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Old 8th October 2013, 02:03 PM   #1
Nikitas is offline Nikitas  Greece
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Default D3a preamp.

Has anybody tried this tube triode strapped as a differential preamp? What are your impressions?
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Old 8th October 2013, 02:19 PM   #2
ja2dhc is offline ja2dhc  Japan
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I've not used D3a as a differential amp with pentode connection.
I used it as a triode strapped conventional voltage amp.
That amp generates a lot of micro-phonic noise.

There is a famous amp to use D3a by Pete Millett named
E-Linear, refer to the below URL.

E-linear amplifier
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Old 8th October 2013, 02:28 PM   #3
Nikitas is offline Nikitas  Greece
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What do you think about it? How's the sound? Is it worth it?

Edit: Millett's version isn't what I have in mind.
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Old 8th October 2013, 04:35 PM   #4
kevinkr is offline kevinkr  United States
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I use them in one of my phono stages and as the drivers in my GM70 amp. (triode strapped)

I find them somewhat microphonic in phono stages, but generally not a big problem, and otherwise very quiet.

They are very linear. Pleased overall with their performance and durability.
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Old 8th October 2013, 04:54 PM   #5
Nikitas is offline Nikitas  Greece
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I'm thinking of using these right after my buffalo dac, which produces balanced output.
And I'm trying to avoid the use of transformers..
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Old 8th October 2013, 05:09 PM   #6
Nikitas is offline Nikitas  Greece
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this is the concept:

Point is, is it worth pursuing this concept, or is it more practical to find another (SS or opamp) solution for BallSE conversion and after it use something like a 5842 with a CCS?
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Old 8th October 2013, 05:18 PM   #7
kevinkr is offline kevinkr  United States
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I use Sowter I/V transformers and 5842 with a variation of the TPA COD pcbs..

Not sure with the Buffalo, but probably worth a try. Bias and level shifting arrangements will be needed for your output stage. How much gain do you need - is the D3A a good choice given its high mu?
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Old 8th October 2013, 06:48 PM   #8
Nikitas is offline Nikitas  Greece
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To be honest I am not sure. This is my very first attempt involving tubes.
I have some 6n1p,6v6,6sn7,6sl7 around, do you find any of these a better choice for the task?
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Old 8th October 2013, 07:43 PM   #9
kevinkr is offline kevinkr  United States
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Cannot answer the question, to even partially answer that question you need to figure out the signal level at the output of the buffalo dac, is the output current or voltage, and what your target output level is at FS or at some level lower than that typical of the bulk of your program material. High level voltage outputs make it simple, at most a little gain is required. Next comes noise and how much you can tolerate, this is a big issue if doing I/V conversion passively, for example the analog path in my dac limits resolution to about 15 bits due to the analog noise floor. (I can get another bit, but that's about it)
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Old 8th October 2013, 08:13 PM   #10
Nikitas is offline Nikitas  Greece
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Ok, let's see: the dac is current-output, giving approximately 16mA, 2V. About distortion, more zeros are always better,but I'm not going to witch hunt them. The power amplifier is an f5, a bit tweaked, something between v1 and v2 ang provides more than enough gain, so the preamp stage should be unity gain.
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