[HeyManslowdown97]

By newer I meant...newer, because OPA1612 is a newer design then let's say NE5532 or even LM4562. OPA1612 is one the most low-noise opamps ever built, so totally recommended for unity-gain stages (LPF or output stage of a DAC, but also I/V stage too).

You should be able to find single-to-dual DIP8 adapters for mounting 2xAD797 on a DIP8 socket.

In your experience with the Opa1612 how stable is it with high frequency application in a DAC that tends to run sharp in the tremble? I.e. DSD DAC

I also need to use Low impedence caps with high current ripple as what the DAC calls for. You have any recommendations in the 500mA range Low Impedance Cap to power the opa1612 at 3.6mA per channel (chip) and beyond?!

Will try to fit adapters if I can use the AD797 as well! thanks for rec’s!

It does sound like the Opa1612 is ideal for what I need it for! I can always add the AD797 in the output stage

 

[Rroff]

I've never had any problems with the OPA1612 and stability personally in a variety of uses the only exception to that I had a loose connection once in an amp from plugging in and out dozens of opamps for testing (not the last time it has happened either :| ) and had an OPA1612 get very very hot and start misbehaving - though it survived.

 

[HeyManslowdown97]

I've never had any problems with the OPA1612 and stability personally in a variety of uses the only exception to that I had a loose connection once in an amp from plugging in and out dozens of opamps for testing (not the last time it has happened either :| ) and had an OPA1612 get very very hot and start misbehaving - though it survived.

I have interested in low ESR Electrolytic Capacitors to power the Opa1612. My main attraction to them is a higher ripple current in the AC to “ power” the board onward as the opa1612 only requires low quiescent current of 3.6 mA but I know I’m in the Op amp thread so I don’t want to take the thread off topic. I just wanna know how much caps play a role on the op amp and what’s a recommendation for low impedance headphones combo with op amp and caps in a lpf in a DSD DAC. Or can someone guide to a head fi thread devoted to caps discussions if it exists to broaden my knowledge of them and how they used in applications!

My main objective is get more volume from the DAC not more gain since more gain creates more noise (if that makes sense).

Simply looking at the specs the opa1612 is pretty nice but I’ve yet to commit to a dedicated listening test.

 

[carlmart]

If you want to get more volume, but do no want to increase the gain, then you will to increase the power supply voltage. Or add another stage.

 

[raoultrifan]

https://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf worth a read. Usually, a fast multilayer 0.01-0.1uF + 1uF tantalum should do, but one 10...100nF in parallel with 10...100uF for each rail should do as well. This should ensure a good and oscillation-free operation for most opamps; of course, a crappy PSU and badly designed PCB will need additional care (I mean more caps across the rails, in between the opamp and the PSU itself).

Not sure how to achieve a higher volume to an amplifier without increasing the gain. Also, I'm not sure why do you refer to a DAC instead of an amplifier? For a DAC, just find one able to output 4V RMS (ES9018 and I guess ES9038 chips can be programmed this way); at leas Burson Play can output > 4V RMS single-ended directly from the ES9018K2M chip, so the amplifier's gain is a bit over 2X (it outputs 10V RMS in the end).

 

[HeyManslowdown97]

If you want to get more volume, but do no want to increase the gain, then you will to increase the power supply voltage. Or add another stage.

Thanks for the suggestion. How do you add another stage??! I am interested in knowing how! I am thinking of using a step up converter but am afraid of frying the line that goes to the semiconductor (Ak4497eq) that’s datasheet voltage is set at up to 3.6v and I want to go up to 5v. The step ups LDOs are only good at low leaps in power supply.

The signal relay is 3VDC which I changed from the stock for better quality (coil, construction, etc), I thought about going up to 5, 6 or 9VDC but I’m afraid of frying the board because I don’t know how to overhaul the entire DAC’s power supply. Haha

What is interesting is that the new Ak4499 chip runs on current rather than voltage so that’s where I got the idea of increasing the current ripple but that might create more noise??!

All this stuff is interesting but just when you think you have a “figured it all out” and aha moment when you do more research you realize everything you first thought was brilliant becomes a huge miscalculation!

@raoultrifan your post never disappoint! Will study your info, thanks!!! I just meant overall volume without distorting and it would be nice to “power” your music via the amps in terms of sound would be great so I get what you meant about amp not the DAC; I was just thinking holistically

Tantalum Polymer caps are interesting and it funny you mention them because I was reading up on them and was considering using them. They are really resistant to shock and vibration and a low ESR which sounds fascinating! I’m also considering Ceramic Caps for longer life expectancy and I’ve heard they are really great with noise reduction along the the op amp.

The trick I believe is allowing the Op Amp to do it’s thing without the DAC getting in it way. The Burson as you described it sounds pretty bada**!

 

[carlmart]

Any direct changes on the Topping, except if you really know what your are doing and have DIY experience with SMD parts, is not recommended.

The most you could or should do is soldering two three thin wires to L and R DAC output, and add another power supply and amplifier circuit OUTSIDE the Topping, on an external box.

As the DAC output is balanced, just twisting each wire group will preserve the signal from noise and RFI.

But a much simpler way would be to add an external headphone amp.

 

[HeyManslowdown97]

Any direct changes on the Topping, except if you really know what your are doing and have DIY experience with SMD parts, is not recommended.

The most you could or should do is soldering two three thin wires to L and R DAC output, and add another power supply and amplifier circuit OUTSIDE the Topping, on an external box.

As the DAC output is balanced, just twisting each wire group will preserve the signal from noise and RFI.

But a much simpler way would be to add an external headphone amp.

External headphone amp are really excellent choice provided that it’s a better sounding than you preamp and has a great battery life.

You solder three wire for per channel with a ground, positive and negative.

(I know any mod has high risk and high reward)

Was thinking of rocking one of this but don’t know to connect it to the DAC.

US $1.23 11％ Off | Dual OP Amp Board Preamp DC Amplification PCB DC Pre-Amp Amplifier Empty Board Module for NE5532 OPA2134 OPA2604 AD826
https://s.click.aliexpress.com/e/iuDJYIk

 

[carlmart]

Did I say battery powered headphone amp? I didn't, and certainly wouldn't recommend it.

A single DIP IC won't be able to provide high amplification for headphones.

You should look for designs where the chips can output high current or that use push pull output transistors, preferably mid power types.

And supply should be splitted and well regulated, more than +/-12v. Linear if possible.

 

[Rroff]

Not sure how to achieve a higher volume to an amplifier without increasing the gain. Also, I'm not sure why do you refer to a DAC instead of an amplifier? For a DAC, just find one able to output 4V RMS (ES9018 and I guess ES9038 chips can be programmed this way); at leas Burson Play can output > 4V RMS single-ended directly from the ES9018K2M chip, so the amplifier's gain is a bit over 2X (it outputs 10V RMS in the end).

Yeah as far as my knowledge goes if you want more volume minimising gain you HAVE to have higher output voltage from the source (DAC) but that does mean having higher voltage on the amp side so you can avoid clipping, etc. at a given gain.

+/-12V rails (and whatever VRMS that is) is where most headphones stop gaining from higher voltage really and in many cases anything from +/-9V upwards is fine potentially a lot of headphones can be damaged if you go much over around 7-8 VRMS anyhow (usually a power rating but it often works out around that).

As a general point as well while having low impedance is important - going all out for ultra low impedance can actually be detrimental - there is usually a window of impedance that will get the best performance and stability from an amplifier especially some regulators can be very sensitive to ESR - hence why many amps have a pair of 220uf reservoir caps that you can't just randomly increase the size of and necessarily get good results despite a popular thing being replacing them with ~680uf caps.

 

[HeyManslowdown97]

Yeah as far as my knowledge goes if you want more volume minimising gain you HAVE to have higher output voltage from the source (DAC) but that does mean having higher voltage on the amp side so you can avoid clipping, etc. at a given gain.

Yep, so many people don’t “hear” digital clipping. Voltage is the way to go 99% of the time! Although some DACs are now using replace higher voltages for higher current which is something that was considered taboo years ago but I think technology has gotten so good that you don’t even notice “drops” in AC.

AC also has major advantages mainly being safer in the board but I would imagine it being more sensitive.

The great boards have a balanced combo of both AC and DC especially in Op amps. (IMO).

As a general point as well while having low impedance is important - going all out for ultra low impedance can actually be detrimental - there is usually a window of impedance that will get the best performance and stability from an amplifier especially some regulators can be very sensitive to ESR - hence why many amps have a pair of 220uf reservoir caps that you can't just randomly increase the size of and necessarily get good results despite a popular thing being replacing them with ~680uf caps.

Yea, there’s no way to know unless you A/B test and experiment. But based on what you wrote I have read very similar stuff. So it’s a balance. I can speak for experience increasing the uf’s in the caps doesn’t make it sound better but when you start off it just seems “logical” to do. It’s “sounds” great in theory until you listen and realize how wrong you actually were!

 

[Spektykles]

After some hunting time I found a supplier still have some AD797 Mil'spec NOS, they still have about 200 units in stock. I already ordered 2 pair just for fun. If anyone is interested then PM me, i could arrange some for you.

 

[HeyManslowdown97]

After some hunting time I found a supplier still have some AD797 Mil'spec NOS, they still have about 200 units in stock. I already ordered 2 pair just for fun. If anyone is interested then PM me, i could arrange some for you.

There’s are actually quite a lot of resellers in the States that do this! Hong Kong is interesting since it’s only 30 minute boat ride to shenzhen yet it’s still unofficially run by the UK so they benefit from these ”specials”

Hong Kong is also home of the free internet to mainland china. It's how they allow protection for free speech.

AD797 spec ”bump” isn't that high for the military grade since the innovation is about 30 years old.

The AD797 was a response to the popular Opa627. So putting a military grade with slightly bump in specs at the time used for military purposes and now discontinued and decreases its supply while Increasing it’s demand value.

There’s is also Moore’s Law that makes Op amps transistor much better than they were 30 years ago.

Scarcity is used as commodity when demand is up and supply is down especially when parts of the world is closed to particular markets because of things like sanctions, etc*

All things equal you would still need a superior DAC with exact equilibrium to perhaps notice any audible difference from the prosumer grade made today. Then there’s the quality of the recording and also what type of genre of music that will emphasize certain features of the AD797 (military grade?!) that weren’t designed for music.

“Military grade” may be a detriment as an “Audio grade” as the application isn’t in lock-step with its functionality. Then there’s subjectivity in the form of the placebo effect of justifiability to one’s purchase.

There is more than just datasheet specs in the nuance of making and reproducing sound unless you talking about a specific usage in music reproduction such a well temper piano, etc with exact specifications in the form of tonality and pitch.

There’s just so many variables. It’s not about what is says in the requirement usages. Although such guidelines must be respected for they may cause damaged to any DAC or parts on the DAC.

But I am sure it’s worth a try for fun. Wouldn’t hurt to do so!

Spoiler

*“Scarcity

Spoiler

Principle. In economics, market equilibrium is achieved when supply equals demand. ... Disequilibrium also occurs when demand for a commodity is higher than the supply of that commodity, leading to scarcity and, thus, higher prices for that product.”[\Spoiler]

 

[Ivan TT]

Hi all!

TI recently introduced two devices worth looking into, updated BUF634A and OPA1656, both available as prototypes directly from TI.

New BUF634A has higher slew rate, wider BW and decreased quiescent current in wide-BW mode, and is cheaper than original 634

OPA1656 is positioned for audio applications: low noise and really good THD (-131dB) and high output current (100mA), but still needs a series resistor to drive capacitive loads unfortunately.

Together will make a really good composite amplifier, I will try this application at some stage.

 

[Themilkman46290]

Hi all!

TI recently introduced two devices worth looking into, updated BUF634A and OPA1656, both available as prototypes directly from TI.

New BUF634A has higher slew rate, wider BW and decreased quiescent current in wide-BW mode, and is cheaper than original 634

OPA1656 is positioned for audio applications: low noise and really good THD (-131dB) and high output current (100mA), but still needs a series resistor to drive capacitive loads unfortunately.

Together will make a really good composite amplifier, I will try this application at some stage.

So if my device had buf634 before, I could use these in its place?