some more gain
Hi,
i just build this pre for my F5.
But i need some more gain, say -6db
which resistors have to be changed? - without sonic decrease...🙂
or is there a good sounding pre schematic) with slightly more gain
thanks a lot
Hi,
i just build this pre for my F5.
But i need some more gain, say -6db
which resistors have to be changed? - without sonic decrease...🙂
or is there a good sounding pre schematic) with slightly more gain
thanks a lot
Years old thread.... But has as a snappy title!.. search friendly.
Want to thank Juma for all the schematic's and information, simple circuits with good explanations.
I was looking around today because I need some gain, mostly use computers for source and many amps just don't put out much with a .5vac signal, its not enough. found this and made it.
Looked at many others but settled on this one to try out. Its going infront of a Pre with Jfet inputs.
My 2SK170 are 9.2 IDSS, so changed 33R CCS resistors to 51R to lower current, its now 6.4ma each with +-18V supply's so 70% ..... thinking of going to 43R to get that a bit higher
Sig gen has a bit of noise, need new cable for it. But the wave is nice and sharp. used a 39K load resistor.
Not possible with this circuit without heavy modification - upsidedown BA2 style.
Easiest way would be to add a transformer (in auto configuration) ie. Jenson JT123 or something similar.
Hello Juma,
Here is a version of pcb for your pre as per post 53.
I have included pot (RK09L-alps japan) and input cap (5mm pitch poly).
I have included the psu on the pcb itself. Is it ok? I have connected all input side grounds with a copper pour and made a star of output ground, psu ground (regulator) and input ground.
regards
prasi
i have tried to make it visually simple. viewed from component side.
Here is a version of pcb for your pre as per post 53.
I have included pot (RK09L-alps japan) and input cap (5mm pitch poly).
I have included the psu on the pcb itself. Is it ok? I have connected all input side grounds with a copper pour and made a star of output ground, psu ground (regulator) and input ground.
regards
prasi
i have tried to make it visually simple. viewed from component side.
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Sure it is OK but I think those JFETs would be better used in this circuit :
https://www.diyaudio.com/forums/showthread.php?p=4254886
post nr. 485
https://www.diyaudio.com/forums/showthread.php?p=4254886
post nr. 485
Hi,
I have amplifier with Zin=47kohm and need increase the level of input RCA signal from 1V RMS to 2V RMS Could I use the circuit from #53 and adjust R9,8 to reach appropriate gain? If this is bad idea and there are better options could you please recommend me another circuit based on jfet in input? Thanks in advance,
bern
I have amplifier with Zin=47kohm and need increase the level of input RCA signal from 1V RMS to 2V RMS Could I use the circuit from #53 and adjust R9,8 to reach appropriate gain? If this is bad idea and there are better options could you please recommend me another circuit based on jfet in input? Thanks in advance,
bern
Hi,
I would like to try the schematic from #53
I was looking for BC550C/BC560C bjt transistors but they are difficult to acquire. I thought maybe instead of TO-92 transistors I should try SMD versions (which theoretically should be easier to buy).
What low noise SMD transistors do you recommend instead of BC550C/BC560C?
Thanks, B
I would like to try the schematic from #53
I was looking for BC550C/BC560C bjt transistors but they are difficult to acquire. I thought maybe instead of TO-92 transistors I should try SMD versions (which theoretically should be easier to buy).
What low noise SMD transistors do you recommend instead of BC550C/BC560C?
Thanks, B
I thought they were pretty ubiquitous in Europe...
tme.eu has them and delivers to Poland, I believe.
BC850/860 are the SMD equivalents.
Yes they were. Unfortunately they gone. You can meet the BC550/650 manufactured by CDIL. But I don't know what to think when I read:
BC550/560
Unfortunately there is no Bc560c anymore.
Thanks I will check.
Post #22 here mentions a few places where BC560C can still be found:
https://www.diyaudio.com/forums/gro...c560c-onsemi-fairchild-buy-3.html#post6255625
Please note also that BC550C is still readily available.
https://www.diyaudio.com/forums/gro...c560c-onsemi-fairchild-buy-3.html#post6255625
Please note also that BC550C is still readily available.
I found one of my old prototypes, the all-BJT version of preamp shown in post #53 of this thread and I wanted to hear how does it sound 12 years after. I put it in my preamp-testbed and surprisingly, it's not bad at all - precise and lovely, nice to listen to.
This version has gain of 12dB (4V/V) and swings about 5V RMS max. at output, Zin is about 100k and Zout is a somewhat less than 100 R so it wil drive most amps, not just F5.
The PSU is single 18V (easily obtainable from amp's power rail with 7818 reg) and consumes about 20 mA per channel (about 15 mA through Q3/Q4).
There's a dual power supply version too but the DC offset volatility at the output demands a coupling cap or DC servo so why bother... I put 10uF SILMIC II on the output and forget about it - if you'll use it just for F5, 1uF at the output is enough and you can lose R11 in that case.
Of course, BC550C/560C are not easily available any more in some parts of the world but SMD replacements (BC847c-850c/857c-860c) are sold everywhere. Just take care about SOA of SMD parts - don't run more than 10 mA through Q3/Q4 (make R16/R17 lower, say 6k8 or so...) meaning that you shouldn't have more than 39 mV across R14/R15 with SMD transistors. Since these parts are very cheap buy your self a stash so you can easily match them - mine are hfe=600. 5% match is OK (Q1 to Q2 and Q3 to Q4)
This version has gain of 12dB (4V/V) and swings about 5V RMS max. at output, Zin is about 100k and Zout is a somewhat less than 100 R so it wil drive most amps, not just F5.
The PSU is single 18V (easily obtainable from amp's power rail with 7818 reg) and consumes about 20 mA per channel (about 15 mA through Q3/Q4).
There's a dual power supply version too but the DC offset volatility at the output demands a coupling cap or DC servo so why bother... I put 10uF SILMIC II on the output and forget about it - if you'll use it just for F5, 1uF at the output is enough and you can lose R11 in that case.
Of course, BC550C/560C are not easily available any more in some parts of the world but SMD replacements (BC847c-850c/857c-860c) are sold everywhere. Just take care about SOA of SMD parts - don't run more than 10 mA through Q3/Q4 (make R16/R17 lower, say 6k8 or so...) meaning that you shouldn't have more than 39 mV across R14/R15 with SMD transistors. Since these parts are very cheap buy your self a stash so you can easily match them - mine are hfe=600. 5% match is OK (Q1 to Q2 and Q3 to Q4)
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How about PSRR ?
Incidentally, both BC32740 and BC33740 are active and on stock az Mouser.
No mention of NRND.
Cheers,
Patrick
Incidentally, both BC32740 and BC33740 are active and on stock az Mouser.
No mention of NRND.
Cheers,
Patrick
PSRR is not great so the clean power supply is needed.
With PS filtering as shown above the noise is not detectable even with very sensitive speaker.
BC327-40/337-40 could be good candidates for Q3,4
With PS filtering as shown above the noise is not detectable even with very sensitive speaker.
BC327-40/337-40 could be good candidates for Q3,4
If high hfe is more important than noise, then there are also plenty of BC549C / BC559C available at Mouser.
Cheers,
Patrick
Cheers,
Patrick
The Onsemi datasheet gives the same typ. noise figures for BC549/BC550 and BC559/BC560, only the max value is larger for BC559?