xrk971 Pocket Class A Headamp GB

[xrk971]

The electrolytic caps on input should have +ve going to JFET and -ve going to input signal. Elna Silmic II 4.7uF are good choice for this.

 

[xrk971]

Hi all, I am new to DIYA and am very excited to begin building this uber pocket amp!

I only see the diagram of the top side of PCB, can someone point me to the SMT side of PCB so I know how to populate it correctly?

thanks!

Edit: ok i get it, if the part label is legible and not reversed then that is the part for that side...!!!

If you don't read through thread you will miss tips on improving Amp. Initial BOM has been upgraded so that 100uF oscon now replaced with 2200uF 16v Nichicon. Improves stereo crosstalk from -53dB to -73 dB. Eliminates turn off thump.

 

[babysupra]

The electrolytic caps on input should have +ve going to JFET and -ve going to input signal. Elna Silmic II 4.7uF are good choice for this.

Hi X, this is macky112 from head-fi =)

on your post 575 on this thread, I noticed you have both the film caps and electro caps at C1 and C2_2 locations:
1. how are the film cap and electro cap connected? are they in parallel?
2. are the film caps required at those locations, or can I just go with electro caps?

thanks!

 

[xrk971]

Hi X, this is macky112 from head-fi =)

on your post 575 on this thread, I noticed you have both the film caps and electro caps at C1 and C2_2 locations:
1. how are the film cap and electro cap connected? are they in parallel?
2. are the film caps required at those locations, or can I just go with electro caps?

thanks!

They are in parallel and it's all about what you like to do / "cap rolling".

On the inputs some people would be happy with just a 4.7uF Elna Silmic II. Stock config is 2.2uF film.

On outputs the stock config is 390uF electrolytic and 1uF film. Some people like just a single 100uF electrolytic here. I like 1000uF oscon plus 100uF Silmic plus 1uF film.

If you just had the 1000uF oscon no film - it would probably sound fine. These are very small nuances in the sound we are playing with.

There is a big 470uF Silmic that might be interestingg.

On inputs, electrolytics have +ve facing in towards the input transistors.

 

[babysupra]

They are in parallel and it's all about what you like to do / "cap rolling".

On the inputs some people would be happy with just a 4.7uF Elna Silmic II. Stock config is 2.2uF film.

I see! that means what you showed on post 575, the 3rd image, is actually total of 6.9uF at C1

On outputs the stock config is 390uF electrolytic and 1uF film. Some people like just a single 100uF electrolytic here. I like 1000uF oscon plus 100uF Silmic plus 1uF film.

If you just had the 1000uF oscon no film - it would probably sound fine. These are very small nuances in the sound we are playing with.

There is a big 470uF Silmic that might be interestingg.

On inputs, electrolytics have +ve facing in towards the input transistors.

it looks like C2_1 and C2_2 are in parallel right? could you explain what is the purpose of the C2_2 bypass cap? is it just a way to fine tune output capacitance? (I just read through both threads on head-fi, I will begin reading through this thread today, and I apologize if this question has been covered before in this thread!)

 

[xrk971]

It is a common belief that electrolytics have higher distortion at higher frequencies. By putting a bypass film cap that has low distortion and low ESR, treble performance is improved. Whether we can hear it is another matter. Funch says he can.

 

[babysupra]

Hey X, I have access to several 18v switching power supplies, and I was thinking using one during my building phase so I don't have to mess with alkaline 9v batteries

wondering about cap voltage rating, in the final BOM list, ost electro caps are rated 16v, if I just plug the 18v PS3 directly into this amp, uh, are the caps gonna explode on me? Is it necessary to go for 25v caps.

 

[babysupra]

I just looked over my mouser order confirmation and I made the mistake of ordering four 1uF Wima caps instead of two 1uf and two 2.2uf

Is it ok to just parallel an electrolytic cap to a 1uf Wima at input C1 to increase capacitance?

 

[xrk971]

You can use 1uF on inputs to start - add some 4.7uF Silmics later on the SMT side.

 

[xrk971]

Clear mint tin case, this one is actually an NHB for someone in Singapore.

 

[stellarelephant]

Sleek!

 

[stellarelephant]

I just looked over my mouser order confirmation and I made the mistake of ordering four 1uF Wima caps instead of two 1uf and two 2.2uf

Is it ok to just parallel an electrolytic cap to a 1uf Wima at input C1 to increase capacitance?

You can use 1uF on inputs to start - add some 4.7uF Silmics later on the SMT side.

Good news...
1uF may actually be plenty...with a stock 47K local feedback resistor (R2), anyway.

I've been having fun learning to make bode plots. If I'm doing it right, then either 1uF or 2.2uF will give full bass extension, since both set the corner frequencies close to the "textbook perfect" 2Hz. This results in no appreciable roll-off in the audible spectrum above 20Hz...well maybe like -0.1dB in the case of the smaller cap. I certainly don't think I'd be able to hear the difference...

 

[xrk971]

Anyone looking for a great sounding headphones on a budget should check these out. I just bought a pair to use for my low impedance phone tests. Status Audio model OB-1. Superb sound, very well made, super comfortable to wear circumaural. Open back design for nice sound stage. Nominal 55ohms but innerfidelity data shows closer to 70ohms - 96dB sensitive not an exaggeration. $79 on Amazon Prime free 1 day shipping. I have listened to them all night. I can highly recommend - sounds similar DT880 but probably more bass. Nice overall balance though.

The lower impedance load definitely works well with the new Hugh Dean desktop amp design (6w into 8ohms CFP with a CCS in SE Class A) amp that I am testing prototype now. Unbelievable bass dynamics.

 

[prasi]

Presenting the Silicon Harmony - a CFP SE Class A amp with CCS developed in conjunction with Aksa. Intial tests at 1.5amp bias and 34v linear supply is simply stunning. Immense power and dynamics on 55ohm Status OB-1's.

Nice and convenient PCB design.

You could try these for fastons http://www.mouser.in/Search/ProductDetail.aspx?R=1742188-1virtualkey57100000virtualkey571-1742188-1
and these for its insulated female part
http://www.mouser.in/ProductDetail/...GAEpiMZZMvz8LftK4jerjSynp%2bx3x0siOylZjvGK0Y=

 

[xrk971]

Presenting the Silicon Harmony - a CFP SE Class A amp with CCS developed in conjunction with Aksa. Intial tests at 1.5amp bias and 34v linear supply is simply stunning. Immense power and dynamics on 55ohm Status OB-1's.

 

[xrk971]

Nice and convenient PCB design.

Yes, the layout designer did a fantastic job! A true work of art

 

[pcgab]

Presenting the Silicon Harmony - a CFP SE Class A amp with CCS developed in conjunction with Aksa. Intial tests at 1.5amp bias and 34v linear supply is simply stunning. Immense power and dynamics on 55ohm Status OB-1's.

Nice! Are those boards available X?

 

[xrk971]

Sorry, these boards will only be part of finished special edition desktop amps - still under development so spec's are not firm yet. It will be a fairly substantial sized case and PSU given the heat output (circa 45w to 60w per channel).

 

[gwrskien]

No,no,no, that is a terrible idea.. we need more amps and boards...

 

[stellarelephant]

Wow, it certainly looks good. Love the new logo too!