Little Dot MK8SE / MK6 Super Mods (All verified mods are on first page)
Apr 12, 2018 at 3:07 PM Post #3,226 of 4,154
Yes that would be alright, sorry I thought that was what you meant when you were probably talking about the power tube decoupling. I have 40uF driver decoupling caps atm. Don't know what effect they have though because I've only ever had those caps.

Ahh gotcha. I wanted to confirm before i swap the 15uF's for 33uF's in my friends amp. Ill see if i can compare, once everything is done.
 
Apr 12, 2018 at 3:11 PM Post #3,227 of 4,154
Out of interests, I checked some of those Caps, and quickly add up to Thousands....LoL!

So, is the sound performances up to par ? Can it be said to be top of the line that can compete against very expensive one ? How about output impedance?
 
Apr 12, 2018 at 3:17 PM Post #3,228 of 4,154
Out of interests, I checked some of those Caps, and quickly add up to Thousands....LoL!

So, is the sound performances up to par ? Can it be said to be top of the line that can compete against very expensive one ? How about output impedance?

Its a balancing game tbh. Like some of the caps that @SonicTrance is using have great value for money.But its upto you if you want to spend that much, after a certain price you reach a point of diminishing returns.

The most i spent on my upgrades was $350.
 
Apr 12, 2018 at 3:28 PM Post #3,229 of 4,154
Ahh gotcha. I wanted to confirm before i swap the 15uF's for 33uF's in my friends amp. Ill see if i can compare, once everything is done.
Right.

My view is that the CCS mod will do more than the driver stage decoupling but I can't say for sure because we haven't tested or compared these properly in this amp. But the idea of a film cap in the driver stage is to provide a fast response reservoir to tighten things up a bit.
 
Apr 12, 2018 at 3:42 PM Post #3,230 of 4,154
Out of interests, I checked some of those Caps, and quickly add up to Thousands....LoL!

So, is the sound performances up to par ? Can it be said to be top of the line that can compete against very expensive one ? How about output impedance?

I think the cost of mine was £300 or so, not bad considering the amp wasn't particularly expensive for a balanced amp can't say exactly because it kept changing but for example the Audyns are quite cheap compared to the Jupiter caps but with very similar performance. The quality caps do make a massive difference together with tubes etc. My preferred set of tubes atm cost $5 each!The output impedance is one of our mods to tailor the amp to your desired set of headphones.

I will leave the question of whether it's TOTL or not I think others here might like to say what they think but some members have had access to various hifi meets in which the very best amps were on show.
 
Apr 12, 2018 at 3:54 PM Post #3,231 of 4,154
The changes weren't as dramatic as the ones i had before, as i basically rearranged things around and changed the wiring from before.

But the most apparent and biggest changes were to the separation and the blackness of the background when nothing is playing. Before this, the soundstage had a nice bump going from stock to the new resistors/caps, with the wiring everything is much more "clearer". And the low end is so much more well defined. When compared to my WA22, it sound like this has a layer of cloudyness removed, whereas the WA22 feels like it has something in front of it. (if this makes any sense)



I had this issue once with one of my desktop motherboards, the only way i could fix it was to first clean the affected area with isopropyl alcohol and then to scrape all the carbon off. Which in turn ruins a lot of traces coming into the affected region, so i had to run wires on both sides of the board. Luckily these amps dont have as many traces as a motherboard, and you seem to have the blue PCB so traces will be easier to spot.
A well lit workbench will go a long way to help you in spotting the affected the traces.
I guess sound stage will be better after 100 hours run
 
Apr 12, 2018 at 4:02 PM Post #3,232 of 4,154
I guess sound stage will be better after 100 hours run
All the parts have been run for way more than 100 hours already. I just rearenaged them recently and changed the wiring.
 
Apr 15, 2018 at 1:02 PM Post #3,233 of 4,154
That damage area has carbonize conductive which cause ground shorted PNP transistor, all other circuit has no issue at all after checked with DMM
After checked cabling, ground connection, at last the amp turn on peacefully however still read "0" on the vu meter, no idea what's wrong, the DC voltage reading :
(106) (3.5) (3.5) (106) (106) (3.5) (3.5) (106)
(106) (3.5) (3.5) (106) (106) (3.5) (3.5) (106)
(215) (215) (215) (215)
 
Apr 16, 2018 at 5:14 PM Post #3,234 of 4,154
After checked cabling, ground connection, at last the amp turn on peacefully however still read "0" on the vu meter, no idea what's wrong, the DC voltage reading :
(106) (3.5) (3.5) (106) (106) (3.5) (3.5) (106)
(106) (3.5) (3.5) (106) (106) (3.5) (3.5) (106)
(215) (215) (215) (215)

Your voltages at B+ side at 106v are nearer to the correct value so if we assume that everything is alright up to there then the problem is after the anode and around the cathode area, but you are getting no voltage drop across the 150R resistor which I can't understand. I'm assuming that you have checked the resistance across your 150R resistors. All your voltages are the same at either side of the anode and cathode resistors. I'm assuming that because both your channels show equal values that the problem is higher up the chain. I believe the 2 channels are linked by the 680R resistor but I'm at my limits here, hopefully someone who is more knowledgeable than me will chime in.

In the meantime, it's a long shot but you could do a continuity check with one end of your multimeter to ground and the other on various components: each leg of the 680R resistor in the middle near the fuses, each of the pins in the output XLR sockets, then each of the pins in the power tube sockets and note down the results. That should show up anything going to ground that shouldn't be.

Edit: Did you manage to fix the carbonize issue? And are you board traces through that burnt area OK now?
 
Last edited:
Apr 20, 2018 at 9:43 AM Post #3,235 of 4,154
Your voltages at B+ side at 106v are nearer to the correct value so if we assume that everything is alright up to there then the problem is after the anode and around the cathode area, but you are getting no voltage drop across the 150R resistor which I can't understand. I'm assuming that you have checked the resistance across your 150R resistors. All your voltages are the same at either side of the anode and cathode resistors. I'm assuming that because both your channels show equal values that the problem is higher up the chain. I believe the 2 channels are linked by the 680R resistor but I'm at my limits here, hopefully someone who is more knowledgeable than me will chime in.

In the meantime, it's a long shot but you could do a continuity check with one end of your multimeter to ground and the other on various components: each leg of the 680R resistor in the middle near the fuses, each of the pins in the output XLR sockets, then each of the pins in the power tube sockets and note down the results. That should show up anything going to ground that shouldn't be.

Edit: Did you manage to fix the carbonize issue? And are you board traces through that burnt area OK now?
Sorry for the late reply, the damage board area fixed already but the amp still reading "0" on VU meter , totally silence to headphone, still can't find out what's the problem yet
 
Apr 20, 2018 at 10:36 AM Post #3,236 of 4,154
Sorry for the late reply, the damage board area fixed already but the amp still reading "0" on VU meter , totally silence to headphone, still can't find out what's the problem yet
Your voltages at B+ side at 106v are nearer to the correct value so if we assume that everything is alright up to there then the problem is after the anode and around the cathode area, but you are getting no voltage drop across the 150R resistor which I can't understand. I'm assuming that you have checked the resistance across your 150R resistors. All your voltages are the same at either side of the anode and cathode resistors. I'm assuming that because both your channels show equal values that the problem is higher up the chain. I believe the 2 channels are linked by the 680R resistor but I'm at my limits here, hopefully someone who is more knowledgeable than me will chime in.

In the meantime, it's a long shot but you could do a continuity check with one end of your multimeter to ground and the other on various components: each leg of the 680R resistor in the middle near the fuses, each of the pins in the output XLR sockets, then each of the pins in the power tube sockets and note down the results. That should show up anything going to ground that shouldn't be.

Edit: Did you manage to fix the carbonize issue? And are you board traces through that burnt area OK now?

Are these voltages with the default caps?

One thing i would definitely do is check if the via's are not damaged.
 
Apr 20, 2018 at 4:08 PM Post #3,238 of 4,154
I can't get any result right now include output XLR pin, cause the meter show unstable big differential DC voltage reading, I just got the input pin reading all same 133.5 mV

OK, have you continuity tested everything you have done to the next point on the trace on both sides of the board, very important as the board is double sided just to confuse us.

I don't believe your 150R resistors are at fault so the only way that I can see that the voltage is the same on both sides of the 150R resistor is that the signal is taking a short cut and bypassing the resistors there. So I suggest to do what I said in my last post and check for shorts or ground on every component, so just run a continuity test with one end of the multimeter in ground and the other on every leg of every component including the output XLR's, tube socket pins etc., amp off, and let us know the result.
 
Apr 20, 2018 at 4:55 PM Post #3,239 of 4,154
OK, have you continuity tested everything you have done to the next point on the trace on both sides of the board, very important as the board is double sided just to confuse us.

I don't believe your 150R resistors are at fault so the only way that I can see that the voltage is the same on both sides of the 150R resistor is that the signal is taking a short cut and bypassing the resistors there. So I suggest to do what I said in my last post and check for shorts or ground on every component, so just run a continuity test with one end of the multimeter in ground and the other on every leg of every component including the output XLR's, tube socket pins etc., amp off, and let us know the result.
I had checked the ground short earlier, that's why I found problem with transistor before. After transistor problem solve, the amp turn on no more crack sound, no more circuit burn, however both VU Meter now light up togather at the same time, I suspect either zener diodes, diodes, bridge retifier, N channel J-Fet and Mosfet having some issue, may be going to change those parts later. I also ordered some eyelets to fix those damage area. (https://www.aliexpress.com/item/100...ular-Rivets-DIY-Double-sided/32841162429.html)
 
Last edited:
Apr 21, 2018 at 5:11 AM Post #3,240 of 4,154
Oh, right!

Not sure how that circuit works on switch on. There is a diode near the fuses in that area, I don't know if you've checked that. Anyway good luck!!
:)
 

Users who are viewing this thread

Back
Top