Topping Pre90 Review (preamplifier)

[Universal Cereal Bus]

This aside about balanced connections has arguments that are philosophically similar to the original input impedance arguments. There are two competing design considerations. One favors more universal component compatibility (balanced connections; robustly buffered high input impedance), which potentially comes at the marginal expense of complexity and performance. A principal argument for interoperability is the fundamental purpose of the device (an interconnect; a preamp).

Another decision prioritizes lower complexity and expense (unbal. connection; un/under-buffered low input impedance). There may also be theoretical or real SNR improvements; however, compatibility suffers. An argument presented in both on-topic and off-topic discussions is that problematic, incompatible devices in the system are poorly designed. Overall system degradation is the fault of the other device (poor grounding; capacitor-coupled output), not the fault of the design decision under scrutiny. If only all devices in the system are considerately selected, the overall system is just fine and the design decision is vindicated.

It's funny. There are people arguing both sides of this philosophical divide for different topics. Of course, they are not hypocrites; their positions can still be justified and internally consistent because real engineering decisions are much more complex and subtle than the reductionist examples above. Still couldn't help notice it though.

 

[Wombat]

By making sure that you have a solid ground and ground them all. And go looking for ground loops, and ensure they are broken. Ground management isn't rocket science, but can throw the odd curve ball, especially of you have a badly designed bit of kit in the system. But I have never seen a system that can't be cured.

Ah, but then some may have to learn some basics101 about their hobby. Brain strain?

https://www.ranecommercial.com/legacy/library.html#p7AP3c1_2

https://www.ranecommercial.com/legacy/library.html

This is all so old hat.

 

[pma]

Native output of many DAC chips is differential.

That’s correct. And there are DACs that use an extra opamp to make a SE out from its balanced out. Like OP275 behind NE5532. So there is a noise penalty, real noise penalty, not only added ground buzz.

 

[misterdog]

Though this thread is about a balanced preamp. Why every time a piece of balanced equipment is featured we have the same old faces regurgitating the same old mantra from the church of the single ended, I have no idea.

Obviously these people have no intention in buying this product yet they produce reams of 'knowledge' as to why their single ended components 'might' sound better.

This forum is about scientific measurement, not personal opinions. So send some of your 70/80/90's preamps to Amir for testing and we can compare the measures, and use our own judgement.

Otherwise this forum just descends into yet another subjective opinion forum, of which there are plenty.

 

[ElNino]

That’s correct. And there are DACs that use an extra opamp to make a SE out from its balanced out. Like OP275 behind NE5532. So there is a noise penalty, real noise penalty, not only added ground buzz.

I'm curious, would you recommend that SE outs be taken directly from one arm of a differential DAC's output rather than summed by an op-amp?

 

[pma]

I'm curious, would you recommend that SE outs be taken directly from one arm of a differential DAC's output rather than summed by an op-amp?

No. I speak about this. The SE sum is made at the end of the balanced circuitry and it adds noise, especially in case of the parts used.

 

[ElNino]

No. I speak about this. The SE sum is made at the end of the balanced circuitry and it adds noise, especially in case of the parts used.
View attachment 99412

I understand that, but I guess I'm not understanding your overall point. All modern high-performance DAC ICs require a balanced to single ended sum if you want to use them single-ended. (The last high-performance IC that was not inherently balanced was the PCM1704.)

 

[JohnYang1997]

I understand that, but I guess I'm not understanding your overall point. All modern high-performance DAC ICs require a balanced to single ended sum if you want to use them single-ended. (The last high-performance IC that was not inherently balanced was the PCM1704.)

If you ask me you'd get a much more definitive answer.
Modern DACs that are mostly balanced by nature (cs43131/43198 as an exception). ESS for example has lots of common mode distortion and noise to be cancelled out. Thus it's inevitable to have a differential sum. This is also important in headphone amplifiers, some amps just use one arm for their single ended output which creates issue.
At current stage of performance for DACs, I would say differential amplifier has relatively small performance impact considering dac noise, resistor values, driving capabilities of current opamps like lm4562, opa1612. But at top performance level around 1uV, it's starting to limit performance. Resistance can be as low as 330, 680 without hurting distortion performance.

 

[Cujobob]

I recomend buying a nice tubebuffer to put after preamp, if you want to try some tubeyness. But might be cheaper to ge a pre with tube buffer build in. To me the real tubesound comes from output tubes. You should buy a nice stereo radio with tubes to really experience it. I have one from mid 60ies i didnt test yet. B&O, Radionette and Rank Arena are nice units

I own and have owned many tube products, including a Mccalister power amplifier using television tubes to get 75 WPC. Pre amplifiers tend to add just the right amount of distortion to give you the beautiful tube presentation without notes in music that feel rounded off.

 

[pma]

I own and have owned many tube products, including a Mccalister power amplifier using television tubes to get 75 WPC. Pre amplifiers tend to add just the right amount of distortion to give you the beautiful tube presentation without notes in music that feel rounded off.

How do you know that it is a distortion that makes the difference for you? Is not it only a common superstition? Would you try this?

https://www.audiosciencereview.com/...-world-tube-preamplifier-about-2-7-thd.18392/

 

[Cujobob]

How do you know that it is a distortion that makes the difference for you? Is not it only a common superstition? Would you try this?

https://www.audiosciencereview.com/...-world-tube-preamplifier-about-2-7-thd.18392/

Interesting concept, but I don’t use Foobar. I also don’t believe that AB tests in audio are reliable for a variety of reasons I would rather not get into in this particular thread (other than to tell extremely obvious differences). I do support the concept of blind tests, of course, where applicable.

 

[philibuster]

Does it have a balance control?

EDIT: the manual (which is just a sheet), seems to imply that balance can be adjusted from +10 dB to -60 dB:

http://www.tphifi.net/drivers/pre90_ext90_manual.zip

The manual mentions balance control, but there are no directions for adjusting balance. I think there is no balance control.

 

[Harmonie]

The only reason we aren't using optical fibre for carrying all our digital signals between components is copyright/rights management/piracy issues, don't kid yourself otherwise. Performance was/is not a factor. TosLink was the first consumer optical interface and it was quickly realized they were giving away the crown jewels. They learned their lesson fast and gave us a series of non-compatible, crappy connections that constantly need protocol updates and replacements.

We should be using high speed optical connections, standardized for everything but we aren't. Vested interests rule. You've likely got fibre runing down your street carrying all your internet traffic. It runs under the oceans and powers our stock exchanges. Why? Because it's superior.

Just wondering what happened to "glass" optical ? Like AT&T connection ?

 

[Guerilla]

This is why I liked the idea of the Freya+. You can run it normally in passive and enable the tube mode when the mood fits. Admittedly, I have to crank the Freya+ to max volume and utilize my digital volume control if I want audible distortion. I wish it was a bit more tubey, oh well.

Yes I dont hear much difference if I use the tubebuffer or not with my Shiit Saga, but my speakers are unfinished, and only acceptable in frequensyrespons.

 

[Guerilla]

I own and have owned many tube products, including a Mccalister power amplifier using television tubes to get 75 WPC. Pre amplifiers tend to add just the right amount of distortion to give you the beautiful tube presentation without notes in music that feel rounded off.

You are probably right. I mostly know tubeamps from guitaramps where I like the distortion from the power section, but prefer transistor distortion when its used before or in the preamp. Hm.. Now we are talking tubeamp

 

[Vasr]

You are probably right. I mostly know tubeamps from guitaramps where I like the distortion from the power section, but prefer transistor distortion when its used before or in the preamp. Hm.. Now we are talking tubeamp

Most of the "tube guitar amps" use tubes within their pre-amp section to shape the sound and if using tubes in the power amp section (not all do), don't shape the sound all that much, unless you are playing at volume 11.

It is easier to overdrive the pre-amp tube section to variable overdrive compression before clipping than solid state unless you are using a DSP to do amp/speaker modeling or do effects.

 

[win]

It is easier to overdrive the pre-amp tube section to variable overdrive compression before clipping than solid state unless you are using a DSP to do amp/speaker modeling or do effects.

Can you explain why?

Thx

 

[Vasr]

Can you explain why?

Thx

I am not an expert on the electronics but here is my understanding of it. This is for amps designed as guitar amps where you are intentionally trying to shape a limited range of sound not hi-fi equipment where you need to reproduce a wide range of sounds.

Tubes have this relatively wider non-linear behavior before clipping with increasing harmonics so you can get variable and easily controlled level of "warmth" for the "tone" that you prefer rather than a binary between clean and overdrive saturation/clipping. Different vendors select different tubes for what their overall envelope sounds are. By doing this in the builtin pre-amp stage and overdriving them but keeping the output level to power amps attenuated, tube guitar amps can get that overdrive compression tones without having to play at very loud volumes. Driving power amp tubes to overdrive compression would limit it to playing at relatively loud volumes (which is fine only if you were doing a live large stage event where they would still be miked even at close to max volume).

You can emulate this in solid state either by circuit design (the iconic Ibanez Tube Screamer that I have from the 80s being the perfect example) or with DSP (like the Digitech processors which I also use) to a reasonable extent. But before the development of the latter emulators/modelers, tube guitar amps were simple and easy for the tone preferred by guitar players. Even after they were available, professional guitarists have used a combination of effects units and tube amps to get their signature sounds. Whether it is Jimi Hendrix with the solid-state Electro-harmonix Big Muff feeding the amps or Dave Gilmour with different combinations of overdriven units before feeding to tube amps to get that unique and difficult combination of heavily sustained, fat/warm and sweetish distortion (no clipping distortion) tones for his solos. The amps themselves don't need to be driven to full saturation in this case.

 

[Daverz]

The manual mentions balance control, but there are no directions for adjusting balance. I think there is no balance control.

That's too bad. Some recordings have an imperfect left-right balance and can be improved by a slight adjustment of a balance control.

 

[restorer-john]

That's too bad. Some recordings have an imperfect left-right balance and can be improved by a slight adjustment of a balance control.

Most recordings I find are not balanced properly. I think an awful lot of mastering "engineers" are partially deaf in one ear.

If your power amplifier has L/R level controls (like most decent ones do) that does the same job.