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Topics - SurreyNick

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Amplifier Discussion / What Op Amp for 20W+ Busking Amp?
« 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?

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I’m confused.  I want to build Brian Wampler’s modified MXR Distortion Plus but the board layout I have found produced by storyboardist on the Effects Layouts blog (http://effectslayouts.blogspot.co.uk/2015/07/wampler-distortion-plus-mods.html) differs from the schematic I found which is apparently the one produced by Brian Wampler and which appeared in the article in Premier Guitar.  They both claim to be from the same source though.  Are there two different Wampler mods to the MXR?

Both versions (see attached) have distortion, tone and volume pots, plus switches for smooth, bass and compression but the version on the Effects Layouts blog has 9 diodes instead of 8, has 7 resistors instead of 4, and has 9 capacitors instead of 7.  Some of the values are different too.

Am I going mad, and which of these two versions should I build?

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Amplifier Discussion / 20 Watt Battery-Powered Amp Concept
« on: March 05, 2018, 05:55:14 AM »
I thought it might be fun to try and build a c.20 Watt battery-powered guitar amp from bits and pieces I have lying around and would invite thoughts and ideas on the proposal.

My initial idea is to use a TDA2005 in bridged mode for the amp, which the spec claims will typically produce 20 watts at 14.4 volts on a 4 ohm load, and precede this with a pre-amp stage based on the MXR Distortion Plus using a RC4558, the circuit driving a single Jensen Chicago 8/20 MOD Speaker (8 inch, 20 watt, 4 ohm) with the whole thing powered by a Ritar RT1250 12v 5.0Ah SLA battery.

The amp would only have volume and gain controls and the battery would probably be exhausted within two to three hours at full volume, but these are components I have lying around so I won’t have to go shopping for anything.  However I’m open to ideas, especially those where the build is quite straightforward.

What do you reckon?

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Amplifier Discussion / Power supply question
« on: March 04, 2018, 05:51:16 AM »
I want to build a 12V battery-powered amp employing a TDA2005 and would like some advice about the power supply.

I propose using a Ritar RT1250 12v 5.0Ah SLA battery to power the amp but I’d also like the option to run the amp from the mains using an AC-DC adapter.  I’d also like to be able to re-charge the battery without having to remove it from the amp cabinet.

I’m guessing it would be inadvisable to draw power from the adapter via the battery i.e. connect the battery in series with the adapter because the current would eventually damage the battery, so what would be the simplest way to achieve my goals?

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Amplifier Discussion / Schematics for Deanvard Amps (from the 1980s)
« on: November 09, 2016, 09:26:34 AM »
At an auction yesterday, for just a few quid, I picked up an old practice amp (pic attached). It took some time to identify the maker but it turns out it was made in the 1980s by company called Deanvard, based in Peterborough, England.  The company made a small range of SS guitar amps from a 10W practice amp (which is what I bought yesterday) to a 100W Bass amp.  I don't think they had much of a reputation and the company closed in 1991.

What I am wondering is if anyone has any schematics for this company's amps?

If so, perhaps you would be good enough to post them on the site here, or perhaps let me have a copy.

Many thanks

Nick

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As the topic title says, is there anyone out there who can help me design a circuit and schematic for a 10W+ stereo portable mini amp?

I am new to solid state circuitry, but I have a good working knowledge of vintage valve radios, so I can follow a schematic, assemble a unit etc. etc. I have just finished making my son a 'toy' 0.5W 'baccy-tin' amp and now want to make him a decent portable amp, still battery powered though (12v 4.5Ah sealed lead-acid), with optional DC adapter also used to charge the battery. This will be for practice play and for taking to the park/camping etc. He could easily buy himself a commercial unit, but I like making things and want to have a go as a surprise gift. Oh, I should mention he's a pretty good player and into heavy metal in a big way.

I'm not aiming to make anything fancy, no special effects required, just one 6.5mm input, volume, tone and gain controls, with the option to listen via the speakers or switch to headphone socket. For the speakers I was planning on two Jensen MOD5-30's. I have designed the cabinet which is 7" cuboid and the sides open out to create two wings, each of which will hold a speaker. I have attached a rough CAD drawing to give an idea and an image to show what it could look like when closed (I would use a different leather so it doesn't look so old-man!).

So, is there anyone who can help me with a circuit?

Thanks

Nick

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