DNA (Donald North Audio) Headphone Amp

[Kees]

Single ended inputs, also for the balanced amp?

[spritzer]

It has a dual differential output via transformers but the rest of the amp is SE.

[Donald North]

Donald,

One other thing to consider, I see that you are using a JJ GZ34 for the rectifier. I have been told by multiple sources that there was a rather large batch of bad tubes produced last year that tend to arc and fail in a rather catastrophic manner. If you are running the rectifier very hard you might consider using another brand of rectifier. I had one of the bad JJ's in my personal headphone amplifier (which runs the rectifiers quite hard) and thankfully its failure didn't do any damage down stream.

Thanks for the heads up on the JJ rectifier tube. I'm running it conservatively in the Sonett so hopefully it won't fail prematurely.

I'm building for myself an 8 tube phono stage which will run the 5AR4 much harder - I'll do some bench tests on the JJ before putting it into the circuit.

[Donald North]

It has a dual differential output via transformers but the rest of the amp is SE.

Your understanding is correct.

[boomana]

I like the green jacks with the silver and blue.

[n_maher]

I like the green jacks with the silver and blue.

Yeah, but you're a girrrrrrrrrrrrrl.

[boomana]

It would look really nice with a silver source.

[Richter Di]

Hi Donald, will there be an European version available with 230 Volt?

How is the bias setting done when the tubes drift?

[Kees]

Hi Donald, will there be an European version available with 230 Volt?

How is the bias setting done when the tubes drift?

X2.

You just beat me to it.

[Donald North]

Thanks for your interest. Yes a 230V will be made but not immediately. It will require changing to different power transformers with multiple taps, which are physically larger and necessitate changes to their mounting pattern on the chassis. I investigated having the current power transformers custom wound for 230V, but the cost is prohibitive.

The 6H30 is biased in self-bias mode, running very conservatively. The tube should last many, many hours. When it sounds like it is time to replace, they're inexpensive, around $20-25 each.

[dcpoor]

There was so much to listen to at Canjam that I didn't get a chance to check this amp out.

It looks great though, very unique look.

[nikongod]

I took a moment to listen to this amp and chat with Donald North at the national meet.

The amp was quite nice. I didnt listen nearly as long as I would have liked, but it did quite well for detial and tonal balance with DT-880/250. The IEC output takes the DT-880 to a new level, and makes them a very strong point for price VS performance.

Chatting with DN was great, and I listened to a CD that I would not have otherwise thought to get. I didnt press him for the specs of his transformers, but still hold my previously stated guesses. We chatted about amps in general and he certainly knows his stuff!

[Hopstretch]

I'm very sorry I missed this. After briefly meeting Donald on Friday, I never ran into him again.

[Donald North]

Thanks guys, it was a pleasure meeting all of you as well. I always enjoying discussing music and hi-fi with fellow enthusiasts and am thrilled to see some younger faces. I love hi-fi and don't want it to die.

[Frihed89]

I took a moment to listen to this amp and chat with Donald North at the national meet....I didnt press him for the specs of his transformers, but still hold my previously stated guesses.

Somewhere (here?) I made a crack/asked a question about adding Double C-Core Silver Output Transformers. As I recall, DN suggested this would be possible upgrade.

Following that short "discssion", I have some questions for everyone:

1. Do you think a radical "improvement" in the output transformer would substantially improve the sonics?

2. I wonder if any existing Audio Note transformers or other components would fit, physically and electrically? (Try to restrain yourselves at the mention of the words "Audio Note". I am a hopeless true believer).

3. To the comment about 230V, aren't there any existing power transformers that would work? Again, AN makes a number and many (most? all?) have dual windings.

To Donald North, are you coming to RMAF2009? If you look on booking buddy or fare compare, etc., the prices of flights are low. I just booked a SW flight to SFO-Den for $69 and noticed that Frontier, AA and others had dropped their prices to compete.

I'd like to hear this amp, although I don't know about this "wonder tube".

Cheers.

[Donald North]

Hi Frihed,

Thanks for your questions:

1. Changing to Audio Note double C nickel cores with silver windings will definitely change the sound. Whether this is perceived as an improvement is subject. I personally like nickel & silver for hi-fi amplifiers.

2. The standard Audio Note transformers are different from my specifications. I'm investigating into having some prototypes made in copper first.

3. For 230V, I have to change both the B+ and filament transformers. There are multi-tap transformers available, however they have different mounting dimensions requiring changes in the chassis. I'm investigating it for future production.

4. Thanks for the suggestion about RMAF. I have not decided if I will be exhibiting or not.

Where do you live in Denmark? For summer vacation I normally travel to Europe to visit friends in Stockholm, Malmo, and Copenhagen. Perhaps we could meet up and you could hear the Supertube in person. Note: I didn't coin this name, but do like it

[luvdunhill]

Supertube in person. Note: I didn't coin this name, but do like it

I think Victor Khomenko first used the term for the 6H30P.

[spritzer]

I think Victor Khomenko first used the term for the 6H30P.

I believe you are correct. It's a shame it can't handle more voltage though...

[Hopstretch]

I believe you are correct. It's a shame it can't handle more voltage though...

Come on. Are you a member of Team Arcy-Sparky or a mouse?

[Frihed89]

Thanks for answering my questions. Incidentally, on Tuesday I am going to audition a used AN Miushu integrated.

Hi Frihed,....Where do you live in Denmark? For summer vacation I normally travel to Europe to visit friends in Stockholm, Malmo, and Copenhagen. Perhaps we could meet up and you could hear the Supertube in person. Note: I didn't coin this name, but do like it

I call it the Br

[darkless]

Donald, if you're going to stop by Copenhagen, please let me know as well. I live only 9.8 km away (16 min drive) from Frihed89.

[Frihed89]

Double Core UltraHiB silver output transfomers weigh about 8 kilos each! I just bought an AN amp that has two of them and weighs at least 40 kilos. I can't imagine sticking one of these beasts into head amp. Fortunately, I was joking...i think.

[Donald North]

Congrats on your purchase!

For a headphone amp I would go with a custom version of their preamp output transformers. It's plenty big for the function and fits on my chassis

[Frihed89]

Congrats on your purchase!

For a headphone amp I would go with a custom version of their preamp output transformers. It's plenty big for the function and fits on my chassis

What's the deal with the AN preamp transformer you put up for sale? Was that another project? What happened? That's a really wicked piece of iron for a preamp!

[Donald North]

I had those transformers designed and made for a phono preamp personal project. I was planning to use the 6AS7/6080 dual triode on the output. Recently I changed the design and will use different output tubes: 12B4. They require transformers of different specification, hence the sale listing of these.