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-   -   semi finished 7294 + 6n11 (http://www.diyaudio.com/forums/solid-state/185436-semi-finished-7294-6n11.html)

trigger 20th March 2011 01:55 PM

semi finished 7294 + 6n11
 
http://farm6.static.flickr.com/5258/...0f5b65aa0a.jpg


well after like 500 welds she is semi finished. i had to hook it up and listen, i am quite impressed by the sound of the amp. i took on the project with very limited budget $100, i didnt expect much with low end components but the amp is very clean and accurate, no distortion at top vol, . my speaker project was 50$ budget, 70's CTS 15's +jensen horns, (speaker stands and super tweeters are still on the shop table to be made) most supplys are used or were found scrap.


well one issue, the amp has a start up buzz that goes away after a min, and when the vol pot is in the half way spot, there was a buzz, that i silenced with, brass pegs on the buffer, but now there is a slight scratchy sound at the mid point of the vol pot, i am sure its not dirty, like a feedback buzz...?

the other issue, with earth ground connected, buzzz, or when i touch chassis, buzzzzzzzzz. little buzzez but buzzez, any ideas or recommendations???? snubber caps?, more brass? isolate power supply?eahhh?

otherwise the amp is dead silent even at top volume.


http://farm6.static.flickr.com/5131/...08acd61d4d.jpg
project not finished

trigger 22nd March 2011 06:26 PM

any ideas or links to info, on how i can eliminate the buzzing

trigger 25th March 2011 10:20 PM

loud start up buzz, any idea of what i can do?

CBS240 25th March 2011 11:56 PM

Do you have an input filter installed after the pot? How is the grounding scheme concerning ground loops? The buzzing when earth gnd is connected stinks of a ground loop.

trigger 26th March 2011 01:51 AM

no input filter in the circuit (i think)
something like a RC filter? i was hoping the 6n11 buffer would eliminate any need for attenuation, its buzzin.
so i measure dc offset and then i ...? iam lost, after several hours of reading, i cant find a formula or further direction.?

i appreciate the help!

Meganinja 26th March 2011 02:20 AM

Hi
I think it is the valve that make hum buzz during start up, because valve should have HV delay sometime , as it warmed up the buzz disappear , get a anti thump delay a min or two kit on ebay should fix the problem

Regards

trigger 26th March 2011 02:48 AM

Quote:

Originally Posted by Meganinja (Post 2516694)
get a anti thump delay a min or two kit on ebay should fix the problem

Regards

thank you much for your response, are you talking about installing audio delay effect ic? or is there something more prefab? or am i lost as usual...?
again thanks for the response.

trigger 26th March 2011 03:01 AM

wait, would a simple solution to eliminate to start up buzz be just to just install simple switch after the buffer before my amp? is there a good line signal switch on the market, or will a standard switch work?

trigger 26th March 2011 03:41 AM

http://farm6.static.flickr.com/5141/...749b4a64f2.jpghttp://farm6.static.flickr.com/5264/...e39eba8690.jpg
http://farm6.static.flickr.com/5182/...ee72743da6.jpgHttp://farm6.static.flickr.com/5097/...4a6b290326.jpg

trigger 29th March 2011 02:39 AM

if i were to remove the 12vac PT from this equation, and replace it with a step down PT what issues would i be looking at feeding a step down pt off the torodial?
any advice is appreciated as i dont really know what iam doing, just doing it safely...


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