Have somebody used TDA1554?

[white_devil]

Hello, i'm kind of noob and i'm trying to use a TDA1554 2x22W power amp that i built (working and using it ), i thought it was enought with connecting a guitar preAmp for the amp input, but i guess that isnt enought because it works but with really low gain :S i mean with other stuffs (tv for example) work really great, but with my guitar sound very low, i think the problem is that the preAmp is giving too low gaing but i'm not very sure...


Any suggestion???

Thanks

[Threefish]

What sort of preamp you using? If the TDA1554 amplifies well with a TV, which would already have a fairly strong output signal, but not your guitar preamp, it sounds like you need a preamp with more gain.
I was just looking at the data sheet, and it says it is used primarily for car radios, which means low voltage but potentially high current draw. Is your power supply up to high current draw? (though if this was the case I would guess that you would get some sort of oscillation or motorboating, not low output). There are other chips like this (TDA2005, TDA1562) used in car radio applications, and I know they require ~12v and up to 4A or more current.
Wow!!! 17 pins on that ic!!! Have you rigged it up on vero, or a pcb??

[white_devil]

Yeah, i now it have a high current i have a 6 amp power supply and the IC need 5 so thats not the problem and i think i need more gain too but i just dont have a schematic of a higher gain one, i have this preAmp:

http://www.harmony-central.com/Guitar/Faqs/faq/faq.buildPreamp.txt <-- the 3rd that said:

"From: nm1@ukc.ac.uk (N.McBride)
Newsgroups: alt.guitar
Subject: Guitar-to-hifi box
Date: 30 Nov 92 10:55:13 GMT
Organization: Computing Lab, University of Kent at Canterbury, UK"

And it works but too low :S

And yes i have it on pcb and its nice, i have a Mmm (sorry i dont know the name in english, but the piece of metal u put on IC for heating prevention) , what can i try please?? another preAmp? or do i need something else?

Thank you

Oh oh and btw i tested it with my homemade distortion (MXR Dist+) at highest volumen and it sounded a lot higher , so i think definitly its preAmp..

Any tip, and Thanks Threefish 

[white_devil]

Anyone please? i need it...

Thanks

[RDV]

Add in one of these between your preamp and amp and you will be louder. If you use the BMP one, you'll want to leave off the volume control at the end.




RDV

[Threefish]

Just had a look at that link. If I read you rightly, you used the third schematic shown, based on the 741 op amp. What value did you use for R4? It says the starter value of 100k gives you a gain of 2. That's nothing in terms of guitar preamp gain, so I can understand if you get low volume output. I'd try to sub in an 11k or 3.3k for gains of 10 or 30 respectively, as the notes say. You'll probably get some sort of distortion or other change in sound as you increase the gain. Maybe put a socket (half of an 8-pin ic socket works for me) where R4 is so you can quickly change resistors, and hear the change in gain/volume. You could probably put a pot there as well, but that's getting more complex.....
RDV's suggestions are good. If you want to tack something on the end of what you've already got, these are your simplest option.
There are many other circuit options out there that you can use as a preamp. Follow the links from this site to www.runoffgroove for the Fetzer Valve, and look at their other circuits which could be used for a more distorted/overdriven preamp. An LPB1 (or 2) or mosfet booster (find these at www.generalguitargadgets.com) could be used too, though they're really better for volume increase, and not for adding that preamp sort-of grit that guitar preamps tend to have to some degree. 
Or if you're feeling adventurous, look at the great work RDV, R.G. and co. have been doing on a Vox preamp : http://www.diystompboxes.com/smfforum/index.php?topic=37049.0
this looks awesome, and sounds good. It'll be my next preamp build.

[white_devil]

Hey!! u r guys awsome, thx, for being honest i dont know what a "gain of 2" means but i believe its low (yes, i'm using the 100k resistor) so i'll check those sites (thx Threefish ) and lots of thx RDV :D i'll try that too, excellent , now  i have a better idea about the problem, thank you guys really much, ohh and btw Threefish, i cannot use valve base preamp because i'm from Dominican Republic and here's reaaaaaaaaaaaally a trouble to get some valve (or any:P) that's why i decided doing a IC chip based

But thxxx guys i'm truthly happy for your answers :D:D

Thank you really REALLY much :D

[white_devil]

Well i tested the preAmp, just doing the conection PreAmp<=>Speakers (to "hear" the gain) and its "audiable", i mean it can b heared (low but can ) and i changed the R4 for a 220 Ohm resistor i have in here (just for testing purpose) and get higher!!! but distorted :S :S but its ok, i just want to test and i'll test all the possible solutions specially the RDV one.

I also changed the speaker for another one (my stereo system speaker ) and sound higher!!! so now i'm kind of confuse if speakers can cause any change on the preAmp or Amp gain.. BTW the speakers i'm using r very strange and weird :S its a soundBarrier with a transformer on input so i'm not sure about how it works cuz i have lots of inputs hehe like 6 i guess.. in the electronic store they told me "just take the red and black" and that's what i'm doing but with a "normal" speaker sound higher Mm.. anyone know how this speakers work ??  and if i just need red and black why do they have so much inputs for the transformer.. Thanks,  and i'm sorry about asking so much , its that i'm just a newbie..

Thank you very much and by the way, the transformer i talk about its like this:

http://www.twacomm.com/catalog/model_T725.htm

but solded to the speaker input and for 20W (sorry, i couldnt find a picture)

Thank you, anytip?

[white_devil]

Well i guess no one can help me anymore but thx anyway for the help

[Paul Perry (Frostwave)]

I don't know what circuit you are using, but that transformer has NOTHING to do with any amp like this. The output frm these car radio chip amps usually goes via a large cap directly to the speaker (the other side of the speaker goes to ground).
That transformer is for sending a high voltage (high impedance, hence low wire loss) audio signal from a public address amplifier around a sports stadium or similar.

[white_devil]

So i dont really know how to use that transformer and why to use it, i just bought the speakers and it came with it i just dont know, so do i have to remove it?? and use the speakers directly???

As i said, i'm a newbie i dont really know what this transformer is for..

Thank you

[Peter Snow]

Well, I'm no expert on this but it looks like the transformer is a step-down to enable the speaker to be hooked up to a 70v line and this is undoubtedly the cause of some of your volume drop. That's why it sounds louder when connected to your hi-fi speakers. I would stick to a "standard" speaker for the purposes of testing so the transformer is out of the equation.

If you have no other speaker to use, then un-solder the wires from the transformer to the speaker, solder a couple of new wires directly to the speaker terminals and connect your amp directly to that. It may be as well to check the impedance of the speaker too.  A quick and dirty method is to measure the resistance of the coil by sticking a meter across the speaker terminals. You want something in the 4-16 ohm range ideally.

HTH,

Peter

[white_devil]

oh oh thanks cool:D so it doesnt matter if i just remove that transformer? and use directly the speaker input?? and i dont know if that impedance u talk about is 8 ohm, cuz the speaker say on behind "20 watts 8 ohm"  is that?? u said is something between 4 and 16 ohm..

Thanks guys

[Peter Snow]

8 ohms is good... 

Peter

[white_devil]

But is that what u mean with impedance???

Thank you

[Peter Snow]

Yes, that's right.

Peter

[white_devil]

Awsome!! :D:D:D i'll try that out soon as possible

[white_devil]

Just in case this help:

http://akamai.globalsources.com.edgesuite.net/f/593/3445/5d/pdt.static.globalsources.com/IMAGES/PDT/BIG/260/B1000791260.jpg

That's an image of a speaker of the same type, isnt exaclty that one but is really similar ..

Hope this help.. thx

[Peter Snow]

Those definitely look like public address speakers that you find in the ceilings of offices or whatever. Once you disconnect the transformer I see no reason why it should not work.  Whether it will sound good is another question

Good luck,

Peter

[white_devil]

Whether it will sound good is another question

hahaha, thank you then, so i'll have to test it out, but i'm really excited, i'll test it tomorrow (i didnt have time today) and i'll tell u my answer..

Thank you a lot bye bye