[gibosi]

Back in the day when I was listening to 408A's, I found these Philips Miniwatt TS62. However, even though these carried the Philips' label, I am quite sure Philips didn't manufacture them. The characteristic seams in the glass are missing and there are no visible etched manufacturing codes. My WAG is Philips contracted with Sylvania to make a deluxe 408A for the European market and these are the result. Anyway, as best as I can remember, these have the same sound as the Sylvanias. Nice tubes.
 

 

[BzzzzzT]

The EF91s are far better than the stock tubes, although find them very bassey which is perfect for my K550s but they don't pair well with the X2's. I think my favorite tubes so far are the 408As very clear mids and highs with recessed bass. Now just to try a few different opamps, I've heard a lot about the muses01 and 02 but I'm looking for something cheaper.

 
I love the X2s with the LD 1+! I actually liked the EF91s more than the 408As. I do like bass and my Little Dot is heavily modded, plus I am using the Muse 02, so my sound is probably different. I think the extra price of the Muse 02 is totally worth it. I think the Muse took the 1+ to another level. It even beat out a discreet opamp I purchased. You can get them from Mouser for around 50 after shipping, still pricy for an opamp though. I really liked the Burr Brown OPA620KG for a a good cheap opamp. But like tubes, opamps are a personal choice.

 

[benburton]

I bought a Little Dot I+ the other day, and I have tried rolling in a pair of Sylvania GB-408a tubes (bought them on eBay here). I followed the directions with the K1 and K2 jumpers on the 408a setting, and the J1 and J2 jumpers removed. When I powered the unit on the blue power light comes up, but the tubes do not glow and there is no sound from the unit. Works great with the stock tubes on the 6JI setting (K1 and K2 on 6JI, J1 and J2 removed).
 
Should I send this back to the seller and request a replacement? I talked to David from Little Dot, and he said that he can't offer support/replacement because the seller on Amazon is not authorized.
 
I suppose it could be the tubes that are to blame, but neither worked and I did try swapping them. The eBay listing also says they were tested and NOS (although not matched).

 

[gibosi]

  I bought a Little Dot I+ the other day, and I have tried rolling in a pair of Sylvania GB-408a tubes (bought them on eBay here). I followed the directions with the K1 and K2 jumpers on the 408a setting, and the J1 and J2 jumpers removed. When I powered the unit on the blue power light comes up, but the tubes do not glow and there is no sound from the unit. Works great with the stock tubes on the 6JI setting (K1 and K2 on 6JI, J1 and J2 removed).
 
Should I send this back to the seller and request a replacement? I talked to David from Little Dot, and he said that he can't offer support/replacement because the seller on Amazon is not authorized.
 
I suppose it could be the tubes that are to blame, but neither worked and I did try swapping them. The eBay listing also says they were tested and NOS (although not matched).

 
If you have an voltmeter, measure across pins 3 and 4 in the socket to see if there is 20 volts. (I haven't done this in a long time, so I am not sure if the 20 volt source is DC or AC. But I think it is DC.) In the socket, pin 1 is just to the right of the gap, so count counterclockwise to pins 3 and 4.
 
If you have 20 volts, the tubes are likely bad. However, you might want to clean pins 3 and 4 (scrape with a dull knife or use sandpaper) on the tube just to be sure.
 
If you do not have 20 volts in the socket, open the amp up and make sure the jumpers on K1 and K2 are tight and secure.
 
Cheers

 

[benburton]

Thanks for the tip gibosi. I've actually just decided to order another pair of WE-408a's. I will test those, and then I can be pretty sure that either the Little Dot is defective or the GB-408a's are. Will post updates.

 

[fragger008]

Hello all,
 
Thanks for this topic on which I can learn a lot of things !
 
I have AKG Q701 headphones, with a Little Dot I+ that I received two weeks ago, with stock Opamp and stock 6J1 tubes. The sound was pretty good for me, comparing to the headphones directly plugged in to my NuForce uDac.
 
Reading a lot of things on Internet, I decided to purchase an OPA2107 and a pair of Voskhod 6ZH1P-EV tubes. I've received the tubes 2 days ago and I'm still waiting for the Opamp.
 
First of all, I would like to say that I really love my AKG Q701, but I just find that it has a lack of bass, in terms of bass "volume", basses are here, but for my personal feeling they are not loud enough. Moreover, I love the highmids and highs that are really precise, but unfortunately to my ears I find them sometimes too fatiguing, particularly at loud volume. All this feeling when my headphones was directly plugged in on my NuForce uDac.
 
When I received my Little Dot I+ with stock configuration (stock Opamp with stock 6J1 tubes), I found that the bass volume was a little bit better, and high-mids and highs were less fatiguing so it was very good for all points.
 
Two days ago when I put my Voskhod tubes, I was wondering a lot of improvement since I've read many and many good impressions of these tubes. But I must say that I'm quite disappointed Ok, It is evident that the sound is more "precise" and more "clean" than stock tubes, particularly in high frequencies. But I find that bass volume is less than with 6J1 tubes, with less punch and impact Moreover, high frequencies are again fatiguing at loud volume...
 
I'm still waiting for the OPA2107, and I've also ordered a pair of 6HM5 E900 El Yugoslavia.
 
Do you think that the OPA2107 will go in the good direction according to my impressions ? Also I've read about the MUSES02, what about it ?
 
And also, is there some Opamp/tubes combination that work better than other ? For example, MUSES02 will work better with Voskhod 6ZH1P-EV than with 6HM5, whereas OPA2107 will work better with 6HM5 than with 6ZH1P ? Or something like that ?
 
For your point of view, what is the best combination of Opamp and tubes for the AKG Q701 to have more bass volume impact and punch, and less fatiguing high frequencies ?
 
Thank you by advance for your answers, and sorry for my bas english, I'm from France
Best regards,
Jonathan.

 

[tkoreaper]

I love my MUSES02. It was the first opamp I purchased for my LD1+ so I have no experience with any others. I will say though that it leaves me wanting nothing... sound is absolutely superb. At first it was very bright and tinny sounding, but after breaking it in overnight the sound came to life. I am currently using a pair NOS Mullard CV4015 EF92 tubes, but eagerly waiting for the pair of NOS El Yugoslavia 6HM5 that I recently purchased after hearing so much about them. I use the DT 990 PRO (250 OHM) headphones which are supposed to tinny sounding, but with my setup it's perfect. The bass isn't as much as stock levels, but the sound is much tighter and more clean. The tubes I ordered should bring the bass up a little more, but don't think I'm saying that it's current levels are lacking at all, I just want a little more punch.

 

[BzzzzzT]

  Hello all,
 
Thanks for this topic on which I can learn a lot of things !
 
I have AKG Q701 headphones, with a Little Dot I+ that I received two weeks ago, with stock Opamp and stock 6J1 tubes. The sound was pretty good for me, comparing to the headphones directly plugged in to my NuForce uDac.
 
Reading a lot of things on Internet, I decided to purchase an OPA2107 and a pair of Voskhod 6ZH1P-EV tubes. I've received the tubes 2 days ago and I'm still waiting for the Opamp.
 
First of all, I would like to say that I really love my AKG Q701, but I just find that it has a lack of bass, in terms of bass "volume", basses are here, but for my personal feeling they are not loud enough. Moreover, I love the highmids and highs that are really precise, but unfortunately to my ears I find them sometimes too fatiguing, particularly at loud volume. All this feeling when my headphones was directly plugged in on my NuForce uDac.
 
When I received my Little Dot I+ with stock configuration (stock Opamp with stock 6J1 tubes), I found that the bass volume was a little bit better, and high-mids and highs were less fatiguing so it was very good for all points.
 
Two days ago when I put my Voskhod tubes, I was wondering a lot of improvement since I've read many and many good impressions of these tubes. But I must say that I'm quite disappointed Ok, It is evident that the sound is more "precise" and more "clean" than stock tubes, particularly in high frequencies. But I find that bass volume is less than with 6J1 tubes, with less punch and impact Moreover, high frequencies are again fatiguing at loud volume...
 
I'm still waiting for the OPA2107, and I've also ordered a pair of 6HM5 E900 El Yugoslavia.
 
Do you think that the OPA2107 will go in the good direction according to my impressions ? Also I've read about the MUSES02, what about it ?
 
And also, is there some Opamp/tubes combination that work better than other ? For example, MUSES02 will work better with Voskhod 6ZH1P-EV than with 6HM5, whereas OPA2107 will work better with 6HM5 than with 6ZH1P ? Or something like that ?
 
For your point of view, what is the best combination of Opamp and tubes for the AKG Q701 to have more bass volume impact and punch, and less fatiguing high frequencies ?
 
Thank you by advance for your answers, and sorry for my bas english, I'm from France
Best regards,
Jonathan.

 
I LOVE the Muse 02. One thing I found about the Muse compared to all the other opamps it tried, is that it reduced sibilance without making the highs sound rolled off. Mouser electronics has them for $46.25 plus shipping. I also liked the bass it put out.
 
I really liked the 6J1 tube. I even liked the 6J1s more than my C3Gs

. My X2s tend the be slightly darker, so I think the 6J1s really work well with them. No the 6J1 is not as detailed as some other tubes, but I find it is really dynamic and fun to listen to. I think too many people discount this humble tube as not being prestigious/audiophile enough and don't give it a fair chance. I really want to try the 6HM5s. I would look for recommendations on what people like with the Q701s. I think it is good to have some different tubes to find what works best.

 

[fragger008]

Thanks for your answer
 
So do you have some "combination" examples of Opamp and Tubes that work well with AKG Q701 ? That maybe could improve the amount of bass and give less fatiguing highs at loud volume ?

 

[gulakpi]

I read from the other Little Dot Tube Rolling thread that the "ultimate" tube for the LD is the C3g on an C3g to 6AK5 adapter.
The C3g looks rather expensive on eBay, and there is a C3m available at lower costs.
 
My research showed the C3m is a C3g with 20V filament. Otherwise it is the same tube.
Can I interpret this as:  The C3m with the socket adapter can be used on the LD1+ like the WE408A (with the WE408A jumper settings)?

 

[gibosi]

  I read from the other Little Dot Tube Rolling thread that the "ultimate" tube for the LD is the C3g on an C3g to 6AK5 adapter.
The C3g looks rather expensive on eBay, and there is a C3m available at lower costs.
 
My research showed the C3m is a C3g with 20V filament. Otherwise it is the same tube.
Can I interpret this as:  The C3m with the socket adapter can be used on the LD1+ like the WE408A (with the WE408A jumper settings)?

 
The pin-out for the C3m is different than the C3g, and thus, a different adapter would be necessary. So yes, the C3m will work using the 408A heater settings, but you can't use the C3g adapters. However you can always ask one of the eBay vendors to build adapters for you, or if you are handy, perhaps you could build your own.

 

[benburton]

  Thanks for the tip gibosi. I've actually just decided to order another pair of WE-408a's. I will test those, and then I can be pretty sure that either the Little Dot is defective or the GB-408a's are. Will post updates.

 
Turns out it was the tubes that were defective, not the Little Dot. Now happily burning in WE-408a's.

 

[gibosi]

It is a little surprising that both tubes were defective. But for sure, it is good to know that there is nothing wrong with your amp. Enjoy!

 

[Meddlesome Duck]

Is it possible to use an adapter so the little dot I+ can support tubes such as the 6SN7 or the like?

 

[gibosi]

Is it possible to use an adapter so the little dot I+ can support tubes such as the 6SN7 or the like?

 
Where there is a will, there is a way.
 
However, it is not a simple thing to do. Given that the physical spacing between driver tubes is not consistent on LD amps, there is no universal adapter available that can simply be plugged in. In the end, it is easiest to just cobble a few parts together.
 
1) Either a 9-pin or an octal socket mounted on a bread board to enable easy solderless wiring. Simple adapters can then be used to allow the use of other double triodes.
 
2) Two 7-pin test sockets which are used to connect the external breadboad socket to the LD.
 
3) A DC laptop power supply which can provide at least 1.5A at 15V. The LD can safely provide up to 0.45A of heater current, however, the 6SN7 draws 0.6A and a 5687 draws 0.9A. 
 
4) A stepdown voltage regulator to adjust the output of the power supply to either 6.3V or 12.6V.
 
The following post is a little out of date, but still might be useful:
 
http://www.head-fi.org/t/563884/little-dot-tube-amps-vacuum-tube-rolling-guide/5760#post_10435226
 
And you might end up with something that looks like this:
 

 
Here, I am using a 9-pin breadboard socket wired up to run an E80CC at 12.6 volts. The laptop power supply is to the right, beyond the view of the camera. Evidently, the 7-pin Vector test sockets are no longer available, so it will be necessry to make something similar using 7-pin sockets as per the referenced YouTube video.
 

 
An RCA 6SN7 with a simple adapter to allow it to be used in a 9-pin socket.
 

 
A 5687 (I think) to show the ease of rewiring the socket to accommodate tubes with different pin-outs.
 
So, yes, it is possible to run 6SN7 as well as many other double triodes in a Little "Monster" Dot 1+.