now the LT spice file with higher idle current as here recommended: post 268
Change the 8 x15 k to 5,1k, 4x 22 to 6,8R and the OPA output resistor from 100 to 22R. Instead of 5,1k resistors it is possible to set CRD 3,5 mA diodes.
at all upper resistors
I check
I R8= 2,81mA
I R21= 5,11mA
I R10= 10,84mA
I R1= 2,81mA
I R29= 4,65mA
Summary: 26,22mA each rail
Change the 8 x15 k to 5,1k, 4x 22 to 6,8R and the OPA output resistor from 100 to 22R. Instead of 5,1k resistors it is possible to set CRD 3,5 mA diodes.
at all upper resistors
I check
I R8= 2,81mA
I R21= 5,11mA
I R10= 10,84mA
I R1= 2,81mA
I R29= 4,65mA
Summary: 26,22mA each rail
Hi Chris,
I do indeed appreciate your efforts.
Meanwhile, I have got my brand new toy: Focusrite Scarlett Solo 4Gen.
Here are my recent results. Below, I have shown measurement results of practically unchanged preamp. I have replaced R100 with R300 to reduce gain.
On the first snapshot I have presented measurements of Scarlett Solo 4Gen loopback and in the 2nd snapshot there is measurement of C-3850 at 1.858V p-p output.
Contribution of C-3850 to overall distortion is indeed negligible. Practically almost none. This is really excellent preamp.
PS: Please note that the results presented in post #39 were obtained with somewhat inferior sound card (Xonar U7 MkII). Now, we have much better results.
Figure 1. Focusrite Scarlett Solo 4Gen
Figure 2. C-3850 at 1.858 Vp-p
I do indeed appreciate your efforts.
Meanwhile, I have got my brand new toy: Focusrite Scarlett Solo 4Gen.
Here are my recent results. Below, I have shown measurement results of practically unchanged preamp. I have replaced R100 with R300 to reduce gain.
On the first snapshot I have presented measurements of Scarlett Solo 4Gen loopback and in the 2nd snapshot there is measurement of C-3850 at 1.858V p-p output.
Contribution of C-3850 to overall distortion is indeed negligible. Practically almost none. This is really excellent preamp.
PS: Please note that the results presented in post #39 were obtained with somewhat inferior sound card (Xonar U7 MkII). Now, we have much better results.
Figure 1. Focusrite Scarlett Solo 4Gen
Figure 2. C-3850 at 1.858 Vp-p
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I think that in the technical issue I already announced that it had good measures in specifications, but its sound (at least for me, is very flat, it does not tell me anything), has anyone tried any sound improvement in listening with any of these modifications, it is quite common to hear audio components with spectacular measures, but then people do not like it, in fact the JC2 clone with worse averages, sounds for me much better, where is that point of improvement, operational, transistors, configuration, I have several for friends and for other things, but I do not listen to it, precisely for that reason, the ideal would be to seek improvement in listening rather than in the performance that already has, greetings.
From measuring point of view one ones their equipment be a wire with gain. Detracting and adding nothing.
From listening perspective one could like a sound with adding a little pepper and salt. How much off each depends on the person and partnering equipment.
If ones said this pre-amp sounds better when adding a little bit of salt, I believe him/her. But it doesn't mean it will be good in my system. Maybe my source or power amp add that little bit of salt already.
Adding a salted pre-amp can be to much then and one without will sound better.
If JC2 is better in your system and to your ears, go for that one.
What's the point of trying to mimic this pre-amp with the JC2 right?
At least that's how I see it.
From listening perspective one could like a sound with adding a little pepper and salt. How much off each depends on the person and partnering equipment.
If ones said this pre-amp sounds better when adding a little bit of salt, I believe him/her. But it doesn't mean it will be good in my system. Maybe my source or power amp add that little bit of salt already.
Adding a salted pre-amp can be to much then and one without will sound better.
If JC2 is better in your system and to your ears, go for that one.
What's the point of trying to mimic this pre-amp with the JC2 right?
At least that's how I see it.
@Berlusconi
That's the none modified version right?
Any idea what may cause the small bump around 3k?
Yes. I have used all components from the kit, assuming that there are no "Wunderwaffe" (Ger: Wonder veapon) components that would improve the sound. Results prove that assumption.
Regarding the sound quality I absolutely concur with you. The entire audio chain must be as close as possible to the ideal "amplifier wire". Then we may listen to the original recording. Adding sound to the original just obfuscates technical problems that exist elsewhere: bad recording, inadequate mastering, low quality DAC etc. Then, one assumes that addition of distortion solves the existing problem. In fact, this just makes it bearable.
I will let Michael Beeny to explain this in his very original way. Just listen to this. Hilarious.
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Hi
building finished. Test okay. setup is with bigger idle current. OPA LM49720 is inside now.
under the pcb i solder additionally to the film cap to each rail a 10µF silmic 2 cap.
Gain 5,14dB, DC offset is not immeasurable 0,00mV
input shorted and load is 10k ohms.
maximum is 3,3Vrms without getting clipped..that is 17,3Vpp!
test is done with 2Vrms input:
fg low is 1 Hz
fg high is about 400kHz...could get more but the phase shift is for me enough...
square wave tested with 10kR +47nF(49,4nF)
pro:
sound is in the first 20 minutes hard and "forwarding"...partly annoying...after 4 hours I can say without comparison with other pre amps:
this pre-amp is quick, sound neutral, deep bass, high are very open without S, Z, TZ, noises.... sound stage is deep and wide,...
cons:
a little bit more ground is missing- singers should have more feet, piano is always a bit hard, less body at singers and instruments( short/less resonant)...but it is not fair i own a NUVISTA 600 integrated.
the pre-amp has a loud turn on/off pop - so switch off the power amp !
fine preamp.
chris
building finished. Test okay. setup is with bigger idle current. OPA LM49720 is inside now.
under the pcb i solder additionally to the film cap to each rail a 10µF silmic 2 cap.
Gain 5,14dB, DC offset is not immeasurable 0,00mV
input shorted and load is 10k ohms.
maximum is 3,3Vrms without getting clipped..that is 17,3Vpp!
test is done with 2Vrms input:
fg low is 1 Hz
fg high is about 400kHz...could get more but the phase shift is for me enough...
square wave tested with 10kR +47nF(49,4nF)
pro:
sound is in the first 20 minutes hard and "forwarding"...partly annoying...after 4 hours I can say without comparison with other pre amps:
this pre-amp is quick, sound neutral, deep bass, high are very open without S, Z, TZ, noises.... sound stage is deep and wide,...
cons:
a little bit more ground is missing- singers should have more feet, piano is always a bit hard, less body at singers and instruments( short/less resonant)...but it is not fair i own a NUVISTA 600 integrated.
the pre-amp has a loud turn on/off pop - so switch off the power amp !
fine preamp.
chris
Attachments
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Nice build. That little box looks cute.
Could you make some distortions plot of your build?
How did you compare it to the nuvista? That amp doesn't have a power input right?
no THD measurements possible. have no equipment.
compare will come after some days "burn in"
what do you mean with
That amp has no power input right?
i have no volume pot. i change my volume on my laptop over streaming to my PS audio DAC.
kr
chris
compare will come after some days "burn in"
what do you mean with
That amp has no power input right?
i have no volume pot. i change my volume on my laptop over streaming to my PS audio DAC.
kr
chris
i think i did yesterday a stupid thing.
after switching off the pre amp i heard a loud pop. then i made the mistake and switched again on - the same - POP!
okay now i realized that the on/off pop is loud...****...then i switched off without power amp.
now i want to have a listening session and the pre amp is dead. i checked fuses...the 315mA primary fuse was blown!
Why can this happend???..maybe to fast switch on/off/on ..caps are not so much?
the amp is now playing...lets enjoy listening..
after switching off the pre amp i heard a loud pop. then i made the mistake and switched again on - the same - POP!
okay now i realized that the on/off pop is loud...****...then i switched off without power amp.
now i want to have a listening session and the pre amp is dead. i checked fuses...the 315mA primary fuse was blown!
Why can this happend???..maybe to fast switch on/off/on ..caps are not so much?
the amp is now playing...lets enjoy listening..
chermann
"maximum is 3,3Vrms without getting clipped..that is 17,3Vpp!"
What equations have been used here?
"maximum is 3,3Vrms without getting clipped..that is 17,3Vpp!"
What equations have been used here?
Good evening
i am sad to report that i have hum on my speakers.
as i wrote before i start to change the prim. fuse with 315mA and the amp is playing music....i just listening 30 seconds and let the amp alone for a small dinner...back to the music was playing but i hear something strange in between the music...i stop playing this track and i hear a loud hum out from both speakers...****... hum sound like 50/100HZ hum
i changed the voltage regulators and the in the second step the opamp...still the same
...after swich on the pre-amp is no hum....but after about 30 sec you hear that it getting louder and louder...this is not acceptable...
i have to check the pcb...sound is still here but the background hum is annoying. i guess i "loos" GND connection somewhere?...not?
any help is appreciated
chris
i am sad to report that i have hum on my speakers.
as i wrote before i start to change the prim. fuse with 315mA and the amp is playing music....i just listening 30 seconds and let the amp alone for a small dinner...back to the music was playing but i hear something strange in between the music...i stop playing this track and i hear a loud hum out from both speakers...****... hum sound like 50/100HZ hum
i changed the voltage regulators and the in the second step the opamp...still the same
...after swich on the pre-amp is no hum....but after about 30 sec you hear that it getting louder and louder...this is not acceptable...
i have to check the pcb...sound is still here but the background hum is annoying. i guess i "loos" GND connection somewhere?...not?
any help is appreciated
chris
