I need help with a woofer/mid amp, Iím giving up on chip amps. - diyAudio
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Old 18th September 2003, 05:20 PM   #1
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Question I need help with a woofer/mid amp, Iím giving up on chip amps.

By the way Iím new to this forum, not really new Iíve been checking it out for a while with great joy. Most of you guys seams to be really smart, Iím not smart just helpless and curious, tell me if itís not OK to ask for help before I actually contributed to the forum?

Well Iíve built some chip amps pretty OK for my pc and party tweeters, but I donít get any solid bottom in my main system with them.

My problems:
*My friend took his woofer amps back.
*The chips amps doesnít do it.
*Budget cuts from my wife.
*To much stuff in my junk boxes that Iím attached to, driving the queen crazy.

What I need:
*An stereo amp that could produce clean, deep, tight fast bas and open, clear mid up to 3kHz.
*That would be able to build with the junk I have or with minimum of new stuff.

What I have:
*Trafo 40.0.40 1000VA that I guess would give me 56V rails.
*Lot of smaller trafos less than 300VA, to cover most needs.
*Several big heat sinks.
*10 big caps 10000uF 63V
*Transistors and Op amps
B700/D736 4pcs of each
B836/D1148 4pcs of each
TIP3055 2pcs
TIP29CFS-ND 1pcs
IRF522 10pcs
IRF9530 10pcs
IRF610ND 8pcs
LM3875TF 4pcs
OPA549T 3pcs
OPA470GP 2pcs
AD797AN 2pcs
*Most passive components and what I donít have I think I could place in my mini budget

Some questions:
*I know this sounds like electronic junkyard wars, I donít have a lot of fancy stuff, but couldnít it be possible to make a decent amp with a decent design anyway?
*Could it be possible to use like LM3875 or other op amps to drive power transistors?
*I have looked at Rod Elliotís subwoofer amp, just because it used the same rails, but I donít have any of those transistors, could it be possible to convert it to the one I have in anyway?
*Are their any really easy power amp schematics that use cheap junk transistors anywhere?

Sorry for all these to you maybe stupid questions, but I try to learn so I will be less helpless in the future!

Thanks!

Magnus

PS: I donít believe in magicís, Iím not a fancy guy so I donít believe in fancy exotic components. (maybe I would if I could afford to try them)
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Old 19th September 2003, 03:15 AM   #2
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Smile amp problem

hi there, have read your post and saw you really have alot of staff to play around with, including the LM3875 which a lot of members here are using as bridge amp or parallel amp or bridge/parallel amp. am even planning to build this B/P amp usingthe AN1192. if you like this thing i can point you in this direction, but i believe u dont want anymore to do with chip amp but rather go for transistor components. i could give you a lot of good design which i have tried. you could use your 3055 but you have to get the complementary pair of this, also the IRF9530, also you get the comp.pair. I presume you still want to use the same transfo. by the way you mentioned Rod Elliots design on subwoofer power amp, are you planning to build a subwof amp or just the power amp?
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Old 19th September 2003, 04:55 AM   #3
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Default Hi thanks

Well I have tried tons of different chip amps in different configurations and the one that had the tightest bas were OPA549 but the mid got dark and disfuse.

I have tried a bridged 3886 and that one sounded really bad, my speaker are kind of difficult and I love to feel the music. I'm biamping and for the top the GC work pretty well even if it is kind of hard compaired to 300B heat. So what I need is kind of super extended subamp that would work okay up to 3kHz.

The pioneer M1 that my friend had here really did it well, but I can't afford to buy thoose in this lifetime.

I would be glad for any suggestions and tip2955 is cheap so I will get some tomorrow. Anything more I should put on my shopping list?

I'm not agaist chip amps at all, just that I haven't found any design that does it for me. Have you seen any hybrid with power mofset to boost the current after a chip amp like lm3875, is it possible? I don't know if it would like my ps though, but I'm open to build several ps if nessesary. Yes I would love to get use of this big trafo and I think 56V rails would give me enough power.

Thanks again.

Magnus
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Old 20th September 2003, 06:29 AM   #4
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Smile tired of using chip amps

base on last post, you said "u luv 2 feel d muzic" the solution for that is a subamp. you want clean mid & high, the solution for that is a well design and made power amp rated at least 120w or if that is not enaf 200w to 250w.
the 2955 & 3055 wont give you what you like, mosfets will do.
by the way if you dont mind my asking, pls. answer my following questions; 1. how familiar r u in making transistor power amps.
2. are u satisfied in just following circuits you would like to try coming from the web?
3. in what power range are you contemplating to build for the power amp and subamp.
4. where do you mostly hear your muzik, inside your home or outside at your garden.
By answering this questions it would give me a better picture of what you really need, then i can direct you to some circuits i have already tried (of course with some modification) and also for the other members who can also advise and direct you.
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Old 20th September 2003, 06:33 AM   #5
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You should go get the 300W sub amp PCBs...then get most of the transistors as samples from On-semiconductor...that way it wun kill u or your wife...since u already have the caps and the trafos...visit the on webby at
www.onsemi.com
free stuff flaoting all over the place...why not get it??
I believe u are just getting a sub amp...for mids I think the lm3886 would do really wel...ever tried bi-amping?? maybe u should do so...
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Old 20th September 2003, 06:34 AM   #6
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Smile tired of using chip amps

base on last post, you said "u luv 2 feel d muzic" the solution for that is a subamp. you want clean mid & high, the solution for that is a well design and made power amp rated at least 120w or if that is not enaf 200w to 250w.
the 2955 & 3055 wont give you what you like, mosfets will do.
by the way if you dont mind my asking, pls. answer my following questions; 1. how familiar r u in making transistor power amps.
2. are u satisfied in just following circuits you would like to try coming from the web?
3. in what power range are you contemplating to build for the power amp and subamp.
4. where do you mostly hear your muzik, inside your home or outside at your garden.
By answering this questions it would give me a better picture of what you really need, then i can direct you to some circuits i have already tried (of course with some modification) and also for the other members who can also advise and direct you.
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Old 20th September 2003, 10:13 PM   #7
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Default Some explanation

Well when I said feeling music I didn't mean it in that way, I don't want it in a rocker kind of way and a subamp is out of the question, kind of hard to tri amp a (2)way system.

Yes what I'm looking for to build is something well design and I like mofsets, how much power would I be able to get from the power supply I've?

Over to your questions.
1. Not much experience at all, just buildt some small test transistor amps, to try to figuring out how it works.
2. I would be okay with just following a schematic, but it would be wonderful if someone would help me to disect it in detail so I could learn something from it, I would like to understand every part and how it works together with the others.
3. I guess i don't need that much power, but I need something is pretty stable on low loads.
4. I listen to the music inside my home but the livingroom is big 800sqf.

Bas/mid driver:
I crossover the speakers at 800, the bas/lower mid is a 15 inch JBL AL1500, sitting in a "P.Buller" decrompression box (works a little like a Terminated line) *smile*

Thanks again

Magnus
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Old 22nd September 2003, 04:44 PM   #8
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li_gangyi Thanks,

Onsemi, were a nice place and really genourus with samples.
I think I will try the 300W sub amp, and he says it works pretty well up to a 1kHz, it doesn't cost anything to try.

Just one problem I can't seam to find MJE15035/MJE15034 anywere, any suggestions for replacments?

Anyone built the sub amp here? Does it sound OK?

mozikluv, do you have any other suggestions?

Magnus
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Old 23rd September 2003, 09:10 AM   #9
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Default sub amp

hi there again, would you believe that i have copied the the circuit of my 12" velodyne sub amp hoping to duplicate the sound quality output. i got the original speaker from a friend whos sub burned. it never did come out the same, not even 75% of the original sound, after that i never tried building another one.

just wait for a day or two, i'll get my transistor substitution book from my friend, he borrowed it but am not sure if there is exactly the same equivalent, it could be a bi9t higher or lower.
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Old 23rd September 2003, 09:31 AM   #10
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You could use some BD139s and BD140s...as far as I noe they arequite safe to use...tried on the P3A with them...not sure about the 300W amp though...and yes...Onsemi rox~!!!
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