First Budgie SE (Single-ended EL84 amp)

a 3W single ended EL84 amp for home, work & school

Postby EWBrown » Sun Aug 12, 2012 7:25 pm

I'm lovin' it too, three, four....

[:) ;) (lol)

/ed B
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mysterious object

Postby leadtower » Mon Aug 13, 2012 6:12 pm

Is this a new circuit? Or a re-worked budgie board? I have to pay more attention; sheesh!
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Postby brians7 » Mon Aug 13, 2012 9:24 pm

Shannon can you post a Budgie SE schematic to it for (RH84)? Of coarse when you get the time. Thanks Brian
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Re: mysterious object

Postby Shannon Parks » Tue Aug 14, 2012 5:29 am

leadtower wrote:Is this a new circuit? Or a re-worked budgie board? I have to pay more attention; sheesh!


New board. Making a Budgie family and this is the amp portion. The Budgie family characteristic will be the flipped upside Hammond chassis with a pre-drilled chassis top plate to facilitate easy construction.

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Postby Shannon Parks » Tue Aug 14, 2012 5:40 am

brians7 wrote:Shannon can you post a Budgie SE schematic to it for (RH84)? Of coarse when you get the time. Thanks Brian


I presume someone will do this before I get a chance to, but the mod will be pretty simple.

I still question the series feedback method for a triode VA (RDH3 bottom page 41) after not having success with an early Clementine prototype using it.

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exellamente'!

Postby leadtower » Tue Aug 14, 2012 9:34 am

We can place orders now?
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Postby Shannon Parks » Tue Aug 14, 2012 12:07 pm

Not yet, but very soon. I'll take orders by the end of the month and should have the top plates. Budgie SE amp boards will be $39, and the top plates will probably be $49.

It's configured for the Edcor XPWR136-120 for the power transformer and two Edcor GXSE10-8-5K as the outputs. I guess you can go ahead and order, as you'll have a 5 or 6 week wait from Edcor. Those are just under $100 shipped.

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Last edited by Shannon Parks on Mon Sep 17, 2012 8:11 am, edited 1 time in total.
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Roger That

Postby leadtower » Tue Aug 14, 2012 3:04 pm

Thanks Shannon; I'll do that.
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Postby EWBrown » Thu Aug 16, 2012 9:35 pm

For RH84 implementation, just connect a 470K resistor between the 6BQ5 plate (pin 7) and the 12AX7's plate, for each channel,
that should be easy to do this, on the solder side of the board.

Try RH84 mode with, and without, the global NFB, it may surprise you - I did this with a mini-sized 6BM8 / Russian 6F3P SE amp ,
and the combined NFB made it sound even better than the standard "OPT secondary, thru a resistor back to to VA cathode" NFB scheme.

HTH

/ed B in NC
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Postby TerrySmith » Fri Aug 17, 2012 6:12 am

Does this have enough gain to use standalone or is a preamp needed?
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Postby Shannon Parks » Fri Aug 17, 2012 8:59 am

TerrySmith wrote:Does this have enough gain to use standalone or is a preamp needed?


It doesn't need a preamp. 500mV will drive it to 3W, so any device - like a smartphone or music player or even the Budgie phono - works fine. It was a key design consideration.

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Postby soundbrigade » Wed Aug 22, 2012 10:17 am

We are coming (or going) to Chicago for X-mas. Maybe I hire a car and come down (or up= to you and pick up a card or two or more.
I can make a notification on the Swedish forums and offer guys a groupsex ... group-buy , mean. :$
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Postby Shannon Parks » Wed Aug 22, 2012 2:31 pm

soundbrigade wrote:We are coming (or going) to Chicago for X-mas. Maybe I hire a car and come down (or up= to you and pick up a card or two or more.
I can make a notification on the Swedish forums and offer guys a groupsex ... group-buy , mean. :$


Sounds cool!

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Postby EWBrown » Thu Nov 01, 2012 7:27 pm

It's alive!!!!!

I just completed my SE Budgie build, ran the DC voltage checks - all were within 1% of the voltages show non the schematic.

Tubes installed are J/J; 2 EL84s and 1 ECC803 (fancy 12AX7A).

Hooked it up to the test setup CD player and speakers, and it sounds very nice! [:) (love) [:)

Only changes I did were to use a Hammond 156R (similar to C354) choke, and I decided not to install the 4 20 ohm resistors and headphone jack, in its place,
I installed a power-on LED, and aded a couple of 1N4007s (connected to 6.3V A & B, a 180 ohm resistor and 47 uF / 16V cap to light it up).

I just need to find a better looking knob for the volume control, right now it's just an old gray plastic "Heathkit" knob, scavenged from some 50 year old dead Heathkit device. :/

Image

/ed B
Last edited by EWBrown on Sat Jan 24, 2015 10:25 pm, edited 4 times in total.
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Postby jollyrogr » Thu Nov 01, 2012 9:36 pm

Cool! Can't wait to see the pics. My pcb's just arrived today so I'm revved up to get started. So you used the heater voltage to light up your power LED?

I haven't ordered any tubes yet but I think I will use JJ ECC803 and the Sovtek EL84M's

What are you using for speakers?
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