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Old 13th September 2004, 08:49 PM   #1
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Default 30W UL 6L6P-P amp

I was searching in forums at DiyAudio to take ideas and schems to build my new amp .
So ,with Geekís and coqsncoqsí very useful help I tried to design my own schem.
The driver stage , 6SN7 direct coupled to 6FQ7 LTP , is taken by coqsncoqs (a driver stage that he is working with arnoldc for an amp with EL34).
It has around 39.5 db gain . So with 0.5 Vrms input Iíll have 47 V at each output of the phase splitter , right???

Here I have a newbie question. The above means : 47*2=94 V rms from grid to grid ????
According to , Svetlanaís data the SV6L6 PP output stage needs peak 70 V grid to grid voltage or 49.5 V rms . So with an input about 0,25Vrms and without FB I can drive the output stage at full power and have 30W .
Please be patient and if Iím wrong please correct me .

The output stage is designed by me trying to obtain a 6L6 PP UL AB1 at 450V ( Geekís suggestion) to have Po about 30W.
Iím saying ďto obtainĒ cause ,as a newbie , I donít know if itís correct ( Geek havenít seen it, yet ).
Maybe Iíll do fullish things so donít freak out!
I have attached the schem , hoping the gurus out there will help me!
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Old 13th September 2004, 09:17 PM   #2
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Resident,
Can't help you with your amp but in case you want the picture posted, click on 'Browse' in the 'Attach file:' section underneath the reply box.

/Hugo
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Old 13th September 2004, 09:32 PM   #3
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Hi,

Quote:
The driver stage , 6SN7 direct coupled to 6FQ7 LTP , is taken by coqsncoqs (a driver stage that he is working with arnoldc for an amp with EL34).
No idea what they're up to but using the octal version to drive the same tube but in its noval version doesn't make sense to me.

The 6CG7 and 6SN7 are electrically one and the same, only sockets are of a different type.

As for the rest of your QQs I'd need to see the circuit first to be able to answer.

Cheers,
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Old 13th September 2004, 10:05 PM   #4
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oups......
sorry!!
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File Type: jpg 6l6.jpg (15.4 KB, 594 views)
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Old 13th September 2004, 10:12 PM   #5
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Hope the schem is clearly enough.I don't know how to make good attachments,yet!!

@fdgrove
Quote:
The 6CG7 and 6SN7 are electrically one and the same, only sockets are of a different type.
I didn't know this.So,I can use 6SN7 with no problem,right?
I find it like it is in the attachment file.
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File Type: gif sn-fq_ltp_arnoldc_05-rc_voltages_small.gif (10.7 KB, 495 views)
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Old 13th September 2004, 10:33 PM   #6
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Hi,

Quote:
I didn't know this.So,I can use 6SN7 with no problem,right?
If you keep in mind that some of the 6SN7 variants are spec'ed for a plate voltage of 250VDC you'll be fine.
Doing it the other way, using 6CG7/6FQ7s throughout would be the easier way, probably cheaper too.

Arnold_C's input and splitter stage should drive the 6L6Gs without problem.
I didn't redo any math, but at first glance it should be O.K.

Cheers,
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Old 14th September 2004, 09:45 AM   #7
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Quote:
No idea what they're up to but using the octal version to drive the same tube but in its noval version doesn't make sense to me.
Me neither . arnoldc wanted (did?) to use a 6SN7 into a 12AU7 LTP. Don't know for sure if he had to do it that way (already had his chassis laid out that way?). My thinking on going with a 6SN7 into a 6FQ7 was if you were stuck into using an octal into a 9 pin noval, a 6FQ7 or a 6GU7/12BH7 would be better than a 12AU7.

See: http://www.diyaudio.com/forums/showt...984#post473984

Cheers
Wayne
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Old 14th September 2004, 10:31 AM   #8
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Quote:
Doing it the other way, using 6CG7/6FQ7s throughout would be the easier way, probably cheaper too.
I agree, a 3/4" (19mm) hole is much easier to drill/punch than a 1 and 1/8" (29mm) hole. And they're cheaper, even NOS, than 6SN7's. As far as the 6SN7 variants go, 6SN7GTA or GTB's are the ones to look for (450V max anode).

Plenty of DRIVE! More than enough for a 6L6! You'll see basicaly the same circuit in some EICO's and H.H. Scott amplifiers.

Quote:
So with 0.5 Vrms input Iíll have 47 V at each output of the phase splitter , right???
Yup! 66.5V RMS at each output (OUTA, OUTB). 188V P-P, 133V RMS between the two, that's at 500mV input no feedback. That's if my math is correct!

Wayne
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Old 14th September 2004, 02:51 PM   #9
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@ coqsncoqs

I see that arnoldc designs his circuits with MC7 (MicroCap 7) .I have downloaded MC evaluation 7 demo and the tubemods but I canít run any mode Ďcause it says that I must convert it from MC4 version to MC7.How can this be done?

If you donít know please contact arnoldc if he can help me. Does anyone have the original MC 7 program to send it by e-mail to me??? Please zipped!

Quote:
Yup! 66.5V RMS at each output (OUTA, OUTB). 188V P-P, 133V RMS between the two, that's at 500mV input no feedback. That's if my math is correct!
My calculations arenít the same. Please see again mine Ďcause Iíd like to know if Iím thinking right.
With 0.5 Vrms input Iíll have 47,2 Vrms ( gain 39,5 db or 94.4 -as it is in arnoldcís schem) at each output of the phase splitter . So 47,2*2=94,4 V rms from grid to grid .
The SV6L6 PP output stage needs peak 70 V grid to grid voltage or 49,49 V rms . So with an input about 0,25Vrms and without feedback I can drive the output stage at full power and have 30W .

I have redrawn the schem into two separate sections to be more clearer .
Please see the values of components if theyíre correct.
Any tips and hints is acceptable!!
I donít know the amount of FB ,yet. Thatís why Iím writing Rx and Cx. Iím designing the PSU write now .Hope to post it today , to have your opinion.
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File Type: jpg driver stage.jpg (69.6 KB, 434 views)
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Old 14th September 2004, 02:53 PM   #10
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And the output stage.
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File Type: jpg output stage.jpg (72.5 KB, 420 views)
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