Thai Tao

Hi, What's the current stable gerber file for CFA2? There is too many version in the google folder. Thanks!

Thanks, i will study the schematic more

Hi Kelvin, If i understand the schematic correctly, the CFA2 will have quite high open loop gain right? The CFA3 although output stage doesn't have gain like other buffer, it still wrap around the input stage which is also high loop gain so the zero feedback here only apply for the current buffer, right? My point is if really need that high current gain, then change the first mje15030 to pzta06 we will have current gain x5 in worst case ( 20 vs 100 ), and if we continue to the second mje15030, we will continue to get another x5 current gain and the pzta06 will still be able to handle 20ma bias. Or is the reason is we need thermal couple? Thanks!

hi @kevin gilmore, may i ask why there are 3 emitter follower at the output stage? I think it's just too waste silicon when only the outer most pairs do the heavy lifting. Instead can we just change to 2 emitter follower with the first one use small transistor like bc546 or mpsa06 so we can take advantage of high hfe to have high input impedance and the last one use mje15030 to do heavy work?

Hi all, I'm planning to order some board, do you guy think gold immersion and 2oz copper thickness make different in sound compare to HASL and 1oz?

Sparkoslabs make solid stuff with very detail document. Amb o78/o79 implement tps7a4700/3301, the sparkoslabs output noise is 3uV at 5v compare to 4uV of tps7a4701, 16uV of tps7a3301, PSSR wise, the sparkoslabs win completely at 120db compare to 80db of 4700/3301.

I found these picture of the Liquid Crimson https://www.head-fi.org/threads/new-cavalli-audio-liquid-crimson-amp.737694/page-14#post-14019045

so spice indicate at least 0.02% thd at 300ohm, real world measurement must be worse, can't understand their spec 0.0014% at 50ohm but at the same time i dont' believe some big company like cavalli do some marketing shit like that.

There's one thing i can't understand is that according to massdrop measurement, this amp has really low THD+N : only 0.0025% https://www.head-fi.org/threads/massdrop-x-alex-cavalli-tube-hybrid-amp-cth-dropping-monday.857673/. If it's a simple tube gain stage coupled to solid state buffer like the original CTH no way it could have such low THD. Even the schiit Vali2 with global feedback has higher distortion than the Massdrop CTH.

That is a tottally different design.

Yeah, i know it's liquid carbon, not liquid gold but as you stated that liquid carbon is mini liquid gold, i assume that the topology is the same, may be the liquid gold has better PS, transistor, ... etc. You seem to surf taobao a lot . I don't understand why you always want to reserve engineering cavalli product while you always call their product shitty? I'm also very curious about cavalli designs because i have heard the ehha, it sound very good and i really like reading detail his diy document. I guess the Liquid Crimson is like Schiit Jotunheim with input swap by tubes? I don't know other way then that you can make a balanced amp with only 2 tubes. Anyway, can't wait until you publish other cavalli design

So you said the LG is just a bigger LC, and now we can have a Massdrop LG for only 299$

I don't think the input jfet (2sk170bl) is fake as i buy it from a very high reputation local shop, the volume is 50k type, i will try it with 10k. Thanks for your suggestion.

Hi Kelvin! After some time, i have discovered that my amp have some serious problem: when i turn the volume up, after half volume the noise is increased to very audible level, so i measure the output with nothing connected, maximum volume and got this: Some serious 50hz harmonic at -55dbv lvl ! At min volume, it's fine: I thought it could be the power supply problem but i measure the PS and it's fine: So the problem must come from amp board, do you think what can cause this? Thanks!

Thanks you guys, actually that engraving and drill hole for audio jack (the volume pot hole come with the stock panel) cost me only 5$, incredible cheap!