Your in the USA. Mother mouser has MODERN njw0281/0302's for under $2/25 , ($2.31 apiece) why would you bother with ancient history ? 4pair-250w = a $16-$18 Op stage @ 250Vce - 30mhz Ft.
OS
If were to build another amp today I would certainly use a more modern type.
I just feel that the old work horse deserves much more credit than it has been givin in some cases.
The other thing is I still have a few amps that use them and have rarley failed and only when driven very hard for a long time have they failed.
Jameco still carry's them for $.79 each per 10 and this would get both of my amps up running without breaking the bank.
And Radio shack still carry's them for around $2 so when I just need 4 or 5 of them it won't cost me $12 for tax and shipping on top of the total cost.
And most if not all of the parts for a simple amp as such can still be found there for the newbie to cut their teeth an such a project as I did some 35 years ago.
Thats all. jer
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Thanks Gerald. Sometimes people loose site that electronics isn't all about purchasing the biggest and best stuff. Some people want to see how much they can build out of stuff they have lieing around that fits in there budget. Really nice projects you invest time and money into. Others just do what they do.
Yep I agree!
Ever since I was a young budding guitarist playing rock and roll I have been on the prowl to be able to build the biggest baddest amp that I can with the least amount of money to be spent and still have good quality.
And when I first started out collecting schematics and found out what parts were involved, I found it was redicualess for the prices that they charged for some of the peices of equipment that I sought after.
I still think that way today although it has gotten much better in this day and age.
Many don't realize or never experienced how hard it was to find and what it cost back then to find an amp of 150 watts or more of decent quality without getting a lifetime loan from the man.
So this is why I have great respect for some of the older circuits and alot them have stood the test of time and still meet or exceed todays standards in many ways with the exception of the sub .001% THD stuff that is just now starting to come out into the main stream.
Besides who can actualy here the diffrence anyhow, Besides afford it?
Just look at the specs of some of the stuff that is being pushed on the public now.
Hardely any of it meets my requirement of less than .1% to .05% THD at 100 watts as a minimum.
jer
Ever since I was a young budding guitarist playing rock and roll I have been on the prowl to be able to build the biggest baddest amp that I can with the least amount of money to be spent and still have good quality.
And when I first started out collecting schematics and found out what parts were involved, I found it was redicualess for the prices that they charged for some of the peices of equipment that I sought after.
I still think that way today although it has gotten much better in this day and age.
Many don't realize or never experienced how hard it was to find and what it cost back then to find an amp of 150 watts or more of decent quality without getting a lifetime loan from the man.
So this is why I have great respect for some of the older circuits and alot them have stood the test of time and still meet or exceed todays standards in many ways with the exception of the sub .001% THD stuff that is just now starting to come out into the main stream.
Besides who can actualy here the diffrence anyhow, Besides afford it?
Just look at the specs of some of the stuff that is being pushed on the public now.
Hardely any of it meets my requirement of less than .1% to .05% THD at 100 watts as a minimum.
jer
If I may chip in ...
There is too much of an obsession with THD - if you look at the "older" transistor designs from the 60's/70's, ther ewas a lot of effort of control IMD. I see NO ONE here speccing IMD at all, just bandying around stoopid figures of 0.001% THD (!)!.
And, yes, there are much newer and better devices available, but just see if you can get then 5-10 years later to "fix" your beloved high-falutin design.
I side with using the commonly available transistors such as the 2n3055/MJ2955, BD139/BD140, MJE340/MJE350, MPSA42/MPSA92, 2n5401, etc. - you get the picture.
And since I repair guitar and PA equipment, there is nothing like the older gear than is 'primitive', but can run all day and all night, as opposed to your new Class-whatever, that craps out in the middle of your gig, and rests comfortable in intensive care awaiting unobtanium parts (cf. Gallien-Kruger).
There is too much of an obsession with THD - if you look at the "older" transistor designs from the 60's/70's, ther ewas a lot of effort of control IMD. I see NO ONE here speccing IMD at all, just bandying around stoopid figures of 0.001% THD (!)!.
And, yes, there are much newer and better devices available, but just see if you can get then 5-10 years later to "fix" your beloved high-falutin design.
I side with using the commonly available transistors such as the 2n3055/MJ2955, BD139/BD140, MJE340/MJE350, MPSA42/MPSA92, 2n5401, etc. - you get the picture.
And since I repair guitar and PA equipment, there is nothing like the older gear than is 'primitive', but can run all day and all night, as opposed to your new Class-whatever, that craps out in the middle of your gig, and rests comfortable in intensive care awaiting unobtanium parts (cf. Gallien-Kruger
).I thought i wasn't the only one who thought the way i did some good comments boolaboo. I really believe the same also. I have spent a lot of my time looking for schematics on amps that are basically cheap reliable old beasts that basically chug along and don't cause one to much pain in complexity and my pocket. I think anyone thats in the band scene understands that fully.
I have an old Maplin catalogue from the late 70's which I think has this design in.
I'll see if I can find it and scan it for you.
about
2N3055 Power Transistor, 2N3055 Datasheet PDF, Circuit Schematic, Pinouts
(2N3055 Power Transistor Technical Specifications)
I read:
With changes to the technology, the original process became uneconomical and a similar device, now using the name 2N3055 transistor, was supplied using epitaxial base technology. The maximum voltage and current ratings of this device are the same as the original, but the power handling (safe operating area) is limited at high voltage to a lower current than the original. However, the cut-off frequency is higher, so allowing the newer type of 2N3055 transistor to be more efficient in switching power supplies. Also the higher frequency response improves the performance when used in audio amplifiers. Some suppliers offer a high safe-operating-area version of the 2N3055 power transistor using the "H" suffix.
It is therefore to be considered in any case the year of manufacture to which it is.
Who can tell me an URL with a genuine RCA datasheet?
have a look also there:
http://www.diyaudio.com/forums/soli...-models-quasi-complementary-power-output.html
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Thank you. I was curious to see if anyone knew that the original 2N3055 is actually no longer made and has been out of production for a long time.
The part number is still used because so many folks used and continue to use this for their designs. A problem occurs in replacing older 2N3055s with modern ones. The gain bandwidth is so much higher that the replacement may oscillate.
One popular method was to take any power transistor production that did not meet the intended specifications and label it as a 2N3055 because the data sheet specifications were so poor.
So it is possible to find devices labelled 2N3055 that have much higher voltage, gain and bandwidth.
The original question was would the schematic work for a 200 watt amplifier. Even with better output transistors the answer is not really. The output current should be capable of 20+ amps to drive a 4 ohm rated loudspeaker at what could be it's minimum impedance! The current gain at high current can drop to 5! So that would require a driver current of 4+ amps (at least 2 if you are an optimist.) So that would require the driver stage to dissipate 210 watts! Of course in this design the pre-driver current is .05 amps so even with an optimistic high gain output of 100 ( 5 x 20) you would have Five peak amps out.
So the design shown is around a 50 watt design (into 4 ohms) absolute maximum!
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This really isnt true. I had a 2 pair 2n3055/mj2955 225WRMS amplifer that really was very loud. I used it for a disco for years and had very good service out of it.
Yes, thank you.
Please send not as PM but to my e-mail address:
kirschner-hifi@tiefbasswiedergabe.de
The design shown at the start of the thread is what was discussed. It certainly is possible to build a bigger amplifier what is shown is not.
Is English your second language?
The design shown at the start of the thread is what was discussed. It certainly is possible to build a bigger amplifier what is shown is not.
Is English your second language?
You said it would only produce 50 watts.
If two pairs prodiuces 225WRMS then 1 piar will produce 112.5watts.
My point still stands, your statement was not true.
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