seriously thinking about building this schematic. Can you find any issues with it? - Page 2 - diyAudio
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Old 1st November 2013, 06:52 AM   #11
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No worries, many of us have tried to tell him the same thing, but the messages did not get through... he would just have to find out things his own way, nothing wrong with that, everyone has a different way of learning things.
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Old 1st November 2013, 02:52 PM   #12
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OP = opening poster = Sea Biscuit
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Old 4th November 2013, 10:46 PM   #13
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Quote:
Originally Posted by jazbo8 View Post
An on-going saga... Just build the darn thing and see if it works already... if not, figure out why.

That thread you linked to was a completely different idea/effort [which has since been scrapped] than this one.

Quote:
Originally Posted by jazbo8 View Post
The OP is not interested in copying working circuits, that would too easy, so trial and error it is...
This schematic that I posted in THIS thread is pretty much a straight copy of an old Supro amp, so your hopes and dreams of me copying working circuits has come true!


Look, I may ask some questions that are either tedious, boring, short sighted or just plain don't make sense to some of you. That's because I am very much a novice builder. There are many parts of these circuits that I just don't fully understand... YET. I'm working my way through it, and in time I promise to make my questions more interesting for some of you more seasoned hobbyists/techs. But in the meantime, try being either constructive or absent

And thanks to you guys that have offered some help. I will change the rectifier and look at the other concerns.

Here's a link to the schematic I copied. What drew me to it was that it is the most simple dual output tube schematic I've seen, plus I like the sound of old Supro's. And furthermore, I have a pair of transformers from an old 60's Bandmaster and a nice pair of old GE 6L6's to go into it. That makes this project very affordable for me because all I need is some general inexpensive parts to implement it.

http://usdn3.nodevice.com/preview/big/373/373418-2.jpg
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Old 4th November 2013, 11:00 PM   #14
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Question about the center tapped HT and rectifier.... Would it make any difference whether I changed the rectifier to work with the CT'ed winding, or instead - simply lift the center tap and leave the rectifier as drawn in the schematic?
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Old 4th November 2013, 11:14 PM   #15
Enzo is offline Enzo  United States
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You can use a full four-diode bridge and leave the center tap not connected, or you can use two diodes and ground the center tap. In the first place you will be rectifying the entire winding voltage into DC. If you ground the center tap, you are then rectifying half the voltage of the winding, so the result will be much different.
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Old 4th November 2013, 11:20 PM   #16
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Here's a pdf of the same schematic I copied with some additional information. There's a note about the cathode resistor value on there too. http://www.angelfire.com/mech/beansa...hems/S6420.pdf

The only things I changed were the PT CT, I moved the bulb to be fed by 6.3vac instead of mains voltage, I added 1 ohm sense resistors on the cathodes of the output tubes, and I also plan on adding a standby.
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Old 5th November 2013, 06:37 AM   #17
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I stand corrected, good luck with your Supro build.
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Old 5th November 2013, 10:43 PM   #18
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ok here's an updated drawing.


As for the power tube screen resistors, can anyone help me understand what their function is?


Plus, I'm looking at C2 & C3. Any reason not to just use a single 30uF or just drop the 10uF?


Click the image to open in full size.
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Old 5th November 2013, 11:33 PM   #19
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If you still want to only use 3 triodes, just use a 12av6 as the first tube, and maybe you can use the signal diodes as clipping diodes such as in a distortion pedal. Otherwise, using the remaining 12ax7 half as an additional gain stage would make it much more usable for passive guitars or even bass.
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Old 10th November 2013, 01:20 AM   #20
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Stick a direct coupled follower in there and...
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