Juma's Head Amp

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#401
Hiss from your source is common. If you have no hiss when not playing it's not the head amps problem. Prasi has good suggestion but CD players use op amps as drivers and they will have hiss typically (unless high end one). Surprisingly, your iPhone is rather quiet as a source when cellular device and Bluetooth are turned off.

Good DACs with good regulated PSU are also quiet.
 
#405
ammel68 said:
So now op-amps are noisy and cause hiss??

Typically if they're used as buffers(or drivers as you call them) in a CD player or other device, their gain is around 1 and not a source of hiss.
Click to expand...

My old Phillips CD player is not dead silent when not playing. Although I use headphone output as a preamp to control volume. Whereas my external DAC is silent.

I'm sure not all CD players have hiss.
 
#407
xrk- 1 set (1 PSU+1 Stereo HA)+2 buffer-shipped
gannaji- 1 set (1 PSU+1 Stereo HA)
saheb- 1 set (1 PSU+1 Stereo HA+2 buffer)
kram- 1 set (1 PSU+1 Stereo HA)-shipped
btesize-1 set (1 PSU+1 Stereo HA)
rumina-1 set (1 PSU+1 Stereo HA)- shipped
nicusim-1 set (1 PSU+1 Stereo HA)- shipped
potepuh-1 set (1 PSU+1 Stereo HA)- shipped
e_fortier-2 PSU +1 Stereo HA+2 buffer-shipped
touchdown -1 Stereo HA-shipped
albertNL- 1 set (1 PSU+1 Stereo HA) shipped
Malvin - 1 set (1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA)-shipped
one more member through PM-1set(1 PSU+1 Stereo HA+2buffer)-shipped
Thanks
Prasi

 
#410
Thanks all,

Sorry about the delay, looks like the source is the issue for the hiss, with a CD player everything is fine...I have 2 of these IQAudio Dac+ each powered by a very well filtered PSU, I'll have to look at the Alsamixer setting in Volumio.

BR,
Eric
 
#412
Well, I have great news 😀

I went into Alsamixer and was able to lower the overall Playback Digital Gain (Master software volume) by 4dB and I also disabled the Playback Boost (1dB) so the overall gain was lowered by 5dB, guess what...regardless of where my volume setting is via my app there is no more noise..hiss..awesome !! Finally I can enjoy the music without any background noise.

I'll wait a few hours in order for break-in but so far the Juma HA is a keeper, thanks all.

BR,
Eric
 
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#413
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#415
e_fortier said:
I went into Alsamixer and was able to lower the overall Playback Digital Gain (Master software volume) by 4dB and I also disabled the Playback Boost (1dB) so the overall gain was lowered by 5dB, guess what...regardless of where my volume setting is via my app there is no more noise..hiss..awesome !! Finally I can enjoy the music without any background noise.
Click to expand...

My greatest fear in computer audio: the absolute need to fiddle with settings and get problems in return. Then suspecting well working devices to be at fault....
 
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#417
Hi Saheb
I would think that a build guide would be ideal, but for such a simple HA would not be justified. Read the bits and pieces of info posted by Juma and others in this thread and you would have an excellent build.
matching of i/p pair would be sufficient i would guess, but i doubt one could have that many pnp/npn trannies of various grades.
just adjust your build for near zero offset and 50-100mA of bias, you shall enjoy music (would be my bet). too busy with other priorities right now, sorry!
i have posted a bom some posts ago, do have a look.
 
#418
prasi said:
Hi Saheb
I would think that a build guide would be ideal, but for such a simple HA would not be justified. Read the bits and pieces of info posted by Juma and others in this thread and you would have an excellent build.
matching of i/p pair would be sufficient i would guess, but i doubt one could have that many pnp/npn trannies of various grades.
just adjust your build for near zero offset and 50-100mA of bias, you shall enjoy music (would be my bet). too busy with other priorities right now, sorry!
i have posted a bom some posts ago, do have a look.
Click to expand...
Thanks,
I have downloaded bom's from previous posts. I shall try to get the i/p pair matching happen.
I have been following the thread, let me get the pcb's then will try the build.
So +/- 15V with 100ma bias. So a 12-0-12 1amp Traffo will do I guess?

Sent from my A0001 using Tapatalk
 
#419
You want a 15vac trafo so that you have room to use a voltage regulator or a cap multiplier to smooth the ripples. Cannot use un-regulated power supply with simple CRC filtering unless you like hum. 7815/7915 regs work well enough but they need about 18-19v to work. A MOSFET cap Mx needs 4v above 15v. Need a 25VA trafo minimum. The 10VA ones are too small as this burns off about 6w at idle.
 
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