Little Dot I+ Headphone Amp Impressions

[Mr. Lin]

Hey Mr. Lin, not to wander off, but when you have the chance, maybe in another thread could you give us a run down on your interconnect design.

Thanks!

Well it's sort of a work in progress. The pair pictured is fairly simple, just three solid silver conductors. The positive is OCC silver with a cotton dielectric. Everything is covered in Teflon. Connectors are the Eichmann Silver Bullet. This was sort of a one time thing since it was so expensive to make, I just wanted to try this design out and use nothing but silver throughout, since usually at least the RCA connectors are a brass alloy, sometimes copper. I'm working on something similar now that's more cost effective, but it's definitely nice to have a pair of this caliber lying around, and to buy something equivalent from a major manufacturer would probably cost a fortune.

Mr. Lin, excellent work! I'm curious about where you sourced the Brown Dog adapters from-- they look top-rate!

Go to the Cimarron Technology website - I guess that's the company behind Brown Dog. They also offer pre-assembled components, so the op-amp is already mounted in case you have really shaky hands or something. Actually, I admit I don't have the steadiest hands in the world, but I made my life easier by watching the tutorial they link to at the bottom of the home page. The Surface Mount Soldering Techniques lesson demonstrates how to solder a little SOIC chip to a board. If you know how to solder, much of it won't be new to you, but he has a few tips that really did help.

 

[ehoove]

Which one, the CV4010 or the 6AK5 with the larger shield on it?

The CV4010
Regards,
Jim

 

[Mr. Lin]

The CV4010
Regards,
Jim

Ever tried anything from the EF91/EF92 family yet Jim? I'm curious about these because it seems to be a very different tube. I have a set of Valvo EF91s coming from Bulgaria, but I'm confused about the directions for placing the shunts inside so the I+ works with this tube family. It says to place jumper caps onto J1 and J2, but where do those caps come from? I guess I'll have to e-mail David again.

 

[TerryS]

Ever tried anything from the EF91/EF92 family yet Jim? I'm curious about these because it seems to be a very different tube. I have a set of Valvo EF91s coming from Bulgaria, but I'm confused about the directions for placing the shunts inside so the I+ works with this tube family. It says to place jumper caps onto J1 and J2, but where do those caps come from? I guess I'll have to e-mail David again.

Spare jumpers came in the bag with the headphone adapter cable with my LD-1+.
Terry

 

[Mr. Lin]

Spare jumpers came in the bag with the headphone adapter cable with my LD-1+.
Terry

Found them, thanks! I'm not going to use the cables that came with the I+, so I just put them away. The bag the cables are in looks like something you'd buy at Radioshack, that's why I didn't expect there to be anything else in it. Kind of strange that they were in there.

 

[1octave]

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]

More entertainment...

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]

Another tube flavor:

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]

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.

 

[Mr. Lin]

And you thought this thread was buried...

Couple new tubes to add, both NOS, both EF95. One pair is Valvo, the other Amperex Orange Globe and were made in the US.

Both are excellent. The Valvos have a little more bass, and they're also a bit dark. The Amperexs on the other hand give excellent upper frequency detail and clarity. Between the two I think the Amperex is probably better, but compared to all the other tubes I've amassed, these are among the best.

 

[john57]

I just received my Little Dot LD 1+ and I am very impressed by it when I changed the standard Chinese 6JI tube to the WE408A tube and the difference with the tubes were extreme in my case. The 408A tube was much smoother that the 6JI tube. I had no problem taking the bottom half off the change the jumper and put it back together to use the 408A family of tubes and I have decided to stay with that family. I The Little Dot LD 1+ is one of the best bang for the buck I received in a long time for audio equipment.

 

[Mr. Lin]

I just received my Little Dot LD 1+ and I am very impressed by it when I changed the standard Chinese 6JI tube to the WE408A tube and the difference with the tubes were extreme in my case. The 408A tube was much smoother that the 6JI tube. I had no problem taking the bottom half off the change the jumper and put it back together to use the 408A family of tubes and I have decided to stay with that family. I The Little Dot LD 1+ is one of the best bang for the buck I received in a long time for audio equipment.

Agreed John, just one thing I strongly recommend: change that op-amp it comes with. No need to go crazy with it like I have, maybe take a look through my thread or the one over at headfi to see what's recommended. The 2107 comes immediately to mind, but there's a ton of op-amps out there for very little money that will give your I+ the little push it needs in the right direction. Generally I've found op-amps to have a greater than or equal effect on the sound quality as tubes. Up until you get to the best op-amps, that is - then there's little difference between them.

 

[john57]

To tell you the truth I got a bit lost reading all the op-amp rolling threads. If I understand correctly the OPA2107 is a direct replacement for MC33078 that is in the Little Dot? What exactly is the improvement that I may get? I have all the tools to work on circuit boards as needed. I am not going to get very involved in op-amp rolling since I wanted to be content and happy in what I have. There was a period in my life that my hearing was failing and my first surgery attempt failed and the second attempt was a triumphal success. To be able to hear difference in sound that was greater than the ability I was born with. Anyway that is a long story. I just thrilled to be able to hear the difference in the tubes and I decided bring out my last remaining NIB Stax headphone out of storage and put in service with my main rig with the Melos.

 

[Mr. Lin]

To tell you the truth I got a bit lost reading all the op-amp rolling threads. If I understand correctly the OPA2107 is a direct replacement for MC33078 that is in the Little Dot? What exactly is the improvement that I may get? I have all the tools to work on circuit boards as needed. I am not going to get very involved in op-amp rolling since I wanted to be content and happy in what I have. There was a period in my life that my hearing was failing and my first surgery attempt failed and the second attempt was a triumphal success. To be able to hear difference in sound that was greater than the ability I was born with. Anyway that is a long story. I just thrilled to be able to hear the difference in the tubes and I decided bring out my last remaining NIB Stax headphone out of storage and put in service with my main rig with the Melos.

To my ears, the difference is relatively small, but quite significant, if you know what I mean. That's why I recommend doing it. I think I described it somewhere in the beginning of this thread, everything got faster sounding (transient attack), and resolution was enhanced, as were dynamics. All these things add up.

Again, no need to go crazy, maybe just get one of the highly recommended ones and be done with it. You won't need to do much work, the op-amp is in a socket so you just pull it out and replace it.

Yes, the 2107 is a drop-in replacement. You just need a "dual" op-amp, or one that has two circuits (sometimes it says "channels" in the specs). You may have to go to ebay to get some of the recommended ones, but they're still cheap. There's at least one seller on there now that I've bought most of mine from, and he hasn't let me down yet.

 

[roggom]

Mr Lin, are you sourcing the opamps from one vendor? I would like to roll some, just hard to find credible vendors these days.

 

[TerryS]

I ordered the Linear Tech OP-Amps (LT1364) directly from LT. Not very fast, but reasonably priced....

Terry

 

[Mr. Lin]

Mr Lin, are you sourcing the opamps from one vendor? I would like to roll some, just hard to find credible vendors these days.

I get what I can from Digikey. If they don't have it I usually buy from samerpav on ebay. He's proven trustworthy and reliable over and over again.