Folsom's great little 7297 Chip Amp

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WC

Re: Folsom's great little 7297 Chip Amp
« Reply #780 on: 9 Feb 2017, 05:31 pm »
I'm out of boards again.

Are you going to make any more?

walkern

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Re: Folsom's great little 7297 Chip Amp
« Reply #781 on: 11 Feb 2017, 04:52 pm »
I just finished up construction of an Aikido line stage to use with my Folsom amp.  I love the way the Sainsmart sounds with the little 7297, but I was curious about how much better a tube line stage might be with better parts and circuit design and boards etc.   The Aikido cost me about 3 times what the Sainsmart did (using stock board and parts from John Broskie, NOS Sylvania 12AU7s, a resistor based stepped attenuator, and decent but not exotic in and output RCA connectors as well as ONO copper and silver hook up wire) but is still C&C, and it does seem to allow me to get a bit more out of the Folsom amp. The dynamics are improved slightly, as is soundstaging and clarity. Overall I am happy with the Aikido, but it is not 3 times better than the Sainsmart and was a great deal more work to get up and running.

In any case, as best I can tell, the Folsom amp will reveal improvements in associated gear and remains (IMHO) a fantastic bargain.  No surprise that you are out of boards again.

Beardy

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Re: Folsom's great little 7297 Chip Amp
« Reply #782 on: 17 Feb 2017, 01:20 am »
Hi All,

Looking to crowd source here...

Given Folsom is out of boards, what board/sell/origin would you recommend?

I like the idea of a battery supply and this is a convenient deign for a 12V supply it seems like a good time to mess about with this approach.  I have read that you want to add `low impedance’ capacitors as well  - I am assuming that the impedance of the battery is significant and this helps in some way to provide a rapidly responding infinite current source…  is this a near-accurate approximation of what’s going on and what would you suggest?

The crosstalk is noted on the spec sheet at 46db (and typically 60db) – is there anything to be gained in buying two and building up two independent amps or is it more of a case that it can’t be worse, it may be better and it’s so low cost as to not be a concern…? 
I also note Danny's comments about double the current capability, damping etc.  so maybe there are some other potential benefits outside of crosstalk I am missing.  I would guess that the high current capability of a battery supply minimizes the potential benefit of getting away from sharing a single current source.

I have just learned that my BDP-103 uses a digital volume control that loses bits at lower volume levels.  So I need some sort of preamp/volume control.  Output impedance for the OPPO is 100ohms (allegedly) and perhaps I could get away with a passive volume control but otherwise I need to use some volume control on the amp.  I know that the one on the pcb’s from china are not great – what would you recommend (to save me reading back through 40 pages)?

I would guess that the heat sinks on the low cost boards are likely to be places where money can be saved so does any one notice their amps running hot - and just to confirm it the heat sink `live' or grounded (does it need to be isolated from the chip or everything else?

I am sure I will come up with more questions, but your help is gratefully appreciated.
thanks
Beardy

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #783 on: 17 Feb 2017, 03:10 am »
1. I don't know anyone selling another board.

2. eBay boards are compatible with 12v, mine technically isn't for full benefit. 3. Yes capacitors lower noise from battery.

4. Crosstalk figures are probably meaningless. As far as I can tell there's no audio frequency crosstalk to speak of really, as the figure is probably based on tid bits of RF (this is common, to rate chips at crosstalk in unused frequencies). 5. You can gain some current from monoblocking, but that only helps with impedance dips. Proper implementation needs a ballast resistor and I can't inform you of the value on that without a lot of work to test.

6. You loose "bits" on most analog volume controls too, it's not as big of a deal as you might think. My recommendations are you begin to close in on an external DAC to use that has volume, since the Oppo is just OK. 7. Several people have really been digging that little tube-pre mentioned.

8. The low cost boards are probably steel traces, they're single sided, often mislabeled, use all super cheap parts, and use second rate chips that didn't pass quality control to be able to handle full specified voltages.




I'd be happy to print some boards, if there was a min order. It takes about 25-30 orders, of both boards. But so far since I've run out it's been a slow trickle, so it's hard to assume that I can get that min order.







lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #784 on: 17 Feb 2017, 03:04 pm »
Quote from: Folsom link=topic=138229.msg1589811#msg1589811 date=14873010
[b
I'd be happy to print some boards, if there was a min order.[/b] It takes about 25-30 orders, of both boards. But so far since I've run out it's been a slow trickle, so it's hard to assume that I can get that min order.

I for one hate to see this superb sounding amp die on the vine for lack of boards. Why not just start a Group Buy list here where buyers add there name. When the list gets to the predetermined quantity needed, a call for payment is sent to each person on the list.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #785 on: 17 Feb 2017, 11:38 pm »
Where should I post a GB thread?

Letitroll98

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Re: Folsom's great little 7297 Chip Amp
« Reply #786 on: 18 Feb 2017, 04:58 am »
Unfortunately you can't post a group buy.  For Industry Participants like you that are not making any real money on these boards we may make an exception and allow that model you've been using of "hey I have some boards, pm me".  And the exception is a tradition, not a rule, so is always subject to the powers that be.  A group buy thread would have to be started by a non-IP member in the appropriate circle, this one in this instance, and would have to organize and run the group buy.

I think if you let a short stretch pass interest will build back up again.  The thread has been going this long, so members are still interested and posting.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #787 on: 18 Feb 2017, 05:00 am »
Thank you, I knew I should ask.

If someone else wants to head up a group buy, that works for me!

WC

Re: Folsom's great little 7297 Chip Amp
« Reply #788 on: 20 Feb 2017, 04:13 am »
Just completed my latest Folsom amp. I couldn't find a case I liked, so I built my own. I am totally blown away by the sound quality of this one. It's my fourth build, but this one has the Antipole PS with a Lundahl transformer powering it. The amp has the stock BOM except the input caps are Clarity ESA. I have about 100 hours on it, and it is by far the best sounding yet. I have previously only used an SMPS to power these amps. I just can't get over how good this new one sounds. I can listen for hours without fatigue. Jeremy: This is one great design, and I hope you decide to offer another batch of cards so many others can build, and enjoy this superb sounding amplifier!



How did you wire up the LED for the front power button?

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #789 on: 20 Feb 2017, 03:53 pm »
How did you wire up the LED for the front power button?

There is a wiring diagram at the E-bay sellers listing, link below. The switch LED is 12V, so I used a resistor with the higher voltage supply of the Antipole PS. I don't like super bright LED's so I used a variable resistor (trimmer) to get the illumination I wanted, and then installed a fixed resistor of that R on the switch.


 http://www.ebay.com/itm/16mm-12V-Latching-Push-Button-Power-Switch-Black-Metal-Blue-LED-Waterproof-/141819074705?hash=item2105135891:g:x4QAAOSwdGFYqjOD


KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #790 on: 17 Mar 2017, 01:31 pm »
I've been enjoying listening to my Folsom 7297 amp and since completing the Pass B1 buffer and placing it before the amplifier it even sounds better .
The transformer makes a little noise but unless you're sitting next to it it is not an issue .
The amp is pretty revealing and has good treble and low end reproduction .

WC

Re: Folsom's great little 7297 Chip Amp
« Reply #791 on: 17 Mar 2017, 02:13 pm »
I've been enjoying listening to my Folsom 7297 amp and since completing the Pass B1 buffer and placing it before the amplifier it even sounds better .
The transformer makes a little noise but unless you're sitting next to it it is not an issue .
The amp is pretty revealing and has good treble and low end reproduction .

Which transformer did you use?

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #792 on: 17 Mar 2017, 05:17 pm »
The Hammond model in the designers BOM .
It just has a slight audible hum when powered . I have ithe mounting brackets resting on some thin pieces of rubber and there are also rubber washers on the mounting bolts . I will add a layer of rubber on the top of the case to see if it minimizes the hum as the top of the transformer is very close to the case top

Odal3

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Re: Folsom's great little 7297 Chip Amp
« Reply #793 on: 17 Mar 2017, 06:22 pm »
I have had good results reducing hum by using moon gel under the feet of other power supplies that I have used.
Not sure if it will help in your situation but it's only $7

http://www.guitarcenter.com/RTOM/Moongel-Percussion-Dampening-Gels-1274115039839.gc

absolutk

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Re: Folsom's great little 7297 Chip Amp
« Reply #794 on: 20 Mar 2017, 01:59 am »
SO many great builds in here! Alas, I'm not in a position to start mine anytime soon so my boards are sitting in their anti-static bags since purchase. Anyone interested, please send me a PM or leave a note here.

indosmokejon

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Re: Folsom's great little 7297 Chip Amp
« Reply #795 on: 23 Apr 2017, 07:40 pm »
Hi there. Not sure how many people still have boards out there that are looking for a proper enclosure for their builds. I ran across these on eBay and bought 2 for the builds of the Folsom that I have been planning. They seem to be a great size, they have a built in divider, power cord, heat sink and many other odds and ends. When I get mine I will open it up and take some pics and share with everyone the specifics. I will include a link to the item. I made a "best offer" as well and only paid $30/per to the door!

https://www.ebay.com/itm/192164116930

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #796 on: 23 Apr 2017, 09:54 pm »
Thanks for the heads up on the NABU cases jon
 I used the same one for my chip amp build and I think I paid a little more with shipping from SS,  so its a good deal .
I'll probably pick another one up for future projects

S Clark

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Re: Folsom's great little 7297 Chip Amp
« Reply #797 on: 24 Apr 2017, 01:02 am »
They turned down $32, so it may take $35+ to buy one.

indosmokejon

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Re: Folsom's great little 7297 Chip Amp
« Reply #798 on: 24 Apr 2017, 01:23 am »
I realize now after reading almost all the way through this build thread again that the NABU chassis is in fact mentioned many times over and even pictured by other builders. Oh well, just trying to look out for people here!  I am excited to get mine and start building.

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #799 on: 26 Apr 2017, 06:48 pm »
Just tried putting my Little Dot MkII+ tube headphone/preamp in front of the Folsom amp .
Not really any improvement and clicking sounds when turning the DACT so ...test over . Out it comes
The Little Dot does improve the sound of my modded Audio Source Amp 100 though !