[eboy2003]

I am not blaming Little Dot, with USD:RMB exchange rate dropping to 6.8 comparing to 7.3 a year ago, the manufacture will have to cut some cost if they choose not to raise the item price here in US. I will upgrade all caps and resistors myself to have better matched pairs anyway.

 

[Pricklely Peete]

Quote:

Originally Posted by eboy2003 /img/forum/go_quote.gif I am not blaming Little Dot, with USD:RMB exchange rate dropping to 6.8 comparing to 7.3 a year ago, the manufacture will have to cut some cost if they choose not to raise the item price here in US. I will upgrade all caps and resistors myself to have better matched pairs anyway.

Good points.....we often forget economic realities dictate certain decisions. In many instances the difference between a premium cap and it's lesser cost sibling is very little in the overall scheme of things. Although top shelf parts are a difference maker, the real keys are further DIY mods such as those you've outlined plus a few tricks I use to great effect (cost wise these tricks and tips are relatively cheap with an aural reward out of all proportion to money spent).

Most of the cost of amps is R&D, labor and chassis......something most consumers don't really take into account when inspecting the contents.....LD has managed to stuff their low cost offerings with a pretty fair selection of quality parts. It's admirable to see that in a budget offering.

Peete.

 

[eboy2003]

Just report the story of my continuing mod for MK IV.

MK IV uses unregulated AC for 6H30Pi heater, so put a resistor of 1 - 1.2ohm in series is absolutely necessary if you are using 110V AC version but your AC is actually 120V. For 6AK5 heater, it uses a 7805 + 2 IN4001 on the ground to regulate output about 6.1V. This design is fine, unfortunately the 7805 heatsink is just way too small to handle ~400ma heater current from 2 6AK5. It's so hot to touch and doom to fail in long run. The heatsink is also uninsulated and just about 1mm to touch the pin 1 of 6H30Pi. FYI Pin 1 is the plate for one of the triode section of 6h30 that carries ~200V, if the heatsink (7805 ground pin) ever touches it, you will see fireworks...

I have changed the 7805 and two 1N4001 circuit to LT1084 with 169ohm and 681ohm resistor, and 10uf tant Cadj, which outputs about 6.25V with 400ma load. You can also use LM317 or lower current LT1086/LT1085 with the same resistor value to do the job. The nice thing of LT1084/LT1085/LT1086/LM317 is their pin out is reversed comparing to 7805, well not exact reverse, you will have to alternate Vout and Adj pin to fit the board's trace. But this orientation allows you installing a big heatsink towards outside of the board. MK IV case is quite roomy, a big heatsink can easily fit.

OK, now pictures:

See how small the original heatsink is...
The picture also shows a bunch of other resistors and capacitors I have changed. My original MK IV non-SE version uses less quality components than SE version. Also installed a switch instead of the jumper pins for EF92/EF95 selection. The 2.2uf capacitor is removed/shorted, this is the coupling cap between volume pot and 6AK5. It's not necessary if your source device already has an output coupling capacitor to block DC. And taking the lesson of my MK III, I changed the 150ohm cathode and plate resistors to 2W ones.

The reverse side.

 

[punk_guy182]

Man that is some serious modding that you are doing.
Eveer thought of making your own amps and compete with Little Dot?

 

[eboy2003]

Quote:

Originally Posted by punk_guy182 /img/forum/go_quote.gif Eveer thought of making your own amps and compete with Little Dot?

No, I think use MK IV as the base to mod and improve sound quality is much better and fun. For DIY projects, chassis and transformer is not easy to get quality like Little Dot.

MK IV basically uses MJ circuit similar to this, just a few resistor value changes for 6AK5 and 6H30.

So far I have changed:

1. Added 1.2ohm/3W resistor on 6H30Pi heater (absolutely necessary)
2. Replaced 150ohm/1W plate and cathode resistor to 2W ones (highly recommended)
3. Replaced 7805 + 2 x 1N4001 for 6AK5 heater to LT1084 w/ bigger heatsink (recommended)
4. Changed 1000uf/35V and 220uf/25v 7805 power filter cap to panasonic FM (stock was UCC KYZ, probably OK quality)
5. Changed all 1/4w resistors to good quality dale, irc, and m/e ones, with hand matched on left/right channel. The only 4 left (2x 220K, 100K) near the dip switch are for lower impedance headphones, which I don't have to change. (not necessary if you already have IV SE)
6. Replaced the EF92 selection jumper to good quality switch.
7. Replaced the cathode capacitor 220uf/16V UCC SMH to Elna Silmic II 220uf/25V.
8. Shorted the input coupling capacitor 2.2uf MKP.

Next I will try to play with power filter caps (3 x 470uf/250V, 2 x 0.047uf) and output capacitor (2 x 330uf/200v, 2 x 2.2uf WIMA MKS4, 2 x 0.22uf) and the feedback capacitor 0.47uf/250v between 6H30 upper and lower section after my 6H30-DR and Silmic II caps burn in. The output cap probably will be the most bang of bucks. Ultimately I probably will build an external power supply or internal regulated power supply for 200V.

 

[punk_guy182]

THat is a lot of modding and your remarks are very interetsint but I'm curious as how SQ has improved with the changes you have made.

 

[Nidhogg22]

Would DT-990 Pro 250ohms be a good idea with this amp?

 

[kevinvisionm]

hello guys, my replacement amp just have been great but i feel it's a bit unbalanced. the sound on the right is a bit louder than the left. is anything i can do to help? thanks

 

[Penchum]

Quote:

Originally Posted by kevinvisionm /img/forum/go_quote.gif hello guys, my replacement amp just have been great but i feel it's a bit unbalanced. the sound on the right is a bit louder than the left. is anything i can do to help? thanks

Try swapping the driver tubes first, and see if the imbalance moves with the tubes. If not, then swap the power tubes (large in back) and see if the imbalance moves with them. It usually isn't a big thing. The tubes will need 45 hours to mature, and sometimes the imbalance will go away once they are mature.

 

[Penchum]

Quote:

Originally Posted by Nidhogg22 /img/forum/go_quote.gif Would DT-990 Pro 250ohms be a good idea with this amp?

Hey Nid,

I noticed that you were also looking at the MKV. Both amps should work well with your headphones. The question of the day is, "Do I want tube sound or Solid State sound?" There is a bunch of reading on HeadFi, that will help you decided which is more in line with your tastes.

If you read my reviews closely, they will give you a good starting point for your research into this. I suffer (or enjoy) both platforms, so I have both.

 

[Alfisti]

Seen a few people mentioning a crackling coming out of one chanel or the other. I had a similar problem a few months back. Crackling, moved the tubes around which made the issue better or worse to varying degrees depending on what tube was where. Talked to David, cleaned the tubes off...

...plugged the tubes back in, started them warming and about 30secs in the whole thing went pop. As in quite litterally pop: sound, acrid smoke, hissing, the whole schomozzle. Needless to say I turned it off and unplugged with a quickness.

Long story short it's gone back to Little Dot. Don't know what's wrong with it yet (shipping mixup, no-one's fault), but there's a replacement coming.

Have to mention: David at LD's been absolutely fantastic with the whole thing. Couldn't be more helpful if he tried.

 

[punk_guy182]

Quote:

Originally Posted by kevinvisionm /img/forum/go_quote.gif hello guys, my replacement amp just have been great but i feel it's a bit unbalanced. the sound on the right is a bit louder than the left. is anything i can do to help? thanks

I am having the same problem since I received it last summer. I'm suspecting the power tubes to be at fault but I'm not 100% sure. I'm guessing the internal components of the AMP are responsible for sound imbalancement. I'll wait for a price drops on those Russian Supertubes and I'll know for sure if the power power tubes were at fault or not.

 

[hombretranquilo]

Another port over the gain settings... with AKG K701

I read to owners who have their AKG K701 with the Little Dot IV gain settings to minimum, while others have fixed it a 10 ... David (from Little Dot) has recommended me to put the gain as low as possible so that my listening level was between "10 and 14 hours" at the potenciometer.

Well, if I put the gain to a minimum (as it comes from factory), my level of listening to my 701 is located on the 12 o'clock of the potentiometer ... but several users talk that a higher gain give more "punch" to the sound

What's your recommendation and / or experience with the gain settings and AKG 701?
Thank you

 

[oldson]

sorry guys if you have covered this, but this is a long thread to treck through.
can you tell me if this amp would pump enough power to drive my ath-a900 cans (40 ohm), without it having to be at full volume, all the time?
many thanks

my ldmkv is great but i just fancy a tube amp!!

 

[SoundCheck88]

Hello ,Audiophiles.!Had to comment on the LD -MK IV -a great work of art.!!That knob completes the amp.Just Beautiful.i have a question when i purchase the Little Dot SE-IV what conections will i need to use with my PC.?My PC sound better than my Apple I-POD or my I-PHONE.Thank You in advance .Take care .George.