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Old 9th March 2008, 03:07 AM   #1
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Default Tubelab SE monoblock?

How best could one build a monoblock amp out of Tubelab SE? Do I just buy the board but half the quantity of the rest? Should the resistor and cap value be recalculated?
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Old 9th March 2008, 07:12 PM   #2
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Now this is a question that no one has asked yet.

You will need all of the power supply components including the filament regulator since the power supply is common to both channels. This is C1 through C7, R1 through R7, R30 and R35, D1 through D5, U1, and an octal socket.

You will need the components to populate one channel of the PC board. R8 through R18, R31 and R34, C8 through C10, Q1, U2, a 9 pin socket and a 4 pin socket.

The resistor that drops the filament voltage for the 5842's (R3) will need to be a higher value since there is only one tube (half the current) the actual resistance value depends on how much voltage vour filament winding puts out.

Depending on your choice of power transformer, R6 may need to be a higher value since there will only be one PowerDrive circuit. The negative voltage will be higher because only half of the current is being drawn leading to too much dissipation in the mosfet. This is probably not required for a 540 VCT transformer used for 45 tubes but will be needed for a 600 VCT or higher transformer used for 300B tubes.
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Old 11th April 2008, 02:21 AM   #3
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If using the same PT as stereo, should R3 and R6 value be doubled?
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Old 12th April 2008, 09:23 PM   #4
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Quote:
If using the same PT as stereo, should R3 and R6 value be doubled?
In theory yes. What output tube are you planning on using? And what power transformer, the 272JX? I am in the process of building up another board. I may be able to take some measurements on a board with a few strategic parts left out.
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Old 13th April 2008, 02:31 AM   #5
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The same 2A3 output tube and same 272JX PT. In other words everything is same as if I was building a stereo amp but skip one channel. Two R3 and R6 should be connected parallel?
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Old 19th April 2008, 06:13 PM   #6
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I have an opportunity to get a Hammond 272BX PT locally at a discount price and was wondering, should it be a good choice for this monoblock with 2A3 OP tubes?
Spec is as follows.
Secondary: 300-0-300 V, 100 mA
Filament winding 1: 5 V, 2 A
Filament winding 2: 6.3 V, 3 A
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Old 19th April 2008, 09:47 PM   #7
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hello,
I'm building a 300b amp similar of tubelab without pcb in mono version and I'd like to ask about two tweaks:
anyone have tested 6c45 instead of 5842?
and 10m45 as CS of the 300Bwith cap and toroidal transformer (no gap) on the output?
Have a nice day .
Guglielmo
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Old 27th April 2008, 08:51 PM   #8
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Hereís an update for those who may be contemplating TubelabSE monoblock amp. I put two R6 in series to deal with half the power draw and increased R4 value (and wattage) to bring down B+ voltage. For some reason I didnít have to change R3. It works with 272JX PT for 2A3 tube even though R4 gets hot. I may eventually get a smaller PT but until then, this project turned out to be a doable one.

I thank Tubelab for all the help.
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Old 28th April 2008, 07:02 PM   #9
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Correction, R3 did have to be changed to higher value. I increased it to 6.5 Ohm 3 watt resistor and the input tube plate voltage came out right and it's not overly glowing anymore. Tubelab was right all along. My bad.
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