Ciao Domenico,
thank you for your posts.
Please give a look to my post #1373, it was my interpretation of what I read about connecting the supercap. So you confirm it was right. It cannot work because the dc feedback doesn't sense the midpoint of output transistors: the diamond buffer is not within the ring.
I never heard the sound of the NHB-108, no the true original one, nor the chinese clone because I heard mine only once modified. I must say I love it. No lack of bass at all, it has 11 couple of output transistors and 12x6.8mF capacitors a channel.
About the "Melius Finale" you posted: Interesting design but it has a total feedback loop, that is out from my scope. It seems to have the base of the "Hitachi Amplifier" design (that is a good starting point idea), highly improved here: nothing is missing and the components are high quality ones.
When I was desperate because the fake transistors, I got on eBay, didn't allow my NHB-108 to work, I bought a couple of LJM L20 V9.2 and a couple of L20 V10. They are far different from each other being the V9.2 an elegant (almost) design and V10 a sloppy (very sloppy) one, but they sound the same. Why? I think because of the total feedback loop.
In my chain I don't have any equipment with total feedback loop, my tube and hybrid designs have no feedback at all but the local "on stage" ones. I got used to the no-feedback sound, in Rome I have two cross-coupled 2x10W and 2x20W tube amps, partial designs of mine, biamping two B&W801: basses are a little long but voices are outstanding, even with ultra-linear cirtuitry. The preamplifier is a hybrid design of mine, name "WOTS", a 6H30 followed by a mosfet buffer, both working in high current, with a double "Virtual Battery" 130V PSU. Months (perhaps some years) after I published the WOTS in internet, CHF published something very similar in the magazine. Here in Utah, as a preamplifier, I have an Aikido (all tubes) with a tube rectifier and double Virtual Battery 300V PSU.
So I want to avoid feedback in my designs. The WHA-217 (I had to rename it adding 1 becasuse 216 is 6^3, a devil's thing) is the one equipment of mine having a feedback over stages. With transistors, you have to use some feedback in voltage gain stages.
What I had to put to work were: 2 2x50V 625VA toroidal transformers by ICES-EBM (made when they were an artisan craftsmen firm) and 25 couples of MT200 Sanken. Here is why I used the NHB-108 base. But it could be changed for a better one.
What I still need to put to work is a 2x60V 1KVA (if I remember well) transformer that is in a smoked Adcom GFA585-SE. I didn't like its sound, despite very good reviews about it, so I don't want to repair it and reuse its transformer and, hopefully, its cabinet too. But it is a long term project, perhaps the only bufer stage in the Adcom cabinet and an Aikido, used as a VAS, placed in another cabinet.
Switching PSU could be a solution to try. In order to keep me fit, I assembled a Quad 405 clone with a switching PSU. I don't like its sound too much and I don't know where to put the blame on, the 405 or the PSU. Pehaps I have to remove the 8x4.7mF capacitors I put after the PSU.
Not always David beats Goliath!
I don't know the Holton 500, however, the 1300 (@100Hz) declared damping factor, with only 4+4 output pairs, means a feedback loop is present from the speaker output. It would be interesting observing the damping factor @20KHz. The NHB108 has no feedback loop from the speaker output and has only one output pair. The measured DF is around 30 (bass) to 23 (treble), which is not too bad at all. But, still, you can compare these two amplifiers only at low volume with easy speakers.
I don't like too much the sound of an amplifier with the feedback loop from the speaker output, more or less, if their designs are good ones, they all sound the same; the only partial exceptions are those few designs whose open-loop bandwidth is at least the double than the audio bandwidth (but, if I am able to design with that wide bandwidth - tubes only - I won't apply for any FB).
I chose the NHB-108 as a base for my WHA-217 because of the absence of the speaker FB loop. You could extend your's with the NSCB final stage, this will not increase the expected maximum power, but will be able to drive even your iron. This David can beat Goliath!
I don't know the Holton 500, however, the 1300 (@100Hz) declared damping factor, with only 4+4 output pairs, means a feedback loop is present from the speaker output. It would be interesting observing the damping factor @20KHz. The NHB108 has no feedback loop from the speaker output and has only one output pair. The measured DF is around 30 (bass) to 23 (treble), which is not too bad at all. But, still, you can compare these two amplifiers only at low volume with easy speakers.
I don't like too much the sound of an amplifier with the feedback loop from the speaker output, more or less, if their designs are good ones, they all sound the same; the only partial exceptions are those few designs whose open-loop bandwidth is at least the double than the audio bandwidth (but, if I am able to design with that wide bandwidth - tubes only - I won't apply for any FB).
I chose the NHB-108 as a base for my WHA-217 because of the absence of the speaker FB loop. You could extend your's with the NSCB final stage, this will not increase the expected maximum power, but will be able to drive even your iron. This David can beat Goliath!
I don't think i would enjoy your Dartzeel either. Neither the input resistor, nor the parallel outputs make it better where it really shines: at low power into easy loads. Once you exceed about 5W the distortion goes through the roof and the magic evaporates. In a big room i would not expect much.
The only Holton amp i have heard was from his commercial line and was absolutely great. At any decent power it would eat a Dartz for breakfast. No idea how good are the diy modules.
The only Holton amp i have heard was from his commercial line and was absolutely great. At any decent power it would eat a Dartz for breakfast. No idea how good are the diy modules.
@Marigno
well, if you decide regardless for an open loop power amp or low / no loop feedback, the options you have are lower than a traditional scheme, even if optimally set and cared for and very well sounding, such as Spectral 260 whose scheme is at about the one I posted.
then if you love the sound of 108, if I have read correctly, then that is the way
well, if you decide regardless for an open loop power amp or low / no loop feedback, the options you have are lower than a traditional scheme, even if optimally set and cared for and very well sounding, such as Spectral 260 whose scheme is at about the one I posted.
then if you love the sound of 108, if I have read correctly, then that is the way
I add, we don't always think like audiophiles, considering regardless that a WELL DONE switching power supply sounds bad or worse than a traditional one.
If WELL DONE, it means that it does not radiate, a switching does not have transformers that can vibrate or even emit dispersed flows, it is stabilized and it is very quiet, always if WELL DONE it can be positioned close to the amplifier boards.
So, to understand each other, it is necessary to say which traditional power supply you compare it with and, above all, which switching you are talking about, because if grabbed by a friend who knows a lot, then better gloss over.
Instead if you try with an industrial switching ................... well .......
it's a bit of an audiophile-only story that as current generators the best are the resistors and, to follow, the usual transistor
If WELL DONE, it means that it does not radiate, a switching does not have transformers that can vibrate or even emit dispersed flows, it is stabilized and it is very quiet, always if WELL DONE it can be positioned close to the amplifier boards.
So, to understand each other, it is necessary to say which traditional power supply you compare it with and, above all, which switching you are talking about, because if grabbed by a friend who knows a lot, then better gloss over.
Instead if you try with an industrial switching ................... well .......
it's a bit of an audiophile-only story that as current generators the best are the resistors and, to follow, the usual transistor
I don't like the NHB-108 sound for the simple reason I never heard it. I only connected the board to check if it was alive or not. Then I added the NSCB stage. This is the sound I like.
This is the eBay link to the switching PSU I'm using to power the Quad405 clone.
1000W +-50V LLC Soft Switching Power Supply / amplifier PSU board L3-83 | eBay
I asked the seller for some more information but they don't have any. I connected it to a board of 8x4.7mF.
I compare it with the simple transformer-Bridge-capacitor PSU being its transformer VA 1.7 times the Wrms of the class B amp, assembled with good quality components and a total capacitance as big as possible.
I should try such a PSU with a good amp board but I'm not a "research audio group". What I can say is that I think this PSU connected to the 405 clone is not a good solution, with ot without the added capacitors board.
Finally I totally agree with you, I don't like CCS and, when possible, I prefer to use resistors in place of them and I like designing with BJT too.
A short off-topic, two designs of mine, demonstrating the use of resistor (R1, R10/11, R13, R21) used instead of CCS, with their value as low as possible, to maximize the current in their stages. The sound of both is very close and outstanding, not in my opinion, but in the opinion of a lot of people after listening at them. The distortion is written in the circuitry to be not that low!
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I didn't think about the CCS as IC, I was referring to the ones made with discrete transistor and diodes. I never used a CCS component, because all of them are too low in operation voltage for my designs. That's why I prefer a resistor.
I have a lot of H&B carbon resistors. Pure crap! You measure, then you move and bend the leads, in order to adapt them to the assembly, measure again and the value is far different. I have never used one of them. And never dared to use carbon trimmer, who can trust them?
About power supply: I am used to stabilize the voltage with a "Virtual Battery" circuitry in order to power-up gain stages low power circuitries as preamplifiers. If you want to use a stabilized PSU with a power amplifier (a high power one), the one acceptable solution, nowadays, would be the switching PSU.
About regular PSU on a power amp: did you ever tried the inductive circuitry? Transformer-bridge-inductor-capacitor, being the inductor a big piece of iron (high current, has the gap). I didn't, that's why I'm curious.
For the next future, I confess, I look forward to listen an all-switching "NCore Hypex".
But, for now, I have to settle with my NHB-108 interpretation, being the WHA-217, that performs very well, over my expectation. It has been playing for almost a month, it is very stable, does not generate any listening fatigue, gives the thrill even with male voices. I'm happy but never satisfied, just how we Audiophile are.
I have a lot of H&B carbon resistors. Pure crap! You measure, then you move and bend the leads, in order to adapt them to the assembly, measure again and the value is far different. I have never used one of them. And never dared to use carbon trimmer, who can trust them?
About power supply: I am used to stabilize the voltage with a "Virtual Battery" circuitry in order to power-up gain stages low power circuitries as preamplifiers. If you want to use a stabilized PSU with a power amplifier (a high power one), the one acceptable solution, nowadays, would be the switching PSU.
About regular PSU on a power amp: did you ever tried the inductive circuitry? Transformer-bridge-inductor-capacitor, being the inductor a big piece of iron (high current, has the gap). I didn't, that's why I'm curious.
For the next future, I confess, I look forward to listen an all-switching "NCore Hypex".
But, for now, I have to settle with my NHB-108 interpretation, being the WHA-217, that performs very well, over my expectation. It has been playing for almost a month, it is very stable, does not generate any listening fatigue, gives the thrill even with male voices. I'm happy but never satisfied, just how we Audiophile are.
in my opinion the NON SENSE of the various audio feeds is to make them floating:
they are bulky, expensive and not very efficient and depend a lot on the filter cell cap.
A stabilized power supply, let's talk about the final power stage, is another story.
Then there is, in fact, the switching power supply.
But, switching and stabilized are defined regardless, by audiophiles, bad sounding, mah
they are bulky, expensive and not very efficient and depend a lot on the filter cell cap.
A stabilized power supply, let's talk about the final power stage, is another story.
Then there is, in fact, the switching power supply.
But, switching and stabilized are defined regardless, by audiophiles, bad sounding, mah