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Posted
1 minute ago, Tasebass said:

Got send a link to the above video …

Sorry to say all this does is feed well fuelled fire to the hypocrisy “ High End” Audio producers have become…

 

love this hobby but seeing this makes me cringe 

 

Tase.

It’s very sad. When you consider that this is a $50k phono I would have thought the business owner would fix it for free. That would generate some serious goodwill. 

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Posted
1 minute ago, PKay said:

It’s very sad. When you consider that this is a $50k phono I would have thought the business owner would fix it for free. That would generate some serious goodwill. 

The Manufacturer sent it to Mark for repair..

Which He did…

Which by the look of it all send Tom into a spin..

huh!!🤔😳

Posted (edited)
8 minutes ago, Tasebass said:

Which by the look of it all send Tom into a spin..

huh!!🤔😳

 

Why the surprise? It must have been severely embarrassing to have his "secrets" revealed. 🙂  He must expect sales to tank after this.

 

 

Edited by aussievintage
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Posted
19 minutes ago, Tasebass said:

The Manufacturer sent it to Mark for repair..

Which He did…

Which by the look of it all send Tom into a spin..

huh!!🤔😳

I missed that bit. That will be the end of manufacturers sending Mark their gear.  You certainly wouldn’t expect that from a business relationship. 

Posted
56 minutes ago, PKay said:

I missed that bit. That will be the end of manufacturers sending Mark their gear.  You certainly wouldn’t expect that from a business relationship. 

Watch the start of the video again!!

Cracks me when Mark uses odds and Sods to mimic the product construction..

Posted (edited)

Alas, the dangers of posting on YouTube, Mend it Mark is one of many that has attracted the ire of an audio manufacturer for a video they deem unpalatable. I suspect Mark has not heard the last of Tom Evans Audio.

It's also risky being a technician posting on an audio forum but here goes. I am eating popcorn as I write.

As a technician I love to work on some of this small scale hi end gear and on many occasions cannot see the value of it.

At least the  Evans phono preamp was through hole components and basic opamps making it  repairable. The fact that the circuit was basically lifted from an opamp data sheet was amusing. Oh, and I also heard that in the world of some audiophiles that "opamps sound bad", hence the market for discreet opamps....how can this be with this 50k phono preamp being full of opamps.....sacrilege. Maybe a 2k directional power cable will improve the sound. Enough of my sarcasm but this is one of the beliefs in common circulation.

Much of the new small scale manufacturer gear is surface mount components and some featuring custom programmed FGPA chips with the part numbers filed off for example. The danger being that if the manufacturer disappears so does any hope of repairing the item.

So what lessons can be learned here. The power of research, choice and common sense.

In the case of the Tom Evans unit we have a small manufacturer and $50k for a phono preamp. I would definately want to pull the lid off and see where my money is going preferably in the presence of a knowledgeable audio technician. 

Sticking to larger reputable manufacturers is a good idea imo. Remember mass production brings down costs and they invest in the manufacturing and test equipment to produce a consistent quality product. 

There is too much snake oil in the world of audio, catering to many with deep pockets. The fact some companies exist means that they have a market to produce some of this stuff. 

I say good on them for tapping into this market and if you are silly enough to purchase some of it......good luck.

I love fixing audio  where I can but find that some of this new high end gear is increasingly harder to fix due to its complexity, lack of circuit information and the bad practice of some small manufacturers to file the part numbers off the components as mentioned previously. I can understand the reasons, Patents are super expensive and the China copy machine will rip off the design and clone it anyway. 

I too am enjoying the renewed interest in quality vintage audio equipment. A simpler time where things were built to last with quality components and service manuals to repair the device.

All I can say is good luck, do your research and purchase wisely. The world of hifi is indeed a minefield. 

Edited by Anodecap
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Posted
9 hours ago, Anodecap said:

discreet opamps

 

An amusing term.  An opamp is an opamp unless it's an audiophile opamp, where it's specifications may be somewhat less than an opamp. 🙂  An opamp can be made from anything, even valves.    Integrated circuit opamps are made from "discrete" transistor elements constructed on the chip.  You've seen the diagrams they publish.

image.png.fae29916335a27de2551b2b189122c6c.png

 

My main problem with using an opamp where a few transistors would do, is that it is overcomplicating things.   Simple single ended class A amplifying stages will do the same job and sound just as good, or probably better.

Posted
3 minutes ago, aussievintage said:

 

An amusing term.  An opamp is an opamp unless it's an audiophile opamp, where it's specifications may be somewhat less than an opamp. 🙂  An opamp can be made from anything, even valves.    Integrated circuit opamps are made from "discrete" transistor elements constructed on the chip.  You've seen the diagrams they publish.

image.png.fae29916335a27de2551b2b189122c6c.png

 

My main problem with using an opamp where a few transistors would do, is that it is overcomplicating things.   Simple single ended class A amplifying stages will do the same job and sound just as good, or probably better.

Yes opamps are a massive interesting subject that would make for an interesting thread. Discrete opamps require careful matching of transistors and have poor temperature compensation when compared to a simple Ic type such as the NE5532. They also take up a lot of room and are power hungry. I recently repaired an Eastern Electric DAC where the opamps had been replaced with discrete types that cooked the power regulators due to excessive current draw. I have rebuilt many analogue studio mixers in my time which are full of  simple ic opamps, NE5532/ 5534 being the most common. . 

Nothing wrong with the Tom Evans  design philosophy using opamps, the build implementation looked like a prototype especially for $50k. Maybe the poor publicity received will bring about a redesign. 

Opamp rolling is also an interesting audiophile subject potentially fraught with problems such as parasitic oscillation, distortion and excessive current draw if one deviates from the manufacturers design. Yet some manufacturers of DACs in particular provide sockets for opamp rolling in their products. 

Posted

I've read on other forums that OPAMP amplifier designs generally outperform their ALL DISCREET counterparts, due to the higher levels of consistency and quality control. 

This was news to me - but kinda makes sense, in light of this thread and the issues encountered with this phono stage.

I don't pretend to know the truth of it. 🤔

What do others think?  🧐

Posted
2 minutes ago, SONDEKNZ said:

I've read on other forums that OPAMP amplifier designs generally outperform their ALL DISCREET counterparts, due to the higher levels of consistency and quality control. 

What do others think?  🧐

 

I tend (for perhaps the very first time!  :shocked: ) to agree with av:

 

3 hours ago, aussievintage said:

Simple single ended class A amplifying stages will do the same job and sound just as good, or probably better.

 

 

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Posted
5 minutes ago, SONDEKNZ said:

I've read on other forums that OPAMP amplifier designs generally outperform their ALL DISCREET counterparts, due to the higher levels of consistency and quality control. 

 

It's more than that.  It is due to better designs that have been fine-tuned over the years, and the ability to implement more complicated designs - which a discrete design just cannot do, due to severe space limitations.  They (discrete opamps) are already too big to fit in many pieces of equipment.

 

That is not to say a completely different design for the equipment in question, maybe one NOT using opamps, might not be best of all.   

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Posted

It depends what you are trying to achieve, but as a general rule opamps from reputable manufacturers that apply strict tolerance and quality control to their manufacturing and factory acceptance testing perform superbly well and are incredibly reliable.

 

But in reality,  so much audiophile market demand is created by those that just believe things, and the underlying audiophile logic that goes along with that.  To someone that doesn’t know any better, it may make sense that a stack of discrete components will ‘sound better’ than an integrated chip.

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Posted (edited)
16 minutes ago, Anodecap said:

Vintage eq curves and wondering if it has IEC and NAB eq.

 

Not according to the manual.  This is why I have my own computer setups for playing those odd old records that very few manufacturers support these days.  I also built a small (opamp based 🙂 ) mono phono preamp with RIAA DIN DECCA78 AES NAB curves and more (can add more if ever needed)

Edited by aussievintage

Posted (edited)

I am interested in the Tom Evans phono design but now the video has been pulled am wondering if it is a negative feedback design or not. Was it MM and MC? and I would also expect adjustable loading for $50k. 

Looking at the number of opamps it's definately a cascaded opamp design. Here is a summary of the principle. ln a cascaded system, each op-amp is referred to as a stage. The output of one stage drives the input of the subsequent stage. As the input signal passes through each stage, it is amplified by the gain of that stage. The resulting overall gain of the cascaded system is equal to the product of the gains of each stage. For the price I would expect independent power supply rails for each stage. 

Tom states the following on his website which is a very bold statement and I remember seeing nothing remarkable when Mark traced the circuit. 

All audio amplifiers be they IC or discrete circuits have inherent flaws that the ear / brain is very sensitive to. I have developed unique circuitry and techniques to avoid the common pitfalls of amplifier design others fall into. 
Since then there have been a multitude of 'pretender' phono amp products produced by everyone that can hold a soldering iron, but none use or know anything about the highly advanced circuitry design I developed and use in my product range.  

Sounds like snake oil to me, but I am happy to be proven wrong. Is this amazing  revelation and circuit design worth $50k? 

Interested in comments.

 

 

Edited by Anodecap
Posted
33 minutes ago, Anodecap said:

ln a cascaded system, each op-amp is referred to as a stage. The output of one stage drives the input of the subsequent stage. As the input signal passes through each stage, it is amplified by the gain of that stage. The resulting overall gain of the cascaded system is equal to the product of the gains of each stage.

 

And hopefully, it has an even no. of gain stages, so that absolute polarity is maintained.

 

33 minutes ago, Anodecap said:

For the price I would expect independent power supply rails for each stage. 

 

Absolutely!  :shocked:

 

Posted

I cannot believe that anyone would even consider this unit after seeing the amatuerish design, poor manufacturing quality, and the utterly ludicrous scenario of the manufacturer not being able to repair it themselves.  😵‍💫

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Posted
23 minutes ago, POV said:

I cannot believe that anyone would even consider this unit after seeing the amatuerish design, poor manufacturing quality, and the utterly ludicrous scenario of the manufacturer not being able to repair it themselves.  😵‍💫

It's an interesting discussion and analysis given a decent opamp costs around $7 and there are only so many different opamp circuit configurations.....electronic components are cheap.  Hoping those that understand more about phono preamps than me join the discussion.  Big dollars are spent in the pursuit of vinyl perfection by many, wondering what justifies the $50k price tag.

I have lots of popcorn and am enjoying this topic. I seek enlightenment into the world of Audiophilia.

Posted
10 minutes ago, Anodecap said:

I seek enlightenment into the world of Audiophilia.

 

Well here's a red hot tip.  If a manufacturer of an electronic component cannot work out how to repair their own equipment, and need to send it to someone else to work out how to repair it....that is the biggest red flag of all the red flags.  It's a laughable scenario, and I'm not surprised they have had the video taken down.  Well may they be embarassed...the state of that component, and their inability to repair it themselves is inexcusable in my view.  

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Posted
18 minutes ago, Anodecap said:

Hoping those that understand more about phono preamps than me join the discussion.  Big dollars are spent in the pursuit of vinyl perfection by many, wondering what justifies the $50k price tag.

 

There is no mystery.  That price tag just represents how the gullible buy into the spin of audiophoolery.  

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Posted (edited)
31 minutes ago, aussievintage said:

 

Actually a bunch of them are being used in parallel.

Ahh yes I remember Mark mentioning this in the video. Maybe this is the "secret" technique justifying the $50k price tag.

Here is an excerpt regarding parallel opamps.

There are several advantages to paralleling operational amplifiers (op amps), including Increased output drive: The output drive capability increases by the number of amplifiers in parallel. 

-Reduced voltage noise: The amplifier noise power is reduced by the number of amplifiers in parallel. 

-Reduced output offset error: The distribution of offset errors moves toward a center value as more amplifiers are added. 

-Reduced power dissipation, Sharing the load with multiple amplifiers reduces the power dissipation of a single amplifier. 

-Increased current, Power op amps can be paralleled to increase current. 

-Improved SOA (Safe-Operating-Area): Power op amps can be paralleled to improve SOA. 

-Doubled thermal capability, Power op amps can be paralleled to double thermal capability. 

 

However, there are design details that require careful attention when paralleling op amps, such as common-mode range considerations, stability, slew rate, and losses. 

Justify the $50k price tag?

Think I will keep listening to my " Pretender" phono preamp.

Edited by Anodecap
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Posted (edited)

So out of interest I asked ChatGPT to design me a phono preamp using parallel opamps as an exercise into the use of Ai. In 5 minutes I had a full set of specs, a pcb design, parts list and LT Spice model. Here is part of what Chat GPT gave me. The Lt Spice model works flawlessly. 

See below.....

Designing a phono preamp with parallel op-amps involves combining the outputs of multiple operational amplifiers to achieve improved noise performance and higher current-driving capability. Below is a conceptual design outline:


---

Phono Preamp Design with Parallel Op-Amps

1. Input Stage

Cartridge Type: Identify the type of cartridge (MM or MC).

Moving Magnet (MM): Requires an input impedance of 47kΩ.

Moving Coil (MC): Typically lower impedance (10Ω–100Ω), often requires a step-up transformer or a high-gain input stage.

2. RIAA Equalization

Use active or passive RIAA equalization. For simplicity and accuracy, go for active equalization using the feedback loop of the op-amp(s).


3. Parallel Op-Amps Concept

Purpose: Using parallel op-amps can reduce noise and improve dynamic range, which is critical for phono preamps.

Configuration:

Connect the inputs of multiple op-amps in parallel (with input resistors for current sharing).

Combine their outputs through small resistors (for balancing) or directly if matched well.

Use op-amps with low noise and high linearity (e.g., OPA2134, LM4562, or NE5532).

4. Design Example

Schematic Overview

1. Input Stage:

Use an initial gain stage with 2-3 low-noise op-amps (e.g., NE5532) in parallel for each channel.

Input impedance: 47kΩ for MM cartridges.

2. RIAA Equalization:

Implement the RIAA curve in the feedback loop of the op-amp configuration.

Precision capacitors (e.g., polypropylene) and resistors ensure accuracy.

3. Output Stage:

Use another set of parallel op-amps to buffer the signal.

Combine outputs using 10Ω resistors for balancing.


Example Circuit Values:

Input gain: ~40 dB for MM, adjustable for MC.

RIAA values:

75µs: 2122 Hz (high frequencies).

318µs: 500 Hz (midrange).

3180µs: 50 Hz (low frequencies).

5. Power Supply

Dual-rail supply (±15V or ±12V).

Use low-noise regulators and ample decoupling (100nF ceramic + 10µF electrolytic per rail).

---

Detailed Component Selection

Op-Amps: OPA2134, LM4562, AD797 (for MC cartridges).

Resistors: Use 1% tolerance or better.

Capacitors: Use low ESR and low tolerance (1%-5%).

---

Would you like detailed circuit diagrams or PCB layout advice?

 

Simply an amazing amount of information for 5 minutes work. 

I might just build it out of interest.

I can see big changes in the HFi industry with designs driven by AI.

Edited by Anodecap
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