Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: SurreyNick on August 06, 2019, 11:02:24 AM

Title: What Op Amp for 20W+ Busking Amp?
Post by: SurreyNick on August 06, 2019, 11:02:24 AM
For a bit of fun and to see what can be achieved, I want to build a compact busking amp using two Jenson MOD5-30 8Ω speakers which I have kicking around.  The speakers have a rated power of 35W and I was thinking of using them in parallel to give me a 4Ω load.  Power will come from one (or two) Ritar RT1250 which is a 5.0aH, 12V SLA battery.

I was thinking of using a TDA1524 in a pre-op stage, which should work well at 12VDC and give me controls for volume, balance, treble and bass.  What I can’t decide upon is what Op Amp to use.  Should I go for a dual channel op amp and try to bridge it (such as the TDA1554 2x22W power amp), or is there a decent single channel op amp I could use?

I want to get maximum power fully exploiting the potential of the two drivers, even if it means only getting an hour or two of play time.

Any thoughts on what op amps would work well?
Title: Re: What Op Amp for 20W+ Busking Amp?
Post by: phatt on August 07, 2019, 03:23:33 AM
Be aware that the claims on data sheets are often assuming full supply voltage.
With only 12Volts those ratings are greatly reduced.
There are clever units around that give over 20 watts but would draw a lot of current.

Here are some options for you;
This would run from a 12Volt battery but you still need a preamp;
https://www.jaycar.com.au/compact-2-x-20wrms-stereo-amplifier/p/AA0518

A similar option but cheaper;
https://www.jaycar.com.au/universal-amp-12w-module-m032-1-channel/p/AA0225

This is in Australia but I'm sure similar stuff exists in other countries.
A simple Treble/Bass preamp can be made from a dual opamp such as TL072.
Phil.
Title: Re: What Op Amp for 20W+ Busking Amp?
Post by: SurreyNick on August 07, 2019, 07:11:34 AM
Thanks for the suggestions Phil

The Compact 2 x 20WRMS Stereo Amplifier isn't really what I'm looking for.  I prefer to buy an IC loose and build into my own circuit board, or at a push buy an op amp on a small pre-built board.  The Kemo MO32 could be a runner, but if I've done my calcs right with a 12VDC supply and 2x8ohm speakers in parallel it'll only give me 12W of power.  The speakers can handle considerably more than this.  I will consider the MO34 though, which is the 40W variant you mentioned, but at UK£25 just for the IC it's quite pricey!

I came across the TPA3110 and the TPA3118 and wonder if anyone has any views on their suitability?

Nick
Title: Re: What Op Amp for 20W+ Busking Amp?
Post by: tonyharker on August 08, 2019, 05:36:53 AM
Check out the OEP30w amplifier this will give you 17w into 2x8 ohm speakers in parallel at 12v.  Class d bridged amplifier, you wont hear the difference between 17 and 20w. All over ebay at about $2
Title: Re: What Op Amp for 20W+ Busking Amp?
Post by: SurreyNick on August 08, 2019, 07:25:27 AM
Thanks.  The OEP30w appears to be an excellent choice.   :tu:
Title: Re: What Op Amp for 20W+ Busking Amp?
Post by: joecool85 on August 12, 2019, 04:10:14 PM
Thanks.  The OEP30w appears to be an excellent choice.   :tu:

It looks like at 12v you will only be getting 10w @ 8 ohm and 12w @ 4 ohm.  Still probably plenty, but beware.