|Author:||automap68 (registered user: 127 posts )|
|Date:||Fri, Feb 10th, 2012 @ 16:18 ( . )|
On 02/10/2012 @ 15:55, Warren wrote :
Try not to get too upset. I'm new here, and just built basicly the same amp as you in December. It started as a P1eX but I changed it to an SEL but with an EL34.
: I too have lots of lots of fancy gear. This is my first low power/low frequency project. I repair and maintain tube amps in the 10's of kilowatts range in the upper UHF range. The tubes run with with voltages in excess of 35kV, and some are 4' tall.
: Anyway, while I am new to this forum I am on others for other hobbies and people get offended too easy when long time members try to help. No one knows who you are, or what your experience is. So an asumption is made that you don't know what you are doing, and you made a mistake. And this often turns into people thinking they are insulting each other when they are probably not.
: So, it is alwasy best to give way more information than you think you need, and answer questions as completely as possible without offense.
: With all that said, your problem is that you aren't getting the gain/power output you expect? Can you use your scope to measure the in and out signal level of each stage? First the level at the input jack, then at the gain 1 pot, then the gain 2 pot. Use a 10x probe, and be careful of the voltages.
: Record what the voltage gain of each stage is, and if the clipping is symetrical or asymetrical.
: I can't help you with what this values should be as mine will be differnt with an EL34 and my preamp stages 1 and 2 are biased like a P1eX. But that should give you more information to post to determine what is going on. If you find a stage has little or no gain, or clips very early, that will where to focus your attention.
Thanks for the idea
I have looked at each stage but will have to do it again and record the level
I did this 1 day visually just to see the difference in magnitude
Which looked fairly normal no real apparent lack gain through each stage but I will do it again as soon as I get out Tonight
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