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Old 3rd February 2013, 10:10 PM   #1
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Default long tailed power amp class a

so got me self some ruskies on the cheap from e-bay, 6p18p, 6p6s, 6n2p 6n1p. done my first project pretty much. so i'm thinking about number 2.

i noticed a lot of people asking if they can use pp txs as se? well i was wondering how aout the other way round? i have a 5k (C.T.) 5w output tx i was thinking if i hook an 8 ohmer to the 4 ohm tap i'd essentially have 10k a-a?

thinking b+ around 250v allowing 100v for the tail and 150 for the plate. any recommendations? advice? critiques? all welcome

one last note. i do realise if i go through with this i could lose some iron/tubes however i would like to see if i can get it to work so i willing to deal with the loss
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Old 4th February 2013, 01:49 AM   #2
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Have no idea what you are asking.

P-P or SE?

Output transformer for a P-P pair (I am guessing) running at 250V.

100 for a tail? What tail?

No idea what you are doing.
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Old 4th February 2013, 02:03 AM   #3
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self inverting power amp to lower power output and increase input sensitivity. also cos i've only seen it in 1 other place. in p-p config using a se centre tapped tx to see what happens. i read that se is more demanding on the core so i tht i'd try pp on it seeing as the taps are 50% i hope that's a bit clearer

also i hope to run it in class a as the other place i saw it did the same and said it had good results Push-Pull Without a Phase Inverter
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Old 4th February 2013, 03:49 AM   #4
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Quote:
Originally Posted by akadazzle View Post
self inverting power amp to lower power output and increase input sensitivity. also cos i've only seen it in 1 other place. in p-p config using a se centre tapped tx to see what happens. i read that se is more demanding on the core so i tht i'd try pp on it seeing as the taps are 50% i hope that's a bit clearer
Sorry, still makes little sense.

Quote:
also i hope to run it in class a as the other place i saw it did the same and said it had good results Push-Pull Without a Phase Inverter
Well now I have a frame of reference. You are mistaken, it is not a SE OT that is a P-P transformer being used. You have no other choice to run that circuit as Class A, it is a self split arrangement but the addition of the 'tail' helps in the balance between the output tubes. I would just do a simple self split with what you have.
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Old 4th February 2013, 04:58 AM   #5
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i appreciate my lack of knowledge on the terminology can be confusing so apologies

but i do realise a SE TX isn't used, the reason i'm doing it is to see what happens. my SE TX has a 50% centre tap on it (and looks awfully similar to the 1 on a lc15). a lot of people on the internet ask if u can use p-p tx's as SE. the most common answer i found was no because SE is too demanding on the cores, i figure that must mean p-p is less demanding. so i want to wire my SE as 5k tap to anode 1 centre tap to ht and 0 ohm tap to anode 2 with a 8 ohm load on the 4 ohm load tap to give me 10k anode to anode. i plan on using it in this wiring config with a circuit based on the 1 on the link. what can i say? 70% curiosity 30% cheap A** brit
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Old 4th February 2013, 05:34 PM   #6
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SE and PP transformers are very different in construction. SE has a core gap to deal with the DC magnetism. I don't know enough about it to comment on whether this would be okay in a PP design, but you definitely can't (shouldn't) use a PP OPT in a SE amp.

This output circuit is very interesting to me. I've been contemplating a SE design for a while now, the goal of which is to have an amp that can produce great overdrive tones at a medium volume level. I'm now thinking this inefficient PP design would be fun to try.
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Old 4th February 2013, 05:45 PM   #7
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Self inverting power stage has so many defects that I can not see any practical reason to build such. But if one wants to experiment, that's some reason.
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Old 4th February 2013, 07:54 PM   #8
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Quote:
Originally Posted by doozerdave View Post
This output circuit is very interesting to me. I've been contemplating a SE design for a while now, the goal of which is to have an amp that can produce great overdrive tones at a medium volume level. I'm now thinking this inefficient PP design would be fun to try.
same sorta goals i had to be honest, what sort of output power should i be aiming for? i was thinking maybe around 6-8w would be a safe max as these are rated for 7w peak in se or do you think i could push a little more? as i mentioned these cores look uncannily like the one from an lc15 so maybe i might get lucky with 10w?

i'll do a bit more messing on my se first tho as i really do want to hear triode mode first. i asked in another thread but no one answered, is it safe to just throw a sub mini toggle in as triode switch? or do i need higher quality? (only rated for ac250 2a no dc spec) b+ in question is 250. for 6p18p

thanks in advance =)

Last edited by akadazzle; 4th February 2013 at 08:15 PM. Reason: forgot to mention the valves i using....
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Old 5th February 2013, 02:21 AM   #9
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You should be able to run your SE transformer as a P-P transformer by using the 50% tap as a center tap on a P-P amp.
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Old 5th February 2013, 12:39 PM   #10
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Quote:
Originally Posted by akadazzle View Post
i'll do a bit more messing on my se first tho as i really do want to hear triode mode first. i asked in another thread but no one answered, is it safe to just throw a sub mini toggle in as triode switch? or do i need higher quality? (only rated for ac250 2a no dc spec) b+ in question is 250. for 6p18p

thanks in advance =)
That switch should be fine. 250VAC will have peaks of 350V so the switch definitely has a higher isolation voltage than 250V.
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