]I built one of these into a practice amp
http://www.vellemanusa.com/downloads/0/illustrated/illustrated_assembly_manual_k4001.pdf
Its powered by a 9v battery or a 12v power supply, in a 6"x9"x5" enclosure with a 4" 6W 8ohm speaker.
Any ideas on getting a bit of clean headroom on it? it goes into gritty overdrive pretty quickly. I do like that but would like more clean if possible.
https://sqtu8a-sn3301.files.1drv.com/y3mal6r6dsV_fjgpC0VUxSw0Psb_ZCn2i4Gixu6pstBdmNprn8RNGNiUe3FvJcmTDoXdS1Cx1QXDuZAaWfA_sCQPYgMXS5DppEbXR4tuaQQN3_JNCSJf7d57tuj5Xo5cTMcnoPv1IeESIn7MuLkIdT-bK98yhFXOGCykALazlgHDn0?width=2322&height=4128&cropmode=none (https://sqtu8a-sn3301.files.1drv.com/y3mal6r6dsV_fjgpC0VUxSw0Psb_ZCn2i4Gixu6pstBdmNprn8RNGNiUe3FvJcmTDoXdS1Cx1QXDuZAaWfA_sCQPYgMXS5DppEbXR4tuaQQN3_JNCSJf7d57tuj5Xo5cTMcnoPv1IeESIn7MuLkIdT-bK98yhFXOGCykALazlgHDn0?width=2322&height=4128&cropmode=none)https://s6tu8a-sn3301.files.1drv.com/y3mkd0BFs-OuSa0LQgNjSnTqj8EA-jinsUa6s6kUS6G38yEb1qFesbTImImHYdnFbmTQieIGLcQEE_BNVpWYZP6qiRHwhpNTIPK7KViepoycbzcNT9cLwodHwzcN3dcevMIEMESy5ei4rWwMEiAtSjCOhh8JRA3lyzLDLKHcqsrlLU?width=2322&height=4128&cropmode=none (https://s6tu8a-sn3301.files.1drv.com/y3mkd0BFs-OuSa0LQgNjSnTqj8EA-jinsUa6s6kUS6G38yEb1qFesbTImImHYdnFbmTQieIGLcQEE_BNVpWYZP6qiRHwhpNTIPK7KViepoycbzcNT9cLwodHwzcN3dcevMIEMESy5ei4rWwMEiAtSjCOhh8JRA3lyzLDLKHcqsrlLU?width=2322&height=4128&cropmode=none)
You need a higher supply voltage if you want more clean. :tu:
Phil.
Thanks for that. It can take up to 18 v so will look for a new supply ti deliver that. Or 12 AA batteries. Would a 4 ohm speaker help?
4 ohms will be a bit louder but twice the current draw on your battery and it may or may not help the distortion.
You really need a bigger amp unit and a preamp will also help as raw guitar signal may be to much low frequency which adds to the distortion problem.
Phil.
Think iIl just accept that i can have quiet and clean or loud and dirty. For quiet and dirty i can use my overdrive pedal. Will be back for more ideas on my next build-possibly something tiny with a 2" speaker just for fun.
I'm using that chip for a similar project. The cleanest sound I was able to achieve was using the +15v side of a regulated bipolar supply (Rod Elliot's board). It sounded great, but the regulator got too hot to touch so I shut it down. Velleman makes a really cheap 1a regulated, adjustable supply that I'd like to try in the future, but for now I have 4X9v batteries in series/parallel for a bit more than 18v. It still breaks up too soon for my taste, but I put a 50k pot between the guitar and the input and that cleans it up at the expense of some volume. I'm using an 8 ohm, 8-inch Peavey speaker (I think I like my Radio Shack closeout/ceiling PA 8" better). No preamp, yet. Glad to see someone else using this chip/board; keep us posted.
Mackayprod, thats cool. Are you using the Velleman kit, or just the TDA2003 chip which is at the heart of it? I got kit from Maplins (the UK/Ireland equivalent of Radio Shack)
Been playing with it again and decided I like it (or am too lazy to modify). basically I play it quiet or else flat out (wakes the family if not the neighbours) and theres no in-between. One mod I heard of is to use a smaller resistor going in to the inverting input. this increases negative feedback thus reducing the gain. I based the enclosure design on the Pignose (imitation, flattery and all that) though its a bit smaller. I put a bit of effort to fit a DC input jack and also a headphone out jack, so I can always change the guts while keeping the enclosure (of which I'm quite proud). Mainly used with my homemade Lap Steel and a Hofner Shorty guitar. Actually sounds great as a Harmonica amp too.
Letting the battery run down gives more distortion anyway (sometimes in a good way...) as Brian May did with his Deacy amp. You can now buy a Deacy replica including a variable power supply to simulate a dying battery but wheres the fun in that?
Any suggestions for preamp design?
I'm using the Velleman kit. I originally used it as a quick-n-dirty guitar amp for my daughter, who got a strat copy for Christmas. I built it into an old RCA hi-fi speaker with an on-off switch and a 9v battery. As I remember, it sounded better on those single-coil pickups than it does with my humbuckers. I think the battery power supply lacks enough current to give the chip all the headroom we are looking for, or at least that's the theory I'm working from now.
I'm going to build the Rod Elliott P27 circuit and experiment with the diode "soft-clipping" system http://sound.westhost.com/project27.htm (http://sound.westhost.com/project27.htm).
I've been looking at the TDA datasheet and would like to try to reduce the gain of that chip...better to do that than to pad the input? If we can drive the amp into clipping with just a guitar pickup straight in, why use a preamp (other than for eq control, pickup loading impedance)? I think that's done by varying R1/R2, but I'll try to figure it out and post.
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
Quote from: J M Fahey on May 29, 2016, 06:48:11 AM
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
OK here is plan B. I've been playing around with the Lm386 opamp and decided it might suit my little enclosure better than the TDA2003. I thought id use 2 of the TDA2003 modules with each one driving a 4" car speaker in some sort of cabinet. Maybe shaped like the Roland Street Cube https://m.thomann.de/ie/roland_cube_street_bk.htm
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Quote from: flester on December 02, 2017, 02:57:56 PM
Quote from: J M Fahey on May 29, 2016, 06:48:11 AM
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
OK here is plan B. I've been playing around with the Lm386 opamp and decided it might suit my little enclosure better than the TDA2003. I thought id use 2 of the TDA2003 modules with each one driving a 4" car speaker in some sort of cabinet. Maybe shaped like the Roland Street Cube https://m.thomann.de/ie/roland_cube_street_bk.htm
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I'm making my first foray into DIY solid state amps with this kit. Can anyone tell me what happens if I use a 50k log pot instead of a 47 ?
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50k versus 47k? Absolutely nothing different.
50k versus 47 ohms? All the difference in the world.
Quote from: Enzo on January 17, 2018, 10:28:02 PM
50k versus 47k? Absolutely nothing different.
50k versus 47 ohms? All the difference in the world.
Lol clearly. Thanks!
Any ideas on how to get a single tone pot into this circuit?
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Quote from: flester on December 02, 2017, 02:57:56 PM
Quote from: J M Fahey on May 29, 2016, 06:48:11 AM
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
OK here is plan B. I've been playing around with the Lm386 opamp and decided it might suit my little enclosure better than the TDA2003. I thought id use 2 of the TDA2003 modules with each one driving a 4" car speaker in some sort of cabinet. Maybe shaped like the Roland Street Cube https://m.thomann.de/ie/roland_cube_street_bk.htm
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Heres the beginnings of my stereo 2 x tda2003 project. Sounds a bit better than my previous enclosure with the 5w 4" 8ohm speaker. These very cheap 4" car speakers are rated at 4 ohms and 80W rms. Seems optimistic but they should be able for 4W rms. Still need a preamp for guitar use - any suggestions?
I also want to see if it works as a Smartphone amp. Planning some wine-themed styling on the wine box enclosure.(https://uploads.tapatalk-cdn.com/20180211/77dc25c91019d20b1406954471cedcdd.jpg)(https://uploads.tapatalk-cdn.com/20180211/390baabdfaf639759a9e924977c8bee8.jpg)
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Quote from: flester on February 11, 2018, 02:37:12 PM
Quote from: flester on December 02, 2017, 02:57:56 PM
Quote from: J M Fahey on May 29, 2016, 06:48:11 AM
You can't reduce gain very much, I guess minimum is around 20X , because it becomes unstable.
So reduce R2/R1 ratio to about 20:1 but not less, any ectra reduction myst be input padding."Which is not all bad, you can add a passive tone conrol which will be lossy anyway.
OK here is plan B. I've been playing around with the Lm386 opamp and decided it might suit my little enclosure better than the TDA2003. I thought id use 2 of the TDA2003 modules with each one driving a 4" car speaker in some sort of cabinet. Maybe shaped like the Roland Street Cube https://m.thomann.de/ie/roland_cube_street_bk.htm
Sent from my SM-G935F using Tapatalk
Heres the beginnings of my stereo 2 x tda2003 project. Sounds a bit better than my previous enclosure with the 5w 4" 8ohm speaker. These very cheap 4" car speakers are rated at 4 ohms and 80W rms. Seems optimistic but they should be able for 4W rms. Still need a preamp for guitar use - any suggestions?
I also want to see if it works as a Smartphone amp. Planning some wine-themed styling on the wine box enclosure.(https://uploads.tapatalk-cdn.com/20180211/77dc25c91019d20b1406954471cedcdd.jpg)(https://uploads.tapatalk-cdn.com/20180211/390baabdfaf639759a9e924977c8bee8.jpg)
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BTW i put a Kemo 12w module into the original enclosure. I found it breaks up nicely with a mic'd harmonica (as did the TDA2003 in fact). Goin to add a back to the enclosure to reduce feedback. Just learning how important enclosure design is by trial and erroer.
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