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Old 23rd September 2010, 06:58 AM   #21
adamus is offline adamus  United Kingdom
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why not use a ccs anode load, say dn2450 cascode, or something like the morgan jones cascode, then try LED or stick with a resistor in cathode?
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Old 23rd September 2010, 02:43 PM   #22
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Quote:
Originally Posted by adamus View Post
why not use a ccs anode load, say dn2450 cascode, or something like the morgan jones cascode, then try LED or stick with a resistor in cathode?
Yes! I see it! But CCs anode load, it is very hot! And the sound is not like!

Use led in the cathode, i like the sound!
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Old 23rd September 2010, 04:40 PM   #23
kevinkr is offline kevinkr  United States
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Hi kevinkr!

Well thank you!
Well yes, the LM317 can not be the best, I used Jfet replace it! I recently tested the following schematic, and I enjoyed it! 6h30pi particular tube,
Thank you and hope you add comments to this pre!

With tube 6h30 i like:
Anode = 90V, 40mA/ Tube
6h6 I like:
Anode = 170V, 40ma/Tube
This is other circuit, Please see it!
Thanks
Quanghao
Simple balanced pre-amp. I did something similar long ago and also experimented with cross-connected cascodes, excellent balance, but too much noise with the Amperex E82CC I was using at the time. Consider using a cascode CCS with a small negative supply (-12V or so), CMRR will be greatly improved. (Ability to reject hum, and other common mode noise)
I'd think you might want to increase the plate load resistor values slightly? _ I haven't checked rp for this type, but bear in mind that with differential connection it will be much higher than you think. (twice or more is possible)
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Old 10th October 2010, 08:31 AM   #24
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Quote:
Originally Posted by kevinkr View Post
Simple balanced pre-amp. I did something similar long ago and also experimented with cross-connected cascodes, excellent balance, but too much noise with the Amperex E82CC I was using at the time. Consider using a cascode CCS with a small negative supply (-12V or so), CMRR will be greatly improved. (Ability to reject hum, and other common mode noise)
I'd think you might want to increase the plate load resistor values slightly? _ I haven't checked rp for this type, but bear in mind that with differential connection it will be much higher than you think. (twice or more is possible)
yes! it is very nice idea . the circuit follow the basic with CCS + bias!
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Old 23rd October 2010, 01:11 PM   #25
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This is layout for Pre 818! please see it!
Thanks
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Old 23rd October 2010, 01:20 PM   #26
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Quote:
Originally Posted by adamus View Post
why not use a ccs anode load, say dn2450 cascode, or something like the morgan jones cascode, then try LED or stick with a resistor in cathode?
Hi admus!
Led biass, the sound is very detail, Like!
Thanks
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Old 23rd October 2010, 02:35 PM   #27
adamus is offline adamus  United Kingdom
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no problem. LED + Css anode load has given me good results in similar designs.
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Old 9th November 2010, 08:35 AM   #28
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Quote:
Originally Posted by adamus View Post
no problem. LED + Css anode load has given me good results in similar designs.
Hi adamus ! im not like the sound use CCS!

Hi all!
you can down the circuit and measure about the pre in this linhk:
http://www.quanghao.com/product.php?id_product=72
thanks
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Old 10th November 2010, 11:47 AM   #29
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Default This is cricuit for Pre818

Tranfosmer for PRE818
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File Type: jpg Tranfosmer-for-PRE818.jpg (83.2 KB, 515 views)
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Last edited by quanghao; 10th November 2010 at 12:07 PM.
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Old 10th November 2010, 11:56 AM   #30
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Default This is cricuit for Pre818

This is cricuit for Pre818
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File Type: jpg PRE-818-cricuit-design-by-Q.jpg (223.0 KB, 530 views)
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