Hey all,
I’m looking for some advice on building a power amp that will be used for guitar.
I have some preamps as well as a Helix for more preamps.
I would like to build a solid state power amp to push guitar speaker cabinets. Specifically a 16 ohm 1x12 cabinet. I also play in a rather loud band. The other guitarist uses a Fender Mustang for 100 and the bassist uses a 500 watt Bass amp
I have looked at the variety of class d modules. ICEPower modules with built in power supplies seem like a no brainer, but I have come across a few Class AB kits that have my attention. I got into building pedals in 2020 so the idea of building the amplifier myself from parts sounds fun. I also don’t know how well they work/sound at 16 ohms. The specs usually say 4-8ohm load.
The kits that I am looking at:
LM3886 x3 150w
TDA7294 BTL/Stereo
SKP GB150D Mosfet
I’ve also seen PCBs for Current Feedback amplifiers which I’ve read were used a lot in solid state guitar amps in the 80s and 90s.
Anyway, I’m looking for advice on what might be the best choice for a first time build.
Thanks,
Trav
I’m looking for some advice on building a power amp that will be used for guitar.
I have some preamps as well as a Helix for more preamps.
I would like to build a solid state power amp to push guitar speaker cabinets. Specifically a 16 ohm 1x12 cabinet. I also play in a rather loud band. The other guitarist uses a Fender Mustang for 100 and the bassist uses a 500 watt Bass amp
I have looked at the variety of class d modules. ICEPower modules with built in power supplies seem like a no brainer, but I have come across a few Class AB kits that have my attention. I got into building pedals in 2020 so the idea of building the amplifier myself from parts sounds fun. I also don’t know how well they work/sound at 16 ohms. The specs usually say 4-8ohm load.
The kits that I am looking at:
LM3886 x3 150w
TDA7294 BTL/Stereo
SKP GB150D Mosfet
I’ve also seen PCBs for Current Feedback amplifiers which I’ve read were used a lot in solid state guitar amps in the 80s and 90s.
Anyway, I’m looking for advice on what might be the best choice for a first time build.
Thanks,
Trav
https://jimsaudio.com/mosfet-150w-power-amplifier-gb150d-partial-kit-matched-input-out-bjt-mosfet/
this would be my pick if these where my "only" choices...got to ask why solid state??
seems to me it would be easier and more economical to find an old tube chassis and gut the preamp or transplant the bits you need to a new chassis, an old JMP head would have an output transformer that has a sixteen ohm tap so no impedance worries.
Fender Mustang amp? a quick search only turned up a 25 watt model so are you certain about your other guitarist's amp being a 100 watt output?
this would be my pick if these where my "only" choices...got to ask why solid state??
seems to me it would be easier and more economical to find an old tube chassis and gut the preamp or transplant the bits you need to a new chassis, an old JMP head would have an output transformer that has a sixteen ohm tap so no impedance worries.
Fender Mustang amp? a quick search only turned up a 25 watt model so are you certain about your other guitarist's amp being a 100 watt output?
Given you have a single 16 ohm speaker (Brand? Model?) that limits power big time
3886 will give you some 30W RMS, 7294 slightly higher, none is suitable in your loud band.
Zero details on your links, only board pictures, no schematics, no power supply details (most important), but the 150W MosFet could do it.
Which means 150W into 8 or 4 ohms, doubt you get more than 60-70W at best into your 16 ohm speaker.
Mustangs come in all sizes, up to 150W; your friend uses the 100W version, you must at least match that, none less.
Personally I would suggest the Ice power board: enough power, solves the PSU problem; you will still have lots of work and fun getting and drilling a chassis, making (maybe even tolexing) a case for it, mounting all hardware and board inside, input and speaker jacks, mains connectors, etc.
It is definitely not "plug in" by any means.
Please keep us updated.
Note: don't worry about constant current output.
It is not "magic", it just adds a little extra EQ by interacting with speaker wonky impedance but you don't need it, all preamps and simulators you mention already include some *speaker cabinet" emulation, just pick the one you like.
3886 will give you some 30W RMS, 7294 slightly higher, none is suitable in your loud band.
Zero details on your links, only board pictures, no schematics, no power supply details (most important), but the 150W MosFet could do it.
Which means 150W into 8 or 4 ohms, doubt you get more than 60-70W at best into your 16 ohm speaker.
Mustangs come in all sizes, up to 150W; your friend uses the 100W version, you must at least match that, none less.
Personally I would suggest the Ice power board: enough power, solves the PSU problem; you will still have lots of work and fun getting and drilling a chassis, making (maybe even tolexing) a case for it, mounting all hardware and board inside, input and speaker jacks, mains connectors, etc.
It is definitely not "plug in" by any means.
Please keep us updated.
Note: don't worry about constant current output.
It is not "magic", it just adds a little extra EQ by interacting with speaker wonky impedance but you don't need it, all preamps and simulators you mention already include some *speaker cabinet" emulation, just pick the one you like.
You could drive it in bridge tied mode with 3886 or 7294.
That will give you 2x the single ended 8 ohm power.
Those might not be the only choice, just some that I came across.
The main reason I would go solid state over tube is:
1. Less expensive - power tubes and output transformers would be $200- $300 on their own.
2. Less dangerous - Most ss power amps are running under 100v. Tube amps can be in the 700v range at the power section
3. More reliable/less maintenance. In my experience, its hard to kill a well-built solid state amp. My Peavey Bandit is from 2002 and it has had zero problems and hasn't needed anything other than a cleaning.
4. It would probably be easier to build from scratch than repurpose something.
I would love to build my own tube power amp, but it would almost make more sense to just build a full amp, which defeats the purpose of using other gear that I want to use.
This is the amp he uses Fender Mustang GT100
The speaker cabinet is a Victory 112 cabinet with a Celestion Creamback 75 watt speaker.
In the links I provided they do not include the schematic but they all state the topology.
3 (three) 3886 chips in mono - 150w @8ohms (not sure the noise/distortion level) but that would be about 75 watts @ 16ohms (maybe more depending) at +/- 36 volts.
The 7294 example uses 2 in BTL: 180W@8ohm BTL, 60W@8ohm,0.1% THD stereo. So, 90watts BTL@16ohm.
I understand the idea that I need to match his wattage, but he isn't maxed on the volume. I think 75 watts could match volume. I could also run an additional 16ohm cabinet and put myself at 8ohm and gain the additional db that come with adding a second speaker (2db?)
ICEPower modules are definitely on the radar, since I can grab their mono 200 watt board for $130 from Parts Express. I think that I just want to make things hard on myself.
The kits listed are around $40. I assume I would need a power transformer and not a switching power supply? I assume (perhaps wrongly) that the PT would last longer than an smps. So, probably a bit more expensive.
I am actually happy to design and drill myself. I drill all of my pedal enclosures. Its part of the fun.
I just don't know much about wiring up transformers but I'd rather learn on something with lower voltages.
No idea how that can be.
Three chips paralleled can still only provide max supply voltage minus a few volts peak. For the suggested supply at 36 V that's max estimated 24 V rms output.
Translates to 72 W at 8 ohms.
Jeez - sounds like a steal. People on ebay want the better part of that for an empty wood enclosure for a 12"...
Excellent advice, as the power supply is a significant "problem", as far as problems go. Always has been, always will be - in any industry. There are challenges when stepping into this territory and if you can eliminate a big one for just $50 more, you'll thank yourself later for money well spent.
It'd be some old tube chassis to stumble upon and get the 100W of power he's looking for. A quad of something running high voltage, high current - better make use of that standby switch between sets - I'd bet for every one that's stable until the tubes die, there's a dozen more "old tube chassis" high power designs that'll blow up at the drop of a hat. A HiWatt STA 100 doesnt count as an old tube chassis, because even though it's old, tube - it's nearly $2000!
That is an interesting point that I didn’t think about.
Should I consider something capable of higher output power so that I’m not reaching maximum range?
My biggest concern there is blowing my 75 watt speaker
Absolutely!
It sounds like an ICEPower board is the smartest choice.
Without opening a different and more controversial can of worms, I am still interested in building a class ab amplifier
Ask Mr Fahey about that - he swears by them for musical instrument amplification.
Chips make practical 20 watt guitar amps. They do not make practical 60-100 watt guitar amps. Too much thermal load through one small package (or two if you’re bridging trying to get that 100 watts) and the end result is something running hotter than it needs to.
@wg_ski What would be a better solid state alternative?
I believe Orange Amplifiers uses TDA7294 for their CR120 and Super Crush 100 amps. I've never heard of one failing. I'm sure it happens, but there are lots of them in the wild. The CR120 is set to only be used for 8-16ohm and according to their claims, its set up so that the same output power is applied at both 8 and 16ohm. The Super Crush states a power reduction when using 16 ohm.
My Peavey Bandit uses 2N3055 / MJ2955 combo. I believe it is 100watts@ 4ohm/ 80watts@ 8ohm (somehow).
I am open to alternatives. I'm also okay with just buying a PCB as long as I can find everything I need (power supply).
I believe Orange Amplifiers uses TDA7294 for their CR120 and Super Crush 100 amps. I've never heard of one failing. I'm sure it happens, but there are lots of them in the wild. The CR120 is set to only be used for 8-16ohm and according to their claims, its set up so that the same output power is applied at both 8 and 16ohm. The Super Crush states a power reduction when using 16 ohm.
My Peavey Bandit uses 2N3055 / MJ2955 combo. I believe it is 100watts@ 4ohm/ 80watts@ 8ohm (somehow).
I am open to alternatives. I'm also okay with just buying a PCB as long as I can find everything I need (power supply).
When I was a development engineer designing the proprietary Nextel walkie talkie phones, we had sales engineers for all of the major chip companies circling our plant like flies on horse poop. The National Semiconductor guy was particularly generous with samples, and quite knowledgeable about their products. The kid that lived next door to me has a little Peavey guitar amp which he had blown up twice. I was about to replace the output chip a third time when I went to the National guy, gave him the type number, a TDA2002 I think, and asked for something that would drop in and not blow no matter how many speakers he connected to it. I don't remember the number of his magic chip, but it lived.
This action led to a discussion about guitar amps. He agreed to get me all the chips I needed as long as I built one for hid kid too. He got me some samples of a new chip, the LM3886, along with some SPI controlled EQ chips, some HiFi preamp chips and several different flavors of opamps. I wound up making three guitar amps. They made about 50 watts into a 12 inch 8 ohm speaker. None of these amps ever blew up. The kin next door wound up getting an electrical engineering degree and a job at the Motorola plant where I worked. About a year later he got a better job with one of the big cellular companies (AT&T I think) and left south Florida. I gave him the LM3886 guitar amp that I had made. I still have a stick full of those old National 3886 chips.
This action led to a discussion about guitar amps. He agreed to get me all the chips I needed as long as I built one for hid kid too. He got me some samples of a new chip, the LM3886, along with some SPI controlled EQ chips, some HiFi preamp chips and several different flavors of opamps. I wound up making three guitar amps. They made about 50 watts into a 12 inch 8 ohm speaker. None of these amps ever blew up. The kin next door wound up getting an electrical engineering degree and a job at the Motorola plant where I worked. About a year later he got a better job with one of the big cellular companies (AT&T I think) and left south Florida. I gave him the LM3886 guitar amp that I had made. I still have a stick full of those old National 3886 chips.
Rod elliott's guitar amp project may be interesting, although it may not provide very high power at 16 ohms:
http://sound-au.com/project27.htm
Keep in mind that double power will only provide +3 dB output (probably less because of thermal compression). That's just noticeable by ear. speaker sensitivity is where you can usually gain much more!
http://sound-au.com/project27.htm
Keep in mind that double power will only provide +3 dB output (probably less because of thermal compression). That's just noticeable by ear. speaker sensitivity is where you can usually gain much more!
That's some good karma right there. I'd say you had an influence, anyway. I once bought a girlfriend's kid a 286 mobo with 512k; the guy I got it from said "watch his eyes light up when it boots windows". His mom later told me he's so quiet; hardly left his room. Sometime later I heard he got an EE degree. I'll never know, but they say sometimes all it takes is a "moment" of kindness or a little bit of a stretch like that.