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A WE-91B project
A WE-91B project
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Old 15th April 2018, 12:48 PM   #111
jerrylong is offline jerrylong  China
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Thanks for noticing this project, could you give some advice to this project?
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Old 15th April 2018, 03:45 PM   #112
hooman is offline hooman  Iran
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1-hi sensitivity speaker =hear very small signal from amp !!!it is very bad chans in tube amp .
2-dht out put =noise in output . dc filament with good filtering and 100 ohm balance pot .some times i use battery for filament to understand source of hum .if change ...should try on filtering of dc for filament .
3-disconnect the signal of tube driver to 300b and see the oscop .if have hum try to fix it .
4- reduce hum in out put dht tube is not difficult .but most of problem happen in gain stage and first tube .this kind of hum need spend time to detect source of hum .
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Old 15th April 2018, 04:33 PM   #113
hooman is offline hooman  Iran
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rr2.jpg

to day i working on guitar amp hum .45 mv hum is problem on guitar speaker .
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File Type: jpg rr1.jpg (221.3 KB, 130 views)
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Old 16th April 2018, 04:01 AM   #114
jerrylong is offline jerrylong  China
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Quote:
Originally Posted by hooman View Post
1-hi sensitivity speaker =hear very small signal from amp !!!it is very bad chans in tube amp .
2-dht out put =noise in output . dc filament with good filtering and 100 ohm balance pot .some times i use battery for filament to understand source of hum .if change ...should try on filtering of dc for filament .
3-disconnect the signal of tube driver to 300b and see the oscop .if have hum try to fix it .
4- reduce hum in out put dht tube is not difficult .but most of problem happen in gain stage and first tube .this kind of hum need spend time to detect source of hum .
Thank you hooman, very good advice. This experience will help me a lot
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Old 16th April 2018, 04:02 AM   #115
jerrylong is offline jerrylong  China
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Quote:
Originally Posted by hooman View Post
Attachment 675348
to day i working on guitar amp hum .45 mv hum is problem on guitar speaker .
Use battery to the heater, quite a good testing method, how to connected it to 300B filament?
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Old 16th April 2018, 02:32 PM   #116
hooman is offline hooman  Iran
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hi
se1.jpg
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Old 16th April 2018, 05:33 PM   #117
jerrylong is offline jerrylong  China
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Thanks a lot, you are quite a artist of drawing◝A WE-91B project
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Old 16th April 2018, 07:07 PM   #118
hooman is offline hooman  Iran
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RE1.jpg
RE2.jpg
RE3.jpg
2 YEARS before i send circuit and parts to my customer for 300 b amp project .pleas look at the power supply and amp .first i design circuit whit c3m...vt25...300b...
2 dht !!
before to assemble and make box by customer ...i test all of circuit and check sound with hi sensitivity speaker .
hum=0
musical sound
no pcb .
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Old 17th April 2018, 12:26 AM   #119
jerrylong is offline jerrylong  China
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Begin to rebuild the second one of this mono.
Two changes:
1, used shield twisted cable for heater
IMG_1258.JPG
2, change connection point of two 310A, from 1st stage to 2nd stage
IMG_1259.JPG
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Old 18th April 2018, 05:13 PM   #120
jerrylong is offline jerrylong  China
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Reduced the noise to 6mV(input VR to min and max)
IMG_1282.JPG

IMG_1281.JPG

When input VR at the middle nosie rised to 19mV, connected the shell of VR to chassis, noise reduced to 8mV
IMG_1283.JPG
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