When does it make sense to place preamp between components?

[oOBurrowsOo]

I have bought the teac NT 701 (streaming dac pre) and matching AP 701 (power) amp. I have bought them because the components supposed to measure better as my arcam sr250 (as some say measure bad in the channel separation department) and thus have better sound on my Dynaudio special forties.

The manual states the NT 701 has an excellent pre amp build in.

On short term the nt 701 sounds fantastic, but on long term this unit just has no soul. It has a small soundstage (compared to the more expensive NAD M23) and less expressive vocals (compared to the arcam). There is nothing bad about the (extended) high-range though. When I go down in the Dynaudio range (evoke) this gets better because the imaging on those speakers is better so it gets some things it stands out.

From youtube reviews some dudes rave over Dynaudio products to improve in soundstage/soul with a tube preamplifier. I though have no knowledge of elektrics. Should I buy a preamplifier or does it make sense to place lets say a primaluna preamplifier between the NT701 (streaming dac pre) and AP701 (dual mono power amp)? Or is this already handled by the preamplifier in the teac?

regards Burrows

 

[MaxwellsEq]

Hello and welcome!

It's quite tricky to know what to advise you on.

Normally, I would advise against inserting another device in the chain to try and "tune" the sound.

I don't know the Teac products, but really they shouldn't be responsible for "having no soul". It would help explaining how you experience this.

 

[NTK]

A properly functioning preamplifier, tube or otherwise, would have no significant effect on the so called "soundstage" (or "soul", or whatever). When I say "a properly functioning preamplifier", I mean one that is engineered to perform the function of outputting an accurately amplified version of the input signal, and to perform other functions such as volume adjustment and source selection.

Humans perceive sound source locations by the differences in timing (interaural time differences, ITD), levels (interaural level differences, ILD) and spectral modifications by our heads and ears (the head related transfer function, HRTF) in the sound our ears receive. Reverberations, depending on the timing relative to the initial direct sound, give us the cues on the sizes of the sound sources and of the space (the venue) we or we perceive to be in.

Straight electronic amplification has effectively zero influence on the spatial cues in the reproduced sound. The spatial cues embedded in the recording -- the source material have by far the biggest influence. Rooms and loudspeakers (due to their different sound radiation patterns -- i.e. directivities) can also affect perceived soundstage significantly. Narrow directivity loudspeakers and "dead" rooms usually give more compact and focused (pin-point) sound images. Wide directivity loudspeakers in "live" rooms usually give more diffused images that give a feeling of more "enveloping" and spacious sound.

There are also techniques/signal processors that "enhance" the spatial imaging of sound. You may want to check out the various BACCH threads (such as this and this). BACCH uses crosstalk cancelation (XTC) for the enhancement, and is designed to work with 2 channel reproduction. It limitations is that it work well only for one listening position, and for the best results, requires a one-time individual calibrations/measurements of the listener and head tracking during listening (of the one listener). Upmixing is an alternative method but it will require a surround setup.

Thus to change the "soundstage", you can experiment with:
1. Different placements of your loudspeakers and listening positions.
2. Room acoustic treatments.
3. Loudspeakers with different directivities (e.g. wide dispersion front firing, omnis, panels, open baffle, etc.)
4. XTC such as BACCH
5. Upmixing

 

[Jas0_0]

Welcome @oOBurrowsOo

I had the exact same dilemma about 6 years ago (before I discovered Audio Science Review)

I had a Linn Majik streamer DAC, a Nord power amp and Proac speakers. Music just seemed a bit lean and lifeless. Just like you, I thought adding a tube pre between streamer and power amp would solve it.

It didn’t.

Then I thought the power amp was to blame so switched it for a tube power amp.

That didn’t work either (and selling the Nord is still my biggest hifi regret).

Then I thought it must be the Linn, so I switched it for a DAC and Mac as source.

That didn’t work either.

Then I started learning about room acoustics, and got some heavy curtains.

That worked.

Then I got a UMIK mic, and started measuring my system and applying EQ.

That really worked.

I learned that electronics have a far smaller impact on sound quality than the speakers, and the interaction of those speakers and the room.

Hope that helps.

 

[Jaxjax]

I run Dynaudio & NAD C658 streamer/pre. I would try Dirac or other EQ system. EQ is your friend & makes a huge difference. Measure & go from there & suit to taste. I don't use much EQ but it made a huge difference & haven't touched settings in years.

 

[Chrispy]

Depends on your needs, I find pre-amps handy switching centers as well as help with things like phono eq. Have no desire to play around with a tubed one, tho.

 

[radix]

From youtube reviews some dudes rave over Dynaudio products to improve in soundstage/soul with a tube preamplifier. I though have no knowledge of elektrics. Should I buy a preamplifier or does it make sense to place lets say a primaluna preamplifier between the NT701 (streaming dac pre) and AP701 (dual mono power amp)? Or is this already handled by the preamplifier in the teac?

There are very few youtube channels I would take buying advice from. Most audio reviewers are either all hype or everything is the best or worst.

If one thing sounds better than another, the likely causes are: it's louder, the speakers or listener are in a different position, the listener expects it to be better. Or, the manufacturer actually built-in a sound (like poorly designed tube systems that add distortion).

A lot of modern audio hardware is so good that the differences are beyond human hearing. Of course, you could assemble a system that is sub-optimal in some way (components are less than ideal together), but I don't think that's too common (no evidence of that).

Your room (geometry, soft stuff vs hard stuff, carpets, curtains, windows) makes the biggest effect on the sound. Then the speakers. Everything else is a tiny effect.

 

[Keith_W]

Hello, and welcome to ASR.

If I read you correctly, you are saying that your Teac NT701 / AP 701 combo sounds worse than the Arcam SR250 receiver with the same speakers, and it is lacking "soul", with a smaller soundstage, and less expressive vocals?

Unfortunately, things like "soul", "soundstage", and "expressive vocals", are not quantifiable and mean different things to different people, so it is difficult to understand what you are describing. I would ask whether you compared the amplifiers at the same volume and with everything else equal, e.g. any processing done by the Teac and Arcam turned OFF. I would closely examine the settings in your Teac vs. Arcam to make sure it is not interfering with the signal in any way.

 

[GXAlan]

I have the Arcam SR250. It has 96 kHz Dirac built in and plenty of power for most applications. Were you running Dirac on your Arcam? If so, the “soul” you likely experienced was a more natural bass rendition.

 

[Scytales]

@oOBurrowsOo,

The Dynaudio loudspeakers you refer to (although you didn't mentioned the specific model out of the Evoke range) are inefficient to very inefficient loudspeakers, their sensitivity being in the 84 to 88 dB SPL/1 W/1 m depending on the specific model.

You didn't specify the size of your listening room(s) or told about your preferred type(s) of music , but, to my mind, the Arcam SR 250 isn't sufficiently powerful to drive those Dynaudio loudspeakers to anything remotely close to realistic peak loudness levels with good recording material of simple acoustical instruments, such as a very well recorded solo piano. I refer to peak levels at the attack of each tone, not mean loudness level. The TEAC AP 701 is barely adequate only for some models of the Dynaudio Evoke range.

I would suggest that your Arcam SR 250 use to produce sound colourations due to the triggering of protection circuits such as limiter or dynamic compressor during peak music levels, and that you have become accustomed to this subtly distorted sound. The TEAC being more powerful would produced much less distortion.

 

[MattHooper]

Welcome @oOBurrowsOo

I had the exact same dilemma about 6 years ago (before I discovered Audio Science Review)

I had a Linn Majik streamer DAC, a Nord power amp and Proac speakers. Music just seemed a bit lean and lifeless. Just like you, I thought adding a tube pre between streamer and power amp would solve it.

It didn’t.

Then I thought the power amp was to blame so switched it for a tube power amp.

That didn’t work either (and selling the Nord is still my biggest hifi regret).

Then I thought it must be the Linn, so I switched it for a DAC and Mac as source.

That didn’t work either.

Then I started learning about room acoustics, and got some heavy curtains.

That worked.

Then I got a UMIK mic, and started measuring my system and applying EQ.

That really worked.

I learned that electronics have a far smaller impact on sound quality than the speakers, and the interaction of those speakers and the room.

Hope that helps.

I can totally see how you would have experienced that epiphany and I fully endorse your reasoning.

That said, ironically enough, I had an acoustics/tube experience. (None of the following meant to convince anyone, just my personal anecdote)...

My room always sounded terrific for 2 channel audio. At the time I was between big speakers and was using some old Thiel 02s for music listening. Also, at the time I was using a Harman Kardon integrated stereo amp. Then I decided to outfit it for a projection based home theater as well. This meant that I had to use the wall directly behind my usual listening sofa for the projection screen wall. Therefore I would have to switch everything in the room 180 degrees - sofa on the other end of the room, speakers where the listening sofa was.

So to test out I switched the sofa and speaker positions. The sound went to hell! I couldn't believe it. It sounded thin, sucked out, stale, just yuck! I kept trying to listen for days and I had to admit...I had a big problem. I would not enjoy my system like this. In fact I was thinking of just abanandoning my goal of doing the home theater, or switching the room positions. Then the HK amp died on me so I asked my audiophile pal if he had an amp I could borrow. "Yeah" he said. "I have this little tube amp I saved from someone throwing in the garbage. It's supposed to be something of a classic but I never used it and don't know if it works." It was an Eico HF-81, 14W/side, integrated amp.

I hooked it up to the speakers and...holy cow! I couldn't believe it. The sound was rich, full, "organic," punchy, vivid, smooth. It sounded goregous! It was almost like some of the acoustic issues were fixed. For days I couldn't stop listening it sounded so beautiful.

Then I was like WTF is this thing? Then I looked it up, and found all the rave reviews of this old tube amp. Ha. Who woulda thought?

Anyway, now it was obious it was still possible for me to enjoy the sound in the new arrangment, so I went forward with everything. I've always looked on that little Eico as the "little tube amp that saved my home theater room." Later I bought my own Eico HF-81 and loved it. Though ultimately I stuck with CJ tube gear. And an acoustic renovation of the room fixed the acoustics issues anyway.

So in my case, it seems, the things that didn't work for you, kinda worked for me.

As for the OP: It's hard to beat NTK's response.

I have both a solid state and a tube preamp in my system, as I often like to inject some preamp tube sound. That's generally not what most people are in to around here though. "not the job of amplification to mess with the sound." I don't necessarily see it that way, in terms of a strict rule

 

[Waxx]

A preamp can have advantages, but is not essential in all setups (certainly not as seperate). An integrated amp has a preamp build in.

But a preamp can help to make various sources compatible with the amp on input voltage and impendance, and makes it easy to switch between sources, and very often the volume knob is in the preamp as not all sources have that (only dacs have a volume out control.) And for a turntable (vinyl) you also need a lot of extra gain (30-80dB depending on the cell used) and the RIAA eq to translate the signal on the record to line level (what the amp expect to see at the input). That is the main reason people use preamps.

And for colouring the sound (for subjective quality), it's also often the best place. But not everybody (and certainly not here) wants that. The colouring is always a degradation of the original signal, mostly by adding low order harmonic distortion (the warmth).

I don't know your gear, so i can't tell your specific case. But what i wrote above is applicable on that anyway.

 

[MaxwellsEq]

Going back to the OP, swapping one set of electronic amplifiers for another has resulted in:

... just has no soul. It has a small soundstage ... and less expressive vocals...

Amplifiers can't influence soundstage. Amplifiers should not be able to have any impact on vocal expressiveness.

Assuming it's not placebo or cognitive bias, a likely thing that's happening here is a lack of level matching when making comparisons.

Adding an extra amplifier device in the chain, assuming it's well designed and operating properly should not be able to make the soundstage larger nor make vocals more expressive, unless it changes the end-to-end levels back to the OP's original gain structure.

 

[restorer-john]

The entire reason preamplifiers (as a standalone HiFi component) existed was to be the "nerve centre" for connecting various sources, all having different output levels, impedances and signal routing requirements (tape decks etc back in the day). Most preamplifiers had excellent phono stages due to the ease of obtaining much better performance when pulling out a RIAA stage from an (integrated) amplifier and placing it in a low level box.

Control over the tone, filters, balance and of course volume meant a preamplifier was essential when sending all of those connected sources to a power amplifier. The preamplifier must have plenty of adjustable extra available swing to be able to deal with low level recordings and low output front ends.

Plenty of ASR members have one, maybe two sources and they are already high level (2V or greater), so preamplifiers aren't going to help them, unless they are dealing with low gain power amplifiers. But guys with plenty of vintage source gear, will need a quality, well designed preamplifier.

 

[JiiPee]

I'm not familiar with the said Arcam and Teac units, but if everything else - speakers, speaker placement, room acoustics, listening position - remained absolutely same, there should be no significant change in "soundstage", or "imaging", unless we understand the meaning of those words differently.

Some possible causes I could think of are:
- Arcam used Dirac signal processing. This could easily make the difference.
- You are now listening at lower sound level than with the Arcam
- For some reason, the Arcam added significant amount of distortion to the sound, and You were accustomed to the effect that it created.

As others have pointed out, properly implemented electronics used in amplification do not make significant changes to "soundstage" or "imaging".

 

[MaxwellsEq]

Another justification for a preamplifier is to act as an attenuator between a "software volume control" on a DAC that's feeding a power amplifier directly. These DSP volume controls can accidentally go to 100%.

 

[restorer-john]

Another justification for a preamplifier is to act as an attenuator between a "software volume control" on a DAC that's feeding a power amplifier directly. These DSP volume controls can accidentally go to 100%.

I've seen the mess when that happens- more often than people would hope. Voice coils and ripped spiders, toasted amplifiers and very scared people.

But I and others have warned over and over. More fool anyone who gets a random "default 0dB volume event" or a "factory reset on startup" issue.

 

[brunes]

Another justification for a preamplifier is to act as an attenuator between a "software volume control" on a DAC that's feeding a power amplifier directly. These DSP volume controls can accidentally go to 100%.

I got a bit nervous about this and decided to go with a preamp (diy Neurochrome) between DAC and poweramp.
I made a single input / output preamp as I don't have any other sources.
Bit of peace of mind - not sure how it affects sound adding something to the chain. Also the potentiometers can vary in quality, in particular to channel matching. Not sure I notice any difference to be honest.

 

[oOBurrowsOo]

Explaining have no soul:
I started in hobby ICE. When I experimented with speakers, i found out the more they cost the less they sounded. It's the experience you get when the main speakers are being high passed at 80 Hz or the mids are being restricted by a too low efficiency of the speakers. Maybe there is a way to measure if there is a highpass filter somewhere in my chain.

My hifi setup is as below picture special 40 on stands, with the sub6 with peq from the nice Andrew Robinson tutorial and the nice special forty preset. My room size is very large on the left, but plays to a wall in the right.

The most people (NTK: preamplifier funtioning properly) don't see any added value in adding a preamplifier to the system. This is important info for me thanks for the input and posting your experiences on this topic.

@NTK The post was very interesting and beyond my knowledge. I always thought the power amp should biggen the 'soundstage' because the source is always recorded in a room that is smaller than your living room. Now that you post that a 'big soundstage' has more to do with the quality of your hifi chain it makes sense to me.

Humans perceive... ears recieve. I know that if you close one ear, the other can still receive phase information, so you can still localize sound. Your brain compares the sound (phase) on the outside of your ear with the inside of your ear and makes a calculation in a milisecond, that is very impressive.

Experiment with:
Placement: See drawing. I have found that the sound 'collapses' if the speakers have no same distance to the back wall. The 'soundstage' is best when I sit in a triangle with my speakers. Moving the speakers to the wall leads to the exaggerated bass which i like
Room acoustics treatment: #1 on my list. I am going for curtains on the wall and maybe ceiling sound absorption will help.
Loudspeakers with different directivities: Last resort if I have some evidence my special forties are not up to the task. I once had black MB Quart speakers in my car with a nice bumped bass. Sort of like the special forties have.
XTC such as Baccht: Very nice theories to study and a nice advancement. I hope the price will drop a bit in the future. And I will study the theories. I also like the Troels gravesen site for making your own speaker and also want to study the amplification theories of the class D full feedback amplification.... enough to read.

I have the Umik and think of measuring some things when I make changes to my room.

I will study sound theories and alter my listening room. And then measure changes. As I am taken over by the audio virus.

The arcam sr250 has class a operation beneath some watts so there is much to like (exept for some class a leanness in the bass regions). The thing that struck me was at some testing forum they tested it and concluded that the unit measured not well enough for critical listening. If you measure something and it doesn't measure 'well' maybe they have found something that sounds 'well' but measures 'not well'. Like 'if it rains' it 'is clouded' so 'if it doesn't rain' it 'is not clouded'.

Lots of hifi babble to conclude it already has a nice preamp build in but much work is to be done in the room acoustics department.

 

[oOBurrowsOo]

It's a bit embarassing I did set the subwoofer volume much too high. It sounds much less 'liveless' and more open now. I guess 0 db is a bit too loud.