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Old 3rd July 2007, 06:06 PM   #1
alexcd is offline alexcd  United States
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Default Driver chips for BPA300 amplifier

I wanted to start this over in a new thread

Quote:
Originally posted by alexcd
I think I've decided to use the OPA1632 to drive the BPA300. Maybe some others want to get in on a group buy of the boards. I'll do the layout.

Quote:
Originally posted by tryonziess
that mean you are going to design a useable driver with this chip. make the boards as good as alex88 and i want some. have you noticed the neat bridges jrdg uses to transfer the output power in there amps. nice thick elevated copper covered in epoxy. nice!! if you can machine out about 75 pounds of solid aluminum for the case we could have some amps like that. otherwise 8000 dollars u.s. i am going to build my own thanks to alex boards. have fun

Quote:
Originally posted by alexw88
The spec of OPA1632 is very good. Just use a good standard opamp to drive it.

Quote:
Originally posted by alexcd
Haha, I am absolutely not planning on using that much aluminum in my amp. I'm doing 2 channels + seperate dual power supply using 1/4" aluminum. I have some access to a machine shop but let's not talk crazy now.

I planned on following the OPA1632 datasheet exactly. If you want in, it would be cheaper for me to order more. Any extra ideas are welcome. I will start another thread if interest continues.

Quote:
Originally posted by alexcd


"Differential input sources must have well-balanced or low-source impedance." - OPA1632 datasheet p6

This isn't a problem for me but I can see why it would be nice to have additional buffering. Two opamp then, right?

Quote:
Originally posted by alexw88
1 opamp if you want to use it with single-ended input only.

2 opamps if you want to use it with balanced input as well as single ended input. I think this option has more flexibility.

I have thought of IF I would built it (ok, I won't), I will build a 3-section board that can be cut into 3 pieces and be able to use them seperately.
The 3 sections are : voltage regulation, dual opamps buffer, differential opamp line driver.

This way I can reuse these 3 modules for different applications, e.g. preamp, DAC, etc. Also this saves PCB setup cost.

Quote:
Originally posted by alexcd
haha, Thanks for the idea. That is a good one. I was thinking the same thing. I was planning on a separate +/-15V regulator board but why bother if I'm using it for here only. BTW, I was going to use my mains 25VAC and regulate down to the +/-15V with a separate diode bridge. It should be no more than a small heatsink's worth of heat for just this circuit, right?

Quote:
Originally posted by alexw88
Regulate 25VAC down to 15VAC should be ok, that's what I am doing in my amp. There is not much heat since the current is small.
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Old 3rd July 2007, 06:30 PM   #2
BWRX is offline BWRX  United States
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It looks like your questions were answered. What then is the point of this thread?
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Old 3rd July 2007, 06:40 PM   #3
alexcd is offline alexcd  United States
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The point is that OPA1632 may or may not be the right choice here. I would also like to find out if anyone else has a need for a line driver or other use for this circuit and wants to give input. I would like to make PCB's but obviously the more people the merrier.
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Old 3rd July 2007, 07:00 PM   #4
alexcd is offline alexcd  United States
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http://www.thatcorp.com/datashts/1600data.pdf

Anyone ever heard of this brand?
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Old 3rd July 2007, 09:11 PM   #5
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is the opa chip better in this application than the ths from ti. you will need to provide a balanced line in from 2 op to the ths/opa1692 i guess. now is this far superior to a standard drv134 setup. the only really good point is the cmrr of the new ths is as good as a transformer. when you get the board built let me know i will need a few. still have not ruled out the lundahl transformer. there is also a good schematic at ti about this chip and the transformer in combination. with .000? thd on this amp i really do not want to garbage it up. so any help is appreciated. if you have access to a milling machine melt down a couple thousand beer cans and mill out a jrdg billet case. would be nice.
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Old 4th July 2007, 12:47 AM   #6
alexcd is offline alexcd  United States
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Good questions. I was hoping for someone to ask them. Personally, I think that a OPA2227/OPA1632 would be a mean combination with no worse than 1% resistors. I am more worried about the effects of the resistors than the chips.

That case idea sounds good but only if Sam Adams starts putting beer in cans. I wouldnt want cheap beer getting in my project.
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Old 4th July 2007, 01:22 AM   #7
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THS4131 and OPA1632 are pin compatible if you keep pin 7 open. You can use the same pcb and try both chips.

For resistors, I agree 1% or even 0.1% should be used. You could hand match the 1% to get better accuracy.

What voltage regulator will you use? Ever thought of the new low noise LT1763?
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Old 4th July 2007, 01:26 AM   #8
alexcd is offline alexcd  United States
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I never give regulators much thought... usually the cheapest
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Old 4th July 2007, 11:34 AM   #9
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more and more projects are requiring 0.1 or better resistors. has anyone found a place to buy bulk precision resistors in varying values at a reasonable price. i never thought the cost of resistors would enter the equation, but now its has. you can buy a fairchild op amp for less than a 0.1 vishay/dale resistor. any of you ever heard a leach amp playing music. i have been thinking about building a discrete amp after the chipamp projects. it looks like leach spent quite a lot of time debugging the original design and it should be quite reliable with present day components.
you could always melt the sam adams bottles and machine with diamond tooling. that would be one nice case. back light with leds. there are no limits imposed on diy projects just time. good choice in your brew.
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Old 4th July 2007, 11:48 AM   #10
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Default that driver

i just read the datasheet on the that line driver. it looks to be a dropin driver with all the advatages of the ths/opa and all in on little dip8 chip. price is about 3.00 dollars. you could mount it right on the main board. they also have some other neat stuff and mouser sells their products. i might give this little unit a go.
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