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Old 20th March 2011, 01:55 PM   #1
trigger is offline trigger  United States
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Default semi finished 7294 + 6n11

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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.


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project not finished

Last edited by trigger; 20th March 2011 at 02:12 PM.
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Old 22nd March 2011, 06:26 PM   #2
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any ideas or links to info, on how i can eliminate the buzzing
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Old 25th March 2011, 10:20 PM   #3
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loud start up buzz, any idea of what i can do?
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Old 25th March 2011, 11:56 PM   #4
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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.
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Old 26th March 2011, 01:51 AM   #5
trigger is offline trigger  United States
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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!
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Old 26th March 2011, 02:20 AM   #6
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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

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Old 26th March 2011, 02:48 AM   #7
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Quote:
Originally Posted by Meganinja View Post
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.
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Old 26th March 2011, 03:01 AM   #8
trigger is offline trigger  United States
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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?
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Old 26th March 2011, 03:41 AM   #9
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Old 29th March 2011, 02:39 AM   #10
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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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