I really appreciate your help. It took me a while to understand what you were telling me (I am guessing that English is not your first language). I am beginning to think you are are only one who actually understood what I was hoping to do. As I said at the outset, I have never designed a circuit and have limited knowledge of the interactions of the components in my system. I had completely forgotten to take the need for adding RIAA equalization into account until you mentioned it.
This creates a new problem that may explain why I have never seen any circuit for inputting I/V converted DAC outputs into a preamp's phono stage inputs. The phono stage of a preamp has INVERSE RIAA EQUALIZATION included in its circuit to allow the preamp to output a flat signal after it REVERSES the RIAA equalization that was applied during the vinyl manufacturing process.
Sooooo... in order for it to be possible for a signal from a DAC to be used through a preamp's phono stage, it must either have RIAA equalization applied to it OR the inverse RIAA equalization circuit in the phono stage must be disabled .or removed.
Option 2 is out of the question because Ken Stevens guards the secrets of his preamp design with his life. None of the capacitors in his preamps are even marked with their values except the PS electrolytics. Besides that, I would not be willing to start cutting traces on the PCB or removing components just to find out what some circuit concept sounds like.
That only leaves me with option 1, but I cannot find any schematic for building an RIAA equalization circuit,\ (probably because it is not useful to anyone unless they are in the vinyl recording business). I did find an RIAA equalizer made by Esoteric Sound, Rek-O-Kut. Unfortunately, it is designed for adding various equalization curves to old 78 RPM record playback to make them playable through modern preamps and it only outputs mono after doing that. Besides that it costs way more than I am willing to spend on an idea that may or may not have good sound results.
If anyone knows where I might find a schematic for building a simple RIAA equalization circuit without chip op amps, I would greatly appreciate a link or at least a pointer for where to look for one. I have tried every search term I can think of without success. Please do not send info on building "inverse" or "reverse" RIAA circuits.
What is a T-switch?
I started working on building a line level circuit ala Lukus' Lampizator. I actually have chased down that rabbit hole for many years and am amazed at how many people have so many contrary opinions of his concepts and designs. Hell, just the debate over what value of resistor to use for I/V conversion is almost endless and that is just the beginning. Some people report great results and say they love the sound they got. Others say it is garbage compared to the results of decent op amp chips. At the end of the day. everyone's ears are different and preferences of what sounds good are as individual as snowflakes.
i generally prefer the sound of good tube gear. I have heard and have bought some excellent SS gear that sounds great. BUT, at the end of the day, I judge a piece of gear based on how it makes me "feel". If I feel relaxed and euphoric after a long listening session, then I am closer to audio nirvana and that is my goal... reaching audio nirvana.
Most people on this forum call the RIAA recording equalization 'reverse RIAA'. Passive circuits with such a transfer are often used for measuring the RIAA playback correction in phono preamplifiers, but they are usually designed to be driven with line level voltage signals rather than with a current straight from a TDA1541. The circuit of post #7 is supposed to have a RIAA recording equalization when driven with current, but it has some issues that make it impractical.
What is driving me crazy at this point is that there are so many schematics for SIMPLE inverse RIAA equalization circuits (that reverse RIAA equalization) on the internet but I can't find a single schematic that is equally simple for an RIAA equalization pre-emphasis circuit. I mean, if an inverse RIAA equalization circuit that reverses RIAA equalization can be built using only resistors and capacitors, it seems to me that there must be a way to add RIAA equalization to a flat signal just as simply. Any help finding info for a "simple" RIAA equalization (not inverse equalization) circuit schematic would be greatly appreciated.
I would not be using current directly from my TDA1541A. I would use the voltage after a resistor I/V conversion. This voltage signal is what I would need to apply RIAA equalization to to make it usable by the phono stage of my preamp which has a circuit in it that applies reverse RIAA equalization.
I looked at all of the circuits that have been posted by members so far and unless I am misunderstanding them, they appear to show inverse (reverse) RIAA equalization circuits which is opposite of what I would need to apply tp the flat signal from my DAC. Adding reverse RIAA equalization to the signal from my DAC would result in making the output from my preamp double reverse equalized not flat.
Some are attempts to be helpful. Others like this one are just insults.
Can you point me to a schematic for a simple circuit that uses only resistors and capacitors for adding RIAA equalization to a flat frequency signal? Until I clear that hurdle, I am stuck.
And, can we agree that "inverse" (reverse) RIAA equalization is the opposite of the RIAA equalization that is what is applied to every 33 1/3 RPM LP.
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It is just not a good idea... feed that into the preamp inputs.
Use 4x OS tda1541A with proper filter and clock, then to opamp I/V , feed this to a filter/buffer second opamp.
The second opamp removes the switching noises and buffer more for accurately send the audio without noise to the pre-inputs.
I tried all the ways with TDA and this is the only way. The I/V resistor only works well for BurrBrown dac types.
Use 4x OS tda1541A with proper filter and clock, then to opamp I/V , feed this to a filter/buffer second opamp.
The second opamp removes the switching noises and buffer more for accurately send the audio without noise to the pre-inputs.
I tried all the ways with TDA and this is the only way. The I/V resistor only works well for BurrBrown dac types.
Thanks I understand the principles and rationale of RIAA equalization. What I lack is the knowledge that is necessary to design and build circuits.
I am having some difficulty communicating with some members because I need to pass the flat signal from my DAC through an RIAA equalization network to make it possible to input the signal to my preamp's phono stage input and to output a flat signal to my amplifier. I realized this after member eclipsevl mentioned RIAA way back in the beginning of this thread.
I keep asking for a schematic of an RIAA equalizer network using only resistors and capacitors but for some reason many members think I need to apply inverse RIAA equalization to the signal from my DAC. My preamp phono stage will apply inverse RIAA equalization. Some have posted links to inverse RIAA equalization networks. In fact, this would not result in my preamp outputting a flat signal but would actually result in an output signal that is doubly boosted at low frequencies and doubly cut at high frequencies.
I really appreciate this forum and am trying to not let my frustration cause my replies to be sharp but it is difficult and I would appreciate a warning rather than a ban if I cross any forum rules.
Thanks but if I cannot figure out a way to do a simple resistor I/V conversion of the current signal from my DAC and then apply a simple resistor and capacitor RIAA equalization to the resulting voltage signal, I will go back to my original plan which was to eliminate the chip op amps in my Philips CD880 player and build a tube output. I already have almost everything I need to build that.
I don't think I will go all in and eliminate the 4x oversampling in any case but you never know. The problem with doing that is I don't want to give up my SPDIF output because I want to have the option to use my cd player as a transport only.
Ifvthe stated aim is to bypass your current I've stage then build another, there's loads on the forum.
The easiest way might be a transformer output stage. Bielsik might do a set already fir the tda1541
The easiest way might be a transformer output stage. Bielsik might do a set already fir the tda1541
Let me check the schematic , applying a I/V resistor you will screw up the sound , and RIAA even more, then the RIAA input more, then more,
The TDA just sounds like that , it is not impressive at all.... trying to get something out of it that it cannot do it impossible.
The TDA just sounds like that , it is not impressive at all.... trying to get something out of it that it cannot do it impossible.
Maybe upgrading the opamps to something like opa604 and taking the output out of PIN 7 , bypassing the double capacitors and the muting transistors...
More advanced mods is to use the DEM reclocker, there good luck...
More advanced mods is to use the DEM reclocker, there good luck...
rfbrw, I have seen worse than this...
coating drivers with metal sheets...
Using straight dac's v out into pre-amps, OUTCH...
Building some of the diy kits which are THD machines
Modifying a great amp from 50 watts to 100 watts with lower thd while screwing up all other parameters...
Removing filters, removing caps, installing DC servo everywhere.
Then there is this : playing vinyl through DAC .... I am just crying
Then all the filters all the active stuff...
Xos drivers too low,
MDF, MDF Open baffles, outch etc etc etc
I remember when I built MDF open baffles, it was the worst thing I ever built beside my new loudspeakers (too honest).
Then I redid it all in spruce boards , used a 12'x6 screwed that to my tall bookshelves back loaded with books, then I was !!! Awww this is how OB sounds like!!! haha
Driving tda through resistor i/v into RIAA then into PHONO, this I don't know were should it fit in the list.
coating drivers with metal sheets...
Using straight dac's v out into pre-amps, OUTCH...
Building some of the diy kits which are THD machines
Modifying a great amp from 50 watts to 100 watts with lower thd while screwing up all other parameters...
Removing filters, removing caps, installing DC servo everywhere.
Then there is this : playing vinyl through DAC .... I am just crying
Then all the filters all the active stuff...
Xos drivers too low,
MDF, MDF Open baffles, outch etc etc etc
I remember when I built MDF open baffles, it was the worst thing I ever built beside my new loudspeakers (too honest).
Then I redid it all in spruce boards , used a 12'x6 screwed that to my tall bookshelves back loaded with books, then I was !!! Awww this is how OB sounds like!!! haha
Driving tda through resistor i/v into RIAA then into PHONO, this I don't know were should it fit in the list.
I bought my CD880 new when they first came out and it has served me well without an failures since. I saved the Dutch Service Manual saved on my PC many years ago. Except for the schematics, it is of limited use to me because i do not understand Dutch. Yes, I plan to eliminate the op amps completely and I also plan to eliminate the two opposing analog out 220uf capacitors and use a lower value Auricap XO polypropylene film capacitor in their place. The best chip op amp is no chip op amp IMHO. YMMV
Are you trolling everyone or didn't you get the key message of post #43? You use a definition for reverse RIAA that's opposite to everyone else's. All the 'reverse RIAA' circuits you find everywhere are actually applying RIAA recording equalization/RIAA pre-emphasis. The only problem is that they need line level input signals, and a TDA1541 loaded with a small resistor produces a lot less than that.
Actually, I am not telling anyone they are wrong. Everyone has the opinion of what what sounds best and they are entitled to their opinion. What is happening is that I did not ask for anyone's opinion about what I want to try to do. I asked for help to achieve what I want to try.
If it sounds better than my CD880 did before I did the mod TO ME, I will keep it. If it sounds worst TO ME, I will undo it. It really is that and nothing more. If you have some input that will help me build what I want to do, please post that. If not please quit posting on this thread.