Gainclone up and running with some problem

kmj · 10th January 2005, 12:19 PM

Well, it seems that the gainclone indeed is simple to build, however i'm havin som minor problems (ofcourse )

.

The amp is Brians basic kit with a transformer 24x24V @300VA (unrectified).

When i was going to measure the DC-ofset (between the speakerterminals on each shannel, right?) i got a low value on the right one, about 2.0 at the lowest setting. On the left however, i didn't even get a value.... No indication whatsoever. The 3 groundcables is connected at one point in the chassi but not to the outlet in the wall, so to speak. No grounded output in the building.

When i turned it on, with my CD-walkman connected, a rythmic zapping eminated from the left speaker. A hightening in intencity occured when i raised the volume. It is not a hum but more like a Sci-fi Zapping sound, Tzing!. (sorry for the bad explanation).

Any ideas how to get rid of it?

Best regards!

P.S.
The chip is connected to an Aluminum heatzink 7x7cm and from 3 to 10mm thick depending if you measure at the point och connection or higher up where there are ridges for heat dissipation.

The chip is running quite hot it seems

moamps · 10th January 2005, 07:56 PM

any picture?

kmj · 10th January 2005, 08:22 PM

Accually, It just vanished. I connected the amp to my regular system and now there's not a sound, no humming, nothing. It's deadquiet.

To bad the music also is just that

Even if it's a steal for about 200$ depending on chassi and so on there's no "life" in the music so to say.... Good sound but nothing that makes you feel the music.

Perhaps it's because my speakers has a recommendation of 100W to be at their best but anyway...

dw1narso · 11th January 2005, 12:39 AM

May us know what is your speaker, cables and cd player?

Please burn your GC, at least 100hours before you listen critically.

My speaker Dynaudio Audience 40 is not an easy speaker. But my GC drive it nicely...

Regards,
---
David

dw1narso · 11th January 2005, 12:42 AM

Also,

picture please... or please describe more detail about your grounding scheme...

Regards,
---
David

thomas997 · 11th January 2005, 12:58 AM

Quote:

Originally posted by kmj

When i was going to measure the DC-ofset (between the speakerterminals on each shannel, right?) i got a low value on the right one, about 2.0 at the lowest setting. On the left however, i didn't even get a value.... No indication whatsoever. The 3 groundcables is connected at one point in the chassi but not to the outlet in the wall, so to speak. No grounded output in the building.

2.0mV?

Quote:

Originally posted by kmj

The chip is running quite hot it seems

Is the chip the isolated version, or the non-isolated (metal tab on the back)?

Also now that your setup is working, what offset are you getting on the other channel?

jackinnj · 11th January 2005, 01:37 AM

figure you need ~ 700 - 800 sq mm of surface area for the chip's heat sink at that voltage transformer

kmj · 11th January 2005, 08:34 AM

Quote:

May us know what is your speaker, cables and cd player?

My speakers are DIY bookshelfspeakers with Vifa PL18WO09-08, 6.5" and Vifa DX25TG05-04, 1"

Their sensitivity is in the lower 80's.

The source consists of aPioneer DV-656 hooked up to a Xindak DAC3

Cables are also fron Xindak, AC-02 and SC-01

Quote:

Is the chip the isolated version, or the non-isolated (metal tab on the back)?

Its the isolated version and when i started it up I accually burned my finder on the heatsink after only a few minutes. I switced it of and started it up again after an hour or so and now there not hot at all.....the wierdest things keep happening

DC-offset.
Right: 27,8mV
left: 0,16mV

Sorry for the swedish but the signal runs from RCA-in to selector to volume to chip.
Signal ground from RCA-in to volume to chip.

Starground has the 3 wires noted in the instructions.

Anyway, it works fine

peranders · 11th January 2005, 08:36 AM

Linjeväljare = Input selector (in the picture)

Good it turned out good for you.

PS: kmj, you have the same trouble as I have: Insulated, isolated, only one word in swedish for that. The same problem with feeling and emotion which also has only one word in swedish.

PS: Don't forget to have "svettpasta" as I call it (sweat paste), heat compound between the LM3875 and the heatsink. The heat transportation will increase.

If you don't have any you can get a click from me.

dw1narso · 11th January 2005, 09:14 AM

KMJ,

what is your pot value?

do you use the zobel network (2R7ohm + 0.1uF cap)?

I have my amp transform a lot after 150 hours of burning...

My experience with zobel on my amp: do not change any sound but make the amp less hot...

I also just change the pot from 100K log to 10K log... the lower register (bass region) is improved, treble become sweeter, mid become more calm but detailed is improved... (NOTE: my cd player output is 1.2volt RMS, which is quite save to use the 10K pot)

Then, you can also check the High-Capacitance tweak as per-Carlosfm suggestion..., which I do not apply yet currently...

Regards,
---
David

10th January 2005, 12:19 PM	#1
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	Gainclone up and running with some problem Well, it seems that the gainclone indeed is simple to build, however i'm havin som minor problems (ofcourse ) . The amp is Brians basic kit with a transformer 24x24V @300VA (unrectified). When i was going to measure the DC-ofset (between the speakerterminals on each shannel, right?) i got a low value on the right one, about 2.0 at the lowest setting. On the left however, i didn't even get a value.... No indication whatsoever. The 3 groundcables is connected at one point in the chassi but not to the outlet in the wall, so to speak. No grounded output in the building. When i turned it on, with my CD-walkman connected, a rythmic zapping eminated from the left speaker. A hightening in intencity occured when i raised the volume. It is not a hum but more like a Sci-fi Zapping sound, Tzing!. (sorry for the bad explanation). Any ideas how to get rid of it? Best regards! P.S. The chip is connected to an Aluminum heatzink 7x7cm and from 3 to 10mm thick depending if you measure at the point och connection or higher up where there are ridges for heat dissipation. The chip is running quite hot it seems

11th January 2005, 08:36 AM	#9
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Linjeväljare = Input selector (in the picture) Good it turned out good for you. PS: kmj, you have the same trouble as I have: Insulated, isolated, only one word in swedish for that. The same problem with feeling and emotion which also has only one word in swedish. PS: Don't forget to have "svettpasta" as I call it (sweat paste), heat compound between the LM3875 and the heatsink. The heat transportation will increase. If you don't have any you can get a click from me. __________________ /Per-Anders (my first name) or P-A as my friends call me

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10th January 2005, 07:56 PM	#2
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	any picture?

10th January 2005, 08:22 PM	#3
kmj diyAudio Member Join Date: Feb 2004 Location: Falkenberg	Accually, It just vanished. I connected the amp to my regular system and now there's not a sound, no humming, nothing. It's deadquiet. To bad the music also is just that Even if it's a steal for about 200$ depending on chassi and so on there's no "life" in the music so to say.... Good sound but nothing that makes you feel the music. Perhaps it's because my speakers has a recommendation of 100W to be at their best but anyway...

11th January 2005, 12:39 AM	#4
dw1narso diyAudio Member Join Date: Mar 2004 Location: Jakarta	May us know what is your speaker, cables and cd player? Please burn your GC, at least 100hours before you listen critically. My speaker Dynaudio Audience 40 is not an easy speaker. But my GC drive it nicely... Regards, --- David

11th January 2005, 12:42 AM	#5
dw1narso diyAudio Member Join Date: Mar 2004 Location: Jakarta	Also, picture please... or please describe more detail about your grounding scheme... Regards, --- David

11th January 2005, 01:37 AM	#7
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	figure you need ~ 700 - 800 sq mm of surface area for the chip's heat sink at that voltage transformer

11th January 2005, 09:14 AM	#10
dw1narso diyAudio Member Join Date: Mar 2004 Location: Jakarta	KMJ, what is your pot value? do you use the zobel network (2R7ohm + 0.1uF cap)? I have my amp transform a lot after 150 hours of burning... My experience with zobel on my amp: do not change any sound but make the amp less hot... I also just change the pot from 100K log to 10K log... the lower register (bass region) is improved, treble become sweeter, mid become more calm but detailed is improved... (NOTE: my cd player output is 1.2volt RMS, which is quite save to use the 10K pot) Then, you can also check the High-Capacitance tweak as per-Carlosfm suggestion..., which I do not apply yet currently... Regards, --- David

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