Folsom's great little 7297 Chip Amp

Folsom · « **Reply #560 on:** 4 Sep 2016, 10:16 pm »

Just try to keep the thermal grease thin. You only want it as thick as you absolutely need it. As the insulation and grease increase, the power of the amp can decrease.

ebag4 · « **Reply #561 on:** 5 Sep 2016, 12:46 am »

Thanks Lacro, the part that peeled was on the unused end so no worries.

Powered my amp up in its temporary dual case setup (built into a couple of previously used project boxes). I used a small pair of speakers and a portable player before putting it in the big rig, no magic smoke so I put it in the main system, sounds good, zero time on it. I'll let it burn in for a while and see how it comes along, but right off the bat, not bad. It has a lot more gain than the Bottlehead Kaiju, so I had to adjust the subs a bit to match the output. The gain is high enough that it is really loud at 50 on the Vega, I typically run between 75 and 85.

One nit to pick is that the transformer is loud, I currently have it on rubber feet and it is still loud, not so loud that you hear it with music playing but loud enough you hear it when you power up.

In the current setup it will be very easy to compare to a pair of 12V 100ah PowerSonic AGM batteries I have, I will report on what I find. If I end up liking the Antipole best, I will probably move to a toroidal transformer.

Best,
Ed

G Georgopoulos · « **Reply #562 on:** 5 Sep 2016, 01:57 am »

Quote from: Folsom on 4 Sep 2016, 10:16 pm

Just try to keep the thermal grease thin. You only want it as thick as you absolutely need it. As the insulation and grease increase, the power of the amp can decrease.

ah Jeremy ,what you say is really funny to me.

even if this chip has thermal protection it would be the heatsink that's causing problem
thermal grease and insulation are highly thermal conductors..

Folsom · « **Reply #563 on:** 5 Sep 2016, 02:09 am »

George, you can actually calculate the thermal resistance and how it affects things for power loss. The thing is, the insulation of the chip itself is considerably higher than say mica and grease at reasonable levels.

But when using big transistors at high voltage these factors become more serious. Mica will reduce power output a fair bit compared to keratherm.

Folsom · « **Reply #564 on:** 7 Sep 2016, 02:44 am »

Hi everyone, I found these, which might be ideal for mounting the transformer.

http://www.mcmaster.com/#rubber-standoffs/=141zebg

Style 1 & 2 make the most sense to me, as a stud sticking up into the transformer holes would be ideal it seems so long as you can get a tightening tool to it.

ebag4 · « **Reply #565 on:** 8 Sep 2016, 01:07 am »

I have let this amp play for close to 25 hrs now stepping in the room to listen on occasion. I sat down with it after work tonight to listen to a few tracks. This is a really good sounding amp, good tone, imaging, pace, etc., it has my toes tapping.

I will set it up on batteries this weekend to compare.

Great job Jeremy, certainly worth the cost and effort. As soon as I decide which of the power supplies I will use, I will be picking up better binding post, RCAs, and a suitable case.

Best,
Ed

Folsom · « **Reply #566 on:** 8 Sep 2016, 01:27 am »

Good to hear Ed. It's pretty unbeatable for the money! It's a good way into true high end audio.

Captainhemo · « **Reply #567 on:** 8 Sep 2016, 01:29 am »

Quote from: Folsom on 7 Sep 2016, 02:44 am

Hi everyone, I found these, which might be ideal for mounting the transformer.

http://www.mcmaster.com/#rubber-standoffs/=141zebg

Style 1 & 2 make the most sense to me, as a stud sticking up into the transformer holes would be ideal it seems so long as you can get a tightening tool to it.

Cool you like what you are hearing from the amp Ed :beer; I am interested to hear what you think when you power it with the batteries.

jay

lacro · « **Reply #568 on:** 11 Sep 2016, 12:58 pm »

Hey Jeremy,
Do you have issues with using these on the Antipole PS for input/output?

http://www.mouser.com/ProductDetail/TE-Connectivity-AMP/282844-2/?qs=sGAEpiMZZMvZTcaMAxB2AJ%2f79sE4hFAYCpaUmMF7fng%3d

Folsom · « **Reply #569 on:** 11 Sep 2016, 06:26 pm »

No, if they fit they work.

ebag4 · « **Reply #570 on:** 11 Sep 2016, 10:07 pm »

Quote from: Captainhemo on 8 Sep 2016, 01:29 am

Cool you like what you are hearing from the amp Ed :beer; I am interested to hear what you think when you power it with the batteries.

jay

I have been switching back and forth between the Antipole and a pair of 12VDC batts wired in series. Because I have the amp wired up to a jack for the input voltage it is quite easy to swap between the Antipole and the batts. I will say that the amp sounds great with either. One thing that surprised me a bit was that I had a very slight hum with my ear next to the 94db Wedgies drivers with both supplies, please keep in mind that this is practically inaudible and could be due to the temporary nature in which I have the amp set up (i.e. Amp not enclosed in a metal case, cables laying over each other, etc).

I played several tracks and portions of tracks with which I am quite familiar, however try as I might, I could not detect a difference, not one that I would detect repeatedly. For a few moments during the beginning of Deacon Blues I thought I heard better leading edge attack with the Antipole, but after going back and forth I could not detect the difference with any certainty.

Of course this is with my system, my room, my ears, etc., others may have more resolving systems or ears.

For the record, this is the system: NAS/Sonic Transpoter/Roon-microRendu(powered by IFi ps)-Auralic Vega DAC- Folsom amp & Servo Sub Amp (x2)- GR Research Wedgies, Servo Sub Amps drive 2x12" servo drivers housed in an "H" Frame alignment housing per channel AC Devices: Powered through Pi Audio Uber & Majik Busses Cables: microRendu hard USB connector, High Fidelity CT-1 RCA (DAC to Amp), Monster RCA (DAC to Servo amps), Morrow Audio Sp-5 speaker cables.

Best,
Ed

S Clark · « **Reply #571 on:** 11 Sep 2016, 10:43 pm »

Thanks for the review. It's one I've been waiting for, since I've been on batteries all this time. I've got an Antipole board, but I haven't gotten around to filling it yet... so I'll probably continue to procrastinate.

Folsom · « **Reply #572 on:** 11 Sep 2016, 11:15 pm »

Try putting an RC of 10r 1uf across the transformer side of the CMC. (a resistor and capacitor in series, one leg of resistor attached to one leg of CMC towards AC input and one leg of capacitor to the other CMC leg toward AC input)

See if you can tell the difference after that.

ebag4 · « **Reply #573 on:** 11 Sep 2016, 11:53 pm »

Quote from: Folsom on 11 Sep 2016, 11:15 pm

Try putting an RC of 10r 1uf across the transformer side of the CMC. (a resistor and capacitor in series, one leg of resistor attached to one leg of CMC towards AC input and one leg of capacitor to the other CMC leg toward AC input)

See if you can tell the difference after that.

I may have those parts in my collection. Where exactly should it be mounted?

Thanks,
Ed

Folsom · « **Reply #574 on:** 12 Sep 2016, 12:12 am »

I'm not sure how to explain it any more...

ebag4 · « **Reply #575 on:** 12 Sep 2016, 12:36 am »

Quote from: Folsom on 12 Sep 2016, 12:12 am

I'm not sure how to explain it any more...

How about pointing out the CMC.

Captainhemo · « **Reply #576 on:** 12 Sep 2016, 12:41 am »

Won't you be good pretty much anywhere on the input side of the trans ? Keeping it close will probably be easier....

jay

Folsom · « **Reply #577 on:** 12 Sep 2016, 01:36 am »

Quote from: Captainhemo on 12 Sep 2016, 12:41 am

Won't you be good pretty much anywhere on the input side of the trans ? Keeping it close will probably be easier....

jay

The best location will be closest to the CMC.

CMC is the common mode choke. It's big, has wires around a core.

ebag4 · « **Reply #578 on:** 12 Sep 2016, 01:42 am »

Quote from: Folsom on 12 Sep 2016, 01:36 am

The best location will be closest to the CMC.

CMC is the common mode choke. It's big, has wires around a core.

The choke, now I know what you are referencing.

Thanks,
Ed

BRN · « **Reply #579 on:** 12 Sep 2016, 03:22 am »

I can understand why any differences between the battery supply and the Antipole would be almost indistinguishable, because of the power regulation on the amp. The Antipole has the CMC and caps before the regulators to help clean the A/C coming in and a lot of capacitance after for the D/C. This should provide a nice clean source for the amp.

To this point I have been very happy with the amp and have not felt any urge to look for something else.

Brad