74HCU04 Amp: Let's get lazy
Sep 21, 2004 at 12:27 PM Thread Starter Post #1 of 13
Tomo

Tomo

DIY tube amps can be SHOCKING
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Hi,

Good long time ago, I posted about using CMOS logic chip for analogue-fun. I was hoping someone else will do the testing so save me troubles.
very_evil_smiley.gif


Anyways, I finally got my sorta-job. So I took a day off and built me a 74HCU04 amp. The schematics is here in this application note.

http://www.fairchildsemi.com/an/AN/AN-88.pdf

I made it to run with four 1.2 NiMH's. Gain = 1. Rin = R1 = 100k (Only resistors I had) Input coupling cap is 4.7u OSCON. (Only caps I have unpacked.) The naughty thing have DC Offset due to my crappy voltage splitter. I didn't use BUF634 because of it PSU voltage is awefully close to minimum limit. (Need to come up with better scheme)

Sounds pretty good. Kinda surprising coming from a chip costing less than 50 cents. I am going to keep it as my primary for a while.

Tomo

P.S. Got any idea of improving virtual group at low voltage level?
 
Sep 30, 2004 at 12:43 AM Post #4 of 13
Tomo,

My experience with cmos chips used in the linear mode is that they are very sensitive to loading... if you load them down they rapidly loose bandwidth and gain.

YMMV, Jack
 
Oct 29, 2004 at 9:00 PM Post #6 of 13
what I'd like to try is using some higher current logic gate connected to DSD data stream in some SACD player, should be fun.. low pass filter being the headphone connected..
 
Dec 19, 2004 at 5:01 AM Post #8 of 13
Hi,

Wow Mr. Shin has done some good work there. Don't forget to bypass those. Hehe. I am crazy enough to bypass those 74HCU04's with Sanyo OSCONs; low voltage caps used on your mobo.

All in all, the complementing components cost me more than the chips themselves.

Enter the cheapophile! (Entering the dragon seems too painful and exhausting, don't you think?)

Tomo
 
Jan 25, 2005 at 9:13 PM Post #9 of 13
This is odd, but I think the STMicroelectronics version of the 74HCU04 chip sounds better than the TI version. I didn't expect any difference, but it seems a bit more "coherent" and smooth if that's possible.


Which manufact. did you use, Tomo?
 
Jan 26, 2005 at 6:33 AM Post #10 of 13
Mine's from Toshiba.

I don't think I have access to STM's stuff. Mine sounds pretty smoothe with enough mmphf. I wish I can test out other company stuff. I gotta be careful though, because I don't have output cap.

T
 
Oct 21, 2006 at 7:50 AM Post #11 of 13
Sorry to bring this up from the grave, but i was wondering if any head-fier out here could help me out and sell me one or two 74HCU04s because it is currently the only missing link in my project and i'd hate to pay shipping and handling that digikey would charge on such a small order.
 
Oct 21, 2006 at 12:18 PM Post #12 of 13
Quote:

Originally Posted by was ist los?
Sorry to bring this up from the grave, but i was wondering if any head-fier out here could help me out and sell me one or two 74HCU04s because it is currently the only missing link in my project and i'd hate to pay shipping and handling that digikey would charge on such a small order.


If you really need it desperately, I can get it from you. Farnell here has it:
http://sg.farnell.com/jsp/endecaSear...jsp?SKU=701658

I collect from their counter (near my office) and can post to you. It's about US$0.60 each. I will just include in the postage required to post them to you but that will take a week or two. Can you wait so long?

BTW - what project are you doing? I also built this amp Tomo built but its performance is very dependant on headphones used. Some phones just get no benefit from the amp.
 
Oct 22, 2006 at 7:06 AM Post #13 of 13
Hi Heady, thanks for the offer, but i must decline. I'm planning on adding a 74HCU04 amp to my alien dac. I think i'll just take apart my old 74HCU04 amp since i don't use it anymore. Once again, thanks again.
 
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