Greetings all, I'm in need of some advice on which amp to build. I'v perused dozens of threads and examined more options than I can recall, but I don't yet feel confident on which one to choose. Here's my predicament: the amp will be powering 8Ω speakers that aren't sensitive (~83dB/W). Since money is tight, I first thought I'd build a chipamp. But given my speakers' lack of sensitivity, I wasn't convinced 60W will get me to the SPL I'd like to be able to achieve. I don't often play music loud, but I'd like the option to do so, plus I like having the headroom even for quieter sessions.
So then naive me thought I'd get one of the parallel chipamps for not much more money! However, I quickly learned that running chipamps such as the LM4780 in parallel will do me no good, since I'm running in to 8Ω. So now the options that lie before me are pretty much all more expensive and complicated. Since I only have enough discretionary funds to build one amp, I'd really like to get it right the first time (and by "right" I mean "satisfying my wish for enough power, high fidelity, and not too expensive").
Before detailing the options that I'm aware of (and thus asking for your vote, advice, further suggestions, etc.), let me just ask: am I wrong to think a 60W chipamp won't be enough power? Because if it is, then I'll save myself quite a bit of time and money and just do that. I know it's probably hard to answer that question, given the amount of detail I've left out (in the interest of brevity), so I'm happy to fill in more details if you want them.
With that said, here are my non-chipamp options, as I see them:
1. ESP Project 101: I've been drawn to this project from the beginning of my search, because it promises high power and high fidelity (Rod says as much, and there are many great reviews out there as well). The biggest drawback here is cost. Since I don't have the BOM, I don't know the exact cost, but my educated guess is that it'll be ~$150 just for the PCB and components (not including transfo, PSU, enclosure, binding posts, etc.). I was hoping to be under $100, if possible. I know I know, I'm cheap!
2. Honey Badger: like ESP P101, plenty of power, but even more complicated and more expensive. There are lots more amps like the Honey Badger (plenty of power, but more complicated and more expensive), so I'll just lump them all under this listing. That is to say, I'd only consider these options if given very compelling reasons to do so.
3. ESP Project 3A: Rod recommends the lower rail voltage, which only gets you 60W. However, there is the option of a (riskier) higher rail voltage that gets you 90W into 8Ω. Does anyone have any experience doing so? Even with the risk of damage, I'm still coming out WAY ahead in terms of price, as the PCB and components is only ~$40. Granted, 90W isn't much gain over 60W (Rod states it is only an increase of 1.8dB, which confused me: my calculations show an increase of 3.5dB). But even doubling up and running a balanced signal into bridged P3As gets me 200W for only $80.
However, that leads me to another set of questions: can I just use one of these to transform the SE signal to a balanced one? Do I then connect the source ground to the ground input of both amps? And what do I do with the ground output, since the binding posts are now connected to each amp's output? Does this change how or whether one connects to a speaker protection unit? And how does one calculate the wattage of a bridge amp — is it just double the output for 4Ω load (since mine are 8Ω)?
Apologies for the long post, but after months of trying to learn the answers on my own, I've concluded I just need to humbly ask you all! I pray you don't pity me too much, with my simpleton questions. Many thanks~
So then naive me thought I'd get one of the parallel chipamps for not much more money! However, I quickly learned that running chipamps such as the LM4780 in parallel will do me no good, since I'm running in to 8Ω. So now the options that lie before me are pretty much all more expensive and complicated. Since I only have enough discretionary funds to build one amp, I'd really like to get it right the first time (and by "right" I mean "satisfying my wish for enough power, high fidelity, and not too expensive").
Before detailing the options that I'm aware of (and thus asking for your vote, advice, further suggestions, etc.), let me just ask: am I wrong to think a 60W chipamp won't be enough power? Because if it is, then I'll save myself quite a bit of time and money and just do that. I know it's probably hard to answer that question, given the amount of detail I've left out (in the interest of brevity), so I'm happy to fill in more details if you want them.
With that said, here are my non-chipamp options, as I see them:
1. ESP Project 101: I've been drawn to this project from the beginning of my search, because it promises high power and high fidelity (Rod says as much, and there are many great reviews out there as well). The biggest drawback here is cost. Since I don't have the BOM, I don't know the exact cost, but my educated guess is that it'll be ~$150 just for the PCB and components (not including transfo, PSU, enclosure, binding posts, etc.). I was hoping to be under $100, if possible. I know I know, I'm cheap!
2. Honey Badger: like ESP P101, plenty of power, but even more complicated and more expensive. There are lots more amps like the Honey Badger (plenty of power, but more complicated and more expensive), so I'll just lump them all under this listing. That is to say, I'd only consider these options if given very compelling reasons to do so.
3. ESP Project 3A: Rod recommends the lower rail voltage, which only gets you 60W. However, there is the option of a (riskier) higher rail voltage that gets you 90W into 8Ω. Does anyone have any experience doing so? Even with the risk of damage, I'm still coming out WAY ahead in terms of price, as the PCB and components is only ~$40. Granted, 90W isn't much gain over 60W (Rod states it is only an increase of 1.8dB, which confused me: my calculations show an increase of 3.5dB). But even doubling up and running a balanced signal into bridged P3As gets me 200W for only $80.
However, that leads me to another set of questions: can I just use one of these to transform the SE signal to a balanced one? Do I then connect the source ground to the ground input of both amps? And what do I do with the ground output, since the binding posts are now connected to each amp's output? Does this change how or whether one connects to a speaker protection unit? And how does one calculate the wattage of a bridge amp — is it just double the output for 4Ω load (since mine are 8Ω)?
Apologies for the long post, but after months of trying to learn the answers on my own, I've concluded I just need to humbly ask you all! I pray you don't pity me too much, with my simpleton questions. Many thanks~
Honeybadger comes with a circuit board, in kit form with parts. What's complicated about that? You need the power, my 8 ohm speakers are 101 db@1w1m. I get away with 35 W/ch, you need more. You need at least 2 output transistor pairs with that speaker. I listen at 1.5 vpp in my music room, but the cannon shot peaks on 1812 overture need to be about 40 v to be musically correct.
Get a transformer from antekinc.com, some 4700 filter caps fuse holder fuse wire coupla 3 amp 100v rectifiers from farnell, some heat sink from heatsinkamerica down in the vendor forum. You need a WP35 iron, some tin/lead rosin core solder, safety glasses, a 3 mm tap & drill, for mounting transistors on heat sink, some 3 mm screws & nuts for screwing things down. A couple of rca jacks and a screw terminal strip or pair of 1/4 phone jacks, some heat sink compound, some to3p mica insulator kits, also farnell. You need a DVM for problems. I'd use a metal file cabinet (12x12x12) for a chassis. you need a drill & stanley carbide hacksaw to cut holes for the heatsink connectors etc. You need some drilled dowel or 1/4 air tubing cut up for standoffs from the metal. I cut fuse holder holes with a 3/8 drill then file out of round with a rat tail file for the D shape.
You should be able to get all that in 3 boxes for $10 freight a box, $30, a significant expense if you don't live in LA, SF, or Boston near a Fry's.
I'd pick the rail voltage specified in the honeybadger build document, wasn't it +-50 or something? 400 w is not much louder than 100.
Be sure to measure the DC offset of speaker terminal before attaching your expensive speakers. I'd buy some trash speakers at goodwill/salvation army/stvincetdepaul for testing until you've got it warm once. If your feeling flush get the diyaudio speaker protector board in the same box. I personally believe the relay contacts will cause problems about 5 years age, but something more sophisticated takes some build it yourself boards.
If you want an adventure in 1 box, buy a blown Peavey CS800s, CS800x, or Cs600s, on craigslist. And fix it. They have microprocessor speaker protection using current transformers, something that is way difficult to do it yourself IMHO. You'll have more shipping costs, but you'll know more when your done. I didn't need a scope, just a dvm & an analog meter with a 2 vac & 20 vac scales.
Have fun.
Get a transformer from antekinc.com, some 4700 filter caps fuse holder fuse wire coupla 3 amp 100v rectifiers from farnell, some heat sink from heatsinkamerica down in the vendor forum. You need a WP35 iron, some tin/lead rosin core solder, safety glasses, a 3 mm tap & drill, for mounting transistors on heat sink, some 3 mm screws & nuts for screwing things down. A couple of rca jacks and a screw terminal strip or pair of 1/4 phone jacks, some heat sink compound, some to3p mica insulator kits, also farnell. You need a DVM for problems. I'd use a metal file cabinet (12x12x12) for a chassis. you need a drill & stanley carbide hacksaw to cut holes for the heatsink connectors etc. You need some drilled dowel or 1/4 air tubing cut up for standoffs from the metal. I cut fuse holder holes with a 3/8 drill then file out of round with a rat tail file for the D shape.
You should be able to get all that in 3 boxes for $10 freight a box, $30, a significant expense if you don't live in LA, SF, or Boston near a Fry's.
I'd pick the rail voltage specified in the honeybadger build document, wasn't it +-50 or something? 400 w is not much louder than 100.
Be sure to measure the DC offset of speaker terminal before attaching your expensive speakers. I'd buy some trash speakers at goodwill/salvation army/stvincetdepaul for testing until you've got it warm once. If your feeling flush get the diyaudio speaker protector board in the same box. I personally believe the relay contacts will cause problems about 5 years age, but something more sophisticated takes some build it yourself boards.
If you want an adventure in 1 box, buy a blown Peavey CS800s, CS800x, or Cs600s, on craigslist. And fix it. They have microprocessor speaker protection using current transformers, something that is way difficult to do it yourself IMHO. You'll have more shipping costs, but you'll know more when your done. I didn't need a scope, just a dvm & an analog meter with a 2 vac & 20 vac scales.
Have fun.
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Hi,
What are the speakers ? Sensitivity doesn't tell you about power handling.
FWIW I'd always derate an amplifier by half for driving real speakers,
i.e. for 8 ohm reactive speakers design an amplifier that works into
a 4 ohm resistive load, this is especially true for chipamps and
their generally invasive protection modes. Two chips give you
the bonus of of much better use of the chosen heatsinks too.
rgds, sreten.
What are the speakers ? Sensitivity doesn't tell you about power handling.
FWIW I'd always derate an amplifier by half for driving real speakers,
i.e. for 8 ohm reactive speakers design an amplifier that works into
a 4 ohm resistive load, this is especially true for chipamps and
their generally invasive protection modes. Two chips give you
the bonus of of much better use of the chosen heatsinks too.
rgds, sreten.
I'm surprised to see no mention of a bridged chip amp configuration. With 8 ohm speakers, each amp would see 4 ohms. If your transformer has enough grunt, you can get well over 100W to your speakers. That said, the expensive parts are always the big pieces. The power supply, including transformer and filter caps, and the enclosure, will dominate the cost.
Hi,
YMMV but I don't trust specs into resistive loads, and for certain a
speakers impedance rating does not equal the same resistive load.
(Though you could argue it should, it generally simply does not.)
With chipamps there is good mileage in designing a parallel amplifier
for a 4 ohm resistive load for use with 8 ohm speakers. IMO it cannot
be said that chipamp bridging is a good idea, except for car audio.
rgds, sreten.
*Start* with a 60W/ch chipamp, actually build and enjoy it, you'll be surprised at how good and loud it can be.
If not enough (which I doubt) , next step isnot, say, 100W/ch, which is just a couple dB higher, but *serious* power, think 180 to 300W/ch ... which in any case I doubt your speakers will stand.
So in a nutshell: build what you *cab* build, which is quite good already, and if later you want Rock concert levels, build serious power amps driving Pro/PA type speakers , they are *designed* to take anything you can throw at them and crack the walls and ceiling.
If not enough (which I doubt) , next step isnot, say, 100W/ch, which is just a couple dB higher, but *serious* power, think 180 to 300W/ch ... which in any case I doubt your speakers will stand.
So in a nutshell: build what you *cab* build, which is quite good already, and if later you want Rock concert levels, build serious power amps driving Pro/PA type speakers , they are *designed* to take anything you can throw at them and crack the walls and ceiling.
Thanks for the replies, everyone. Quick responses:
indianajo: By "complicated" I mean "more parts," which usually means more cost and more opportunities for mistakes (especially for someone without much experience). The rest I'm good with.
sreten: Very true, but power handling shouldn't be a problem. I think my max SPL will be lower than the power handling of the drivers.
mjurban: The problem with bridging into a chipamp is heat, or so I read. So I'd rather use four 3886's than 2 4780's, but then the price becomes commensurate with a discrete amp. Kinda loses its appeal.
minek: Perhaps for you, but $20 for me is something I must consider. I got my enclosures for free, and the rest is pretty much a fixed cost no matter amp I build. So my only opportunity to manage costs is PCB + components.
ostripper: I'd be remiss if I didn't say "thanks" for designing the HB! But I can't see where you got $100 for the amp. I costed the BOM at $80/channel, not including the PCB.
JMF: I would love to start with a chipamp and see how it goes, but as I said I can't afford to build it and then discover I need more power.
Cheers~
indianajo: By "complicated" I mean "more parts," which usually means more cost and more opportunities for mistakes (especially for someone without much experience). The rest I'm good with.
sreten: Very true, but power handling shouldn't be a problem. I think my max SPL will be lower than the power handling of the drivers.
mjurban: The problem with bridging into a chipamp is heat, or so I read. So I'd rather use four 3886's than 2 4780's, but then the price becomes commensurate with a discrete amp. Kinda loses its appeal.
minek: Perhaps for you, but $20 for me is something I must consider. I got my enclosures for free, and the rest is pretty much a fixed cost no matter amp I build. So my only opportunity to manage costs is PCB + components.
ostripper: I'd be remiss if I didn't say "thanks" for designing the HB! But I can't see where you got $100 for the amp. I costed the BOM at $80/channel, not including the PCB.
JMF: I would love to start with a chipamp and see how it goes, but as I said I can't afford to build it and then discover I need more power.
Cheers~
Hi,
That is the sort of statement that indicates you really
don't know what is going on matching speakers to
amplifiers. What are your speakers ? What is the
excursion limited power handling at low frequencies ?
Not that you can change much about how much power
a speaker can take, the issue is, is lower power OK.
rgds, sreten.
It sounds like you're buying you parts from the wrong place. Ostripper's estimate is pretty good.
As far as saving money goes, Rod Eliot it in Australia. If you buy boards from him and he ships from there, the shipping cost will be much higher than a USPS priority box from Houston TX (diyaudio store).
Cost of parts. I don't know why honey badger uses all those exotic probably fake on Ebay transistors. I see the diyaudio store is not selling the kit with parts this week, just the bareboard. I would use MPS8099 at $.08 for all the little npns, and MPS56 at $.11 for the little pnp. If you can't find those bargains anymore at newark, try 2n5401 and 2n5551 at $.35 ea.
TO126 if any, fairchild bd139/140 are about $.50. MJE15032/33 in TO220 is worth the $4 they cost. but NJW381/302 in TO3p are a bit exotic maybe pricey. Try MJ802/4502 to save a few dollars, from newark which won't be counterfeit.
Look with the Ic minimum Vceo minimum tool at newark to see what is on sale that day in TO3p/TO247. Might be fairchild fjl4215/4315, or Sankyo 2SA1693/2SC4466. Watch out for short lead surface mount parts TO264, you don't want that without a $700 workstation and a $100 microscope for surface mount.
Silver mica caps, I've been substituting CPO ceramics for those without a lot of obvious oscillations. I don't know why the passion for silver-mica caps.
I'm scratch building a 5 transistor driver 2 output transistor circuit to fit in my chassis, use 80 v no center tap transformer, and putting out 1 W average and 200 w rare peaks on 55 db classical music. I'm going into the second year fiddling with it after one big failure (pwgtang), and wish I could buy some US made boards to replace my originals that are peeling lands and don't sound very good cold anyway. Honey Badger is attractively worked out and supported, but won't fit in the hole or use the power supply I own. I don't need 3 output pairs anyway for 101 db@1w1m. If you are not playing strumma strumma singer songwriters with a dynamic range of 10 db, you need more power than a chip amp can put out. My classical LP's go 55 db dynamic range sometimes, and 70 db for superior CD's. Just including apiano in the mix, acoustic and not electric, runs the dynamic range up to 20 or 30 db bacause of the ping at the start of the note. If your music is all one sound level and you listen soft, JM Fahley advice about IC amps at 60 W is appropriate.
However if your amp goes into clipping, the square top waveforms tend to melt woofer coilss if you do it a lot. Most band people know too much amp power is better for speakers, than too little. Watch the excursion of the woofers when you start out a honeybadger or 300w/ch amp, if they approach 1" you may need to limit the volume. If not, not.
Cost of parts. I don't know why honey badger uses all those exotic probably fake on Ebay transistors. I see the diyaudio store is not selling the kit with parts this week, just the bareboard. I would use MPS8099 at $.08 for all the little npns, and MPS56 at $.11 for the little pnp. If you can't find those bargains anymore at newark, try 2n5401 and 2n5551 at $.35 ea.
TO126 if any, fairchild bd139/140 are about $.50. MJE15032/33 in TO220 is worth the $4 they cost. but NJW381/302 in TO3p are a bit exotic maybe pricey. Try MJ802/4502 to save a few dollars, from newark which won't be counterfeit.
Look with the Ic minimum Vceo minimum tool at newark to see what is on sale that day in TO3p/TO247. Might be fairchild fjl4215/4315, or Sankyo 2SA1693/2SC4466. Watch out for short lead surface mount parts TO264, you don't want that without a $700 workstation and a $100 microscope for surface mount.
Silver mica caps, I've been substituting CPO ceramics for those without a lot of obvious oscillations. I don't know why the passion for silver-mica caps.
I'm scratch building a 5 transistor driver 2 output transistor circuit to fit in my chassis, use 80 v no center tap transformer, and putting out 1 W average and 200 w rare peaks on 55 db classical music. I'm going into the second year fiddling with it after one big failure (pwgtang), and wish I could buy some US made boards to replace my originals that are peeling lands and don't sound very good cold anyway. Honey Badger is attractively worked out and supported, but won't fit in the hole or use the power supply I own. I don't need 3 output pairs anyway for 101 db@1w1m. If you are not playing strumma strumma singer songwriters with a dynamic range of 10 db, you need more power than a chip amp can put out. My classical LP's go 55 db dynamic range sometimes, and 70 db for superior CD's. Just including apiano in the mix, acoustic and not electric, runs the dynamic range up to 20 or 30 db bacause of the ping at the start of the note. If your music is all one sound level and you listen soft, JM Fahley advice about IC amps at 60 W is appropriate.
However if your amp goes into clipping, the square top waveforms tend to melt woofer coilss if you do it a lot. Most band people know too much amp power is better for speakers, than too little. Watch the excursion of the woofers when you start out a honeybadger or 300w/ch amp, if they approach 1" you may need to limit the volume. If not, not.
With all due respect, I know well the difference between sensitivity and power handling. The speaker (which I'm currently building) is Roman Bednarek's JDB3, and I based what I said off of the following from his website: "You can definitely feel the bass from the RS180 and they can handle power levels beyond my threshold in my medium sized listening room in most cases. They do eventually reach a point where the sound starts to "compress" and the midrange gets harsh but I would guess that the output is over 100 dB by that point."
Of course, 60W can almost get those speakers above 100 dB output. But I wonder if frequently pushing a chipamp to its upper limit isn't asking for trouble. Hence the initial question: to chipamp or not. It looks like I've got 1 vote for more power, and 1-1/2 votes for chipamp.
Pray tell where I can get all those components for $100! I used the BOM from the Excel worksheet, looked up every PN in Digikey, and it came out to $80/ch (plus $39+SH for the PCB). I didn't bother double-checking with Mouser or anyone else, because at that point it seemed out of reach. I've never seen a kit available on the DIY store, just the PCB.
Also, it's worth pointing out that Rod charges a flat $12 for shipping to the US, which isn't much more than most domestic vendors.
Lastly, could I be so bold as to re-ask these questions re: bridge mode: Can I just use one of these to transform the SE signal to a balanced one? Do I then connect the source ground to the ground input of both amps? And what do I do with the ground output, since the binding posts are now connected to each amp's output? Does this change how or whether one connects to a speaker protection unit? And how does one calculate the wattage of a bridge amp — is it just double the output for 4Ω load (since mine are 8Ω)?
Of course, 60W can almost get those speakers above 100 dB output. But I wonder if frequently pushing a chipamp to its upper limit isn't asking for trouble. Hence the initial question: to chipamp or not. It looks like I've got 1 vote for more power, and 1-1/2 votes for chipamp.
Pray tell where I can get all those components for $100! I used the BOM from the Excel worksheet, looked up every PN in Digikey, and it came out to $80/ch (plus $39+SH for the PCB). I didn't bother double-checking with Mouser or anyone else, because at that point it seemed out of reach. I've never seen a kit available on the DIY store, just the PCB.
Also, it's worth pointing out that Rod charges a flat $12 for shipping to the US, which isn't much more than most domestic vendors.
Lastly, could I be so bold as to re-ask these questions re: bridge mode: Can I just use one of these to transform the SE signal to a balanced one? Do I then connect the source ground to the ground input of both amps? And what do I do with the ground output, since the binding posts are now connected to each amp's output? Does this change how or whether one connects to a speaker protection unit? And how does one calculate the wattage of a bridge amp — is it just double the output for 4Ω load (since mine are 8Ω)?
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I make my own PCBs, nothing can beat this
Instead of building DIY (chip)amp, it might be more economical to buy one instead?
I'm sure you can get decent 'refurbished' discrete 5.1 receiver on Ebay for under $200
with free shipping. No DIY amp will beat this..
Hi illinimdg,
I'll start by telling you that I've been in service for over 35 years professionally. All my experience shows me that a bridged configuration isn't healthy for most chip amps, or even stereo amplifiers commercially available to the home user. I don't know exactly why, but the sound quality isn't as good in bridged mode either. Of course, having your real damping factor (as opposed to what they tell you in the specs portion for bought equipment says) is almost halved by bridging your amplifiers.
I would highly recommend using a stereo amplifier capable of the full power you have decided upon. Given that the average to peak power in music is often in the 15 to 20 X range, be realistic about how much power you think you need.
The Honey Badger looks like a really nice amplifier. One you'll own for decades. I'm actually thinking of building one in the long term. Right now I have another one of ostripper's designs that I'm really looking forward to completing. He is a very good designer.
As for speaker relays, so they can give trouble. Replace them when needed. I've seen plenty of amplifiers that come in for a relay around the 20 year mark. That's a broad range of experience. You can make them last simply by turning the volume down when you turn them on or off. A delayed mute on the input signal would achieve the same thing.
So, a "kit" of some description would give you the greatest performance, the best experience building even if you do have trouble, and the greatest amount of pride in the finished product. Going with one of ostripper's designs is going to be about as certain to give you a great sounding, long lasting amplifier as any. I think your wife might loosen the purse strings once she has had a listen to your amplifier build.
I've built a few Symasym amplifiers too. They all sounded great, but at 50 watts the ones I built aren't powerful enough for what you want. They each sound great, a Honey Badger is better, so I can't really recommend one of those. I guess a good preamplifier will come after this?
Build your amplifier once, enjoy it for a lifetime.
-Chris
I'll start by telling you that I've been in service for over 35 years professionally. All my experience shows me that a bridged configuration isn't healthy for most chip amps, or even stereo amplifiers commercially available to the home user. I don't know exactly why, but the sound quality isn't as good in bridged mode either. Of course, having your real damping factor (as opposed to what they tell you in the specs portion for bought equipment says) is almost halved by bridging your amplifiers.
I would highly recommend using a stereo amplifier capable of the full power you have decided upon. Given that the average to peak power in music is often in the 15 to 20 X range, be realistic about how much power you think you need.
The Honey Badger looks like a really nice amplifier. One you'll own for decades. I'm actually thinking of building one in the long term. Right now I have another one of ostripper's designs that I'm really looking forward to completing. He is a very good designer.
As for speaker relays, so they can give trouble. Replace them when needed. I've seen plenty of amplifiers that come in for a relay around the 20 year mark. That's a broad range of experience. You can make them last simply by turning the volume down when you turn them on or off. A delayed mute on the input signal would achieve the same thing.
So, a "kit" of some description would give you the greatest performance, the best experience building even if you do have trouble, and the greatest amount of pride in the finished product. Going with one of ostripper's designs is going to be about as certain to give you a great sounding, long lasting amplifier as any. I think your wife might loosen the purse strings once she has had a listen to your amplifier build.
I've built a few Symasym amplifiers too. They all sounded great, but at 50 watts the ones I built aren't powerful enough for what you want. They each sound great, a Honey Badger is better, so I can't really recommend one of those. I guess a good preamplifier will come after this?
Build your amplifier once, enjoy it for a lifetime.
-Chris
The amp I know is rated for bridging, the PV-1.3k, the output transistor pairs are sort of matched at the factory for Vbeon. Then the output transistors are separated from each other by 0.5 ohm emitter resistors to force current sharing. Then the driver stages of each channel are defined gain determined by the feedback resistors, so they should be putting out the same driver current. The grounds of the two sides are tied together. The speaker terminal hots of the two sides are tied together bridged. It is not a wheatstone bridge, and both channels of the amp are in phase when bridged. The input is forced by a switch to be the same for both channels when bridged.
So if I were bridging 2 lm3886 for example, I'd use .5 ohm or 1 ohm resistors at the outputs to force current sharing. I don't know if this has been done before. Doing this puts you on perfboard with bare wires, which in my experience is a solder problem. Or you lay out something in a simulator and get boards made custom, way beyond my puny computer op systems capability. (Lubuntu 12) Edit see anatech's experience why nobody does this - I'm certainly not going to.
In my 1w average 200 w peak amp, instead of using 2 MJ15015 output transistors (pushpull pair) and an Apex AX6 driver board, I have thought of using a LM3886 IC driver pushing a stack of 330 ohm resistors + rail to ground, separated by a double diode or a Vbe multiplier transistor. Follow this by the pushpull MJ15015s, for current amplification only. One base to the top of the double diode, the other base to the bottom. That should get you plenty of current for musical peaks. the lm3886 itself is current limited to about 7.5 A. A MJ15015 can do 20 for a millisecond, a MJ802/4502 can do more I suspect. Of course this puts one on perf board as the driver board, since noone I know of has done this before. One cool thing about this experiment, you can use a speaker protection capacitor without voltage reversal, if you put the lm3886 in single supply mode and don't connect the center tap. So no speaker protection relay is required.
Digikey semis should be competitive but all three mouser newark digikey I think are high on big block heat sinks and class AB amp transformers. See vendors above post 2 for low buck solutions, at the cost of 2 more freight charges. Of course a blown 300w-500 w used PA amp solves the heat sink, enclosure, transformer, rectifier/capacitor board and machining problems all at once. There was a PV500 here last month, $100, allegedly working. Used recievers are too feeble in output transistor pairs, IMHO.
So if I were bridging 2 lm3886 for example, I'd use .5 ohm or 1 ohm resistors at the outputs to force current sharing. I don't know if this has been done before. Doing this puts you on perfboard with bare wires, which in my experience is a solder problem. Or you lay out something in a simulator and get boards made custom, way beyond my puny computer op systems capability. (Lubuntu 12) Edit see anatech's experience why nobody does this - I'm certainly not going to.
In my 1w average 200 w peak amp, instead of using 2 MJ15015 output transistors (pushpull pair) and an Apex AX6 driver board, I have thought of using a LM3886 IC driver pushing a stack of 330 ohm resistors + rail to ground, separated by a double diode or a Vbe multiplier transistor. Follow this by the pushpull MJ15015s, for current amplification only. One base to the top of the double diode, the other base to the bottom. That should get you plenty of current for musical peaks. the lm3886 itself is current limited to about 7.5 A. A MJ15015 can do 20 for a millisecond, a MJ802/4502 can do more I suspect. Of course this puts one on perf board as the driver board, since noone I know of has done this before. One cool thing about this experiment, you can use a speaker protection capacitor without voltage reversal, if you put the lm3886 in single supply mode and don't connect the center tap. So no speaker protection relay is required.
Digikey semis should be competitive but all three mouser newark digikey I think are high on big block heat sinks and class AB amp transformers. See vendors above post 2 for low buck solutions, at the cost of 2 more freight charges. Of course a blown 300w-500 w used PA amp solves the heat sink, enclosure, transformer, rectifier/capacitor board and machining problems all at once. There was a PV500 here last month, $100, allegedly working. Used recievers are too feeble in output transistor pairs, IMHO.
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VHex+
Hi illinimdg,
If I may recommend, VHex - a very simple high-quality power amp, built and tested by a number of members here:
VHex amplifier
Parts are very inexpensive, HexFETs are cheap and rugged.
Here is a single-layer PCB layout, designed by member abetir - you can etch it yourself:
PCB layout docs for etching
Here it is - etched, built and tested by Terry:
Terry's build
You can also buy professionally manufactured PCBs for VHex+ (more powerful 2-output-pairs version of the amp) at $26.90 for a pair - see attached, that's what they look like.
In any case, overall cost is rather low, as well as simplicity, preserving very high performance at the same time.
Cheers,
Valery
Hi illinimdg,
If I may recommend, VHex - a very simple high-quality power amp, built and tested by a number of members here:
VHex amplifier
Parts are very inexpensive, HexFETs are cheap and rugged.
Here is a single-layer PCB layout, designed by member abetir - you can etch it yourself:
PCB layout docs for etching
Here it is - etched, built and tested by Terry:
Terry's build
You can also buy professionally manufactured PCBs for VHex+ (more powerful 2-output-pairs version of the amp) at $26.90 for a pair - see attached, that's what they look like.
In any case, overall cost is rather low, as well as simplicity, preserving very high performance at the same time.
Cheers,
Valery
Attachments
If you're interested in this design, I can put together a "kit" with all required parts.
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Vhex amp is a single pair output device kit. If you listen very softly that would probably be fine. I like peaks occasionally.
Pansonaudio.com is selling a LM49810 IC kit but he has limited his to 50W. TI says the IC will drive 300 W. Compact Series
$48/channel w/o heatsinks +~$30 freight.
I suspect Panson's tiny heat sink is the big limiter. He has probably also limited the power rails to < the 100 v TI allows. If you put the output devices off the board on a huge 6x8 heatsink I bet you could get more like the 300 w TI allows. He does have 2 pairs of output devices.
You can't buy just the LM49810 IC, I got the last of the digikey stock after TI discontinued it. You can buy 600 of them, but in onesies panson is the source.
Pansonaudio.com is selling a LM49810 IC kit but he has limited his to 50W. TI says the IC will drive 300 W. Compact Series
$48/channel w/o heatsinks +~$30 freight.
I suspect Panson's tiny heat sink is the big limiter. He has probably also limited the power rails to < the 100 v TI allows. If you put the output devices off the board on a huge 6x8 heatsink I bet you could get more like the 300 w TI allows. He does have 2 pairs of output devices.
You can't buy just the LM49810 IC, I got the last of the digikey stock after TI discontinued it. You can buy 600 of them, but in onesies panson is the source.
My VHex amp is a dual output pair version putting out around 100WRMS @ 8 ohms. I've been running it fairly hard for the past week. It sounds nice!
PS. Those are my amps in Vzaichenko's picture.
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