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DIY Stompboxes => Building your own stompbox => Topic started by: whomeno on November 18, 2019, 10:13:25 PM

Title: Stupid question
Post by: whomeno on November 18, 2019, 10:13:25 PM
will a regular mono audio amplifier work as a power amplifier?
I would put a pre amp into it.
looking at some of the prebuilt 50 watt
Title: Re: Stuip question
Post by: mth5044 on November 18, 2019, 10:55:47 PM
Would be good to provide more information. Link to what you're looking at?
Title: Re: Stuip question
Post by: whomeno on November 18, 2019, 11:09:00 PM
I'm looking to put a power amplifier in a 125b . then have some pre built pre amp pedals to run to it. I built the tiny giant amp and just now modded it to run at 16.8 volts, but would like to find some thing in the 40 to 50 watt range at 8 ohm. more like the exh magnuim 44 pedal.  I have a marshall dsl 40 cr and a peveay valve king 20 now but looking for a pedal.
Title: Re: Stuip question
Post by: vigilante397 on November 19, 2019, 12:09:24 AM
Do you have a link to the amplifier module you're considering? That's what mth5044 was asking.
Title: Re: Stuip question
Post by: antonis on November 19, 2019, 05:18:42 AM
Also, what exactly means "stuip"..??  ::)
Title: Re: Stuip question
Post by: whomeno on November 19, 2019, 07:50:06 AM
here is one
https://www.amazon.com/dp/B07GBX7DS3/?coliid=I2W7O2ZC4HGDJG&colid=2CMFVYV4SFRNA&psc=1&ref_=lv_ov_lig_dp_it
Title: Re: Stuip question
Post by: Mark Hammer on November 19, 2019, 08:40:21 AM
Analog amps like that one will require sufficient heat-sinking ti dump the heat created by higher power,  Can you achieve that in a 125B?  I have my doubts.  I suspect that the EHX units are all class D amps with switching power supplies, rather than analog.

I picked up one of these last summer for around $10-12. https://www.parts-express.com/tpa3116d2-2x50w-class-d-stereo-amplifier-board-with-volume-control--320-699  You will note that the heat sinking provided does not permit any sort of thermal coupling to a larger heatsink or the wall of an enclosure, implying that it doesn't need more than is provided, except maybe some decent ventilation.

For your power and size requirements, class D is likely what you want.
Title: Re: Stupid question
Post by: whomeno on November 19, 2019, 09:16:49 AM
Mark,
Would this fit in a 125b?
Could I just use 1 output?
If so what would I need to do with the
Other one?
Thanks
Title: Re: Stupid question
Post by: Mark Hammer on November 19, 2019, 01:56:32 PM
Here's your answer.  I placed the amp on the back plate of a 125B enclosure.  As you can see, plenty of room for an input and output jack, and power jack.  As for whether one can run only one channel,and do so safely, I leave that determination to others.  My own hunch is that you may need to terminate the unused channel.  On the other hand, there ARE single-channel amplifiers of this type available, which sidesteps the problem.
(https://i.imgur.com/Bgjjh3J.jpg)
Title: Re: Stupid question
Post by: whomeno on November 19, 2019, 02:28:38 PM
Thanks
Title: Re: Stupid question
Post by: Ben N on November 19, 2019, 03:19:14 PM
Yup, class D is the only way to do what you want (AFAIK) and works fine, but you may have to pad down or limit you preamp's output. This is no tube amp, and any saturation of the power amp is going to sound bad, so you have to keep it linear--it is just like reamping. Of course you can simulate power amp saturation in the preamp. I've got one of these
(https://voxamps.com/wp-content/uploads/2019/01/MV50AC-MINI-AMP-HEAD.png)
in my practice rig (works into a cab or headphones), and it's class D power--no problem, sounds great, just all the dirt comes from the nutube preamp or upstream.
Title: Re: Stupid question
Post by: whomeno on November 19, 2019, 03:21:02 PM
would something like this be good? it is only 35 watt.
https://www.banggood.com/TDA8932-35W-Digital-Amplifier-Board-Module-Mono-amplifier-Low-Power-Consumption-p-1460337.html?rmmds=search&cur_warehouse=CN
Title: Re: Stupid question
Post by: stallik on November 19, 2019, 03:41:53 PM
Quote from: whomeno on November 19, 2019, 03:21:02 PM
would something like this be good? it is only 35 watt.
https://www.banggood.com/TDA8932-35W-Digital-Amplifier-Board-Module-Mono-amplifier-Low-Power-Consumption-p-1460337.html?rmmds=search&cur_warehouse=CN

I'd say that this would be good for something. Whether it's good for what you want? Probably but maybe not. At this price, what's the harm in trying one?
I've played with many boards of this type and they've all worked though I tend now to take the wattage as pure marketing - I'm used to valves. The  power supplies I've built for the boards end up being much bigger than the board itself
Title: Re: Stupid question
Post by: Ben N on November 20, 2019, 09:20:06 AM
If you're used to tubes, I'd say half would be optimistic. I seriously doubt you can get the useable volume of a Princeton (15W) out of this. Remember, these things are only good up to the onset of distortion, IOW pretty much the opposite of a tube amp. Also, their protection tends to kick in if you work them hard, and they - just - shut - down (and come back to life after cooling down). So I'd say for practice/living room playing, this would be plenty. Add a drummer or bass player, probably not.
Also, as RG Keen, never tires of pointing out, a power amp is pretty much a power supply with a few extra parts. Powering this little gem with 24v@2A will cost a multiple of the amp itself.