• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

EDCOR Output transformer for 300B

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#23
Gee, I'm bummed. My in-laws lived about 3 blocks from the Jian Shin (James) store/office. I've walked past it half a dozen times without a clue about what was inside. Now, the in-laws have moved 20 km away to a completely different area. So no chance of sneaking in any impulse buying while out for a stroll anymore.

no. 11, LANE 113, SAnMIN road, Taipei City, Taiwan - Google Maps

Oh, if anyone else is trying to find them on Google maps, the street name is spelled differently on the James website. Google calls it San Min Rd., Jian Shin calls it Sam Min Rd.

..Todd
 
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#27
tomchr said:
If you don't want sand in your glass, I'd look at the 300B DRD from ElectraPrint. I love that design for its simplicity. I would love to build one, though, I'd like to find a different solution for the choke and 50 W rheostat required.
Click to expand...

I have built several of these DRD amps and I am truly happy with the direct and transparent sound. I am also happy with Jack's chokes which are about $100 a pair if I recall correctly. The big adjustable resistor is not necessary at all. I compute the current flow and voltages using ohms law and then use two 25W fixed resistors. If the operating points are not quite what I like I substitute a different resistor. You only need to experiment with the first amp; the second one will be a copy of the first.
 
#28
Palustris said:
I have built several of these DRD amps and I am truly happy with the direct and transparent sound. I am also happy with Jack's chokes which are about $100 a pair if I recall correctly. The big adjustable resistor is not necessary at all. I compute the current flow and voltages using ohms law and then use two 25W fixed resistors. If the operating points are not quite what I like I substitute a different resistor. You only need to experiment with the first amp; the second one will be a copy of the first.
Click to expand...

I wonder what this circuit (DRD amps) would sound like with an 845 and 5K OPT.

Sorry off topic!


Regards
M. Gregg
 
#30
M Gregg said:
I wonder what this circuit (DRD amps) would sound like with an 845 and 5K OPT.
Click to expand...

Probably Gawdawful. 5K is about half the suggested load (9K -- 10K) for the 845. This type likes to operate at high voltages and low currents in order to really bring out the sonic performance.

Of course, for that particular topology, you'd need to really go for the bigvolts if implemented with an 845.
 
#31
Miles Prower said:
Probably Gawdawful. 5K is about half the suggested load (9K -- 10K) for the 845. This type likes to operate at high voltages and low currents in order to really bring out the sonic performance.

Of course, for that particular topology, you'd need to really go for the bigvolts if implemented with an 845.
Click to expand...

Just for interest,

ELNA audio Capacitor

[FONT=Arial,Helvetica][SIZE=-1]6135HSF[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]80mA[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]5k[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]30W[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]18Hz~50KHz-2dB[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]211/845[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]D[/SIZE][/FONT][FONT=Arial,Helvetica][SIZE=-1]5.2[/SIZE][/FONT]

I think I saw a write up were the 845 could be used at higher current / lower volts, where the 211 could not. I will try and find the info.

Regards
M. Gregg
 
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#32
Just for interest,

The operating points for an 845 when used to substitute a "50" were shown at :

B+ 500v this is lower than that on the DRD circuit.

Plate current = 88mA

Bias supply -50

Heater 10v 3.5A

Load resistance = 765v / 250 mA =3060 Ohms

Power out shown at 4.76W / 8 Ohms.

This was an article in Sound Practices by J.C. morrison, nyc.

Sorry for the off topic! Back to 300B🙂

Regards
M. Gregg
 
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