Velleman

[martind]

Hi,

just found this site by googling solid state guitar amp.

I'm thinking of building an amp using the velleman 200w kit (http://www.velleman.be/ot/en/product/view/?id=360356 ) with a preamp based around one or more of the ROG amp simulations. I'd also like opinions on whether or not it would be practical to utilise it, with a different pre-amp, for acoustic guitar.

200w is way more than I need, but it's 100w in real money and that should allow plenty of headroom so the only distortion is from the pre-amp. I can get the module and transformer for circa £60 which seems cost effective.

If this isn't a good solution, can you suggest a schematic or better still a module around 50 to 100w RMS that would do the job.

The amp would be built as a head unit and would be used to drive a Celestion VIntage 30 and G12H30 in parallel at 4 ohms.

For those concerned about my abilities wielding a soldering iron, I've built 3 valve amps and more effect pedals than I have fingers to count them with. I know my way around a schematic and have produced my own PCB's, but prefer stripboard for one off builds. I don't want to sound as if I'm blowing my own trumpet and acknowledge the greater experience here, just trying to head off some questions.

Regards

Martin

[darwindeathcat]

Hey Bro, if you are definately want to build from a kit, you should veer away from the Velleman ones and more towards something like this: http://www.chipamp.com/lm3886.shtml You'll get a better quality kit with better quality parts, for the same price, and it will actually work as described. I haven't built one of these kits (I've never built a poweramp from a kit, actually), but I have/am building an amp with the same chip (lm3886), and a quick perusal of the archives here will show you that this is really the best way to go... Many of us have had/are having great success building lm3886 amps with ROG preamps. Look over in the preamp forum for many great posts on using ROG circuits as preamps (something I've actually been discussing a lot in there)
good luck and happy building!

[teemuk]

I'm always doubtful about projects/kits that eagerly quote their –peak- power like this one. As a result, their "200W power amplifier" turned out to be a 100W average amp. Furthermore, even the 100W is exaggerated since that amp is pushed to the limits when you drive it with that sort of power. The outputs are single pair of TIP142/147 and these have a dissipation of 125W, which drops to 100W when case temperature is 50 degrees of Celsius. Expecting that this kind of circuit can deliver the said 100W average without failure for a moderate period of time is just not very realistic. More realistic expectation is closer to 60 – 70 watts, which happens to be the rating commonly given for commercial amps that use a single pair of those very same transistors. Double their amount and you have more luck reaching the 100W while the amp still runs cool.

Power amp of Rod Elliot's project 27 is much better suited for guitar applications than this Velleman kit. You could also find very similar designs from most solid-state guitar amps of the 90's. TIP142/147 where popular output devices, now they're pretty much obsolete. Aside discrete, you could also build some chip amp design and lend the circuit from some guitar amp using such chip. I'd be tempted to try two TDA7293 chips, in parallel "slave mode".

[darwindeathcat]

here's a more moderately priced lm3876/3886 amp kit: https://secure.vividcluster.crox.net.au/jaycar2005/productView.asp?ID=KC5150&CATID=25&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=557

[martind]

That seems like quite a strong no for the Velleman kit, with some good reasoning behind it.

The LM3886 chip looks interesting, however the kits mentioned are not UK based. (I'd prefer a kit, but it's not essential.) Can anyone recommend a UK supplier?

Regards

Martin

[Jack1962]

First off , welcome to the forum. I too have built many amps(tube and SS) , saying this bro , did you read the specs on this kit? there is no way it will produce 200 Watts, 50 Watts  is closer for guitar. I haven't built the ROG preamp , myself but they like them here and they are a solid design. However back to your power amp, I would abandon the kit idea , if you have a source for components near you I would build from a guitar or power amp schematic tons of them are avaiable , tryed and true designs are the way to go bro,


                                           Rock On

[martind]

Thanks for the welcome. I did read and the specs, and I probably didn't make it clear in my original post that I wasn't expecting to run it flat out but the 100w rms would have given me plenty of headroom, allowing any distortion to come from the pre-amps and be under control. Anyway, given the comments I've decided to abandon that path, unless desperation sets in.

Part of the attraction of a kit or module, at this point in time, is that I'm looking to get something together for a gig (my first) at the start of November. I don't want to spend a lot of time building and tweaking if I can help it. I'd rather be getting on with practicing. I do have an 18 watt lite, which might have done the job if it wasn't for the one track where I need to play clean, hence my investigation into ss amps/modules.

I've been considering using one of the ROG circuits as a pre-amp into a PA driving my guitar cab, not sure how well this would pan out but I may well give it a try in the near future. Has anyone here done something similar?

Regards

Martin