Little Dot MKIII Tube Rolling
Oct 28, 2008 at 4:22 PM Post #1,336 of 3,377

NikZ

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Quote:

Originally Posted by sinisterm /img/forum/go_quote.gif
Finally got Mullard EF92 (M8161, large shield). OOB they sound, hmm, harsh, I'll tell my impressions after they get some hours.
tongue.gif


Anyone noticed that with EF92 you need to turn volume knob ~5 lines louder to get same sound level as with EF95's? :O



My M8161s did that , too.
 
Oct 28, 2008 at 4:26 PM Post #1,337 of 3,377

ScottieB

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Quote:

Originally Posted by sinisterm /img/forum/go_quote.gif
Yeah they are (what a pain in the **** were they to put on, had to use two screwdrivers like chinese eatingsticks
biggrin.gif
). I didn't mean the harshness as in distortion or anything like that, they just sound harsh, like almost every NOS tube out-of-box I have heard. :p



Man that IS a pain - I consider myself very lucky I got one with switches instead of jumpers (and even still I sometimes think twice about switching btwn EF92 and EF95 - man I'm lazy)!

Anyway the harshness isn't all that surprising - give them some time and they should smooth out. But the volume knob isn't something I've noticed... but there's lots of stuff I don't notice when I'm busy rockin out head-fi style
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Oct 28, 2008 at 11:40 PM Post #1,339 of 3,377

Pricklely Peete

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Quote:

Originally Posted by eboy2003 /img/forum/go_quote.gif
US 110V version MK III and MK IV users be aware. Please check your local AC voltage with a true RMS multimeter. I have confirmed with Mr. Yang that the US version is designed for 110V AC, given 120V AC (in my case, it's 122V AC) will adds 10% more on heater voltage and reduce the tube life drastically. He suggest put a 1ohm 1w resistor in series for each tube.


If you could take pics of the retrofit of these resistors that would be a valuable resource indeed.

In my neck of the woods 127V AC is the norm...so this is a must do mod for me.

Which pin for each tube if you can't take pics please
smily_headphones1.gif


Thanks for the info eBoy2003,

Peete.
 
Oct 28, 2008 at 11:41 PM Post #1,340 of 3,377

Pricklely Peete

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Quote:

Originally Posted by sinisterm /img/forum/go_quote.gif
Yeah they are (what a pain in the **** were they to put on, had to use two screwdrivers like chinese eatingsticks
biggrin.gif
). I didn't mean the harshness as in distortion or anything like that, they just sound harsh, like almost every NOS tube out-of-box I have heard. :p



Use a toothpick next time, either crazy glued in or wedged into the middle or edge of jumper...works like a charm.

Peete.
 
Oct 29, 2008 at 5:12 AM Post #1,341 of 3,377

eboy2003

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All right, I've done mod for my MK IV. MK III mod will be similar. Folks, this is a must mod especially for MK IV SE users here in US, otherwise, you will run risk of burn out 6H30Pi-EH like mine does. MK III and MK IV runs power tube heater unregulated AC straight from toroidal transformer!!! Lots of forum actually recommend 6.2V heater voltage for 6H30Pi, too high heater voltage will reduce its life drastically.

Unfortunately my burn-out 6H30Pi-EH did not recover at the lower heater voltage, it's gone for ever.
mad.gif


Here are the mod photos:

1. Pull out the board, the heater voltage line (white) are directly soldered to the 9-pin socket.
2983577784_5a18b592b3_o.jpg


2. Solder a 1ohm 2W resistor in series. Mr. Yang recommend 1ohm 1W, but 6H30Pi heater eats ~800mA current, it's better to have some leeway for this resistor. Also Mr. Yang said matching is not necessary, but I matched those resistors anyway. Make sure you leave some space from the resistor to board, this resistor will run hot! And don't let it short anything, use heat shrink to protect all naked wires and solder joints.
2982720899_4d0d922e93_o.jpg


3. After mod, test the heater voltage of the power tube, use a true RMS multimeter to measure AC voltage between pin 4 and pin 5. It used to be start 7.0V, and slowly drop to 6.8-6.9V. Now with this mod, it starts from ~5V, and slowly climb to 6.3-6.4V, because cold heater has smaller resistor than fully heated one, this mod also serves soft start functionality.
beyersmile.png
Picture here shows the heater voltage for regular Sovtek 6H30 after the mod, EH 6H30Pi is a little bit lower at 6.325V.
2982720937_b0e4d011ea_o.jpg
 
Oct 29, 2008 at 3:31 PM Post #1,342 of 3,377

Penchum

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Quote:

Originally Posted by eboy2003 /img/forum/go_quote.gif
All right, I've done mod for my MK IV. MK III mod will be similar. Folks, this is a must mod especially for MK IV SE users here in US, otherwise, you will run risk of burn out 6H30Pi-EH like mine does. MK III and MK IV runs power tube heater unregulated AC straight from toroidal transformer!!! Lots of forum actually recommend 6.2V heater voltage for 6H30Pi, too high heater voltage will reduce its life drastically.

Unfortunately my burn-out 6H30Pi-EH did not recover at the lower heater voltage, it's gone for ever.
mad.gif


Here are the mod photos:

1. Pull out the board, the heater voltage line (white) are directly soldered to the 9-pin socket.
snip

2. Solder a 1ohm 2W resistor in series. Mr. Yang recommend 1ohm 1W, but 6H30Pi heater eats ~800mA current, it's better to have some leeway for this resistor. Also Mr. Yang said matching is not necessary, but I matched those resistors anyway. Make sure you leave some space from the resistor to board, this resistor will run hot! And don't let it short anything, use heat shrink to protect all naked wires and solder joints.
snip

3. After mod, test the heater voltage of the power tube, use a true RMS multimeter to measure AC voltage between pin 4 and pin 5. It used to be start 7.0V, and slowly drop to 6.8-6.9V. Now with this mod, it starts from ~5V, and slowly climb to 6.3-6.4V, because cold heater has smaller resistor than fully heated one, this mod also serves soft start functionality.
beyersmile.png
Picture here shows the heater voltage for regular Sovtek 6H30 after the mod, EH 6H30Pi is a little bit lower at 6.325V.
snip



Sorry, I have to ask the obvious question: If this mod only lowers the final operating voltage by .675V, is that enough to really make a difference on longevity? Thanks!
smily_headphones1.gif
 
Oct 29, 2008 at 5:11 PM Post #1,343 of 3,377

Pricklely Peete

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Thanks eBoy,

Yes Pench that added voltage will shorten the life of the tubes. I know it doesn't seem like much but the AC line voltage where I am has me concerned about my one and only pair of DR's.

It could knock as much as 50% off the life of the DR's. Have a look at some articles on the issue. 127V AC here is the norm and is way to high for my liking ...I think eBoy's suggestion of 2W is a very good (minimum) uprating in this case.

The additional side benefit as eBoy says is a soft start feature and likely a little less overall heat from the amp although I cannot say for sure at this point.

At any rate it gives me an excuse to finish the coupling cap mod (with those wonderful 2.2uf 250V K75-10 PLIO's I have sitting here )

In light of this development Pench you can also add these resistors when you receive your parts for your cap upgrade to your MK IV SE.

The resistor mod will have no effect on the SQ of the amps.

Peete.
 
Oct 29, 2008 at 8:04 PM Post #1,345 of 3,377

yamadog1998

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Quote:

Originally Posted by glitch39 /img/forum/go_quote.gif
6H30P-DR.

I know it's expensive, but if you want to take it to the very end of the MK's upgrade chain...




The Only 6H30P That I Can Find Are The 6H30P-SOV And The 6H30PI-EH G Will These Work In The LD MK111? And What Is The Difference Between The DR's And These? Thank You For The Help.I Also Found Sovtek 6H30Pi Which Are currently Being made In Russia.Which Retail For Around $20.
 
Oct 30, 2008 at 1:17 AM Post #1,346 of 3,377

eboy2003

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Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif
Thanks eBoy,

Yes Pench that added voltage will shorten the life of the tubes. I know it doesn't seem like much but the AC line voltage where I am has me concerned about my one and only pair of DR's.

It could knock as much as 50% off the life of the DR's. Have a look at some articles on the issue. 127V AC here is the norm and is way to high for my liking ...I think eBoy's suggestion of 2W is a very good (minimum) uprating in this case.

The additional side benefit as eBoy says is a soft start feature and likely a little less overall heat from the amp although I cannot say for sure at this point.

At any rate it gives me an excuse to finish the coupling cap mod (with those wonderful 2.2uf 250V K75-10 PLIO's I have sitting here )

In light of this development Pench you can also add these resistors when you receive your parts for your cap upgrade to your MK IV SE.

The resistor mod will have no effect on the SQ of the amps.

Peete.



I have my modded MK IV run overnight and it indeed produces much less heat than before. Sound wise no difference, after all, 6.3V heater voltage is the rated voltage for these tubes.

Depends on your normal AC line voltage, you may experiment with different value of resistors such as 0.9ohm, 1ohm, 1.1ohm, 1.2ohm, but 1ohm probably the easiest value to get.

I just wish I troubleshoot this earlier when the first 6H30Pi-EH burned out. Now with two 6H30Pi-EH burned out, I probably will direct go for a pair of DR and leave the stock Sovtek 6H30Pi-EB from MK IV to my modded MK III.

Peete: please let us know how the K75-10 sounds. My MK IV non SE has crappy Phoenix capacitors, I'm looking forward to replace that.
 
Oct 30, 2008 at 3:00 AM Post #1,347 of 3,377

Pricklely Peete

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Quote:

Originally Posted by eboy2003 /img/forum/go_quote.gif
I have my modded MK IV run overnight and it indeed produces much less heat than before. Sound wise no difference, after all, 6.3V heater voltage is the rated voltage for these tubes.

Depends on your normal AC line voltage, you may experiment with different value of resistors such as 0.9ohm, 1ohm, 1.1ohm, 1.2ohm, but 1ohm probably the easiest value to get.

I just wish I troubleshoot this earlier when the first 6H30Pi-EH burned out. Now with two 6H30Pi-EH burned out, I probably will direct go for a pair of DR and leave the stock Sovtek 6H30Pi-EB from MK IV to my modded MK III.

Peete: please let us know how the K75-10 sounds. My MK IV non SE has crappy Phoenix capacitors, I'm looking forward to replace that.




Hi eBoy,

Thanks for the tips and feedback. I'll be heading to the local Rat Shack and see what they have in metal films in the next couple of days (finish the mod on the MK III this weekend).

So far the K75-10's bypassed with Teflon's are impressive (in my MC-7R all tube preamp). It was a major overhaul.

Heres a pic showing the cap array.......the 4 large green bastards are 1 uf 500V K75-10's PLIO's. The rest are all pure Teflons.

MoreMC-7Rbuildshots003.jpg

MeiXingMC-7RUpgrade007.jpg



Peete.
 
Oct 30, 2008 at 3:21 AM Post #1,348 of 3,377

eboy2003

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Wow. That's impressive. But I'm not sure whether MK IV will have enough space to fit for this many caps. I'm currently thinking of using sonicap gen 1 from sonicraft. They got good review in cap notes. I tried them in my DIY 2 x AD1955 DAC and they sounds fairly neutral. Anyone has experience with this cap?

Will also try some K75-10 and sprague paper-in-oil caps...
 
Oct 30, 2008 at 1:11 PM Post #1,349 of 3,377

Penchum

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Quote:

Originally Posted by Pricklely Peete /img/forum/go_quote.gif
Thanks eBoy,

Yes Pench that added voltage will shorten the life of the tubes. I know it doesn't seem like much but the AC line voltage where I am has me concerned about my one and only pair of DR's.

It could knock as much as 50% off the life of the DR's. Have a look at some articles on the issue. 127V AC here is the norm and is way to high for my liking ...I think eBoy's suggestion of 2W is a very good (minimum) uprating in this case.

The additional side benefit as eBoy says is a soft start feature and likely a little less overall heat from the amp although I cannot say for sure at this point.

At any rate it gives me an excuse to finish the coupling cap mod (with those wonderful 2.2uf 250V K75-10 PLIO's I have sitting here )

In light of this development Pench you can also add these resistors when you receive your parts for your cap upgrade to your MK IV SE.

The resistor mod will have no effect on the SQ of the amps.

Peete.



Well, in that case, I'll have to look closely at my other two amps, to see if they need them as well. Not a problem, just one or more things for the pile in front of me.
smily_headphones1.gif
Jezz PP, I feel like I should call up the Roto-rooter man!
smily_headphones1.gif


Oh, and on a side note, I bent a credit card and purchased a new amp for my mini-system, the Audio Source AMP-100. Amazon for $79 and free ship. I just couldn't pass it up.
smily_headphones1.gif
I'll drive it with my Yamaha pre-amp, with FrankenZero sourcing and the MKIII and MKIVse hanging off of tape 1 & 2. I'm going to pull the Super-T amp and look it over seriously for some upgrades/mods. Once my speakers matured, the Super-T was struggling to drive them properly.
smily_headphones1.gif
 
Oct 30, 2008 at 4:16 PM Post #1,350 of 3,377

sinisterm

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eboy2003,

Do you think this could affect on 220V (europe) voltages too? I'm sure that my house has kinda slobby voltage output.

----

These M8161 sure sound great, but they don't mate with GS1K's that well.

BTW, I think I'm gonna put my amp(s) (2x MKIII EU version) + all my tubes for sale in a ~month, anyone interested here? You can check my tubes from my profile.
 

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