Hi all, This is something I've been thinking about for a good while now, and I thought I'd poll the knowledgeable crowd here to see if anyone has any words of wisdom for me before I start in on it.
So here's the idea:
I want to build me a small battery powered busking amp for playing amplified blues harp on the street. I have a little pignose that I use now, but I'd like an amp with bit more bottom-end and that can actually clean up a little if I want (the piggy is all dirt, all the time). I've built a couple of lm386 chip amps, and I'm not really enamored with them either.
So, what I've got now to work with is a Hitachi HA 13001 single supply chip amp that I've built from a kit. It was way too noisy when powered from a wall supply (even with a well-filtered PS), but I think it have WAY less hum on battery power, which should be doable since it requires only +8 to +18 V at ~1amp. The pignose is powered with 6 rechargeable AA's (9volts) and lasts quite a while. The current draw is nowhere near as high as 1 amp though (I think it's ~300mA), so I don't know if this battery configuration will work well for the Hitachi chip, or not. I can get a 4-5 AH 12 volt sealed lead acid battery for about $15 at Fry's Electronics. I'm assuming that if the amplifier circuit is pulling 1 Amp (on average) that means that a 4-5 AH lead acid battery will give me 4-5 hours of continuous play time. Is that a safe assumption? Following this logic, if I'm using 2100 mAH double A's in series, I would only get ~2 hours if the circuit is drawing 1 amp? Does that make sense?
Oh, I'll be using a modified ROG peppermill for a preamp, which let's me dial in clean or go to some pretty nice overdrive if I want.
Pros and cons of battery type:
To go the AA route, I would not have to buy anything (I have battery holders already and an external charger too), but I'm not sure how quickly the batteries would drain. For the 12volt I'd be spending ~25 bucks for the battery and charger, but it *should* give longer play time. If I go with the AA's I'm cool for the preamp supply too (9volts), but I'd have to use a regulator if I went with the 12volt. I know that the 12 volt will get me louder output (data sheet says it'll put somewhere in the realm of 15 watts into 4 ohms at 12volts/1.5-2 amps, so i'll prob get 10watts), but I'm cool with lower output (it'll prob be more like 5-6 watts running on 9v using a bunch of in series 2100 mAH AA batts) if it's easier/cheaper for me to build. It will still be PLENTY loud enough. I'll run this amp through 2 vintage 8" speakers as well (in parallel for 4 ohm load), so that should help get more of the low end out (the piggy I use now only has one 6" speaker).
Future:
What about other battery-powered amp designs (beyond lm386)? Anyone experiment with 12volt single supply chips meant for car audio? These could be very cool if paired with 12 volt "space charged" tube preamps... Thoughts?
You can check out the TDA2003. Its a 10 watt chip. My little brother has a little generic practice amp that uses it. I had to replace the input jack and checked it out while I was in there. It runs on 12 volts and has provisions for "C" batteries IIRC.
http://www.ssguitar.com/index.php?topic=1212.0
Uses car amp chip,runs on 12-18V and yeah AA batteries about 2 hrs full volume.
The TDA20** series have more info available as far as projects go.
So I have done what your asking and it works great,IDK about the battery from Frys
but that sounds about right,and I could use two of em 8)
Thanks for the confirmation Brymus. That is exactly what I was hoping/expecting. I think that, since I have all the parts and won't have to front any more money, I'm going to start out with the AA route. I have enough rechargeable AA's for two rounds of 6 batts, which would give me about 4 hours of street time (plenty for now). If the amp is working out well and I like the sound, then I may invest the ~25 bucks for the 12volt LA battery upgrade to take the hassle out of the multiple recharges that the AA battery scheme will need. I'll post some pics when I get it together. I'm thinking of using a little hard-sided vintage suitcase for the chassis. It'll have a nice handle and stuff, and IMO will be perfect for this kind of portable amp...
Cheers,
DDC
For maximum efficiency (battery life) you should look into a "class D" amp. The tripath kits from www.41hz.com are quite good. If you've never soldered SMT components before you should go for one of the through-hole kits. The AMP6-Basic is pretty good and gives 2x25W from a single 12V supply.
-Matt
I'm looking at doing the same thing with the 41Hz amp ( http://www.41hz.com/shop/item.asp?catid=42&itemid=43 ) and this little gem:
http://www.spinsemi.com/products.html
http://www.oct-distribution.com/
for a bit on onboard reverb. If anyone has advice I'd appreciate it.
Slimbo, i haven't heard of that chip, but it seems like it would make a great multi-fx pedal! Have you posted it over on the DIY stompbox forum? If not, I might do that for you...
Also, thanks Slimbo and Armstrom for the suggestion to check out the 41hz modules. I've always been curious about those kits, and I'm glad to hear that they are good and long on battery life. They are definite future options for me if the chipamp I have now doesn't work out well for battery operation...
Aha! There is already a kit available for that reverb chip. It's from tonepad: http://tonepad.com/project.asp?id=68 (http://tonepad.com/project.asp?id=68)
Also it seems that second link is to a prebuilt module. That seems by far the easiest route. Looking at the PDF datasheet for the module, it seems like you just connect up power, input, and output, and you are good to go. I'm not sure if there are pots and switches on board, but you'll probably want to wire your own panel mount ones in anyway... Looks like you can use an 8 position single pole rotary switch to select the effect type, and then you need three pots to adjust the effect parameters. Through on a DPDT (or 3PDT) true bypass stomp switch,and your in business! Seems pretty easy, and at $27.50, it's a damn cheap way of getting a sweet multi-fx modulation pedal...
Scratch all that. I was looking at the wrong datasheets. It seems that module has some terminal posts at one end of the board. The first PDF on the page shows how to connect them up. Three pots, and three spst switches, and an LED gives you full functionality. Takes 5-9 vdc (perfect for battery op). Just connect input and output, and a bypass switch if you want, and go. It may have a buffered throughput, but I can't determine that for sure from the datasheet.
Im pretty keen to have a go at it, but want to get some advice before I start, my DIY projects seem to end up tripling the original estimated budget.
The pre made effects board seem to have the eeprom with pre loaded effects, not the factory ones which is a bonus, one of the factory ones is labeled as "test". The advantage of having two channels on the amp means it may be possible to have some kind of mixer and mix a clean signal with an effects one (I think the correct term for this may be wet and dry signals? Or am I thinking of sandpaper?).
I wonder if there would still be a need for a pre amp, or a simple 3 band eq, or a little distortion, or seperate impedance inputs for mike for the harp, and guitar. Also for efficiant speakers, the Fitzmaurice jack 10 might be worth looking at.
http://www.billfitzmaurice.com/Jack.html
Feel free to post at other forums, the more info the better.
I think you are probably going to need a preamp. Looking at the specs of the chip, it doesn't seem that is has any gain, but also doesn't seem like it sucks volume. If it has any internal amplification, it's to mach the level of output signal with that of the input. That way, the chip works fine as a pedal or an onboard effects processor. If i were to use this as an on board effect, I'd probably stick it between the preamp and the poweramp. This would give optimum placement in the signal chain for these kind of modulation effects.
The guitar-oriented patch set does not need a miking circuit afterwards becasue both channels are "wet". It seems that you get two effects at a time in this set. eg. the right channel will be reverb, and the left will be echo, tremelo, flanger, etc. Turning down the left channel will let you get just reverb, and vice versa. In this way you get a TON more effects, but you never get any dry throughput. You'd have to install a true bypass switching arrangement if you wanted to get that (not to hard, but it means you have to get at least a DPDT switch. Toggle for an onboard effect, or a more expensive stomp switch for a pedal) In the factory patch set, one channel is "dry" throughput, and the other is the wet signal. You only get one effect at a time with that patch, but you can always have some dry signal.
On board arrangement would be mcuh cheaper to pull off than the stompbox version because using toggle switches to trigger all the different fx combos and for the bypass will be MUCH cheaper than all the stomp switches you'd have to buy for a stompbox. And you won't have to bother with a separate enclosure and all the extra jacks and stuff. This board just screams to me to be put in an amp as an onboard unit. It would make a cool amp bitchin'! You could also even retrofit it to an existing amp too. How cool would that be?
I don't know if the chip is stereo out, do you mean it applies effects to separate channels then mixes them internally for a mono output?
Re the mike input, I meant there will be different impedance between a guitar and a mike, or is it fairly simple to built a High Z / Low Z switch on the amps input? Maybe it would it be better to have a low Z XLR socket for mikes and separate High Z for the guitar input.
I don't know if I read it wrong but I thought if you have the echo and the reverb level at zero on the pots, you will have a clean signal. But I think you still need to be able to switch between options.
On this link there is schematics for a guitar pedal, http://www.oct-distribution.com/datasheets/SKRM-C8-G01.pdf , they have used a multi op amp chip, there is bypass and what must be volume as well. Also an IC connected to the 8 position switch, I think that IC connects to the EEPROM and not the 3 switches on the main effects chip as the main chip cannot be programmed. So we need another PCB.
I can follow most of the schematic, but what is the opamp with pins 12, 13 and 14 for? Is it just connected up in this way because it is unused?
I have no experience with harp through amps, how essential will eq'ing be? Is it common to cut the highs out for example? And does anyone use distortion?
Edit: http://www.runoffgroove.com/tonemender.html
This site rocks. Hows this for some EQ?
The way I understood it is that the chip IS stereo, but the guitar fx patch set uses both channels for effects (left for reverb, right for other effects), thereby basically creating a "mono" fx box. Here's a quote:
"This is a mono‐in/mono‐out program set perfect for stomp boxes and guitar amp applications.
The output of this set is designed to be used directly and NOT mixed back in with the dry signal."
But if you use the factory patchset, it only uses the left channel for various reverb/delay, leaving the right as throughput dry signal, which you would then have to mix back to the left channel for a mono output.
Yes, it's easy to create a high and lo z input. Look at the fetzer valve article at runoffgroove to see how to do this. You'll need 1/4" jacks that have normally closed switches attached.
In that schemo, it looks like they use the opamp to buffer the input and output. I'm not good at interpreting opamp schematics because I don't ever really use them, so I can't tell if they are getting any gain from it. If the module is supposed to be used as an fx pedal, I would assume they've designed it to have no gain (unity).
Eqing is the heart of designing effects that sound good for harp. You need to cut freq's below 100hz and above 1600hz. Give a bump around 200-400 hz. Usually, you'll need to use higher-than-normal coupling caps (likek 0.1-0.047 uf instead of the standard 0.022 uf) to let more bass through. But you have to change the freq dist at each stage in an overdrive to achieve the best sound. For example, you may need to make the signal overly bright into one gain stage, or else it'll sound muddy. Then, in the next stage, you might have to really cut the treble or else it'll sound tinny... anyway, IMO, proper EQuing through the whole circuit is the main reason an overdrive will sound good for harp...
This looks like a cheap way to get into one of those chip amps:
http://shop.ebay.co.uk/?_from=R40&_trksid=m38&_nkw=Lepai+TA2020+
There are people modding them if you search. I'll have to try to find a circuit diagram.
I think you meant Hz and Khz not Mhz as that would be way beyond the range of any instrument I know of.
The usual HiFi range is 20hz - 20 khz
Just clarifing for others who may not know the difference,
Yeah Brymus, I meant Hz. I edited it to say Hz now. Sorry...
Slimbo, that Lepai amp module looks interesting, and CHEAP! It says class T, that means it's using a Tripath chip. Someone would have to take the plunge to see if it sounds good though.... On e-bay usa, they are going for around $24 with shipping. (http://shop.ebay.com/i.html?_kw=Lepai%20TA2020&_fcid=1&_localstpos=85282&_sc=1&_sop=15&_sticky=1&_stpos=85282&gbr=1 (http://shop.ebay.com/i.html?_kw=Lepai%20TA2020&_fcid=1&_localstpos=85282&_sc=1&_sop=15&_sticky=1&_stpos=85282&gbr=1)) Not a bad price at all for 20 watt X 2 channels, already assembled.
Here's the specs:
Features:
* Tripath power IC.
* Mini size design is good fit for home audio, car,motor bike and other audio device.
* It has flash rainbow light in the front panel and very colorful at night.
* Aluminum alloy case makes it looks more beautiful and good to distribute heat.
* Compact Size: approx. 115mm (D) X 140mm (W) X 42mm (H)
Specifications:
* P.M.P.O: 2X180W
* R.M.S: 2X20W
* Input power:12v 2A DC
* Input sensitivity: 200mv
* Input impedance:47k
* Frequence response: 20Hz-20kHz
* Speaker impedance :4-8ohm
* Minimum THD :<0.05%
* Signal noise to ratio: >100db
* RCA input : 1 slot (mp3/cd available)
Follow this link to see a gut shot. It has an op-amp based preamp, and build wuality looks pretty good! http://cgi.ebay.com/Lepai-TA2020-Class-T-Amp-Mini-Stereo-Amplifier-Adapter_W0QQitemZ290369860539QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439b6473bb (http://cgi.ebay.com/Lepai-TA2020-Class-T-Amp-Mini-Stereo-Amplifier-Adapter_W0QQitemZ290369860539QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439b6473bb)
http://www.diyaudio.com/forums/class-d/90500-lepai-t-amp-ta2020.html
There is a huge 50 page thread on these amps in the DIYaudio forums, adding inductors and higher quality and different value components, bypassing the tone controls etc. One guy had a hand drawn schematic which I neglected to save. I don't think these chip amps can be paralleled or bridged, so I'm thinking the best way to set this up is send the same signal to both input channels and connect 2x8" drivers. I have ordered one, hopefully it will be here next week.
I think at the start I will experiment with the gear I have before trying out that reverb PCB from OCT Distribution, though I did email them and they answered and said they will be happy to freight one to me overseas, so that's excellent. Always good when a company replies like that, thanks OCT.
I have a Sure SM58, never tried harmonica through it, (any comments on the suitability of this welcomed), I will run it through a Sansamp Bass Driver to the amp.
I have also found a 12V 4AH SLA battery. I need to find out what voltage this puts out at full charge, because I think some guys had blown the chip from running of a charging car battery at just above 14v.
I also wonder if 4AH will be enough, at full noise drawing 2 amps we get around 2 hours? How will the battery like that kind of power draw?
So many questions!
Thanks for that link! It's a lot of reading, but I will definitely skim through that... Yes, the way to go is to split the input signal, and send it to both channels. Best is to have some small series resistance on each channel input after the split (1kohm on each leg of the split will do). Then send the output of each channel to it's own speaker. If it's truly 2x20watts, then doing it this way, the amp will be putting a full 20 watts through each speaker, making about as loud as a 40 watt amp. The amp will be loud, anyway.
Yes your sm58 will sound AWESOME for harp. It's own of the go-to dynamic mics that pros use (that and the sm57). It won't sound like a bullet mic (they use ceramic or crystal elements), but IMO, you are better off with a dynamic mic for a solid state amp anyway. Especially if you are using that Sansamp first. It will let you get any kind of sound you want. Should be a killer harp rig!
I do not know too much about the battery stuff. That's why I started this thread, actually... I'm pretty sure that class T amps draw MUCH less power than other chip amps of comparble wattage, so you might get quite a few hours out of it. Remember that you are not going to be blasting at full volume all the time, so you should be able to get a bit more time than the math tells you when calculating with peak values. Using RMS power consumption values should get you a closer estimate. Given what I've been able to learn about batteries, that one you picked sounds like it will work fine. I'm not sure what kind of power supply circuitry one should use for battery operation. I suppose at minimum, some small series resistance (100 ohms?) and at least one large cap to ground (about 100uf or so) couldn't hurt. Make sure these are rated for reasonably high power. Prob 1 or 2 watts for the resistor, and at least 20 volts on the cap. Someone else can better answer these questions though...
Here's a link to the announcement and discussion of that sweet octoboard reverb module from diystompboxes. My comments and replies from Frank are at the end:
http://www.diystompboxes.com/smfforum/index.php?topic=79388.0 (http://www.diystompboxes.com/smfforum/index.php?topic=79388.0)
I now have the amp, it is a small circuitboard and wont take up much room at all. Next step is to decide what size and how many speakers. I need 2, one for each channel, and I'm thinking 8" drivers, but this is only based on "I seem to recall reading that a few well known harp players prefer 8's". Their size and weight fits the design criteria, as long as they sound good. I think Adam Gussow talks about his combo's, one tube, one SS, both with 8's in his 2nd youtube lesson, but I may be wrong. I think the best design I have seen is on Bill Fitzmaurice's site with the fairly new XF Guitar Cabs.
Link here:
http://billfitzmaurice.net/XFCabs.html
The smallest is 2x10", I asked on the forum regarding the possibility of scaling it down for 8's. Bill replied "You can, though it will take quite a bit of graphics design skill to do so." My graphic design skills are high school geometry, but if its just a matter of getting the 4 angles correct on the speaker surround parts I think I could eventually figure it out, and scaling down the rest of the box will be easier, good enough for prototype purposes. All this should be ok as long as Im not missing some very crucial points, like the lengths of the inside dimensions cant be the same as the 1/4 wavelength of the 8th harmonic, or the change in box volume will mean the formally crystal clear highs will now sound like mud.
edit: check this out, very interesting. Open back, sealed, or ported?
http://www.webervst.com/sptalk.html
Cool keep the updates coming.
Yes, we use 8" speakers because they break up quicker (ie. at lower volume) plus they aren't too bass heavy. I use speakers salvaged from old electronics. So far, the best I've found are 8" speakers from old organs. Great Tone! Some people report that the cheap Jensen MOD series 8" sound good for harp, and others will swear by Webers. I get my vintage speakers for about $5-10 bucks each, versus ~$25 for the cheapest new speakers, but you definitely will have to put the time in and search around to find those old drivers. Read the reviews of various speakers at this blog: http://bluesharpamps.blogspot.com/ (http://bluesharpamps.blogspot.com/) He reviews both Jensens and Webers, and is thought to be a reliable source.
And yes, Adam mentions the 8" speakers in that vid.
I found a reply direct from Adam from his own Modern Blues Harmonica forum where he discusses why he likes smaller speakers for harp:
Isaac:
The only thing I need to add to your interesting post is that some of the distortion--for the best overdriven amp sound, I mean--needs to come from the speaker cone. It's generally easier to get this from smaller speakers (6", 8", 10") rather than larger speakers (12", 15"), but the key thing is that the magnets need to be relatively small. A Hartke 4 x 10" bass speaker cabinet will sound like crap for harp because the speakers have huge magnets, precisely so that they WON'T distort when you're running loud low frequencies through them.
Amplified harp sounds best when the various sorts of overdrive--preamp, power amp, speaker--accentuate a certain high-mid frequency range. One reason old tube amps sound great, I suspect, is because they (ideally) have original speakers, with old paper cones. I remember playing through a tweed Champ, mid 50s, with the original speaker. Incredible sound.
I have two Mouses. They're identical, except that one has a plain capped speaker and the other has a speaker with a projecting lip of some sort--about 1" high. A mini-loudspeaker coming off the cone. Much, much better sound.
I didn't know that the ideal in a solid state amp, for harp, is to overdrive the preamp but not the power amp. That's interesting.
Very interesting, thanks for that. So it may be a matter of starting a speaker collection and swapping them around untill the best sound is found.
I have been thinking a lot about the sound I want out of the amp, but I only have what I have heard on YouTube and downloaded mp3's to go off. I purchased a few of Adams lessons, I have downloaded a lot of the YouTube ones of Adams and Jon Gindick, and I have instructional material with cd's, my favourite being Brendon Power's "Play Irish Music on the Blues Harp". From these examples, I prefer the "clean" sound of the harps. When Adam demonstrates a technique, then plays it through an amp, it sounds harsh and grating. I am certain the little mike he may be using when recording the lessons is not doing the sound justice and it sound a million times better in real life, but I still like the sound of a undistorted harmonica. I think the amp should have the ability for a bit of overdrive, but I dont know if it is going to be as important in this amp as it would be in a amp designed for electric guitar. I kindoff pictured this amp would be used with acoustic guitar more that electric, maybe some electric bass (only because I already play bass, not sure how it will handle low frequencies).
Anyone care to comment on the need for distortion, and how much, for harp?
The best solid state harp amp I have currently is one I constructed from an old radioshack PA amp I bought for $8 at the Goodwill. It's a "Realistic" brand, model number MPA-20. Very importantly, it's an older one, and the circuitry is 100% discreet (ie. it uses power transistors in the poweramp section, not a chipamp). The newer MPA-20's use a chipamp, and don't sound nearly as good. The only modification I did was to remove the "phono" section (I'm not feeding it input from a record player!), and to change how the negative feedback loop get's tapped to the output transformer. Originally, the NF loop was connected to the 8ohm tap of the OT. I removed this tap, and added two new leads, one to the 16ohm and one to the 4ohm tap of the OT. I made it switchable. When you go to the 4ohm position, it get's crunchy and breaks up early. It's also a bit louder. When you go to the 16ohm tap, it's a little quieter, but MUCH cleaner, even cleaner than it originally was. Both settings have their purposes, and I think both sound really good. This amp also has two input channels (with two separate pre's and two separate volume controls), so it's a really versatile amp. I can plug both harp and guitar into it, or harp and a footdrum (porchboard). BTW, this amp also sounds killer with my cigar box guitar (it's an acoustic with a piezo pickup).
I built this PA into a custom cabinet I threw together with singe 25 watt 8" paper-cone speaker with a smallish magnet. It's one of a pair that came from an old organ. The BEST harp speakers that I've ever found.
Anyway, the point of all this is to say that PA amps are a really great place to look for nice solid state Harp amps. PA amps have been used for years for harp (eg. look how everyone loves those old Bogen PA heads), and a nice solid state one will work as well or better than a tube one. That amp you are buying (the Lapai) is basically a PA amp. I'm not very familiar with those tripath chips, but everyone seems to think they sound good for instrument amps. You are probably on the right track. If you don't get THE sound you want out of it at first, then you'll need to start experimenting with Preamp circuits until you find one that works well with that particular chip. I suggest starting with something like the Fetzer Valve or the Tillman pre (both very simple one-transistor designs), and then move on to something like the Peppermill or Blue Magic (relatively simple two-transistor designs). Any of these preamps should let you dial in a relatively clean tone, or get a nice mild overdrive.
Thank for the tips re preamps. If I can do overdrive easily and keep it cheap, no reason not too.
I have wired the amp to a 4Ah 12v SLA battery, it arrived charged from new, I havent used it long enough to comment on how long it will power it for. I hooked a Onda mp3/4 player and it sounded terrible. Distorted and not loud at all, nowhere near the volume needed for an amp that will do some outdoor work. I then tried a laptop as a source and what an improvement, the amp sounds pretty good, actually really good. With the mods the guys are doing in the link in my early posts, this would be one sweet hifi amp. Tone controls are not great, but they can be improved. It has run for maybe 5 hours at low volume at work here and the battery has dropped maybe 0.2V, to around 12.6. No heat that I can feel anywhere in the amp, the laptop power supply is warm. So a very positive first impression, I think this amp will be up to the task.
Next step it to hook a mike up to it. I have also found a delay pedal so I may get some idea what the reverb will sound like. What is the difference between delay and reverb anyhow?
Stay tuned, and please post comments.
Edit: I'm answering my own questions. Does it get any sadder than talking to yourself on an internet forum? Anyhow, http://www.harmony-central.com/Effects/effects-explained.html
Good to know that the amp is working! Sounds like you will definitely need a preamp though, and perhaps one with significant gain. Maybe even a lm386-based one? I know Armstrom on this form had success building a harp amp with a lm386-based pre. Look for the "smokey", "Ruby", "little gem", and "noisy cricket" schems. Those'll do ya well.
I think the best choice will be the one that has the most tone shaping. The Noisy Cricket Mk II looks like the leader with a grit switch, gain, volume and tone. Smokey's got gain and a tone switch, Ruby's and Little Gem have volume and gain pots. I have had my eye on the Tonemender as well, so naturally I searched for it in this forum and found an improvement, the PhAbbTone box, by the username phatt. Might have to breadboard a few.
one thing to keep in mind is that the LM386 won't break up as nicely at high voltages unless it's driving a low impedance load like a speaker. If you run the output directly into the input stage of a power amp (which is usually on the order of 10-50K ohms rather than the typical 4-16 ohm speaker impedances) you should lower the supply voltage to ensure you get good breakup if that's what you're after. The datasheet provides plots of the maximum output voltage swing vs. supply voltage for various loads. Unless you're driving a speaker you want to look at the plot for infinite load. To mimic the kind of clipping (maximum output swing) you would get when driving an 8ohm load with a 12V supply you will need to lower the supply voltage to about 7.5V. Of course, you could also add an 8ohm resistor to ground on the output to simulate the load as well. I did not try that with my setup though.
Quote from: Slimbo on December 07, 2009, 08:18:58 PM
I think the best choice will be the one that has the most tone shaping. The Noisy Cricket Mk II looks like the leader with a grit switch, gain, volume and tone. Smokey's got gain and a tone switch, Ruby's and Little Gem have volume and gain pots. I have had my eye on the Tonemender as well, so naturally I searched for it in this forum and found an improvement, the PhAbbTone box, by the username phatt. Might have to breadboard a few.
Check out my TDA1519b practice amp,it uses a lm 386 in the pre amp for its clipping behavior.
And went from a Dr Z tone control to a Marshall TMB in the last version.
Be sure you read the 386 data sheets and get the lowest power one (325 milliwatts)
I use that pre amp for tone shaping as a pedal in front of my other amps too.The last version can get any sound from chimy clean to over the top gain.
Think of it like a TubeScreamer feeding a Marshall tonestack feeding a Distortus Maximus.
And you have an idea of the gain available.
QuoteAnd went from a Dr Z tone control to a Marshall TMB in the last version.
Is this the Marshall TMB?
http://i419.photobucket.com/albums/pp276/Bry928/SolidState%20Amps/12Watt-TDA1519B%20build/386PreAmp_2.jpg