[SonicTrance]

I updated first post with final pics of version 2.

 

[iTsCraig]

I updated first post with final pics of version 2.

well done on an extremely good looking AMP
I am glad to hear it sounds good

 

[SonicTrance]

well done on an extremely good looking AMP
I am glad to hear it sounds good

Thanks!
I’m glad you like it. Appreciate the feedback!

 

[MrCurwen]

That's a beautiful amp, inside and outside!

Do those dampers work? Do you have bad microphonics without them?

It is common that directly heated tubes have some microphonics, but usually it's very mild. One amp I built (with 4P1L) had a strange condition - if the music played had a big transient, that transient would cause a kind of an echo. Not repeating, but kind of like a sustain effect. With headphones no less! This would stop if you changed the tubes or damped the offending tube enough. I guess the filament was just kind of loose on that tube.

 

[SonicTrance]

That's a beautiful amp, inside and outside!

Thanks!

Do those dampers work? Do you have bad microphonics without them?

I can't tell you if they work or not as my tubes are not microphonic. I think they look cool, that's why I got them!

 

[Maxx134]

That's how I see output transformers, an old flawed methodology . As I mentioned in the other thread, a voltage follower buffer by definition will skew the current through the transformer due to its inductance, I think if you are going to stick with a transformer output then driving it with an active current source buffer instead would perform better because it will ignore all parasitics thanks to Kirchhoff , after all a transformer is run by current, not voltage.

But then it would be in thw signal path, right?
Then it would be a hybrid design no?
I would not want that.
Why?
I still notice with both hybrids, and fake hybrids (buffer tube stage), and solid state amps... A problem.

Problem is that they all still cannot convey as much 3 dimensiomal space as good as a tube amp..
I feel This issue is hidden with speaker amps because the room will make up the soundstage.
But when having headphones on you get to hear the true nature of amp without room and speakers to add to it.

So the amps with poor soundstage are revieled with headphones...
and so I can also see how MrCurwen states the use of paralleded tubes can blur the details.

Using the topology described in this thread you can achieve top results using only a cheap OT...

I would not have believed this if I didnt witness this myself on my mini amp.

It is using tiny
Japan Z11 EI48 24 Output Transformers ,

And the huge 6bg6 tubes troide strapped ha.
It is also using a switching PSU which is interesting, and I habe noticed the SS TO-220 transistors before the driver tube which indicate to me a similar approach in using new design.

So now with the positive experience of this mini amp I am very convinced in these New approaches, instead of older & expensive designs.

 

[Maxx134]

featuring 6C8G input and 47 output

Hey SonicT, what was your reasoning on the 47 tube?
I see there is also the 46 tube and the 71A tube and the 6A4 tube,
All being like the 47 as a lesser cost alternative.

I know you have very similar taste as me in tubes and I also love the 6C8G as driver tube, but that was in our LittleDot amps which (like most tube amps) is prone to tube rolling differences to get best sound...

I need to look further into the output tube choice,
as I was heavily under the impression that the 45 and 2a3 was best and the 300b most linear..

I had my mind set on a totally different design but am glad I waited a year to see your project first...
If (when) I go for next project I am heavily leaning on your (MrCurwen) topology,
But would still would like to implement some change like an autoformer for volume, if not too expensive.

Anyways, I would like anyone's input on the DHT output tube choices..

 

[MrCurwen]

Once again, everything is in the signal path.

At least everything you can 'hear', meaning everything that has any amount of effect on the sound quality (or, in the case of not-HIFI, tone) of the audio output.

So, I really don't understand this "it's in the signal path" thing. What use is it to ask that? If changing some part of the amp has absolutely no effect on sound output quality, why discuss it? If it does, it's in the signal path.

Problem is that they all still cannot convey as much 3 dimensiomal space as good as a tube amp..

Sonic do you have a comment for this?

As an aside, I have never heard the term "fake hybrid" before. Please elaborate.

So the amps with poor soundstage are revieled with headphones...
and so I can also see how MrCurwen states the use of paralleded tubes can blur the details.

Indeed. Parallel caps also, but this is highly context dependent.

I would not have believed this if I didnt witness this myself on my mini amp.

Interesting. So it's a SE parafeed amp?

So now with the positive experience of this mini amp I am very convinced in these New approaches, instead of older & expensive designs.

Maybe I'm cheap but I cringe thinking about the cost of one build of the scheme described in this thread. I'm always finding ways to try and cut corners and make it cheaper.

Indeed with only a few changes it's possible to achieve 92% of the sound quality with significantly lowered price.

I see there is also the 46 tube and the 71A tube and the 6A4 tube,
All being like the 47 as a lesser cost alternative.

71A as a LESSER cost alternative to the 47? I must've misunderstood or times sure have changed from my tube buying days. I came to the 47 because I got tired of trying to find affordable 71A's for my amps.

I need to look further into the output tube choice,
as I was heavily under the impression that the 45 and 2a3 was best and the 300b most linear..

Again, 4P1L is the undeniable king of DH tubes. And also king of all tubes in it's mu and rp area. Only reasons to use american tubes are

1) aesthetics

2) you are building a recreation of a classic amp, i.e. aesthetics.

Not to say you can have first class results with them also; the 47 was after all ranked almost as low THD in the distortion benchmark I linked way back.

But would still would like to implement some change like an autoformer for volume, if not too expensive.

What is your objective with the autoformer?

In any case, the volume pot / stepped attenuator is basically a non-issue. There is really zero audio gains to be made there. I don't hear any difference in sound quality between using an Alpha pot (yes, the guitar amp kind) and precision fixed resistors (unadjustable attenuator). If you have a balanced input (XLR) then stepped attenuator is more handy. Otherwise just go with the Alpha pot.

Anyways, I would like anyone's input on the DHT output tube choices..

1) Don't go DHT.

2) If you go DHT, use 4P1L.

3) If you have a specific aesthetic in mind, go for 33 or such. 47 if you simply must have big bottles. 2A3 is for suckers, 45 is too expensive and 300B is just pointless (although very pretty and linear).

With big current DH tubes you are just digging a very hot hole for yourself. Unless you MUST have DH tubes, just don't.

The sound quality difference is quite metaphysical in nature. Meaning you must really hard believe that you are hearing it to really hear it. It's not a "night and day" thing.

With some amps it can be, I know. Not with this one. The 6P31S version has "DHT sound" already built into the schematic.

Just go with the TV sweep tubes. I myself think they're pretty.

 

[SonicTrance]

Hey SonicT, what was your reasoning on the 47 tube?

It was recommended to me by MrCurwen as he knows I like big bottles. I just wanted to build this amp using DH tubes and wanted to use globe tubes as I like the look.
The 71A has much smaller envelope, so is not as impressive looking It's also a triode rather than a pentode. Not that it matters.

I know you have very similar taste as me in tubes and I also love the 6C8G as driver tube, but that was in our LittleDot amps which (like most tube amps) is prone to tube rolling differences to get best sound...

The 6C8G was chosen for two reasons;

1: It has µ36 which is perfect for this amp as I need more gain than the 6SN7's µ20 for driving speakers.

2: Aesthetics, it just look sweet with the ST bottle and top grid cap! Also quite affordable still.

Anyways, I would like anyone's input on the DHT output tube choices..

You can use any linear tubes you want and it'll sound fantastic! If you build with the output buffer you can also use output tubes with high rp, if not then preferably use output tubes with low rp. Remember, if you look at datasheets for a pentode it will list a very high rp. You need to look for the triode curves for that tube!

Sonic do you have a comment for this?

Not really, no.

Again, 4P1L is the undeniable king of DH tubes. And also king of all tubes in it's mu and rp area. Only reasons to use american tubes are

1) aesthetics

2) you are building a recreation of a classic amp, i.e. aesthetics.

Not to say you can have first class results with them also; the 47 was after all ranked almost as low THD in the distortion benchmark I linked way back.

This^^
Aesthetics is very important to me. So is SQ of course. I want the best of the two! I'm very happy with my choice of tubes. Though, the DH tubes each require a separate PT (winding) and their own reg. So it dramatically complicates the build! That being said, I have no regrets!

 

[Maxx134]

As an aside, I have never heard the term "fake hybrid" before. Please elaborate

Yeah sorry thats just my own opinion of some equipment that use tube for the sake of having it,
while not even having it implemented to perform any useful amplification.
Its not a real term just an observation.

71A as a LESSER cost alternative to the 47?

Yes my mistake I really need to do more research into these tubes .

) If you have a specific aesthetic in mind, go for 33 or such. 47 if you simply must have big bottles. 2A3 is for suckers, 45 is too expensive and 300B is just pointless (although very pretty and linear).

That's some real advice! much appreciated thanks.

 

[Maxx134]

Aesthetics is very important to me. So is SQ of course. I want the best of the two! I'm very happy with my choice of tubes. Though, the DH tubes each require a separate PT (winding) and their own reg. So it dramatically complicates the build! That being said, I have no regrets!

The more I looking at your tube choices,
the more I see myself liking your choices.

I have same exact preference as I have same driver tubes in my littleDot now.

I have to start planning lookiing into chassis style lol.

In really like the implementation of your
Chassis setup,
as it remind me of the Woo Wa33 which I also heard ..

Both the Woo Wa33 and the Eddie Current Studio which I heard,
are both using 2a3 tubes,
and its so funny to me when reading what MrCurwen stated here about the 2a3 is for suckers lol.
It definitely makes the amp more sellable.

Both of those amps, I heard,
and they have a characteristic large powerful soundstage but I do not care for 2a3 and also think it is more for aesthetics and popularity while being expensive.

 

[SonicTrance]

The more I looking at your tube choices,
the more I see myself liking your choices.

Yes, they are good choices!

However, you would get pretty much the exact same gain if you used triode strapped EL36's instead.
Superbly linear tube.

In really like the implementation of your
Chassis setup

Yes, separate psu chassis seems to work very well!

 

[baronbeehive]

Wonderful work Sonic!

I agree that P2P must simplify enormously any problem solving you need to carry out. The whole thing looks complicated this way but as you say some form of modular construction lies behind all that mass of wiring fortunately lol!

I just had part of the trace come up during a repair but managed to circumvent that. I'm still trying to fix my LD!!!

 

[Maxx134]

I just had part of the trace come up during a repair but managed to circumvent that. I'm still trying to fix my LD!!!

I in same boat I have to check my socket pins for a cold solder joint that opens with tube heat 2min into playing music .
Just didn't have time to fix.

LD amp was a great learning experience for me and more a sentimental value but like Sonic I ready for another project.

You should post your current issues in the LD thread .
Merry Christmas guys.

 

[SonicTrance]

Wonderful work Sonic!

Thanks, baron!
So, when are you starting to build this amp?