| blunt |
Hi all.
I am new to this forum so bare with me. i am kind of a noob when it comes to audio but i have build a class AB amp based on BD 139/140 transistors.
it amplifies arround 60 watt and plays very good. But i talked with my teacher and he said that it could play even better if i had better effects transistors but i dont know how to see if a transistor is better for the purpose(this is problerly still because i am a noob) so i was hoping that someone could reccomend me some. prefereable would be arround 100-150 watt output per channel.
if you need schematics or any other information about the amplifier please say so. I hope this can be a good start for me making alot of DIY audio projects so it would be nice if my first amp would perform good.
BTW i am building a pre-amp for it atm based on the tda2415A if that can help.
Cheers
Anders "blunt" |
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| Johan Potgieter |
Anders,
Quick calculation shows that with BD139/BD140 about 20W output will be maximum within the ratings - not sure where the 60W can come from. Presume we are talking per channel?
In a case of my own 80W amplifier I use the BD139/140 to drive my power transistors (TIP35/36). But over where you are quite a larger variety of transistors would be available than here (South Africa). I was restricted to 42V + 42V supply because of the transistor maximum safe ratings (that is for 8 ohm loudpseaker impedance).
I am sure others will reply here. |
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| Graham Maynard |
Hi Anders,
Can you post up your circuit ?
Cheers ....... Graham. |
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| tomahauk |
bd139/140 are too weak to use them in output stage
in practice they can diffuse something about 5W of power (per one transistor)
as Johan P. said max power of amp with bd139/140 in output stage is 20W
ok, first show scheme of this amp ... |
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| ACD |
Hej Anders :)
Welcome to this forum.
The BD139/140 are good drivers, but poor output devices.
You may want to look at BD911/912 as outpot devices
- easy to get in Denmark and cheap ;) |
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| jacco vermeulen |
| quote: | Originally posted by ACD
The BD139/140 are good drivers, but poor output devices. |
Think again, not if you put 20 of them in parallel.
More amusement : a power amp manufacturer overhere even did it for series production.
(not counting 1 diy twit who got as far as 20 per channel)
And a very cheap output stage up to 75 watt at that, 40 of the good pieces could be as little as $10.
I seem to recollect NP mentioned he thought of going as high as 50 low power devices in parallel. |
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| ACD |
Jacco ;)
In Denmark it would be cheaper to use two pairs of BD911/912 than fourteen pairs of BD139/140...... |
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| jacco vermeulen |
True, but 20 BD139 in parallel gives an output stage with an;
Ft of nearly 200MHz
hFe of 200
30 amps continuous, 40 amps peak.
A total Pd of 320 watts.
Lower Cob than 1 single big Sumo wrestler.
BD911/912 already were major suck in the previous century.
Ft of 3 Mhz, yikes
:clown: |
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| destroyer X |
Maybe this can be a problem too.... in parallel, i think, you will have much bigger capacitance if compared with a single unit
regards,
Carlos |
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| tomahauk |
| quote: | Originally posted by jacco vermeulen
Think again, not if you put 20 of them in parallel.
... |
if amp will be broken, the repairing will be nice adventure ;] |
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| destroyer X |
So, i will be tracking this thread with special interest.
All rigth Jacco...lower capacitance than one single "sumo".....
thanks,
Carlos |
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| tomahauk |
| quote: | Originally posted by jacco vermeulen
True, but 20 BD139 in parallel gives an output stage with an;
Ft of nearly 200MHz
hFe of 200
30 amps continuous, 40 amps peak.
A total Pd of 320 watts.
Lower Cob than 1 single big Sumo wrestler.
BD911/912 already were major suck in the previous century.
Ft of 3 Mhz, yikes
:clown: |
Ft of 200Mhz is very usefull in audio ... ;/
Pd = 320 W, i dont' think so, bd139 have very big thermal resistance junction-case, it's 10*C/W, 20 transistor have 0.5*C/W, with 150W of power the junction will have 100*C temp (in 25*C ambient temp) if you have 0*C/W radiator ... in real world it could diffuse maybe 100W ...
what mean Cob ? |
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| ACD |
| The BD139/140 are good trannies, but please be realistic about their use ;) |
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| Johan Potgieter |
| quote: | Originally posted by jacco vermeulen
Think again, not if you put 20 of them in parallel.
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I thought that was the way non-thinking people used them! :eek:
Poor Anders; with all this he is sure to get his output stage exactly right!
As was requested, can we have a circuit, please? You would by now have learnt that you might be able to only add a more powerful complementary pair. Were you thinking of retaining the same power transformer (it it was overrated)? If so, what are the ratings?
Regards |
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| jacco vermeulen |
| quote: | Originally posted by ACD
The BD139/140 are good trannies, but please be realistic about their use |
You guys are pretty funny.
If you buy big numbers, 20 BD139 or BD140 devices cost less than a Sanken MT200.
An Rcs of 10 C/W divided 20 = 0.50 C/W, please name me a device with a Rcs of 0.50 C/W.
I've got output devices that have an Ft of 80Mhz and higher and built output stages with them, is 80 Mhz no good for audio either ?
Stax didn't seem to think so, and Nelson Pass had no problem using them for my Forté Audio amp.
Name me a professional audio company that still does BD911/BD912 output stages and i'll name you one that does it with TO126 devices. (and it doesn't come cheap)
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| ACD |
Jacco :D
Which pro audio companies uses BD139/140 as output devices now a days :confused: |
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| Bama Slamma |
| BD139/140's work very well as drivers but seem a little underrated as output stage devices. My amp that I built about a month ago uses them as drivers for the 2SC5200/2SA1943 output stage (50 mA bias current). A single pair of 2SC5200/2SA1943 has no problem doing 100w into 8 ohms. Mine get just barely warm playing loud. I had the amp outside playing while I was working in the yard. About six hours of high power playing and the heatsinks were just barely warm to the touch. The transformer was the hottest component of the amp and even it was only warm to the touch (about 110F/40C). Make sure you get them from a reputable dealer. I have heard about some fakes of these transistors. |
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| tomahauk |
jacco v. but you know we got the 2007 year ?
;]
i can buy a 2SC3858 for 3.56 euro
bd139 for 0.17euro, that is 2.6 euro for 20 qty
...
and bd139/140 have only 80V Vce ;/ |
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| blunt |
ok i can see one thing from your responses and i need to do some reading in all this amplifying stuff..
and sorry for the late feedback with schematics. but here it is
you talk alot about driver transistors and output transistors ? i only have the bd139/140...
talked with my teacher and he said that they actually kinda stole it from this site... http://www.sound.westhost.com/project3a |
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| Ryssen |
| quote: | | only have the bd139/140... |
If you use that schema and bd139/140 you wont get 60w.How much you get I dont know,but not 60. |
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| tomahauk |
atlast ;]
first you must higher voltage supply, for 150W@8ohm its about +-55V
second you must replace q7 and q8 for someone stronger , for example 2sc5200 and 2SA1943
...
i will write rest maybe tomorrow |
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| jacco vermeulen |
| quote: | Originally posted by tomahauk
but you know we got the 2007 year ? |
Sure, let's do 2K:
A fellow diyA member is Holger Barske, he tests audio gear for the German Stereo magazine.
He also did an article on an Array power amp, an audio brand from overhere.
The M1 model has an output stage with 64 small smd devices that do an Ft of 120 MHz. |
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| blunt |
sry but 60 watt was what the site said.
tomahawk.. as said i am a newbie sp could you explain what gain there is by replacing the difrent components.?
Cheers
Anders |
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| Johan Potgieter |
Jacco,
Nee, nie bedoel om te spot nie. Dit het maar uitgeglip! :)
Eintlik het jy 'n punt.
Actually Jacco has a point, in that multiple power transistors distributes heat over the heatsink instead of creating a point source. Handy to keep a stabilising transistor from lagging behind in T.
Anders,
That circuit would certainly give up to 80 - 90W. I do not know the 2SC../2SA.. power transistors, but presume they are adequate. The Vce max for the BDs under these conditions is 100V.
There are minor component values here that I wonder about (e.g. the rather high value of C4 and C6; I would rather also phase-correct by having a phase-lead cap over R5) but let us not nit-pick. If you have no way out, 7 - 10 BDs a side should do it, and would also decrease the net value of the temperature compensating resistors. (It would appear that few people realise that these give rise to some high order harmonic distortion.)
Hope you come right - regards. |
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| jacco vermeulen |
Johan,
baie meer mense begryp dat nie. :clown:
I did't mean to say that someone as Blunt should try to do a 60 watt in 8 output stage with BD139/140, i'm just trying to defend the little critters.
Doing a board layout for that many devices in parallel requires a lot of practice and/or start all over again.
If Blunt can not make the distinction between an 8 watt TO-126 and a 200 watt T0-247 he should try something a lot easier first, imo.
My 20 BD139/140 per channel amps are based on the Elektor Class A headphone amp design to drive an AKG K1000, btw. Fully regulated and separate rails for front end and output stage, <1% 1 Ohm metalfilm emitter resistors, BDs mounted without insulators, does 20 watts/8 in Class A.
Not that i still use them, there are much better front end designs nowadays. But they beat Mr Lang's 20 watt/A design by a mile.
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| tomahauk |
| quote: | Originally posted by jacco vermeulen
Sure, let's do 2K:
A fellow diyA member is Holger Barske, he tests audio gear for the German Stereo magazine.
He also did an article on an Array power amp, an audio brand from overhere.
The M1 model has an output stage with 64 small smd devices that do an Ft of 120 MHz. |
i'm not saying 'it won't work', but this solution is 'a little bit crazy', i think better to use 2pair good transistors in output stage than 64, 120Mhz Ft, hmm is that usefull in audio ? and what bandwidth has got that amp ? have you got a link to it ?
| quote: | Originally posted by blunt
sry but 60 watt was what the site said.
tomahawk.. as said i am a newbie sp could you explain what gain there is by replacing the difrent components.?
Cheers
Anders |
the basic solution to make amp give more power is incrase supplying voltage, (what voltage you have?), but if you incrase voltage you must instert transistors that hold a higher voltage and higher current
and you should change a value of some resistors
say what you use transistors as q1, q2, q3, q4, q5, q6, q7, q8 ? |
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| jacco vermeulen |
www.arrayaudio.nl/reviews.html
I built a KSA50 with 12 Sanken devices per channel, two of them dissipate 700 watts.
Some say that is a little bit crazy.
I've got about 1000 output devices with an Ft of 30 to 80 MHz more to play with, not counting mosfets.
Ever constructed an A-75 ? i'll show you a few hundred TO-220 mosfets if you like. |
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| tomahauk |
becouse it is ;]
lets leave that topic ;] i'm borred of it ;]
edit:
you dont say that they used a cascodes that change all, the bandwith must be huge |
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| jacco vermeulen |
| Shame, i posted a list of reviews in 3 different languages. |
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| tomahauk |
| quote: | Originally posted by jacco vermeulen
Shame, i posted a list of reviews in 3 different languages. |
first i try to read Holger Barske review, later i watch other
it's 2:24am go sleep ;] |
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| ilimzn |
| quote: |
Originally posted by blunt
ok i can see one thing from your responses and i need to do some reading in all this amplifying stuff..
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What worries me more is that it seems your teacher should do the same reading too...
Didn't do a very good job of stealing either :)
In a power amplifier, transistors get progressively bigger as you go from the input to the output, as the signal is amplified in stages. In your schematic, the rightmost transistors, top and bottom, are the output transistors, the ones immediately to the left of them are their drivers, and the sole one marked BD140 is the so called voltage amplification stage. Now, to give you an idea how (in)adequate BD139/140 are for the output stage, let's compare transistor sizes: take a BD139 and then multiply it's size about 3 times in each direction - this is how big a MJL type output transistor is - why do you think this is so?
So, I have a question for you - and feel free to ask your teacher the same question: would it be a good idea to fix wheels to a car with screws from a watch, instead of the rather big ones used normally used? |
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| Bonsai |
| Goed om te sien dat 'n paar mense Afrikaans en audio kan praat. |
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| boholm |
@ Blunt:
In your drawing the following transistors are used:
MJE15034, MJE15035, MJL4302 and MJL4281
Can you tell me (us) which transistors are used instead of these, please? |
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| jacco vermeulen |
| quote: | Originally posted by Bonsai
kan praat |
Ek es nog verslaaf aan die Fritz boeke
Anders,
if you want something good between 100 and 150 watts i suggest you build a Leach amp.
You can download everything you need from ACD and Jens, the designer of the Leach boards: HERE
Plenty of people present who can help you while you're building it.
(ek moet praat nie soveel nie :clown: ) |
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| blunt |
ok parts list...
Transistors.
Q1,Q2,Q3,Q9 = NPN BC546
Q5 = NPN BD139
Q4,Q6 = PNP BD140
Q7 = TIP 2955
Q8 = TIP 3055.
thats all the transistors..
32v i think we have from the trafo..
hmm leach amp sound like a good idea.. whats the average cost price and what benefits do it have over the one i allready have built. |
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| richie00boy |
There is nothing wrong with the amp you are trying to build. You just confused people by wrongly saying you had used BD output devices.
The output devices you have chosen are not very good, but they should work. |
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| jacco vermeulen |
| quote: | Originally posted by blunt
what benefits do it have over the one i allready have built. |
It's a complete and matured design, a great many have constructed it.
There's a quadratic rule for amplifiers as well, twice the amp will cost four times as much.
In the 100 to 150 watt range, the Leach amp offers a great deal for the money and time you invest.
Tomahauk is smart, but he is 16 and offering ill advice to upscale Rod's Project 3 oldy to a higher wattage level. Stick to the 60w P3 if you favor economics, otherwise pick a different design.
Less can be more. |
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| jacco vermeulen |
Friday fun:
How does a Polish person say "ï don't know" ?
=> Nie wiem.
How does a Polish person in South Africa say "i don't know" ?
=> Nie wiem Nie. :clown:
(don't shoot me, i've got Polish origin family members) |
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| Bonsai |
| Johan Potgieter needs to answer that one! |
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| jacco vermeulen |
Bonsai,
forgot to mention your Ovation looks impressive, both design and amp itself. |
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| blunt |
hmm so building a new amplifier.. but what about volume control in the leach amp ? will i need my preamp to do that ?
and do you guys know a site where you can buy a box to put it in ? will save me alot of trouble... |
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| AndrewT |
| quote: | Originally posted by tomahauk
atlast ;]first you must higher voltage supply, for 150W@8ohm its about +-55V
second you must replace q7 and q8 for someone stronger , for example 2sc5200 and 2SA1943 |
absolutely wrong.
the 2sa1943/c5200 is only 150W and has a terrible SOAR (1.6A@60Vce) compared to the 230W MJL4281/4302 (3A@60Vce).
The MJL can just about cope (but I don't recommend it) with 150W into 8ohms from +-55Vdc supply rails.
The 2sa1943 has absolutely no hope of being reliable into the same load at that power and voltage.
As for substituting TIPs, well stand back and switch on from a safe distance. |
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| Johan Potgieter |
| quote: | Originally posted by ilimzn
Didn't do a very good job of stealing either :)
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If I were Anders I would start getting confused by now.
Ilimzn,
The diagram given in that particular post (#20), is to me exactly the same as the one in the reference given by "teacher". I did not read that that diagram was using BDs as output transistors - I took it that diagram was the suggestion for the more powerful version.
Blunt,
Perhaps by now academic, but were you originally using BDs also as final transistors (that is, BD139/140 driven by BD139/140), or exactly which circuit was it that you wanted to upgrade. |
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| Johan Potgieter |
Andrew,
I said that I was using TIP35C/36C for output transistors in my about 90W circuit (depending on what the mains decided to be on any particular day ....)
Certainly not for 150W into 8 ohm, but I am really posting this to ask what it is that I am overlooking. Several of these amps have been working for years (it was designed in 1994) - am I in mortal danger of something? (I have earned my pension; I am looking forward to use as much of it as possible.)
Regards |
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| AndrewT |
Hi Johan,
I don't have sufficient data on the TIPs, so cannot comment on 80W into 8ohms. Probably OK on +-42Vdc.
+-55Vdc is a different ball game. |
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| jacco vermeulen |
| quote: | Originally posted by Johan Potgieter
in mortal danger |
Frankly Johan,
i read your bio some time ago, and i'm a weeny bit surprised too.
The era of BD911/912s and any TIP power Tr. ended long before the 1990s for serious audio in my swamp.
Even then, anything more than 75 watts from a single pair of TIP35/36C would have been living on the edge.
All things relative of course.
I've had a 15-watter amp with 4 of the BD139/140 on gentle impedance/phase curve 89dB/W loudspeakers every day for weeks while i was rebuilding the regular power amp.
At serious sound pressure levels even, most of the stuff i enjoy needs a bit of volume.
4 original Philips 8 watt BD139/140, not the higher powered clones, but with bulky heatsinking for such little creatures.
A single pair of TIP35C/36C on >40 Vdc rails would not last long driving a somewhat deceiving loudspeaker, imo.
Example time :
a tulip and cheese audio guy had an output stage with 12 BD911/912 per channel in his 125<->150 watt/8 power amp, untill the mid 80s when he switched to Sanken Sumo sized ones and bumped up the power level to 200W/8.
Ths is how it looks nowadays (with fancy heatsinked Isabellenhütte emitter resistors) => |
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| Johan Potgieter |
:) :) :D :D ;)
Well, then ...... but I did not say the TIPs were the best, if you look up, simply wondering what was wrong!
That amp was designed 13 years ago, choice of components governed by availability (you guys are more fortunate, Jacco), and I still got < 0,01% harmonic distortion, only 2nd and 3rd harmonics (i.e. anything else below threshold of audibility). G.nfb was 29dB. Not boasting, just explaining why I still make them thataway. Venture into better types here (say the mentioned MJLs) and one has to import: either quantity, expensive or both. Safe output (SOAR) is limited to 80W. But I am hunting and hoping.
But thanks for the comment (and interesting discussion in general). |
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| jacco vermeulen |
| quote: | Originally posted by Johan Potgieter
one has to import |
Johan,
i gathered as much +25 years ago from plenty of S-A people i shared time and kak praat with, heard the same from a couple of them on this gathering.
As for electronic parts, it's close to paradise overhere, ek moenie klaag nie.
Without the excess luggage, i'd have preferred living with a view at the Tafelberg long time ago.
(i need the waterfront :clown: )
ps: waar ek geboore is ons praat gelyk Afrikaans.
I've asked myself a couple of times what horrible monster loudspeakers are common in Scotland. |
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