Is R15 1M correct and is the output impedance as low as say 240k at this point?
If you want to use 10n for C7 I arrive at R15 218k7, R16 31k8 and C8 3n43.
If you want to use 10n for C7 I arrive at R15 218k7, R16 31k8 and C8 3n43.
See the simulation in post 2929. I put in the same values. It has to be seen if the helper transistors in post 2961 raise the output impedance.
This last circuit does away with the risk of frying the cart....I like that...as it also removes any adjustments from the input.....
I like your servo that sense at the output and injects before the buffer better
I see the change of gain with different carts, but I don't see it as a problem as is is possible to change gain with by jumpering different RIAA networks.
I like your servo that sense at the output and injects before the buffer better
I see the change of gain with different carts, but I don't see it as a problem as is is possible to change gain with by jumpering different RIAA networks.
Well, today I have listened to op amp version. Servo worked as expected so it was dc coupled. At first glance everything was ok, plenty of gain, but after couple records I realized that something was gone, something that was so appealing about this circuit - ultimate transparency and micro details. Clearly OP275 is not up to the task here, even though it is really not a bad op amp, jfet (or bipolar hybrid, I should check...) input and so on. So I reverted back, mmmm.... much better 🙂
I sim'ed current mirrors with helper transistors and if multisim is not lying, output impedance raised from 320k to 717k, so this gives me nice RIAA caps values and good bump in gain. This could be enough, I'm going to check it now.
About your last transconductance circuit. At first look I have some doubts. I think input pair would not conduct, it would just float, and grounding sources would leave only one current mirror working, but maybe I'm wrong, I will check it later.
I sim'ed current mirrors with helper transistors and if multisim is not lying, output impedance raised from 320k to 717k, so this gives me nice RIAA caps values and good bump in gain. This could be enough, I'm going to check it now.
About your last transconductance circuit. At first look I have some doubts. I think input pair would not conduct, it would just float, and grounding sources would leave only one current mirror working, but maybe I'm wrong, I will check it later.
Maybe post 2961 works when you float the cartridge between gate and source of the input Fet, ground not connected. At the source there should still be nearly zero DC.
Anyway, nice that you can get more gain with the helper transistors. In the Opamp version you could try to flip the leads at the cartridge. Maybe the phase inversion results in the strange sound you get. Anyway, if you get it going without the Opamp thats more elegant.
Anyway, nice that you can get more gain with the helper transistors. In the Opamp version you could try to flip the leads at the cartridge. Maybe the phase inversion results in the strange sound you get. Anyway, if you get it going without the Opamp thats more elegant.
I keep getting your pdf´s in three pages. The middle page has the schematic and the others have some components designations (all in a bundle... unreadable) is this avoidable ?
It's dead quiet Joachim, only broadband noise (2mV/div in foto). Yes, you are right, in my case resulting gain is ~52dB. With 6Ohm cart. that would be way much more. I attached circuit as build and some sims, any tricks and tips would be appreciated. I really like it, I'm even considering upgrading my preamp for more gain if that's the last resort.
I see you started new thread for nobrainer. That looks elegant/interesting too, I may give it a try, just were did I put those low noise 2sc/2sa...
Hi Sampler
What is the 100k trimmer (R3) needed for in your Starless version ?
Like this :
Hi Joachim
Looking at your last schematic, I estimate the first stage output impedance should be around 286k... am I correct ?
The opamp arrangement on the output acts just as a servo or does it have amplification ?
No, output impedance is over 700kOhm so the 1Mohm resistor is not right. Sorry, that the schematic appears on page two. It has reasons that are hard to explain.My drawing program tries to put known component names to the semiconductors. Because it uses only weak artificial intelligence it has no idea about what i use. Removing the not used names shifts the component names up and down, creating 3 pages. I do not think that you need spoon feeding, just read EVERYTHING i post here and you will be able to make the best phono stage in the word in a minute. The Opamp has gain. I try to help sampler to get enough gain with his DL103 into my transimpedance input. "I am not perfect, but i am perfect for you "
Grace Jones.
Grace Jones.
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I am reading... carefully 🙂
I really like your design.... Would it work with a benz ACE M (0.8mV output) ?
So IOP2 is the servo and compares DC offset with GND, feeding the difference to the other opamp. That 1u (C1) must have a big impact in the final voicing... what type do you use ?
I really like your design.... Would it work with a benz ACE M (0.8mV output) ?
So IOP2 is the servo and compares DC offset with GND, feeding the difference to the other opamp. That 1u (C1) must have a big impact in the final voicing... what type do you use ?
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What impedance does the ACE M have ? What schematic are you referring too ? Using a servo is a two side sword. It will not have much impact on the treble response so some authorities like Malkolm Hawksford ( my "father" ) uses a simple TL071. By 1kHz the gain has rolled off. Others claim that they can even hear the opamp used. For the cap i usually use Wima MKT. I f i want to scare the demons away i use EVOX-RIFA PPS:
That is my preference :
https://www.distrelec.de/folienkond...63-vac/evox-rifa/smc16-5105j100c31tr24/820150
https://www.distrelec.de/folienkond...63-vac/evox-rifa/smc16-5105j100c31tr24/820150
Thank you.
This is the schematic I am refering to: http://www.diyaudio.com/forums/analogue-source/154210-mpp-297.html
The benz ACE M has 24ohm output imp. and 0.8mV out
This is the schematic I am refering to: http://www.diyaudio.com/forums/analogue-source/154210-mpp-297.html
The benz ACE M has 24ohm output imp. and 0.8mV out
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When it is the schematic with the helper transistors you will get 64dB of gain with your Ace M. That should be more then enough. Gain can be changed by changing the components in the RIAA. For example if you half the values of the resistors and double the caps you get 6dB less gain. It also works the other way around.
I like the parameters of your cartridge. That gives a good combination of low distortion and decent noise performance into my circuit.
I like the parameters of your cartridge. That gives a good combination of low distortion and decent noise performance into my circuit.
That is new concept for me. I mean modifying the Riaa values to set gain. I will do that because I only need 48 ~50dB gain.
Acording to my calculations, using C7 = 20n I need R16 = 15k9; C8 = 6.86n; R15 = 1M and output impedance of the first stage (the one with the wilson mirrors) should be 122k8.
Can you verify my calculations ? What about R17... can it stay as 1k ?
Acording to my calculations, using C7 = 20n I need R16 = 15k9; C8 = 6.86n; R15 = 1M and output impedance of the first stage (the one with the wilson mirrors) should be 122k8.
Can you verify my calculations ? What about R17... can it stay as 1k ?
Now i need the exact schematic. Your link did not send me there but in principle your calculations are right. Less gain buys you less distortion so if you do not need more, that is good.
Now i need the exact schematic. Your link did not send me there but in principle your calculations are right. Less gain buys you less distortion so if you do not need more, that is good.
Here it is:
Attachments
Ok, that one has over 700kOhm output impedance. The floating input has never being tried. Who has the guts to build it ?