My classmates and I al had to pick a project to build and depending on what it is and if it works and if it's hard to make we get grades that are essential for me to complete my last year.
I didn't have an idea what to build so i went to talk with my dad.
It didn't take him long to tell me what he wanted:
transistor amplifier 4x80W rms, in and out for tape, in for Cd, SCART in for TV, pre-amp for mic and pickup. Goodman speakers or Cerwen vega. when I heard him busy my head kindoff exploded 'cause I don't yet have the knowledge of audio like he made me believe he has. what i get from it know is that he wants 4 speakers, each speaker has a 80Wrms amp, per 2 80W amps there is a normal amp, there al in signals come toghether and the out's of the 2 pre-amps to. the big problem is finding schematics like the one's i need and the need to know if the schematics are good.
so if someone has a schematic for a +/-80Wrms amplifier, a power supply to go whit that and pre-amps for mic and pick up it would be a great help
also site's with more info on the subject that you think that would realy help me out then please post them.
thanks
I didn't have an idea what to build so i went to talk with my dad.
It didn't take him long to tell me what he wanted:
transistor amplifier 4x80W rms, in and out for tape, in for Cd, SCART in for TV, pre-amp for mic and pickup. Goodman speakers or Cerwen vega. when I heard him busy my head kindoff exploded 'cause I don't yet have the knowledge of audio like he made me believe he has. what i get from it know is that he wants 4 speakers, each speaker has a 80Wrms amp, per 2 80W amps there is a normal amp, there al in signals come toghether and the out's of the 2 pre-amps to. the big problem is finding schematics like the one's i need and the need to know if the schematics are good.
so if someone has a schematic for a +/-80Wrms amplifier, a power supply to go whit that and pre-amps for mic and pick up it would be a great help
also site's with more info on the subject that you think that would realy help me out then please post them.
thanks
hello belg,
no offense intended, i just want to save you some frustration.
there is no way you can make this work... mic preamps and phono preamps are hard to build because they amplify tiny signal levels, they are very sensitive to hum and noise pickup. this stuff is a bit hard to get right.
All the signal switching you listed can be worked out...
making a four channel power amplifier is a big enough school project!
look at Rod Elliot's site for some schematics. he also sells boards.
what about
http://sound.westhost.com/project03.htm
for an easy poweramp.
there is very little chance of success without considerable experience for the project you outlined. And a non-working project will probably not net you good grades, eh? So may i propose a four-channel poweramp for now and a matching preamp (ideally kit based) for later?
regards
k
no offense intended, i just want to save you some frustration.
there is no way you can make this work... mic preamps and phono preamps are hard to build because they amplify tiny signal levels, they are very sensitive to hum and noise pickup. this stuff is a bit hard to get right.
All the signal switching you listed can be worked out...
making a four channel power amplifier is a big enough school project!
look at Rod Elliot's site for some schematics. he also sells boards.
what about
http://sound.westhost.com/project03.htm
for an easy poweramp.
there is very little chance of success without considerable experience for the project you outlined. And a non-working project will probably not net you good grades, eh? So may i propose a four-channel poweramp for now and a matching preamp (ideally kit based) for later?
regards
k
okay, so making my own pre-amp is out
that's not to big of a problem 'cause that was just an option. We won't be using a mic or pickup anyway. I just wanted to make a full system.
My knowledge about electronics is enough to build something with just the schematic, I've got the possibility to use ultiMate programs to draw te PCB and also to make PCB's is not a problem.
Another problem is that the sustem really has to be good, my father is really a music fanatic and first he wanted amps like MBLE made them altough they're broke for over 20 years but now philips sells those amps, he wanted goodman or cerwen vega speakers so i'm looking for a verry good amp.
What I saw on that site would be nice but I'm not shure if it is what i'm looking for. If you know more examples of good amps with 100Wrms or something like it that would also be great
thanks keyne
that's not to big of a problem 'cause that was just an option. We won't be using a mic or pickup anyway. I just wanted to make a full system.
My knowledge about electronics is enough to build something with just the schematic, I've got the possibility to use ultiMate programs to draw te PCB and also to make PCB's is not a problem.
Another problem is that the sustem really has to be good, my father is really a music fanatic and first he wanted amps like MBLE made them altough they're broke for over 20 years but now philips sells those amps, he wanted goodman or cerwen vega speakers so i'm looking for a verry good amp.
What I saw on that site would be nice but I'm not shure if it is what i'm looking for. If you know more examples of good amps with 100Wrms or something like it that would also be great
thanks keyne
'cause i'm still under moderation i'll reply here and paste this post i'm my post above and delete this one, srry for this
I was checking out the site that keyne gave me and browsed the other projects and i found this project: http://sound.westhost.com/project3a.htm
I found it more interesting 'cause the overall quallity would be better and the output is more like i wanted it.
What do you think?
I was checking out the site that keyne gave me and browsed the other projects and i found this project: http://sound.westhost.com/project3a.htm
I found it more interesting 'cause the overall quallity would be better and the output is more like i wanted it.
What do you think?
ok here I am again, i alsow saw that posts are unediteble, ok so I learn something new
i've found some stuff that was reallyyy interesting to me
i'll be making this amp:
http://sound.westhost.com/project3a.htm
so I order 2 PCB's and use it with 4ohm and tadaa 100Wrms
as pre amp i'll be making this one:
http://sound.westhost.com/project97.htm
it has the desired controlls and also I can order the PCB
schematics on that page where also verry helpfull and they made me understand the whole idea of it
as phonoamp i'll be making this
http://sound.westhost.com/project06.htm
again I order the PCB and my work is complete
with this my father wanted to use goodman or cerwen vega speakers, i'll wee what's availeble today
the stuff i just typed, does it look okey to you guys, I don't know yet what works good togheter and what won't
is someone willing to check it out for me?
thx guys
i've found some stuff that was reallyyy interesting to me
i'll be making this amp:
http://sound.westhost.com/project3a.htm
so I order 2 PCB's and use it with 4ohm and tadaa 100Wrms
as pre amp i'll be making this one:
http://sound.westhost.com/project97.htm
it has the desired controlls and also I can order the PCB
schematics on that page where also verry helpfull and they made me understand the whole idea of it
as phonoamp i'll be making this
http://sound.westhost.com/project06.htm
again I order the PCB and my work is complete
with this my father wanted to use goodman or cerwen vega speakers, i'll wee what's availeble today
the stuff i just typed, does it look okey to you guys, I don't know yet what works good togheter and what won't
is someone willing to check it out for me?
thx guys
belg,
the ESP projects with their associated PCBs look to be the right thing for the project. This is not tweaky high-end stuff, but this also means you have a very good chance of making things work with his PCBs.
It would be an advantage if you had an oscilloscope and a signal generator so you can verify performance of the finished product.
build it carefully and slowly, and modular! check all pieces before you connect them together.
Goodmans is out of business i think. Cerwin Vega (spelling!) is here: http://www.cerwinvega.com/ . I don't think these speakers are my cup of tea so i will refrain from commenting further on this matter.
Regards and Good Luck with your project!
k
the ESP projects with their associated PCBs look to be the right thing for the project. This is not tweaky high-end stuff, but this also means you have a very good chance of making things work with his PCBs.
It would be an advantage if you had an oscilloscope and a signal generator so you can verify performance of the finished product.
build it carefully and slowly, and modular! check all pieces before you connect them together.
Goodmans is out of business i think. Cerwin Vega (spelling!) is here: http://www.cerwinvega.com/ . I don't think these speakers are my cup of tea so i will refrain from commenting further on this matter.
Regards and Good Luck with your project!
k
hey keyne, i have an oscilloscope and low frequency generator that can go up to about 2Mhz, i think there are some more things i have acces to at school, that won't be a problem.
If the teacher accepts and i hope he does 'cause i love this project then i'll start ordering the pcb's and the parts.
The cooling fins, do they have to be outside of the casing or dan it be inside with enough vent holes?
thx for the cerwIn vega
site, i'll be surfing that one for a while to. You also say that cerwin vega isn't your favorite but then what would you recommend, i myself don't have a clue what to use but my father said he wanted these, what are the pro's and contra's?
thx for the help keyne
If the teacher accepts and i hope he does 'cause i love this project then i'll start ordering the pcb's and the parts.
The cooling fins, do they have to be outside of the casing or dan it be inside with enough vent holes?
thx for the cerwIn vega
site, i'll be surfing that one for a while to. You also say that cerwin vega isn't your favorite but then what would you recommend, i myself don't have a clue what to use but my father said he wanted these, what are the pro's and contra's?thx for the help keyne
okey i've switched preamp, i'll be building http://sound.westhost.com/project88.htm with power supply http://sound.westhost.com/project05.htm
the cooling fins should be outside, they CAN be inside (as in all the commercial mid-fi equipment) but you really have to make big vent holes in the top and bottom of the enclosure. Or you need a fan, which obviously is noisy (but you could add temp control for the fan to your project, too...).
I don't buy speakers, so i have no recommendation, sorry! i build my own... all i can say that it doesn't make much sense to select a speaker based on brand name alone, because the range of speakers offered by one company is vast. I guess your father wants a certain sound associated with a CV speaker he already heard and not just the sticker on the box, eh? Maybe he can help you selecting the speaker based on catalogs or the website or - much better - actually listening in a store.
regards
k
I don't buy speakers, so i have no recommendation, sorry! i build my own... all i can say that it doesn't make much sense to select a speaker based on brand name alone, because the range of speakers offered by one company is vast. I guess your father wants a certain sound associated with a CV speaker he already heard and not just the sticker on the box, eh? Maybe he can help you selecting the speaker based on catalogs or the website or - much better - actually listening in a store.
regards
k
well he has always been a fan of audio and listening to music, i think it's like you say, that certain sound one produces i guess.
surely we'll be going to a store to listen and so on butt if someone has a good idea to fit this amp, please tell me.
about that fan, indeed i could try to do that whit a NTC resistor, that might work, butt my dad says that if it's a good amp and there are vent hole's at the back, bottom, side and top (at the end of the casing were the fins will be placed) then the heat won't be that big, but also the supply's will be placed in that same casing so maybe...
i'll try to convince him to putt te fins on the outside or to put a fan with an ntc around it
surely we'll be going to a store to listen and so on butt if someone has a good idea to fit this amp, please tell me.
about that fan, indeed i could try to do that whit a NTC resistor, that might work, butt my dad says that if it's a good amp and there are vent hole's at the back, bottom, side and top (at the end of the casing were the fins will be placed) then the heat won't be that big, but also the supply's will be placed in that same casing so maybe...
i'll try to convince him to putt te fins on the outside or to put a fan with an ntc around it
hellow again
does someone has online companies that can deliver the output transistors that i need for the p3a amp from esp?
i can't find them on farnellindustries and not even on the official site of OnSemi
i'm talking about the MJE15035 and the MJL...
i also sent a mail to farnell to ask them about those transistors and they don't have them.
thx
does someone has online companies that can deliver the output transistors that i need for the p3a amp from esp?
i can't find them on farnellindustries and not even on the official site of OnSemi
i'm talking about the MJE15035 and the MJL...
i also sent a mail to farnell to ask them about those transistors and they don't have them.
thx
Output Transistors
With regards to the new transistors for the P3a try http:\\www.onsemi.com . As a student constructing a genuine project you should have no problem getting samples of the transistors shipped to school for free.
The older ones for the P3a were BD139 & BD140 drivers with your choice of output (Rod used 2SA1302 2SC3281 - now obsolete & even 2955 3055 pairs I believe), but have a look at http://www.anidian.com/audio/construct/p3a_1.shtml for some alternatives
I'm building using the MJ15003/4 pair with MJE340/50 drivers & there are many other combinations that have been used on this amp with great success listed on this site.
My heatsinks will be internal with 2 chanels per 0.6C/W heatsink for a bi-amped setup
Cheers & good luck
Paul
With regards to the new transistors for the P3a try http:\\www.onsemi.com . As a student constructing a genuine project you should have no problem getting samples of the transistors shipped to school for free.
The older ones for the P3a were BD139 & BD140 drivers with your choice of output (Rod used 2SA1302 2SC3281 - now obsolete & even 2955 3055 pairs I believe), but have a look at http://www.anidian.com/audio/construct/p3a_1.shtml for some alternatives
I'm building using the MJ15003/4 pair with MJE340/50 drivers & there are many other combinations that have been used on this amp with great success listed on this site.
My heatsinks will be internal with 2 chanels per 0.6C/W heatsink for a bi-amped setup
Cheers & good luck
Paul
ON devices
For the P3A ROD suggest the MJL4281A (NPN) and MJL4302A (PNP) pair.
They are available as well as the MJL1302A/3281A from
www.onsemi.com
Good Luck
\Jens
For the P3A ROD suggest the MJL4281A (NPN) and MJL4302A (PNP) pair.
They are available as well as the MJL1302A/3281A from
www.onsemi.com
Good Luck
\Jens
Well I made a four channel power amp that fits inside a 300*about 480* 75mm amp (w*l*h). This was using G Randy Slones amp design in his high power audio construction manual of design 11.4 "a low distortion amp" or summit like that.
I had to trim off a little bit of the boards and do like two point to point wires to fir them inside the case, heatsinks make the sides of the case and anodised silver alu the top and bottom with mahogany front and a ply back. I had to trim as I didnt check the size I just assumed that 300 (12" for you yankes) length would fit two in. Anyway these amps sound superb much better then a commercial amp costing £700.
I built these as a first power amp project (had done low level things and loudspeakers before tho) and had no difficulties in doing everything myself, from etching the PCB to making the case (but I had build speakers to knew my way around all the tools). I built these when I was 17 so it isnt too hard. Ok now for the last bit price.
OK Ill give a sum up of how much you can expect to spend on the power amp alone.
Power supply and boards all complete including connecty thingies for all channels = approx £300. This is sans case as I used a cheap old computer case that I didnt have to pay for as I already had it.
Ok the power supply I used has a 625VA from maplin which cost £40 and Ive got three 6800uf caps per rain for smoothing. This for me is fine under the light loads I stress the amp. If you want to run four of less then four ohm loads at loud levels, I would suggest a larger supply with summore caps.
The better case which is finished appart from some fancy looking LED's that I wanna add to make it better looking, was made from two conrad engineering heatsinks the 30-75 thing I think one per side ie one per two channels. The top and bottom cost £5 ebay A3 sheets and the front and back fom my dad he makes guitars as a hobby so I scavenged of him.
The book can be found in any good library.
Hope thats helpful Matt
I had to trim off a little bit of the boards and do like two point to point wires to fir them inside the case, heatsinks make the sides of the case and anodised silver alu the top and bottom with mahogany front and a ply back. I had to trim as I didnt check the size I just assumed that 300 (12" for you yankes) length would fit two in. Anyway these amps sound superb much better then a commercial amp costing £700.
I built these as a first power amp project (had done low level things and loudspeakers before tho) and had no difficulties in doing everything myself, from etching the PCB to making the case (but I had build speakers to knew my way around all the tools). I built these when I was 17 so it isnt too hard. Ok now for the last bit price.
OK Ill give a sum up of how much you can expect to spend on the power amp alone.
Power supply and boards all complete including connecty thingies for all channels = approx £300. This is sans case as I used a cheap old computer case that I didnt have to pay for as I already had it.
Ok the power supply I used has a 625VA from maplin which cost £40 and Ive got three 6800uf caps per rain for smoothing. This for me is fine under the light loads I stress the amp. If you want to run four of less then four ohm loads at loud levels, I would suggest a larger supply with summore caps.
The better case which is finished appart from some fancy looking LED's that I wanna add to make it better looking, was made from two conrad engineering heatsinks the 30-75 thing I think one per side ie one per two channels. The top and bottom cost £5 ebay A3 sheets and the front and back fom my dad he makes guitars as a hobby so I scavenged of him.
The book can be found in any good library.
Hope thats helpful Matt
Hi Belg,
Keeping the heat sinks inside will certainly limit their cooling efficiency, even with holes in the enclosure.
As nobody plays at peak level (full power) all the time, a lot of companies rate their heat sinks at 1/3 rated output power.
In your case, that would be 4 times 80 W = 320 W.
Total cooling ability should them be no less than approx. 100 W.
For comfortable operation, you will not want to calculate a temperature rise of more than 25 degree above ambient for the sinks. This leaves margin for the thermal resistance of the insulation when mounting the transistors, and the casing-to-die thermal resistance. (from the semi-conductive part of the transistor to its enclosure).
Effectively this gives an overall heat sink specification of 0.25 K/W which will be very difficult to obtain unless you place the heat sinks as the sides of the enclosure. Remember to mount the Vbe stage transistor on the heat sink for thermal compensation, or it'll melt down !
In stead of repeating myself over and over, I suggest you download my booklet from www.sylvest.dyndns.dk:8080 with the user name diyaudio and the password booklet.
As for the Cervin Wega speakers, my personal general oppinion is that they are great for partying, and can stand a lot of power. However, I would look for something like the british B&W speakers for something all-round, as I find them to be more musically and detailled.
As someone said, it depends on personal likings and preferred music taste.
Jennice
Keeping the heat sinks inside will certainly limit their cooling efficiency, even with holes in the enclosure.
As nobody plays at peak level (full power) all the time, a lot of companies rate their heat sinks at 1/3 rated output power.
In your case, that would be 4 times 80 W = 320 W.
Total cooling ability should them be no less than approx. 100 W.
For comfortable operation, you will not want to calculate a temperature rise of more than 25 degree above ambient for the sinks. This leaves margin for the thermal resistance of the insulation when mounting the transistors, and the casing-to-die thermal resistance. (from the semi-conductive part of the transistor to its enclosure).
Effectively this gives an overall heat sink specification of 0.25 K/W which will be very difficult to obtain unless you place the heat sinks as the sides of the enclosure. Remember to mount the Vbe stage transistor on the heat sink for thermal compensation, or it'll melt down !
In stead of repeating myself over and over, I suggest you download my booklet from www.sylvest.dyndns.dk:8080 with the user name diyaudio and the password booklet.
As for the Cervin Wega speakers, my personal general oppinion is that they are great for partying, and can stand a lot of power. However, I would look for something like the british B&W speakers for something all-round, as I find them to be more musically and detailled.
As someone said, it depends on personal likings and preferred music taste.
Jennice
Re: Re: Output Transistors
Tarun
Why don't you just use 2SA1943/2SC5200, the "successors" of these transistors according to their original maker? They have a higher transition frequency. Do they oscillate in the P3A? The Aksa amp's maker has asked his customers to shift to this without any mods to the rest of the circuit, IIRC. If it oscillates, will increasing the value of the compensation cap or putting a gentle passive RC ultrasonic low-pass at the input (maybe 3dB at 60KHz or higher) stop it?millwood said:
Tarun
Im assuming that the heatsink requirements are half if only two of the channels are running. So as you quote 0.25 for the lot 0.5 for half. Finding two 0.5's for the sides of the case if indeed you take that route wont be too hard nor that expensive if you shop around (i got the two conrads for £38) that included shipping from Austrailia, these are 0.37 sinks so thats more then Jennice recommended, I will say that at 0.37 per channel (slone recommends 0.8 per amp) your not going to be in any danger of getting too hot as the thing runs cool even under hard duress. Altho this is active so the amps are not having to work as hard as they would under a full range pair of speakers. Altho the max SPL when using acitve increases so I can play it louder which will mean the amp heats up, but again its not hot just warm.
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