Hi Sugarhi, I meant to have selectable channels... Not to have several preamps running through eachother... In that case you are definately right... But many commercial amps have multiple channels, each with their own sound. I'm not one hundred percent sure, but I believe that each "channel" on a combo amp is actually a differnt preamp, and that they all feed into one power amp. My main question from a diy perspective, is whether or not you can have all the outputs of the preamps connected to the input of the poweramp stage at one time (ie have all the preamps in parallel, and getting powered, whether or not all of them have an input signal). In this formation, each preamp would have it's own input jack as well as controls, and in theory you could plug into two or more channels at a time (either with an external a/b box, or have different instruments/mics plugged into the differnt channels). This would definately be the simplest way to go.
   The other way I would think to do this is to have a single input, and use a double gang rotary switch to route the signal and power to the preamp circuit that you wish to be using at any one time. The outputs of each preamp would still be all connected to the single input of the poweramp, but the difference is that no power would be sent to the channels that are not used.
   I guess that you could also use the stereo-jack method to cut the ground if you wanted to still have a jack per preamp, but not have power flowing to the unused preamp channels.
   I wonder also, I guess if you can have two preamps feeding signal to the power amp simultaneously? I don't see any real reason why you can't... Would you need to stick a mixer stage in between?

   Anyway, I still think it would be really cool to build a DIY gainclone amp with multiple "voices"...

Hey, how does one connect multiple preamps to the input of a poweramp? It would be VERY cool to build several of these runoffgroove jfet circuits into a combo amp. that way you could have multiple channels, all with a "clone" sound of the different amps those pedals are made to simulate.
  Would one simply connect the outputs of all the differnt preamps in parallel to the input of the poweramp stage? Or would one have to make sure that only one preamp is connected to the power amp at a time (ie. with a rotaryswitch ).I'm sure each preamp would have to have it's own input jack and control pots.
  I'm planning on making a lm3875 "gainclone" as a poweramp, and really would love to build several of these fairly simple ROG circuits as pramps for it... that would make a killer combo!

Thanks for your reply! I got some good advice about this from another forum also, and I think I have been thoroughly convinced that a chipamp is the way to go. My choices are the lm3875, lm3886, and the TDA2050 (as you suggest). I read at the "decibledungeon" website about using a couple of old computer power supplies (to get +-24v) with a lm3875 gainclone, and that's one idea I might take. Otherwise, I guess I can head to the thrift store and buy some cheap old HiFi equipment, and hope I get a good transformer and/or heatsink out of it... Hopefully, with all the stuff in my parts bin, the chip and other components that I have to order, and the "salvaged" transformer, I can get one of these chipamps together for less than $20. I've got several preamps builds lying around, but I also thought of building in one of those runoffgroove pedal designs, like the english channel or professor tweed, into this thing as well... That will add a bit to the cost, but certainly not more than $10 more... A 40-60 watt Harp amp, for under $40 total? If it sounds good it will be an amazing deal! I'll keep you advised of my progress!

Hey, I have read several interesting things about this, the best is probably here: http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonesmps.html

I have also read about how to mod ATX computer power supplies, for example here: http://www.instructables.com/id/ATX--%3e-Lab-Bench-Power-Supply-Conversion/?ALLSTEPS

I am planning on using this kind of power supply in a gainclone power amp, but need to collect me some old computers first!
Let us know if you get this working, and I'll let you know If I do too!

Well, I just built this over the weekend. It sounds really really good! I am a blues harmonica player, and I built this because I wanted to a "tube sound" at an affordable price. I really think that this circuit does that. I'm ran a couple of my homemade customized dynamic and piezo mics through it last night, and then into the "line in" jack on my crappy old Solid State 20w PA amp and 2x10 cab. It sounds to me MUCH warmer (ie. tube-like) than either plugging the mics directly into the PA's mic preamp jacks, or using my legendary pignose to preamp the signal (and much less noise too!). I added a "simply wonderful tone control" and a 100k volume pot, and opted to have a drive pot as well as the the gain pot pictured in the circuit. I haven't experimented too much with it yet as I haven't boxed it up yet (I'm waiting for the paint to dry on the enclosure), but so far I am VERY pleased with this thing. By the way I used .47uf coupling caps which I heard somewhere help "voice" amps for harp by allowing more bass... Once I box it up, I'll add this to my line up in the following manner Mic->Dano Fish and Chips EQ->Modded Dano Fab Echo->SSTS Preamp->Solid State PA->2x10 cab

If anyone is interested in sound samples or pictures, just let me know and I'll post some...

My next project will be a LM3886 or LM3875 power amp that I will build into my cab, thereby eliminating the crappy PA amp all together!

Hi All,

    I've been looking for an amp build that was: 1)easy, 2)in the 30-40 watt range, and 3)used a single rail power supply so that it was 4)cheap. After untold hours of searching, I seem to have found the solution in two schematics that use the TDA2030 in conjunction with two power transistors. The first schematic comes from a kit offered by quasar electronics (UK) (http://www.electronic-kits-and-projects.com/1109.htm) (schematic is a pdf listed at the bottom of the description, and the other is listed on elecfree.com (http://www.elecfree.com/circuit/power-amplifier/30w-amp-otl-by-tda2030-transistor/
Power Amplifier : Power Amplifier OTL 30W by IC TDA2030 +Transistor).
   My questions for the list are as follows:
   1) I would prefer to build from the schematic from the quasar kit because I know it is proven, and it puts out more power. However, they (of course) do not list any component values other than the IC and Transistor types, and the input voltages. I'm more of a "follow instructions guy" when it comes to amp building, so I have no idea how to calculate these values. Can I use similar values from the other schematic (the elecfree one)? That schematic is very similar except that it uses different transistors and has a lower input voltage (and is missing the equivalent of C2, R1, and R3 in the quasar schematic).
    2) As the TDA2030 seems to be hard to find here in the states, I have looked up the NTE replacement for it, which is the NTE1380. Looking over the datasheet, it *seems* to be an exact duplicate. Is anyone aware of any deviations from the TDA2030 pinout?
   3) As far as the transistor types: I was unable to find the exact types from the schematics. Can I uses some sort of generic equivalents? Any suggestions on which ones?
   4) Any other suggestions about these schematics?

Any help would be greatly appreciated!!!

Well, I guess nobody cares, but I went ahead and ordered the components and am going to build this thing anyway... Maybe I'll write about my results...

Correct me if I am wrong, but isn't the Noisy Cricket just a souped up version of the Little Gem. I think that the main differences are the "grit" switch and the tone controls, right? If you aren't getting enough volume, check to see that that you have grounded the speaker to the common ground (ie the battery) rather than to the chassis. I made that mistake once, and as soon as corrected it, I got my volume back!

Hi all, I'm new to the list, and am about to embark on my first major "from scratch" amp project (i've built a few general purpose amp kits, and modified several existing amps). Instead of starting with the de rigour noisy cricket or little gem, I came across a schematic at this site: http://members.tripod.com/gillcar/id24.htm for what seems to be a very cool and easily built "tube clone" preamp circuit. Before I place my smallbear and electronics goldmine orders for parts, however, I wanted to ask the list if anyone knows or has built this circuit? Does it work? Does it sound good? Is it worth my time? Are there any known flaws in the design or any essential mods I need to know? Any help I could get would be greatly appreciated...

BTW I play blues harp, and plan to use this to get good tube style blues tone to feed into my vintage 20watt pa amp...