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Topic: Amp question. (Read 45285 times) previous topic - next topic
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Amp question.

Reply #25 –
You can overload analog inputs, and more easily if they're on a portable unit.

Amp question.

Reply #26 –
I need to disagree with the conventional wisdom here.  While differences among amplifiers of the same type (solid state, tube) may be undetectable in blind tests, amps do differ in their ability to drive speakers.  Take a speaker with low sensitivity, and compare a 100 watt Adcom to a 100 watt Bryston (for example). The Adcom would be far inferior.

Amp question.

Reply #27 –
is this the same for the bithead as it would be for any other amp?  What determines how easily it is to overload?  I know I could digitally attentuate but I'd rather not loose the bits, any other way? 

If I get another amp to be used out of the 0404, what do i look for to make sure it can't overload?

Thanks!

Amp question.

Reply #28 –
Quote from: gaillard on
...  He said it was a "hot" line.
...

Usually "hot" means "high voltage". Perhaps he meant the output voltage of your headphone amplifier was much higher than line level, which AFAIK is <= 1V, and would saturate the inputs. Just find the user manuals of the devices and check the specifications.
But please yes do start another topic, would you?

Amp question.

Reply #29 –
Quote from: HbG on
Today i managed to snag a vintage Marantz 1060. I got it because i love vintage stuff, it looks so gorgeous with all those shiny knobs and pretty letters. It's in good condition, despite smelling smokey the volume knob turns silently, and there is no hum. For the rest i'm an amplifier newbie. Another reason for getting it is that one is currently doing over $140 on ebay and i got mine for less than half of that.

It's a nice piece of equipment. I used to have one. The preamp section (inc phono) is reputed to be good and that's how I found it. I didn't like the power amp section. It was noisy for a start. Using the preamp section with a tripath power amp improved things.
Quote
So that's my question, how much does a good amp matter and what and how big are the differences between amps?

Far less than speakers but I think it does matter and is noticeable. Probably not between high end amps but between good amps and regular consumer ones.
Quote
Can one derive what is a good amp just from looking at the stats, like thd, rms wattage, damping factor, capacitively coupled output.... or is there more magic involved?

I have the impression if the noise, frequency response, thd and imd (and crosstalk) are good the amp should be good. I don't know if that's a theoretical result. It's what engineers seem to care about in any case.
Quote
When googling i always see amps reviewed in audiophilespeak. I never see "This is a good amp because of statistic x". It's this vagueness i'm hoping to see cleared up here.

The market would become too competitive if everyone went by measured characteristics.

Amp question.

Reply #30 –
Quote from: CSMR on
Far less than speakers but I think it does matter and is noticeable. Probably not between high end amps but between good amps and regular consumer ones.
Do you have ABX results that demonstrate this? All the positive results I have seen one of the amps is broken, or very bad (note that most consumer amps these days don't count as very bad), or were performed using a very artificial test (like extreme clipping).
Quote from: CSMR on
Quote
When googling i always see amps reviewed in audiophilespeak. I never see "This is a good amp because of statistic x". It's this vagueness i'm hoping to see cleared up here.

The market would become too competitive if everyone went by measured characteristics.
The market for high end amplifier would cease to exist if everyone went be measured characteristics.

Amp question.

Reply #31 –
CSMR, i've heard in various (hopefully unconnected) places that the preamp and phono section are good but the power amp is less so. Given the other comments here i'm not so keen on spending money on a power amp though (unless i need more power ), speakers first.
I don't mind the noise and it doesn't seem that noisy to me, i had a slight hum through an earth loop but solved that by putting a "mantle current filter" (don't know the translation) in my tuner's cable input. When i disconnect the amp from everything but the pc so it can't hum from groundloops and i analyse the spectrum with my pc, there is still a hum at -87dB but it is inaudible even with the volume all the way up.

The only thing it doesn't seem to like is my 16 ohm headphones, i have to twist all the knobs and hit all the sound related buttons to get a reasonable sound out of it. It's probably not made for low impedence 'phones?

Quote from: cabbagerat on
The market for high end amplifier would cease to exist if everyone went be measured characteristics.

That is a bold statement, could you post links to the ABX results?

I read Rod Elliot's articles on impedence too, thanks. Had looked on his site but hadn't come across those yet. It seems source impedence is one of the areas where amps differ which may or may not become audible depending on the speakers. If anything he acknowledges the difficulty in measuring audible differences between amps because of the vast number of parameters.
Veni Vidi Vorbis.

Amp question.

Reply #32 –
Quote from: cabbagerat on
Quote from: CSMR on

...
The market would become too competitive if everyone went by measured characteristics.
The market for high end amplifier would cease to exist if everyone went be measured characteristics.

Marketing and engineering... reads like a Dilbert cartoon.

BTW I just found a photo of the 1060 on Wikipedia!
http://de.wikipedia.org/wiki/Bild:Marantz1060.jpg

Amp question.

Reply #33 –
Quote from: HbG on
The only thing it doesn't seem to like is my 16 ohm headphones, i have to twist all the knobs and hit all the sound related buttons to get a reasonable sound out of it. It's probably not made for low impedence 'phones?

I'm sounding like the president of the Rod Elliot fan club in this thread - but here is another one of his projects that I like - Headphone adapter for power amplifier. Of course, it's not suitable for all phones (only ones that expect 120ohm source impedence), but worked well for me until I built my headphone amp.
Quote from: HbG on
Quote from: cabbagerat on
The market for high end amplifier would cease to exist if everyone went be measured characteristics.

That is a bold statement, could you post links to the ABX results?
Ok, fair comment. The point I was trying to make is that, if people judged objectively (based on measurements and blind listening tests), then the comically expensive sound equipment market is likely to shrink a huge amount.
Quote from: HbG on
I read Rod Elliot's articles on impedence too, thanks. Had looked on his site but hadn't come across those yet. It seems source impedence is one of the areas where amps differ which may or may not become audible depending on the speakers. If anything he acknowledges the difficulty in measuring audible differences between amps because of the vast number of parameters.
Judging amps based purely on measurements and blind tests is difficult, but judging them in the stereophile "make up a load of nonsense" way is just wrong. As with most things, the truth lies somewhere between the extremes.

Amp question.

Reply #34 –
Quote from: seditious3 on
I need to disagree with the conventional wisdom here.  While differences among amplifiers of the same type (solid state, tube) may be undetectable in blind tests, amps do differ in their ability to drive speakers.  Take a speaker with low sensitivity, and compare a 100 watt Adcom to a 100 watt Bryston (for example). The Adcom would be far inferior.


Please elaborate on how the Adcom will be 'far' inferior in this example. Which measured paramaters/behaviour will the Adcom come up short on?

-Chris

Amp question.

Reply #35 –
Quote from: cabbagerat on
Quote from: HbG on

The only thing it doesn't seem to like is my 16 ohm headphones, i have to twist all the knobs and hit all the sound related buttons to get a reasonable sound out of it. It's probably not made for low impedence 'phones?

I'm sounding like the president of the Rod Elliot fan club in this thread - but here is another one of his projects that I like - Headphone adapter for power amplifier. Of course, it's not suitable for all phones (only ones that expect 120ohm source impedence), but worked well for me until I built my headphone amp.

The Rod Elliot fanclub? Sign me up!
I was thinking of exactly the same thing although i hadn't found his headphone adapter yet. I just wanted to use a 1 and 4 ohm resistor in series as a simple voltage devider, i think that's better suited for low impedence 'phones even if wasteful in power.

I'd agree that comically expensive equiment is likely to have a high snake oil rating. Personally i don't mind buying anything as long as the product is worth what i paid for it.

After thinking about everything that's been said some more i view high end audio as similar to high bitrates in lossy coding. It gives additional insurance that you won't hear a difference. In that light it makes sense that people pay for better equipment than is strictly necessary when they can afford to do so.
Veni Vidi Vorbis.

Amp question.

Reply #36 –
Quote from: cabbagerat on
... until I built my headphone amp.
...
if people judged objectively (based on measurements and blind listening tests)...

Cabbagerat,
There are many subjective criteria by which one can judge the quality of an amp, among other things, the aesthetic/design aspects are important.
Also, as you yourself did, there is sometimes the pride of building something - certainly not an objective criteria, is it?
I am quite certain you did not perform any blind listening test on your diy headphone amp. And if I had just bought a vintage Marantz 1060 amp I would not worry about performing any blind listening test on it either, or measuring its distortion or noise.
I would just do that which HbG did: open it to check the innards visually, and listen to it - preferably with a good pair of loudspeakers.
Rod Elliot is a good reference but he himself prefers the sound of valve amplifiers - although or perhaps because valve amps are known to add a small amount of second-order harmonic distortion (something that the Marantz 1060 with large output capacitors outside the feedback loop will also do, to some degree).
Yes I know about clipping behavior, but a 10W valve amp will "nicely" clip where a 90W mass-produced hybrid amp won't clip at all, so which is better?
So even good engineers are entitled to their subjective judgement - why not the average consumer? And why not consumers in the high-income bracket?
Lab measurements and ABX blind listening tests for power amps cannot be done by the average consumer; it takes too much equipment and money, and anyways differences in speakers would overshadow any differences in amplifiers; so they are not a cure-all, end-all means for judging amplifier quality.

Here is just my $0.02: decide on a budget, read the specs, check the brand reputation, find reviews on the Web (preferably those with lab measurements) and exercise that rarest of qualities - common sense - when you choose your next amp.
Imho, the vintage Marantz 1060 was definitely a great find. 

HbG, you didn't mention the brand or model of your headphones, but I would suggest you check http://www.headwize.com/ first, and perhaps check the sales of CMoy amps on eBay.

Quote from: WmAx on
Quote from: seditious3 on

... The Adcom would be far inferior.

Please elaborate on how the Adcom will be 'far' inferior in this example...

Please don't.

Amp question.

Reply #37 –
Quote from: Gigapod on
So even good engineers are entitled to their subjective judgement - why not the average consumer? And why not consumers in the high-income bracket?
The problem comes in when somebody walks in to a HiFi shop with, say $500. They are sold a $450 set of cables and told that they will make their current system 'so much better' - instead of being sold nice, affordable equipment which both measures well and sounds good.

You are right, by the way. I didn't do any listening tests on my headphone amp, but I did some pretty extensive measurements  As you say, there is pride in building something (like my amps) or buying something vintage (like that Marantz), which can't be measured.

Amp question.

Reply #38 –
Quote from: cabbagerat on
The problem comes in when somebody walks in to a HiFi shop with, say $500. They are sold a $450 set of cables and told that they will make their current system 'so much better' - instead of being sold nice, affordable equipment which both measures well and sounds good.
It's been a long time since I've walked in to a HiFi shop. Are there still shops left that allow you to actually try the equipment in your own room before you buy/pay ? I've known a shop like that (long time ago) and they had a very loyal client base. AFAIK they are still in business.
OTOH ppl who don't know much about audio snake oil might not have the courage to go back to the shop and claim that the $450 set of cables doesn't make a difference. I don't think this effect is limited to audio. Nikon and Canon would probably suffer if they would only sell expensive cameras to ppl who really deserve them

Amp question.

Reply #39 –
If i wanted any i'd have to do the measuring before buying the Marantz anyway, but how many people bring with them a reference amp of their own when buying a second hand amp?

I just checked for a CMoy on a dutch trading site, no hits. Ebay lists a few in Germany, i think i may build one myself, but if i do something i want to do it thorough. The PIMETA sounds like a nice and challenging project.
For the record: my current 'phones are Sony EX-71SL canalphone type buds, i can't rule out the possibility of getting other 'phones somewhere in the future though. I don't have a good set of cans yet.

I'd agree with cabbagerat on the cables, after reading some about that and doing the math myself, cables that are expensive beyond their what their build quality warrants are useless. It can get wound up over people paying too much and then proceed to fool themselves into thinking it was worth it. OTOH it's their problem, says the cynic in me.

@Kees: I don't think anyone deserves a $450 cable if it performs no better than a $50 one. An expensive camera is worth what you pay for it, i don't know to what degree that goes for high-end audio equipment?

Thankfully amps aren't like cables.
Veni Vidi Vorbis.

Amp question.

Reply #40 –
I think it's easier to see the difference in visual quality between two cameras than it is to hear the difference between two pieces of sound equipment. Plus, high end cameras are often used because they allow for very large prints to be made from the image, and they tend to have less noise.

Amp question.

Reply #41 –
Quote from: cabbagerat on
Do you have ABX results that demonstrate this? All the positive results I have seen one of the amps is broken, or very bad (note that most consumer amps these days don't count as very bad), or were performed using a very artificial test (like extreme clipping).

That's my impression from what I've read. Also from experience but I haven't used many amps and the not so good ones have had obvious flaws. I haven't seen or looked for any ABX tests. I don't know who would be willing to fund this. An easier approach would be to add distortion digitally and ask with various headphones and speakers at what point (with what measurements) it becomes noticeable.

Amp question.

Reply #42 –
Quote from: HbG on
...
I just checked for a CMoy on a dutch trading site, no hits. Ebay lists a few in Germany, i think i may build one myself, but if i do something i want to do it thorough. The PIMETA sounds like a nice and challenging project...

http://search.ebay.com/cmoy

The PIMETA is a good headphone amp but it seems its specs degrade with decreasing load impedance; I'm not sure it will do too well with your 16 Ohm Sony ear buds. Something with discrete parts (like the one Cabbagerat built) may perform better with very low impedance loads.

http://tangentsoft.net/audio/pimeta/bench/32-ohm.htm

I thought about it for some time and then concluded that most (all I had seen) headphone amp kits are almost as expensive, if not more, than new ones. My second conclusion was that I could buy a vintage amplifier in good condition for about the same money. My third conclusion was that if I was willing to do some soldering/cleaning/tinkering, I could probably buy on eBay a nice vintage amp with some relatively-easy-to-fix problem and a nice pair of vintage speakers for just a little more money...

My dear half (aka the Voice of Reason here at home) interrupted all this thinking by reminding me that I _already_ had a nice stereo/HT setup. 

So: whenever I want to use my Sennheiser PX-100 headphones (32 Ohms) to check some audio samples (I really prefer to use loudspeakers to listen to music), I just connect them directly to the output of my ALC882 codec - which is spec'd as having headphone buffers anyways (note: not all codecs have headphone buffers; check the datasheet first).

Quote from: Firon on
I think it's easier to see the difference in visual quality between two cameras than it is to hear the difference between two pieces of sound equipment...

I agree 100%.

Amp question.

Reply #43 –
Quote from: CSMR on
...
An easier approach would be to add distortion digitally and ask with various headphones and speakers at what point (with what measurements) it becomes noticeable.

That has been done already, more than a few times since the 70's, and not only for distortion (you can also use filters to simulate different frequency responses, add mixers to simulate different degrees of stereo separation, etc).
The conclusions are surprising: a number of people actually like it when, for example, valve amps add a certain amount of second-order harmonic distortion. Another example: stereo separation of about 30dB is enough for most people. Google for it a little and you can find a lot of interesting data.

Amp question.

Reply #44 –
Quote from: Gigapod on
The PIMETA is a good headphone amp but it seems its specs degrade with decreasing load impedance; I'm not sure it will do too well with your 16 Ohm Sony ear buds. Something with discrete parts (like the one Cabbagerat built) may perform better with very low impedance loads.

http://tangentsoft.net/audio/pimeta/bench/32-ohm.htm


I'll build myself because i want to, even if it costs a little more. I think i'll start with a simple cmoy, as it has low output impedance and is so simple it doesn't require a pcb. Now all i need is a nice tin.
http://sound.westhost.com/project113.htm looks good too, for a tabletop headphone amp.

What does that 32 ohm benchmark say? I can't interpret it very well.
Veni Vidi Vorbis.

Amp question.

Reply #45 –
Quote from: HbG on
...
What does that 32 ohm benchmark say? I can't interpret it very well.

You have to compare the harmonic and intermodulation distortion figures between the no-load, high-impedance headphones and low impedance headphones (they are on three separate pages). You'll notice the distortion figures, while very good without load, rise quickly with lower load impedances. I am not sure whether distortion is inversely proportional to output current but if it is, at 16 Ohm you'll have 0.3% distortion levels or worse.

You may have better luck with some different circuits, for example I have seen a few where the op-amp drives a couple of discrete mosfets, which are mounted on small heatsinks. This is usually slightly less expensive and much less load-impedance sensitive.

The problem with high-performance op-amps is they oscillate quite easily, and just because they don't oscillate on your workbench doesn't mean they won't oscillate later, under different operating conditions. It takes a lot of trial-and-error to get it right, and after you have destroyed a few IC´s it becomes an expensive exercise in frustration. Plus you really need an oscilloscope.

You can avoid a lot of problems by using either an all-discrete design like this one:
http://www.amb.org/audio/ck3/
or the already mentioned design by Rod Elliot.

The CK3 uses very-easy-to-find BD139/BD140 power transistors which cost ~20 cents each if you buy 10.

It's not a portable design; neither is Elliot's. In both cases the most expensive components will be the transformer and the printed circuit.

Imho the original CMoy and mods are still best if you want a weekend project for a portable, battery-powered headphone amp.

Note: if you want the simplest possible headphone amp look at the TDA1308 (~$3):
http://docs-asia.origin.electrocomponents....66b80427e19.pdf
(it can drive 16 Ohm loads at < 0.1% THD+N and will survive output shorts for < 20s, can be USB-powered, 60mW, etc)

Amp question.

Reply #46 –
Too late, i've just built my first cmoy! Using a TS922 opamp and a TLE2426 rail splitter.. except they gave me the wrong part or a broken one. With a makeshift rail splitter of wrong spec parts the amp sounds okay but gives loads of DC (my earplugs actually get warm - scary!) and one ear is louder than the other, i suspect the volume pot, it measured odd and it barely does volume adjusting to begin with.

On the bright side there's no noise.

It cost me about 16 euros in parts.
Veni Vidi Vorbis.

Amp question.

Reply #47 –
Quote from: HbG on
Too late, i've just built my first cmoy!
...
It cost me about 16 euros in parts.

For the DC you can temporarily add a 1000uF electrolytic capacitor, but remember to also connect the return wire from the headphone jack to the "negative" rail. Do it before your ruin your earphone plugs...

For the volume control, well... there is the famous "Blue Velvet" pot, but it costs > $10 just by itself... when it can be found at all.

IIRC the original CMoy, following the KISS principle, didn't have a volume control, it just had a fixed resistor, and it used the volume control from the MP3 player.

BTW since you started this thread on the Marantz, I started thinking about getting one myself... I guess I caught the "vintage bug" from you!

Amp question.

Reply #48 –
I solved the DC by thoroughly cleaning the solder joints and draining some solder here and there, there was still some residue in between that shorted out some things, i got rid of some cracking that way too. I'm really not as good at soldering as i thought.
I'm now using a rail splitting circuit with lower value resistors, 2.7 and 3.3kohms but the ground still sinks to .8 volts from the negative rail as soon as i plug the headphones in... The impressive part is it still gives acceptable volume before clipping even at such low voltage.

As for the volume, i soldered around the pot and i still get the problem, i think i must have uneven gain or something, but i checked all the resistors..

Glad you caught the vintage virus now too, if you strike a good deal you won't be disappointed!

Edit: Built a new attempt, fixed the rail splitter proper, it sounds okay now but i'm still left with DC in only the left channel. What's wierder is it gradually decreases with turn-on time. Soldered a cap onto the OP's power pins to combat oscillation and now the DC is split, two thirds of it on the right channel and one third on the left. Cleaned the PCB again, it's drying now.

Wierdness.

Edit2: Turns out using S39 to solder is a Bad Idea, washed the entire circuit again, it's okay now.
Veni Vidi Vorbis.

Amp question.

Reply #49 –
Quote from: HbG on
...
Glad you caught the vintage virus now too, if you strike a good deal you won't be disappointed!
...

Well, I can see you really caught the DIY virus! You can test the circuits using a protoboard, I think that would avoid a lot of problems with solder resin.

Anyways, since you passed me the vintage virus, here is what I ended up with, for the princely sum of 30 euros:
http://gigapod.free.fr/marantz_restoration.html