Hello all

I recently bought a Celestion Bulldog speaker, made in UK for Vox, 15W, 6 Ohm. I want to build an amp head just for this beauty.
I am unable to choose between TDA2030, 2040 and 2050, does anyone have any recommendations?
What transformer ratings should I go for? (THE AMP MUST NEVER REACH > 15W 6 Ohm)

Thank you in advance 

Hello all

I have built a little 1W amp using a TDA7267 (schematic: http://www.st.com/stonline/books/pdf/docs/1569.pdf). It worked like charm. I then decided to add a volume control, so instead of the input capacitor at pin 4 I connected a 100k log pot between pin 4 and ground. I then connected the input capacitor at the pot's input. The layout is like this:

INPUT -||-|-----
               |
               |---- PIN 4
               |
               |---- INPUT GND + PIN 5 (CIRCUIT GROUND)

(sorry for the terrible ASCII scematic, I have no EDA software on this computer)

The circuit did not work anymore. Instead of 10mA of quiescent current it drew before, it drew 60mA afterwards. It produced no sounds at low volume and a low sound, heavily distorted, at high volume. I removed the pot and reverted to the original design, It worked normal again.

I have build this circuit twice with different stripboard layouts, different caps. I am fairly positive that the issue is the log connectivity and not somewhere else (e.g. faulty caps).

Any thoughts?

I have read that a major difference between guitar amplifiers and hi-fi is the bandwidth. Since a guitar produces sounds from 80 to 5000 Hz higher frequencies are not only unnecessary but also unwanted, since they can introduce interference and oscillation.

In a TDA2003 circuit this is controlled by the Cx-Rx network. I have changed the original values from 39 to 47 nF and Ω, respectively - haven't noticed any difference. What would be a correct set of values?

Hello all

I am looking for a chip able to produce around 1-2 watt on a single channel with no distortion. Unfortunately all chips I have found so far have very high gain, and for this low power it means heavy distortion. I tried installing resistors in series with the input, but it is not the optimal way as I practically amplify input noise. To make matters worse I work on stripboard and this limits my choices - SIPs are obsolete, DIPs cannot be heatsinked, Pentawatts are one category higher in terms of power and require higher voltages.

I would appreciate any suggestions.

Just built a TDA2003 amp on stripboard, works like charm :-) I have read the sticky post suggesting grounding techniques at the Amplifier Discussion subsection of this forum, and I have placed the chip in the middle of the board, with power supply & speaker connections and caps and the zobel network on one side of the stripboard, and all other connections to the other. I cannot imagine a better way to do this without pcb :-S The chip's quiescent current at 12 Volts with 1.6Ω load (two 3.2Ω speakers in parallel) is 40mA, meaning I have no oscillation issues.

My problem is that I have this audible hum which is reduced only when I 1) touch the heatsink, or 2) touch the shield of the shielded input wire, or 3) connect the circuit to my guitar and touch the strings. With the guitar connected and none if its metal parts touched, the hum gets really annoying. If that helps you, the hum is exactly the one I get from my Marshall MS-2 battery-powered amp. To make matters worse, I have not installed an input pot yet, and with its 40db gain the TDA2003 is unforgiving :-)

My question is: What can I do to reduce the hum?

I have not installed it in a case yet, and supply it by my bench PSU. I was thinking of connecting the safety ground cable to the screw holding the chip to the heatsink, seems to me like a good spot. What do you think? In case of a simple 2-wire connection (no safety ground cable) what should I do?

P.s.: If it is of any relevance, I have changed the values of some parts: C4 (output coupling to load) from 1000 to 2200 μF, C2 (ripple rejection) from 470 to 2200 μF, Rx from 39 to 47 Ω, Cx from 39 to 47 nF.

I hope I write in the proper subforum.

Does anyone have a schematic of the Marshall MS-2? I have searched everywhere in the site, including the links to other sites, but found nothing.

Hello all, I am new in here :-)

I have a question regarding the Pentawatt class AB models from ST (TDA2003, TDA2006, TDA2030, TDA2040, TDA2050). I want to include a volume control in the input, but I have 3 questions:

1) What type of pot do I use? logarithmic or linear?
2) How do I calculate its value?
Where do I place the capacitor?

Thank you in advance.