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Old 4th November 2012, 02:53 AM   #11
Pano is offline Pano  United States
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Old 16th June 2013, 01:51 PM   #12
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http://www.circuitstoday.com/wp-cont...er-circuit.png

Any comments on this one?
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Old 17th June 2013, 04:59 PM   #13
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Quote:
Originally Posted by theb0b View Post
Yes, they've drawn the circuit inside out.

Well, simple it most certainly is, and distort it most certainly will. But unfortunately they've not drawn the biggest, heaviest and most expensive part of the circuit; the power supply. Not that that will be sophisticated for an amp like this; a transformer (a bit higher than 30-0-30), a massive bridge rectifier and lots of capacitance at 63 volts. But do you want all this amplification together, or distributed? It might be quite a lot cheaper, and certainly no heavier, to get a single 2000 watt transformer than six (or even three) smaller ones.

You could, either by paralleling up an extra pair of output transistors (and associated emitter resistors) and thus driving a lower impedance, or by bridging up (and thus doubling the available voltage) and doubling the output transistors, get quite a bit more power out of this circuit - depending ultimately on what you can get as a power transformer.

Wanders off grumbling about "pure class B, zero standing current, no RF stabilisation, no Zobel network, crossover distortion…" and fades out into the distance.

Where are you that no-one's trying to dispose of older, heavy amplifiers and replace them with modern ones that may not last quite as long as the older style butgive you a decent risk of getting old without being crippled by the transport? Do they have component s
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Old 17th June 2013, 11:51 PM   #14
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Quote:
Originally Posted by chrispenycate View Post
Yes, they've drawn the circuit inside out.

Well, simple it most certainly is, and distort it most certainly will. But unfortunately they've not drawn the biggest, heaviest and most expensive part of the circuit; the power supply. Not that that will be sophisticated for an amp like this; a transformer (a bit higher than 30-0-30), a massive bridge rectifier and lots of capacitance at 63 volts. But do you want all this amplification together, or distributed? It might be quite a lot cheaper, and certainly no heavier, to get a single 2000 watt transformer than six (or even three) smaller ones.
Multiple amps give me scalability and redundancy. If one section breaks down, a quick reconfigure and I'm back up and running but at reduced power. Where I am there are many electrical rewinding shops. Sourcing transformers isn't my problem.

Quote:
Originally Posted by chrispenycate View Post
You could, either by paralleling up an extra pair of output transistors (and associated emitter resistors) and thus driving a lower impedance, or by bridging up (and thus doubling the available voltage) and doubling the output transistors, get quite a bit more power out of this circuit - depending ultimately on what you can get as a power transformer.

Wanders off grumbling about "pure class B, zero standing current, no RF stabilisation, no Zobel network, crossover distortion…" and fades out into the distance.
It appears that the circuit as posted is thermally very unstable. Pity because it is cheap and powerful. I'm imagining TIP142/147 or TIP2955/3055 as output because they are available everywhere and cheap. Nice simple multiple pair designs with PCB's would be useful.

Would class B MOSFET's be too nasty?

Quote:
Originally Posted by chrispenycate View Post
Where are you that no-one's trying to dispose of older, heavy amplifiers and replace them with modern ones that may not last quite as long as the older style butgive you a decent risk of getting old without being crippled by the transport? Do they have component s
I'm in Cebu, used amps just don't get sold for reasonable prices. There are a few component shops but fakes are rife. Post is not really an option here, many packages go missing.

It's quite frustrating, there are so many excellent threads that head in the right direction, just as a PCB is about to be finalized, somebody comes along and suggests a modification that improves the SQ by 0.01% but adds complexity and exotic components.

On this site the Apex designs look good, I love the Destroyer amps. Quasi, has some great stuff but there aren't any "build" threads that don't spiral off and end up being impossible to follow, the APEX thread for example bounces between many threads, and it is very difficult to understand, even which amps are being referred to. Destroyer and Quasi are similar.

Do I really need to get out the books and reinvent the wheel, just to be able to take part in the conversation?

I'm not technically savvy enough to troubleshoot a new project, and it seems although there is a need for simple cheap designs, they don't seem to be well documented.

I've built some ESP projects, I've etched some of my own boards, I've built Arduino based projects, but DIY audio power amps don't seem to have solid accessible designs.

I'm sure there are many others out there that need a little handholding, to try and enjoy the hobby.

(Sorry, if this seems like a rant, it isn't meant to be one.)
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Old 28th June 2013, 07:29 AM   #15
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Given the files, can you get the pcb made...or make yourself...yes, then

Construct a Leach Superamp. All the necessities are explained on the university site.
Additional benefit - you will have a very good amp.

Gajanan Phadte
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Old 29th June 2013, 03:26 AM   #16
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theb0b - what components are available to you, in the areas of signal transistors (low power, high gain), driver transistors (medium power, medium gain), and output transistors (high power, gain low unless Darlington)?

Are signal / power / Zener diodes easy enough to obtain?

Perhaps with the help of people here, a design could be created or adapted that gets reasonable performance from the components available in your area (I'm in NZ, so am spoiled for choice, but still have plenty of standard old parts in my junk boxes).

I whipped up the CircuitsToday design in LTspice, with appropriate models from OnSemi, and I can concurr with chrispenycate - it's pretty crud. On the other hand, turning it into a usable amplifier would be a good learning experience - a few minor mods improves performance significantly, such as swapping out the bootstrap for a proper current source, and adding in a Vbe multiplier to take it from pure class B to class AB.
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Old 9th July 2013, 10:49 AM   #17
masood is offline masood  India
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Quote:
Originally Posted by gmphadte View Post
Given the files, can you get the pcb made...or make yourself...yes, then

Construct a Leach Superamp. All the necessities are explained on the university site.
Additional benefit - you will have a very good amp.

Gajanan Phadte
dear gajanan phadte,
i also want to make an out door hi fi amplifier with soft start,short circuit protector,with mosfet or bipolar that are easily available in india.i have two 40watts 12 inch speaker that was given by my friend.i will etch pcb.plz give me sugession and hint.thanking you.yours masood
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Old 20th July 2013, 08:37 AM   #18
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Check out Rod Elliot's P3A!!
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Old 20th July 2013, 01:28 PM   #19
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Originally Posted by diy didi View Post
Check out Rod Elliot's P3A!!
Yeah! I've done the P3a and it isn't really powerful enough for what I need.

I've sourced all of the actives for a few Destroyer DHR Turbo's. The PCB design is for 7 pairs, but trimming off the outside 2 I think I can make a 5 pair prototype first.

I'll be using 2N5401/2N5551 for the IPS, 2SC4793 for the VAS, 2SC4793/2SA1837 for drivers and 2SC5200/2SA1943 for outputs. And I've got the Zener's.

I'll be using a pair of +28-0-28 V transformers about 10 amps each.

I haven't got enough 100V Caps for the PS yet, but I've got all the others, I'm just hoping that the 100V rating is not fake. Unfortunately my resistors are only 5% so I'm going to have to check them all.

For a heat sink I'm planning on using a cylinder head from an old 2stroke Suzuki!

I'm going to be using the board design by alex mm, I can't find the post it is in in the This is DHR thread, but I saved it somewhere.
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Old 25th July 2013, 07:16 PM   #20
dangus is offline dangus  Canada
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Audio Amateur reprinted plans for a PA amp that would do about 550W into 4 ohms; I think the plans may be reprinted in the book, "Audio Amateur Power Amp Projects". Unfortunately, it was designed around the classic and discontinued Hitachi MOSFETs, but there may be substitutes by now. The plans included a board for thermal and DC offset protection.

The ETI 466 amp may be worth considering. ETI-466 Amplifier Technical Review

Another possibility: use chipamps bridged and paralleled. The LM3886 is about as cheap as a single power transistor.
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