New Schematic Linestage Tube Preamp using EF86 & 12AX7 - Page 5

Edwind · 24th January 2012, 09:44 AM

Thanks for the answer DF96.
I don't know how to create a model and simulate the schematic that I post and Lars.
Just want to know what exactly happened with that two circuit.
Maybe Lars can help?

SY · 24th January 2012, 09:49 AM

If this circuit gave you distortion and rolled off highs, then you have likely made a mistake somewhere in the construction (or elsewhere in your signal chain) and need to hunt that down.

Edwind · 24th January 2012, 10:05 AM

I've been checked more than 3 times.
Last Sunday, I also called my friend to come.
He checked again (found no mistakes) and did a blind test (I build a new one for Lars's circuit).
I used the same quality, marks, and types components but with different values for resistors.
The result are the same with me.
So I guest the answer must be THD, harmonics number, etc.

DF96 · 24th January 2012, 10:48 AM

The circuit is sufficiently simple that if properly built with the right value components it can't really go wrong. The volume control at the input will ensure it can handle any source, and there isn't really anything in it to roll off the treble. My conclusion is that either you haven't built what you/we think you have built, or you are not using it in the way you/we think you are using it.

revintage · 24th January 2012, 11:20 AM

So, how does the rest of your signal chain look? Something is wrong, but not in the lineamp, if you have built it according to the schematic.

Edwind · 24th January 2012, 12:10 PM

I agree with DF96, we maybe have different assumptions.

Lars:
I connect it directy to power amp by RCA interconnect cables. Just like usual, no other equipment such as line selector or passive pre-amp, etc.

By the way, I remember 3 years ago (or more) when I still not an audio-holic my friends said if I can heard loud differences as low as ±0.5dB or lower.
I don't know true or not what they said until now.
But, is it influent in my opinion "it's seem already roll of at 15kHz"?

revintage · 01:17 PM

You didn´t mention your source?

Measure and you will find that -3dB is at a few hundred kHz and THD, with mainly 2nd order harmonics, is far below 0,1%.

You found your previous design was low in distortion, and it is very far from!

So the only thing I can think of, is that your preferences maybe are a bit off as this one should be close to invisible. Could the loss at 15k be the absense of distortion?

Please report back when you have found/built something that suit you needs.

Edwind · 24th January 2012, 02:17 PM

Sorry I forgot, the source was CD-Player (NAD C-542).
As I wrote before, I don't have any measurement instruments.
Just LCR + multimeter only.
That's why I couldn't tell the value of THD, harmonics number, IMD, freq. response, crosstalk, phase shift, open and closed loop gain, input and output impedance, etc.
What I need is sound reproduction must as natural as possible to real sound, not only depending on instruments measurement values or theoretical calculation on paper/simulation.
Since there are a lot off stuff has 0.01% of THD on 1kHz, but all sound different one from another.
Any way all of you already help me as far as this time.
I'm very proud.
Thanks everybody.

24th January 2012, 09:49 AM	#42
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	If this circuit gave you distortion and rolled off highs, then you have likely made a mistake somewhere in the construction (or elsewhere in your signal chain) and need to hunt that down. __________________ If there's a sucker born every minute, where do the rest of them come from?

24th January 2012, 01:10 PM	#47
revintage diyAudio Member Join Date: May 2007	You didn´t mention your source? Measure and you will find that -3dB is at a few hundred kHz and THD, with mainly 2nd order harmonics, is far below 0,1%. You found your previous design was low in distortion, and it is very far from! So the only thing I can think of, is that your preferences maybe are a bit off as this one should be close to invisible. Could the loss at 15k be the absense of distortion? Please report back when you have found/built something that suit you needs. Last edited by revintage; 24th January 2012 at 01:17 PM.

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24th January 2012, 09:44 AM	#41
Edwind diyAudio Member Join Date: Jan 2012	Thanks for the answer DF96. I don't know how to create a model and simulate the schematic that I post and Lars. Just want to know what exactly happened with that two circuit. Maybe Lars can help?

24th January 2012, 10:05 AM	#43
Edwind diyAudio Member Join Date: Jan 2012	I've been checked more than 3 times. Last Sunday, I also called my friend to come. He checked again (found no mistakes) and did a blind test (I build a new one for Lars's circuit). I used the same quality, marks, and types components but with different values for resistors. The result are the same with me. So I guest the answer must be THD, harmonics number, etc.

24th January 2012, 10:48 AM	#44
DF96 diyAudio Member Join Date: May 2007	The circuit is sufficiently simple that if properly built with the right value components it can't really go wrong. The volume control at the input will ensure it can handle any source, and there isn't really anything in it to roll off the treble. My conclusion is that either you haven't built what you/we think you have built, or you are not using it in the way you/we think you are using it.

24th January 2012, 11:20 AM	#45
revintage diyAudio Member Join Date: May 2007	So, how does the rest of your signal chain look? Something is wrong, but not in the lineamp, if you have built it according to the schematic.

24th January 2012, 12:10 PM	#46
Edwind diyAudio Member Join Date: Jan 2012	I agree with DF96, we maybe have different assumptions. Lars: I connect it directy to power amp by RCA interconnect cables. Just like usual, no other equipment such as line selector or passive pre-amp, etc. By the way, I remember 3 years ago (or more) when I still not an audio-holic my friends said if I can heard loud differences as low as ±0.5dB or lower. I don't know true or not what they said until now. But, is it influent in my opinion "it's seem already roll of at 15kHz"?

24th January 2012, 02:17 PM	#48
Edwind diyAudio Member Join Date: Jan 2012	Sorry I forgot, the source was CD-Player (NAD C-542). As I wrote before, I don't have any measurement instruments. Just LCR + multimeter only. That's why I couldn't tell the value of THD, harmonics number, IMD, freq. response, crosstalk, phase shift, open and closed loop gain, input and output impedance, etc. What I need is sound reproduction must as natural as possible to real sound, not only depending on instruments measurement values or theoretical calculation on paper/simulation. Since there are a lot off stuff has 0.01% of THD on 1kHz, but all sound different one from another. Any way all of you already help me as far as this time. I'm very proud. Thanks everybody.