[SonicTrance]

Ive never seen a aftermarket 80x80x20 fan. Just get 25mm thick fans and mount them on the outside. Also get some taller feet to give them airflow.
Preferably you should use bigger fans for lower noise and higher airflow. I use 120mm fans. Then you'll need to cut the bottom cover though.

 

[SonicTrance]

I thought I'd make a post comparing the MK6 to my DIY project I've been building.
For the last year or so I've been experimenting and building @MrCurwen 's LTP design. It has been many ups and downs along the road but the amp is finally finished!

Granted, I've not heard many top dollar amps but this LTP is the best amp I've heard!. When comparing to the LD it practically blows it out the water. It's very resolving, transparent and non-fatiguing. The modded LD is also all of those things, but this is on another level! The LTP sounds cleaner, crisper yet very dynamic and real. The LD has a layer of dirt that the LTP don't have.

Tubes do only voltage amplification and cheap russian tubes sounds just as good as the premium audiophile tubes in this circuit!
All tubes have gyrator plate loads and CCS tails. B+ and B- are regulated.

Circuit goes like this:

Input LTP - grid drivers - output LTP - power buffer - OT/parafeed caps.

Schematics (@MrCurwen 's design):

Input stage:

Grid drivers:

Output stage:

Power buffer:

I can also share psu schems if someone is interested.

Pics of the completed amp:
Input stage:

Grid drivers:

Gyrators/CCS.

Output stage:

Power buffer:

Gyrators. I doubled up on their heatsinks in output stage as they need to dissipate about double wattage compared to input stage.

If someone wants to build this design we can start a new thread. I encourage people to build it. It sounds amazing!

 

[baronbeehive]

Fantastic Sonic, congratulations! Must be a great design of MrCurwen's.

That layer of dirt would be the NFB?

How much do you reckon it would cost?

Difficult to imagine any improvement on the SMLD but hey......

Edit: looks like there are 2 amps?

Has that design been implemented before now?

 

[SonicTrance]

Fantastic Sonic, congratulations! Must be a great design of MrCurwen's.

Thank you!

That layer of dirt would be the NFB?

Different designs. The LD needs feedback. This LTP does not.

How much do you reckon it would cost?

The parts alone are not that expensive. I have used all russian film caps, which are cheap. And just regular lytics. As the psu is regulated and doesn't fluctuate with the signal, cap quality doesn't matter as they're not in the signal. I have not calculated how much I've spent on it. Most expensive part is probably my Elma 4 pole 24 way attenuator.

Difficult to imagine any improvement on the SMLD but hey......

Yes, I felt the same way! The LD is still very good, of course.

Edit: looks like there are 2 amps?

One input stage and one output stage. I have two separate chassis because my initial plan was to only build an input stage and hook that up to the LD output stage. But plans changed and I ended up building the complete amp and left the LD as is.
If I was going to build again from scratch I would probably have both input and output stage in one chassi and a separate chassi for the psu. I could never fit everything in one case, unless huge of course.

Has that design been implemented before now?

What do you mean?

 

[baronbeehive]

That attenuator looks impressive, as does the whole amp I will leave the more technical aspects to others to comment on.

Excellent idea to separate the PSU chassis for noise isolation.

Could the input stage be bolted on to the LD then?

I meant, has this design been built by others, or just yourself?

BTW, does it still sound "tubey", what I mean is, is it liquid, and warm sounding, or just very transparent?

 

[SonicTrance]

Could the input stage be bolted on to the LD then?

Yes, you could build the input stage and connect it to the LD (output tube grid would be where you connect it)

I meant, has this design been built by others, or just yourself?

MrCurwen has obviously built it, and some others I believe.

BTW, does it still sound "tubey", what I mean is, is it liquid, and warm sounding, or just very transparent?

If by "tubey" you mean slow, warm and creamy? Then, no. It sounds fast, punchy and clean. Very non-fatiguing. You hear it's a tube amp though as clean as SS. No harsness or other fatiguing sounds!

 

[MrCurwen]

Pics of the completed amp:

Wow the work quality is so much better than anything I've ever done.

I'm a circuit design guy, not a chassis design guy, and these pictures sure drive the point home.

That layer of dirt would be the NFB?

Sonic's reply is correct, it's not the NFB, it's a combination of many things. Basically it's just distortion, LD produces more distortion even with NFB. The reasons for this have been written out in this thread.

I meant, has this design been built by others, or just yourself?

It's the same circuit that was inside the amp I linked a picture of here. Small black wooden shelf with two white chassis' (PSU & signal chassis) and black wooden open-top power buffer on top of the shelf. Different tubes only; Sonic didn't have space for directly heated tubes' filament supplies. TV sweep tubes (BEAM TETRODES, think about that, not even real triodes) are superbly linear though.

I've built it a number of times. One gentleman in Denmark has the schems and a lot of info, he wanted to build it to use with speakers only, but I haven't heard from him in some time.

My SE design is very similar in nature, but since it's much simpler more people have built it. One gentleman in Peru, one in South Carolina USA, one in Hong Kong. There may be others that simply built it from schems and never messaged me, I don't know.

BTW, does it still sound "tubey", what I mean is, is it liquid, and warm sounding, or just very transparent?

Sonic gave his comment, mine is more pedantic; if the recording has a warm and liquid sound, then a truely transparent amp will reproduce the warmth and the liquidness. If the recording doesn't have these things, a transparent amp will not reproduce these things.

I'm guessing you are using 'transparent' to mean "low THD achieved via soul killing amounts of NFB". I object to that; the common english meaning of 'transparent' would be what I explained above.

How much do you reckon it would cost?

Depends on how many FETs you burn during building and setup. Not kidding, they can easily make a serious dent in your budget.

Sonic went the elegant route with really good aesthetics, that increases cost. Also the stepped attenuator could be replaced with a 2.5 eur pot with not much harm.

The power buffer at the output is not necessary, it is basically for "best results only" builder. The amp sounds (in my opinion) extremely good without it.

The OT's in Sonics build are Hammond 125D if I recall correctly. My local shop doesn't carry them anymore (tragedy for me) but I paid 25 euros per piece for them originally.

All in all if you cut some corners the design can be simplified (cheapened) a lot without too much loss of HIGH END POINTS. This build Sonic made is the ultimate version.

 

[baronbeehive]

......

Sonic gave his comment, mine is more pedantic; if the recording has a warm and liquid sound, then a truely transparent amp will reproduce the warmth and the liquidness. If the recording doesn't have these things, a transparent amp will not reproduce these things.

I'm guessing you are using 'transparent' to mean "low THD achieved via soul killing amounts of NFB". I object to that; the common english meaning of 'transparent' would be what I explained above.

....

Sorry I was generalising after having used tube amps forever! Of course you are quite correct.

......

.... This build Sonic made is the ultimate version.

Sure looks like it to me .

 

[gug42]

Ive never seen a aftermarket 80x80x20 fan. Just get 25mm thick fans and mount them on the outside. Also get some taller feet to give them airflow.
Preferably you should use bigger fans for lower noise and higher airflow. I use 120mm fans. Then you'll need to cut the bottom cover though.

Ok sniff bad news

@ SonicTrance @MrCurwen https://www.head-fi.org/f/members/mrcurwen.442227/
Wow Impressive peace of works ! Wishes I have a such amp !
https://www.head-fi.org/f/members/mrcurwen.442227/

Other subjects about super moding Little Dot mkVI+ : Any one try to add some outpout transformers on the mkVI+ ?

 

[Maxx134]

Ah, tube electrode geometry! One of my most favourite subjects!

Hi! I been away and nice surprises here..
I like to ask what you think about silver plates.
I realize it too general question so to specify,
I found that for my 12sl7, I feel the silver plate gave me better treble and air.

It not seem to make sense as I thought black plates were best.
For instance, my raytheon & kenrad with silver plate sounded better than the black kenrad and also Sylvania wich seemed a Touch less resolving,
So i am just curious if the silver plate helped, or maybe the year produced instead.

Yes, generally admited that matched pair is under 10% of differences.
Thx

=> Internal mismatch can be more anoying than tube Left/Right mismatch

I believe the MK6 & MK8 don't have to worry as the tube configured in common cathode circuit so the triodes within the tube are forced to perform similar.

If someone wants to build this design we can start a new thread. I encourage people to build it. It sounds amazing!

Wow buddy how you keep all that majestic work from us?
Lol excellent work!
I like the choice of tubes!
So how much power we talking here?
How is the soundstage?

This build Sonic made is the ultimate version.

Thats what I would do...
If your going to do a project,
might as well go all in haha.

 

[MrCurwen]

I like to ask what you think about silver plates.
I realize it too general question so to specify,
I found that for my 12sl7, I feel the silver plate gave me better treble and air.

It not seem to make sense as I thought black plates were best.
For instance, my raytheon & kenrad with silver plate sounded better than the black kenrad and also Sylvania wich seemed a Touch less resolving,

Material of the anode has 0.0% effect on sound quality, in any audio circuit.

It has an effect on longevity; different metals (or rather metal compositions) react differently to heat, some expand more than others. Also different metals store different amounts of residual gas; this gas is trapped inside the metal while the tube is constructed. Then it is released when the anode is heated during normal operation. This gas then disrupts the normal operation of the tube by attaching itself to either the grid or the cathode, changing their chemical composition, and thereby altering their electric behavior. This is normal ageing of the tube, leading to eventual end of life.

Some anode materials trap more gas than others. This effects tube reliability and lifetime, but not sound quality (while the tube is young in hours operated).

Two main routes of tube wear are

1) heat expansion warping the elements

2) gas damages.

So i am just curious if the silver plate helped, or maybe the year produced instead.

The silver plate had no effect. The production year could have had an effect. Linearity is determined by tube geometry, construction and alignment of the electrodes, i.e. how regular is the grid wire pitch etc.

So how much power we talking here?

Into a 4 ohm load (speakers) about 0.5W RMS, enough to fill a decent sized room to deafening sound levels with normal sensitivity speakers. Power is not an issue for headphones with any amp really, I think.

I believe the MK6 & MK8 don't have to worry as the tube configured in common cathode circuit so the triodes within the tube are forced to perform similar.

Forced by what? There is 1.5 k ohms of impedance in the tail, let's say 250k to 350k impedance in each branch above the tail. What is the dominant component, is it the tail?

I like the choice of tubes!

Even the beam tetrode?

 

[gug42]

Hi! I been away and nice surprises here..
I like to ask what you think about silver plates.
I realize it too general question so to specify,
I found that for my 12sl7, I feel the silver plate gave me better treble and air.

It not seem to make sense as I thought black plates were best.
For instance, my raytheon & kenrad with silver plate sounded better than the black kenrad and also Sylvania wich seemed a Touch less resolving,
So i am just curious if the silver plate helped, or maybe the year produced instead.

Well from your local expert : for a same brand, it's more a matter of factory, production line and quality control ...

I believe the MK6 & MK8 don't have to worry as the tube configured in common cathode circuit so the triodes within the tube are forced to perform similar.

Sorry ... I did'nt understand ... perhaps my english ... perhaps my knowledge

 

[SonicTrance]

Wow the work quality is so much better than anything I've ever done.

I'm a circuit design guy, not a chassis design guy, and these pictures sure drive the point home.

Thanks! Really appreciate it!

Depends on how many FETs you burn during building and setup. Not kidding, they can easily make a serious dent in your budget.

I've learned this the hard way! Ha!

The power buffer at the output is not necessary, it is basically for "best results only" builder. The amp sounds (in my opinion) extremely good without it.

I agree it sounds great without the buffer. But I noticed a cleaner sound with the buffer so I wouldn't cheap out on that. Just my opinion.

Also the stepped attenuator could be replaced with a 2.5 eur pot with not much harm.

Remember you need a balanced 4 pole pot. They are usually stereo so you'd need one for each channel, which is a pain. Maybe there's cheap balanced pots, I haven't seen any? The pot could be completely taken out though, replaced by some resistors and then adjust volume digitally.

Lol excellent work!
I like the choice of tubes!

Thanks, Maxx!
Yes, I experimented with some different tubes and ended up with this combo. The input stage takes either a pair of 6SN7's or two pairs of 6C5G/6J5G (with 20min of soldering it can take any input tube you wish, within limits of course)
Output stage takes two pairs of 6BG6's or 6P7S's (pictured). I also experimented with EL36's which sounds just as good but I chose the bigger ST bottles as they're nicer looking, ha!

You may notice I have a empty socket in the middle of both stages. That's where the rectifier tube would go. I wanted to use a rectifier tube only for aesthetics. A rectifier tube will not have any impact on sound when followed by a reg as the voltage is constant and doesn't fluctuate.
I had severe oscillation problems and it turns out the rectifier tubes caused 95% of that oscillation for some reason. Which does not make much sense but I now use UF4007 diodes instead and oscillation is gone!

How is the soundstage?

Compared to the LD I'd say it's wider and more realistic. As you know I'm kind of awful at describing sound with words. You really need to hear it!

 

[MrCurwen]

I agree it sounds great without the buffer. But I noticed a cleaner sound with the buffer so I wouldn't cheap out on that. Just my opinion.

My whole design came out of the necessity of not wanting to buy expensive parts (especially OTs)! I am very cheap! I don't buy tubes that cost over 4 or maximum 5 euros per piece, I prefer tubes that cost 3 euros per piece.

Thus far there are two functioning builds of the whole things (with output buffer) and neither of them is in my own use. There are more builds without the output buffer. I really need to build one for myself also, I enjoyed the output buffer as well.

But, it is not necessary for superb high end audio. I bring this point out to lower the threshold for inexperienced builders; leaving the buffer out simplifies things, think about PSUs etc. It is possible to add later also.

People who are not cheap like me, can also try buying better OTs. Once you have the output buffer there, OT quality is not important, but without it, you can improve sound by simply spending money on a better OT.

Remember you need a balanced 4 pole pot. They are usually stereo so you'd need one for each channel, which is a pain. Maybe there's cheap balanced pots, I haven't seen any? The pot could be completely taken out though, replaced by some resistors and then adjust volume digitally.

Yes of course for balanced DAC output. I'm thinking about SE sources all the time. For SE input you can just use an Alpha double pot, but I do believe they cost more than 2.5 eur nowadays.

Compared to the LD I'd say it's wider and more realistic

Distortion masks microdetail. Lower (open loop) distortion -> more detail, larger soundstage.

 

[gug42]

I'm a total newbe about amp conception, but well I'm really curious why anyone try to add outpout transformers to the mkVI+ ?
For some people it is the only "flaw" of the mk6 ?