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Old 10th March 2012, 08:55 AM   #1401
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Quote:
Originally Posted by jazbo8 View Post
Did you play with the order of the pentode/triode sections? e.g., t->p->t->p, or p->t->p->t... Like the LED bias, must be a nice light show when fired up.

Just hit 1,400 posts!!

Jaz
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Old 10th March 2012, 11:41 AM   #1402
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Originally Posted by jazbo8 View Post
Thanks, also what is the switch on the plate of the PI for, sorry if this has already been covered before...

Jaz
The amp is running Class A so I disconnected the top output tube so the amp runs sort of single ended rather than push pull. I was more curious than anything, it cuts the power down by half, I think the amp sounds better in P-P, it gets a little ratty at higher levels but I hear adjusting the screen can help there. I had the hole for the switch already so it was something I had to try.
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Old 10th March 2012, 02:49 PM   #1403
bst is offline bst  United States
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The prodigal returns.

I won't derail the thread with a detailed account of all that's gone on in the last several months. Suffice it to say, I must have signed up for a lot of work on karma in my last lifetime -- multiple deaths in the family, a flooded home, and a spouse diagnosed with a chronic disease. Thankfully, the sh*tstorm has pretty much abated, and things are looking up.

*********

Once again, I'm going to modify the 'rules' and rewards of this challenge. Rather than choosing one design as better than all the others (a flawed premise from the outset), I've tried to identify those who kept this thread going and growing. No, this isn't political correctness, where everyone gets a prize simply for showing up. I scanned many pages, and tried to pick out a dozen people who truly formed the core of this discussion.

Obviously, Tubelab and Tubekit were the source of this (almost always) friendly competition. Printer2 also puts a great amount of thought and time into his well-illustrated posts. TheGimp, Trout, Scitizen17, Djgibson51, Costis_n, Cassiel, ChrisA, Jonnyeye, and Wavebourn all kept the discussion lively and interesting. Kevinkr, with his moderator's hat on, rounds out this baker's dozen of worthies.

If other readers or participants feel I've overlooked someone, please chime in.

************

I too have 'magpie syndrome' -- except that my storage area looks like the last scene of 'Raiders of the Lost Ark'. So instead of paying the BOM tab for one 'winner', I'm going to ship a box of goodies worth at least $100 to each of the people listed above.

I have thousands of NOS tubes. hundreds of pounds of passive components, and many rare goodies to make A DIY tinkerer salivate. If you will tell me your preferences as to category of components, I'll try to oblige. Want sleeves of tubes? How about boxes of new aluminum knobs? Envelopes full of resistors, or bags full of polypropylene caps? Tubelab, I know you like high voltage. How about a huge potted UTC transformer, and matching choke, rectifiers, and HV sockets to construct a 1600v, 2200mA power supply?

Gentlemen, let me know your preferences, and a shipping address, in a PM. For those folks overseas, please be realistic -- I'll be glad to send you tubes or other lightweight components, but a box full of transformers isn't likely to come your way.

****************

I hope this twist is acceptable to all, and thanks for keeping things going while I dealt with much unpleasantness.
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Old 10th March 2012, 05:19 PM   #1404
Cassiel is offline Cassiel  Libya
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Well, welcome back. Hopefully there would be no more sorrowful times for you, now that karma has done its nasty stuff .


Quote:
If other readers or participants feel I've overlooked someone
Well, apart from me being at the bottom of the barrel sharing places with Costis and Johnnyeye *cough cough* I think Wavebourn left the game too early, I'd swap him with.......(can't remember his name), the one who builds guitars and posted a few recordings. Australian I think. Probably my 'peculiar' sense of humor put him off so I'm feeling a bit guilty. Never seen again.
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Old 10th March 2012, 08:09 PM   #1405
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Sorry to hear life has been throwing you a bunch of fast balls. Good to hear you are back. The challenge was fun in that it got us thinking and working on our projects. As far as I have looked at things the prize was to look at your design and see something to be proud of, that you might inspire someone else to pick up side cutters and iron to build or build upon your design, or at least learn from your mistakes.

While the concept of picking a winner and offering a prize seemed simple enough from the beginning, I would say now the practicality of it may not have been. So now we have a gracious offer of treats for all the good kids for participating in the fun. Well it just kind of knocks me over. You are being much too gracious.
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Old 11th March 2012, 12:28 AM   #1406
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Quote:
Originally Posted by Printer2 View Post
The amp is running Class A so I disconnected the top output tube so the amp runs sort of single ended rather than push pull. I was more curious than anything, it cuts the power down by half, I think the amp sounds better in P-P, it gets a little ratty at higher levels but I hear adjusting the screen can help there. I had the hole for the switch already so it was something I had to try.
Wouldn't running the PP OT in SE cause it to saturate, may be at low power level, it isn't too bad?

Jaz

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Originally Posted by bst View Post
The prodigal returns.

****************

I hope this twist is acceptable to all, and thanks for keeping things going while I dealt with much unpleasantness.
Sorry to hear about the ordeal you had endure of late, glad to see your return, you should really be the one to get rewarded for creating one of the most successful threads in this forum, I have learned so much just by reading and trying out the various designs that appeared in the thread, thanks again!

Jaz
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Old 11th March 2012, 01:55 AM   #1407
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glad to see ya back BST and i'dd like to thank ya all, ive learnt a lot reading these pages, whats this years compition ?
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Old 11th March 2012, 03:00 AM   #1408
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Quote:
Sorry to hear about the ordeal you had to endure of late, glad to see your return, you should really be the one to get rewarded for creating one of the most successful threads in this forum, I have learned so much just by reading and trying out the various designs that appeared in the thread, thanks again!
I was looking for the right words when Jaz's post appeared, and I can't say them better.
Awesome thread - thanks bst.
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Old 11th March 2012, 03:18 AM   #1409
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Quote:
Did you play with the order of the pentode/triode sections? e.g., t->p->t->p,
I did try this arrangement.
RCA Receiving Tube Manual RC30 (resides on my iPad thanks to Pete Millett) gives a figure for input resistance at 50MHz.
So I have a lot of 100pF caps in the current circuit.
Using triode strapped pentode in the second stage I couldn't stop the oscillation without rolling everthing off above 1KHz - not a good sound. I don't have enough shed time to hunt down the possible layout cause of this so reverted to the posted schematic. A value of A=16 in the 1st stage was just too hairy, A=8 was just too polite, A=12 gave a sustained rude ballsy rock sound that had me grinning for days.
Cheers
JimG
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Old 11th March 2012, 03:31 AM   #1410
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Quote:
Like the LED bias, must be a nice light show when fired up.
See picture on Post 1321.
The 4 LEDs are 3ml items behind 2ml holes in the top of the chassis in a line between the two tubes.
Half my 6BL8's are used items and this way I can see at a glance if each tube section is at least passing current after everything has been buttoned up. LED in middle of front panel tells me heater circuit is also delivering.
Cheers
JimG
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