Trying to achieve 25-30 watts... help please!

diaz028 · 8th November 2010, 01:00 AM

How much power can I get from 400V B+?

My OT is rated at 35 watts.

So I am just wondering what tubes I can use to achieve about 25-30 watts of audio power, other than cathode biased 4xEL84?

1. Cathode biased 4 x 6V6 ?
2. Cathode Biased 2 x 6L6 ?

Just wondering. All specs for the 6V6 and 6L6 show wattage ratings with B+ of 360V and 450V, but nothing in between, and not always with cathode bias.

Thank you!

chrish · 8th November 2010, 01:06 AM

I built a fixed bias 6L6 6L6GC AB2 Amp 400 volts B+ with MOSFET source followers and DC coupled two stage diff amp driver.

eeyore · 8th November 2010, 01:11 AM

Depends on topology (SE or PP) and Class. But what is the current and voltage rating, as the OPT may not have enough current capability. Too many variables...

stokessd · 8th November 2010, 01:47 AM

PP pairs of 6L6GC's (5881) with fixed bias will get you there.

PP pairs of EL34's (6CA7) with fixed bias will get you there.

PP pairs of KT88's with fixed bias will get you there but that's more tube than you have output transformers to handle.

You'll also need a power transformer that can source that much power.

Sheldon

aardvarkash10 · 02:25 AM

Quote:

Originally Posted by diaz028

How much power can I get from 400V B+?

Lots!

Is this for geeetar or hifi?

Where is your 400V coming from and how many mA can it deliver? What heater current can it deliver?

Quote:

Originally Posted by diaz028

My OT is rated at 35 watts.

OK - what is its primary and secondary impedance?

Quote:

Originally Posted by diaz028

So I am just wondering what tubes I can use to achieve about 25-30 watts of audio power, other than cathode biased 4xEL84?

1. Cathode biased 4 x 6V6 ?
2. Cathode Biased 2 x 6L6 ?

Just wondering. All specs for the 6V6 and 6L6 show wattage ratings with B+ of 360V and 450V, but nothing in between, and not always with cathode bias.

aaaaaaahhhh you get to enter the magic realm of load lines.....

Easy entry level learning stuff here

diaz028 · 8th November 2010, 02:17 AM

Class = A or AB Push Pull (whatever works)

PT = 300 0 300 @ +150mA
OT = 35watts @ 4000cct
Filter = SS rectifier, 44u input cap, 10h choke, 44u grid cap.

Depending on the tubes, B+ should end up around 350-400V. Amp is not built yet, still in the design phase.

tubelab.com · 8th November 2010, 02:27 AM

Quote:

My OT is rated at 35 watts.

The important question that hasn't been asked here is what is the impedance of the OT. If it is too high, you can't get there from here.

kevinkr · 8th November 2010, 04:20 AM

Quote:

Originally Posted by tubelab.com

The important question that hasn't been asked here is what is the impedance of the OT. If it is too high, you can't get there from here.

The poster says 4000cct, which I assume is 4K plate to plate, but who knows.

richwalters · 8th November 2010, 07:21 AM

Using KT88's with 400V B+ & fixed bias with 4KA-A should get around 40W walkover and a very long life. Perhaps a luxury overkill.
The 6L6 was the standard workhorse for the popular 30W-1960's guitar amps. The number of circuits around is vast.

I often run output trannies well-over their ratings. Sofar without failure. A 100W from a 50W tranny is fine solong deep bass isn't required. The trick is not to disconnect the output under load.

richy

artosalo · 8th November 2010, 08:52 AM

With a PP-pair of 6L6, 807, 6P3S-E etc. you can get some 25 to 35 W depending on bias system. With fixed bias you will get more power with better efficiency.

Here is one of my amplifiers I built few years ago with Edcor transformer and 6P3S-E tubes.

It has the preamplifier, tone controls and balance, but can be easily simplified.

8th November 2010, 01:00 AM	#1
diaz028 diyAudio Member Join Date: Jun 2007	Trying to achieve 25-30 watts... help please! How much power can I get from 400V B+? My OT is rated at 35 watts. So I am just wondering what tubes I can use to achieve about 25-30 watts of audio power, other than cathode biased 4xEL84? 1. Cathode biased 4 x 6V6 ? 2. Cathode Biased 2 x 6L6 ? Just wondering. All specs for the 6V6 and 6L6 show wattage ratings with B+ of 360V and 450V, but nothing in between, and not always with cathode bias. Thank you!

8th November 2010, 01:11 AM	#3
eeyore diyAudio Member Join Date: Aug 2005	Depends on topology (SE or PP) and Class. But what is the current and voltage rating, as the OPT may not have enough current capability. Too many variables... __________________ DF http://diy-audio-blog.blogspot.com

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8th November 2010, 01:06 AM	#2
chrish diyAudio Member Join Date: Oct 2003 Location: Sydney	I built a fixed bias 6L6 6L6GC AB2 Amp 400 volts B+ with MOSFET source followers and DC coupled two stage diff amp driver.

8th November 2010, 01:47 AM	#4
stokessd diyAudio Member Join Date: Nov 2002 Location: Fort Wayne, IN	PP pairs of 6L6GC's (5881) with fixed bias will get you there. PP pairs of EL34's (6CA7) with fixed bias will get you there. PP pairs of KT88's with fixed bias will get you there but that's more tube than you have output transformers to handle. You'll also need a power transformer that can source that much power. Sheldon

8th November 2010, 02:17 AM	#6
diaz028 diyAudio Member Join Date: Jun 2007	Class = A or AB Push Pull (whatever works) PT = 300 0 300 @ +150mA OT = 35watts @ 4000cct Filter = SS rectifier, 44u input cap, 10h choke, 44u grid cap. Depending on the tubes, B+ should end up around 350-400V. Amp is not built yet, still in the design phase.

8th November 2010, 07:21 AM	#9
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	Using KT88's with 400V B+ & fixed bias with 4KA-A should get around 40W walkover and a very long life. Perhaps a luxury overkill. The 6L6 was the standard workhorse for the popular 30W-1960's guitar amps. The number of circuits around is vast. I often run output trannies well-over their ratings. Sofar without failure. A 100W from a 50W tranny is fine solong deep bass isn't required. The trick is not to disconnect the output under load. richy

8th November 2010, 08:52 AM	#10
artosalo diyAudio Member Join Date: Feb 2010	With a PP-pair of 6L6, 807, 6P3S-E etc. you can get some 25 to 35 W depending on bias system. With fixed bias you will get more power with better efficiency. Here is one of my amplifiers I built few years ago with Edcor transformer and 6P3S-E tubes. It has the preamplifier, tone controls and balance, but can be easily simplified.

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