I don’t think a preamp can reduce or cancel out H2 generated in the main amp (no matter whatbphase it is in). The power amp generates more positive H2 on top of the input H2 of the preamp - shows up as more H4 out of the ACA. There is no feedback here so distortion just grows and is additive.
Try it on the sim. Perhaps others who tried ACA with B1 Nutube or BAF2018 H2 board can also chime in.
It does? Where did you find that information...? I think you are referring to the Korg NuTube B1. (And also a bridged ACA has plenty of neg. phase H2
)The SSII has selectable plate loading, either a resistor or a CCS, the resistor sounds perhaps a bit more “tubey” but I wouldn’t really charactize this as having lots of tube sound. With the CCS it’s a touch cleaner and does clip a bit harder, although with either load the distortion is pretty close to the bottom of what I can measure until it starts to clip. The conjecture above that it produces 1-2% is frankly wrong.
As a linestage I think most users are going to be incredibly happy with it, the sound is very clean, very musical, very delightful. I’d happily use it as my only preamp if I didn’t currently have 4 preamp projects.
As a headphone amp everything said above holds true as well, it can easily drive impedances from Grados all the way up to Sennhiesers, as well as planars and other of the ‘difficult to drive’ headphones.
It’s a great kit, the chassis turned out really, really well, and the first batch is sure to sell out as soon as it’s opened up.
Last edited:
Perhaps others who tried ACA with B1 Nutube or BAF2018 H2 board can also chime in.
I have all those circuits you list. The H2 widget and the NuTubeB1 are both additive to whatever you connect it to downstream. The NuTube + ACA gets a little dreamy and vague together, but some people will love that sound.
Where the NuTube really shines is in front of a pedestrian class-AB amp - it really changes the character for the positive ( by making the harmonic phase negative...lol ) and makes the tone absolutely beautiful! It’s a circuit that everybody should have so that can try it and see what neg. Phase H2 is all about.
Last edited:
Lovely project, no doubt! I object to the name, as it (for me at least) has this subtle (or not so subtle) hint that it could be better, but it is kept 'cheap' for 'starving students'. It may just be me, but the name implies it's really not that good, but 'good enough' for starving students. I hope this is just a case of poor wording, rather than actual facts .
With that out of the way, for some of us that have never had the pleasure of listening to Tubes, this may very well be the entry point to that 'other' world to have a taste of it.
That said... I think you nailed it here with this statement:
I know part of the charm is just building stuff and not always having the best sounding equipment, but there is a limit to what wives allow us to put in the house!
So I'm intrigued, as someone that has already built and love the WHAMMY, if this would provide either a significant upgrade or at least a significant lateral move to invest the time for this project and move it to the top of the list... or will it be a little less good overall and be more of a nice project to build rather than a 'better' end product.
And then there is the ultra-practical approach: for someone wanting to get a grip of how tubes sound, how would this new project compare with market options like the Schiit Vali, which I almost bought just to get an idea of tube sound.
I know you mostly object to giving subjective opinions (which I applaud and is one of the many reasons I admire you), so any feedback, either technical or as subjective as you are comfortable being would be very much appreciated.
Schematics and specs like gain and impedances would just be icing on the cake
Big hug,
Rafa.
.With that out of the way, for some of us that have never had the pleasure of listening to Tubes, this may very well be the entry point to that 'other' world to have a taste of it.
That said... I think you nailed it here with this statement:
So, keeping in the DIY world... how would this stand up to the WHAMMY for instance (in terms of pure Headphone AMP or as PRE for the ACA)?
I know part of the charm is just building stuff and not always having the best sounding equipment, but there is a limit to what wives allow us to put in the house!
So I'm intrigued, as someone that has already built and love the WHAMMY, if this would provide either a significant upgrade or at least a significant lateral move to invest the time for this project and move it to the top of the list... or will it be a little less good overall and be more of a nice project to build rather than a 'better' end product.
And then there is the ultra-practical approach: for someone wanting to get a grip of how tubes sound, how would this new project compare with market options like the Schiit Vali, which I almost bought just to get an idea of tube sound.
I know you mostly object to giving subjective opinions (which I applaud and is one of the many reasons I admire you), so any feedback, either technical or as subjective as you are comfortable being would be very much appreciated.
Schematics and specs like gain and impedances would just be icing on the cake
Big hug,
Rafa.
Last edited:
Exactly. Both the H2 widget and NuTubeB1 set at default pos phase H2 I presume. The opposite effect will happen when a stage which produce neg phase H2 is connected to the ACA. At 48V, the 18FX6A in SSII will produce a small amount of neg phase H2 and almost nothing else, I'm quite certain it will sound terrific with the ACA.
It's no secret that I've been raving about how good the ACA sounds with the AKSA Lender preamp, but still, I can't stop thinking about one occasion when my ACA sounded absolutely gorgeous. That was before I built the AKSA Lender and when I was still using a B1.
On that fine afternoon, a friend came over to my place for a listening session and brought along a headphone amp from XRK. We hooked it up as preamp to my ACA and I was completely blown away with the bestest, sweetest and most musical sounds I've ever heard. Admittedly, I don't know enough to describe in detail what I've heard, but I guess it could have been H2. Maybe X would be able and willing to describe what is so special about the sound, seeing that it is his preamp.
On that fine afternoon, a friend came over to my place for a listening session and brought along a headphone amp from XRK. We hooked it up as preamp to my ACA and I was completely blown away with the bestest, sweetest and most musical sounds I've ever heard. Admittedly, I don't know enough to describe in detail what I've heard, but I guess it could have been H2. Maybe X would be able and willing to describe what is so special about the sound, seeing that it is his preamp.
Last edited:
It must be catching - I have to finish my WHAMMY and an HP-1 at some point, although one of the parts for the latter is o/s until October (!) so there'll be plenty of time for an SSII.
Reading through the Assembly Instructions & Manual, there's a typo in the section on testing: looking for 19V between pin3 of each valve and ground "you can find ground on pin3" should read "pin4"?
That would have been the Pocket Class A headphone amp that Twocents brought over. That HPA/preamp is a SE Class A MOSFET source follower with a BF862 n channel JFET input stage with local feedback. It produces a lovely sound that is H2 dominant and descending higher orders of harmonic distortion as is typical of SE Class A. THD is in range 0.05% driving loads as low as 250ohms.
As I have not been able to find a schematic of the SSII yet, but based on 6L6’s statement that 1-2% is wrong, I will retract my estimation until I can see the circuit. If it has a CCS, probably will be much lower in similar 0.05% THD and as low as 0.002%. But depends on how the tube is handled as that is the H2 and THD generator.
But it is true that adding a sweet sounding pre with higher H2 distortion to a SS amp can make it sound very sweet.
Correct X, that is the HPA that Twocents brought over to my place. And following on from my post yesterday, we've decided to have a second listen to that combination.
Thanks for the sound description. I can't wait to hear it again.
PS I didn't know there was a thread on diyAudio. Thanks for the link.
Look again for the mosfet source resistor... it’s the tube’s filament.
Elegant bit of engineering there, and works beautifully.
That is clever and elegant but I wonder what the effects of the feedback of the audio output current is going to be on the filament current, which controls the tube’s supply of vacuum path electrons? Perhaps the thermal time constant is too slow to matter.
In case you didn’t know, there is also a desktop version of the PCA HPA, all through hole and with higher bias current and performance. Built in cap Mx and CRCRC PSU too.
xrk971 Desktop Class A (DCA) Headphone Amp
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.