[max232]

I just had a message here on Head-Fi, from a user who's modding his DSD, and the series resistors between the outputs of the OP275 op-amps and the 2.5mm TRRS jack, are 22Ω.
He said that there are also 22Ω resistors between the socketed op-amp and the 3.5mm TRS jack.

Humor me, why is that important? Does it imply that it won't drive high impedance phones?

 

[DBaldock9]

No, driving higher impedance phones usually works just fine - the issue is the potential for changing the sound when driving low impedance phones.
http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html

 

[max232]

No, driving higher impedance phones usually works just fine - the issue is the potential for changing the sound when driving low impedance phones.
http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html

Ok thanks. I'm trying to get on board with this stuff. That's a great article!

 

[shutterbox]

I just had a message here on Head-Fi, from a user who's modding his DSD, and the series resistors between the outputs of the OP275 op-amps and the 2.5mm TRRS jack, are 22Ω.
He said that there are also 22Ω resistors between the socketed op-amp and the 3.5mm TRS jack.

Does that mean these out the output impedances for balanced and SE output? If so, many earphones could be ruled out

I thought I remember seeing someone mentioned the SE output impedance is <1 but I could have misunderstood.
.

 

[Ivan TT]

the series resistors between the outputs of the OP275 op-amps and the 2.5mm TRRS jack, are 22Ω.

 

[max232]

That's the 4495 version? What does the fact that the resistors are 22ohm imply?

 

[DBaldock9]

That's the 4495 version? What does the fact that the resistors are 22ohm imply?

It's the AK4497EQ analog board.

 

[Ivan TT]

As above, AK4497 with decoupling caps removed.

Output resistors act as current limiters, short circuit protection and isolate capacitive loads (and cable is capacitive).

If used they determine output impedance, which is not a problem for high-impedance loads, but a bit of a lottery with BA's and hybrids.

I have IEMs that would not play nice with anything above 0 Z (Z for impedance) or close to it, have hybrids that sound good regardless.

Sonically these issues manifest as / curve to me, drop in LF, increase in HF.

I had a chance to audition FH5 on FA1 (22Ohm Z) they sounded yuk, on mojo (Z0) - not bad.

I plan (among others mods, I think I have about 5% of original parts still remaining on my DSD dac-amp board, everything else has been replaced) to use OPA1622 configured for unity gain as output buffers for both SE and differential outs and remove output resistors altogether, but it will take some time to get there, international deliveries could be so slooooooowwwwww....

 

[DBaldock9]

As above, AK4497 with decoupling caps removed.

Output resistors act as current limiters, short circuit protection and isolate capacitive loads (and cable is capacitive).

If used they determine output impedance, which is not a problem for high-impedance loads, but a bit of a lottery with BA's and hybrids.

I have IEMs that would not play nice with anything above 0 Z (Z for impedance) or close to it, have hybrids that sound good regardless.

Sonically these issues manifest as / curve to me, drop in LF, increase in HF.

I had a chance to audition FH5 on FA1 (22Ohm Z) they sounded yuk, on mojo (Z0) - not bad.

I plan (among others mods, I think I have about 5% of original parts still remaining on my DSD dac-amp board, everything else has been replaced) to use OPA1622 configured for unity gain as output buffers for both SE and differential outs and remove output resistors altogether, but it will take some time to get there, international deliveries could be so slooooooowwwwww....

Are you working with the OPA1622, installed on a DIP-8 header, or directly with the tiny VSON-10 surface mount package?

 

[Ivan TT]

Are you working with the OPA1622, installed on a DIP-8 header, or directly with the tiny VSON-10 surface mount package?

The former, but I would love to have skills to design a PCB for VSON-10!

I will have bypass caps soldered on DIP8 PCB and short wires to tap into power and I/O, there's just enough space on either side of DIP8 socket and above it to fit 3 in (having said that I had 2xLME49600 installed for a day or two and could still somehow slide the whole thing into the casing )

By the way, for those who are handy with hot air soldering replacing 5V and 3.3V LDOs for low-noise alternatives improves sound quality quite a bit, 3.3V replacement is LP5907, 5V - TPS73250, arrow.com has them in stock and the delivery is free (including international). I have 3.3V LDOs replaced across the digital board too.

 

[DBaldock9]

The former, but I would love to have skills to design a PCB for VSON-10!

I will have bypass caps soldered on DIP8 PCB and short wires to tap into power and I/O, there's just enough space on either side of DIP8 socket and above it to fit 3 in (having said that I had 2xLME49600 installed for a day or two and could still somehow slide the whole thing into the casing )

By the way, for those who are handy with hot air soldering replacing 5V and 3.3V LDOs for low-noise alternatives improves sound quality quite a bit, 3.3V replacement is LP5907, 5V - TPS73250, arrow.com has them in stock and the delivery is free (including international). I have 3.3V LDOs replaced across the digital board too.

There are a few small production run PCB shops in NZ, including - https://www.pcbzone.net/user/About.aspx

I've got one of these on order, to replace the soldering iron I've been using for the last 32 years (at least) - so that it's easier working on surface mount designs, like the various Zishan DAPs, and Walnut DAPs & Amps -
https://www.ebay.com/itm/Aoyue-968A...ron-Hot-Air-Station-Complete-Kit/110839316933
Also picked up one of these, for removing / replacing through-hole sockets -
https://smile.amazon.com/gp/product/B00B88FRME/

When installing the OPA1622 DIP-8 adapters in the DSD, are you removing the socket pins, so that they're lower profile?

 

[endia]

I plan (among others mods, I think I have about 5% of original parts still remaining on my DSD dac-amp board, everything else has been replaced) to use OPA1622 configured for unity gain as output buffers for both SE and differential outs and remove output resistors altogether, but it will take some time to get there, international deliveries could be so slooooooowwwwww....

i installed that opa1622 as lpf on my 4495 dsd, one of my favorite opamp among opa189 and opa2209..

By the way, for those who are handy with hot air soldering replacing 5V and 3.3V LDOs for low-noise alternatives improves sound quality quite a bit, 3.3V replacement is LP5907, 5V - TPS73250, arrow.com has them in stock and the delivery is free (including international). I have 3.3V LDOs replaced across the digital board too.

there are two TPS73250 there; DCQ (sot223) or BVT (sot23), which one is suitable?

When installing the OPA1622 DIP-8 adapters in the DSD, are you removing the socket pins, so that they're lower profile?

standart socket pins not suitable for zishan, max space you have is a standart dip8 opamp height..
i did a few custom adapters specially for it and had explained the process some time ago;
https://www.head-fi.org/threads/the-zishan-dsds-corner.826185/page-47#post-13615969

 

[DBaldock9]

i installed that opa1622 as lpf on my 4495 dsd, one of my favorite opamp among opa189 and opa2209..





there are two TPS73250 there; DCQ (sot223) or BVT (sot23), which one is suitable?



standart socket pins not suitable for zishan, max space you have is a standart dip8 opamp height..
i did a few custom adapters specially for it and had explained the process some time ago;
https://www.head-fi.org/threads/the-zishan-dsds-corner.826185/page-47#post-13615969

I've purchased some of the BrownDog 020302 Dual SOIC-8 to DIP-8 headers, with the custom installed short pins, without shoulders - for the SOIC parts.
The OPA1622 is a VSON-10 part, and @Ivan TT is installing those op-amps in his DSD, mounted on the DIP-8 adapter.
I was just asking if he was removing the pins on the DIP-8 adapter, to make the assembly thinner.

 

[endia]

I've purchased some of the BrownDog 020302 Dual SOIC-8 to DIP-8 headers, with the custom installed short pins, without shoulders - for the SOIC parts.
The OPA1622 is a VSON-10 part, and @Ivan TT is installing those op-amps in his DSD, mounted on the DIP-8 adapter.
I was just asking if he was removing the pins on the DIP-8 adapter, to make the assembly thinner.

ah! i should read with more care, sorry..

 

[max232]

There are a few small production run PCB shops in NZ, including - https://www.pcbzone.net/user/About.aspx

I've got one of these on order, to replace the soldering iron I've been using for the last 32 years (at least) - so that it's easier working on surface mount designs, like the various Zishan DAPs, and Walnut DAPs & Amps -
https://www.ebay.com/itm/Aoyue-968A...ron-Hot-Air-Station-Complete-Kit/110839316933
Also picked up one of these, for removing / replacing through-hole sockets -
https://smile.amazon.com/gp/product/B00B88FRME/

When installing the OPA1622 DIP-8 adapters in the DSD, are you removing the socket pins, so that they're lower profile?

That's a really nice soldering kit. I dabbled in surface mount soldering years ago modding video equipment. I wouldn't know where to start with audio. I've sold all of my tools over the years. A good fluoresent lighted magnifier is worth it's weight in gold I can tell you that. As well as a good solder sucker.