MHDT Orchid or Lampizator Amber 3?

Do they support 6SN7 tubes with the proper adapter (Garage1217)?

In all our dacs, tube is acting as a buffer.
So, the tube is a passive compnents in circuit and so a fixed set up (bias). No needs to adjust resistors’ value for most tube.

However, the tube is working on -17.5 to + 17.5 volts, quite a very low voltage in tube’s world.
5670 can works on this low voltage because 5670 was design and developed for minitary communication equipment during WWII. So, it can be work on hardest enviorment such as low battery source and hard vibration. All pencil tubes were designed to be used in air plane, they also have same characteristics like 5670. 6SN7 is a commercial tube, it may also works on our dac but sound must be another issue.

Best Regards,
Jiun
Mhdt Lab

Subjective/anecdotal impressions would suggest that 6SN7 tubes do indeed work.

I didn't realize you got the A OK from Jiun!
Thanks.
I did notice in the specs that the gain from the 6SN7 tube is lower than the 396A; maybe not quite enough to be noticeable, and, maybe as a buffer, gain is not an issue anyway.
Will be interesting to hear what your findings are.
This is indeed one helluva great sounding dac with grannyrings mods and the SR Orange fuse. Yes, I admit it, I am a grannyring 'fan boy'. 

My experience with 6sn7 tubes in preamps has proven the Psvane T-series black bottle tubes (cv181) sounds as good, and in most cases,  better than the myriad of well touted NOS 6sn7 tubes.

Only problem is these cv181 tubes don’t seem to last as long.

Can someone send me a link to the adapter I would need to roll a cV 181 (6 SN7) for the ORCHID. Also with this adapter/riser in place do you still need to enlarge the thru hole of the top plate?

2nd from bottom:
http://www.garage1217.com/garage1217_diy_tube_headphone_amplifiers_012.htm

Same place on eBay: https://www.ebay.com/itm/GARAGE1217-6SN7-TO-5670-396A-TUBE-SOCKET-ADAPTER-OUTSTANDING-BUILD-QUALITY/...

I have both CV-181Z and 6SN7, but I will run *6SN7* FIRST, to be sure things are smooth and steady.

Hole needs to be enlarged like I mentioned (7 posts above) for 6SN7 or run topless till you decide.
The hole would need to be larger yet for CV-181 obviously, if I do that, I’m machining it properly.

The E88CC, 6922, 6DJ8 family will poke through the stock size hole about a half inch or so above plate.