Folsom's great little 7297 Chip Amp

Folsom · « **Reply #860 on:** 18 Aug 2017, 05:03 pm »

1. 18v>15v. 15v might be cut out under load from providing enough power. 18v will produce a little more heat is all.

2. The square one was saturating a tiny bit. It had a warmish sound but the round one has dynamics and stuff that are more accurate.

ebag4 · « **Reply #861 on:** 18 Aug 2017, 05:11 pm »

Quote from: BRN on 18 Aug 2017, 04:22 am

Ed,

The chassis looks nice. Where did you get it?

Thanks,
Brad

Thanks Brad. I would like to tell you but I honestly don't recall. This case has housed several amp kits throughout the years, I have had it for more than 10 years. They are still available I believe, I see others using the same or similar case every so often.

Best,
Ed

Edit: I also received my new boards, thanks Jeremy.

BRN · « **Reply #862 on:** 19 Aug 2017, 12:51 am »

Ed,

No problem. Does your chassis have a divider that separates the PS from the amp?

Thanks,
Brad

ebag4 · « **Reply #863 on:** 19 Aug 2017, 01:13 am »

Quote from: BRN on 19 Aug 2017, 12:51 am

Ed,

No problem. Does your chassis have a divider that separates the PS from the amp?

Thanks,
Brad

Hey Brad, no it does not although I did consider fabricating something. In the end I just put it together, the end result sounds very good. It's not my best work so I didn't post any pics, but here it is with the Antec transformer (which made a great improvement over the Hammond):

Best,
Ed

Folsom · « **Reply #864 on:** 19 Aug 2017, 02:16 am »

How would you compare the hammond to antek in a little more descriptive language?

rtate · « **Reply #865 on:** 19 Aug 2017, 03:37 am »

@ ebag4 , also is it 18v or 15v secondary's ?

Edit , I saw an earlier post that had the model # (15y)

Voncarlos · « **Reply #866 on:** 19 Aug 2017, 12:56 pm »

Quote from: ebag4 on 19 Aug 2017, 01:13 am

Hi eBag4

If I could, I would like to make a suggestion tip that was given to me by Rick Schultz, and to which I implemented in my own SS amps.
Remove that large ferrous metal bolt and nut running up through the transformer and replace them with a plastic bolt.
This made a very obvious difference to me for the better.
If I recall correctly, it brought out more clarity and detail in my system.
I should also add that I got rid of the large metal plate on top and substituted a piece of 1/8th inch plywood.

ebag4 · « **Reply #867 on:** 19 Aug 2017, 02:45 pm »

Quote from: Folsom on 19 Aug 2017, 02:16 am

How would you compare the hammond to antek in a little more descriptive language?

Hi Jeremy, no audiophile terminology required to describe the difference, the Hammond had a constant low level mechanical and electrical hum, I had it mounted on rubber in a separate enclosure and still had the problem. The antec has no self noise that I can hear.

Quote from: rtate on 19 Aug 2017, 03:37 am

@ ebag4 , also is it 18v or 15v secondary's ?

Edit , I saw an earlier post that had the model # (15y)

Hi rtate, I am using the 15V secondary as recommended earlier in this thread. I will use it again for my next amp.

Quote from: Voncarlos on 19 Aug 2017, 12:56 pm

Hi eBag4

If I could, I would like to make a suggestion tip that was given to me by Rick Schultz, and to which I implemented in my own SS amps.
Remove that large ferrous metal bolt and nut running up through the transformer and replace them with a plastic bolt.
This made a very obvious difference to me for the better.
If I recall correctly, it brought out more clarity and detail in my system.
I should also add that I got rid of the large metal plate on top and substituted a piece of 1/8th inch plywood.

Hi Voncarlos, thanks for the recommendation, that's an easy change to try,

Best,
Ed

limits · « **Reply #868 on:** 27 Aug 2017, 05:23 pm »

Hi everyone--I got my second Folsom 7297 amp, which uses the current version of both the antipole and amp boards, finished on Friday! Once again, I would like to thank Jeremy for offering them again, and also for tweaking the design of both boards.

After a rough set of mistakes I made on the first build, I wanted to challenge myself to have an easier time putting together another one and possibly improve on a thing or two over amp #1. Maybe even have some fun in the process...

I probably wouldn't have bothered taking on another one, except, despite all the uphill battles at getting the first one to work, it sounds damn good. So...Onward...

This one uses Folsom's updated BOM, with the exception of the under-board bypass caps and I also went with the original TI transistor instead of the ON part. The biggest substitution I made was using the Antek 200 VA transformer instead of the Hammond on my first build...Try as I might, I could never eliminate the hum completely from it, which was annoying because otherwise the amp was so good. Imaging and detail are just scary good...

I also incorporated a Felix line filter in front of the transformer primaries. I don't know how great of difference, good or bad, it made, but man, I will say the 3d imaging I am getting--even early on--from this amp is amazing!!

It has been playing almost continually since Friday night, and has really smoothed out since then, with the bonus of an absolutely black, silent background when music isn't playing

So here are some pics...

pocomo · « **Reply #869 on:** 27 Aug 2017, 09:50 pm »

Looks awesome, congrats lims!

Folsom · « **Reply #870 on:** 28 Aug 2017, 01:03 am »

xsb7244 · « **Reply #871 on:** 28 Aug 2017, 08:26 pm »

Folsom,

Do you have a website? Facebook?

Folsom · « **Reply #872 on:** 29 Aug 2017, 12:21 am »

Neither. A website will come at some point.

undertowogt1 · « **Reply #873 on:** 29 Aug 2017, 01:21 am »

Quote from: limits on 27 Aug 2017, 05:23 pm

Hi everyone--I got my second Folsom 7297 amp, which uses the current version of both the antipole and amp boards, finished on Friday! Once again, I would like to thank Jeremy for offering them again, and also for tweaking the design of both boards.

After a rough set of mistakes I made on the first build, I wanted to challenge myself to have an easier time putting together another one and possibly improve on a thing or two over amp #1. Maybe even have some fun in the process... I probably wouldn't have bothered taking on another one, except, despite all the uphill battles at getting the first one to work, it sounds damn good. So...Onward...

This one uses Folsom's updated BOM, with the exception of the under-board bypass caps and I also went with the original TI transistor instead of the ON part. The biggest substitution I made was using the Antek 200 VA transformer instead of the Hammond on my first build...Try as I might, I could never eliminate the hum completely from it, which was annoying because otherwise the amp was so good. Imaging and detail are just scary good...

I also incorporated a Felix line filter in front of the transformer primaries. I don't know how great of difference, good or bad, it made, but man, I will say the 3d imaging I am getting--even early on--from this amp is amazing!!

It has been playing almost continually since Friday night, and has really smoothed out since then, with the bonus of an absolutely black, silent background when music isn't playing

So here are some pics...

limits, what size enclose did you go with, L / W / H ? and Brand?

BRN · « **Reply #874 on:** 29 Aug 2017, 02:56 am »

Limits,

You build looks great. I can't wait to start my next Folsom amp.

Brad

limits · « **Reply #875 on:** 29 Aug 2017, 02:04 pm »

Thanks, guys!

Can't wait to see your next build, Brad--you always do great work!

Quote from: undertowogt1 on 29 Aug 2017, 01:21 am

limits, what size enclose did you go with, L / W / H ? and Brand?

undertowotg1--I went with a chassis from the diyaudio store:

1 x Pesante 3U - Quantity 1 / 300mm / 10mm Silver for $117.00 each
Rear Panel IEC Socket Option:Without IEC Socket
Handles:None
Baseplate:I'd like a baseplate
Baseplate Depth (Match your chassis depth):300mm
How many 300mm deep baseplates?:1 x 300mm deep baseplate [Add $12.00]
Feet:Anti-Vibration Feet
Feet Quantity:1 set (4 pieces) of Anti-Vibration feet [Add $16.00]
Customization:None

Kind of expensive but it looks nice. I would highly recommend getting the baseplate. It makes assembly a lot easier, as you have open access to everything, and once you get everything built (except soldering the input/output connections) you can just drop in the baseplate and complete the build.

limits

undertowogt1 · « **Reply #876 on:** 29 Aug 2017, 07:33 pm »

thank you for the detailed respone Limits

undertowogt1 · « **Reply #877 on:** 7 Sep 2017, 02:16 am »

I am in the process of ordering my parts for the Folsom AMP.... I am a total newbie at this

, I have built other audio related things but nothing like an amplifier. I may be relying on this thread a little to much during my build, only time will tell. I went ahead and splurged on the case and got the same case limits used, they do look nice.

For my second question.....As far as the heat sink is concerned what size should I be aiming for? Whats the deal with this aspect of the build?

Thanks.

undertowogt1 · « **Reply #878 on:** 9 Sep 2017, 01:31 am »

Quote from: undertowogt1 on 7 Sep 2017, 02:16 am

I am in the process of ordering my parts for the Folsom AMP.... I am a total newbie at this , I have built other audio related things but nothing like an amplifier. I may be relying on this thread a little to much during my build, only time will tell. I went ahead and splurged on the case and got the same case limits used, they do look nice.

For my second question.....As far as the heat sink is concerned what size should I be aiming for? Whats the deal with this aspect of the build?

Thanks.

I have been looking on Mouser and some pics of other members builds. Would a HALF BRICK designed for adhesive work? So many choices on Mouser!

undertowogt1 · « **Reply #879 on:** 15 Sep 2017, 03:29 am »

So I have started my build, I did the antipole first to get in the groove again. I was pretty straight forward. Now I guess I am on the harder part, mounting the chip and soldering the chip. The solder holes are pretty close in this area. I assume it is an issue if the legs on the chip touch other legs. Anyone have some tips for this area of the build.