X-ccs bosoz need more gain - diyAudio
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Old 5th September 2016, 05:56 PM   #1
tonimxp is offline tonimxp  Italy
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Default X-ccs bosoz need more gain

Hi guy i just try to make some measures and i have just discovery that my x-ccs bosoz gain is only 2 or so (6db)

I compared its fft with my 6sn7 tube preamp ( i love his timbric),I'd likeit to amplify more (10db) and that had a predominance of second harmonic.
What are the elements that manage the gain ratio?
What can I do to manage the second harmonic distortion like I did with my F5 v2 turbo Power Amp?
To better interpret the values of the FFT 1Khz I also measured the sound card slot in 5,8db and 3,8db.
Later I performed the measurements on the X-ccs Bosoz.
My primary need, however, is trying to get more gain.
Please can you help me?
Thanks in advantage

Antonio
Attached Images
File Type: jpg IMG_20160905_0003.jpg (270.6 KB, 213 views)
File Type: png Scheda Audio FFT att..png (55.5 KB, 211 views)
File Type: png Scheda Audio FFT.png (55.5 KB, 187 views)
File Type: png x-ccs bosoz FFT att..png (56.6 KB, 183 views)
File Type: png x-ccs bosoz FFT.png (56.1 KB, 184 views)
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Old 5th September 2016, 06:58 PM   #2
Zen Mod is offline Zen Mod  Serbia
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as I said , for increasing gain - decrease value of both source resistors

regarding miniscule gain - triple check values of resistors you put on pcb

regarding invoking nonsymmetry in circ (invoking 2nd) , few tricks :

-different values of source resistors
-different values of drain resistors
-different values for NFB resistors (4K7/47K)

different meaning - not equal values left vs. right side

edit: quick analysis of voltage points and currents in your schematic is showing that 680/68R resistors are correct

what is a way of driving the preamp : bal in/bal out or ..... ?
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Old 5th September 2016, 07:41 PM   #3
tonimxp is offline tonimxp  Italy
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Thanks ALEX i'm absolutly sure that all resistors value are ok.
Tests are made with in and out unbalanced mode.
I will try again to playing change resistors value.
Thanks.
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Old 5th September 2016, 07:49 PM   #4
Zen Mod is offline Zen Mod  Serbia
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please confirm - with SE input , I hope you grounded neg. input ?
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Old 5th September 2016, 08:20 PM   #5
tonimxp is offline tonimxp  Italy
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yes according with schematic I have shorted -IN ( right side ) and -OUT ( left side ) to gnd.
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Old 5th September 2016, 09:16 PM   #6
Zen Mod is offline Zen Mod  Serbia
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if you're keen of connecting output to gnd at all , then ground positive output , not negative

so , try it like this (using SE Input):

1. IN- grounded , none output grounded , use whichever OUT you want as SE hot

2. IN- grounded , OUT+ grounded , use OUT- as SE hot

choose which way you like more , and inform us what is gain in both cases

..... for now , only worse thing you didn't tried , is grounding all inputs and all outputs
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Old 6th September 2016, 11:26 AM   #7
tonimxp is offline tonimxp  Italy
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Hi the picture show :
Righ channel= IN- grounded , OUT+ grounded , used OUT- as SE hot
Left channel= IN- grounded , OUT - grounded , used OUT+ as SE hot
In both cases, if not short-circuit the pole consideration not used to exit (out + or -out) depends on the case mentioned above, the exit used accordingly becomes slightly more low.
I tried with 1,957 Vin and 4,242 Vout so the gain is 2.16.
Tried also by taking the + and - poles simultaneously same result gain.
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File Type: jpg IMG_20160906_130229.jpg (302.3 KB, 33 views)
File Type: jpg IMG_20160906_130252.jpg (293.8 KB, 27 views)

Last edited by tonimxp; 6th September 2016 at 11:33 AM.
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Old 6th September 2016, 01:41 PM   #8
tonimxp is offline tonimxp  Italy
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Tried r5 68//27 and no more gain
Tried short r16 4,7k and gain up only from 2,16 to 2,96
tried r17 47k//47k and gain down from 2,16 to 1,95
I can not figure out how to get more gain in this preamplifier!

Last edited by tonimxp; 6th September 2016 at 02:00 PM.
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Old 6th September 2016, 02:14 PM   #9
tonimxp is offline tonimxp  Italy
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I think i have to replace r17 with one more value for more gain i think 470k, what do you think?

Any advice is welcome,thanks.

Antonio
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Old 6th September 2016, 04:36 PM   #10
Zen Mod is offline Zen Mod  Serbia
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yes , you can try that , for test

you're using 5K volume on output ?

gain measured without any other load on output ?
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