Want to step up from a Millet Hybrid
Mar 16, 2007 at 4:09 AM Post #17 of 38
I was under the impression that the M3 was the superior amp because it was supposed to take the concept of the PPA and improve it.

I've already got a TREAD on my Millett, so it looks like the PPA will be the one to build, unless the CK²III can hit well above it's weight.
 
Mar 16, 2007 at 6:30 AM Post #18 of 38
Quote:

Originally Posted by JWFokker /img/forum/go_quote.gif
I was under the impression that the M3 was the superior amp because it was supposed to take the concept of the PPA and improve it.

I've already got a TREAD on my Millett, so it looks like the PPA will be the one to build, unless the CK²III can hit well above it's weight.



The M3 in my opinion is superior in that is much easier to build & has a more robust design whereas the PPA could be a potential nightmare if you are not careful. Search the threads for the problems people have encountered. Once again, I don't believe one is sonically superior to the other just different. Possibly, if you have Sennheisers, you might pick the PPA over the M3.
 
Mar 16, 2007 at 7:31 PM Post #20 of 38
Quote:

Originally Posted by JWFokker /img/forum/go_quote.gif
That's good to know. And I'm more of a Grado fan as well.


Knowing this I would steer you towards the M³ as well. Again I would stress that your budget may need to be stretched, if you look at amb's site you'll actually find the spreadsheet that I did when the project started that lays out the rough cost of construction. Just parts and shipping could easily total $160 and you're still looking for a case and all the accessories.

Best of luck,

Nate
 
Mar 16, 2007 at 9:24 PM Post #21 of 38
I've got a spare humidor (I regularly use them for amp cases), a TREAD already built for my Millett, a ton of capacitors and various parts, so I may very well be able to do it for under $160. No sense in letting those Silmic II's sit around.

Thanks for the help, dudes.
 
Mar 17, 2007 at 12:23 AM Post #22 of 38
Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif
Yes, but C1 and C13 are electrolytics.


C1 and C13 aren't "in the signal path" per se. They're cathode bypass, and the amp would sound far worse without them.
 
Mar 17, 2007 at 3:42 AM Post #23 of 38
Quote:

Originally Posted by ericj /img/forum/go_quote.gif
C1 and C13 aren't "in the signal path" per se. They're cathode bypass, and the amp would sound far worse without them.


Signal goes right through them, this is discussed in quite a few threads. Yes amp would sound worse without them, but having the best possible caps in there will make it sound as good as it can. I've even seen designs with film caps bypassing these electrolytics.
 
Mar 17, 2007 at 4:16 AM Post #24 of 38
Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif
Signal goes right through them, this is discussed in quite a few threads.



Through them to where? Ground?
 
Mar 17, 2007 at 7:42 AM Post #25 of 38
Quote:

Originally Posted by ericj /img/forum/go_quote.gif
Through them to where? Ground?


Yes. Fallen Angel is absolutely correct.

One way to look at it is that the Anode (Plate) is always supplied with a much higher positive voltage. However, the signal voltage - which is carried through the grid - is necessarily AC, and so varies from positive to negative according to the frequency of the signal (music). In order for this to take place, the cathode portion of the tube has to "accept" the negative dips of the signal. So, a large part of the signal waveform is always somewhere between the grid and the negative ground, which passes through the cathode. When a resistor is applied to the cathode, some current actually flows from the plate, biasing the tube (Class A operation). A capacitor is used to "bypass" this resistor so that the AC portion of the signal passes through the capacitor, and the DC bias current is maintained through the resistor. Hence, cathode bypass.

The result is that a very small current and voltage exists through the capacitor, but it is almost all signal. In addition, the combination of the resistor (often just a trimmer) and the bypass capacitor forms an RC filter. So, the capacitance must be high to keep from losing the bass frequencies. This usually means an electrolytic, and a quality, even "boutique" capacitor is warranted.
wink.gif


EDIT: This is also the reason that so much DC is freely passed by vacuum tubes. Unlike solid-state circuits, which take DC separately and use it as amplification leverage, it's all superimposed in a tube circuit.
 
Mar 17, 2007 at 3:47 PM Post #27 of 38
OK - please bear with my ignorance here. I'm new to this. What did you do to get to this point? I just bought a PCB and want to start building an amp - how did you depart from (or add to) the BOM?
 
Mar 17, 2007 at 4:04 PM Post #28 of 38
Quote:

Originally Posted by JerryJ /img/forum/go_quote.gif
OK - please bear with my ignorance here. I'm new to this. What did you do to get to this point? I just bought a PCB and want to start building an amp - how did you depart from (or add to) the BOM?


That's the Cetoole revision for the Millett Hybrid Max:
New Millett Hybrid Layout at DIYForums.org
 
Mar 17, 2007 at 4:15 PM Post #29 of 38
So this is a different PCB entirely? In what way does the sound differ? I haven't finished reading the entire thread - I assume the boards are available. Does this outperform the PPA?
 
Mar 17, 2007 at 4:35 PM Post #30 of 38
Quote:

Originally Posted by JerryJ /img/forum/go_quote.gif
So this is a different PCB entirely? In what way does the sound differ? I haven't finished reading the entire thread - I assume the boards are available. Does this outperform the PPA?


Yes, this is an entirely new PCB design, by Cetoole. "Outperform" is a relative term. Strictly speaking, tubes may never "outperform" solid-state when it comes to measurements. However, this is somewhat similar to a tube-based PPA. The output stage is very nearly the same (solid-state Diamond Buffers). However, the PPA is opamp based in the primary stage and adds a third amplified virtual ground channel.

By comparison, Cetoole's Millett Hybrid Max also incorporates a STEPS-similar power supply on the board and an e12 delay circuit for the ultimate in convenience. It's still under prototype development, though. Everything works except the PS has a little hum. We're working on getting that fixed for the next round.
 
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