[EricGC]

I sent an email to Mhdt (replies below). Seems that they have not tried 6922 in their DACs.
 
==============
 
Hi,
 
The tube buffer stage of 5670 which used in our DACs are supplied with -17 ~ +17V.
This is a very low voltage condition and that's why we choose 5670.
 
6922 is also a tube used in military communication during the world war II, so it can be used in this condition.  But usually 6922 tube need higher voltage so the results.. hmmm I don't know.
 
Other high voltage tube like 12AX7..AU7 .. etcs will be not recommended.
 
If you try to use 6922, you need a adapter since the pins alignment are different to each other.
 
Best Regards,
Jiun
Mhdt Labs

 

[213Cobra]

Jiun is of course right about the 12XXX series not being suitable, even if you had an adapter. The heater voltage is wrong, and the plate voltage requirement is much higher. But there is precedent for the 6dj8/6922 family being used with very low operating voltages, so I was willing to try it. Thus far, the results via adapter are sonically excellent. More notes coming.
 
Phil

 

[slex]

My adapter came yesterday and blonk it into the paradisea 3 with a Genalex Gold Lion ecc88. Results are promising. Almost comparable with my Bendix 2cc51 with bit of wider soundstaging but tad less details.

Will let it burn in for a week and see the final result.

 

[EricGC]

These two tubes are about same price right (Genalex Gold Lion ecc88 & Bendix 2c51)? So... what's the point of getting adaptor?  

 

[slex]

These two tubes are about same price right (Genalex Gold Lion ecc88 & Bendix 2c51)? So... what's the point of getting adaptor?  

Price doesnt matter. Im on the quest for improvement.

 

[213Cobra]

On a quick listen of the adapter/CCa combination in my Havana Balanced, I noticed that the CCa/6922 advantage over the better examples of 5670 family was diminished. I didn't explore it further at the time because I was focused on getting my Pagoda and Atlantis sounding right. So I've complicated my listening mission by putting adapters and CCa tubes in the Havana Balanced for equally attentive evaluation alongside the Atlantis, Pagoda, Pagoda Balanced comparisons I am running now.
 
Will report back. It may be that since in Havana, the current/voltage conversion is performed in the PCM56, the buffer tube selection differences are truncated somewhat, compared to the higher resolution discrete solid state output sections of the 24 bit R2R Pagoda and 20 bit Atlantis.
 
Phil

 

[EricGC]

According to Luckbad's review, rolling tubes has more influence to Altantis than Pagoda. I don't have an Altantis to compare, but I feel different tubes still make very noticeable change to Pagoda's sound.

 

[213Cobra]

My experience with these is different. Atlantis and Pagoda are equally affected by sonic differences in tube-rolling, though the ideal tube may be different in each. My point above is that tube rolling in Havana, while quite fruitful within the 5670-compatible range, showed less advantage to the adapter/6922 change than it does with Pagoda and Atlantis.
 
More to come.
 
Phil

 

[lordcloud]

Just wanted to say thanks for an awesome thread. I'm seriously considering a balanced Pagoda, And this thread had been great!

 

[ericr]

Welcome to Head-Fi!

 

[ericr]

Oh, and as they say here:

Sorry about your wallet!

 

[EricGC]

MHDT customer service is just superb. They replied my email within minutes, and really back up their products.
 
Last week I had some problem with left channel on my Pagoda, after exchanging several emails with Jiun, he helped me identify the issue, and sent me a new board within a week!  Thumbs up!
 
I have done quite intensive research before I bought Pagoda. For some very popular brands (schiit for example), there are always many people like them, and some (more or less) dislike them. But for MHDT DAC, I have not seen a single negative review so far. Amazing sound quality!

 

[s1rrah]

  I have not seen a single negative review so far. 

^^^^^this.

 

[lordcloud]

I'm this close to ordering a balanced Pagoda. It's tough to order one new though. But I've yet to see a used balanced Pagoda.

And yeah, the reviews have all sounded great! T

 

[lordcloud]

Then one day wandering around eBay I happened upon sources for tube socket converters. Prowling that list, I found a source in China for ecc88/e88cc/6922 > 6n3p/5670 converters. This would allow running 6922/cv2492/CCa dual triodes in mhdt DACs. No brainer to order some. First up, the Pagoda single-ended. Out with the Bendix and in with the converters plus NOS Mullard CV2492. It was an idea to try; I had no particular expectations. I wouldn't have been surprised to have this be a step backward.

But no. It's sensational! Current draw is similar to the 5670, so this isn't a strain on the power transformer. I assume mhdt's decision to select the 5670 family was driven by the facts that they are cheap, plentiful and very good, and the extended family of substitution tubes is extensive. Nevertheless, go converters + premium 6922 family and I think you'll be seriously startled by the gains in dynamics, musicality, tone density, transient life and an especially notable extension of deep bass response from Pagoda and Atlantis. I also hear a more fully dimensioned soundstage, including depthwise. Overall a more spatially scalable sound where it's appropriate.

All of my inventory of 6922 family tubes is comprised of premium NOS. Siemens, Siemens-Halske, Amperex PQ, Mullard, Telefunken, Valvo CCa, CV2493, e88cc, etc. I settled on Mullard CV2492 in Atlantis, Siemens CCa in Pagoda, CV2492 in Pagoda Balanced. The differences between these premium tubes are discernible but not gaping. Running a step down Siemens e88cc or Amperex PQ 6922 is still going to be completely in the realm. I don't have any cheap and current production 6922 family tubes, but will get some and report back. The tube socket converters run something like eight bucks. If current production tubes yield same or similar effects, then this can be a very inexpensive sonic improvement.

The differences aren't subtle. I will stick with this combination for a few weeks and see if it sticks. In a separate post I'll get into the differences between Atlantis and Pagoda.

Phil

Phil,

I've just ordered the converter, and I'm now looking at what tubes will sound best.

In your opinion, and with your additional listening done on the balanced Pagoda, what tubes would you recommend?

And thanks for a great write up.

Henri