[coinmaster]

Getting the LD back again has had one undesirable side effect after being used to listening though speakers. The soundstage of my HE-500's is not so good so everything is now pointing to the HEK V2's at some point in the distant future. This is the one area that is so much worse than listening with the APPJ. The other thing that the APPJ does better IMO is the bass response is slightly sharper, although quantity and impact is similar. However that could be down to the RCA power tubes because they do have that characteristic sound.

It's difficult to compare speaker amps with headphone amps though but they are remarkably similar in performance, and the APPJ is single ended of course.

I hope you weren't trying to drive speakers with the mk6 lol.
Also keep in mind the MK6 can sound like apples or oranges depending what you do to it.
Personally I highly recommend putting film caps in the power supply of the MK6 if you want much improved bass quality and quantity and just an overall quality improvement across the range.
And I got the best sound when mixing tubes as well, so I recommend that, 5998s with mullard 6080s were my best combo, I think. But the stock 6080s with 6as7 is also good if you don't have 5998s. The stock 6080wa tubes sounded much better than all the other 6080s I tried by a large margin when mixing, only barely beat by the mullards.

I dunno if they are equivalent to mix ask Coin.

You can use 6080, 6as7, 5998, other equivalents. I would recommend mixing different types rather than the same type with different brands.

There is some of the schematic in the APPJ thread.

Ah okay so it's nothing too fancy then. Not something I would ever build..too many flaws as MrCurwen said.

Why somebody would want to make a circuit that is so vulnerable to small variations is beyond me. I try to eliminate them.

From a pure engineers point of view yeah, but if you manage to tweak such an amp just right then it can blow you away like the MK6 did to me. I guess that can be seen as an advantage since a "well designed" amp will not be capable of sounding like much else than you designed it.

 

[baronbeehive]

It's really great to switch on the amp and wait for the meters to light up without the agonising worry about whether they're going to read OK now.

Thanks everyone for their help!

 

[Maxx134]

The soundstage of my HE-500's is not so good

Have you done any bias mods yet?.

Remember your speaker amp is actually using your room as an added
soundstage which not in the source music ..

Oh, ok. Why is this? The schematic you linked has 6P6 which is soviet 6V6GT.

My fault I forgot to state we have similar but different amps in that "APPJ" thread.

Anode resistance is key here. A reason why some tubes sound "dark" and some "bright" is because a small variation in rp changes the R in an RC lowpass or highpass filter somewhere in the circuit. Why somebody would want to make a circuit that is so vulnerable to small variations is beyond me. I try to eliminate them.

I have also noted and mentioned in past it was surprising to discover the very low bias setting of the driver tubes...
I am talking about the little dot mk6&8 having same driver stage.
The anode resistor was high at 220k ohm,
But the bias was at a very low point .

I believe it will promote and guarantee sonic changes in tube rolling,
Because the load lines measured by Sonic where plotted in lowest non linear areas of the driver tube..

I have to believe it was an intentional design to introduce tube sound into the driver stage,
and then the reliance on using feedback...

My guess for another strong reason of bias point,
would be for cutting costs on a lower voltage PSU for that driver stage.
So staying competitive in cost, while still making profit may have been a factor..

 

[Maxx134]

everything is now pointing to the HEK V2's at some point in the distant future.

Dam..
That reminds me to post the
HEKV2 Feilian Port Mod
Here along with original V1 mods.
While I was away from amp playing I was modding alot headphones lol.

 

[klnglim]

Everything you do with this design will make a difference(!)...

but the PSU improvements are the lesser,
compared to the most important noticeable upgrades,
which are:
1- the coupling caps
2-the WCF caps
3- and the bias adjustment to the driver tubes...

those are three areas of concern that I would do first,
because they will give you your most noticeable improvements currently....

The psu stage upgrade is also an improvement...
But the other mods we do to the rail voltage stated in first page also does same.


Although it is true that the PSU in every amp will interact with its load, the design of the PSU for the powerubes in this amp has already been stated as "musical" as is from a designer..
And yes it is a simplistic but beefy PSU.

I have just checked my amp and notice all those original red colour caps are WIMA MKP10 (0.22/250V), are those good quality caps?

 

[baronbeehive]

Have you done any bias mods yet?.

Remember your speaker amp is actually using your room as an added
soundstage which not in the source music ..


...

The power tube bias, and driver stage bias mods are finished, just the impedance mod to go, waiting on getting another 421A before I do that because I want to bias it initially for those tubes. I am must about to take some pics of the mods.

The soundstage is not a problem of the LD but of the HE-500's. At the time I got them they had probably the best soundstage of the HiFiMan's but by todays standards it is not very good, and after being used to listening to speakers for a year or more the difference is very striking, I must say my preference is always for listening through speakers but I realized that is not possible for some people, such as those living in apartments in NY for example lol, or for me all of the time.

...........


My fault I forgot to state we have similar but different amps in that "APPJ" thread.


...

They have 2 new APPJ's out now, one of which replaces mine!! That one only has 2 power tubes to replace the EL84's so I don't know how it works!

.........

I have also noted and mentioned in past it was surprising to discover the very low bias setting of the driver tubes...
I am talking about the little dot mk6&8 having same driver stage.
The anode resistor was high at 220k ohm,
But the bias was at a very low point .

I believe it will promote and guarantee sonic changes in tube rolling,
Because the load lines measured by Sonic where plotted in lowest non linear areas of the driver tube..

I have to believe it was an intentional design to introduce tube sound into the driver stage,
and then the reliance on using feedback...

My guess for another strong reason of bias point,
would be for cutting costs on a lower voltage PSU for that driver stage.
So staying competitive in cost, while still making profit may have been a factor..

Oh, I wondered how Sonic came to his preferred values for his driver stage.

Dam..
That reminds me to post the
HEKV2 Feilian Port Mod
Here along with original V1 mods.
While I was away from amp playing I was modding alot headphones lol.

Must check out that thread again to see what's up!

 

[baronbeehive]

I have just checked my amp and notice all those original red colour caps are WIMA MKP10 (0.22/250V), are those good quality caps?

They are OK for what they do, the mods only replace those that are important for SQ.

 

[baronbeehive]

SMLD MODS: (continued)

Driver Bias Mod - The idea is to optimize bias on driver stage. The total resistance at the anodes was changed to 33k ohms, the total resistance at the cathodes was changed to 390 ohms, as suggested by SonicTrance for the MKVi+, to change the operating point to a more linear part of the driver tube load line.

Like Maxx134, I decided to add resistors to existing. The alternative is to remove existing resistors and solder in new ones.

New resistors soldered in parallel to existing anodes:

New resistor soldered in parallel to existing cathodes:

You can follow my mods pages: 50, 53, 55, 57, 62, 65, 66, 68, 69, 70, 71, 72, 147, 179 which include pics. Also Mogos mods are here; 33-38, and SonicTrance here: 23, 43, including some great pics.

 

[klnglim]

They are OK for what they do, the mods only replace those that are important for SQ.

Is it better idea to replace some important resistors (below) before on going the next mod?
8 x Mills MRA 150 R/5 W
4X 220K Ohm (Anode resistors) - TKD CM2 Series 2 Watt - 1% Metal Film Resistors - High quality (Japanese) Audio grade resistor.
4 X 10k ohm ("Grid stopper" resistors)
2 X 1.5k ohm ("Common" Cathode resistors)

Do you know what Capacitance/Watts & type of resistors to be replace from picture below?

 

[klnglim]

Did anyone know what Capacitance/Watts & type of capacitors to be replace?

 

[Maxx134]

I have just checked my amp and notice all those original red colour caps are WIMA MKP10 (0.22/250V), are those good quality caps?

Do not change all caps.
Only the caps mentioned in first page.
The caps to change are :
1-Coupling caps
2-cathode caps
3-What caps.
Nothing has changed since first page, only the added extras of changing the bias points of the driver and powertube stages.
That means the driver tube anode resistors of 220k ohms and the 1k cathode resistor should be lowered .
You can use baronbeehive settings.
I myself did not need to go as low and kept my anode & cathode at higher settings,
Because I increased tge PSU voltage by lowering the last 3k3 resistor that feeds the driver stage circuit.
The PSU was a RcRc filter and the reason I could lower the last resistor was because we increased the last capacitance feeding the anodes.

Do you know what Capacitance/Watts & type of resistors to be replace from picture below?

Those should have been power resistors there.
There is no capacitance there.
The designer get away with using cheapo garbage resistors which cannot take the current so they slowly burn over time as you can see...
He try get away with using two resistors in parallel to try dissipate the wattage created there which makes more heat...
They are garbage 1-2watt resistors and is why they cannot take the power so they burn.

This in effect also lower the rail voltage to the powertube over time.

You need one power resistor here.
It is explained in first page.
The best to use here ie Mills wirewound resistor.
They are non inductive wirewound and take alot of punishment without burning.
Only thing to be careful with wirewound resistors is not to damage outer surface when soldering.

It is also recomended in first page to replace all your powertube anode & cathode resistor with Mills wirewound resistors as they are superior .
This is mentioned in first page.
Nothing has changed.

Did anyone know what Capacitance/Watts & type of capacitors to be replace?

There are no capacitors you circled .
You circled the resistors.
If You wanted to change any capacitors in the PSU,
It has been mentioned by coinmaster and also recomeneded on first page .
They are the last two caps of the PSU stage mentioned on first page.

 

[SonicTrance]

Do you know what Capacitance/Watts & type of resistors to be replace from picture below?

I would replace those, yes. They are already quite burnt and wont get any better, lol. The Mills 5W wirewound is perfect for that position.

Did anyone know what Capacitance/Watts & type of capacitors to be replace?

You don't measure caps in W. But all cap mods are on first page.

 

[SonicTrance]

SMLD MODS: (continued)

I'm glad that your amp is finally working again, baron! Go easy with the soldering iron!

 

[klnglim]

Do not change all caps.
Only the caps mentioned in first page.
The caps to change are :
1-Coupling caps
2-cathode caps
3-What caps.
Nothing has changed since first page, only the added extras of changing the bias points of the driver and powertube stages.
That means the driver tube anode resistors of 220k ohms and the 1k cathode resistor should be lowered .
You can use baronbeehive settings.
I myself did not need to go as low and kept my anode & cathode at higher settings,
Because I increased tge PSU voltage by lowering the last 3k3 resistor that feeds the driver stage circuit.
The PSU was a RcRc filter and the reason I could lower the last resistor was because we increased the last capacitance feeding the anodes.


Those should have been power resistors there.
There is no capacitance there.
The designer get away with using cheapo garbage resistors which cannot take the current so they slowly burn over time as you can see...
He try get away with using two resistors in parallel to try dissipate the wattage created there which makes more heat...
They are garbage 1-2watt resistors and is why they cannot take the power so they burn.

This in effect also lower the rail voltage to the powertube over time.

You need one power resistor here.
It is explained in first page.
The best to use here ie Mills wirewound resistor.
They are non inductive wirewound and take alot of punishment without burning.
Only thing to be careful with wirewound resistors is not to damage outer surface when soldering.

It is also recomended in first page to replace all your powertube anode & cathode resistor with Mills wirewound resistors as they are superior .
This is mentioned in first page.
Nothing has changed.


There are no capacitors you circled .
You circled the resistors.
If You wanted to change any capacitors in the PSU,
It has been mentioned by coinmaster and also recomeneded on first page .
They are the last two caps of the PSU stage mentioned on first page.

Sorry my mistaken for typing capacitors, actually what I meant was resistors..
As before make an order, just want to confirm replace all resistors with Mills wirewound, thanks again!

 

[baronbeehive]

Sorry my mistaken for typing capacitors, actually what I meant was resistors..
As before make an order, just want to confirm replace all resistors with Mills wirewound, thanks again!

Only the 8 x 150 ohm power resistors, and the ones you have circled:



I replaced the bottom pair with 2 x 8K2 MRA5, and you could replace the burnt pair with whatever value they are on your board. No use looking on the first page for these, they aren't mentioned!