Is the volume the real issue in a preamp/headphone amp ?

[gino1961]

Hi ! after reading in this wonderful site some lab reports aboout great and still cheap headphone amplifiers i have come to the conclusion that their possible Achille's heel could be the volume control
I often read about an imbalance between the channels, especially towards the beginning of the rotation.
I'm wondering if bypassing or completely removing the internal potentiometer and using an external stepped attenuator with quality resistors could result in a practically flawless device.
I believe the volume attenuator is a very important point in the chain.
Otherwise, I wouldn't understand why potentiometers like the Penny & Giles exist, which are as exceptional as expensive.
Once that problem is solved, a very decent amplification circuit seems easier to find.
Basically, it would be a matter of cannibalizing the circuits inside one of these headphone amplifiers.
I had thought about a kit... but this solution seems even simpler.
If everything works, then you can always put it in a larger case.
I think these little gems aren't considered because they're too small.
If they were placed in a large case, they could sound like some high-end monster...
Have a good day everyone.
gino

 

[Chrispy]

Depends what you want the gear for, or expect of it. Preamps are one thing, integrateds another (and mostly integrateds are a waste of time IMO unless you just need the one box with it's baked in feature set that meets your needs).

 

[gino1961]

Depends what you want the gear for, or expect of it. Preamps are one thing, integrateds another (and mostly integrateds are a waste of time IMO unless you just need the one box with it's baked in feature set that meets your needs).

Hi ! thank you very much for your kind and valuable reply I am changing the title to avoid any confusione
My recurrent issue is the line preamp ... for me it is the center of a system And i would like to get a definitive one Someday
I could go for the Topping pre90 and done with that I am thinking about it also because it provides both unbalanced and balanced ins and outs
But the idea of some diy with some parts already available is tempting as last try

Some headphone amps provide a selection of the gain that makes them also perfect as line stages even from the headphone out (one great case below)

 

[respice finem]

It seems to be a solved problem.

Some analog preamps/HPA have stepped volume control based on a "resistor ladder"

'Topping L70 Headphone Amp Review'

Dec 5, 2022

This is a review and detailed measurements of Topping L70 balanced headphone amplifier. It was sent to me by the company and costs US $349.

The L70 has the beautiful white segmented display. It is the most visible/high contrast display I have seen on an audio product. Volume control is very responsive and is relay based to provide perfect channel matching. You get both unbalanced and balanced output with the latter providing substantially more power. A remote control is provided. Back panel shows some nice extra features:

You have 12 volt trigger to power it on...

• amirm
• Replies: 591
• Forum: Headphone Amplifier Reviews & Discussion

• 

I'm using only digital volume control since years (integrated DAC/preamp/HPA). The RME has automatic gain switching as a "bonus".
No problems driving any HP I came across.

 

[gino1961]

It seems to be a solved problem.
Some analog preamps/HPA have stepped volume control based on a "resistor ladder"

'Topping L70 Headphone Amp Review'

Dec 5, 2022

This is a review and detailed measurements of Topping L70 balanced headphone amplifier. It was sent to me by the company and costs US $349.

The L70 has the beautiful white segmented display. It is the most visible/high contrast display I have seen on an audio product. Volume control is very responsive and is relay based to provide perfect channel matching. You get both unbalanced and balanced output with the latter providing substantially more power. A remote control is provided. Back panel shows some nice extra features:

You have 12 volt trigger to power it on...

• amirm
• Replies: 591
• Forum: Headphone Amplifier Reviews & Discussion

• 

Hi ! thank you very much for your very helpful advice I have the feeling that this wonderful unit will solve any issue
But i am retired If i buy something definitive then i have only to listen to music
To be more specific i would like to start doing some DIY things I have a lot of free time and in the next future i would like to set up a small lab/workshop for fun
As i said above with the recent prices starting from a kit or even from scratch is a little unreasonable
The cheap units are built at a price point Savings are mandatory And my feeling is that most of the savings are located in the volume pot that is also a very important part
I like things like this

1pcs 23-Step 10KAX2 DALE Attenuator Dual-10K Stereo HiFi Volume Potentiometer | eBay

Le migliori offerte per 1pcs 23-Step 10KAX2 DALE Attenuator Dual-10K Stereo HiFi Volume Potentiometer sono su eBay ✓ Confronta prezzi e caratteristiche di prodotti nuovi e usati ✓ Molti articoli con consegna gratis!

www.ebay.it

after this a gain block cannibalized from some headphone amp and its done
I can reduce the overall gain placing a resistor at the input like i have done in the past A 10k resistor before a 10K pot halves the gain
usually power amps do not need much voltage for max power
And unbalanced can be just fine ...

I'm using only digital volume control since years (integrated DAC/preamp/HPA). The RME has automatic gain switching as a "bonus". No problems driving any HP I came across.

Very interesting You mean the RME sound card ?
there are also other option like the PGA 2310 that i am looking at actually with great interest
But i saw this lab report and i was shocked by the results

'Review and Measurements of Weiliang Volume Control'

Aug 11, 2019

This is a brief review and measurements of the Weilang Volume Control and remote control input switcher. It also has a Bluetooth interface built-in. It is available on Aliexpress for under US $40. A member of our local audiophile society brought it to our meeting today for testing.

The case is budget category but still metal with built-in mains power supply:

Seems like a lot of companies brand this product. Here is a picture of its guts from the Aliexpress seller:

It is impossible to fathom how...

• amirm
• Replies: 21
• Forum: Amplifiers, Phono preamp, and Analog Audio Review

• 

again the approach is to try to mate a very good level control with a decent gain stage
The remote control could make things more complicated

P.S. i have one Weiliang unit already If it were only for the low Hz peaks maybe it could be a power supply issue But the distortion ...
Unfortunately i have also lost the remote ... i will take it to the bench
I do not like much the unit with the mains transformer inside the case Much better to have an external high quality power supply and leave inside only the regulators
I did it already for an old dac and liked the final sound better Nothing fancy ... just a Lenovo 20VDC switcher feeding the internal regulator stage
they also sell similar mods

Pardon Our Interruption...

 

[respice finem]

I am no DIYer, really, the last thing I built myself (including etching the PCB) was a DBX compander for my reel-to-reel (in the 80s).
So, I would be probably doing more wrong than right without learning much from scratch, and I would have to buy tools etc. Too lazy

If you are looking for an analog unit, the above linked is OK IMHO and not even expensive.
There are also preamps with such volume control IIRC.

RME = i mean the two in my sig (ADI2-DAC), but IIRC the whole ADI series has roughly the same (digital) volume control.

 

[gino1961]

I am no DIYer, really, the last thing I built myself (including etching the PCB) was a DBX compander for my reel-to-reel (in the 80s).

was it not fun ? actually my dream would be to be able to design a pcb starting from a simple schematic
i have opened some days ago a british amp ... the pcb looks weird (even if the sound is very decent)
everyone is telling me how the lay-out is important But these guys should have been quite naive Some kits have much better designed pcbs

So, I would be probably doing more wrong than right without learning much from scratch, and I would have to buy tools etc. Too lazy

I see Imho instruments are more important than tools For instance a spectrum analyzer is very needed I am playing with some +5VDC power supplies
to do something serious i should be able to check the noise ... for now i listen through the speakers not very scientific for sure
I have 3 devices that needs 5VDC i.e. Chromecast Ultra + hdmi audio extractor+ usb dac
I just ordered some usb cables and i will connect them together to use just one low noise power supply for all units

If you are looking for an analog unit, the above linked is OK IMHO and not even expensive.
There are also preamps with such volume control IIRC.
RME = i mean the two in my sig (ADI2-DAC), but IIRC the whole ADI series has roughly the same (digital) volume control.

Thank you very much again I checked and these are high end pro units My playback system is not resolving enough
And i have to waste time ... sometimes the journey is more fun than the stay at the destination

 

[Sokel]

Regarding pots, you can get a blanc one like that and nice, precision, low ppm resistors to built your own if you like to spend time:

DIY Potentiometer switched 23 positions 4 poles Ø6mm - Audiophonics

rotary potentiometer 24 positions 4 poles Ø6mm

www.audiophonics.fr

You will have to get a precise LRC meter to check it though, as is your plan for your lab.
At the same site you can find kits to mess around as well.

 

[gino1961]

Regarding pots, you can get a blanc one like that and nice, precision, low ppm resistors to built your own if you like to spend time:

DIY Potentiometer switched 23 positions 4 poles Ø6mm - Audiophonics

rotary potentiometer 24 positions 4 poles Ø6mm

www.audiophonics.fr

hi and thanks a lot for the kind and very helpful advice The unit is very nice indeed with contacts sealed I have seen something similar on a very high end Convergent Audio Technology preamp ... it must be a really good solution

i had some experience with a stepped series attenuator 20Klog i bought many years ago After trying it i wonder why stepped attenuators are not more popular
And it was of the series type with the signal passing to all resistors ... increasing the volume the resistors are less of course The resistors were from Holco a very good brand

You will have to get a precise LRC meter to check it though, as is your plan for your lab.

Yes ! but i am still looking for a suitable place Then i could invest more Problem is that i have seen
I've visited several artisan workshops, but the owners prefer to rent at a high price.
The purchase costs per square meter the same as a house. At that point, a small house in the countryside is better. I live in the city and I'm fed up.

At the same site you can find kits to mess around as well.

for sure ready to use pcbs would help a lot For instance i see many boards for opamps I could use them to try some better opamp
I have some pair of interesting opamps like ad797 and ad811 (used by Jeff Rowland in his beautiful Synergy preamp)
a nice thing with opamps is that they draw usually very little current and 2 12V batteries can be used as a basic power supply
Some dc offset will not be a problem with coupling caps

 

[DVDdoug]

There are digital pots and digital volume control chips, and amplifier chips with digital volume control, or if you have digital audio it's easy in the digital domain.
Here is what a quick search of the TI website turned-up.

It seems like analog pots are getting rare. Especially since almost everything now has a remote control. My cars & AVR have rotary encoders. Of course my phone doesn't have a pot. My computer speakers have a pot and I've got a little amplifier in my bedroom for TV sound with a pot.

i see many boards for opamps I could use them to try some better opamp
I have some pair of interesting opamps like ad797 and ad811 (used by Jeff Rowland in his beautiful Synergy preamp)

Op-amps in line-level circuits aren't too critical. You can get better measured performance but it's not hard to get performance better than human hearing. If you have an actual preamp (phono preamp or mic preamp with high gain) noise is a consideration.

Amir has a couple of videos on op-amp "rolling": Does op-amp rolling make amps sound better? Does op-amp rolling swapping work? Part 2

If you're talking about headphone amps, standard op-amps aren't designed to drive the low impedance load. But there are lots of low-power "speaker amplifier" chips that can be used.

 

[gino1961]

There are digital pots and digital volume control chips, and amplifier chips with digital volume control, or if you have digital audio it's easy in the digital domain.
Here is what a quick search of the TI website turned-up.

Hi thank you for the very kind and precious advice
But i am afraid that designing something of the kind is really beyond my ability
I have only done kits in the past and some parts replacement
I can solder a pot but a digital volume control is impossible for me

It seems like analog pots are getting rare. Especially since almost everything now has a remote control. My cars & AVR have rotary encoders. Of course my phone doesn't have a pot. My computer speakers have a pot and I've got a little amplifier in my bedroom for TV sound with a pot.

I see but what about the sound quality?
I still see analog pots in high end equipment
My main interest is in preamps and headphones amps with low gain

Op-amps in line-level circuits aren't too critical. You can get better measured performance but it's not hard to get performance better than human hearing. If you have an actual preamp (phono preamp or mic preamp with high gain) noise is a consideration.

Thanks a lot My present source is a Chromecast followed by an audio extractor and a dac
I have also a cheap audio streamer from SMSL the dp3 but I prefer a video and audio streamer

Amir has a couple of videos on op-amp "rolling": Does op-amp rolling make amps sound better? Does op-amp rolling swapping work? Part 2

I have seen one comparison between two opamps
One discrete and the other monolithic
The difference in price looked higher than the one in measurable performance

If you're talking about headphone amps, standard op-amps aren't designed to drive the low impedance load. But there are lots of low-power "speaker amplifier" chips that can be used.

I understand What about using a low gain headphone amp as line stage?
Usually the main problem i have is too much gain
Some power amps deliver the max power even with less than 1 volt
Maybe an attenuator followed by a buffer could be a saner option?

 

[Joe Smith]

Hi thank you for the very kind and precious advice
But i am afraid that designing something of the kind is really beyond my ability
I have only done kits in the past and some parts replacement
I can solder a pot but a digital volume control is impossible for me

I see but what about the sound quality?
I still see analog pots in high end equipment
My main interest is in preamps and headphones amps with low gain

Thanks a lot My present source is a Chromecast followed by an audio extractor and a dac
I have also a cheap audio streamer from SMSL the dp3 but I prefer a video and audio streamer

I have seen one comparison between two opamps
One discrete and the other monolithic
The difference in price looked higher than the one in measurable performance

I understand What about using a low gain headphone amp as line stage?
Usually the main problem i have is too much gain
Some power amps deliver the max power even with less than 1 volt
Maybe an attenuator followed by a buffer could be a saner option?

You might check out the Schiit Saga 2 preamp. Headphone jack, stepped relay attenuator, remote control, and a full-fledged preamp to use with amp/speakers.

If you are particularly concerned about the channel balance at low levels, it's a nice and fairly cheap solution.

 

[gino1961]

You might check out the Schiit Saga 2 preamp. Headphone jack, stepped relay attenuator, remote control, and a full-fledged preamp to use with amp/speakers.

Good morning and thank you for your kind and valuable advice.
I should have prefaced this by saying: My main goal is to find a way to pass the time I have left between now and my death.
That's why I thought about a hobby.
In particular, audio, which has fascinated me for about 50 years.
I'm sure there are hundreds of commercial products that would immediately solve my problem.
But then what do I do?
So I thought, like many people do, about kits.
But then, looking at what the market offers in budget products, not trying to use one is crazy.
$100 now buys an absolutely excellent preamp.
Let's take the Topping L30. Many high-end preamps can only dream of its instrumental performance.
Since it's a budget product, they must have cut corners.
And then I don't like the low input impedance.
I don't understand why they chose 2.5kW instead of the standard 10K or at least 5KW.
And in fact, one idea is to unsolder the pot and replace it with a 10KΩ stepped attenuator.
I looked at the pot and it confused me. Does it look like it has 4 sections?
I think I'll eventually drop the remote control idea.
When you go to a concert, you don't adjust the orchestra volume, do you?
I think if someone feels the need to adjust the level, there must be a problem with the listening system.
I need to understand the Topping L30's potentiometer better.

If you are particularly concerned about the channel balance at low levels, it's a nice and fairly cheap solution.

not only the channel balance but also the overall quality Stepped attenuators are usually quite better
For sure i would love to get a Penny & Giles ... to use inside a case is a waste It is a piece of jewelry And the price goes along with that

 

[Francis Vaughan]

Chiming to say that audio electronics is likely a great hobby. Retirement can bring arbitrarily amounts of time get into the science deeply. I’m not far from retirement and already planning stuff.
Purchasing a few of the well know texts is a good start. Horowitz and Hill is still probably the go to. Douglas Self’s various books on audio design are authoritative and highly readable. The various on-line forums are generally good, but there is a tendency for many participants to just want the latest perfect answer, which can be frustrating. Especially when discussions lead into snake oil. Which DIY audio is not immune from.

On the subject of the Penny and Giles potentiometer. Remember this is intended for use in analog professional mixing desks. These potentiometers would see hundreds or thousands of movements per day. A big desk with automation would be used to replay a mix, from the original tracks, varying the pot positions in real time. A potentiometer rated for say 100,000 cycles could be expected to fail in months. A million cycles would still be borderline acceptable. A multi hundred thousand dollar mixing desk cannot fail like this. Compared to the cost of the rest of the desk, such components are quite justified. What they almost certainly did not add is some magic to the sound.

 

[gino1961]

Chiming to say that audio electronics is likely a great hobby. Retirement can bring arbitrarily amounts of time get into the science deeply. I’m not far from retirement and already planning stuff.
Purchasing a few of the well know texts is a good start. Horowitz and Hill is still probably the go to. Douglas Self’s various books on audio design are authoritative and highly readable. The various on-line forums are generally good, but there is a tendency for many participants to just want the latest perfect answer, which can be frustrating. Especially when discussions lead into snake oil. Which DIY audio is not immune from.

Hi and thank you very much for your very kind and valuable reply
Obviously, I have great admiration for the most famous audio designers and often read their interviews.
For example, if I read correctly, Nelson Pass, as a young man, worked in repairs and modifications to equipment.
This is sort of my goal: finding broken devices with potential, like a really nice working transformer in particular, and trying to get them working again, perhaps improving some parts.
The measurement issue remains. I believe a spectrum analyzer is a necessary tool.
The QA403, for example, costs around 800 euros in Europe... I understand it's a niche product, but I'm waiting for something less precise but more affordable.
Designing from the ground up is for truly competent people.
Better to start with something less challenging.

On the subject of the Penny and Giles potentiometer. Remember this is intended for use in analog professional mixing desks. These potentiometers would see hundreds or thousands of movements per day. A big desk with automation would be used to reply a mix varying the pot positions in real time. A potentiometer rated for say 100,000 cycles could be expected to fail in months. A million cycles would still be borderline acceptable. A multi hundred thousand dollar mixing desk cannot fail like this. Compared to the cost of the rest of the desk, such components are quite justified. What they almost certainly did not add is some magic to the sound.

Thanks and i see the point very clearly I am leaning towards 10Klog stepped attenuators
Another idea would be a cermet linear pot per channel with modified attenuation curve ... but i cannot even calculate the curve
I am very bad at math I will buy one cheap and make some measurements of the parallel pot and resistor
I read a recommendation to use a resistor 1/10 of the pot or something like that
The cermet pot have a much better contact between the wiper and the resistive layer I do not like plastic pots