Little Dot I+ Headphone Amp Impressions

[Fredisyoga]

Hi guys I just started using my Little Dot 1+ v4 again after getting a e70 velvet dac and raspberry pi as my streamer. I’ve been enjoying all my EF95 tubes and just purchased a pair of Mullard CV4015 EF92 tubes. I think I configured the amp properly with the two jumpers (upper left and lower right); switches stayed the same. At least I think they are the jumpers (they came with the unit).. are they the small plastic nibs that stick into the 2 metal prongs?? I ask because the CV4015 tubes are more than half the volume and sound horrible compared to my EF95 tubes. So I’m wondering if I am using the actual jumpers. Attached image with “jumpers” with manual on settings page. Are these it? They are just plastic…

 

[Chris Brown]

I’ve been enjoying all my EF95 tubes and just purchased a pair of Mullard CV4015 EF92 tubes. I think I configured the amp properly with the two jumpers (upper left and lower right); switches stayed the same. At least I think they are the jumpers (they came with the unit).. are they the small plastic nibs that stick into the 2 metal prongs?? I ask because the CV4015 tubes are more than half the volume and sound horrible compared to my EF95 tubes. So I’m wondering if I am using the actual jumpers. Attached image with “jumpers” with manual on settings page. Are these it? They are just plastic…

I have an older model but although there might be some differences in the circuit-board, they should be pretty similar. You should have two separate jumpers that are clearly labeled as being for EF92 (the teal jumpers in my picture). You would want to use those jumpers to short the pins when using EF92 type tubes (including CV4015) while leaving everything else the same. Do not short those pins when using EF95/6J1 type tubes. Also make sure that the center jumpers are in the 6J1 position, NOT the 408A position (this should not be a problem if you were previously using EF95 tubes, but important to double-check since 408A tubes use a much higher voltage).

Shorted, as shown in the picture, would be the correct EF92 configuration. The jumpers are more than just plastic. There is metal in the center of each jumper that shorts the pins. That's the whole purpose of the jumpers.



If the EF92 jumpers are attached to the pins correctly, then unknown why the CV4015 tubes are not sounding good.

Personally I'd recommend finding some 6HA5/6HM5 or 6HQ5 tubes. These are all actual triodes (as opposed to pentodes operating as triodes), and work with the EF95 setting without any modification. The Sylvania 6HA5/6HM5 tubes are my personal favorites.

 

[Fredisyoga]

I have an older model but although there might be some differences in the circuit-board, they should be pretty similar. You should have two separate jumpers that are clearly labeled as being for EF92 (the teal jumpers in my picture). You would want to use those jumpers to short the pins when using EF92 type tubes (including CV4015) while leaving everything else the same. Do not short those pins when using EF95/6J1 type tubes. Also make sure that the center jumpers are in the 6J1 position, NOT the 408A position (this should not be a problem if you were previously using EF95 tubes, but important to double-check since 408A tubes use a much higher voltage).

Shorted, as shown in the picture, would be the correct EF92 configuration. The jumpers are more than just plastic. There is metal in the center of each jumper that shorts the pins. That's the whole purpose of the jumpers.

View attachment 3094560

If the EF92 jumpers are attached to the pins correctly, then unknown why the CV4015 tubes are not sounding good.

Personally I'd recommend finding some 6HA5/6HM5 or 6HQ5 tubes. These are all actual triodes (as opposed to pentodes operating as triodes), and work with the EF95 setting without any modification. The Sylvania 6HA5/6HM5 tubes are my personal favorites.

I’ve been solely referencing the tube rolling forum

I have an older model but although there might be some differences in the circuit-board, they should be pretty similar. You should have two separate jumpers that are clearly labeled as being for EF92 (the teal jumpers in my picture). You would want to use those jumpers to short the pins when using EF92 type tubes (including CV4015) while leaving everything else the same. Do not short those pins when using EF95/6J1 type tubes. Also make sure that the center jumpers are in the 6J1 position, NOT the 408A position (this should not be a problem if you were previously using EF95 tubes, but important to double-check since 408A tubes use a much higher voltage).

Shorted, as shown in the picture, would be the correct EF92 configuration. The jumpers are more than just plastic. There is metal in the center of each jumper that shorts the pins. That's the whole purpose of the jumpers.

View attachment 3094560

If the EF92 jumpers are attached to the pins correctly, then unknown why the CV4015 tubes are not sounding good.

Personally I'd recommend finding some 6HA5/6HM5 or 6HQ5 tubes. These are all actual triodes (as opposed to pentodes operating as triodes), and work with the EF95 setting without any modification. The Sylvania 6HA5/6HM5 tubes are my personal favorites.

Thanks!! I’ve been solely referencing the headfi forum tube rolling page for years.. religiously haha. Amazing I’ll definitely try the 6HA5/6HM5 and 6HQ5 tubes. The “jumpers” that I have been using that were in my unit already when I first received it don’t look like the ones in your picture and don’t look like they have metal in them to make the short. However, the switches that change from 6J1 to 408A are the kind that have the metal to short the pins. What are they called so I can buy them on eBay or aliexpress? Attached image showing the jumpers I have been using.

 

[Chris Brown]

What are they called so I can buy them on eBay or aliexpress?

Well I've always called them jumpers but I believe they can also be referred to as "shunts". If I were buying new ones, I'd go for the ones with the little tabs on them so you can grab them easier with your fingers instead of having to use tweezers or needle-nose pliers.

MINI SHUNT JUMPER Kit w/Handles MOBO HARD DISK IDE SATA Raspberry PI Arduino D16 | eBay

16 mini jumpers: 2.54 mm / 0.1" spaced. With handles. Fit most motherboards and desktop IDE disk drives, many printed circuit boards, Raspberry Pi and Arduino boards. Suitable for Arduino Raspberry Pi PCB PC DVD HDD Motherboard Shorting and More.

www.ebay.com