PUNCH - 1W amplifier

[tca]

It seems you have a short circuit!

Is the output in any way connected to  ground?

[arijit1035]

Sorry for the delay i was busy with some work but here is a pic... i have drawn the connection lines over the image.... the circuit is ugly and confusing by itself. I kept the circuit spacious so that i don't solder anything by mistake cause my soldering i crappy. i taped it afterwards with cello-tape don't know why but i thought it was a good idea.... anyway have a look at it. if the circuit needs to be redone tell me cause i don't have a problem doing it all over... to be fair i enjoyed making it...
https://drive.google.com/file/d/0B_4-Pn2YOUu5UU1KTVBkTWYzZlE/view?usp=sharing

[arijit1035]

i cant make out if the output is connected to ground i posted a pic of the circuit please tell me if anything is wrong with the layout.

[tca]

Are you sure that your IC is the TDA7052? Not the TDA7052A? (Can't tell from the image you posted.)

[arijit1035]

the id on the chip says tda 7052 N44270 HnH5011

[arijit1035]

Hey i checked the output connection looks like i did solder the + of the batt with the audio out. After correting this it started working fine but there is a cracking hum in the background. May be the polarised 1u cap isnt working well should i replace it with a non polarised cap? Thank you for all your help till now.

[dwietzel]

I have built a tonemender to put in front of my PUNCH amp. It is driving the PUNCH way to hard and need to see what the best way is to match these two circuits as best as possible. You can get the schematic from the zip file placed here. Any help would be extremely appreciated.

http://www.distinctiveturnings.com/vickaudio/FreeGuitarPCB/index.php/tested-pcbs/run-groove-tonemender/

[tca]

Welcome!

The tonemender has a drive pot (500k), use it. Replace it with a 100k pot to reduce the  max gain available. If you don't want to mess the tonemender just add a100k pot/trim (voltage divider) at the output and adjust to taste.

I would reduce to 500k to a smaller value.

Cheers.

[dwietzel]

Someone else replaced the A500K pot with a 22K fixed resistor which would give unity gain ( would be fine for what I am trying to do).

http://blackoutelectronics.com/wordpress/?p=431

If I wanted to use this instead of the trimmer, can you advise what pins would be connected by the resistor? Any other jumpers needed for the other pin(s)?

Thanks,
Dave

[Stan87]

Hello, everyone!

I'm an absolute beginner and want to build the Punch as my first amp. My problem is not new here - local stores don't have MPF102.
They actually don't have many JFETs at all.
I've read that J201 is not compatible for this build (they don't have it anyway).
I hoped to use 2SK117 instead - it has Ig = 10mA, just like MPF102

What parameters I should look at when choosing a JFET?

They also have those n-channel field transistors:
2SK212F
2SK246
2SK301
BF862
MMBFJ201
MMBFJ310

I don't really care about form, just want it to work...

Thank you for help!

[PRR]

That MMBFJ201 *IS* your J201, except with little teeny legs. Physically awkward but electrically right.

[Stan87]

Thank you, PRR! Too bad J201 is not suitable for this build. 
I chose MMBFJ310. It looked the most close to MPF102. I made a conclusion (because of this https://www.physicsforums.com/threads/confusion-regarding-pinch-off-voltage-in-a-jfet.734222/), that the important parameter described in this message:

^ The J201 has -.8V pinch voltage... this is to low if you put a booster, or something that amplifies the signal, in front of it. The MPF102 has a -3V pinch voltage. The J201 is the cause of the distortion.

...is V_GS(OFF). But J201 actually has V_GS(OFF)=-0.3 ~ -1.5 V and MPF102 has V_GS(OFF)=-8.0V
Also, in this message

^ The 2n5484 will work nicely.

The + of the 1uF cap goes into the TDA7052 input.

Cheers.

...recommends 2n5484. But it has V_GS(OFF)=-0.3 ~ -3.0 V. Not much more than J201.
So, it's still unclear why some FETs would work fine and others wont.


Anyway, my built succeed! It works! Of course, it were a pile of troubles.
First, the store had TDA7052 on paper, but actually they only had TDA7052A, so I was forced to buy additional 1M Ohm pot, which cost me almost the price of whole initial build.
Second, I knew MMBFJ310 is SMD, but I wasn't ready it's SO small! Anyway, I made a tiny "board" for it to not screw it and it worked out.
Finally, when I soldered everything together, it simply didn't work. Thanks to Corey aka chptunes, who pointed out that R3 should be omitted. When I removed it - the amp started working!

Only, the bright white noise in on the background. Isn't there some way to reduce it without cutting the volume? 

[deadastronaut]

hi guys,

a friend wants a little 'clean' amp so i thought of the punch as it seems like an ideal candidate...

the thing is, i'm using the TDA7052a. so i have the vol pot on pin 4 to ground etc...

heres the issue, i have it breadboarded as per scheme page 1. (+ vol pot)

ive tried a 4ohm 6'' speaker and an 8 ohm 6'' speaker... on pins 5/8 but its distorted as hell..

and the weird thing is  when i turn the vol the speaker/s suck in and out...without even playing

e.g i can control the speaker suck n blow with the pot.....weird

am i missing something here?..

(is this amp ok with humbuckers?) or only for fender heads

EDIT: after reading this thread, it seems i have exactly the same isue as 'shrike' did in his video....

thump thump thump...too
http://www.diystompboxes.com/smfforum/index.php?topic=99271.msg989200#msg989200

dodgy ic's ?..

[tca]

The schem on page 1 does not work for the TDA7052a... you will need a cap. Check p. 8 of the data sheet.

http://www.nxp.com/documents/data_sheet/TDA7052A_AT.pdf

Cheers.

[tca]

Something like this: http://www.diystompboxes.com/smfforum/index.php?topic=99271.msg894794#msg894794
Cheers.

[deadastronaut]

Ahh i see.. cheers tiago..i'll give that a go then. nice one...

i just ordered a TDA2627A for fun, they look pretty cool too..

[deadastronaut]

brilliant...got it going.

cheers man..

edit: wow i'm quite impressed...

after a tinker around with guitar with a naked unboxed 6'' speaker, it sounded pretty cool..

i even put my 5 string bass on it for a laugh...and it handles it with no distorting etc...and at a pleasant level..

very cool...be a nice sound when boxed.. nice one tiago..

i'll give it a proper test in the morning,..

[deadastronaut]

Lol...i had this amp running on a 9v solar panel only....worked great....till the clouds came over ha ha..

[Luke51411]

Lol...i had this amp running on a 9v solar panel only....worked great....till the clouds came over ha ha..

Nice! Sounds like a commercial product to me. "battery free portable amp with tube saturation and natural sag upon first cloud cover"

[duck_arse]

rather dark-sounding, would you say, DA (the other)?