[Algar]

I'll probably be getting this for a psu http://www.artesyn.com/media/pdfs/ssl20c.pdf

 

[FritzS]

Quote:

Originally Posted by PinkFloyd Mike.

Mike,
whats the value from the PHE466 - bypass of the output electrolytic cap?

What recommand you for bypassing a 1000 uF BG?

 

[PinkFloyd]

Quote:

Originally Posted by FritzS Mike, whats the value from the PHE466 - bypass of the output electrolytic cap?

I think it was something like 100nF (polypropylene) and also a 1uF polyester in parallel with the output cap if I can remember correctly.

Quote:

Originally Posted by FritzS What recommand you for bypassing a 1000 uF BG?

I really don't know Fritz, it's up to you, does it need "bypassing"? I don't use the blackgate caps as they're too big (physically) and way too pricey for what they are, you could try the 1UF / 100nF / 100pF combo made up of 1uF polyester, 100nF polyprop and 100pF silvered mica in parallel with it... your ears will know if it's right for you, just experiment until you hit that "sweet spot" In fact, why are you using output caps? Better if you fit a trimpot and lose those caps altogether. Of course you won't need them at all if you are using the AD8065 as the offset is minimal.

Mike.

 

[FritzS]

Quote:

Originally Posted by PinkFloyd I really don't know Fritz, it's up to you, does it need "bypassing"? I don't use the blackgate caps as they're too big (physically) and way too pricey for what they are, you could try the 1UF / 100nF / 100pF combo made up of 1uF polyester, 100nF polyprop and 100pF silvered mica in parallel with it... your ears will know if it's right for you, just experiment until you hit that "sweet spot" In fact, why are you using output caps?

1uF polyester ..... you are a polyester fan

I did not use input caps - so I use a output caps - it's only to protect my headphones from demand

Quote:

Originally Posted by PinkFloyd Better if you fit a trimpot and lose those caps altogether. Of course you won't need them at all if you are using the AD8065 as the offset is minimal.

I search for a small DC protection for the headphones - Davids kit is to big fore my case. If I have a DC protection I will cancle the output cap too

 

[PinkFloyd]

Wait a few days Fritz, there may be some news for you

 

[FritzS]

Hi,
are good too!? I will get samples .....

http://www.linear.com/
LT1363 - 70MHz, 1000V/µs Op Amp
* 70MHz Gain-Bandwidth
* 1000V/µs Slew Rate
* 7.5mA Maximum Supply Current
* 9nV/ rt Hz Input Noise Voltage
* Unity Gain Stable
* C-LoadTM Op Amp Drives All Capacitive Loads
* 1.5mV Maximum Input Offset Voltage
* 2µA Maximum Input Bias Current
* 350nA Maximum Input Offset Current
* 50mA Minimum Output Current
* ±7.5V Minimum Output Swing into 150 ohms
* 4.5V/mV Minimum DC Gain, RL=1k
* 50ns Settling Time to 0.1%, 10V Step
* 0.06% Differential Gain, AV=2, RL=150 ohms
* 0.04° Differential Phase, AV=2, RL=150 ohms
* Specified at ±2.5V, ±5V, and ±15V

 

[69CamaroSS396]

Forgive me if this has been answered previously, but I haven't yet read all 37 pages of this thread. I can't access the White Noise website, either directly or through a link. I get what seems to be the home page, but I can go no further. Anyone else experience the same trouble?

Thanks, Greg

 

[FritzS]

Quote:

Originally Posted by 69CamaroSS396 Forgive me if this has been answered previously, but I haven't yet read all 37 pages of this thread. I can't access the White Noise website, either directly or through a link. I get what seems to be the home page, but I can go no further. Anyone else experience the same trouble?

here it works http://www.wnaudio.com/

 

[PinkFloyd]

Have you see the latest thread Fritz??

 

[FritzS]

Quote:

Originally Posted by PinkFloyd Have you see the latest thread Fritz??

Yes I do

 

[69CamaroSS396]

Quote:

Originally Posted by FritzS here it works http://www.wnaudio.com/

Fritz, Thanks, but I have the same issue with that link. I see the page with the amps and the menu, and nothing happens beyond that. I've never had a problem like this.

Greg

 

[FritzS]

Hi,
The following modifications I will make ...... as seen on Walt Jung's Website ......
WTnT_Op_Amp_Audio_2 - Realizing High Performance: Buffers (Part II) http://waltjung.org/PDFs/WTnT_Op_Amp_Audio_2.pdf
Replace the two diodes with transistors - MPSA42 / MPSA92
connect the collectors with a pice of wire to +V or to -V (as shown in picture)
both resistors in path must be equal - 120 Ohm (Welwyn RC55C 0,25W 0,5%)
both current sources must be equal - 3.5 mA
ZOBEL network - 10 Ohm in series with a 100 nF cap (WIMA MKS4 0,1 uF 250VDC / Welwyn MFR4 0,25W 1%)
a 15 Ohm resisitor in series to the headphone
local and over all feedback resistors as described in some threads
solder a 3 A reverse diode parallel to the PSU input posts und the PCB - to protect the amp from erroneous reverse polarity
solder a Panasonic FC 2200uF 50V cap parallel to the PSU input jack

If I have this done I will publish some photos here

The last ideas please see here:
http://www.stockhammer.at/hifi/wna.php

PS: I see the PPA v2 with discrete buffers is similar to my suggestion (of WNA) but use more parts
http://elvencraft.com/ppav2/
http://laroccoaudio.net/discretebuffer.htm

 

[FritzS]

Dear All,
really I miss the WNA discussions here

I hope a follower comes back as "phoenix out of ash" - as "Phoenix-HA1"!

But no-one reply to my suggestion for modification.
I think with an J-FET input OP and small modifications it can comes back as a great headphone amp!
Another idea I have for the output DC protection - it's a symbiosis from some DIY projects. I will post this ASAP.

My experience is a J-FET input OP sounds better than a bipolar input OP - AnalogDevice OP's sounds better than BurrBrown - the AD OP275 sounds better than NE5532N or OPA2134

I hope for feedback

 

[nph134]

Sorry about that, the website had to be moved to a new server and there were some problems so for a few days only the homepage was there. The whole site is up now though.

As it says on the front the website will stay up and show info on the up and coming WNA book.


Quote:

Originally Posted by 69CamaroSS396 Fritz, Thanks, but I have the same issue with that link. I see the page with the amps and the menu, and nothing happens beyond that. I've never had a problem like this. Greg

 

[spendorspain]

Hi

Yesterday I've installed in my WNA MkII the modified AD744 op-amp, with the output stage bypassed (output taken from pin 5, not 6). The mod is very easy: solder in a 8-pin DIL socket a bridge between pins 5 and 6 and bend slightly the pin 6 of op-amp to avoid any contact with the socket (I've also isolated it with fine heatshrink). Thus, the output from op-amp pin 5 goes through the bridge to the socket pin 6, and the modified assembly can be used like any normal op-amp (see attached photos).

Now the AD744 is in "IC1" position instead of LM6171 and the sound is very good, even with the output caps needed with LM6171 in place and with only 24 hour burning-in time. There is clearly more detail to my ears (my musical tastes are mostly classical symphonic) and without doubt it will improve as AD744 doesn't need any input/output cap in signal path. There is more space or air between instruments, so it is easier to hear the different musical lines or when two instruments are doubling. With AD744 it is like you sit a little further back in the concert hall (a perspective which I prefer with headphones) and the bass is much more tuneful and detailed.

Using output caps, I've not yet measured the possible DC offset, but there is absolutely no thumps when powering on and off (with AD8065 there was a loud and frightening thump at turn-on and even more at turn-off).

As listening goes on, I´ll post more impressions, but it looks very promising.

Regards
Jose