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Old 7th March 2013, 08:46 PM   #81
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0.06A
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Old 7th March 2013, 09:00 PM   #82
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Quote:
Originally Posted by sagi4422 View Post
0.06A
Correct, Ik=62ma.

What's your estimated output power? (see the table at the bottom of this page):

Tubes & Transformers

Load Z is your output transformer primary impedance.

Last edited by boywonder; 7th March 2013 at 09:03 PM.
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Old 8th March 2013, 06:24 AM   #83
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I need to measure the B+ for this table ?!
I measured the voltage across C1 and C2. C1 - 453V and C2 - 437V
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Old 8th March 2013, 09:41 AM   #84
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DIY tube amp Simple SE - YouTube
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Old 8th March 2013, 01:16 PM   #85
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Nice! It sings! The RCA jacks and speaker jacks in cardboard boxes are a nice touch.

Looks like you've got a motor run cap as well.

Now you need a chassis. You can use a baking pan upside down for a quick and dirty chassis, you just need a unibit to drill the tube holes.

The voltage across C2 is your B+ voltage. If you jumper or install a switch across SW1-SW1 you be using SS rectification and your B+ will increase a little.

What is the primary impedance of your output transformers?

Last edited by boywonder; 8th March 2013 at 01:19 PM.
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Old 8th March 2013, 02:23 PM   #86
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5000 ohms
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Old 8th March 2013, 04:42 PM   #87
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I am working on an aluminum chassis now . Thinking of adding some wood for the faces of the chassis . Dont know yet ....
Anyway, I added the run cap and it removed most of the hum I had before .
I have a problem with my POT , anyone can
Offer such POT from mouser/farnell?
In case I would like to increase the maximum volume I have now (max output power), the right approach is by changing tubes?
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Old 8th March 2013, 04:59 PM   #88
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Quote:
Originally Posted by sagi4422 View Post
I have a problem with my POT , anyone can
Offer such POT from mouser/farnell?
In case I would like to increase the maximum volume I have now (max output power), the right approach is by changing tubes?
What's the problem with the pot? A cost effective upgrade alternative is a stepped attenuator off of ebay from China.

You can increase the power out by increasing the B+ and bias current (by reducing the value of R17 & R27) as long as you do not exceed the max power dissipation specs of whatever tubes that you are using. Tubelab's tables are your friend here.

One note on the tables; IIRC, the tables are for triode wired outputs. If you are using UL, your output will be higher.

In Tubelab's tables, notice the values in red, these are busting out of the published max power spec of the output tubes. You can usually exceed the max dissipation values a little without much trouble, although that depends on the tubes. Also, the harder you crank the B+ and bias current, the shorter the tube life will be. On average you can expect 2000-3000 hours out of your tubes (big generalization here...).

Again, looking at the tables, the max power out will be with KT88's. They can handle higher B+ and bias current without busting the max power dissipation spec.

You can easily raise your B+ just by jumpering SW1-SW1, that will give you SS rectification (the rectifier tube will just sit there and do nothing or you can remove it). It will probably go up about 30V or so, since the diodes drop about 1.4V and the rectifier drops about 30 volts or so. SS rectification gives you a lower PS output impedance, a good thing (your motor run cap lowers the output impedance as well).

The easy way to get more output is to use high sensivity speakers, like 93-95db 1W/1M. These amps really shine with high sensitivity full range speakers. Small two way bookshelf speaks are generally fairly inefficient, like 86-87db.
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Old 8th March 2013, 07:55 PM   #89
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I think the POT is basically ok, the problem is that I think I ruined him when soldering so the plates in the POT are dancing. I have ALPS POT from china and it is more soutable for board soldering and less for wiring soldering
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Old 11th March 2013, 08:27 PM   #90
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Any recommendation for mods to this build ?
I am preparing the chassis and I am willing to include/replace the mods before installing the parts
Thanks
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