SNAKEYE Pre-amp+amp.

[deadastronaut]

Preamp, active EQ, send+return, pre out, speaker out (1 watt amp) and DI out.

a one off project for my son in law....its pretty cool,

thanks to samhay for his help. cheers man. 

build files,

https://dl.dropboxusercontent.com/u/7464107/paolosamp1.pdf

https://dl.dropboxusercontent.com/u/7464107/paolostracepcb.pdf

schematic:

[samhay]

Nicely done Rob. Looks like you didn't have any issues with the etch.
Are you going to do a demo video?

And somebody will eventually ask for gutshots...

[deadastronaut]

cheers sam, yeah it works as planned..nice one.

i nearly got him to have it in a 1590DD which would 've been a squeeze still, but possible..
but he settled on using a rack which gave me more room to move..(but more hassle to etch)

yeah guts already been demanded... ...if i get the urge, i'll pop the lid off later,
its just that the rack came as flat pack so its more than 4 screws to do..

i may do a quickie vid later, am having a well deserved /celebratory no debugging whatsoever
beer/whiskey now..

[Kipper4]

Good work DA.
love it cant wait to hear a sample.
Thanks for sharing
Rich

[dbp512]

Could you explain why the fx loop bypasses the tone stack?

[Hatredman]

Could you explain why the fx loop bypasses the tone stack?

And a separate stage for the mids?

[deadastronaut]

hi guys,

loop was as requested,

mids, you'll have to ask brian wampler on that.

anyway, it all works as planned and sounds damn good, plenty of tonal range,

however i have one issue before i give it to my son in law..

when powering on and off i'm getting a huge thump.??

this is how the switch is wired...( added a power/standby led.) as requested.



thoughts?. remedies?..cheers guys..

[slacker]

Do you mean a thump through the speaker? If so you could try and add a big cap in parallel with R34, that way when you turn it on the volume is turned down and comes up slowly as the cap charges up.

[deadastronaut]

Hi ian,

its thumping on power up and down, on xlr, pre out too,

i,ll rig up an old spare speaker and see if its doing it on that ....

cheers man,

[J0K3RX]

Nice Rob!  I see a lot of familiar stuff in there!  Question... is this a clean preamp/amp? If so, what is the 80's/Metal switch for?

The thump sound... From looking at the data sheet for the TDA7052A it has DC volume control on pin 4, right? Why the 82k to ground? Why not a 1u cap in parallel with a 1M resistor?

[deadastronaut]

Hi jim,  the tone switch just gives it more range...especially with distortions in it..

yes, its a very clean amp. The 82k sets the max gain, at 100k it had a littlr breakup on max vol, so i put 82k
as.i/he wanted it uber clean...

cheers man.

[deadastronaut]

Just tried the speaker out, and that is ok, just a tiny pop when powering on/off

but xlr/preout thump...hmmmm....


i put a 1000uf in parallel with the dc in,  to the bottom right of the switch, this has stopped the thump when turning off....but not on..

[slacker]

Try moving the 1000uF to after R1 so in parallel with or replacing C1, or leave it where it is and put another series resistor between it and the switch. Either of those might help slow down how fast the voltage comes up reducing the thump.

[deadastronaut]

Try moving the 1000uF to after R1 so in parallel with or replacing C1,  (tried that to no avail)


or leave it where it is and put another series resistor between it and the switch. Either of those might help slow down how fast the voltage comes up reducing the thump.

so put another resistor from switch to 9v pcb in?..yes.

cheers man.

[slacker]

Yeah, resistor from switch to PCB 9V, big arsed cap from PCB 9V to ground.

[samhay]

Rob - I think you tried a 1000u after R1 yesterday to no avail?
The problem with adding more series resistance to V+ is that you will lose more voltage headroom. With the power amp driving a speaker, how much does the voltage sag already?

[deadastronaut]

cheers ian, i'll give that go....big arsed cap coming shortly . 


: i just put the 1000uf :

+bottom right switch , and - to middle left on switch,

turning off...nice, turning on...more of a pop than a huge thump...better, but not cured...hmmm

but i'll try your suggestion, ive just been reading about power switch ''thumps'' seems very common
and not any remedies as far as i could tell....anyway, back in a bit. 

[deadastronaut]

Rob - I think you tried a 1000u after R1 yesterday to no avail?
The problem with adding more series resistance to V+ is that you will lose more voltage headroom. With the power amp driving a speaker, how much does the voltage sag already?

yeah i tried that yesterday..

i currently have 7.28v on the actual amp...hmmm...i can always remove the 100r before the amp pin 1 though to get 8.16v...?.

edit: jumping that 100r, much better amp, ( unecessary resistor)

the amp doesn't pop/thump at all,

just the xlr/pre outs..

[deadastronaut]

ok, i have to give this to my son in law tomorrow, wont be seeing him for a while etc..

he will just have to turn his mixer down when turning on..(as i would anyway.)

any pop on amp speaker is negligable anyway. so any speaker will be fine..

note to any builders : remove/jump R33

cheers guys.

meanwhile i'd still be interested in any cures for ''thump'' for future reference..

[deadastronaut]

did a quikie video demo...before it goes..