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Old 16th April 2003, 03:10 AM   #1
arnoldc is offline arnoldc  Philippines
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Default A 76-6SN7 driven 300B

This is my second tube amp project, and also a success. Hum was around 3mV and it drives my Infinity Kappa 200 with ease. This amp I find has the weight and slam, but my 2A3 has more bite. They both sound good to my ears.

The OPTs are Hammond 125ESEs which were taken from my previous project, an SRPP 2A3 after that amp was upgraded to MagneQuest DS-025 OPTs.

The 125ESE continues to amaze me, at that price point it's unbeatable IME. I do have plans to upgrade them to Lundahl OPTs, maybe in a distant future or when the 125ESEs will be called for another duty.

The power transformer is a Lundahl LL1648 and has a Hammond 193J as choke.

The tube line-up is RCA VT76, GE 6SN7GTB, RCA 5U4G and a borrowed Electro Harmonix 300B (haven't decided on which 300B yet for myself, maybe you guys can recommend?)

The circuit was based on Joseph Esmilla's 300B DX with modified PSU using Duncan's PSUII designer.

I'm not good in woodworking and the base is kinda rough, I hope to get in touch with a furniture maker as i also lack decent tools for that.

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The wiring...
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Old 16th April 2003, 10:09 PM   #2
SHiFTY is offline SHiFTY  New Zealand
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Cool amp!

How are the 125ESE's handling the 100mA or so of the 300B?

I would have thought the core would saturate above it's rating of 80mA (or maybe that is a conservative rating)

Are you getting the full 8W of output, and how does it compare to the 2A3 in terms of volume?
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Old 17th April 2003, 03:23 AM   #3
arnoldc is offline arnoldc  Philippines
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Hi ShiFtY,

Knowing the 80mA limit of the 125ESE, i'm driving it at around 75mA configured for 5K.

I have not measured the power output yet but later today we will.

Ah volume.... hmm, both my DIY amps do not use a pre-amp and on the SRPP 2A3 my normal listening volume is 2 o'clock driving a pair of 89dB [in]efficient Infinity Kappa. On the 300B, my volume setting is 12 o'clock for the same loudness, but of course these amps have different driver configuration so it may be a factor.

OT: is it normal for a newbie's post to take a while before being posted in the forum?
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Old 17th April 2003, 09:54 AM   #4
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this is the deluxe JF lab 300b circuit.
But 76 isn't a direct heat triode.
If in power amp. tri 26, or my another choice 6C45/we437a.
I had enough confidence for use 6c45 to push 45/2a3/300b.
I use it to push 89db speaker/ Advance signature 8 to test for big drum. & chinese traditional music.
Its good for only one stage to cap cauple. between we437a/6c45 is a 45 magnification tube. we437a is used in the we microwave magnification.
Very low noise. But high current.
max can run 52ma, but sound detail.

I am still try we417a drive 45 tubes.
I am prepare to make it with a kit & in reasonable price.



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Old 17th April 2003, 01:45 PM   #5
arnoldc is offline arnoldc  Philippines
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hi thomas,

WE437A and 45 sounds good i have two Tamura F-475 that i can use for such project
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Old 18th April 2003, 07:20 AM   #6
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to arnoldc,

this several day I directly run in this amp & test the continous condition, stable or not for the coming kit over 30 hours.
( Transformer couple 300B/2a3/45 amp)
I still use 6C45/we437a Single triode to driver the Tango NC 16 to drive 300b with James Choke & output.
I also keep this in a very reasonable price. But I must make sure it will very stable to make the user not disappointed.
pls see the photos.
I reference this circuit & only a littler change it then more reasonable price The sound is much better than my friend's audionote amp.
I really satify.
I use La scala & lowther speaker to test it.
High frequency also very low noise.
Sound also good. As I think, the diy spirit is -Simple is the best. .

this circuit. http://www.tubebuilder.com/images/s.../we300b_se4.gif


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