hello folks transformer PSU question

[chippyguitars]

I want to fiddle around with this batch of tda2030's and these little
transformers only I dont understand the whole solid state power supply, volt/amp rating and such, I am also building for guitar so
I dont need perfection just dont want to smoke the transformers

I have a batch of these little 18-0-18 at 750ma (wimpy)
and the other winding has 24vac at 2 amps,

so would I be better off going single rail with the 24 volt
and if I need to have the +- rails for opamps or what not
do that.... or can I use the split rail with less than 1 amp?
with a tda-2030?

I have seen some really small transformers in cheap guitar amps..
but I am not sure what happens there does it just produce less power when it cant draw any more current?
again with guitar I am likely going to want distortion and power
output is not critical I just want to make noise.. and experiment

also can I split the rail without a center tap on the 24 volt line? I am so used to tubes ...
this whole low voltage/ high current solid state world confuses me

I dont really need the split supply for the preamp as I am likely to use jfets

ok sorry to brain dump too much in one post!

[Leolabs]

12V-0V-12V ,a few Amps and above is enough for a TDA2030.Your 18V-0V-18V ,750mA can be use for your preamp,assume that it is a discrete design as a normal OPAMP won't go for +/-25V(after rectification).

[chippyguitars]

ok I guess can you split the rails with no center tap?
on the 24vac.. only the low current side is center tapped on this one
the other option is single supply I guess

[lndm]

It seems to me that a 18-0-18 750mA transformer is what I'd call a common choice for running (multiple) op-amps, FWIW.

When it comes to assessing the current capability, you need to visualise the power supply as having a resistance (source resistance). If the load is of such a low resistance that it equals the source resistance, half the voltage will be seen across the load, and half held across the power supply, for example. A transformer is typically rated so that when you draw the rated power, the load will see around 90% of the unloaded voltage so the load there would be around 10 times the source resistance.

[AndrewT]

Hi Chirpy,
I see two different problems that are both easily overcome.

First, for solid state, it is generally more convenient to have both positive and negative supplies to power the circuits. Most circuits can be made to work with a single polarity PSU but a number of circuit topologies are used to trick the circuit into believeing it has a dual polarity supply.

Just use +- dual polarity supply, it makes it easier.

Secondly, you plan to use/build a guitar practice amp.

The duty from a guitar is heavy and/or very transient. You should design for both.

You need peak ability for that strong TWANG when it happens and also continuous power capability for the strumming that seems to go on for ever (when the mood takes you).

These equate to PA duty not domestic. And don't fall into the trap that distortion is acceptable just because you choose to send a deliberately distorted signal to the amp. You should want the amp speaker combination to reproduce accurately all the signals you send. Aim for quality and let your skill produce the effects.

Now decide on the SPL you can tolerate in your practice environment. This will determine the sensitivity of your speaker and the power of your amp. Do the calculations after that decision is made.

[chippyguitars]

some smart cookies over here !
thanks I have to digest things a bit now

so yeah you can use a voltage divider to get the split rail from the
24VAC line right? although I just looked at the peavey rage 158 on schematic heaven..
and it looks to be single supply and that is way enough noise
being made there about 15 20 watts with the tda2040

I wanted to build discreet preamp with jfets and use the chipamp
for power I also got these transformers really cheap
so I am trying to use them as opposed to getting the ideal
parts

Thanks again for the responses you guys know your stuff