PUNCH - 1W amplifier

[chptunes]

i see there is a tda7052 a than has a volume lug on the chip as well .

you run the pot from ground to pin 4 . i wonder what the benifit of this design is . oh well , i ordered 5 so i guess i will never know unless i bought the normal ones and a/b'ed em .

Beware.  I also built my Punch with the TDA7052A chip, and some changes are required.  R3 (10k) should be omitted.  The DC Volume (Pin 4) is at full gain with a 1M Resistor to Ground.. 100k is a about half volume, and is a nice fixed level for living room use in my experience.

My Punch project morphed into this:




-Corey

[petey twofinger]

thank you

what is the purpose of the 8 ohm resistor in series with the speaker ?

[chptunes]

thank you

what is the purpose of the 8 ohm resistor in series with the speaker ?

A 16 Ohm load drops the wattage and current, keeping battery power feasable.  This resistor should be rated at 1w or more [I used a 3w resistor].

[tca]

oh well , i ordered 5 so i guess i will never know unless i bought the normal ones and a/b'ed em .

You can do some extra stuff with the TDA7052A like adding a tremolo (http://www.diystompboxes.com/smfforum/index.php?topic=99407.0) The phase shift oscillator of the EA tremolo has the right voltage, see the schematic on the given link.

Cheers.

[chptunes]

Just built a basic Punch circuit for a friend.  Used the TDA7052A chip and A500k DC Volume Potentiometer.  The speaker measures around 1.5" wide by 2.75" long, and is rated for 3w at 8 Ohms.. last time I ordered from Mouser, I threw it in the shopping cart for cheap.

The current draw is 11.6mA at idle [Volume full].. when crashing a G chord, the current draw spikes between 20-25mA.  Battery life should be fine, especially if using an adapter part-time.

It's just a quirky novelty gift for my best bud, really.  Sounds clean, but saturated because of the tiny speaker.  Tiago's Punch circuit stays clean, so it accepts pedals nicely.. I drove this "Snickers Punch" with my AMZ Tweed Stack last night.  Fun high gain crunch at whisper level.  My wife says it's cute and family friendly.









-Corey

[tca]

^ Lovely!

[bluebunny]

+1!

That is a really great example of a re-purposed enclosure.  Nice work.

[petey twofinger]

very nice , and too cute !  my mini noisey cricket is in a tin enclosure something like that . it oscillates like mad with a extra bass fuzz stage in there .

i like the idea of those cheap tin enclosures but man , drilling them is , well i just get very nervous !

i am currently waiting on the 7052a chips to arrive .

[Gurner]

thank you

what is the purpose of the 8 ohm resistor in series with the speaker ?

A 16 Ohm load drops the wattage and current, keeping battery power feasable.  This resistor should be rated at 1w or more [I used a 3w resistor].

wrt battery power, that resistor represents pure inefficient waste ...you're basically converting battery power into heat (disapated across the resistor) ....if you wanna preserve battery power properly - firstly, I'd argue you should simply steer clear of a BTL amp like the TDA7052A -  you'd be far better off just reducing the output signal level into the speaker (e.g. by putting a 1M DC vol pot on pin 4 ...if it's a TDA052A) or using a higher impedance speaker (therefore 16 ohms) or having some other input level control. The worst place to tackle this is inserting resistors on the output legs of the amp. That's akin to driving your car at full revs & then keeping your foot heavily on the brake to keep the speed down.

[chptunes]

very nice , and too cute !  my mini noisey cricket is in a tin enclosure something like that . it oscillates like mad with a extra bass fuzz stage in there .

i like the idea of those cheap tin enclosures but man , drilling them is , well i just get very nervous !

i am currently waiting on the 7052a chips to arrive .

Thanks pal.. Drilling those tins is a little dicey...

Let us know how yours comes out.

[chptunes]

thank you

what is the purpose of the 8 ohm resistor in series with the speaker ?

A 16 Ohm load drops the wattage and current, keeping battery power feasable.  This resistor should be rated at 1w or more [I used a 3w resistor].

wrt battery power, that resistor represents pure inefficient waste ...you're basically converting battery power into heat (disapated across the resistor) ....if you wanna preserve battery power properly - firstly, I'd argue you should simply steer clear of a BTL amp like the TDA7052A -  you'd be far better off just reducing the output signal level into the speaker (e.g. by putting a 1M DC vol pot on pin 4 ...if it's a TDA052A) or using a higher impedance speaker (therefore 16 ohms) or having some other input level control. The worst place to tackle this is inserting resistors on the output legs of the amp. That's akin to driving your car at full revs & then keeping your foot heavily on the brake to keep the speed down.

Thanks Gurner.. I suppose the DC Volume Pin does keep tabs on current draw pretty well.  I'll measure current with and without the resistor...

[deadastronaut]

@corey sweet...literally...

[chromesphere]

I divorced the LM386.  It just didnt work out for us.  I told it that "it wasnt me, it was you" and it began to whine in that harsh trebly tone you may be familar with.

I dont know if i would do this, but i noticed that the TDA7052 has 2 outputs.  Is this to drive 2 speakers?  Is it ok to do this?  Will the output power be 2 x 1/2 watt? (id imagine it would).

Cheers
Paul

[tca]

I dont know if i would do this, but i noticed that the TDA7052 has 2 outputs.  Is this to drive 2 speakers?  Is it ok to do this?  Will the output power be 2 x 1/2 watt? (id imagine it would).

No. The TDA7052 is a BTL (Bridge-tied load) amplifier. The two outputs are for connecting the speaker, only one. Check the datasheet.

tca

[chptunes]

But, it will drive loads from 8 to 16 Ohm just fine.  You could connect two speakers in series or parallel, as long as the total load stays within the correct range.

Two 4 Ohm or 8 Ohm speakers in series would be nice, or two 16 Ohm speakers in parallel.

[tca]

I divorced the LM386. 

You could try its big brother, the LM380. Some examples:
- Mark's miniamp: http://hammer.ampage.org/files/Miniamp.png
- or the Pygmy amp (http://home.comcast.net/~synthdoc/P/1750.pdf), needs a buffer...

Cheers.

[Gurner]

To me, the LM386 sucks wolf's cookies in large order (I can't quite figure out the unbridled lurve for it round these parts....must be the plethora of '10 component circuits' that gets most into it -  indeed every time I see one I think "Everybody was Kung-fu fighting")..

Personally, unless you wanna see your battery sucked dry in short order, for a TDA7052a IMHO it's better to go with a 16 Ohm speaker (or 2 x 8 Ohms speaker in series) ...or even higher.

[chptunes]

To me, the LM386 sucks wolf's cookies in large order (I can't quite figure out the unbridled lurve for it round these parts....must be the plethora of '10 component circuits' that gets most into it -  indeed every time I see one I think "Everybody was Kung-fu fighting")..

Personally, unless you wanna see your battery sucked dry in short order, for a TDA7052a IMHO it's better to go with a 16 Ohm speaker (or 2 x 8 Ohms speaker in series) ...or even higher.

My 'Snickers' Punch (pictured above) draws 11.6mA at full volume (500k on Pin 4, with an 8 Ohm speaker load).. 20-25mA peaks when attacking my guitar.  How long would a fresh Alkaline run at 11.6mA.?..

[Gurner]

My 'Snickers' Punch (pictured above) draws 11.6mA at full volume (500k on Pin 4, with an 8 Ohm speaker load).. 20-25mA peaks when attacking my guitar.  How long would a fresh Alkaline run at 11.6mA.?..

I'd say there's an error in your measurement...the quiescent current of the TDA7052A will be 15mA alone (no sound & no speaker attached - see the datasheet quick reference data - http://www.nxp.com/documents/data_sheet/TDA7052A_AT.pdf ...and that's only at 6V supply) - let alone full volume with a speaker attached.

At 9V supply, with a BTL IC like the TDA7052A, you can potentially squeeze about 15V peak to peak (5.3V RMS) across the load ...& in this situation that's over 700mA running through the speaker ...a 9V alkaline battery would last something like 20 minutes with the amp running full tilt!

[chromesphere]

I divorced the LM386.

You could try its big brother, the LM380. Some examples:
- Mark's miniamp: http://hammer.ampage.org/files/Miniamp.png
- or the Pygmy amp (http://home.comcast.net/~synthdoc/P/1750.pdf), needs a buffer...

Cheers.

But TCA, why would i want to do that when your punch amp looks so much easier
My chips are on the way anyway, thanks for sharing the layout!

EDIT:

No. The TDA7052 is a BTL (Bridge-tied load) amplifier. The two outputs are for connecting the speaker, only one. Check the datasheet.

tca

It was the datasheet that i was looking at, rechecking it, not sure how i even came up with such a stupid question.  Thanks again!
Paul