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Messages - Littlewyan

#151
Does this not increase the load capability of the PSU? As one diode can take 1A, so surely one on each winding means i can draw 2A?

The first link you sent me btw was a PSU design i planned to use in future, looks much better ;)
#152
Hi Guys, I've drawn up schematics for both the PSU and the Amp itself and attached them to this post. What do you think?
#153
What were the two diodes for by the way? Distortion?
#154
Sounds good, I'll get onto the parts buying on Wednesday and I'll let you guys know once shes finished. Thanks for all your help. I'll stay clear of RedCircuit in future and will spread the word!
#155
Well in that case I think I'll just get hold of the parts and use the chip, as it sounds like the only thing I'll learn from this circuit is how to NOT build a power amp.

By the way, how would I overdrive the Preamp?
#156
I understand that, however others have also said the power amp should work to an extent. I just wanted to see if I could get this to work, then I was going to use the TDA2030. Does the TDA2030 overdrive nicely btw? As in when its pushed?
#157
I should add that C5 is always connected in my circuit, the 47uF capacitors in the Preamp are actually 22uF which should make the situation better in theory and the line coming from R13/R14 has got a ground line going over the top of it on my PCB, however both are covered by heatshrink.
#158
Well I have changed C10 for a new capacitor in case the other one was leaky, also changed the output transistors and now I find I get the blocking distortion ALL the time. Tried increasing the voltage to 26 volts but exactly the same issue occurs. Measured the voltage on the emitters of the two output transistors and it is 13 volts, on the base of Q3 its 0.7 volts exactly. I think these voltages are correct, so perhaps its the preamp causing the issue?
#159
Ah now it is a single supply as I'm only taking the positive side of the AC Waveform coming from the two 30V windings on the transformer, which gives me a 30V positive rail that then goes into the voltage regulator. So I don't have a negative supply, just a ground.
#160
The transformer is a 2x30V, center tapped to ground and goes through a variable voltage regulator that is currently set to 24 volts. I only decided to use a regulated supply as I've never built one before!
#161
Well the TDA2050 datasheet states that the supply voltage is 25V? So does that not mean it would push out 32watts at 25volts?
#162
J M

Sorry to maybe sound a bit dumb, but can you explain what you mean with regards to the PSU? My PSU provides 24volts up to 2A, does the voltage determine the power output? As this chip can take up to 25volts, so would I have to lower my voltage a bit?

Ryan
#163
Thanks for everyone's feedback regarding this. I only built this amp as it was 10watts, so not too loud to use at band practice but its turned out to be a right pain. I should add that I'm also using a regulated PSU for this that only puts out 24volts, now as hes using an unregulated PSU his will probably provide 33volts under no load and maybe 28volts under load, could this be the issue? Also the blocking distortion starts with the volume halfway and sounds awful. I looked at that Chip but it puts out 32watts which is a bit too loud for what I want. Anyone know of a chip or design that only puts out 10watts at 8ohms?
#164
Amplifier Discussion / Serious Blocking Distortion
July 05, 2013, 10:54:13 AM
Hi Guys

I have built the circuit in this link: http://redcircuits.com/Page52.htm

And it gets pretty bad blocking distortion when you go above half way on the volume control. On full volume its so bad the amp cuts out and then comes back. Now I have tried just connecting my guitar to the 2nd JFET in the preamp and that works fine, so I think its probably the Pre Amp driving the Power Amp too hard. Any ideas? You can hear the blocking distortion start to come in a bit with the volume at half way by the way and its not the speaker as I'm driving a Marshall 2 x 12" speaker cab.

Ryan