As spin-off of thread below I build a unbalanced tube input board for my hybrid purifi modules as mentioned in the thread below.
https://www.diyaudio.com/community/...urifi-1et400a-amps.379211/page-3#post-7027789
Picture from Jasper84
I made a PCB for the unbalanced version, a 6n6p tube with mu-follower topology.
The preamp has a gain of 9 times and no problems to drive the 2k2 input impedance of the 1et400a modules.
Timing circuit around Q1 has a 13 seconds delay. This gives the tubes time to heat up without getting a big thump and shutdown the amp modules without strange noises.
Led D2/3 is on the “amp on” signal and can be mounted in a B9A socket with a hole in the middle. Tube bottom will light up when amp is on.
Combined this input board with 2 x 1et400a Purifi amp and Hypex smps1200a400 and smps 265v/6.3V then you get amp in picture below.
This amp is a pleasure to listen to.
https://www.diyaudio.com/community/...urifi-1et400a-amps.379211/page-3#post-7027789
Picture from Jasper84
I made a PCB for the unbalanced version, a 6n6p tube with mu-follower topology.
The preamp has a gain of 9 times and no problems to drive the 2k2 input impedance of the 1et400a modules.
Timing circuit around Q1 has a 13 seconds delay. This gives the tubes time to heat up without getting a big thump and shutdown the amp modules without strange noises.
Led D2/3 is on the “amp on” signal and can be mounted in a B9A socket with a hole in the middle. Tube bottom will light up when amp is on.
Combined this input board with 2 x 1et400a Purifi amp and Hypex smps1200a400 and smps 265v/6.3V then you get amp in picture below.
This amp is a pleasure to listen to.
Last edited:
Hi Monstercore,
Thanks for sharing your build! It looks great!
I’m still deciding whether to go with a balanced or single-ended input for my Purifi 1et400a amp. My current DAC has differential outputs, and I’m also considering getting a streamer with XLR out. So balanced would make sense, but it also adds a bit more complexity to the build.
From your experience — do you think it’s worth going fully balanced in this case, or is RCA more than enough for a home setup?
Appreciate your thoughts, and thanks again for posting your project.
Thanks for sharing your build! It looks great!
I’m still deciding whether to go with a balanced or single-ended input for my Purifi 1et400a amp. My current DAC has differential outputs, and I’m also considering getting a streamer with XLR out. So balanced would make sense, but it also adds a bit more complexity to the build.
From your experience — do you think it’s worth going fully balanced in this case, or is RCA more than enough for a home setup?
Appreciate your thoughts, and thanks again for posting your project.
Hello Vavilen,
I used and tested balanced and unbalanced. When you go for the tube input preamp, I could not hear any difference. So unbalanced is the way to go.
But when you have all balanced equipment with 6 to 10Vrms output signal , you can omit the complete input preamp.
This sounded for me the best. See Input PCB below for Purifi or ncore.
https://www.diyaudio.com/community/...urifi-1et400a-amps.379211/page-8#post-7254111
I used and tested balanced and unbalanced. When you go for the tube input preamp, I could not hear any difference. So unbalanced is the way to go.
But when you have all balanced equipment with 6 to 10Vrms output signal , you can omit the complete input preamp.
This sounded for me the best. See Input PCB below for Purifi or ncore.
https://www.diyaudio.com/community/...urifi-1et400a-amps.379211/page-8#post-7254111
Last edited:
You can jumper-set the input sensitivity for the Purifi to work with whatever source you have.
I agree that balanced directly into the Purifi is best.
Jan
I agree that balanced directly into the Purifi is best.
Jan
I’m currently using a Wiim Pro Plus with unbalanced 2Vrms output. With a balanced input buffer from Neurochrome connected in unbalanced way, the sound isn’t loud enough even near max volume — highs feel dry and sharp, and bass is lacking.
I’ve decided to try a lamp buffer, because I had experience with an AD1862 DAC, and for me it sounded more natural and pleasant than Delta-Sigma DACs. So I’m curious to see if lamp buffer makes Purifi amp sounding a bit warmer.
I’ve decided to try a lamp buffer, because I had experience with an AD1862 DAC, and for me it sounded more natural and pleasant than Delta-Sigma DACs. So I’m curious to see if lamp buffer makes Purifi amp sounding a bit warmer.
Two different things, tonal deviation and level.
As I mentioned, you can set some jumpers on the Purifi to fix the level.
The tonal issues sound to me like a too small coupling cap.
But hard to say unless you piost a schematic. No idea what the different DACs have to do with the issue you now have.
If another DAC fixes it for you, why tha lamp buffer?
Jan
As I mentioned, you can set some jumpers on the Purifi to fix the level.
The tonal issues sound to me like a too small coupling cap.
But hard to say unless you piost a schematic. No idea what the different DACs have to do with the issue you now have.
If another DAC fixes it for you, why tha lamp buffer?
Jan
