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Old 1st May 2011, 04:40 PM   #1
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Default What to build? (I have a lot of parts)

Hi guys. I have a few things that I would like to use for a new project. Any ideas of what I can do with them?

(3) C-2305 Chokes - 5H @ 100mA, 300Ω, 1.5KV.
(2) RH-1540 Chokes - 15H @ 40mA, 475Ω, 1.07KV
(20+) Transformers - 250-0-250, 3.15-0-3.15, 75mA
(100+) Capacitors - 10uF to 200+uF (300+WV)
(5+) Turret Boards (most are pretty small)
(1) Pre-drilled board (kind of like a breadboard only with drilled holes)

I have tons of other stuff like transistors, resistors, capacitors, inductors, heatsinks, and some transformers (some even military transformers that are in heavy steel enclosures).

I don't have any good amplifier for listening to music, which I love to do!

Thank you; I appreciate any input!
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Old 1st May 2011, 04:59 PM   #2
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Why not a parafeed amp with all those chokes? I wish I had your problem!
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Old 1st May 2011, 05:33 PM   #3
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Quote:
Originally Posted by carbondated View Post
Why not a parafeed amp with all those chokes? I wish I had your problem!
I'm sorry Carbon; I don't know what "parafeeding" is?

Thank you for the input.
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Old 1st May 2011, 06:12 PM   #4
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Need to know more about your power transformers ie how much HT current are they good for. If 75ma is the best you've got have you any that could be paired for monobloc use.

Can't really consider options on valves, amp topology or output transformers without this info.


Brgds Bill
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Old 1st May 2011, 06:48 PM   #5
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FingerBoy: What have you got for speakers, ie how sensitive? Whats the budget? What are your listening habits? How big is your listening room?

You have some chokes that would work for small mono blocks; your power transformer voltage & current ratings are a bit small though, even for monos.
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Old 1st May 2011, 07:21 PM   #6
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My speakers are just okay. Really nothing special: 88dB sensitivity. I am a student that doesn't have much money; but I have a lot of parts.

I also have a few aluminum chassis sitting around.

I can fish around and I may be able to find a higher current transformer. We have a lot of old military stuff.

The goal is to just get something better than my junk receiver from the 1980s.

If I need to use a MOSFET power amp; so be it. It's better than the all-in-one chip amp that the receiver has.
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Old 1st May 2011, 08:52 PM   #7
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Are some (or all) of the power transformers matching? If you have a pair you could do a PP EL84 or 6V6 design....good for somewhere between 6W and 12W or so, depending on triode or UL outputs.

The pair of chokes would work for this also. Do you have any tubes or output transformers?

Edcor XPP series OT's would be a good budget choice, like an XPP10-8-8K ($17/ea) or XPP15-8-8K ($20/ea). Spend the $3/transformer difference to get the 15W......

Do a search here for Gingertube's baby Huey (EL84 UL-12W), Sy's red light District (EL84 Pentode-15W), Eli's El cheapo and Poindexter's 6GK5/6V6 music machine (6V6 triode 6W).

EL84 Amp - Baby Huey

Last edited by boywonder; 1st May 2011 at 08:56 PM.
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Old 1st May 2011, 09:19 PM   #8
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I have over 10 of the exact same transformer. The 250-0-250 HV and 3.15-0-3.15 Filament. The amperage isn't very high though.

I do not have any tubes, but I may be able to salvage a bunch of output transformers. We have hundreds of misc. transformers sitting around collecting dust.

I don't plan to be BLASTING my music, but I would like something that I can hear well at decent volumes.
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Old 1st May 2011, 09:29 PM   #9
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There are some things I don't understand about that schematic. What are the "bias" blocks in the shematic. You just substitute the blocks with the components in the dotted box?

I never understood what "bias" really is? Does it basically shift the DC offset?

Also, I don't seem to find the input impedance and output impedances of the OT?

I'll fish around to find a pair of OTs tomorrow.
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Old 1st May 2011, 10:57 PM   #10
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Quote:
Originally Posted by fingerboy21 View Post
There are some things I don't understand about that schematic. What are the "bias" blocks in the shematic. You just substitute the blocks with the components in the dotted box?

Yup.

I never understood what "bias" really is? Does it basically shift the DC offset?

You need to apply a negative bias DC voltage to the tube's grid (or just make the grid more negative than the cathode) to set an operating point for the tube. The negative voltage corresponds to a bias current that will flow from the anode to the cathode. Without it, the tube is wide open "on". Unlike transistors, tubes are "full on" without a bias voltage.

Also, I don't seem to find the input impedance and output impedances of the OT?

Both PP EL84's and 6V6's like 8K to 10K primary, and either 4, 6, or 8 ohm secondary depending on your speakers.

I'll fish around to find a pair of OTs tomorrow.

If you find some, you have to determine if they have UL (screen grid) taps. Without those taps, you are limited to triode or pentode operation.
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