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Old 24th February 2008, 05:36 PM   #1
Ryssen is offline Ryssen  Sweden
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Default TentLabs Directly Heated Tubes Supply

http://www.tentlabs.com/Products/Tub...ent/index.html
Is it worth the price?
Has anyone done anything like this DIY?
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Old 24th February 2008, 07:15 PM   #2
Sheldon is offline Sheldon  United States
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Default Re: TentLabs Directly Heated Tubes Supply

Quote:
Originally posted by Ryssen
http://www.tentlabs.com/Products/Tub...ent/index.html
Is it worth the price?
The only thing that matter is what it's worth to you. They work fine.

I considered DIY, and that's pretty easy if you have a few volts to burn. The nice thing about the Tentlabs piece, is that you can use the regular AC windings, i.e., 5vAC for 5VDC.

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Old 24th February 2008, 07:19 PM   #3
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I am using these on my 300b monoblock amps. I like them better than the voltage regulated DC that I had before. To me they sound as good as AC heated filaments. DIY hifi supply is great to deal with and good turn around in product. Price is subjective I guess.

Hope this helps,
ck
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Old 24th February 2008, 09:17 PM   #4
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Default DIY current heating

Of course there's a DIY option!

New DHT heater

This circuit is still in constant use - with same 300Bs, and the filament voltage is still 4,9V, nearly 4 years later.

Piotr compared it to other filament circuits in a linestage, and liked it best.

If you try this current source, or maybe use the Tentlabs, you will not go back... AC heating sounds REALLY bad in comparison.
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Old 26th February 2008, 07:47 PM   #5
Ryssen is offline Ryssen  Sweden
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Quote:
Of course there's a DIY option!
Of course..Interessting,if I want to use this with GM70,I guess R4 needs to be lowered,what about R2/R3?Trafo 16v or more?
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Old 27th February 2008, 03:38 PM   #6
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Default Re: DIY current heating

Quote:
Originally posted by Rod Coleman
Of course there's a DIY option!

New DHT heater

This circuit is still in constant use - with same 300Bs, and the filament voltage is still 4,9V, nearly 4 years later.

Piotr compared it to other filament circuits in a linestage, and liked it best.

If you try this current source, or maybe use the Tentlabs, you will not go back... AC heating sounds REALLY bad in comparison.

Yup, it is very, very good. Thanks Rod for sharing!
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Old 27th February 2008, 06:24 PM   #7
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Default GM70 design notes

GM70 is 20V 3A, so that will need a very BIG power supply!

start with Trafo 24V, with very high VA (power) capability, maybe 500VA. Maybe use a 24V control panel Trafo (get these used from salvage company or industrial seller).

Use 100V 10A schottky diodes ( try the ONSEMI.com site for their sample program, get 10 different diodes, 25pcs each for $15 US)

then add high quality capacitors 10000 or 15000uF/35V, like Panasonic TSUP series. Parallel capacitors a good idea - make sure ripple current handling is MINIMUM 8 Amperes.

This supply should give you about 27V with 2V peak-to-peak ripple. Use powersupply Designer II to check that the parts you buy will give around these figures: 26V to 30V is needed. The dc output you get is very strongly dependent on the trafo resistances, so measure these (pri and sec) and put these, and the open-voltage into PSUDII. If you get too much voltage, use a wirewound resistor to drop it to 28V.

Set R3= 3,3K and R2= 27K or 24K to give about 2 to 5V across the top transistor.

Each power transistor radiating 15W, so a high power transistor is needed, look for TO-220 packaged parts with at least 60W handling. The BDX53C is a darlington with Cob (typically) 100pF at 5V Vce. Use an isolating sheet and a very large heatsink (maybe 1 deg C/W)

test the circuit for 1 hour using 4 parallel 24 ohm (50 Watt) wirewound resistors as a load - don't connect to your high-priced triode until you are sure the transistors/heatsink can handle the heat.

Next, adjust the current sense resistor. Use a 0,22ohm TO-220 packaged part, and add 3 or 4 43 ohm leaded resistors in parallel. when the circuit is hot, cut the 43 ohms out, 1 by 1, until current is exact.

good luck in building!
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Old 27th February 2008, 06:46 PM   #8
Ryssen is offline Ryssen  Sweden
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Yes BIG!
Thanks!
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Old 29th February 2008, 09:54 PM   #9
Ryssen is offline Ryssen  Sweden
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Quote:
Set R3= 3,3K and R2= 27K or 24K to give about 2 to 5V across the top transistor.
So the voltage across Q1 isnt that critical(I mean for other filiamentvolatges (2-7volts)can R2 or R3 be made adjustable?
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Old 1st March 2008, 07:36 AM   #10
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I used them and heared them several times and they are worth every penny of the price. Build a few 300B amps and with the Tentmodule the background is blacker than black, more detail and so on. I don't want to advertise for Tentlabs, but just want to make a statement that it is really that good.
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