This is way too complicated,
The polarity has ONE test,
microphone to loudspeakers.
Check phase, if wrong, switch output amp red/black.
The polarity has ONE test,
microphone to loudspeakers.
Check phase, if wrong, switch output amp red/black.
MarcelvdG
What do you think of this? I wonder if it might work if it can be modified to have different input, output impedances and input sensitivity. You have to click "see original listing" to see the details.
https://www.ebay.com/itm/154574628127?
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It will depend on whether the film capacitors with much larger values you need for the circuit of post #72 fit on the board. Chances are they don't. You could increase R4 by some large factor to get away with smaller values for the capacitors, but then you get more noise. All in all, I would just use a perfboard.
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For a simple circuit like Marcel suggested, I would just use some kind of proto board (example to illustrate, no link to the seller, or suggestion that this is the right one for you). Then you can accommodate any sized components you like. No need for a pre-built pcb.
By the way, when you change R4 to 52.65 Ω including the parallel resistance across the MC amplifier input, C1 and C2 get within 1.4 % from an E6 standard capacitor value:
R1 = 10 Ω
R4 = 52.65 Ω including the MC amplifier input resistance that is in parallel
For example, the resistor on the board has to be 69.21422 Ω, or 69.8 Ω rounded to the nearest E96 value, when the MC amplifier input resistance is 220 Ω. It has to be 111.19324 Ω, or 110 Ω rounded to the nearest E96 value, when the MC amplifier input resistance is 100 Ω.
R3 = 759.646247223 Ω -> 750 Ω rounded to an E96 value
C2 = 98.730165882 nF -> 100 nF rounded to an E6 value
R2 = 9510.7946895155 Ω -> 9530 Ω rounded to an E96 value
C1 = 334.35691799 nF -> 330 nF rounded to an E6 value
The capacitors either have to be accurate film capacitors or accurate NP0 a.k.a. C0G ceramic multilayer capacitors, definitely not ceramic class 2 or 3 capacitors (such as X7R, X5R, Y5V, Z5U). The more accurate the better, but the best you can get with these values is probably +/- 5 % tolerance.
R1 = 10 Ω
R4 = 52.65 Ω including the MC amplifier input resistance that is in parallel
For example, the resistor on the board has to be 69.21422 Ω, or 69.8 Ω rounded to the nearest E96 value, when the MC amplifier input resistance is 220 Ω. It has to be 111.19324 Ω, or 110 Ω rounded to the nearest E96 value, when the MC amplifier input resistance is 100 Ω.
R3 = 759.646247223 Ω -> 750 Ω rounded to an E96 value
C2 = 98.730165882 nF -> 100 nF rounded to an E6 value
R2 = 9510.7946895155 Ω -> 9530 Ω rounded to an E96 value
C1 = 334.35691799 nF -> 330 nF rounded to an E6 value
The capacitors either have to be accurate film capacitors or accurate NP0 a.k.a. C0G ceramic multilayer capacitors, definitely not ceramic class 2 or 3 capacitors (such as X7R, X5R, Y5V, Z5U). The more accurate the better, but the best you can get with these values is probably +/- 5 % tolerance.
Thanks. I will buy some bread boards to use. I guess I should get some that allow components to be mounted as close together as possible because the voltages that will be in the circuit will be about 4mv.
How can I determine the resistance of my preamps phono input? There is no schematic available for the Convergent Audio Technology preamp and I don't think it is stated in the user manual.
Having a think about shielding, placing your circuit away from transformers and avoiding other sources of noise would be a good idea.
It's usually in user manuals under a heading like "Technical information" or " Specifications". At least there is some information on their website, you have to click on Specs to see it:
https://www.catamps.com/legend
2 kohm for the MC input of the SL1 Legend Black Path Extreme
https://www.catamps.com/renaissance
4 kohm (user adjustable) for the SL1 Renaissance Black Path Extreme
When the target value for R4 is 52.65 ohm, both with 2 kohm and with 4 kohm amplifier input resistance, the best E96 value for the resistor in the RIAA recording correction circuit would be 53.6 ohm
I have some Mu metal sheeting (4" x 10') that I recently bought for a very good price (about $20) from a guy in Ukraine. If I come up with a circuit that works and sounds very good, I will put the final device in a metal enclosure entirely lined with Mu metal. I also recently bought some 26Ga, 75 ohm, Teflon dielectric and insulated, silver plated copper coax cable to use for any wire that needs to be used (like between the DAC output and this circuit's input).
I will keep the signal connection from my DAC chip output to the input of this circuit as short as possible and hardwired instead of using coax with RCAs. I will probably put the circuit's box on top of my CD player right above the DCA chip. I will only use RCA connections between the output of this circuit and my preamp phono stage input.
I have an older model, SL1 Signature MkIII, that does not have separate inputs for MC and MM cartridges. it has one phono input with an impedance of 47K. BUT it also has an adjacent "load" option where a resistor soldered between 2 RCAs can be added to the circuit. I have never added a "load" and just use the 47K input as is. Would it help my quest to use this load option and if so what do you think might be a good load to add?
Ken Stevens designed and built the first SL1 (Reference) model of his preamp in about 1985. I bought that one. Since then, every model has been a gradual improvement of pretty much the same basic circuit and renamed SL1 xxx... I think the current model is about the 12th iteration of the original model. Some models have have been minor upgrades and other more dramatic. The tubes used have changed only in the line stage where 6922s substituted for the 12AU7s starting with the SL1 Signature MkIII model. This resulted in less of a battle to keep the noise from degrading as tubes aged.
If I were not retired and had lots of cash, I would probably buy one of the several "Black Path" models that have Black Gate caps in them. 🙂 They are supposedly dead quiet which is a very high bar for any vacuum tube equipment.
I see. Just leave the amplifier at 47 kΩ and use a 52.3 Ω resistor in the RIAA recording correction circuit then.
MarcllvdG, I really appreciate your help. I hope we are coming into the home stretch
I think I understand parts of what the circuit you have provided do but not other parts. Please bear with me. I am learning on the fly here.
What I think the circuit is doing is applying a high pass and a low pass filter to the signal from my DAC to create a signal that is EQed to be the same as the signal that is applied to a vinyl recond. Is that correct or have I got that wrong?
If it is correct, how much will the circuit attenuate the signal that passes through it? In other words if, the voltage that is generated by the I/V conversion of the current from my DAC is say 10mv, how much voltage will remain after the signal passes through the filter circuit?
The other question I have is how do I deal with creating an impedance at the input to the circuit that the output of my DAC can reasonably deal with.
I think I understand parts of what the circuit you have provided do but not other parts. Please bear with me. I am learning on the fly here.
What I think the circuit is doing is applying a high pass and a low pass filter to the signal from my DAC to create a signal that is EQed to be the same as the signal that is applied to a vinyl recond. Is that correct or have I got that wrong?
If it is correct, how much will the circuit attenuate the signal that passes through it? In other words if, the voltage that is generated by the I/V conversion of the current from my DAC is say 10mv, how much voltage will remain after the signal passes through the filter circuit?
The other question I have is how do I deal with creating an impedance at the input to the circuit that the output of my DAC can reasonably deal with.
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It emphasizes the high frequencies in accordance with the RIAA recording characteristic (the same as is applied to vinyl records) up to a certain frequency, namely 35 kHz with the values I recommended, where the response levels off. The theoretical RIAA recording curve keeps going up indefinitely with frequency, so you have to stop following it somewhere. Mathematically, a response that follows the theoretical RIAA recording curve up to a certain frequency and then levels off is equivalent to the response of a cascade of a (hypothetical) ideal RIAA recording curve circuit and a first-order low-pass filter.
The reason I recommended 35 kHz for the frequency where it levels off is that I expect that the overall response including the digital filter and the phono preamplifier will be as flat as it gets with 35 kHz.
The resistor R1 of the circuit is supposed to be the current-to-voltage converting resistor. I've chosen 10 Ω because I thought I read in one of the posts of this thread that the DAC works well with 10 Ω. With a 4 mA peak-peak output current, the voltage across the 10 Ω would be 40 mV peak-peak or about 14 mV RMS.
(10 Ω is not exactly according to spec, though. According to the February 1991 datasheet of the TDA1541A, page 7, footnote 1, the permitted output voltage compliance is +/- 25 mV to ensure no performance losses. With a maximum output current that can lie anywhere between 3.4 mA and 4.6 mA, that boils down to 5.43 Ω rather than 10 Ω. Then again, this datasheet spec is probably conservative.)
At 1 kHz, the output voltage of the circuit is about twenty times less than the voltage across R1, so around 0.7 mV RMS. That's about 7 dB to 8 dB more than the 0.3 mV from your MC cartridge, but this is a maximum level, while cartridge levels are usually nominal levels. Chances are that the DAC will sound slightly softer than the cartridge.
Thank you again MarcelvdG. When all others seemed to have abandoned me, you have continued to help me in my quest.
I hope you will help me sort out any problems that I may encounter when I build your recommended circuit and hook it up between my CD880's DAC output and my preamp's phono stage input.. You are a hero for bringing me to this point in my quest.
I hope you will help me sort out any problems that I may encounter when I build your recommended circuit and hook it up between my CD880's DAC output and my preamp's phono stage input.. You are a hero for bringing me to this point in my quest.
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I want to apologize to everyone for not understanding what an IRIAA circuit actually is at the outset. The common definition still does not make sense to me but it is what it is.
The irony is that what everyone here said it is is the same as what I eventually found on a site for DIY record makers called "lathetrolls.com". It still boggles my brain that the RIAA EQ that is applied to a record is called "inverse" RIAA EQ instead of RIAA EQ.
In any case, I am not beyond admitting my mistakes when I commit them. Thank you all.
The irony is that what everyone here said it is is the same as what I eventually found on a site for DIY record makers called "lathetrolls.com". It still boggles my brain that the RIAA EQ that is applied to a record is called "inverse" RIAA EQ instead of RIAA EQ.
In any case, I am not beyond admitting my mistakes when I commit them. Thank you all.
Noise.
0.3mV is a very low level signal. 2V is a much more robust signal that can withstand/reject background and RF noise in circuits far more easily.
Others have been so nice to warn you that this is technically not a very good solution. I agree with that, but I have seen people on this and other audio forums do stranger things and be happy with the result, so why not try it?
You will have to disconnect the DAC outputs from the op-amp current-to-voltage converters inside the CD player. Can you do that without causing unrepairable damage? Otherwise you can't revert the change if you don't like the results.
Yes. Not only a technically bad solution, but it also goes directly against his stated goal.
So it is only natural that people try to warn and discourage him.
Of course he can change his goal anytime he wants and have fun the way he likes.
It will be interesting to see what comes out of it, it is technically an interesting adventure.
Jan
So it is only natural that people try to warn and discourage him.
Of course he can change his goal anytime he wants and have fun the way he likes.
It will be interesting to see what comes out of it, it is technically an interesting adventure.
Jan