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Old 23rd June 2008, 06:46 AM   #1
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Default tube newbie needs guidance

hey everyone,

I just stumbled across an old pair of monoblocks that where in pretty rough shape (They did work just looked hideous and had seen better days) so I salvaged what I could and was looking for suggestions on what to use the parts for

the salvage list is as follows

a pair of hammond1609 transformers
a hammond 270ex transformer

4x 6v6GT's (sylvania, signet, marconi and rogers)
2x 6sc7's (phillips and rogers)
1x 5y3gt (marconi)
1x 5y4gt (westinghouse)
1x 6sc7 (rogers)

and 1 unidentified tube made by rogers but looks very similar to the 6sc7 in terms of the size

I have built a few small headphone amps without any issues (although reading schematics isn't a strong point but is becoming more clear), and look forward to reading a fair bit more into tubes but any direction would be great!

from what i've read so far it seems a 6v6 pushpull amp would be the best use of the 1609's
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Old 23rd June 2008, 10:40 AM   #2
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That will work. It's also suitable for p-p EL84, 6BQ5, 6973, 7189. No doubt there's many vertical amplifier tubes (e.g., 6GF7) that would also give you excellent results with the 10k plate to plate (nominal) impedance.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 23rd June 2008, 11:30 PM   #3
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Hi Mox and welcome. I see you are flatlander as well! 6V6 PP is a good choice considering the parts you have. Let us know how you make out.

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Old 24th June 2008, 12:43 AM   #4
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Read the "El Cheapo" saga. The 1609 O/P trafos will work in a triode wired EC. Keep the "28" Hz. high pass freq., to protect against core saturation.

Save the 270EX power trafo for a preamp or SE amp project, as it comes up short in current capability, when the needs of a PP "12" W. O/P tube stereoblock are considered.

The salvaged tubes are "all over the place". Properly matched pairs of O/P tubes are appropriate in PP amps. You could do a DECWARE SE84 style SE stereoblock that employs the 6V6s and 270EX power trafo already in your possession.

The 6SC7 is a twin triode whose electrical character resembles the 6SL7, 5751, and 12AX7, but it has a single, shared, connection for both cathodes that limits its utility.
Eli D.
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Old 24th June 2008, 03:14 AM   #5
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Thanks for the suggestions. I've got a lot of reading ahead of me before I can begin understanding a lot of what is said (especially in the el-cheapo thread you linked that I skimmed through a bit)

Ideally I want to find the best fit to use the available parts to keep costs down (being a poor student with an audio hobby isn't the easiest thing to manage )
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Old 24th June 2008, 06:52 AM   #6
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looking aroudn a bit more i found a 6v6 version of the baby huey amp using hammond 1608 output transformers

how would this compare to the el-cheapo in terms of ease and cost of build?
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Old 24th June 2008, 11:48 PM   #7
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Both the 1608 and 1609 are rated for 10 W. You can expect approx. 12 W. from a UL mode PP pair of "12" W. tubes. Pentode mode will yield a bit more.

Approx. 6 WPC is what you get from triode wired 6V6 family tubes set up as PP pairs. That works very well with the O/P "iron" you already have.

Allied Electronics has all the power magnetics needed to construct an "El Cheapo". Look here to get the stock #s.

Jim McShane sells all the small parts needed to construct an EC, at fair prices.

All that's left is a chassis. That requirement can be filled by purchasing a large/deep plain Aluminum baking pan at your "local" WalMart.
Eli D.
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Old 25th June 2008, 06:35 AM   #8
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Thanks Eli,

I did see Jim's page in my skimming the link you posted earlier. I think the EC will be the eventual choice once I feel confident enough to undertake it.

Now to start studying schematics.
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Old 26th June 2008, 05:08 AM   #9
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I printed off the most recent schematic for the EC and think I have a decent idea of how it works minus the specific technical aspects but did have a few questions.

Link to schematic I was looking at.

First thing is how the circuit actually is setup, mainly where components are soldered in. Are they soldered just on the black dots or do they also get joined when the lines cross (see right below the 4.7 uF cap between b2+ channels 1 and 2)

I know the Amp section is for one channel, but is the power supply also? And would it need to be duplicated for the second channel of the amp (essentially doubling the cost of the iron necessary)?

Also where does the LTP Cathodes section of the CCS connect to? I'm guessing somewhere on the tubes themselves since everything else is matched up from power to amp.

Also I wasn't able to ocate the symbol at the very leftmost side of the amp section where there is a circle with a bend below it.

Still have lots more reading to do, but these questions should put me a bit closer to understanding.
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Old 26th June 2008, 11:32 PM   #10
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The black dots are for the connection points, the lines simply crossing are not connected. The LTP ccs goes to the negative voltage supply. The funny symbol is for an input connection like a rca jack.
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