riaa correction network.
Lcart/(Rcart+Rtermination) should be 75usec.
By using a small pot for Rtermination it will be easy to do some fine tuning in the high end of the FR.
One drawback is that if you change Carts frequently, that each time the optimal Rtermination has to be selected.
The other effect is that noise will be increased, but in most cases this won’t be a problem.
If really needed, this loss in SNR can be cancelled with a special additional circuit.
Hans
I have been using the cartridge's inductance and resistance plus load to form the 75 uS attenuation.
Using a choke for the low frequencies did not work. It would look good in LTSpice but it was all wrong. Would not bring the low frequencies up to where they should be.
I gave up on that. Since I am using a Xilica XP for crossover and room and speaker correction and the fact it has a "global" set of filters in addition to the individual channels I am using this to get the low frequencies right using extremely low Q shelving filters.
To get it to sound right the filters are pretty close to what you would expect.
Since I am running everything through this thing I figure it cannot be any worse than having a choke in the circuit. In fact it sounds very good.
At the moment using a cascade of OP637 and OP627 for gain. Maybe I did not have enough gain in the first stage for the choke to work? I do not know - 26 db in the first stage and 23 db for the second stage. Both op amps in inverting mode.
Had two stages since there used to be a choke in between them - with the choke I did use more gain on the second stage - still did not correct correctly.
I am dealing with noise but I do not think it has anything to do with the concept.
What is strange is when I was not using the Xilica and ran the phono with the choke into a Pass buffer the EQ sounded better. I would not think the input impedance difference between the Xilica and the Pass Buffer, which is considerable (10k v 220K) would account for this mystery.
My memory tells me the Xilica approach is superior to the high gain choke version into the Pass buffer. Much superior but i hesitate to say much more than that.
Has anyone noticed a bump in the region of 28 hz using the cartridge itself as part of the corrector? No matter what I do it is there. With the Xilica I can remove most of it without harming the rest of the range. I feel sure it is not my turntable. I guess I need to get one of the inexpensive AT MMs and see if it happens there. I am using the Clearaudio Charisma and I like it. Had a fancy MC which died and unfortunately so did the manufacturer, Transfiguration. So I thought I would try something different.
The idea was brought to my attention by Mr. Cordell's phono article though he did not "go all of the way" with the concept. I am attracted to the simplicity of the idea though i realize no one would think using PEQ is simplicity.
I am hoping the old saw "simple as can be but no simpler" applies.
Glad to see others giving this a try.
Using a choke for the low frequencies did not work. It would look good in LTSpice but it was all wrong. Would not bring the low frequencies up to where they should be.
I gave up on that. Since I am using a Xilica XP for crossover and room and speaker correction and the fact it has a "global" set of filters in addition to the individual channels I am using this to get the low frequencies right using extremely low Q shelving filters.
To get it to sound right the filters are pretty close to what you would expect.
Since I am running everything through this thing I figure it cannot be any worse than having a choke in the circuit. In fact it sounds very good.
At the moment using a cascade of OP637 and OP627 for gain. Maybe I did not have enough gain in the first stage for the choke to work? I do not know - 26 db in the first stage and 23 db for the second stage. Both op amps in inverting mode.
Had two stages since there used to be a choke in between them - with the choke I did use more gain on the second stage - still did not correct correctly.
I am dealing with noise but I do not think it has anything to do with the concept.
What is strange is when I was not using the Xilica and ran the phono with the choke into a Pass buffer the EQ sounded better. I would not think the input impedance difference between the Xilica and the Pass Buffer, which is considerable (10k v 220K) would account for this mystery.
My memory tells me the Xilica approach is superior to the high gain choke version into the Pass buffer. Much superior but i hesitate to say much more than that.
Has anyone noticed a bump in the region of 28 hz using the cartridge itself as part of the corrector? No matter what I do it is there. With the Xilica I can remove most of it without harming the rest of the range. I feel sure it is not my turntable. I guess I need to get one of the inexpensive AT MMs and see if it happens there. I am using the Clearaudio Charisma and I like it. Had a fancy MC which died and unfortunately so did the manufacturer, Transfiguration. So I thought I would try something different.
The idea was brought to my attention by Mr. Cordell's phono article though he did not "go all of the way" with the concept. I am attracted to the simplicity of the idea though i realize no one would think using PEQ is simplicity.
I am hoping the old saw "simple as can be but no simpler" applies.
Glad to see others giving this a try.
I need some help with testing Paradise phono stage,
I have available SB X-Fi soundcard and Daquarta software, software is quite good with frequency sweep , white and pink noise .
I tried connecting input of the phonostage to speakers output and adjusting output to 0.7mV , software applies reverse RIAA than signal from phono output taken to line in of SB card.
Trouble is response I get is far from flat , would I be better using higher voltage input with attenuator , what value should I use ?
I have available SB X-Fi soundcard and Daquarta software, software is quite good with frequency sweep , white and pink noise .
I tried connecting input of the phonostage to speakers output and adjusting output to 0.7mV , software applies reverse RIAA than signal from phono output taken to line in of SB card.
Trouble is response I get is far from flat , would I be better using higher voltage input with attenuator , what value should I use ?
Could you show what FR you get, that makes it a bit easier to answer your question.
And yes, 0.7 mV is a bit low but should work when clean. Start with generating a much larger signal like 1Volt and attenuate it with two resistors to ca 5mV@1kHz.
Hans
Paradise is a MC stage , I assume I need bit lower voltage @1kHz am I correct?
How to work out resistors values? I’m not greatest at electronics so forgive a silly question, I take I need to connect 2 resistors between signal and ground and then I take voltage from one of them?
I will take some pics this weekend but it’s mainly low frequencies below 100-150 Hz where I get a rise in response
Thank you
How to work out resistors values? I’m not greatest at electronics so forgive a silly question, I take I need to connect 2 resistors between signal and ground and then I take voltage from one of them?
I will take some pics this weekend but it’s mainly low frequencies below 100-150 Hz where I get a rise in response
Thank you
O.k. In case of an MC amp, the 0.7mV was appropriate.
When starting with a 1 Volt signal, use for instance a 20k / 10 Ohm divider and connect the MC input to the 10 Ohm.
Hans
Parenthetical:
Luke Ellis, CEO of Man Group (one of the largest trading firms in the world), was interviewed by Bloomberg's Barry Ritholtz. At the end of the interview he was asked what advice he would give a young person graduating from college. Ellis' response: "Learn Python"
Luke Ellis, CEO of Man Group (one of the largest trading firms in the world), was interviewed by Bloomberg's Barry Ritholtz. At the end of the interview he was asked what advice he would give a young person graduating from college. Ellis' response: "Learn Python"
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