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Messages - weatherlght

#1
Amplifier Discussion / Re: On/Off Pop Noise Problem
April 27, 2010, 02:29:25 PM
One of my professors told me that its due to power suplly caps charge/discharge transients and that might just be the reason why valve amps dont have that pop. Valve amps have a series resistor / choke in their power supllies since valve amps draw small currents (500-1000mA). Problem is, with a solidstate amp (it draws like 2amps+) any significant resistance that I'll be puting in series to charge the caps slower will reduce some serious volts  :( I'll need to ask around and come up with a solution.
#2
Amplifier Discussion / On/Off Pop Noise Problem
April 26, 2010, 01:22:10 PM
Greetings

I have recently built a 25w tda2050 based amplifier. After double checking all routes and pcb connections, the amp fired up flawlessly the first time. Its clean channel is great, without any hums or hisses. However as I continued using, i noticed that the on/off popping sounds were somewhat much more than tolerable and it may not be safe for the speaker even. The pops are loud and when turning off the amp, after the initial loud pop, 2-3 secs later a silent crackling, tearing sound comes off the speaker too! :( I tried to do a we search but I could not find some confirmed reliable basic practical information. Theres supposedly a circuit to prevent this pop in audio amps but best solutions are the simple ones so I would really appriciate if you can point me in the right direction :)

My build is TDA2050 datasheet with a 10uF nonpolar feedback capacitor instead of the 22uF shown at datasheet. Rest is pretty much the same. It does nto have any hum, hiss or oscillation. It runs pretty smooth and quiet only problem is this popping at turn on/off. For power suplly, I use a 35A bridge rectifier, a 15-0-15 tranny and 4700uF filter caps with one additional 100nF ceramic between the +vcc and -vee capacitor tabs. My star ground is right between the power suplly caps and tda2050 (about 2 inches away from both). My star has a direct connection to mains earth and chasis ground goes directly to mains earth as well. My preamp is a marshall mg15 with a suplly of +-15V zener diodes with 220uF and 100nF caps connected with 680R resistors to power suplly. At around 1w output, my measured dc voltages are +-14.9V at preamp and +21.5V, -21.7V (cheap tranny :( ) at powersuplly. This pretty much sums it up as far as I can remember.

There are 3 main things I am concerned about that may cause this pop

- I read some claims that popping is mainly due to arching at on/off switch. Some people suggest a small mains cap at power switch. Can this work? If yes, what type of cap and how to connect it?

- Some guy talked about DC balance. I'm not sure if he meant +21.5V, -21.7V suplly difference or the 22k non inverting to ground dc resistance and 22k inverting to ground (by speaker). Something about DC offset at output. Are these values critical? I used +%5 varying carbon resistors at poweramp. Shall I measure components induvidially and put 2 22k that are pretty much identical down to less than %1 so these 2 22ks are matched?

- I also have a valve amp and theres absulately no audible pop at on/off. It has a kind of slow start (preamp suplly has some 5k resistor + a series choke) Can the timings of preamp and power amp turn on cause this pop? If yes, then shall I delay the preamp, or the power amp by installing some series resistors? I assume the 680R resistors have that purpose but they dont seem to be enough.

Thanks for your help :)
#3
I could not find the 2n5484 mosfets shown at the schematic :( I found a few bf256 which are a replacement for 2n5485 and 2n5486 i believe. Will they work fine for a nice metal distortion sound? Or they will ruin it? What transistor would be best for this DR.Boogy preamp?
#4
Thanks alot  :)
#5
Thank you for the schematic :) This is something that i will definately built. Still i'll also want to build a classic mg10-15 preamp and combine these 2 along with a tda2050 30w poweramp in a 2 channel nice sounding combo amp :)
#6
update, still need an mg10-15 schematic please :)
#7
I forgot how to play the guitar actually due to dealing with all these amps and tubes as well as the school  :( I checked the link you gave me and found some nice schematics, 5010, 5203 and 5213a. 5203 and 5213 have the leds i need for the fat od/ds sound i believe. I just need to figure out a way to simply those circuits as much as I can. Perhaps throw out the fet switches and all those low output impedence emitter follower transistors. Just put a 2 way switch to bypass the ds preamp and directly connect the input to clean preamp. Add a simple 2nd input before the power amp for cd input, and use that circuit of 5010 for the headphone output. I will use simple a tda2051 circuit running at 25-30w instead of the transistor power amp stage of 5010 though. If i can get my hands on a marshall mg10-15, i'll try to implement the fdd as well.

I'll also add a simple pre-out - pwr-in effects loop stuff. Do i really need a emitter follower before the pre-out jack ?
#8
thank you for the info :) however i need to add a few things to this.

-a diode clipping distortion pre-amp (i'm not sure whether the preamp will give distortion without the diodes or the leds),
-a switch to bypass the clipping stage for clean tones
-a headphones output (i believe i can add this to the end of the preamp as an *pre-out jack, then include an *po-in jack and make a simple effects loop. but some amps add that at the end of power amp using some attenuation circuit to lower down the headphones signal voltage :s, i need a simple schematic for it)
-a simple mixer to the power amp input (or preamp clean stage input) just like in marshall mgs, so i can hear the song as i play
#9
Greetings

I'm an electronics student and I have built 2 tube-amps in the past. I like building guitar amps from scratch with its cabinets and everything. I also tried to make an SS amp but the tone wasn't good at all. However I used a few ss pedals and amps which sounded pretty well like behringer od100, marshall mg series. In my ss amp design I used the schematics of a ts-9 combined with a flat response power amp that only produced a nice sound with a GT8 :p .

I know that there is a good preamp circuit out there that can produce can give a nice overdrive/distortion sound (marshall mgs are fine imo, they use leds for clipping), but the problem is I cant find any schematics for such an amp. I tried the TS-9 circuit and it sounded bad (uses diodes for clipping), I traced the circuit of my friends bc-rich bcl12 amp which also sounds terrible. I couldnt get a hold on to a simple marshall (mg10, mg15) Least i could find was 50dfx which is hard to trace with all the effects and such.

I will really appriciate if you can provide me the schematic of a mg10 or 15 cd or any other analog circuit (behringer od100 has digital effects I believe :/ ) that can provide me with a nice fat overdrive/distortion sound for heavy metal, similar to Iron Maiden tones.

Thank you