Folsom's great little 7297 Chip Amp

mresseguie · « **Reply #980 on:** 18 Nov 2017, 12:07 pm »

Quote from: maty on 18 Nov 2017, 10:37 am

AV123 ELT525M Monitors

http://www.highfidelityreview.com/av123-elt525m.html

Other very data is the minimum impedance but few manufacturers tend to indicate it. In the rest of the speakers, through the measurements of frequency response, impedance and phase.

Maty,

Yes. You are correct.

I hadn't realized they were 83dB. All the more impressive, I think. Good job, Folsom!

I'm certain the amp needs more time to burn in. I'd like to point out that I wasn't complaining. I'm just curious if the amp might not pair so well with really resolving or really efficient speakers. I'll hear them again on/about January 31, so the amp will be very well burned in. I'll return to this thread with my thoughts then.

Michael

uncola · « **Reply #981 on:** 18 Nov 2017, 01:24 pm »

if you want to borrow a dac and preamp when you get back let me know, I have a tiny cheap dual sabre chip dac that has surprising synergy with my small hattor active preamp and the folsom amp. by then my ric schultz modded sonica dac with volume control should be here so the pair will be stored in my closet by then

Folsom · « **Reply #982 on:** 18 Nov 2017, 06:24 pm »

Quote from: mresseguie on 18 Nov 2017, 10:34 am

It's got the Jantzen caps.

200 hrs burn in for completeness, the first hours will be a little rough.

The Daedalus speakers lean towards a slight natural brightness, so it'll take a bit of time on the burn in.

Personally with Daedalus speakers I might seek a warmer sounding source component of some kind, the midrange benefits from it. I'm pretty familiar with the non-modified version of the midrange and that is my general opinion.

I've had my amp hooked up to the Daedalus DA-1.1 ver. 2 and it sounded great.

rtate · « **Reply #983 on:** 18 Nov 2017, 06:59 pm »

I have a question regarding hooking up my antek 2215 transformer.
I think that I need to hook up the input in parallel (red and black) and then hook up the output in parallel as well (green and blue).
Is this correct ?
also what do I do with the purple wire ? is this a shield ?

Folsom · « **Reply #984 on:** 18 Nov 2017, 07:35 pm »

Antek 2215 looks like

115v Primary, tie the red and red, black and black together.

Purple goes to ground (safety, earth).

15v Secondary, tie the green and green, blue and blue together.

That's cool that they offer a shield! That makes it a viable alternative to the Hammond.

rtate · « **Reply #985 on:** 18 Nov 2017, 07:43 pm »

Thanks Jeremy , I am getting close to the power on stage !
A few more hours !!

1108 · « **Reply #986 on:** 30 Nov 2017, 08:26 pm »

Anyone have a board they'd like to sell?

rtate · « **Reply #987 on:** 3 Dec 2017, 10:25 pm »

I have got one of my amps running and sounds really good but I have a little problem.
Music was playing fine and I lifted the chassis to move it slightly and all of a sudden I got a loud hum through the speakers.
I put the amp down and the hum went away however when I touch the input capacitors I also get a hum as well as the input jacks.
I measure them with my meter and they are not grounded to the chassis. Any ideas what it could be ?
I am having trouble inserting pictures but have a few in my gallery if that helps...

Folsom · « **Reply #988 on:** 3 Dec 2017, 11:05 pm »

Well it sounds like somehow you are shorting the inputs. (signal and ground touching)

Perhaps you have a cold solder on a cap or wire that has to do with the input?

It's not abnormal for the human touch to make a ground loop induce, btw. What is strange is when you lift it and it occurs.

Maybe you have a broken IC cable?

rtate · « **Reply #989 on:** 3 Dec 2017, 11:41 pm »

I removed the ic's and also lifted the earth ground from the chassis and the hum is there.
Should the heat sink be isolated from the chassis ?
Mine is anchored to and sitting on the bottom of the chassis.
The hum is loudest at the output caps even touching the paper and even louder if I touch the leads.
I can make it hum by touching other things like the heat sink and even the mounting screws from the felix.
The amp is dead quiet until I touch it and sometimes remains even after I let go...
So I isolated the heat sink from the chassis and removed the input wires from the jacks and the hum is still there and amplifies when I touch the input wires on the insulation.
When the amp was hooked up to the pre amp it was quiet until I touched the amp and would go quiet again when I let goof the amp.

Folsom · « **Reply #990 on:** 5 Dec 2017, 01:40 am »

Well, some pics may be helpful.

rtate · « **Reply #991 on:** 5 Dec 2017, 03:13 am »

sorry , I have a bunch of pics in my gallery.
I can't get them to upload.
As a update: With the amp hooked up to the preamp the Hum is gone (completely silent) even when I touch components on the amp.
If I disconnect the amp from the pre amp the hum is there loud and clear.
I completely disconnected the input wires from the chassis as well as the speaker wires so I think I can rule the chassis out , it must be on the amp board.
When the amp is connected to the preamp (pass B1) the music sounds great ! Less than 8 MV offset at the speakers.

S Clark · « **Reply #992 on:** 5 Dec 2017, 03:17 am »

Yep, I tried to upload one from your gallery and failed...

Folsom · « **Reply #993 on:** 5 Dec 2017, 06:13 am »

Well then I don't see any problems.

uncola · « **Reply #994 on:** 5 Dec 2017, 07:04 am »

*ba dum psssh*

rtate · « **Reply #995 on:** 5 Dec 2017, 11:38 am »

Thanks Jeremy ,so it's normal for the amp to create speaker hum on both channels with nothing connected to the inputs ? Or because you can't see the pictures ?

How does the pre-amp stop the hum ?

lacro · « **Reply #996 on:** 5 Dec 2017, 01:51 pm »

http://www.audiocircle.com/image.php?id=172282&size=xlarge

http://www.audiocircle.com/image.php?id=172277&size=xlarge

http://www.audiocircle.com/image.php?id=172279&size=xlarge

http://www.audiocircle.com/image.php?id=172280&size=xlarge

zek · « **Reply #997 on:** 5 Dec 2017, 02:50 pm »

Quote from: rtate on 5 Dec 2017, 11:38 am

....so it's normal for the amp to create speaker hum on both channels with nothing connected to the inputs ?

No it's not normal to be eny hum.
Carefully check the isolation of the chip and heatsink.

rtate · « **Reply #998 on:** 5 Dec 2017, 06:28 pm »

Thanks lacro for uploading the pictures !
@ zek if the chip was shorted to the heatsink would it still make music and be quiet while hooked up to the pre-amp ? I did isolate the heatsink from the chassis by sliding a piece of rubber between the heatsink and chassis with no improvement.
I'm guessing that it has to be something on the input side but I have gone over all the solder joints and component values and can't find any problems. I even unsoldered the input wires from the circuit board but still humming.
I was thinking of removing the by pass caps from under the board even though I don't think there is a problem with them

Folsom · « **Reply #999 on:** 5 Dec 2017, 09:06 pm »

I was say it is normal. Have you ever heard a guitar amp without a guitar? A fair amount of audiophile amps have a shut-off feature for events without a source connected. But this is one of the reasons why you turn on your preamp/source before the amp, as not only does it make complete circuit but it prevents loud thumps.

When the amp is connected to something it can make a complete circuit.

The pics look good. That is a pretty good sized heatsink, do you have any hole above and below it? If it gets hot that would be about the only thing you could have to do. Otherwise nice job.