analog_sa said:
I agree. Perhaps I need to be more careful with my language. It won't avoid the need for an output coupling cap. I was just trying to say that it will provide a path to ground at DC. All the thermal stability problems that you mentioned before still are there.
But I like the idea of being able to get rid of one of the RIAA network capacitor and replace it with an inductor. Some of the best phono stages that I have heard used Tango LCR networks so I like idea of moving in that direction.
---Gary
half true and half wrong.
I actually calculated the transfer function of the ONO and although they don't set the actual RIAA they create the low cut frequency response which frequency is 1/(2*pi*100*440u) which it think it is 3.7Hz.
Now if you lower the value of the capacitors too much they will affect the RIAA equalization.
Nevertheless, it's correct they can be shorted and apparently the RIAA should work fine.
I don't know.....i thought for a second that i tried to run a simulation through spice and short the cap and got a weird RIAA response...but i might be confusing it with something.
To cross-prove the statement i have just made i will re-run a simulation and see.
Anyways....going back to your point you said:
if you short these two caps the Circuit will be Temperature dependent and if i would use output coupling cap the cap will be overstressed and might become faulty with the age.
Have I understood correctly?
Anyways, if we would assume that the circuit work fine with the output coupling cap (without these 2 caps): Would the sound be not as good due to the DC instability?
My opinion is: no!
Technically it should be the same since, DC conditions will be the same with or without C1/41; the only difference would be that, any little DC change on the circuit due to temp variations, will be greatly amplified at the output.
The output coupling cap will take care of this by blocking DC at the output and the feedback loop will block the DC with the RIAA cap in series in the feedback path thus, BIAS correctly the input Diff amp.
Just my two cents.
Analog: would you have any chance, in case, to try to short the 2X220uF cap and installing an output coupling cap to see if there is in case any issue by doing that?
I actually calculated the transfer function of the ONO and although they don't set the actual RIAA they create the low cut frequency response which frequency is 1/(2*pi*100*440u) which it think it is 3.7Hz.
Now if you lower the value of the capacitors too much they will affect the RIAA equalization.
Nevertheless, it's correct they can be shorted and apparently the RIAA should work fine.
I don't know.....i thought for a second that i tried to run a simulation through spice and short the cap and got a weird RIAA response...but i might be confusing it with something.
To cross-prove the statement i have just made i will re-run a simulation and see.
Anyways....going back to your point you said:
if you short these two caps the Circuit will be Temperature dependent and if i would use output coupling cap the cap will be overstressed and might become faulty with the age.
Have I understood correctly?
Anyways, if we would assume that the circuit work fine with the output coupling cap (without these 2 caps): Would the sound be not as good due to the DC instability?
My opinion is: no!
Technically it should be the same since, DC conditions will be the same with or without C1/41; the only difference would be that, any little DC change on the circuit due to temp variations, will be greatly amplified at the output.
The output coupling cap will take care of this by blocking DC at the output and the feedback loop will block the DC with the RIAA cap in series in the feedback path thus, BIAS correctly the input Diff amp.
Just my two cents.
Analog: would you have any chance, in case, to try to short the 2X220uF cap and installing an output coupling cap to see if there is in case any issue by doing that?
Stefanoo said:
No. I don't have the patience to spell everything out and this is becoming a bit tiring.
To get any kind of sensible offset you have to trim the collector load resistor. With age resitors will change values, fets will also change. The offset can easily become several volts. Nothing will blow but this offset will reduce the output voltage swing or even latch the output to a ps rail.
analog_sa said:
Gotcha!
I was thinking the same issues
i.e. reduce of output swing or latching output to one PS rail.
Possible solution i have now in mind are:
1)DC servo
2)periodic trimming of the circuit through the resistor
3)leaving the 2 X 220uF cap on the RIAA
If you have time, you might try to see how the DC behaves with the caps shorted after having re-trimmed the resistor for 0V output voltage and check if the DC is stable.
If you don't have any chance, never mind, don't worry.
I will try the circuit as soon as i can anyways.
If i had the circuit already working here i would have tried for the sake of my curiosity, but maybe not all are as curious as i am...
I will shoot an order to digikey tomorrow morning...but since it's christmas time i am sure there will be delay on shipping and i won't get any chance to try the circuit before the new year
Hi Folks,
just to complete the subject.
I have just finished to build one CH of the MM stage without the 2 X 220uF cap.
Beside a 50Hz picked up at the output, but i believe it so the set up is a breadboard with wiring all over, there is no big issue with stability nor DC offset drifting.
I am not using the 10pF cap, nor the 100pF and the circuit is very stable, no HF oscillations.
But this could be due to the capacitance of the breadboard or maybe it just work this way.
I will keep on watching the offset.
It's moving a little bit, but not so much.
I have covered the circuit with a glass ball to simulate a metal enclosure.
How much Dc offset drifting is allowed? 10mV? i guess it would be too much, wouldn't it?
In the worse case in area i will use output coupling cap.
(i have build it without any cascode to simplify the process)
I am going to add the MC part and split the 2 RIAA section as shown and check the frequency response.
just to complete the subject.
I have just finished to build one CH of the MM stage without the 2 X 220uF cap.
Beside a 50Hz picked up at the output, but i believe it so the set up is a breadboard with wiring all over, there is no big issue with stability nor DC offset drifting.
I am not using the 10pF cap, nor the 100pF and the circuit is very stable, no HF oscillations.
But this could be due to the capacitance of the breadboard or maybe it just work this way.
I will keep on watching the offset.
It's moving a little bit, but not so much.
I have covered the circuit with a glass ball to simulate a metal enclosure.
How much Dc offset drifting is allowed? 10mV? i guess it would be too much, wouldn't it?
In the worse case in area i will use output coupling cap.
(i have build it without any cascode to simplify the process)
I am going to add the MC part and split the 2 RIAA section as shown and check the frequency response.
Hi Analog,
actually i am noticing that with the glass ball around the offset seems to be pretty stable no need for any coupling cap.
I still HAVE TO check BETTER but it seems to be stable after a settling time.
If so, i won't need any coupling cap at the output which it would be very nice indeed.
Conversely, sorry, but i will use the 1uF Aura Teflon cap
as coupling cap between MC and MM and at the output EVENTUALLY 
Right now i am selecting the resistors and the capacitors for the RIAA equalization network accordingly to the design i have done and i will check the RIAA eq precision.
actually i am noticing that with the glass ball around the offset seems to be pretty stable no need for any coupling cap.
I still HAVE TO check BETTER but it seems to be stable after a settling time.
If so, i won't need any coupling cap at the output which it would be very nice indeed.
Conversely, sorry, but i will use the 1uF Aura Teflon cap
as coupling cap between MC and MM and at the output EVENTUALLY Right now i am selecting the resistors and the capacitors for the RIAA equalization network accordingly to the design i have done and i will check the RIAA eq precision.
Stupid question.
as i am testing the output DC with the DVM connected at the output, i am noticing that when the phono is powered on the output DC starts at around 0.620mV or so and then quickly goes down in about 10s or so to 100mV and when powered off goes to the negative rail for a fraction of a second and super quickly to zero.
If everything would be DC coupled, then the speakers would blow, correct?
What is threshold for a decent output offset? 10mV 20mV 50mV?
Edit:
Very interesting i am trying to compare the Amp with and without the electrolytic cap on the RIAA.
by adding a big cap in series with the 100 ohm resistor to block the DC gain of the amplifier the output DC offset is down to 1mV or less right away and no fluctuation whatsoever.
I still want to try though to see if i can get a decent offset without.
Choices are restricted now:
1) Try to make it as temperature stable as possible by building something around inside the the metal case.
2) using a coupling cap at the output
3) using the DC gain stop capacitor at the RIAA network
It would be interesting to explore which one degrades the sound the least.
as i am testing the output DC with the DVM connected at the output, i am noticing that when the phono is powered on the output DC starts at around 0.620mV or so and then quickly goes down in about 10s or so to 100mV and when powered off goes to the negative rail for a fraction of a second and super quickly to zero.
If everything would be DC coupled, then the speakers would blow, correct?
What is threshold for a decent output offset? 10mV 20mV 50mV?
Edit:
Very interesting i am trying to compare the Amp with and without the electrolytic cap on the RIAA.
by adding a big cap in series with the 100 ohm resistor to block the DC gain of the amplifier the output DC offset is down to 1mV or less right away and no fluctuation whatsoever.I still want to try though to see if i can get a decent offset without.
Choices are restricted now:
1) Try to make it as temperature stable as possible by building something around inside the the metal case.
2) using a coupling cap at the output
3) using the DC gain stop capacitor at the RIAA network
It would be interesting to explore which one degrades the sound the least.
updates?
Stefano,
I recently pulled the ONO out and put it back in my system. I decided to try out an old MM cartridge that I had - the Grado 8MX. My NYAL Super It has too much gain for this cartridge so I switched to the ONO. The Grado likes a load of 10k ohms instead of the traditional 47k ohms, so I had to do a bit of soldering to get this right. Once I did that, the sound was really outstanding. I'd forgotten how good this phono stage can sound.
How are you doing with your ONO?
---Gary
Stefano,
I recently pulled the ONO out and put it back in my system. I decided to try out an old MM cartridge that I had - the Grado 8MX. My NYAL Super It has too much gain for this cartridge so I switched to the ONO. The Grado likes a load of 10k ohms instead of the traditional 47k ohms, so I had to do a bit of soldering to get this right. Once I did that, the sound was really outstanding. I'd forgotten how good this phono stage can sound.
How are you doing with your ONO?
---Gary
Hi Gary,
thank you very much for your interest.
I appreciate it.
I have lots of updates.
Lets start:
I tried the circuit I have attached on this 3d few weeks ago and the sound with my Denon DL103 was "excellent".
The quote is because the circuit was on a breadboard and since RIAA accuracy wasn't precise but still overall sound was natural probably due to the topology of the network.
After have been run this test, I decided to seriously work and improve the curcuit.
So i started to evaluate the amplifier before closing it on the RIAA.
I found frequency response not to be so extended.
Poor square wave response.
The amp, needs a compensation cap as the majority, of course, to introduce the dominant pole and shut down overshoots.
I basically didn't like it whatsoever and so i decided to change it.
Therefore i decided to go off on my own and build a completely new circuit.
In the past 3 weeks of work I finally came out just 2 days ago and perfect it yetsterday with a great ciruit on the breadboard.
Bandwidth at -3dB of the amplifier is 2.8MHz.
Hard work indeed and I am pleased with this.
There is stability on the DC offset and excellent low noise.
I am super proud of the technical aspect of my circuit.
No need for compensation cap.
Square wave is sharp and NO overshoots whatsoever.
I have to finish working on it and i will have to listen to it.
I also got a good soundcard after lots of research and an excellent program to match it that hopefully will allow me to do precise THD measurements and frequency response and thus allow me to build a very accurate RIAA network and to tweak the circuit for minimum distortion.
This plan sounds really interesting .
Alright, i have definitely written too much.
Thank you gary for your interest and i am glad you enjoyed your ONO.
thank you very much for your interest.
I appreciate it.
I have lots of updates.
Lets start:
I tried the circuit I have attached on this 3d few weeks ago and the sound with my Denon DL103 was "excellent".
The quote is because the circuit was on a breadboard and since RIAA accuracy wasn't precise but still overall sound was natural probably due to the topology of the network.
After have been run this test, I decided to seriously work and improve the curcuit.
So i started to evaluate the amplifier before closing it on the RIAA.
I found frequency response not to be so extended.
Poor square wave response.
The amp, needs a compensation cap as the majority, of course, to introduce the dominant pole and shut down overshoots.
I basically didn't like it whatsoever and so i decided to change it.
Therefore i decided to go off on my own and build a completely new circuit.
In the past 3 weeks of work I finally came out just 2 days ago and perfect it yetsterday with a great ciruit on the breadboard.
Bandwidth at -3dB of the amplifier is 2.8MHz.
Hard work indeed and I am pleased with this.
There is stability on the DC offset and excellent low noise.
I am super proud of the technical aspect of my circuit.
No need for compensation cap.
Square wave is sharp and NO overshoots whatsoever.
I have to finish working on it and i will have to listen to it.
I also got a good soundcard after lots of research and an excellent program to match it that hopefully will allow me to do precise THD measurements and frequency response and thus allow me to build a very accurate RIAA network and to tweak the circuit for minimum distortion.
This plan sounds really interesting
.Alright, i have definitely written too much.
Thank you gary for your interest and i am glad you enjoyed your ONO.
ok...
it's been awhile since my last post on this thread.
The phono stage is nearly completed.
In the next weeks i hope i will be able to come out with a working layout.
The circuit has been developed on the breadboard!! It's finally time to finalize it.
Some data:
- it is a 67.5dB 2 main gain stages.
- passive RIIA deemphasis network
- Measured RIIA accuracy within audible band is down to 0.05dB (yeah I know it is an incredible results for a one step network)
- no saturation even at frequency over 40KHz (no need to get so high though )
- frequency response is 0.7Hz -1.8MHz
- THD @1KHz 2.5Vpk-pk is < 0.02%
- no compensation cap on the circuit due to proper selection of parts for the various tasks and proper feedback; no cap for unity DC gain either
- DC offset, when phono is properly cased, is less than 2mV so far so good
- i have choosen to cap couple the 2 stages instead of developing a servo control system
- feedback factor is around 8dB
- circuit's parameter like biasing of the stage feedback factor where evaluated in terms of distortion improvements and during long listening tests.
- noise of the phono is good. i can only scope a 3mV pk-pk total noise after experimenting with many star point ground's startegy i could implement on the breadboard; i think i can ge a little better with a good layout and proper shielding. Anyways no audible noise from 2 steps away from the speakers and just a little hiss on the tweater at maximum volume withe the hear by.
what else can I say? the sound is excellent. I am a very piky and demanding person so it took me so long to develop something that i can considered to be an reference phono stage (at least for me and for the few others that had the chance to listen to it already).
More folks will follow as the project will be finalized.
it's been awhile since my last post on this thread.
The phono stage is nearly completed.
In the next weeks i hope i will be able to come out with a working layout.
The circuit has been developed on the breadboard!! It's finally time to finalize it.
Some data:
- it is a 67.5dB 2 main gain stages.
- passive RIIA deemphasis network
- Measured RIIA accuracy within audible band is down to 0.05dB (yeah I know it is an incredible results for a one step network)
- no saturation even at frequency over 40KHz (no need to get so high though
)- frequency response is 0.7Hz -1.8MHz
- THD @1KHz 2.5Vpk-pk is < 0.02%
- no compensation cap on the circuit due to proper selection of parts for the various tasks and proper feedback; no cap for unity DC gain either
- DC offset, when phono is properly cased, is less than 2mV so far so good
- i have choosen to cap couple the 2 stages instead of developing a servo control system
- feedback factor is around 8dB
- circuit's parameter like biasing of the stage feedback factor where evaluated in terms of distortion improvements and during long listening tests.
- noise of the phono is good. i can only scope a 3mV pk-pk total noise after experimenting with many star point ground's startegy i could implement on the breadboard; i think i can ge a little better with a good layout and proper shielding. Anyways no audible noise from 2 steps away from the speakers and just a little hiss on the tweater at maximum volume withe the hear by.
what else can I say? the sound is excellent. I am a very piky and demanding person so it took me so long to develop something that i can considered to be an reference phono stage (at least for me and for the few others that had the chance to listen to it already).
More folks will follow as the project will be finalized.
Hi everybody,
for whom of you who's interested, I finished my phono stage.
You can find the pics on this thread:
http://www.diyaudio.com/forums/solid-state/153341-my-latest-phonostage-creation.html#post1949754
finally it's is done....I am very happy of it.
for whom of you who's interested, I finished my phono stage.
You can find the pics on this thread:
http://www.diyaudio.com/forums/solid-state/153341-my-latest-phonostage-creation.html#post1949754
finally it's is done....I am very happy of it.
for whom of you who's interested, I finished my phono stage.
finally it's is done....I am very happy of it.
Stefanoo,
Congratulations. It looks very pretty and I'm sure it sounds as good as it looks.
It would be in the spirit of Diyaudio to share the details of the final circuit. We have had many good discussions in this thread and I think that you've learned some good things from the different people here.
Please consider giving something back.
Regards,
---Gary
Thanks Gary for your compliment. It is true....I have learned very much from different people on this forum. I think that's the purpose of sharing information with one another....to learn. As I mentioned on the other thread, I am hoping to commercialize my project...we'll see....so right now I am not in the disposicion to share "details" (schematic, topology, etc..). But we'll see in the future. What I would REALLY like to do....would be to have some of you listen to it.
Thanks for your interest Gary.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.