[MrCurwen]

The schematic I posted is missing the 100 ohm gate stopper for the FET in the CCS. It can clearly be seen in Sonic's photos. Be sure to put that in, it is required. It also helps construction a lot.

100R between CCS and cathode node is not needed. A resistor is a good binding post, but maybe get a 1R resistor for that. Or 10 or something.


In some circuits you need a cathode stopper between cathode and CCS to prevent oscillations.

 

[baronbeehive]

The 2 most annoying things so far -

Taking the board out, and putting it back in, closely followed by taking the PSU Electrolytic caps out.

Welcome to the club!

Very nice job, I am in awe of your desoldering/soldering skills!

First impression , WHERE IS MAH BASS?

The bass on the MKVI actually has more thump than on my speaker APPJ, and that is no slouch!It does take a while to get used to the new sound and for me the refinement is one thing that makes it so much better, you notice much more happening than before when you really start to listen, it really draws you in.

I'm sure you're aware of this but just watch those 3 points highlighted because parts can move around when opening and shutting the chassis and I have the same problem with the third circle at the bottom, the wire is very near to the screw and you might not have noticed that!

So what about the WCF caps?

 

[baronbeehive]

These are the best pics I got on the CCS module:

Hopefully you can see all connections from these pics?
Middle pin (Drain) of the IRF830 connects to one cathode. There's a trace in the board between the cathodes so doesn't matter which one you connect. I also added a 100 ohm R between drain and cathode, mainly because I needed the CCS module to sit a bit higher up. I would actually advice against the 100R as the bias voltage is so low already and that R is going to drop it some more.

Thanks Sonic, they look very good pics. I will study them some more.
.

 

[klnglim]

After few weeks waiting for those components, just finshed all mod except decoupling caps, this is a low budget Russian Caps and bypass, Mundolf MKP Caps, 150R Mills resistors mod, the amp run very stable, sound stage wide, nice and natural comfort, after few hours run, tide bass improvement noticeable, hopefully more improvement in next 200 hours of burn in, may be will do decoupling in future soon, any suggestion for further improvement please give advise, thanks

 

[gug42]

@ klnglim : you can't go really further thant what you did.
If you want, you need to build a total different amp ... a SE one with good output transformer (lundhal or toroidy for cheaper one).


Please can you remind me the specs of the power transformers ?
Perhaps I will do an another amp with thoses parts

Thx !

 

[baronbeehive]

After few weeks waiting for those components, just finshed all mod except decoupling caps, this is a low budget Russian Caps and bypass, Mundolf MKP Caps, 150R Mills resistors mod, the amp run very stable, sound stage wide, nice and natural comfort, after few hours run, tide bass improvement noticeable, hopefully more improvement in next 200 hours of burn in, may be will do decoupling in future soon, any suggestion for further improvement please give advise, thanks

Hey, great day for mods from members!

That is looking fantastic, good work!

Re further mods you might be limited due to the size of the Russian caps unless you want to extend the chassis.

Here's my suggestions roughly in order of sonic benefits, any or all of these:
1 - WCF cap, might be a problem with space
2 - Driver tube bias mod
3 - CCS mod, think about his before doing the driver tube bias mod. I'm not sure but this might mean you don't need to bother with the decoupling for driver stage Also means that it's not so important to upgrade the PSU caps I think. I'm not sure yet as I haven't done it but could be one of the most important mods Also the fact you have Kasei cathode caps means that you gain on sonic benefits so PSU mods not so important.
4 - Power tube bias only if you are plannig on using 5998's/4221A's
5 - Wiring
6 - At least these resistors which are looking worse for wear and are important:

 

[baronbeehive]

@ klnglim : you can't go really further thant what you did.
If you want, you need to build a total different amp ... a SE one with good output transformer (lundhal or toroidy for cheaper one).


Please can you remind me the specs of the power transformers ?
Perhaps I will do an another amp with thoses parts

Thx !

Hey gug42, how is your build going?

 

[gug42]

Great ! Jobs done, and really working well Impressive dynamique, really powerfull bass and lots of details with evry headpones. Far better than the little dot. Perhaps a little bit too expressive in the trebble area. In comparaison the little dot sounds life less ....

My amp, well, take the headphone in their hand with strengh, power and authority. And I have'nt use high end materials : Toroidy for iron (transformers and choke), chemical capacitor bypassed with basic mkp (some blue boxes epcos), total 14 Kg
I have used simple but high end design : two powerlines, one by channel, an really carefull electrical ground implantation.
Tubes are Sylvania 6SN7WGT and JJ KT88

I'm waiting for an oscillo to mesure it.

In the future I will :
- Rebuild it to have a more compart form factor ! Perhaps with using a 6SL7 SRPP gomez
- Build one with theoretical better stuff : lundhal output transformers, hammond choke, full mkp and PIO capacitor (huge beasts), SRPP gomez for input, and DHT tubes for output (2A3 ? 45 ? 300B ? others ?)

 

[klnglim]

Hey, great day for mods from members!

That is looking fantastic, good work!

Re further mods you might be limited due to the size of the Russian caps unless you want to extend the chassis.

Here's my suggestions roughly in order of sonic benefits, any or all of these:
2 - WCF cap, might be a problem with space
5 - Driver tube bias mod
6 - CCS mod, think about his before doing the driver tube bias mod. I'm not sure but this might mean you don't need to bother with the decoupling for driver stage Also means that it's not so important to upgrade the PSU caps I think. I'm not sure yet as I haven't done it but could be one of the most important mods Also the fact you have Kasei cathode caps means that you gain on sonic benefits so PSU mods not so important.
4 - Power tube bias only if you are plannig on using 5998's/4221A's
1 - Wiring
3 - At least these resistors which are looking worse for wear and are important:

I agree with you is changing most of the resistor, just want to know can those resistors (from the pictures with yellow circle) change to wirewound 150R 5W instead of
original show is 120R 5W ?
I understand space inside this amp.is limited, just try my best to find tiny, low cost and better quality if possible as I like the original design case and look weird when extend it.
Another question is about cathode bypass caps, I still some caps (same brand same type) left over, can I add extra as parralel caps coupling?Will that cause sound badly?
Thanks

 

[klnglim]

@ klnglim : you can't go really further thant what you did.
If you want, you need to build a total different amp ... a SE one with good output transformer (lundhal or toroidy for cheaper one).


Please can you remind me the specs of the power transformers ?
Perhaps I will do an another amp with thoses parts

Thx !

Sorry I m not very sure about the power transformer specs and I never open the cover take a look too

 

[bloodhawk]

Welcome to the club!

Very nice job, I am in awe of your desoldering/soldering skills!



The bass on the MKVI actually has more thump than on my speaker APPJ, and that is no slouch!It does take a while to get used to the new sound and for me the refinement is one thing that makes it so much better, you notice much more happening than before when you really start to listen, it really draws you in.

I'm sure you're aware of this but just watch those 3 points highlighted because parts can move around when opening and shutting the chassis and I have the same problem with the third circle at the bottom, the wire is very near to the screw and you might not have noticed that!

So what about the WCF caps?

Thank you for the compliments

All the info in this thread by you, Max, Sonic, Redge has been invaluable!

Ah those wires won't move. The one on the top is much lower than it looks in the picture, from the terminal of the other cap.

And other ones are super stiff Cooper , they won't move even if I drop the amp lol. Plus the copper strands have this really strong and sturdy coating on them.

I might swap out the WCF caps in the future with some MKP's.

For some reason i kinda felt the thump was much more with only the Audyn's in. But it could also because the lower frequencies weren't rolling off as much, and now because of the extension they are rolling off much further down. End of the day not a deal breaker. Some of it has already come back, i have a feeling things will get even better over time as the caps settle in.

 

[baronbeehive]

I agree with you is changing most of the resistor, just want to know can those resistors (from the pictures with yellow circle) change to wirewound 150R 5W instead of
original show is 120R 5W ?

If you mean the WCF grid resistors I think you should stick to your board values, and not necessary for wirewound there, but you could since they are 5W. I'm not sure I can't remember what mine are there.

I understand space inside this amp.is limited, just try my best to find tiny, low cost and better quality if possible as I like the original design case and look weird when extend it.
Another question is about cathode bypass caps, I still some caps (same brand same type) left over, can I add extra as parralel caps coupling?Will that cause sound badly?
Thanks

Ha ha, yes it does look a bit weird!!!

No, that will degrade sound. You need the smaller capacitance value here because it is putting back the high frequencies that are lost due to the larger type upgrade caps. The smaller value caps as bypass are necessary, I found that with my other amp, without these type caps the sound becomes lifeless and others here have experimented and found just the right size and value caps which you should use.

Thank you for the compliments

All the info in this thread by you, Max, Sonic, Redge has been invaluable!

For some reason i kinda felt the thump was much more with only the Audyn's in. But it could also because the lower frequencies weren't rolling off as much, and now because of the extension they are rolling off much further down. End of the day not a deal breaker. Some of it has already come back, i have a feeling things will get even better over time as the caps settle in.

Great, I would have got nowhere without the help here.....apart from up the creek
.

That's an interesting point which I brought up recently with my comparisons with my other amp and found that the MKVI was less articulate in the bass regions. It's something we have tried to address here as a known aspect of the LD's bass being somewhat lacking in transient attack which I believe would elevate the LD to top level status.
I am holding out for the results of the CCS mod before I decide on this because it could do the trick. I believe it had similar results in your BH Crack speedball mod from what I've heard.

 

[baronbeehive]

Great ! Jobs done, and really working well Impressive dynamique, really powerfull bass and lots of details with evry headpones. Far better than the little dot. Perhaps a little bit too expressive in the trebble area. In comparaison the little dot sounds life less ....

My amp, well, take the headphone in their hand with strengh, power and authority. And I have'nt use high end materials : Toroidy for iron (transformers and choke), chemical capacitor bypassed with basic mkp (some blue boxes epcos), total 14 Kg
I have used simple but high end design : two powerlines, one by channel, an really carefull electrical ground implantation.
Tubes are Sylvania 6SN7WGT and JJ KT88

I'm waiting for an oscillo to mesure it.

In the future I will :
- Rebuild it to have a more compart form factor ! Perhaps with using a 6SL7 SRPP gomez
- Build one with theoretical better stuff : lundhal output transformers, hammond choke, full mkp and PIO capacitor (huge beasts), SRPP gomez for input, and DHT tubes for output (2A3 ? 45 ? 300B ? others ?)

Very interesting! What design did you use, was it DIY

 

[gug42]

Yep a DIY, a really standard SE with the spirit of "less is more", juste the usefull stuff :
- only R and C
- Two power line, one by channel
- Classical filter CLCRC
- One ground line by channel

Well if you wan i can send you the schematic

 

[baronbeehive]

Yep a DIY, a really standard SE with the spirit of "less is more", juste the usefull stuff :
- only R and C
- Two power line, one by channel
- Classical filter CLCRC
- One ground line by channel

Well if you wan i can send you the schematic

I think we would all be interested, thanks!