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
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
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)
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.
Wondering about topology and chosen operating point. I run D3A between 8 - 20mA depending on application with Vp 100 - 200V.
They were compared in a single stage common cathode RC coupled driver, CCS loaded, LED biased, between 8 and 14 mA, Vp 150-190v. Me and a musician friend found the E186F to sound better... and it has just enough swing to drive the GM70 to max power, but without any headroom, unfortunately.
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I did not use E186F but used 6688(E180F) triode strapped in place of
D3a (same pin-out).
6688 is better sound than D3a as well. My circuit is shown in the below URL
(sorry written in Japanese). Ip= about 10mA.
MOSFET SE Class-A
I use D3A with gyrator, choke, or IT, and generally run at highish currents. In the IT application I am running at 20mA, at about 180V. No solid state ccs or mosfets in the direct signal path. I find the sound beyond reproach and the measurements show excellent linearity. I do have a number of 6688 and will evaluate for future projects.
Could you post the schematic?
Since I'm running on a low budget, I'm leaning towards some 6v6 I already have, or maybe I'll try 6688 That I found cheap at ebay.
The 6688 seems like a reasonable choice and I assume you also have some D3A to play with?
I can perhaps post the schematic of the tube gyrator, it works and avoids sand in the signal path, but it is not quite as good as one implemented with mosfets obviously, and it is inefficient with plate voltage. It will get you close to mu, and has good psrr. Uses 5687..
What is the output voltage with the I/V resistors you are going to use?
I can perhaps post the schematic of the tube gyrator, it works and avoids sand in the signal path, but it is not quite as good as one implemented with mosfets obviously, and it is inefficient with plate voltage. It will get you close to mu, and has good psrr. Uses 5687..
What is the output voltage with the I/V resistors you are going to use?
Not much point in using tubes in since you are doing I/V with op-amps, it's an added complication to the signal path. Using resistors or transformers the tubes would make sense.
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