6LU8 Push-pull power amp and other builds

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Tue Jun 02, 2015 12:34 pm

this is a classA 6bq5/el84 tube amp by a guy called Brgy Tanod from cebu....

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Tue Jun 02, 2015 12:46 pm

at last tumunog na, 4P1L parallel SET, design goal was to run the tubes as if they were
2A3's, 250 volt plate and 60 mA cathodes(total for the two tubes)...
....a slight tweaking will still need to be done...
i am gettng the filaments to run at least 4 volts...
it is true what they say about this tube being parallel friendly...
and while i used dc to power the filament, i suspect that just like
the 2A3, these tubes can run on AC filaments at 2 volts and still be hum free... 8)

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Sat Jun 20, 2015 7:39 pm

my 6HF5 pp class AB2 power amp.....
work in progress, about to complete...
tube compliments, 6H8c cathode followers,
6BH11 input and phase splitters, 6922 input buffer...

filaments only and psu caps testing, raw B+ was 570 volts at an input of 230 volts ac line...
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power draw, i estimate final idle power draw in the 180 watt range when amo iis fully biased..
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Thu Jul 02, 2015 8:42 pm

intermission.....Danny 40W power amp....designed by Danny Eulogio (based in Seattle, Washington) and PCB lay-out by Eng'r. Dandy Menor from Baguio City....

got the chassis powder coated.....
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modified the speaker protector delay to >10 secs.....
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Sun Jul 05, 2015 12:25 pm

another single ended amp in the works...
using the 4D32 beam tetrodes...
contemplating enhanced triode mode...
tubes came from Gerry Sta Maria for 1500 each...
got another 10 tubes when they were put on sale at Surplus Sales of Nebraska...
winding the power traffo, with about 500VA capacity for an aoutput of about 15 watts per channel
these tube will give the KT150 a run for the money, rated at about the same power,
the 4D32 has a bigger cathode, filaments running 6.3 volts and 3.8 amperes...
http://www.r-type.org/exhib/aai0005.htm

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Thu Jul 09, 2015 11:03 am

taking my sweet time...output offset adjustments confirmed working,
output bias set to about 50mA per collector...
i set the 2k bias pot to 1k and i was at the target current, no further adjustment needed,
whe you maximise to 2k, the output stage is deep in cut-off at power up and power meter
reads12 watts, now my power meter reads 17 watts, meaning the output stage are
now dissipating an additional of 5 watts, things are cool to touch after a few hours...
after two hours meter reads 16 watts for just 1 watt per output trannie,
and the good news is, bias is not increasing....

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Wed Jul 15, 2015 5:06 pm

unused old stock TV tubes, over a thousand of them, now doing inventory, easily over a thousand of them...

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Fri Jul 17, 2015 9:38 am

i found a solitary 6LW6, the king of TV horizontal tubes, i know where to get them,
i am tryng to convince the store to sell me a sleeve of those tubes...

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one such amplifier using the tube...
http://www.tiffe.de/roehren/ga399ma.pdf

above article explains why this tv tube is better than traditional audio beam tetrodes/pentodes...

been thru over 200 power tubes, some of which sells northwards of U$50 n the states today..
the U$1 tubes i purchased years ago are now selling for more than U$4 nowadays...
it seems that as soon as a tv tube is discussed at diyaudio.com, the chinese will gobble
them up in the tens of thousands.... :o :devil:
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Tue Aug 04, 2015 7:15 pm

newly built 832 push-pull, for testing soon....

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Fri Aug 07, 2015 2:37 pm

Stromberg-Carlson, what makes this small amp sound so fabulous? small OPT's, no boutique caps, and yet bass is tight and fast, cymbals shimmering,,,,;)

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Re: 6LU8 Push-pull power amp and other builds

Postby edgarryan » Tue Aug 11, 2015 9:00 pm

tony wrote:Stromberg-Carlson, what makes this small amp sound so fabulous? small OPT's, no boutique caps, and yet bass is tight and fast, cymbals shimmering,,,,;)

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If only it works like it used to.

I have full faith in you that you could repair it and make it sound like new again. :)
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Wed Sep 02, 2015 7:39 am

3rd 6LU8 pp amp build.....i purchased these tubes for $1 each, now they sell for 4$....

OPT's...
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filament only shows 48 watts draw...
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partial underside...
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preliminary schematic...
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Thu Sep 10, 2015 5:36 pm

6LU8 build no.3 completed....

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Tue Sep 22, 2015 4:21 pm

4KN8 CCDA rev. 02 updated using CCS mosfet active loading......

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Wed Sep 23, 2015 5:19 pm

discrete transistor phono stage....

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Fri Oct 09, 2015 8:07 pm

build no.2, this time with rails of +-50 volts....as you can see, caps upsized to 63 volts...
progress updates...

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collection of parts, final....the speaker protection board sits atop the psu board...
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Tue Oct 13, 2015 3:13 pm

speaker delay and dc protection board for the dny40w amp done...

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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Thu Oct 29, 2015 7:41 am

how's this for an amplifier casing?
sent to Bell Metals for electroplating brght zinc.
then to Uni-Pacific powder coating shop for painting...
a 2.5mm aluminum L-type sub-chassis will hold all the heavy components...
so this casing will form an outer shell....

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tops and sidings will be colored matte black(?)....powder coated of course...
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with lfting handles to be installed....
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Mon Nov 02, 2015 6:27 pm

DNY40W second build....chasis already poweder coated...

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partial assembly, power supply and speaker protection, installed and tested, confirmed working...
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Re: 6LU8 Push-pull power amp and other builds

Postby tony » Wed Nov 11, 2015 4:37 pm

installed small aluminum heatsinks for the VAS ang the big CCS to keep them cooler...

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tested the boards for output offset and set it to 0mV....idle current set to minimum...
series lamp tester used here...
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wiring up after confirming boards...
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