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Old 12th November 2011, 04:07 PM   #21
SY is offline SY  United States
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Thanks for digging that up! I wrote it, but no longer had a copy.
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Old 12th November 2011, 05:46 PM   #22
tricomp is offline tricomp  Denmark
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Ha, small world SY

If you'd like to have the original version in full resolution PM me with your e-mail address.
I had to doctor the file to make it fit the forum.
Thanks for writing it.

rgds,

/tri-comp

Last edited by tricomp; 12th November 2011 at 05:50 PM.
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Old 13th November 2011, 02:48 AM   #23
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I will read this on my travels. I'm leaving for Guangzhou in a couple hours. Gives me something to do. If I have time I will visit the parts store in Guangzhou.

SY I read in other forums that you said on the Jolida to first do the CCS on the tail and then address the lifting of the heaters and possibly the SSRP input. I am really happy with the improvements on the CCS. Next up is the heaters. I found a transformer here are the spec (3.15-2.5-0-2.5-3.15)X2(3A)、0-12.6 (1A),0-5(2A)

I just need to make sure I have room. If not I know I can lift the existing heaters but you recommended a separate transformer if possible. As you can tell I respect your knowledge. I'm really happy with the success so far and would like to see how far I can take this amp. I bought it direct from the factory for just over $500 shipped. It's a nice learning platform.
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Old 13th November 2011, 02:02 PM   #24
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Another useless idea...
Shunt Regulated Tail
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File Type: gif Shunt Tail CCS.gif (24.2 KB, 272 views)
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Old 15th November 2011, 11:12 AM   #25
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Default I think the output impedance is?

Ok tricomp I spent some of my free time looking at the formula and coming to understand it. When I first looked at it I could have been trying to read Chinese. But Now I think

Re * hfe (upper) *hfe(lower) + the 1/hoe is between 390k min to 2 meg.

Re = 20
BC549 hfe 400
MJE340 30 min to 240 max not sure how to pin that one down but that was the data on the sheet.

What does the hfe1 and hfe2 mean. I do understand the dc or ac gain but does the 1 and 2 represent?

Sorry I feel like a tortoise trying to swim with the turtles here.

I could not find the BD 139 hoe. SY I looked at the curves but I didn't understand them. But I do understand that if you use high hfe transistors it's not really important because your output-impedance is very high anyway.

I was able to source all the parts except the TL783. I will need to order that. I will experiment with the B- and the other transistors when I get it.But I will replace the BD139 with MJE340 tomorrow and replace the 1/2w trimmer with a 2 watt resistor. I think for safety reasons I must.
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Old 15th November 2011, 11:35 AM   #26
SY is offline SY  United States
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Re is the resistor value you use in the emitter lead to set the current- I think it will be bigger than 20R! hoe can be gotten from the curves- at the point where they flatten out, they'll be more or less parallel and have a tilt. The slope of that tilt is 1/hoe. The hfes are definitely going to be on the datasheets- if you use very old transistors, the datasheet might give beta instead, which is close enough for government work.
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Old 15th November 2011, 01:04 PM   #27
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Ops I was trying verify if that was the resistance at the emitter but I only found this reference in MJ's book , He was talking about the resistance looking into the emitter and said that it was usually 20 ohm.

So I learned something. "silly me". I think the diyaudio forum is about learning and it just goes to show I have much to learn.

Unless I made another mathematical error my output impedance is between just over 2 meg and 16 meg. That's seems very good.



hfe lower BC549 =400
hfe upper MJE340 30-240
hoe for MJE340 = 150K
Re = 172 ohm
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Old 15th November 2011, 01:21 PM   #28
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Bingo!
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Old 27th November 2011, 06:46 AM   #29
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Default Thanks for the help

I changed the BD139 to MJE340 and tried a few resistors for Re but went back to the 200R variable. I played around and was able to get the drop on the L side to 165 on the plate resistors and 162.5 on the plate to grid difference and 171 and 167 on the right side.

I lifted my heater by 65 volts and things are sounding really nice. In fact a couple of day's ago I was typing on the computer and I walked in the living room and my wife was sitting in the sweet spot and paused the CD when she seen me. Her comment was, did you buy new tubes again? I thought about it and said no. She said it sounds like it. It sounds really nice. That is high praise coming from my wife.

I still want to try the neg supply and increase the output impedance even more, but for now it's sounds good. Thanks for the help!
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Old 27th November 2011, 09:35 AM   #30
SY is offline SY  United States
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It's always simple in retrospect.
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