The LL1660s in 4.5:1 did not work out as I had hoped.
The LL1674 8:1 is much more to my liking. Without further ado. Here is the schematic.
dac_output 6n6p parafeed ccs ll1674 lundahl
Believe it or not I had quite a problem wiring these things up for 8:1 duty. To make it easier for you I’ve drawn up an application note.
This note describes wiring up a Lundahl LL1674 with a 8:1 ratio. As I did for my 6N6P DAC output stage. CCS a cascaded version with a IXYS IXTP01N100D top and DN2450N3 bottom.
Wiring a Lundahl LL1674 8:1
And as a power amplifier. I.e. no volume control. And a switch to choose between SE or balanced.
Also without the added global feedback.
Still one of the better references on the net. An excellent primer.
Navy Electricity and Electronics Training Series
Module 6—Introduction to Electronic Emission, Tubes, and Power Supplies
For my hobby room I decided to get the RAKK USB2SPDIF thingy to feed my RAKK DAC MK1. (In my living room I use the Squeezebox 3 and RAKK MK2.)
The thing I liked about it was that it does not use the computer’s supply. Furthermore it has ample linear regulators onboard. I counted four LD33′s and one LD50.
The usb dac is PCM 2707. And it looks like there is a crystal onboard as well.
Used a wallwart linear psu from a router I bricked. Added a L78S12 since the wallwart put out 16VDC unloaded. And then a 10000uF Kendeil for good measure.
Put it in a cheap wooden box et voila.
I just kept missing oomph. With the passive output stage that is.
So first I took away the 1.8k resistor I had in there. And replaced it with a 47 Ohm resistor. And added an SRPP 6N6P gain stage. Got what I wanted in terms of “speed”. But not entirely happy with the sound. It sounded a bit artificial. So I took away one 6N6P. And added my Maqnequest MQ EXO-001 plate chokes. And upped the B+.
Bingo!!!!! Now it also sounded like music. It sounded so much more true to life. Amazing. There is no comparison. The Choke loaded 6N6P stage wipes the floor with the previous SRPP stage. To be honest. I also upped the B+ which in turn increased the current running through the tube from about 11mA to 14,5mA. Which happens to be a sweet spot for the 6N6P according to Dave Davenport. (Who happens to be the designer of the RAKK)
Schematic without the PSU:
6N6P MQ EXO-01 loaded output stage after my passive I/V
I must also admit that the AudioNote DAC 2.1 was what finally gave me the kick in my behind to actually try it instead of constantly thinking about it:
http://www.audionotekits.com/_images/1xoverDACKit2_1_IVDiag1.jpg
http://www.diyaudio.com/wiki/Simplistic_Mosfet_HV_Shunt_reg_PCB_Instructions
A work in progress.
dvb-projekt’s pcb
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