• 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.

#26 pre amp

I think it would be worth trying the ES9018 connected directly to the 26.

Yes, it has to be unbalanced - but I doubt that this would degrade the sound as much as a 6SN7 does.

The ES9018 drives a metre of cable perfectly well, directly from the DAC output.
Properly-implemented current-out mode can work better - but the proof is in the listening.
 
Hi Rod,
I am running it in current output mode. I will run it directly into the 26 unbalanced see how it works.

If I use 10k volume control I have at hand on the 26, I am not sure if this would be too heavy of a load for the ES9018 chip to drive. It seems that I should use a higher value pot?

Thanks
 
Hi Andy and Juanitox;

I will first bypass the 6sn7 stage and run the DAC into the 26 unbalanced. If this does not work to my expectation, I will use line transformer. I have a MegneQuest 10k:500 might be a good fit for this task. 500 into a 10k load(if I use 10k volume pot on the 26), would this impost a heavy load for the source side?

Thanks,
 
ES9018 in stereo mode shows about 195 ohm output impedance, and it works well into 10K.

But the ES9018 DSP volume control has plenty of guard-bits, and works even better (so long as your system-gain is about right - not too high) , and operates without loss of data. Listening-position volume control is more than just convenience, too!
 
Hey, I built a Buffalo III SE into my 26-based preamp to make it a 26 tube output DAC plus full-function preamp. I wrote up the build, with pictures over at Computer Audiophile.

Here's a link:

Building a Buffalo IIIse/Sonore USB/Tube Output DAC

It sounds fantastic. I run the DAC output into a Lundahl LL1676 which sums the outputs, removes the DC offset from the DAC, steps down the voltage by 1/2, filters high frequency digital crud from the DAC, and allows me to apply the 26 grid bias to the secondary. Works like a charm.
 
PS: If you put the volume control on the output of the preamp you don't need to worry about it in the input circuit. I much prefer it that way; an autoformer or transformer volume control can even double as your output transformer.

I wouldn't do it any other way now that I've experienced it, beats any volume pot I've ever heard.
 
Thanks for the link. You have a really nice preamp. My Buffalo is the older version II built several years ago.

Now I have a better idea how to build my new toy. This is what I have in mind, what do you experts think? Go or no go?

Buffalo DAC balanced output into 10k:10k line transformer. The secondary connects to the grid/ground of the 26. a 10K volume pot is connected parallel to the secondary in shunt mode.
 
I now have enough parts to lay out, and the size of the two boxes is set (I have a large flight case into which they must fit). This is the PSU box. And the raw filament supply components will all go underneath. The top plate is 5mm marine grade alloy, (so that will be fun to cut and drill!) with 18mm birch ply sides, veneered.
I have a 123 x 123mm steel transformer cover on the way, so I was hoping to put the choke in there with the transformer. But how close can I position the 157G choke to the mains transformer?
I could put it somewhere else, underneath, but would prefer to put it on the top. Is this too close? Would it help to offset them? I could even mount the choke vertically on a bracket under the cover.
20160406_123751_zps7qzanmyv.jpg
20160406_123942_zpsic7hpyvu.jpg

BTW, I will mount the caps the right way up! :)
 
Hey, I built a Buffalo III SE into my 26-based preamp to make it a 26 tube output DAC plus full-function preamp. I wrote up the build, with pictures over at Computer Audiophile.

Here's a link:

Building a Buffalo IIIse/Sonore USB/Tube Output DAC

It sounds fantastic. I run the DAC output into a Lundahl LL1676 which sums the outputs, removes the DC offset from the DAC, steps down the voltage by 1/2, filters high frequency digital crud from the DAC, and allows me to apply the 26 grid bias to the secondary. Works like a charm.

Hi Magz,
I've always thought about a project like this, but I'd like to use the 45 instead of 26. I'm more than happy with this tube after using it in my latest line stage.
Well, whether it is the 26 or the 45, I'm considering about the real difference between the tube stage and the IVY, with the latest to be proven to have its own merit.
 
Hi Magz,
I've always thought about a project like this, but I'd like to use the 45 instead of 26. I'm more than happy with this tube after using it in my latest line stage.
Well, whether it is the 26 or the 45, I'm considering about the real difference between the tube stage and the IVY, with the latest to be proven to have its own merit.

Hi Alkis, I'm sure the IVY is a very nice output stage for the Buffalo, and the advantage is it was designed specifically for that DAC; I haven't heard it so I can't comment on any differences there may be between it and a tube output.

However, my choice was to merge the DAC and preamp together and eliminate the need to have a DAC output stage in addition to the preamp stage. I already had the preamp and by a stroke of luck when I built it I left enough room for the DAC to fit (mostly because of the fixed width of the front LED display panel, not because of any brilliant forethought by me!).

I love the sound of this combination, and I'm sure I'll be very happy with it for a long time. As far as your project with a 45, I say go for it! You'll never know unless you try it...
 
Hi Alkis, I'm sure the IVY is a very nice output stage for the Buffalo, and the advantage is it was designed specifically for that DAC; I haven't heard it so I can't comment on any differences there may be between it and a tube output.

However, my choice was to merge the DAC and preamp together and eliminate the need to have a DAC output stage in addition to the preamp stage. I already had the preamp and by a stroke of luck when I built it I left enough room for the DAC to fit (mostly because of the fixed width of the front LED display panel, not because of any brilliant forethought by me!).

I love the sound of this combination, and I'm sure I'll be very happy with it for a long time. As far as your project with a 45, I say go for it! You'll never know unless you try it...

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