Little Dot I+ Headphone Amp Impressions

[1octave]

Originally Posted by Mr. Lin

Thank you Jim, I've put a lot of work into the cables I make.

Ok, here's the update for the evening. First of all, as requested, I've taken some pictures. For those not familiar with the I+, the op-amp that's "rolled" is in the center of the circuit surrounded by four capacitors. The little thing in my hand in the other picture is one of the shunts, or jumpers, used to make the I+ compatible with various families of tubes. And finally, a picture of the Telefunken tubes I tried tonight, because many of us love to look at and handle tubes.

I spent quite a few hours listening to the I+ tonight. After a couple hours I switched from the stock (upgrade) WE408A tubes to the CV4010 Telefunkens. My one complaint about the I+ so far is that it's sort of a pain to take a apart, at least mine is. The holes in the bottom half of the chassis don't line up perfectly with the rest of it, which makes it difficult to get the screws back in when you're done. It's also a little tougher than I thought to safely remove an op-amp, and even more difficult to put one back in the socket. Overall, perhaps I'm exaggerating, and I'll survive, in any case..

To be honest I'm not sure if I hear as big a difference between the tube types as I did with the op-amps. There was a difference though - the Telefunkens sounded "bigger," with a wider soundstage, and perhaps a tad more lush than the WE408A. I could be imagining this, but it seems there's a little less dynamic impact now. Because the Telefunkens and the Mullards I have are from the same family of tubes, I was able to quickly install the Mullards a little while ago. Again, no dramatic changes, still a wide, three-dimensional sound like the Telefunkens, a little warm and very smooth.

They both sound good, but I'm reserving any final judgments as these really need to be left on the Frybaby for a while to break in. I think I'll start with the Mullard since it's already in there. Jim was kind enough to sell me a pair of Tung Sol 408's, those should be here soon and they're supposed to be quite good.

I'm really enjoying the I+. It sounds much better now than it did out of the box - and even then it sounded nice. For the money its performance is very impressive.

Really impressive Mr. Lin.!!! You seem to be a pro in this...

[Mr. Lin]

Nope, just OCD, but thanks!

[Mr. Lin]

Today I tried my first pentode tube from the EF91/EF92 family, the third "tube family" that's compatible with the I+. These are something different than the other two families of tubes I've been using, they're taller, for one thing, and inside the guts appear wrapped in metal, as you can see in the pictures. The brand is Mullard, they're NOS.

When I fired them up for the first time there was noise in the right channel, and I was worried one of the tubes was bad, so I turned it off and switched them to make sure. The noise disappeared. Not sure what that was about. Right away I noticed there's more bass with these.

It sounds great, but I must also attribute this at least partly to the LT1028 I put in there last night, which is 2x single-circuit SOIC. Interestingly, these op-amps sounded harsh and thin last night. I put them on the Frybaby for about five hours, and when I listened tonight there was a huge difference, the sound is much better than the National Semiconductor LME49720 I had in there before. Fuller midrange, more detail, more accurate sounding.

Regarding tubes again, I used the Sylvania gold pin 6028s for a few days, then switched to the Tung Sol 6028. Compared to the Tung Sol, the Sylvania sounds a little too aggressive and a tad bright. With the Tung Sol the sound was smoother and more balanced. Definitely prefer the Tung Sol at this point - thanks again Jim!

[Mr. Lin]

Got these 6N1P tubes (compatible with 6AK5) from a seller in Bulgaria for a low price and I'm very happy with them. Plus they come in neat boxes! The sound is smooth, full midrange and bass, very nice. Not the sound I expected from a Russian tube, but that's probably because this is the only NOS Russian tube I've ever heard, and I usually equate Russia with new production tubes.

A friend who speaks Russian tells me the one side says "Radiolampa," and the side you can see in the picture is PCCP, which is Cyrillic, and stands for Soviet Union.

[Mr. Lin]

These arrived today from Denmark, they're NOS Valvo EF91 tubes, originally produced in Hamburg, Germany. I paid $30 for a set of four.

Going from the Russian tubes to these I hear a fuller midrange. These are a little more "tubey" sounding than some of the others, with excellent imaging and tonal richness. Another winner!

[ehoove]

Glad to see your having a blast! Those Valvo tubes are interesting. How do you like the EF91 flavor output wise?
Regards,
Jim

[Mr. Lin]

Originally Posted by ehoove

Glad to see your having a blast! Those Valvo tubes are interesting. How do you like the EF91 flavor output wise?
Regards,
Jim

Output-wise they don't sound too much different than the others. Maybe a little louder, or perhaps that's just the CD I'm listening to tonight (re-master of XTCs' "Mummer"). I also have the Mullard 4015, which belongs in the EF91 family as well - I think I forgot to mention that one - but I haven't had enough time with it to judge it's performance.

The Valvos, however, I really like.