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Old 29th November 2012, 08:09 AM   #11
AndrewT is offline AndrewT  Scotland
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A gainclone is a specific implementation.

Most chipamps are not gainclones.
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Old 1st December 2012, 01:36 AM   #12
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I'm curious if the chipamp.com kit, like the audiosector kit, was meant to be a dual mono and compact-specific design. I bought the stereo chipamp.com kit and I believe that the screamingly loud mids tone is counterproductive for music. The bus (not star) layout, the undersized NFB cap (bass block) and the undersize 100u (clearer Louder mids) amplifier board power caps seem to be the main causes, and Natsemi Spike hard clipper also contributes somewhat increased audio distortion if there's any loud playback.

Natsemi in their AN1192.pdf advises minimum of 470u power caps directly at the chip (aka amplifier board power caps). This specification partially fixes the chipamp.com stereo kit, although while 470u apparently works for parallel amp projects, maybe 1000u could be nicer for solo chips as seen in the chipamp.com kit.

I'm speculating that the dual mono kit could dull out the screaming mids by having a power board not more than 2mm away from the amplifier board. These boards are made to line up and be used as one unit. In that case, the 10,000u caps are close enough to, perhaps, swamp some midrange distortion. Hopefully, the dual mono system works well when used in compact layout--large capacitance close to the chips changes it to a "gainclone." Probably then it succeeds with inoffensive music playback. Adding up all the clues, results in 10,000u||1000u amplifier board power caps, same as the MyRef's power circuit.

P.S.
The chipamp.com kit does seem useful for television. Personally, I'd much rather have the high-end made-for-music NatSemi LME chips for a more pleasant experience with music playback.
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Last edited by danielwritesbac; 1st December 2012 at 01:40 AM.
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Old 14th November 2014, 11:20 PM   #13
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sorry to ask, but does that mean that they are not hi-fi ?
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Old 15th November 2014, 07:03 AM   #14
Philfr is offline Philfr  France
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Hi Daniel,
Comparing LM3886 dual mono kit (snubberized PS),
from Chipamp :
http://chipamp.com/docs/lm3886-manual.pdf
and Audiosector :
DIY Chip Amplifier Kits, PCB's, Components and Information.
I don't see big difference, so I think the sound of two kits are very close ?

If I understand well, you said that "10,000u||1000u amplifier board power caps" sound better, maybe much "warmer" like LM3875 ?
Phil.
PS : 2 weeks ago I build amp with Chipamp kit:
Chip Amp Photo Gallery

Last edited by Philfr; 15th November 2014 at 07:11 AM. Reason: word missing
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Old 15th November 2014, 10:06 AM   #15
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by r100 View Post
sorry to ask, but does that mean that they are not hi-fi ?
The chip is well designed.
The implementation is the part that goes wrong, often very badly wrong.

The Power Supply supplies CURRENT to the Speaker.
The chip modulates that Current.
That gives a clue to where some importance lies.
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Old 16th November 2014, 09:07 PM   #16
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Quote:
Originally Posted by danielwritesbac View Post
TWO of these: Antek - AN-2225 pair of 25+25 vac, 200va transformer
will make dual mono, and that is the answer to your question because they are what fits the chipamp.com dual mono kit.

For reference, ONE of these: Antek - AN-3225 25+25 vac, 300va transformer
would fit the chipamp.com stereo kit.

I would also like to mention:
1). Arctic brand CPU paste (has filler properties) to use with LM3886TF chips (which are covered in coarse plastic).
2). A nice big heatsink, the bigger the better.
3). Air inlet at the bottom of the enclosure (preferably underneath the heatsink), plus, air outlet at the top (or highest point of the rear panel) of the enclosure. Let the cool air in at the bottom and let the hot air out at the top so that the amplifier enclosure isn't an oven.
4). Place the input filter cap between the potentiometer and the RCA Jack (not between the potentiometer and the amplifier). If you don't plan to use a potentiometer (because you have a preamp), then add/substitute a 22k resistor (as a load) between Input + and Input - in order to maintain the integrity of the design. aka, the chipamp.com kit specs about a 10k input load, half of which is the onboard 22k resistor and the other half is the expected 20k potentiometer. Frequent reported problems with DC offset are because of input loads with higher figures than 10k (or 12k).
5). The capacitor for speaker output zobel (output RC) included with the chipamp.com kit is the wrong type. An inexpensive little polyester/mylar dip cap is typically used for zobel, not high-efficiency polypropylene, so if you get poor quality upper treble, then replace that little cap.

P.S.
Terminology:
The chipamp.com kit isn't a gainclone because its very much unlike the 47 labs original.
The audiosector.com kit IS a gainclone because its quite like the 47 labs original.
Thank's for the info. I have just ordered a dual mono kit from chipamp.com. Unfortunately the shipping of the transformers is too expensive from the US to EU so would this locally sourced transformer do ? I am a total newbee with toroidal transformers. Have only used SMPS's so far in my kits.


Buy Ring core transformer 200 VA 24 VAC (2x), Noratel, AA-58049 RM | Distrelec Switzerland

Last edited by r100; 16th November 2014 at 09:15 PM.
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Old 17th November 2014, 12:30 AM   #17
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How about these on the Apex Jr. website?
miscellaneous.html
He has information specifically for chipamp.com's amps.
Mike
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Old 17th November 2014, 07:39 AM   #18
Philfr is offline Philfr  France
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Quote:
Originally Posted by danielwritesbac View Post

I would also like to mention:
5). The capacitor for speaker output zobel (output RC) included with the chipamp.com kit is the wrong type. An inexpensive little polyester/mylar dip cap is typically used for zobel, not high-efficiency polypropylene, so if you get poor quality upper treble, then replace that little cap.
Hi,
Daniel said that in January 2010, maybe actually it's not the same ?
Today it's Vishay :
BC / Vishay 0.1uF Capacitor | Chipamp Electronics
But for Cz, what do you think of Vishay Ero MKP 1837 or Wima MKP 10 ?
Phil.
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Old 17th November 2014, 07:51 AM   #19
Philfr is offline Philfr  France
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Click the image to open in full size.

Just realized that Wima is too big !!
Vishay MKP 1837 at left on pict.
Phil.
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Old 17th November 2014, 08:54 AM   #20
JMFahey is offline JMFahey  Argentina
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Quote:
5). The capacitor for speaker output zobel (output RC) included with the chipamp.com kit is the wrong type. An inexpensive little polyester/mylar dip cap is typically used for zobel, not high-efficiency polypropylene, so if you get poor quality upper treble, then replace that little cap.
C'mon, gimme a break

It's a high impedance over all of the Audio range, 80 ohms at 20kHz , in parallel with a 4 or 8 ohms speaker, and driven by a very low internal impedance source, the chip amp.

Won't be a significant load (say, 8 ohms) until you reach 100 kHz .

No possible audible effect ... unless you skip it and the amp oscillates ... but that's another problem.

Polyester/mylar/polypropylene, even humble ceramic, are perfect in Zobel networks.

Any small internal resistance variation is swamped by the typical series 10 ohms.
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