Hi.
I'm aware of the million threads on the famous RIAA phono preamp with all the re- de- pre-emphasis discussions, and I really got tired of searching the internet and not finding anything useful.
I just built one of those (google "PAiA - RIAA phono preamp kit" and the schematic pops up) and it works but it has the characteristic EQ curve with lots of treble and no bass.
I wonder if it is possible to built one of those preamps with a usable EQ curve that amplifies exactly the same sound that come off the record and converts it to line level or even a balanced line level as those used in professional mixing consoles?
Thanks in advance for any reply.
Phantombox
I'm aware of the million threads on the famous RIAA phono preamp with all the re- de- pre-emphasis discussions, and I really got tired of searching the internet and not finding anything useful.
I just built one of those (google "PAiA - RIAA phono preamp kit" and the schematic pops up) and it works but it has the characteristic EQ curve with lots of treble and no bass.
I wonder if it is possible to built one of those preamps with a usable EQ curve that amplifies exactly the same sound that come off the record and converts it to line level or even a balanced line level as those used in professional mixing consoles?
Thanks in advance for any reply.
Phantombox
What exactly is the problem? What do you mean by "it has the characteristic EQ curve with lots of treble and no bass"? Is the RIAA in error?
jd
Just off the top of my head , I can't see anything wrong with that schematic...
If you built it , are you sure you didn't mix up some of the parts? I've built several 5532 based RIAA pre's to be used with radio mixers without any problems - sounds quite OK. Maybe not super-duper Hi End, but actually very much OK
If you built it , are you sure you didn't mix up some of the parts? I've built several 5532 based RIAA pre's to be used with radio mixers without any problems - sounds quite OK. Maybe not super-duper Hi End, but actually very much OK
What I mean is that the preamp that I built is exactly to specifications according to the schematic, and unless I made the same mistake on both channels (L + R) and my preamp don't "de-emphasizes", then I'd say that the RIAA is in error.
Fortunately I'm not such a square-head... Let me check my design over again, see if I really missed something.
Fortunately I'm not such a square-head... Let me check my design over again, see if I really missed something.
But how do you know it is in error? Did you measure? Does is sound somehow wromg? What's the problem?
jd
A phono preamp without the confusing RIAA stuff would not correctly reproduce the signal on the record.
RIAA equalization - Wikipedia, the free encyclopedia
RIAA equalization - Wikipedia, the free encyclopedia
Just go Here..And use what you have..
http://www.diyaudio.com/forums/analogue-source/57398-phonoclone-vsps-pcb-help-desk.html
http://www.diyaudio.com/forums/analogue-source/57398-phonoclone-vsps-pcb-help-desk.html
Hi PhantomBox,
Here in USA, we celebrated Presidents Day on Monday (didn't have to work that day) so I took the chance to check out the circuit of the "PAiA - RIAA phono preamp kit" and derived a mathematical model for it. This model defines its transfer function, which I then used to find the idealized component values, by equating its coefficients with those of the RIAA curve.
Are you still interested in using the "PAiA - RIAA phono preamp kit" if I were to provide you with the correct component values ?
Regards
Peter
Here in USA, we celebrated Presidents Day on Monday (didn't have to work that day) so I took the chance to check out the circuit of the "PAiA - RIAA phono preamp kit" and derived a mathematical model for it. This model defines its transfer function, which I then used to find the idealized component values, by equating its coefficients with those of the RIAA curve.
Are you still interested in using the "PAiA - RIAA phono preamp kit" if I were to provide you with the correct component values ?
Regards
Peter
Hi PhantomBox,
No, I don’t mind sharing these results with you and any other DIYAUDIO member.
Here are the changes, which I've referenced to the schematic you linked to in your first post ie, PAiA - RIAA Phono Preamp Kit
Change C3/C8 from 47uF to 220uF
Change C4/C9 from 1nF to 2.136nF
Change C5/C10 from 4.7nF to 6.247nF
Change R4/R8 from 68K to 38.02K
With these value changes entered into a Spice simulation I was able to verify the compliance of the response to within +/-0.05dB compared to the response of the RIAA standard.
The value of C4/C9 can be constructed by paralleling a 1.8nF with a 330pF, C5/C10 can be constructed by paralleling a 5.6nF with a 680pF and for R4/R8, a 38.3K can be used.
I suggest that you use +/-2% tolerance or better for the capacitors (except C3/C8) and for resistors, use +/-1%.
The value of C3/C8 has been made large so as to minimize the low frequency droop that would otherwise result with the original value of 47uF.
However, with a 100uF capacitor, a loss of only 0.15dB at 20Hz results, but of greater benefit would be the increased attenuation of unwanted signals caused by record warp. In other words, it will provide a better rumble filter.
As is common with this circuit topology there is an extra zero in the transfer function that is located at just over 212KHz. At 20KHz, the effect of this extra zero is quite minimal and for the circuit values I’ve given you above, a rise in the response of about 0.03dB is observed together with a phase change of 5 degrees. Hope all this helps.
Have fun.
Peter
No, I don’t mind sharing these results with you and any other DIYAUDIO member.
Here are the changes, which I've referenced to the schematic you linked to in your first post ie, PAiA - RIAA Phono Preamp Kit
Change C3/C8 from 47uF to 220uF
Change C4/C9 from 1nF to 2.136nF
Change C5/C10 from 4.7nF to 6.247nF
Change R4/R8 from 68K to 38.02K
With these value changes entered into a Spice simulation I was able to verify the compliance of the response to within +/-0.05dB compared to the response of the RIAA standard.
The value of C4/C9 can be constructed by paralleling a 1.8nF with a 330pF, C5/C10 can be constructed by paralleling a 5.6nF with a 680pF and for R4/R8, a 38.3K can be used.
I suggest that you use +/-2% tolerance or better for the capacitors (except C3/C8) and for resistors, use +/-1%.
The value of C3/C8 has been made large so as to minimize the low frequency droop that would otherwise result with the original value of 47uF.
However, with a 100uF capacitor, a loss of only 0.15dB at 20Hz results, but of greater benefit would be the increased attenuation of unwanted signals caused by record warp. In other words, it will provide a better rumble filter.
As is common with this circuit topology there is an extra zero in the transfer function that is located at just over 212KHz. At 20KHz, the effect of this extra zero is quite minimal and for the circuit values I’ve given you above, a rise in the response of about 0.03dB is observed together with a phase change of 5 degrees. Hope all this helps.
Have fun.
Peter
Hi PhantomBox,
I’m not sure I understand your question, so I will give you two scenarios.
With reference to the attached Spice simulations, the blue curve shows the response if all of the component values are changed to the ones I posted, except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively (as in your post).
The red curve shows no components having been changed except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively.
These responses are error responses relative to the RIAA curve.
Regards
Peter
I’m not sure I understand your question, so I will give you two scenarios.
With reference to the attached Spice simulations, the blue curve shows the response if all of the component values are changed to the ones I posted, except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively (as in your post).
The red curve shows no components having been changed except C4/C9 and C5/C10, which I have made 1nF+1nF and 4.7nF+1nF respectively.
These responses are error responses relative to the RIAA curve.
Regards
Peter
I'm thinking about buying the PAiA RIAA kit, and change the component values as suggested by PLB.
But then I found this:
Circuits Online - Schakelingen - RIAA phono voorversterker
It's the same circuit as the PAiA RIA, but with the 1nF cap wired differently.
Could it be that PAiA have simply made a small error in their schematic?
Does the Circuits Online version match the RIAA standard more closely than the PAiA version?
But then I found this:
Circuits Online - Schakelingen - RIAA phono voorversterker
It's the same circuit as the PAiA RIA, but with the 1nF cap wired differently.
Could it be that PAiA have simply made a small error in their schematic?
Does the Circuits Online version match the RIAA standard more closely than the PAiA version?
Nahh, I guess it's just as bad as the PAiA version.
I'll try to get hold of the approximated component values. I'm thinking of something in the line of:
C4/C9 = 2000pF polystyrene || 130pF silver mica
C5/C10 = 6200pF polystyrene || 47pF silver mica
R4/R8 = some serial combination to get ~38ohm.
That should work, right?
I'll try to get hold of the approximated component values. I'm thinking of something in the line of:
C4/C9 = 2000pF polystyrene || 130pF silver mica
C5/C10 = 6200pF polystyrene || 47pF silver mica
R4/R8 = some serial combination to get ~38ohm.
That should work, right?
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