[Thermionic]

 
I know this is an old thread, but Mr Gilmore mentioned the Crown / Amcron IC150 pre-amp at the beginning, and as this device has received a lot of negative press over the years on various forums I thought I would contribute some personal experience of this preamp.
 
Firstly I suppose I should say that while an audio enthusiast I do not claim to be an audiophile. I have been reasonably content to stay with my Quad valve amps and ELS57 speakers, or a Quad 303 and LS3/5a’s. For headphones I mostly use a Graham Slee Solo and Senn. HD650’s with Equinox, though have others including a pair of Stax Lambda Signature Pros. I listen to Jazz and what was once called ‘serious’ music and go to concerts fairly regularly. So I like to think that I know what live music sounds like. Indeed even my modest equipment can at times sound better than a live event that’s had a poor p.a. system.
 
I have owned the Crown / Amcron IC150 preamp for about 15 years, and have happily slotted it into various mostly vintage systems at home. It is quiet, has useful tone controls, and the ‘panorama’ feature is quite effective at providing crossfeed for headphones. These days I use an Audio Research LS7 or a home built passive switch box and pots based around a Hewlett Packard 44476A RF switch. These perhaps sound better, though not a slap-you-in-the-face amount of better.
 
So I feel that the derision for the IC150 is not entirely justified, though it’s cause is not helped by the proud statement on the front panel; ‘Integrated Circuit Stereo Console’. Not a good thing to boast about these days perhaps. Though let’s not forget that most of our older LP’s and CD’s were recorded and mixed with equipment stuffed full of ICs (and perhaps still are).
 
However, the most important thing to know about this preamp is that to achieve best performance the volume control must be at the 2pm position or ‘later’, and this is stated in the handbook. Crown intended these units naturally to be used with their power amps, which have input gain controls. The idea was that you set the preamp volume control at 3 o’clock and the adjusted the power amp gain control to suit your normal listening level. Turning the volume control on the preamp down seems to introduce a mild loudness effect. (The volume pot is a possibly unique device that has ‘tapped’ sections connected to the loudness circuit.)
 
The IC150 was also designed to drive professional 600 Ohm amplifiers inputs (though unbalanced) if required, and so has quite a high output. I found it fine when driving the insensitive Quad II power amps that need about 1.5Volts, but if you use it with say a Quad 303 you will need to provide attenuation. At low volume levels the sound does indeed suffer; noise goes up, distortion goes up and the frequency response has a high frequency boost that suggests an in-built loudness effect. 
 
Last year I measured my preamp with a professional Lindos audio test set (as used by the BBC etc). I found that at a 3pm volume position it had a ruler straight FR from 20 to 20Khz and noise and distortion figures were similar to the specification (low). At this setting I have A/B it with a straight wire and found no detectable difference when listening on the Lambda’s. I am not saying that someone with more experience and better ears than I could detect a difference, but I am saying there was no ‘screeching’ or nasty integrated circuit sound. I tried some more modern BB OPA606’s that I had in the spares box and found no effect on FR and distortion, though the noise level dropped by 5dB.
 
However, if one then plotted FR, distortion and noise at all the volume control settings picture was different; above 2pm the IC150 performed essentially to specification but below 1pm the HF response starts to rise and noise and distortion increases. 
 
So, if one used this preamplifier in an ad hock situation with a sensitive power amplifier not having gain controls. It would be highly likely that the preamp would sound bright and rather nasty, but use it as it was designed to be used and it all falls into (a nice) place. After all this equipment was used and appreciated in a time that to many these days consider was a ‘golden age’.
 
I rest my case.

 

[nektarios]

hi all!
I m new around and while i was loooking for "aswers" about "circuits" i found that old article which has the same question with me..
so i have an "audio" magazine which describes a few high-end head amps and gives informations about their "power stage"..
Creek obh-21se:2xLm7171 price:224euros
LehmannRhinelander:1xLm49720 and a pair of bd139,bd140 price:370euros
MI V-can:1xOPA4134 and a pair of BD140-BD139 price130euros
Precide S.a ergo AMP1:just an ic BA5415(an IC that i find inside TVs that i repair and doesn t cost more tha 1euro) price:300euros!!!
Project HeadBox seII:2xOPA2134 and 2xTI(TPA)6120a2 price:270euros
until here as u already know these boxes need separate power supply...
Vincent khv-1 pre:1xOPA2604,2x12AX7 and a pair of A1930+C5171(triple hybrid)price:650euros
and the cherry on cake....
CIAudio vhp1-vac-1:here they just say that it has a current-feedback ic(which i suppose it must be TPA6120)price for vhp-1+vac-1:980 euros!!!!
op-amps everywhere even inside current-feedback ics.Easy ,cheap circuits but in a shinny box...!
I m sure that anyone who owns a "high-end" head amp from a big name "around",he  ll be very qurious on what it has in it and then..."hmm i think that circuit i ve seen it in a diy article..."oups!!
Ok i can accept that they use audiophile parts,that they might have done a research on it and we have to pay that knowledge,but so high prices???
I think i m going to make one by myself.....
 

 

[spritzer]

Things are indeed pretty dire and there is very little will to rock the boat and expose all those who sell badly performing and overpriced garbage.  The sad part is that when the market was smaller and better regulated then the amps were better.  Fully discrete SS amps and tube amps that had enough power to drive headphones. 

 

[nektarios]

i agree with u my friend,but now that there is "internet" and people can get informations and learn things(not  properly all the times...)companies should be more carefull on what "they" r doing.Especially when there is so much competition.They should try for better things(unfortunatelly there is a "China" among")but i suppose that they couldn t keep low prices ,not that they r doing it now but i suppose that head amps would be much more expenisive if there wasn t the  "made in china" but more quality in them.and we should not forget that there was more "clear" sound back to old days and not the digital sound that we have to do many,many things so to take the best of it!so maybe then the circuits was more "discrete" and need more electronic parts(not so good for the audio signal) to achieve a good amplification but the sound was pure".now circuits might r smaller with less lines on a circuit board but what sound these circuits have to amplify and take the best part of it?
Anyway sorry if i tired u with all these, i m not an expert but now that i m looking around for a head amp i see to much money for an empty box...with electronic parts that they r very cheap.i suppose u can imagine how cheap are for them who make huge "productions".!if I buy one "blue velvet" 8euros u can calculate how much do they buy the companies that they need  thousands of them!!

 

[jcx]

there may be a few stand alone 3rd party headphone amp makers that have 1000's of units a year production - but only at the lower end - "high end" "audiophile" headphone amps are very much Boutique items - I doubt any one model US$1000+ dynamic headphone amp sells greater than few hundreds a year
 
Stax ES amps are likely an exception - and they make the headphones - possibly you could include integrated DAC/amps like the Benchmark - but I bet lots are being used with yet another amp by those with audiophile pretensions
 
there are a few threads discussing the reasons for high prices in low production volume headphone amps - it isn't all about greed - even in mature small manufacturing businesses 3-5x parts cost is considered "competitive" pricing for products, and "high end" audio product costs all come from case work and "jewelry" (audio manufacturer's really do use this term for gold plated connectors, silver wire...) - the actual amplifying electronics often cost less than the power supply or "audiophile" volume control

 

[spritzer]

There is always something to be said about simple circuits but the signal path can also be very short but with a lot of ancillaries tacked on so that it just looks complicated.  Take for instance the Stax SRM-T2, arguably the most complicated headphone amp ever designed but the signal path is very simple.  Then we have people calling opamp circuits simple and with short signal paths... 
 
Seeing an Alps RK27 in a high end anything drives me up the wall.  It's a cheap part and not a very good one at that.  I wonder if people have ever heard of TKD, Penny&Giles, Alpha or Alps own RK50.

 

[nektarios]

hmm...do u agree that sometimes things are more simple and more "cheap" that "they" show it?and not so sunshine and"hi" as they want us to make beleive it through magazines and articles around?
Maybe in a level of 1000$ maybe something must going on,but is there out someone who take a 1000$ amp and make the same circuit on a simple board not a gold one,used a simple potentiometer and simple jacks and rcas not gold ones and make a blind test?and after that step by step other materials that  might not be so crucial on signal?
I  d like to hear about and if someone has already done it plz give me the link i m hear to learn!!! 

 

[akiroz]

IMO all things labeled "audiophile-grade" are overpriced, it all depends on where you are buying them.
ie. I can buy OPA2134's for $16HKD ~ Aprox.= $2USD each at an international electronic distributor like RS.
 
I have been designing amps for 2 years now and discrete amps are always better in-terms of quality over price, since discrete components have always been very cheap.
However the price of whole amplifiers seem to had nothing to do with production cost.
 
 
 

 

[pabbi1]

Quote:

Seeing an Alps RK27 in a high end anything drives me up the wall.  It's a cheap part and not a very good one at that.  I wonder if people have ever heard of TKD, Penny&Giles, Alpha or Alps own RK50.

We are in lock step on this one. As a lowest common denominator, the rk27 offers an immediate upgrade path, where TKD is the first logical step.