HEllo guys, me again..

Like a subject says, please give me advice with schematics for guitar power amp with lm3886 (because i have one), and a power supply which power up this chip to throw ~20-25watt output.. For practice amp needs surely..

Again Thanks in advance.

Mladen

That`s all i wanted to hear (read).. I do not touch anything, promise!

But, i wanna try to make Amp camp amp for guitar purpose... PhabbTone in front of Nelson Pass project.. Guess what confusing me.. How to add current feedback in this topology? I saw some of ideas which may solve my questions, but i trust only to you guys..  :tu: Thanks all of you for your patience and good will to help me..

Here is a schematic for Nelson Pass ACA amp, and info link...

http://www.diyaudio.com/forums/diyaudio-com-articles/214808-amp-camp-amp-1-a.html

Perfectly clear! As always J M Fahey.. But, how can i mod my power amp to have straight current feedback?

I am also in consideration to build lm3886 with current feedback.. :/ Of course, guitar amp... Do you, or some of you, have some simple circuit for my need?

Thanks guys...

  I hope that some of you guru`s, specialy you, J M Fahey, have solution, but my "My ships had sunk".. Firstly when i saw this post: http://www.diystompboxes.com/smfforum/index.php?topic=81956.msg679661#msg679661 hope is born... but apparently in vain... Write me something.. Is it straight or mixed feedback in my Hitachi power stage? Thanks for your answer and help, also all of you guys are awesome!

Something like this?

This schematic is from Sessionette Rockette 30 amp, and you will recognize standard Hitachi power amp design.... With wholehearted help from J M Fahey, i add current-feedback to PA which is drawn on picture.. But, i want to add Presence to control CF...

Help me to do that...
Thanks in advance!

Quote from: phatt on April 25, 2015, 07:38:10 AM
You could always do what I did!
Build an external tone box,, and just leave the existing one alone.  8|

I plan that , because when i direct input guitar to return in, no hiss at all... thus all hiss is generated through preamp...  And external tone box will be bingo.. PhAbbTone with volume pot direct in return? And i will have clean amp..

Quote from: phatt on April 25, 2015, 07:38:10 AM
An option;
Dave Reeves Hiwatt tone control is by far the best at mid control. :tu:

If Hiwatt control contain Fenderish character?

Quote from: phatt on April 25, 2015, 07:38:10 AM
The mod you mentioned, the leg from Neg input of U1 with the 220n and 47k leg to ground looks good on sims. That returns all the bottom end, though the gain does go UP quite a bit so that may cause issues if circuit noise is already a problem.

Seems like Session preamp suffer noise problem because of sparkle characteristic and good response? :/ Or reason is not great topology... If that is true, another one reason for PhAbbTone..

Quote from: phatt on April 25, 2015, 07:38:10 AM
If you want my take on Dave Reeves HiWatt tone circuit it's here somewhere,, just search for PhAbbTone Ver 3.5
I may have an updated schematic coming soon as some noise still gets in as these hi z circuits are all prone to picking up noise.

If i understand, you have greater version than 3.5? I will wait for that.. Less noise, more want..

I apologize if I repeat, but ran into this schematic. My question is whether this is possible and enforceable in practice ...

Even if it might serve as a guitar power amp ...

JMFahey last year helped me (if he remembers that ) to add current-feedback to classically designed Hitachi mosfet power amp with current resistor, but this with lm317 regulators is new to me...

http://www.current-drive.info/projects/45

All your advice helped me a lot and a lot of them I learned .. As it was obviously that i not enough professional use LTspice ...  :loco

Thanks Roly for that observation...

Let me explain you what is my aim... Session Rockette 30 amp which i have is tonally very similar to fender amps.. Only reason for why i want to add original fender tone stack is because i want to controll mid range... I could instead 6K8 resistor put 10k potentiometre... But while modify TS circuitry, let's do a complete mod..

Phatt, You are totally right, the rockette 30 is the subject of topic. I read all posts pointing to Jungle Jim`s hiss problem, and also share that issue with him... BUT, i found some interesting sentences, maybe problem related, on some other forum:

Quote:
I 'warmed up' my Rockette quite a bit by replacing a resistor and a capacitor in the input-circuit just before the first op-amp (allowing more high frequencies to flow to ground before getting amplified). I'm guessing Stewart Ward does a similar thing when he talks about taming the treble of the amp. Very simple and effective mod that will only cost you half a pound in parts. But you have to be able to read a schematic (they are on the Award-Session website) and locate the parts on the print, de-solder the old parts and solder the new parts in. It didn't take me more then 30 minutes though and I am very pleased with the result: a fuller tone and no more overly-bright trebles. But this has nothing to do with the RetroTone mod, as that concerns the power-amp and negative feedback circuit, 'current feedback' Stewart calls it.

And another one quote:
Look at the first op-amp after the input. There's a 100k resistor and a 10nF cap in series. I changed those to 47k and 220nF and liked the result a lot! (Got this from a Sessionette 75 user.) After that mod you can cleary hear that now it's the reverb that adds some hi-freq 'hiss' or 'sizzle' and not anymore the pre-amp.

End of quotes.

I have no problem with hiss, nor with tone, but think the desired fender tone stack could improve this little amp, which have very good response, transparent sound, etc... I understand that wrong or bad topology with perfect tone stack mean nothing...

I understand that, but what the impact will be on the response curves when I add a Fender tone stack instead of the existing one, when i have only a few hundred ohms of output impendance after inbut buffer, but before tone stack.. I ask this, because simulation of that situation drasticaly changes response curves..

Thank you! Now it is much clearer.

My intentions is to add origin Fender tone stack, with mid pot, like that on first attachment and from TSC... Current tone stack have similar frequency response like Fender TS, i am aware of that situation after simulated it via LTSpice, but i want control of middle frequencies.. And what confusing me... Zsrc of Fender TS is 38K... Do I have to achieve this value, as with, let say 200ohm of Zsrc, i get a totally different frequency graph in LTSpice?

I was comparing in LTSpice this two tone stack, but with Zsrc of 38K, and were very similar, almost identical graphs ..

Hello friends,

I want to modify tone stack from preamp, and need output impedance value from marked point to simulate new one (tone stack) through LTSpice.. How to do that?

Thanks in advance!

Thanks for that advice!

Is this similar to treble bypass capacitor things like many players done on guitar volume pots?
I mean boosting treble on lower volume? Or am i wrong?

Will do what you recommended to me and i will post results!

Basically, i just want to get as close as possible the sound similar to a twin reverb...  <3) (known aim for many people ) Especially from this link.. https://www.youtube.com/watch?v=fFklegm91RI I hope you see that eq settings.. Treble on 5... Sidekick treble on 5 is like -10 treble on Twin, that do not exist!

Thanks again J M Fahey!

EDIT: Just found exact example how my Sidekick sound.. To mention, Treble is on 10, and Presence also on max on this clip.. https://www.youtube.com/watch?v=5uIJq9THm1A

"Bland" sound solved with Celestion G12L-40.. Right from Session Rockette 30... Nice little custom speaker, and to me, sound like have increased sensitivity in dB, despite small magnet... This mod give me well defined all around sound.. BUT , still have a lack of treble, what i think is uncharacteristic for fender amps... Neither Presence pot brings highs... Maybe some of Jensen speaker? C12Q?