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Chip Amps Amplifiers based on integrated circuits

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Old 26th October 2012, 03:53 PM   #51
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TDA 2006 for low's, and TDA2003 for high's, both from STMicroelectronics. The set as I have in my own made audio equipment.
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Old 27th October 2012, 03:38 AM   #52
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Some of the warm organic sound you mention can be done with a Class A preamplifier
if you're talking to me, though i think you aren't as you get technical, i won't be needing any pre-amp as the plan for me is to use a western electric minidac which has it's own preamp built in, so i'm looking to go direct into monoblocks.

as to soundstaging, i think the biggest factor there is the speakers. my former superzeros had NICE soundstaging with any consumer grade receiver i used and competed very nicely with B&W top of the line speakers on macintosh gear. they were no match for the bowers' tweeters or have anywhere near as deep a bass, but they slugged it out admirably in the soundstage department with tighter bass to low midrange. less is more.

personally, i'm not a fan of class A simply because it's the worst power hog with something like 20% efficiency when A/B is around 50% and D 80% or more. that's part of the appeal for me for a low power chip amp if it truly does offer better sonics than typical entry level gear.

i actually have a couple 15wpc class D modules i intended to use for a portable system and a 25wpc sure i should probably build to see how they fare against my panasonic, possibly even using battery power, but i'd like to try a chip amp just to hear what they sound like. besides, it should be possible to build one for under $100n easily if they're only 9 parts each.

still looking for descriptions and comparisons of different modules and/or mods.
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Old 27th October 2012, 12:37 PM   #53
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Quote:
Originally Posted by Osvaldo de Banfield View Post
TDA 2006 for low's, and TDA2003 for high's, both from STMicroelectronics. The set as I have in my own made audio equipment.
TDA2003 has singleton input. It likes to run from clean regulated power. That combination produces a gigantic soundfield easily as do many singleton input amplifiers.

It has low power, but for 8 ohm speakers it can be bridged:
Mono Audio Power Amplifier 20W 2X TDA 2003 Assembling Kit Circuit HK1002 | eBay
It takes two kits for stereo. And, it needs a heatsink.
They have forgotten the input cap and input load (or volume pot).
It would probably appreciate some RF filtering added.
It would like an additional 2200u cap added to the main power cap.
The price is very low, but, it doesn't come with a power supply.
15vdc is about max and in this case, regulated power is good.

Even bridged and run to max, it not powerful. But, it can be pretty.

Without an LTP in its design (without much power noise rejection), the TDA2003 relies on active devices at the power board for really clean DC that it needs. You can use a spare laptop power pack, or you can use a linear regulator for better quality. I'm just saying that the quality control for power is not inside the TDA2003 chip and cannot pollute the negative feedback circuit with power noise rejection traffic. The only good thing about that is, there's no chance of it throwing the baby out with the bath water. The kit represents an inexpensive way to experience the different performance of a non-LTP amplifier.
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Last edited by danielwritesbac; 27th October 2012 at 12:52 PM.
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Old 27th October 2012, 12:45 PM   #54
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Originally Posted by budget minded View Post
. . . i won't be needing any pre-amp as the plan for me is to use a western electric minidac which has it's own preamp built in, so i'm looking to go direct into monoblocks. . . .as to soundstaging, i think the biggest factor there is the speakers. . . .personally, i'm not a fan of class A simply because it's the worst power hog. . .
♦ Pretty Class A preamp consumes about as much power as a night-light bulb.
Chip amp set to lower gain gives bigger sound stage. Apparent with most chip amplifiers.
♦ Works best together, so you can hear (otherwise either too quiet at low gain or smaller soundstage if high gain)
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Last edited by danielwritesbac; 27th October 2012 at 12:49 PM.
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Old 28th October 2012, 01:05 AM   #55
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oh, you were talking about pre-amps. i just think amp & SET when i hear the word class A, but i don't like the idea of adding extra electronics in the circuit path either. that violates the KISS principle, and, if the minidac already has it's own preamp built in, then gain shouldn't be an issue. that's why i'm looking to go the monoblock route instead of getting the high rated class D integrated which, just like a class A preamp, will add distortion to the signal chain. i'm trying to do that straight wire thing.

why would you say using the minidac's own pre-amp is inferior to adding another pre-amp to the circuit? i don't buy that musical fidelity tube buffer hype myself. i don't know if the minidac is class A or not, but it has both tube and solid state outputs.

while i'm thinking of it, if i'm going direct into the amps from a pre-amp, i have to invert the amps, don't i? pre-amps invert the signal? that's an impression i got reading what i could understand here in another thread.

if you know of any good info on chip amp mods and parts upgrades, i'd like to read that. i saw someone mentioning carbon resistors to soften sound as one tweak and i know capacitors make a difference in sound, at least in speakers, but i bet in circuits too.

when you mention "setting the gain", are you talking about modifying the input with resistors or something? i really know little about circuits. i can make out a circuit diagram if it isn't too complicated, but still don't know how to read resistor directions for example.

i don't want to get too complicated and keep everything minimalist as well as easier to understand. i'd just like to make something even better than a patek if possible.
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Old 28th October 2012, 01:29 AM   #56
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while i'm thinking of it, if i'm going direct into the amps from a pre-amp, i have to invert the amps, don't i? pre-amps invert the signal? that's an impression i got reading what i could understand here in another thread.
Preamps may or may not invert the signal relative to the input. Power amps may or may not invert the signal relative to the input. Keeping absolute phase requires consideration of the entire signal path from source to speakers.
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Old 28th October 2012, 02:38 AM   #57
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OK, well if a preamp is part of a dac, it would output a "regular" non-inverted signal then, right?

here's another question, what's up with 300v+ transformers on 50wpc amps? that's a bit of overkill isn't it? i'm guessing it's the same principle as caps in the power supply.
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Old 28th October 2012, 03:20 AM   #58
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The answer to the first question could be "yes," but it is actually more involved than that, as I wrote in my first post. I doubt it's important except in an overall system viewpoint.
For the other question, I assume you mean va rather than just v. The transformer va rating is referred to the rms output. A capacitor-input power supply charges at the peak voltage, so the va must be derated to account for that. Then you have amplifier efficiencies of <25% for Class A and <78.5% for Class B, so the transformer must be derated some more. Now add some overhead for good-practices engineering and you should begin to see that 300va isn't overkill for a 100W amp.
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Old 28th October 2012, 08:49 PM   #59
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Originally Posted by budget minded View Post
Why would you say using the minidac's own pre-amp is inferior to adding another pre-amp to the circuit? i don't buy that musical fidelity tube buffer hype myself. i don't know if the minidac is class A or not, but it has both tube and solid state outputs.

while i'm thinking of it, if i'm going direct into the amps from a pre-amp, i have to invert the amps, don't i? pre-amps invert the signal? that's an impression i got reading what i could understand here in another thread.
There's no problem doing Class A with Solid State, which is nice for high resolution.
Both inverting and non-inverting are available.
Quote:
Originally Posted by budget minded View Post
when you mention "setting the gain", are you talking about modifying the input with resistors or something? i really know little about circuits. i can make out a circuit diagram if it isn't too complicated, but still don't know how to read resistor directions for example.
Have you heard the term "fixed l-pad" or "voltage divider"? Those are just volume controls that use resistors and there's no dial. Adjustment is done by replacing resistor(s).
To see your gain, divide the feedback resistor and its partner, the feedback shunt resistor and then add 1. Or see National Semiconductor Overture Design Guide and if you need spreadsheet software, Oxygen Office is free.
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Originally Posted by sofaspud View Post
Now add some overhead for good-practices engineering and you should begin to see that 300va isn't overkill for a 100W amp.
Right on! That will be low ripple. VA=watts*3 looks pretty good.
He's doing monoblocs, perhaps 50 watts each. Perhaps a pair of 150va transformers for it?
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Last edited by danielwritesbac; 28th October 2012 at 08:52 PM.
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Old 29th October 2012, 04:45 AM   #60
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Have you heard the term "fixed l-pad" or "voltage divider"?
no, i haven't heard THOSE terms, but it sounds like the same idea as a step attenuator. when you talk technical, you'll lose me. i only speak plain english.

i still don't see the point of adding an extra gain stage ahead of a DAC if that already has it's own pre-amp. you might add euphonics, but that's just another word for distortion.

part of my problem seems to be that my speakers have been really stubborn about breaking in with low level signals, but today i noticed that they really opened up and relaxed and the bass is surprisingly deep for 5 1/4" acoustic suspension. i might keep my panasonic after all and just get the DAC even if it would bother me that it has a pre-amp i don't need. i have and issues with two pre-amps.

regardless of class of amp, you can get plenty of power out of just 12 volts although class D likes 24 or even 36 i see. i'm starting to feel better about my original choice in gear now with my minimonitors starting to loosen up. i guess that etched sound was just a stiff woofer & tweeter. i've been using grey noise on them for over a week when i sleep, but last night i boosted the output a few dB and noticed much deeper bass as well as a relaxed crystal clear midrange. maybe they'll keep improving and i'll be happy with what i have. then, a chip amp in the future might just be something fun to check out. i really do like the fast clear sound of class D since my first sonic impact amp, but gainclones seem to have more warmth from what i've read.

the FIRST thing though is just getting a digital EQ and see what that does for my system. if it has lousy DACs, my receiver's sound is very similar to my sony DVD player. i guess i was just being impatient for my speakers to break in, but i'll keep following this forum to learn more. i've seen another panasonic get KOed early in an amp shootout, so i should be able to improve my sound.

i'm interested in this just for the sound and not so much the technical number crunching stuff everyone else is into. getting a parts list and a diagram of the "9 parts per channel" is as deep as i want to get into this though. i'll leave all the tech details to the hobbyists.

if i were to use the digital outputs out of the EQ and actually did need a pre-amp, i'm still inclined to go the passive less is more route. i like clinical sound actually, but my speakers WERE sounding thin a couple days ago to the point of even being bright. they're more liquid now. hope they still improve more.
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