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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Fri Mar 25, 2011 9:08 pm 
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Шаман, типа...

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Location: Pleasant Hill, California
Because anyway that 60W P-P transformers had 4,8,16 Ohm taps. Now it is 2,4,8 Ohm taps for 5W per channel amplifier. Very Happy
Or, for 4,8,16 Ohm on smaller speakers, with lower distortions on 2.5W per channel.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 6:53 am 
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Breadboarded an el83-4p1l circuit...sounds real good...making the amp this weekend...

but tendency to oscillate...then red plates and burnt cathode resistor if oscillate... should i place grid stopper on g2 and g3?


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:06 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
quikie22 wrote:
Breadboarded an el83-4p1l circuit...sounds real good...making the amp this weekend...

but tendency to oscillate...then red plates and burnt cathode resistor if oscillate... should i place grid stopper on g2 and g3?


Can you show your schematic and photo of your layout first?

Mine is quiet without that resistors. Grid stopper only (62 Ohm)

'

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:23 am 
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driver = 6p15p pentode with 10k Rload and 330 ohm cathode R, running at around 20mA

coupling via russian PIO 0.22uF 450V to

4P1L - plate+G2+G3 all tied together, grid stopper to g1=39ohm, Rcathode 510 ohm, OPT=5K, grid leak 470kohm


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:30 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
Are you sure it oscillates?
May be it runs away? Try to decrease that 470K grid leak and see what happens. For example, put some 47K and see. If it is oscillation it won't help. If it is run-away, it would definitely help.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:33 am 
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""Try to decrease that 470K grid stopper and see what happens. For example, put some 47K and see. ""

grid leak or stopper? It is possible runaway too because I dun hear any funny noises.


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:34 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
""Try to decrease that 470K grid stopper and see what happens. For example, put some 47K and see. ""

grid leak or stopper? It is possible runaway too because I dun hear any funny noises.


Sorry for the typo; I corrected.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 7:43 am 
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no problem Smile

Will try with smaller R in grid leak....another trip to the shops for me.... gotta replace the smoked 510 ohm cathode R with higher rating ones as well...

el83+4P1L= very impresssive.... but power is limited... may consider parallel tubes, like yours.


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 8:03 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
6P15P by the way in triode is very close to 4P1L, so you may consider to use either both 4P1L, or both 6P15P in driver and output. Wink

If you use still the same 5K transformer I doubt you can get more power.
Also, you don't use all power possibilities of 4P1L, with coupling capacitor between driver and output stage. It should be used either with interstage transformer, or with cathode follower like I did.

Or, you may prefer your arrangement, but with 6P15P output, and 300V on anode, 220 Ohm in cathode (shunted by cap).


Attachments:
6P15P_triode.JPG
6P15P_triode.JPG [ 117.62 KB | Viewed 5285 times ]

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 8:22 am 
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Yes with the GU-50 amp, the CF allowed a higher power output. So, yes I was considering a cathode follower, but my PT does not have extra secondaries for the -ve bias voltage of CF. Any suggestions for single supply voltage CF? I have 6N1Ps, 6N6Ps, 6P15Ps/EL83 and 4P1L and a couple of 6P1P as well.

I can also custom order an IT, but is an expensive option. Is a 1:1 winding ratio ok?

My OPT has taps at 2.5K, 3.5K and 5K. Other OPT has taps at 2K,4K and 8K.

6P15P is in pentode Smile, have not tried triode yet.


Last edited by quikie22 on Thu Apr 07, 2011 8:47 am, edited 1 time in total

 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 8:46 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
If it is a breadboard, you may try a separate transformer for a negative PS.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 8:48 am 
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would a 1:1 IT be ok?


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 9:01 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
would a 1:1 IT be ok?


Sure.

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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 9:15 am 
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borrowed my friend's custom wound IT, I think the IT is not good, although power is higher, high freq is attenuated...


 
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 Post subject: Re: Gubernator-7: 4P1L Single Ended Amplifier Design
PostPosted: Thu Apr 07, 2011 9:43 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
borrowed my friend's custom wound IT, I think the IT is not good, although power is higher, high freq is attenuated...


It is the problem of any IT... It should be very expensive if you want it to be wideband. That's why I ended up with cathode follower and active dynamic loads and found it much better.

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