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Help needed to upgrade the capacitor in OTL tube amp - Page 3

post #31 of 113

@Do you know what are the two white boxes sticking to the sides of the amp near the driver tubes?
It could by resistors it have to be resistors but why he used big ceramic one ? maybe someone who have the other version of LF339 with 6c5 driver will know?

 

@Also how is called what is used to solder the resistor network?

Solder terminal strips.

 


the diodes used in keph modded LF339 are very fast rectifying diode VISHAY BYW type very popular in use in switched-mode power supply, but my choice will be Schottky

I double checked and the cathode resistor is 470 ohm, but mills 430 ohm resistor was used in one of modded lf339 too.

 

Quote:
Originally Posted by telecaster View Post

Thank you a lot WAAL-E!! I now see a lot clearer in this amp! I was sure I responded last night but here it is again! Thanks for the schematic! I'm glad the SCR 250V is right because nothing else fits in there hehe!

 

So there is not imput cap? Isn't it strange or a genius of a design? Do you know what are the two white boxes sticking to the sides of the amp near the driver tubes?

 

I have bought some 2200pF teflon caps and 0.5µF KP caps in order to experiment with bypassing, a lot of fun in sight!

 

Thanks again for the diagram! I ask Yuking team about it, but they never responded...

 

I have something that I need to ask :

 

20110407_7628e3009424c9392248jbnllNciKGL3.jpg

 

What is are the two soldering card for and what are the components on them?

 

Also in Keph modded 339:

keph.jpeg

What are the diodes for (on the soldering card next to the 2000pF capacitors)? I assume the tiny caps are for decoupling the power filter? The diodes are needed if I want to bypass my power filter too?

 

Also how is called what is used to solder the resistor network? I need to order that part but I cannot find it unfortunately.

BTW thanks for the calculation of the resistor but I remembered my high school days yesterday and found this as well. Appart from that my resistor is 470ohms 50w, not sure why he change the value except that availability of parts...

 

 


Edited by WALL-E - 5/29/12 at 3:07pm
post #32 of 113
Quote:
Originally Posted by jcx View Post

any V1 cathode bypass would count as a "signal path" C if you're obsessing over Cap quality

Yes, and since jcx points out that it can be "interpreted" as part of the signal path, you should also bypass it to be consistent.


Edited by tomb - 5/28/12 at 7:03pm
post #33 of 113
Thread Starter 

Ok I've been learning a little bit about CRCRC filter. I guess I understand why the 339 sound very tight in the bottom, it is because it seems it's might be filtered that way.

 

I wonder what would be the effect if I would lower the filtering to only a CRC filter. If I understand well, if I keep the two resistors in serie, and if I move the middle cap to // of the last cap, I would achieve a last C of (820µF+820µF+440µF) while the first C is 820µF. Is it dangerous if I try it?

 

Or maybe I should use a lower value of nominal C1? Higher C1? Yuking is using 1000µF C1 and C2 // with two 220µF with whats look like a CRC:

It is his no cost object last project custom made for his friend. I know he is into classical music essentially, maybe that's why he's into tight bottom and presence.

照片 2091.jpg

 

For the record, he is using those film cap as output coupling, and that is only 120µF per channel it seems:

照片 2031.jpg照片 2081.jpg


Edited by telecaster - 5/29/12 at 1:54pm
post #34 of 113

I found that the aluminum-housed 470 ohms resistors have not too good tolerance the multimetr showed 514 ohm on one of them almost 10% and it could be worst when they heat up.
I'll gonna change it for Non Inductive -1% Wirewound resistors like, MILLS - MRC50 or MRA-12 12 watt in paraller conf, in power line I think I stick with Mills or Caddock for the driver section and the rest I will use some good Metal Foil Resistors.


In power supply I would try 4-pole electrolytic capacitors MUNDORF MLytic HV Series is especially designed for the application in innovative and demanding tube amplifiers.


And for output cupling Mundof too, MTube Series M-TubeCap polyprophylene film or MKP Series Film Capacitors.


Also will change the stock bridge for Schottky Bridge Rectifies and AC IEC Inlets only because  feling off wen connecting rigid power cords.
That's all.
Vishay 1845 MKP it could be anyway It be worth experimenting using different caps.basshead.gif

Quote:
Originally Posted by telecaster View Post

I added up all the prices for the caps I want to change and the resistors too, I came up with 230€, it's a little steep right... That is for the top of the line vishay BC electro, and 265µF of output coupling SCR MKP per channel. Oh and every elec will be bypassed by it's SCR MKP too. I am sure the price to pay won't transform the 339 radically, but I expect a good step up sonically. Oh and as a bonus I have shop teflon and KP as bypass experimentation!

 

WALL-E, thanks for the drawing I understand way better now! May I ask you what you want to upgrade in the 339?

 

I have an advice to ask though, I wonder if those MKP is any good for output coupling duty : Would they be good as I never heard anyone using them as such...?

 

$(KGrHqJHJCgE9!MFGW2FBP,VyBDY-!~~60_57.JPG

 

They have 3.5mOhms ESR, huge voltage rating which is good I understand, they are MKP of course, and I can have a good price.

Downside is it doesn't fit inside the central black cover, so I thought I could tie them together, markings hidden down, with the lugs facing toward the sides symetrically and have 8 units like that sticking between the two black covers remaining in the open air. For sure I'll have to find a way to secure them to the case. Oh the and total height of this monster cap would be 9cm, so it would be 1 or 2cm higher than the black box... Thinking about it, it's not that pretty, but that way I could pack high voltage MKP which otherwise I would have to stick with 250V MKP, it's the only way...


Edited by WALL-E - 5/29/12 at 3:09pm
post #35 of 113

This is single rail resistor voltage divider and leave it as is,  you can increase the capacity.
The Yuking custom amp could have different transformer winding to provide two split rail.

Quote:
Originally Posted by telecaster View Post

Ok I've been learning a little bit about CRCRC filter. I guess I understand why the 339 sound very tight in the bottom, it is because it seems it's might be filtered that way.

 

I wonder what would be the effect if I would lower the filtering to only a CRC filter. If I understand well, if I keep the two resistors in serie, and if I move the middle cap to // of the last cap, I would achieve a last C of (820µF+820µF+440µF) while the first C is 820µF. Is it dangerous if I try it?

 

Or maybe I should use a lower value of nominal C1? Higher C1? Yuking is using 1000µF C1 and C2 // with two 220µF with whats look like a CRC:

It is his no cost object last project custom made for his friend. I know he is into classical music essentially, maybe that's why he's into tight bottom and presence.

照片 2091.jpg

 

For the record, he is using those film cap as output coupling, and that is only 120µF per channel it seems:

照片 2031.jpg照片 2081.jpg

post #36 of 113
Thread Starter 
Quote:
Originally Posted by WALL-E View Post

This is single rail resistor voltage divider and leave it as is,  you can increase the capacity.
The Yuking custom amp could have different transformer winding to provide two split rail.


Ok thanks, can I lower C1 to 680uF or lower? Same 680uF for C2, then 1000uF for C3? If yes do I need to recalculate the Rn and how do I calculate R?

I read that it's best to have a small and fast C1 and a three times bigger C3, don't know about C2... Also I read that bigger is not better in PS filter, it can make the sound in the bass sterile.

 

C4 and C5 are // of C3 thus increasing its capacitance or not? I don't understand fully C4 and C5, could you please explain it to me?

 

Is it ok to bypasse C1 to C5 with 10µF MKP cap then again 0.42µF bypass? If yes where do I solder the bypass caps? Do I solder the 10µF just at the bypassed big electrolytic lug?

post #37 of 113

Voltage after graetz bridge will drop about 1,2÷1,4V and will increase after C1 capacitor Uout = ~Uin * √2 - 1,4V. So the first cap after bridge shuld be bigger value and the C2&C3 could be less value of capacity if you really want.
I measured the voltage on R1 is 179V,between R1 & R2 is 160V and between R2 & R3 is 142.6V and this is for power the V2, and between R3&R4 is 142.3 and on the end R4 we got 87V this is for power driver V1. I may suggest you C1,C2,C3 equal 1000uf and C4,C5 equal 220 or 330 or 470uF the value of R1..4 do not need to be changed.

To bypass EL I use value between 100nF to 1uF but you choiceu will gona work well, yee solder directly to the endings of EL.

Quote:
Originally Posted by telecaster View Post


Ok thanks, can I lower C1 to 680uF or lower? Same 680uF for C2, then 1000uF for C3? If yes do I need to recalculate the Rn and how do I calculate R?

I read that it's best to have a small and fast C1 and a three times bigger C3, don't know about C2... Also I read that bigger is not better in PS filter, it can make the sound in the bass sterile.

 

C4 and C5 are // of C3 thus increasing its capacitance or not? I don't understand fully C4 and C5, could you please explain it to me?

 

Is it ok to bypasse C1 to C5 with 10µF MKP cap then again 0.42µF bypass? If yes where do I solder the bypass caps? Do I solder the 10µF just at the bypassed big electrolytic lug?

post #38 of 113
Thread Starter 

Thanks a lot for the advices! I have bought 6 1000uF 200V BC for PS filter.

About the value of Rn: I need some help my seller doesn't have 200R and 1Mohm and 30Kohm (he carries 220R though)

R1 and R2 are 100R each right?

R3 is 200R?

R4 is 30Kohm?

R to V1 grid is 10Mohm?

I will order the 3 watts resistors so I don't want to mess it up many many thanks by the way!

post #39 of 113

V1(8 pin octal socket) resistor soldered to pin 1 and 4 is 1 M-ohm, resistor soldered between pin 5 and 8 his value is 1K-ohm.
I will post complete amplifier schematic with all my multimeter readings on weekand it should be helpful anyway.

R1,R2 100ohm/10watt
R3 200 ohm
R4 30K-ohm

Quote:
Originally Posted by telecaster View Post

Thanks a lot for the advices! I have bought 6 1000uF 200V BC for PS filter.

About the value of Rn: I need some help my seller doesn't have 200R and 1Mohm and 30Kohm (he carries 220R though)

R1 and R2 are 100R each right?

R3 is 200R?

R4 is 30Kohm?

R to V1 grid is 10Mohm?

I will order the 3 watts resistors so I don't want to mess it up many many thanks by the way!

post #40 of 113
Thread Starter 

Could 180ohm or 220ohm replace the 200ohm resistor? Same for the 30Kohm, does the 22Kohm is ok?

Is there a downside effect because I upgraded all PS caps to 1000µF for C1 C2 C3 and 470µF for C4 C5?

Particulary for C4 C5, by increasing the capacitance, does it increase the current to the driver? Will it help reducing hum in certain (like the EF80) tubes?


Edited by telecaster - 5/31/12 at 6:02am
post #41 of 113

The resistor values are carefully calculated by designer don't change the the value, if you don't have 200 ohms, 30K-ohm leave the original ones in place.

The B+ power supply is a simple single polarity type, the capacitor job is store a steady amount of charge and then quickly release it most of this charge when it is needed in this aplication also is in smoothing the output of a bridge rectifier after it has converted AC electricity into DC.

 

@is there a downside effect because I upgraded all PS caps to 1000µF for C1 C2 C3 and 470µF for C4 C5? : there is NO

@Particulary for C4 C5, by increasing the capacitance, does it increase the current to the driver? : NO

Will help reducking hum in general.

Quote:

Originally Posted by telecaster View Post

Could 180ohm or 220ohm replace the 200ohm resistor? Same for the 30Kohm, does the 22Kohm is ok?

Is there a downside effect because I upgraded all PS caps to 1000µF for C1 C2 C3 and 470µF for C4 C5?

Particulary for C4 C5, by increasing the capacitance, does it increase the current to the driver? Will it help reducing hum in certain (like the EF80) tubes?

post #42 of 113
Thread Starter 

@Wall-E : So the big ceramic resistor (white plastic box) is 10K ohm? Is it possible it is damage and cause crackling noise?

 

I change the big wirewound resistor today... They were fooked up! They are simply plastic resistor cap inside the aluminium heatsink, when I removed them they were completely loose and the plastic was desintegrated! I wondered why my amp was so hot, now that I changed it it is not hot like before! Still hot but less than before and less quickly!

I wonder what is wrong in my amp, I still have sometimes a crackling noise when no music is playing. Metal film resistors don't make that sound do they!? I have this crackling only on left channel. Yuking sent me all the wirewound resistors to replace them so I guess while I wait for the new parts for the mod, I will change and isolate where does this crackling noise comes from...

post #43 of 113
Thread Starter 

I am very curious about converting the 6SJ7 socket to 6J5 socket:

It seems so easy to do! Only change the pinouts and change R3 to 100ohm... R4 is connected the same, the filaments are pin 2 and 7 also, and 3 and 6 are the same. Only need to change the resistor of grid and the big ceramic.

 

It looks even possible to make some kind of several switches to change the grounding of the pins and to change the resistor pin, and to change the anode and cathode... It would be cool to be able to switch this. It must take some thinking to make the swtich combination idiot proof. Need also to make a switch to change R3 from 100R to 200R... hmm all in all there are no space to achieve this, but it's definately doable in design. Maybe just not worth it.

 

Problem is I have just one tube that I love with 6SJ7, while in 6J5 there are a lot to try that looks cool! Only TS 6SJ7GT looks cool, the others are ugly!

 

Or just change the socket to 6J5 and be done with it! There are a lot of nice tubes for those.

 

NB: filaments are the same 2-7pin.

6SJ7 pinout

6sj7_so.png

_DSC2323.jpg

 

 

6J5 pinouts

oc78_g_2.gif

d5e00472_2099.jpg


Edited by telecaster - 6/1/12 at 7:26pm
post #44 of 113
Thread Starter 
Quote:
Originally Posted by WALL-E View Post

@Do you know what are the two white boxes sticking to the sides of the amp near the driver tubes?
It could by resistors it have to be resistors but why he used big ceramic one ? maybe someone who have the other version of LF339 with 6c5 driver will know?

In fact the 6J5 version use it too. It is the EF86 version which doesn't use that resistor.

post #45 of 113

I don't know the value of the"white plastic box" resistor do you ?
I like your idea"all in one" to use switches to change the type of drivers tube, but even upgrade to 6c5,6j5 shuld be easy to do like you said.
The aluminum-housed resistor had inside thermo protection fuse? the thing what fell off, anyway they would need replacement. May I ask what type wirewound resistor you use as a replacment?
Do you have the cracking noise with all your driver tubes or just with them which need adapter?
I have one faulty ef80wf which after hour or two have statick clicking noise and not always.
When I got ef800tfk to try while ago with the adapters they humed/noise like hell and was sensitive to touch but the issue was not tubes but the adapters.
I opened(lifted up) the adapter with sharp tool  there was twisted bundle of cables which had interference making the noise.With the headphones on head  by simply ajust (twist/turn) top plate of adapter few milimetres left or right  maked the hum/noise disappeared for good the same i did with other adapter.

 

The second photo from the bottom it is the other version of  LF339 with 6c5,6j5 as a driver ?
 

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