Mic, Line, EQ... Preamps

[still4given]

I know you love to do the math. All I did was physically measure the rail voltage at clipping while measuring the AC output with an RMS meter while looking at the scope.

 

[AndrewT]

Then you measured/recorded incorrectly.
You could not meaure 20Vac into your load when the supply voltage had sagged to 28Vdc ±xVripple.

 

[still4given]

What ever

 

[linuxguru]

mr. andrew,
attaching herewith the schematic. its not pretty but rest assured, the pcb layout as per post 505 and the attached schematic are consistant.
regards
prasi

Yes, checked the schematic at post #528 and the layout - they're consistent. Just auditioned one of these builds - the sonics are excellent and neutral, probably due to the simplicity of the signal path. Substitution of TL074 with an OPA4227 gives jaw-dropping transparency and detail, while still maintaining neutrality. I wouldn't use anything faster than the OPA4227 (8 Mhz GBW, 2.3V/usec SR, unity-gain stable), but YMMV.

 

[prasi]

Yes, checked the schematic at post #528 and the layout - they're consistent. Just auditioned one of these builds - the sonics are excellent and neutral, probably due to the simplicity of the signal path. Substitution of TL074 with an OPA4227 gives jaw-dropping transparency and detail, while still maintaining neutrality. I wouldn't use anything faster than the OPA4227 (8 Mhz GBW, 2.3V/usec SR, unity-gain stable), but YMMV.

Hi Linusguru,
Thanks for the confirmation of schema. I too had built one based on the scheme. I had used TL074.
reg
Prasi

 

[linuxguru]

Hi Linusguru,
Thanks for the confirmation of schema. I too had built one based on the scheme. I had used TL074.

In this application, TL074 is OK but a bit veiled. The Excaliber-series TLE2074 and TLE2142 should be better if you can get them. OPA4134 and OPA4227 are much better for transparency and detail. I haven't tried LME49740 because it's too fast and likely to have stability issues with this layout. I'll try re-design the layout later to keep trace lengths shorter.

 

[prasi]

In this application, TL074 is OK but a bit veiled. The Excaliber-series TLE2074 and TLE2142 should be better if you can get them. OPA4134 and OPA4227 are much better for transparency and detail. I haven't tried LME49740 because it's too fast and likely to have stability issues with this layout. I'll try re-design the layout later to keep trace lengths shorter.

Do share the layout and component adjustments done. I have been struggling with tone control for a long long time.

 

[mprivitera1]

Is this correct now??

Regards

HELLO ,
I built this prototype Preamp BJT, I have to test it, but without box, where to connect the "0"?

 

[mprivitera1]

HELLO ,
I built this prototype Preamp BJT, I have to test it, but without box, where to connect the "0"?

... Sorry, I did not realize that these are dual-voltage ..... 24-0-24

 

[mprivitera1]

Is this correct sir???
Can i use this for AX14 or LM3886??
What the minimum voltage for this pre amp?

Regards

Hi APEX , which has output impedance ?
Thank you

 

[jackin2]

In this thread I will post preamps, EQ, active x-overs, VU...
ML3 is Mic/Line XLR preamp with three band EQ +/-20dB
PCB size 100x40mm
Regards

Construya preamplificadores con ecualizador de 2 y 3 bandas

 

[jackin2]

link for downloads line apex ALL for sprint layout 6.0
donload on sprint layout 6.0
preamplifier and amplifiers :
https://mega.nz/#!zIQ1wCDS!8q0TiWmE3fCh_eOKa9URjCqYTf92FoWNe_H8OqotMQc

Sprint Layout 6.0 ISO Free Download

https://mega.nz/#!CMRQjKSR!nTSVAJ8S6J8x25EzMkLsIu66JAptT2j6gs2eFpiIzl0

https://mega.nz/#!OA4TAYBT!3owuNUWG7-gViEi4h5Yx8TuEwt8rmNTB22O-2--bhoc

https://mega.nz/#!KQg3BJoI!249M6D75L8oA6cjHOuvreKKHHT9X_xaCM6OvbBvWt9Q

https://mega.nz/#!XYhAzBDY!IkJWJCDPkAfKveAWnbn4gu0U61W4Ll3DaZUocqPV2rA

https://mega.nz/#!LRIx1baL!J8zei5duFMxQWtPAu8NLwz2BZKyWSPC8hdu9-wK5evo

https://mega.nz/#!qZw0AQQb!RAFesBJrRRrSrfFmX3fX4xQZYYgX1ZcD7jGf_Fp4XQc

https://mega.nz/#!7VADmKKJ!_soIbvMlIZbxrFc5QwJwMMjk9HVYQjAn7hDTv6oy86g

 

[us1070]

My build Apex first class psu is not working the left 2 watt resistor is getting very hot what could be the fault for this?

please see my attachment

 

[es44]

My build Apex first class psu is not working the left 2 watt resistor is getting very hot what could be the fault for this?

please see my attachment

You should take a picture of the soldering side too. The top looks a bit messy.

 

[still4given]

You need to make sure the pinouts of your jfets are correct. A lot of them have more than one pinout for the same part number.

 

[tnvijay]

Hello Mr. Mile sir.... My amplifier based on your lm3886 and stereo tone control is working fine. But I feel that bass is lacking. And sound seems very harsh on ears. I have used all components as per the layout. Should I change any components to make it pleasing to the ears?
Reg
Prasi

Hi Prasi,
From your pictures , I see you have used a log pot 10 k for bass and treble.That may be one reason for a uneven sound. You have to use a Linear pot 10 k. I have a apex tone control and its extremely good.

 

[sasek]

Stereo tone control with 2x10k

hi apex,
how I want to increase gain of this tone control?

 

[apexaudio]

hi apex,
how I want to increase gain of this tone control?

Replace 10k with 4k7 or 2k2, also you can replace 22k with 47k.

 

[sasek]

Replace 10k with 4k7 or 2k2, also you can replace 22k with 47k.

Sorry apex.i use different circuit.how about this circuit?

 

[apexaudio]

Sorry apex.i use different circuit.how about this circuit? View attachment 557422

This circuit is without gain.