Folsom's great little 7297 Chip Amp

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Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1060 on: 30 Dec 2018, 11:33 pm »
For the shop it'd probably be fine, but I'm not sure why you'd build it when you can get something real cheap.

WC

Re: Folsom's great little 7297 Chip Amp
« Reply #1061 on: 31 Dec 2018, 04:47 am »
If I wanted something cheap (no additional cost) I would keep using my 25 year old Denon receiver. Well I have all variety of DIY amps (about 14 channels) that I have boards for and I have the parts for most of them. The Folsom amp is actually the least expensive amp build. Need to find a place for all my amps.  :)

The Soekris DAC will also be feeding my main 2 channel system, when I get my preamp built, so it is pulling double duty.

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1062 on: 16 Jan 2019, 02:10 am »



hey guys. tested my anti pole and got about 19.8 volts. I have a blue 3.3 watt led on the aux with a 1.0k 1/2 watt resistor. using the antek AS-1215 trafo. does that voltage sound ok?

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1063 on: 19 Jan 2019, 02:47 am »
Little amp is up and running. Sounds phenomenal! Only an hour or two on it yet. Thanks so much for the great project. Really nice build directions. The amp really transformed the Elac 6.2s. Very fun to build. I ordered a Furutech IEC out to change out for the cheapo one that came with my case. Will wait a bit to see how it evolves.

Thanks again!
Jeff

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1064 on: 19 Jan 2019, 04:33 am »
Sorry, I missed it. That transformer is lower voltage than you should use.

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1065 on: 19 Jan 2019, 11:47 am »
Not a big deal to swap out to the Antek 1218. I assume the 1215 is not enough to activate the Infinite Capacitor? The 1218 transformer is only $21 (plus shipping). I need to change out the IEC connector as well. Bought a Furutech to replace the one that came with the case.

Is the 1/2 watt resistor on the LED adequate? I have 3 watts that could work or I guess I could use 2, 1/2 watts in parallel.

Thanks again for the project. It really sounds nice.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1066 on: 19 Jan 2019, 07:09 pm »
You're correct on the voltage.

What LED?

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1067 on: 19 Jan 2019, 11:58 pm »
I added an LED to the auxiliary outputs on the Antipole. It is a 3.3 watt blue. I was calculating the resistor value projecting a 17 v output from the Antipole. in actuality it is 19.8 and will be more once I add the new 100 VA 18v transformer. I will likely need to change the resistor. Wasn't sure if a 1/2 watt resistor is sufficient and was curious if having an LED reduced the output of the Antipole.

Folsom


drew_t

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Re: Folsom's great little 7297 Chip Amp
« Reply #1069 on: 22 Jan 2019, 10:53 pm »
Sorry, I missed it. That transformer is lower voltage than you should use.

I thought you said that one was OK?
https://www.audiocircle.com/index.php?topic=138229.msg1553726;topicseen#msg1553726

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1070 on: 22 Jan 2019, 11:01 pm »
I thought you said that one was OK?
https://www.audiocircle.com/index.php?topic=138229.msg1553726;topicseen#msg1553726

I must have only been looking at the VA rating, sorry.

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1071 on: 26 Jan 2019, 10:45 pm »
Replaced the IEC receptacle and the transformer, Fired it up and only have one channel working. Moved around cables and isolated it to the L channel of the amp. Opened up the amp and power is good going into the Antipole but only has one side coming out (the + side has 24v and the - is really low ~0.2v). Turned on the variac to about 70v and started measuring. Power is consistent across all 4 legs of the choke and across all 6 of the 2.2uf capacitors. Two of the diodes have ~6v on one leg and 12v on the other (with variac at 70v). The other 2 have ~6v on one leg and 0v on the other. All 4 of the big caps have about 12v on one leg. I can include pics if helpful. Am guessing I have trashed 2 of the diodes. The 2 "bad" ones are not adjacent. If you are looking at the top of the board with choke end close to you, it is the left diode and second from the right.

Any other measurements you recommend or just replace the 2 diodes?
Thanks for any input!
Jeff

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1072 on: 26 Jan 2019, 11:52 pm »
Your left channel probably has a binding post touching chassis or something.

There is no center tap, so you are suppose to be just getting 24v.

yardbird

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Re: Folsom's great little 7297 Chip Amp
« Reply #1073 on: 27 Jan 2019, 12:31 am »
Antipole is fine. Cold solder joint on an RCA. Stereo has returned!

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1074 on: 27 Jan 2019, 01:33 am »
 :thumb:

DougD

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Re: Folsom's great little 7297 Chip Amp
« Reply #1075 on: 28 Jan 2019, 02:19 am »
Finally started after having the boards for a year (or so). I seem to have lost the BC337-40 transistor that Folsom sent with the boards, can I get a suggested part# for a replacement. There seem to be a lot of options at Mouser and I barely know what I'm working with. Also, on the D45H11G, I've noticed that in pictures of populated boards some have a heat sink attached to the black metal clip. Is the black metal clip sufficient heat sink, or does the transistor need more?
Thanks,
Doug







DougD

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Re: Folsom's great little 7297 Chip Amp
« Reply #1076 on: 6 Feb 2019, 09:33 pm »
Found that little bugger and soldered it in. Finished the anti-pole board. Start working on the case now


Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #1077 on: 6 Feb 2019, 10:04 pm »
Oh , good. Nothing on mouser will work. I have back stock for awhile and can get more.

rockdrummer

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Re: Folsom's great little 7297 Chip Amp
« Reply #1078 on: 13 Feb 2019, 03:51 pm »
Hi everyone.  Got my boards for this amp last week!  I'm so excited to start on this build.

I have come to the decision that I will order a chassis from DIYAudio Store.  I have done lots of reading on this thread, and I know some have hired out companies to drill out of the chassis for parts installation.  Is that the way to go if I haven't ever drilled through metal before? 

Am I wrong in thinking that it just takes having the right bit to drill through aluminum? 

Also, I will need to get the parts ahead of ordering the chassis because I will need lots of planning to know where I want to put things. 

Any advice?  I have built bottlehead products before, several pairs of GR Research speakers/subs before, but I have never had to plan a layout for an amp and needed to drill myself.


I have many more questions but I will have to wait to start spewing them out.
Thanks.
Ben

S Clark

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  • measurement? We don't need no stinkin measurement
Re: Folsom's great little 7297 Chip Amp
« Reply #1079 on: 13 Feb 2019, 04:50 pm »
Drilling aluminum is like going through butter. You don't need anything special, just a drill and a bit.