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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 28 Nov 2011, 23:55 
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Joined: 20 Sep 2008, 19:49
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Location: Montreal, Canada
Hi guys,

I have read somewhere that the 6W6 is a real sleeper tube...so I just bought 4 of them on e-bay.

Does anyone from this forum ever tackle this tube...apparently when triode strapped it sounds just like a 45 so I figure hey..lets give it a try I just happen to have a few small Edcor OPT on the shelve.

If someone has any idea as to how to properly bias this tube it would be awesome, this is how I intend to connect it but I can be totally wrong :eek:

Any help with either SE, SE triode strapped or PP would be awesome.
Attachment:
SET_6N1P_6W6GT.JPG

Thanks in advance,
Isophon

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PostPosted: 29 Nov 2011, 01:09 
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Give me 24 hours and I'll get you a triode stage load line design optimized for overall performance.

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PostPosted: 29 Nov 2011, 02:48 
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Suncalc wrote:
Give me 24 hours and I'll get you a triode stage load line design optimized for overall performance.


Awesome Matt !!

Isophon.

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DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
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PostPosted: 29 Nov 2011, 06:13 
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Joined: 14 Feb 2010, 13:13
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Location: Lisbon, Portugal
I like that IRF840 based filter type. I wonder how good can it perform.

Cheers,
Miguel


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PostPosted: 29 Nov 2011, 07:50 
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HT Performance wrote:
I like that IRF840 based filter type. I wonder how good can it perform.

Not for very long with that big cap on the source.

Isophon, you might want to drop that value significantly - it's not even needed there and puts huge charging currents through the MOSFET.

Cheers!

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PostPosted: 29 Nov 2011, 12:04 
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Joined: 20 Sep 2008, 19:49
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Location: Montreal, Canada
*** I wonder how good can it perform. ***

It works nicely, before the B+ ripple filter I normally have about 25-30mV of ripple, after the ripple it's down to about 3-5mV so it's dead quiet. This part is taken from Peter Millett's 'Engineer Amplifier so this guy know what he's talking about. See here : http://www.pmillett.com/dcpp.htm

You can fine tune the output voltage by tweaking the 10K resistor.

Rgds,
Eric

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DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
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DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
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To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 29 Nov 2011, 12:30 
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Joined: 20 Sep 2008, 19:49
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Location: Montreal, Canada
Geek wrote:
HT Performance wrote:
I like that IRF840 based filter type. I wonder how good can it perform.

Not for very long with that big cap on the source.

Isophon, you might want to drop that value significantly - it's not even needed there and puts huge charging currents through the MOSFET.

So, should I be reducing the value from 220uF (the one connected to the source of the MOSFET) to about 47uF ?

Total current through the MOSFET should be around 100mA max. I wonder if the ripple will increase with a 47uF...

Thanks for the help.
Isophon

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DIY SS Amp : LM3875 GC | TA2024 | TA2020 (AMP-6) | TA2022 | Amp Camp Amp | JLH
DIY Tube Amp : RH84 SE | 6V6 SET | 13FD7 SET (Chinook) | 807 UL SE | 6BQ5 Class A PP UL | 6LR8 SE
DIY Spkrs : Cyburgs Needle | MLTL (FE206E) | CSS EL70 BR | Open Baffle (Alpha 15A + FE206En) (in process...)
DIY Pre-Amp : MooseFET.
To come : MLTL (CSS enabled EL70) + more tube amp...


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PostPosted: 29 Nov 2011, 13:42 
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Joined: 08 May 2009, 08:20
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Location: Duesseldorf, Germany
In my experience, Mos-Fet filters can perform very well. I have used them with some headphone amp circuits (also the Szekeres)
and with EL84 tube amps. They act like a "capacitance multiplier" (http://www.tcaas.btinternet.co.uk/jlhcapmult.htm
and adjustable regulators http://www.fortunecity.com/rivendell/xentar/1179/theory/seamptheory/SEAmplifiertheory.html (scroll down).

Depending on the design, they provide high currents or high filtering.

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Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


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PostPosted: 29 Nov 2011, 21:58 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
Ok, I'm not sure exactly what you mean by a "sleeper" tube. The 6W6 is one of the family of lower power beam power tubes for use in support of television deflection service and small audio amplifiers. It is in the same class as the 6V6 (and all it's variants), 6Y6, and 6K6.

While I do believe that the 45v bias point shown in your schematic is probably good if using this as a guitar amplifier, it is far too high a bias voltage for effective SE operation of this tube for decent fidelity. Since the 6W6 cannot support UL operation due to screen limitations, I'll start with a triode strapped design. In this operating mode, the sweet spot for loading the tube is around 3kΩ. So I did three load line designs for the power stage since you didn't mention what impedance were the Edcors you had on the shelf.

Here is the schematic for this design with the pertinent performance characteristics for 2.5kΩ, 3kΩ, and 3.5kΩ loads.
Attachment:
pic764.jpg
You're probably best off with the 2.5kΩ design, but any should be acceptable. Edcor has ten watt GXSE transformers in 2.5kΩ and 3.5kΩ and XSE transformers at 3kΩ. This design needs 20v p-p to drive it so I would use a standard 12AU7 bypassed cathode preamp stage to drive the tube. Something like this. Then if you wanted more gain you could just swap preamp tubes. The whole circuit would look like this.
Attachment:
pic765.jpg

This is a nice simple design that you should be able to put together in an afternoon. If you need help with a PS design let us know.

I hope this helps.


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PostPosted: 30 Nov 2011, 04:10 
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Joined: 08 Aug 2009, 03:11
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Location: Chilliwack, BC
Isophon wrote:
So, should I be reducing the value from 220uF (the one connected to the source of the MOSFET) to about 47uF ?

Total current through the MOSFET should be around 100mA max. I wonder if the ripple will increase with a 47uF...


Yes, and Pete will most likely agree ;)
(we think a lot alike on forums)

I would use 4.7uF to 47uF, not critical. It's more to keep audio floating on the power rail out of mischief (it's a power filter, not a regulator)

The power filter here will be the cap * gm of the transistor.... 22uF * ~4500 = a tad under 100,000uF equivalent filtation. Lowering the last cap to 47uF will do nothing to the ripple, but will go a long way at reducing transistor dissipation on AC charging peaks and turn-on surge.

Cheers!

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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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