[baronbeehive]

I feel that the most interesting area of upgrade to go in now would be to do the same as has been done for the 6SL7 tube but for the 6SN7. This would need a switch because the optimal operating point for both tubes would not work together without it because they are so different with different load lines. I've heard both tubes on the stock amp and couldn't tell the difference but with both tubes optimised that would be entirely different and I would be interested to hear what the 6SN7 sounded like on it's optimum operating point. We haven't done this because we settled on the 6SL7 as being the best tube for the amp because of the higher gain so we didn't bother experimenting with the 6SN7. But I'm waiting for someone to do it! The anode/cathode tests are what I feel would bring about the most variance in sound.

A switch could also switch between different anode/cathodes with the same tube and could produce a different sound. For instance I have been wondering what sound the operating point low down in the distorted area of the grid would be like. I didn't do this because I was trying to find the best operating point, ie. the least distorted sound. It's possible that the sound would be very tubey therefore you could switch between transparent/tubey sounds depending on your mood, or what type of music you were listening to.

A switch would be simple to do by connecting in parallel the desired anode/cathode resistor to move the operating point to where you wanted it to be. It would be better to have 2 switches, one for anode and one for cathode, this would give 4 different combinations.. and if you had a similar switch for the 6SN7.. well that would be where it would start to get very interesting!

 

[talan7]

Some crazy looking mods on here

 

[CopperFox]

Well I haven't posted for a while. This is because I realised the PCB on my MKVI+ had gotten into a bad enough condition that it needed replacing.

While doing extensive component rolling it is a good idea to try and preserve the PCB from excess wear, tear and heat (instead of doing this for the various new components by carefully removing any older solder from the PCB before installation). It is also probably a good idea to solder extension leads to the joints on the pcb for any components-to-be-rolled. And solder those components to the extension lead instead to keep the pcb in good condition (particularly on the components where the solder joints/pads on the pcb are small). This will probably actually save some time and pain too as it is easier to solder/desolder from the ends of extension leads than directly to the pcb when there is a lot of large added components in the way.

I figured I wouldn't have the time and patience to actually replace the PCB at the moment so in mid-february I decided to order a complete new amp. So I did that... and four weeks later got notified that the black version of the amplifier is not available and not in production and the order was cancelled on my behalf. I asked by email from Little Dot if there was any particular reason for the black version not being produced and if it was to resume production at a later date. But received no response whatsoever even though they had been responsive before that.

So I actually decided to start looking at other amplifiers that would fit the all-black aesthetic of my desk setup. But a few weeks later the silver color MKVI+ was on sale for a good enough price and I ordered that (too !!!). Then, again, for three weeks nothing happened but then the package showed up in tracking and genuinely looks to be arriving soon.

I don't really understand why there was no response from LD about the black version. Even if there are many kinds of bizarre shortages from garden gnomes to bicycle repair parts and shipping containers going on, it would be nice to have some response to queries about future availability of listed products.


The last thing I was doing on the black MKVI was testing the big cathode bypass caps. Even though I had initially positive impressions about the 2200uf FW series caps, it was looking like they were still burning in and the sound was getting worse - flatter, less dynamic, less soundstage and there were less power tubes that would sound ok with them.

The general trend with going from 470uf to 1000uf to 2200uf seemed to be that the sound got more detailed but slower and less dynamic with the larger caps. Also, with the 470uf caps, the high gain mode was too fast to use, with too many things sounding like hits from a hammer. Still, the low gain mode with 470uf sounds better to me than 1000uf with high gain. The latter has more detail but less dynamics, less soundstage and is slower. I do prefer dynamics and speed over detail. Still I feel that it would be interesting to have and test something between 470uf and 1000uf from the Nichicon KZ line.

 

[CopperFox]

You can add as many bypasses as you like but we don't recommend it. The main purpose of the cathode caps is to help transient recovery which will affect bass frequencies. The fastest cap you can have will be best to do this and avoid clipping as much as possible. Apart from this it won't have that much effect on overall sound signature, that is where the coupling and WCF caps come in, they will have greatest effect on sound.

If you imagine several batteries of different types all connected then the electrical signal coming out will be mashed up because of the differing discharge rates. This won't matter ordinarily but for the music signal it needs to be as pure as possible so smearing will inevitably occur as the signal is affected by the differences in the charge/discharge cycle. The signal at one point in the chain will be trying to move on but at another part it will be waiting for another cap to finish it's part of the cycle.

Hmm. Well, I did get a different similar idea. Since I would want to try Nichicon caps between 470 and 1000 uf, I will try using two similar 330uf 100v Nichicon KZ caps there. They obviously should not have very different discharge rates. I did some googling about parallel capacitors in audio circuits and the consensus seemed to be that using two capacitors instead of one larger capacitor is ok and should have lower esr even if the specifications of the larger and smaller caps were similar. With these Nichicons however, the smaller capacitors are also faster in specification. Maybe the combination of being both faster and larger (combined) capacity than the 470uf could be good.

So I would suggest if you want different sounds to try different coupling and WCF caps. Due to their position in the push/pull cycle the WCF caps we feel need to be the fastest and responsive to the high frequencies as you can go for, I have Mundorf SIO which I feel complement the more natural sounding Jupiters in the coupling position.

I've been thinkin about that too... might try Rike Audio Q-Caps or something else later.

 

[CopperFox]

I feel that the most interesting area of upgrade to go in now would be to do the same as has been done for the 6SL7 tube but for the 6SN7. This would need a switch because the optimal operating point for both tubes would not work together without it because they are so different with different load lines. I've heard both tubes on the stock amp and couldn't tell the difference but with both tubes optimised that would be entirely different and I would be interested to hear what the 6SN7 sounded like on it's optimum operating point. We haven't done this because we settled on the 6SL7 as being the best tube for the amp because of the higher gain so we didn't bother experimenting with the 6SN7. But I'm waiting for someone to do it! The anode/cathode tests are what I feel would bring about the most variance in sound.

A switch could also switch between different anode/cathodes with the same tube and could produce a different sound. For instance I have been wondering what sound the operating point low down in the distorted area of the grid would be like. I didn't do this because I was trying to find the best operating point, ie. the least distorted sound. It's possible that the sound would be very tubey therefore you could switch between transparent/tubey sounds depending on your mood, or what type of music you were listening to.

A switch would be simple to do by connecting in parallel the desired anode/cathode resistor to move the operating point to where you wanted it to be. It would be better to have 2 switches, one for anode and one for cathode, this would give 4 different combinations.. and if you had a similar switch for the 6SN7.. well that would be where it would start to get very interesting!

I actually have some new interest in the 6SN7 switch as I've been re-rolling 6SN7s and the various chinese big bottle power tubes I got late last year in my Cern Tube amp and some of those combinations have been interesting. Could get back to that in the future.

Another thing on my mind has been the "softness switch" for the power tube decoupling caps. I wonder if it would be possible to control the amount of power from those with some sort of potentiometer.

 

[baronbeehive]

Some crazy looking mods on here

Hello talan7!

Thanks . Not really crazy though, just trying to make an already good sounding amp even better lol! We feel a combination of crazy and sensible has pushed the amp to end game.

 

[baronbeehive]

Well I haven't posted for a while. This is because I realised the PCB on my MKVI+ had gotten into a bad enough condition that it needed replacing.

Ha! I was wondering when that curse would strike, you seem to have been in luck up to now. Most of us have had those problems in one way or another and have had to remedy the situation by patching up the PCB. It's not that difficult where the pads have lifted to patch them up by scraping away to expose the trace and then solder a piece of wire across to make the connection good. This is where having a DMM becomes an essential tool to check on your repairs.

While doing extensive component rolling it is a good idea to try and preserve the PCB from excess wear, tear and heat (instead of doing this for the various new components by carefully removing any older solder from the PCB before installation). It is also probably a good idea to solder extension leads to the joints on the pcb for any components-to-be-rolled. And solder those components to the extension lead instead to keep the pcb in good condition (particularly on the components where the solder joints/pads on the pcb are small). This will probably actually save some time and pain too as it is easier to solder/desolder from the ends of extension leads than directly to the pcb when there is a lot of large added components in the way.

Yes, good idea, especially where you are repeatedly changing components such as your experiments with the cathode caps. Having to repeatedly take out the PCB is a bit of a nightmare as well.

 

[baronbeehive]

I figured I wouldn't have the time and patience to actually replace the PCB at the moment so in mid-february I decided to order a complete new amp. So I did that... and four weeks later got notified that the black version of the amplifier is not available and not in production and the order was cancelled on my behalf. I asked by email from Little Dot if there was any particular reason for the black version not being produced and if it was to resume production at a later date. But received no response whatsoever even though they had been responsive before that.

Where did you order from? China or US? The LD site in US, littledous.com, has told me that they place great value on customer relations and test each amp thoroughly before sending out, and their warranty looks good. Whereas the China site have been undergoing changes recently.

The last thing I was doing on the black MKVI was testing the big cathode bypass caps. Even though I had initially positive impressions about the 2200uf FW series caps, it was looking like they were still burning in and the sound was getting worse - flatter, less dynamic, less soundstage and there were less power tubes that would sound ok with them.

The general trend with going from 470uf to 1000uf to 2200uf seemed to be that the sound got more detailed but slower and less dynamic with the larger caps. Also, with the 470uf caps, the high gain mode was too fast to use, with too many things sounding like hits from a hammer. Still, the low gain mode with 470uf sounds better to me than 1000uf with high gain. The latter has more detail but less dynamics, less soundstage and is slower. I do prefer dynamics and speed over detail. Still I feel that it would be interesting to have and test something between 470uf and 1000uf from the Nichicon KZ line.

Yes that's my preference too. Your findings are pretty much what I would expect from the larger caps, I found similarly. You might see some improvement in the KZ's up to 1000 uF but that would probably be it. And I feel that if you do go to 1000uF you might need the small bypass cap again. although you seem to have good higher frequencies, that's maybe down to your Miflex coupling caps.

 

[baronbeehive]

Hmm. Well, I did get a different similar idea. Since I would want to try Nichicon caps between 470 and 1000 uf, I will try using two similar 330uf 100v Nichicon KZ caps there. They obviously should not have very different discharge rates. I did some googling about parallel capacitors in audio circuits and the consensus seemed to be that using two capacitors instead of one larger capacitor is ok and should have lower esr even if the specifications of the larger and smaller caps were similar. With these Nichicons however, the smaller capacitors are also faster in specification. Maybe the combination of being both faster and larger (combined) capacity than the 470uf could be good.



I've been thinkin about that too... might try Rike Audio Q-Caps or something else later.

You could certainly try that. We feel that bypass cap use should really be limited and only used where necessarily due to the phase differences that would result which may or may not be detectable. Would be interesting to see if you can hear anything like that going on.

With WCF caps the consensus is that if you don't use the faster silver type caps in that position the sound would become more dull sounding. The WCF cycle goes on in sequence with the top triode operation and as such needs to be quite a distinct sound to avoid becoming muddled up. This is a particular feature of the design of the LD.

 

[baronbeehive]

I actually have some new interest in the 6SN7 switch as I've been re-rolling 6SN7s and the various chinese big bottle power tubes I got late last year in my Cern Tube amp and some of those combinations have been interesting. Could get back to that in the future.

Another thing on my mind has been the "softness switch" for the power tube decoupling caps. I wonder if it would be possible to control the amount of power from those with some sort of potentiometer.

Yes that could be interesting. It means setting up the biases for whatever tubes you use and being able to switch between them if you intend to use 6SN7's with 6SL7's for example.

Not sure if anything would come of a softness switch in the way you mention. We have done a switch for the power tube output to double it if using 5998 tubes. Personally I didn't find it of much use other than in increasing the volume.

I still think the best way to adjust the sound characteristics from slow/soft to fast/hard would be via, tubes, wires, operating points, or caps. Wires could be copper or silver internally or externally, operating points could be set to be transparent or distorted, choice of caps could be for lush or transparent sound, the same for tubes. For example a soft lush sound was easily achieved by using RCA 6SN7 grey glass tubes, whereas GE tubes will be much more transparent.

Edit: probably best to set the amp up for transparent sound and then vary that when required to softer by using tubes or distorted (lush, tubey) operating point.

 

[talan7]

Hello talan7!

Thanks . Not really crazy though, just trying to make an already good sounding amp even better lol! We feel a combination of crazy and sensible has pushed the amp to end game.

I ordered a MK VI from Shenzhen Audio and haven’t heard anything from them for almost two weeks since they asked me what color I wanted. Picked up a DT 990 600 ohm while waiting. Can’t wait to hear them on the MK VI, when it comes.

 

[baronbeehive]

I ordered a MK VI from Shenzhen Audio and haven’t heard anything from them for almost two weeks since they asked me what color I wanted. Picked up a DT 990 600 ohm while waiting. Can’t wait to hear them on the MK VI, when it comes.

Best of luck with your order. I know from the other LD forum that certain LD distributors have been getting a bad name so I hope that you have no problems with yours. It seems that customer relations and QC are not what they used to be now unfortunately, I hope they improve.

 

[talan7]

Would a good tube preamp to a solid state amp give a really good tube sound or do I need tube amp? Is there any benefit using tube preamp

 

[baronbeehive]

Would a good tube preamp to a solid state amp give a really good tube sound or do I need tube amp? Is there any benefit using tube preamp

It could do yes, but personally I don't think there is a need for preamps these days. Apart from imparting a tubey sound a tube preamp could cause problems with direct coupled amps if a tube were to blow which is something to consider.

 

[talan7]

Does anyone on here do mods for others? Let me know what you do and what you charge.