View Full Version : Croft Integrated Phono conundrum
mikecole
24-05-2014, 13:11
I wasn't sure if this should go in the Analogue Art section or here. Feel free to move it.
I received my Croft Integrated Phono about a week ago and find that this thing is a bit of a conundrum. I don't think I have ever had as much of a problem getting something to sound "right" as this. This was supposed to replace a Rega Brio-R, but maybe not. My current system, which I have had for a couple of years now, is an LP12/Ekos 1/Dynavector 10x5, a music server feeding a Logitec Squeezebox going to a Metrum Quad DAC and fed into a pair of Harbeth P3ESRs. I have about 40 hours on the Croft so far.
To me, this is a lot like how I remember my Naim kit presenting the music, kind of propulsive and very little body or tone, mostly leading edge and very little decay. The big difference is that, although this has the impact and propulsion and gobs of detail, not once did I ever have the urge to tap my foot to the music. With the Brio, my foot starts tapping from the first note. Another thing I did not like, at least thru the phono stage, was that the center image was way too far recessed unless I had the speakers very close together - I had trouble understanding the vocalist sometimes. It seems to be a bit harsh sounding with the speakers so close together though.
After tearing my room apart, moving speakers and sub all over, playing with settings and cables, mixing and matching equipment, my conclusion is that I don't love the amp section (but only in conjunction with the phono stage), but the phono section by itself is decent (certainly better than the Brio's phono stage). Currently, I have it set up as a phono stage only feeding the Brio. While not ideal, it better approaches what I like to hear. It seems like the phono stage and the amp together do not make a good pair, at least in my room with my equipment (and my ears).
The odd thing is that I like what the amp portion does for my digital music. I get the impact, fullness and color I want - better than what the Brio gives me. If the phono stage did this same thing, I would be a happy camper. It seems like the phono stage has a highly tailored sound to it, which makes me think maybe the Dyna 10x5 is not the right cartridge for it. Unfortunately, I like the Dynavector sound, it does the tone and PRaT in equal measure. And this is about the most I care to spend on something that gets replaced every couple of years.
I think I can see how it is supposed to sound if everything is set up just right, but I have failed to be able to accomplish that. I can also see that maybe my preferences are just not aligned with the way the Croft presents the music. If anybody has any tips on anything I can try to maybe improve the sound, I am open to suggestions. As it is, I may end up selling it and possibly taking a look at the Rega Elex-R when it comes out as I seem to like the Rega house sound. If the phono stage is improved, maybe it is worth a listen. As far as keeping the Croft as a phono stage, I like things simple and a one box integrated is where its at for me.
Firebottle
24-05-2014, 14:07
Hi Mike,
I have recently had the good fortune to listen to a Croft 25R and to my mind you are describing exactly the failings of the phono stage.
See this thread for another viewpoint http://theartofsound.net/forum/showthread.php?32548-Firebottle-valve-phono-stage.
Being a technical chappie I have realised the equalisation network in the Croft is not RIAA accurate. I have worked out a modification to correct this if you or a friend are competent with the soldering iron.
The modification only involves 6 new components, let me know if you want the details,
:cool: Alan
rubber duck
24-05-2014, 16:01
Another thing I did not like, at least thru the phono stage, was that the center image was way too far recessed unless I had the speakers very close together - I had trouble understanding the vocalist sometimes. It seems to be a bit harsh sounding with the speakers so close together though.
Given that the phono integrated is essentially two boxes in one, it should sound very close to the 25/7 combination. Your experiences suggest that something is wrong and you should get it looked at as this is the complete opposite to my experience with Croft. I own a 25 Basic which I bought to try primarily as a phono stage. There is a fresh, open, immediate quality which reminds me of my Audio Research SP10 II (minus the power, heft and authority). Anyone who's heard the SP10 II will realise this is saying something. To my ears, there is no difference in character between the line and phono stages of the 25 Basic, and no perceptible deviations in RIAA equalisation between the Croft 25 Basic (or 25) compared to other phono stages I've had on hand.
fiddlemaker
24-05-2014, 16:10
As there's a bit of a thing at the moment about whether the Croft RIAA eq is accurate I'd planned to measure it this weekend. But then I just put a couple of records on and it all sounded so bloody great I decided I couldn't give a hoot.
mikecole
24-05-2014, 16:36
Alan, although I have a soldering iron and have done a bit of soldering, I think I would place myself into the "incompetent" camp. Besides, I would not want to mess with something that costs that much money (and that my wife has not found out about yet).
Jeff and fiddlemaker, I am wondering how our views could be so different. I have read so many good things about Croft that I just had to try it out, but have not had heard what you guys appear to be hearing. What TT and speakers are you guys using?
rubber duck
24-05-2014, 17:02
Hi Mike, don't think the TT or speakers explain the difference in what we're hearing. I currently run a Technics SL1210 with a variety of amps including Series 7 into Elipson Planet L speakers. I've also had similar results with Mordaunt Short and JPW speakers. If you bought your Croft new from a dealer I'd take it back to have it looked or at least compare it with another unit.
fiddlemaker
24-05-2014, 17:24
I agree with Jeff. It sounds like something is faulty.
is it possible your speakers are wired up out of phase?
In my experience, Croft amplification majors on realism,solid imaging and utterly convincing presentation- the whole "illusion of music" thing. I've never had harbeths, but I know they are supposed to go well with croft amps.The Dynavector cartridges work fine with the croft phono (used to have one). I honestly think something's broken or not wired up correctly here.
Just one other point for folks to note, including Mike, is that ALL Croft equipment phase inverts the signal. Therefore, ensure that you have compensated for this by reversing the polarity of the speaker cables, either at the amp or speaker end, whichever is easier, as otherwise things will not sound as it should!
However, in some systems the effect will be more noticeable than others. In my system, it's a no-brainer. Glenn should really pop a note inside the boxes of all new kit, letting customers know about this.
Marco.
The Grand Wazoo
24-05-2014, 23:44
....ensure that you have compensated for this by reversing the polarity of the speaker cables, either at the amp or speaker end, whichever is easier, as otherwise things will not sound as it should!
Oops....unless you use a Croft pre and power amp, surely?
Nope, it's relevant in my system only with a Croft preamp. I compensate by reversing the polarity of the speaker cables on my power amp (black to red/red to black). The improvement in sound quality, by doing so, is NOT subtle!!
Marco.
The Grand Wazoo
24-05-2014, 23:53
No that's not what I said:
If you own a Croft pre and a Croft power amp it is different. The pre inverts phase. The power inverts phase too. If you swap the speaker cables round, you will have inverted phase 3 times. That leaves you with inverted phase.
If you wire the speakers correctly, then phase will be corrected.
If you only have a pre or a power, then yes, you should invert the phase elsewhere, as you do.
Absolutely. I was just pointing out that all Croft equipment inverts phase (in case folk didn't know or it was a possible reason for substandard performance). Phase-inverting is a key design principle of Glenn's, done in order to reduce the amount of gain stages used, and thereby simplify the signal path :)
Therefore, when using a piece of Croft equipment with other gear, make sure that the polarity of your speaker cables is reversed further down the chain, for optimium sonic performace!
Marco.
The Grand Wazoo
25-05-2014, 00:15
Well yes, but the way you worded it might have misled those with a pre/power combination. And it's not just Croft who do this - Quad and Conrad Johnson, for example.
Sure, I accept that. I'm simply flagging up the issue of Croft phase-inverting for anyone who may benefit. Every bugger will certainly know now!! :D
Marco.
walpurgis
25-05-2014, 00:20
How do you detect or measure the phase of a pre-amp or power amp? I don't know, so I'm asking.
mikecole
25-05-2014, 03:06
Yep, makes a big difference. I would not have known about it except that JA mentioned it in the Stereophile review. BTW, I made a big breakthrough by thinking way outside the box (for me anyway). A couple of years ago, I was having problems with my system at that time. I finally figured out that by moving my system so that the speakers fired down the short side of the room instead of the long side, it sounded much better. A few weeks after that though, I sold my amp and speakers and got the Brio and Harbeths, which also worked in this configuration. I decided today that maybe it was not an absolute that all speakers would sound better that way, but maybe that particular amp and speakers did. This was a different amp. I moved stuff around and have the speakers firing down the long side again. I decided to just concentrate on digital this time and, man, was I surprised. This sounded more like what I expected to hear. Of course, the Jack Daniels helped me relax enough to listen to the music instead of the sound. The presentation is now more transparent, cohesive and lets me tap my foot again. I will work on the analogue side of things tomorrow. It is still a bit dynamic, but maybe I had moved more towards the pipe and slippers crowd without knowing it. As it stands now, this amp may be a keeper after all. I wonder how many people give up on gear not knowing that the room can make such a difference.
How do you detect or measure the phase of a pre-amp or power amp? I don't know, so I'm asking.
You'll need to direct that at one of our Techy chaps, Geoff (perhaps start a new thread about the subject?) or speak with Glenn himself :)
Marco.
fiddlemaker
25-05-2014, 08:47
i've been using Croft preamps since 1988 with a variety of Power amps (croft and non croft). Never found this to be an issue, never felt the need to reverse my speaker connections. It may be audible, I don't know. But certainly not enough to prevent you enjoying the music if you forget.
Sure, John, but if you know about it, I guess you may as well connect things up correctly, as intended by the designer :)
I'd been using my Croft preamp the 'wrong' way (or rather my power amp connected up the 'wrong' way with it) for years, until one day Glenn visited, whilst delivering my preamp, after it had been upgraded with a new off-board PSU.
We sat and listened for a while, and everything sounded great. Then he got up, went over to my system and changed something (I didn't know what it was), and we played the track again... There was an instant improvement, in terms of soundstage width and depth, vocal projection and a notable increase in overall clarity.
Furthermore, any time I've dismantled my power amp, and have forgotten to reverse the cables, after listening for a short while, I always realise that something isn't quite right, which is usually the point where I look round the back of my amp and realise my mistake! Fixing it always returns the sound to how it should be. Friends visiting, who also have hi-fi systems, have noticed the same thing, so I'm definitely not imagining it.
In my system, music just sounds 'wrong', and my system 'off colour', unless the speaker cables on my power amp are reversed, in order to compensate for the signal phase-inverting of the preamp.
Marco.
Sure, John, but if you know about it, I guess you may as well connect things up correctly, as intended by the designer :)
I'd been using my Croft preamp the 'wrong' way (or rather my power amp connected up the wrong way with it) for years, until one day Glenn visited, whilst delivering my preamp, after it had been upgraded with a new off-board PSU.
We sat and listened for a while, and everything sounded great. Then he got up, went over to my system and changed something (I didn't know what it was), and we played the track again...
There was an instant improvement, in terms of soundstage width and depth, vocal projection and a notable increase in overall clarity.
Furthermore, any time I've dismantled my power amp, and have forgotten to reverse the cables, after listening for a short while, I always realise that something isn't quite right, which is usually the point where I look round the back of my amp and realise my mistake! Fixing it always returns the sound to how it should be. Friends visiting, who also have hi-fi systems, have also noticed the same thing, so I'm definitely not imagining it.
In my system, music just sounds 'wrong' unless the speaker cables on my power amp are reversed, in order to compensate for the phase-inverting of the preamp.
Marco.
Some folks out there may get a shock after reading some of this thread regarding phase inversion with Croft equipment. Like you said Marco, the difference when the system is correctly phase inverted is not subtle. It is not always mentioned when folk buy Croft amps, or at least forgotten in their excitement to hook them up!:)
If you have not correctly adjusted your amp connections to take into account Crofts phase inversion then be prepared for a pleasant surprise. As you have pointed out Marco it makes a huge difference to the whole presentation of the music!
fiddlemaker
25-05-2014, 09:55
Some folks out there may get a shock after reading some of this thread regarding phase inversion with Croft equipment. Like you said Marco, the difference when the system is correctly phase inverted is not subtle. It is not always mentioned when folk buy Croft amps, or at least forgotten in their excitement to hook them up!:)
If you have not correctly adjusted your amp connections to take into account Crofts phase inversion then be prepared for a pleasant surprise. As you have pointed out Marco it makes a huge difference to the whole presentation of the music!
I'm always prepared to try new things. Next time i try a non-croft power amp I'll try it with the phase both ways round. If it makes any difference at all I'll thank you for your insight. If it makes a *HUGE* difference i will paint my bottom blue and display it in the window of Selfridge's, Oxford Street.
I'm always prepared to try new things. Next time i try a non-croft power amp I'll try it with the phase both ways round. If it makes any difference at all I'll thank you for your insight. If it makes a *HUGE* difference i will paint my bottom blue and display it in the window of Selfridge's, Oxford Street.
Ok, It might not be a Huge difference but it is certainly noticeable. Its like listening to your speakers when the are out of phase.
I don't want to see your arse painted blue in any shop window John :lol:
If it makes a *HUGE* difference i will paint my bottom blue and display it in the window of Selfridge's, Oxford Street.
Lol - let's hope, for all our sakes, that's the case - simply for the sheer entertainment value! Will you pop it on YouTube, too? :D
More seriously, it's not just Glenn's amplifiers that phase-invert the signal, but also his standalone phono stages. Therefore, if one buys his RIAA phono stage, and uses it with a non-Croft preamp and/or power amp, the same rules will apply!
Marco.
fiddlemaker
25-05-2014, 10:06
No, James, your speakers being out of phase (with each other) really is a huge difference.
And I'll have you know i have a perfectly delightful derriere.
rubber duck
25-05-2014, 14:52
If you own a Croft pre and a Croft power amp it is different. The pre inverts phase. The power inverts phase too. If you swap the speaker cables round, you will have inverted phase 3 times. That leaves you with inverted phase.
If you wire the speakers correctly, then phase will be corrected.
If you only have a pre or a power, then yes, you should invert the phase elsewhere, as you do.
So what should the OP do in terms of a Croft integrated? Will the phase be inverted or not?
The Grand Wazoo
25-05-2014, 14:59
I'm not really in a position to know, but I'd think commonsense would indicate that it would be correct.
Since connecting a pre/power together causes the phase to be correct, you'd think that the integrated would do the same. In building the unit, it's only a matter of getting the colour-coding on the speaker terminals the right way around after all.
No , the Phono Integrated has 1 tube less than the pre and power together, so it's absolutely "polarity inversed" :rolleyes:
And it really made a big difference her in my home on Harbeth's.
And this was also confirmed by Glenn per Email just a few weeks ago
Here in the Netherlands all sounded pretty good after a week...that is...
...after polarity reversal and fitting the better sounding standard (Schuko/EU) powercord from Naim; connected in the correct live/neutral position (2 positions possible on Schuko's!!)
The Grand Wazoo
25-05-2014, 15:36
...............so it's absolutely "polarity inversed"
Well, that's just bloody ridiculous!
Late to this party, but just to say that absolute phase is noticed by some and not others. It's also speaker/room dependant too and some systems really don't seem to mind, so please don't get het up about it.
The Croft pre/power combinations appear to be absolute phase correct from input to output I think, although I could be wrong. The 'usual for me' slightly weak bass is definitely not a 'thing' with a Series 7/Micro 25 for example. I did always find the integrated a bit 'weak' and harsh/strained when pushed, but absolute phase inversion would NOT have helped here I can assure you. Since the recordings we play are all over the place phase-wise, I suspect it's the way some speaker crossovers are wired too and what's in each path, positive and return, but obviously can't prove this either way.
tubehunter
26-05-2014, 07:50
It depends on the type of the circuit used.
Glenn has used various over the years, some invert some don't.
You really need the circuit diagram.
mikecole
26-05-2014, 11:55
I did invert phase and it made a difference. I try to rationalize that in my head, but I can't except to think that maybe the speakers push when they should be returning to rest. But then what do you do when the recording has inverted phase. That was a big thing quite a while back. It was called the Wood Effect. At any rate, moving my speakers to fire down the long side of the room seems to have fixed things. I'll be keeping the Croft.
Nice one, Mike. Good news all round, then! :)
In terms of the phase-inverting, Glenn really should pop a little note, outlining the situation, inside all his new preamps and phono stages. It wouldn't be difficult or expensive to do either.
Marco.
rubber duck
26-05-2014, 12:22
Now I'm confused. I understand that when I use a Croft pre with a (non-phase inverting) power amp I switch the speaker cables around. But what if I run the 25 Basic as a phono stage (line out) into an integrated amp? Will I then need to switch speaker cables again when listening to the CD player where this is connected directly to the integrated amp (and not through the Croft pre)?
fiddlemaker
26-05-2014, 12:25
Nice one, Mike. Good news all round, then! :)
In terms of the phase-inverting, Glenn really should pop a little note, outlining the situation, inside all his new preamps and phono stages. It wouldn't be difficult or expensive to do either.
Marco.
To me, the issue of the importance of absolute polarity makes no logical sense whatsoever. But I'd be the last person to tell someone what they can and can't hear, and clearly the phase reversal issue (as well as the supposedly inaccurate RIAA eq) is something that some people think is important. As Dave says, absolute phase will vary from recording to recording and possibly track to track. If this is important to you then I guess you need to have a polarity reversal switch fitted to your amp outputs, irrespective of whether the amp is phase reversing or not.
I'd also be the last person to tell someone else how to run their business, but I'm sure GC could save himself a lot of hassle/unnecessary emails to answer if he provided a bit of literature with his products, explaining the above issues, and maybe advising on stuff like alternative valves etc. When I got my first micro in the 1980s it came with a photocopied a4 info sheet. I'm sure something like that would suffice. If he doesn't feel able to find the time to do this, I'm sure he has plenty of friends/well-wishers who would volunteer!
> reversed polarity or... inverted phase....? > is it the same or maybe not....?
When I listen through my Cyrus CDplayer (which has an inverting phase pushbutton) with the Croft and I push the button and listen for differences....
I cannot hear sound differences (hear only a switching sound),.... well maybe very little, sometimes (or I think....) > so nothing to worry about for me ;-)
But when I listen through the same CDplayer with the Croft Integrated and do reverse polarity on both the - and + LSconnectors, I can hear definite sounddifferences with in reversed status having more warmth and body and being easier on the ear ;-)
So.....what about this effect....?
Now I'm confused. I understand that when I use a Croft pre with a (non-phase inverting) power amp I switch the speaker cables around. But what if I run the 25 Basic as a phono stage (line out) into an integrated amp? Will I then need to switch speaker cables again when listening to the CD player where this is connected directly to the integrated amp (and not through the Croft pre)?
Hi Jeff,
I think to invert phase correctly with the Croft pre amp into another NON Croft power amp you need to invert the IC connection between the amps, not the speaker connections.
As has been mentioned before if you run a Croft pre and power this is unnecessary as phase will be correct.
To me, the issue of the importance of absolute polarity makes no logical sense whatsoever. But I'd be the last person to tell someone what they can and can't hear, and clearly the phase reversal issue (as well as the supposedly inaccurate RIAA eq) is something that some people think is important.
The bit highlighted in bold is good, because the opposite of that is what really pisses me off (normally spouted by belligerent 'objectivists', who consider that if it can't currently be measured, then it doesn't exist, and therefore one is automatically imagining it :wanker: ). Such rudely judgemental and insulting short-sightedness is responsible for so many arguments and fallouts on forums.
Quite clearly, others and I can hear the difference made by ensuring that correct polarity is in place when using phase-inverting Croft equipment. However, like you say, the results are recording dependant :)
Marco.
Messing about on spotify, I came across the Sheffield Lab test stuff. Different tones, left and right etc. On it there is a bit where it is in phase and out of phase. When it is 'in phase' the sound should be more clearly defined in the middle, 'out of phase' the central voice gets spread more and is less convincing. Anyway, with my speakers 'out of phase' sounded like 'in phase' should have, so thinking I had wired up something wrong inside a speaker I took both apart and checked everything. The wiring was all correct. On listening again this time in phase sounded right. A mystery. Until I moved back about a foot and then the sound went awry again. It seems that 'in phase' and 'out of phase' can be affected by listener position. I learned the hard way with a few hours of pointless wire checking.
fiddlemaker
26-05-2014, 15:04
The bit highlighted in bold is good, because the opposite of that is what really pisses me off (normally spouted by belligerent 'objectivists', who consider that if it can't currently be measured, then it doesn't exist, and therefore one is automatically imagining it :wanker: ), and such judgemental, insulting short-sightedness is responsible for so many arguments and fallouts on forums.
Quite clearly, others and I can hear the difference made by ensuring that correct polarity is in place when using phase-inverting Croft equipment. However, like you say, the results are recording dependant :)
Marco.
I'm glad you approve of the bold bits. I'm fairly convinced that many aspects of what we enjoy/dislike in the reproduction of recorded music are not reflected by the performance of given components in the type of measurements normally carried out. This is why I couldn't give two hoots about the accuracy or otherwise of Croft's current RIAA eq, or indeed whether or not his amplifiers are phase flippers. That sound great to me, that's all I care about.
Re the guy above who can't hear phase reversal at source, but can when it's implemented at his speaker terminals? I'd be interested to hear an explanation for this, if anyone has any ideas.
Messing about on spotify, I came across the Sheffield Lab test stuff. Different tones, left and right etc. On it there is a bit where it is in phase and out of phase. When it is 'in phase' the sound should be more clearly defined in the middle, 'out of phase' the central voice gets spread more and is less convincing. Anyway, with my speakers 'out of phase' sounded like 'in phase' should have, so thinking I had wired up something wrong inside a speaker I took both apart and checked everything. The wiring was all correct. On listening again this time in phase sounded right. A mystery. Until I moved back about a foot and then the sound went awry again. It seems that 'in phase' and 'out of phase' can be affected by listener position. I learned the hard way with a few hours of pointless wire checking.
I think you may be confusing 'out of phase', where the two speakers are wired such that there is a polarity inversion on one speaker compared to the other, and a failure to maintain correct absolute phase, where both speakers are correctly wired, but the positive-going part of the signal waveform causes the speaker cones to move in rather than out.
Speakers wired 'out of phase' display exactly the features you describe: complete lack of focus and virtually no stereo effect. It shouldn't matter where you are in relation to the speakers. Speakers 'out of phase' always sound wrong, whereas speakers 'in phase' will always sound correct. It might be you have problems with reflection off the walls in your listening room, which will change as you move in relation to your speakers.
Deviation from correct absolute phase is more subtle: not everyone can hear the effect; it will vary from recording to recording and even track to track.
tubehunter
27-05-2014, 08:05
like I said some do some don't
http://www.southampton.ac.uk/~apm3/diyaudio/Croft_preamps.html
like I said some do some don't...
i15ALD6fsUU
Marco.
Thanks Barry. I realise I was on a slightly different topic. What I was getting at, was that I could get the speakers to sound more or less right whether one was wired with reverse polarity or not by moving position. I know this should not happen and was a surprise to me. I did not spend long enough to listen to the ultimate subtleties of it but it shows that listening for small changes can be affected by other factors.
Absolute phase reversal at the speaker or amp terminals is as much the way the amp 'sees' the crossover loading as anything else I believe, not just the signal itself. This might help explain a little?
fiddlemaker
27-05-2014, 11:03
Thanks Barry. I realise I was on a slightly different topic. What I was getting at, was that I could get the speakers to sound more or less right whether one was wired with reverse polarity or not by moving position. I know this should not happen and was a surprise to me. I did not spend long enough to listen to the ultimate subtleties of it but it shows that listening for small changes can be affected by other factors.
Phase difference from two sources is intimately related to listener-source path length difference, therefore position.
fiddlemaker
27-05-2014, 11:15
Absolute phase reversal at the speaker or amp terminals is as much the way the amp 'sees' the crossover loading as anything else I believe, not just the signal itself. This might help explain a little?
Not really. Not to me, anyway. I remain sceptical (that reversing phase at speaker terminals can be audible, while reversing phase at source isn't) but open minded and willing to be educated.
tubehunter
27-05-2014, 11:27
lol
http://www.youtube.com/watch?v=KXewIR7Y7cc
When buying my Croft line r integrated from a London dealer over a year ago he reminded me that it inverts phase so I have been running it with my speaker ends with that in mind since new. I would have thought whomever the gentleman in Orlando bought his amp from should have told him the same.
For many, it's not an issue, but for others it is.
To Fiddlemaker, crossovers in speakers are not symmetrical across the + and - lines, having some components in the + line and with a clear path quite often in the return line. When Heybrook brought out the HB2 many years ago now, a point was made that nothing was in the positive feed to the drivers, as the designer Peter Comeau felt that it was better to do it this way. I have absolutely no idea if this was just sales-puff or bunkum, but the speakers worked well regardless and became endearing classics for those that remember them.
Knowing the sonics of the Croft integrated compared to the 25/7 combo, I really do wonder if absolute phase was the issue I had with the former. I look forward to trying it all out again soon.
fiddlemaker
28-05-2014, 09:10
For many, it's not an issue, but for others it is.
To Fiddlemaker, crossovers in speakers are not symmetrical across the + and - lines, having some components in the + line and with a clear path quite often in the return line. When Heybrook brought out the HB2 many years ago now, a point was made that nothing was in the positive feed to the drivers, as the designer Peter Comeau felt that it was better to do it this way. I have absolutely no idea if this was just sales-puff or bunkum, but the speakers worked well regardless and became endearing classics for those that remember them.
Knowing the sonics of the Croft integrated compared to the 25/7 combo, I really do wonder if absolute phase was the issue I had with the former. I look forward to trying it all out again soon.
But aren't terms like "return line" and discussions about polarity rather meaningless in a floating circuit like a loudspeaker crossover?
(in that at any given instant the red terminal may be more positive then the black one, but at another instant the situation will be reversed)
tubehunter
28-05-2014, 18:04
'nothing was in the positive feed to the drivers'
http://www.diyaudio.com/forums/multi-way/92628-q-heybrook-hb2-xo.html
To Fiddlemaker, crossovers in speakers are not symmetrical across the + and - lines, having some components in the + line and with a clear path quite often in the return line. When Heybrook brought out the HB2 many years ago now, a point was made that nothing was in the positive feed to the drivers, as the designer Peter Comeau felt that it was better to do it this way. I have absolutely no idea if this was just sales-puff or bunkum, but the speakers worked well regardless and became endearing classics for those that remember them.
It sounds like bunkum in an engineering sense.
Music is AC not DC so there is in effect no + terminal no - terminal, the markings just serve help with connection phasing. AC signals travel both ways in the circuit.
A note to the OP that hasn't been covered yet - your cartridge is a HOMC I think? I ran a DL110 into a Croft MM stage in my vintage micro II a way back - it sounded good, but I always felt it needed more gain (& I also preferred the dl110 into Naim MC cards rather than MM). However, I moved to a LOMC instead - initially with SUTs, now with a head amp. I love the Croft phone stage :)
fiddlemaker
01-06-2014, 19:01
A note to the OP that hasn't been covered yet - your cartridge is a HOMC I think? I ran a DL110 into a Croft MM stage in my vintage micro II a way back - it sounded good, but I always felt it needed more gain (& I also preferred the dl110 into Naim MC cards rather than MM). However, I moved to a LOMC instead - initially with SUTs, now with a head amp. I love the Croft phone stage :)
Could I ask why you moved on from SUTs and what head amp you're using?
Although I'm currently living very happily with a 7 mV output Decca, it would be handy to know what mc options work well with the Croft phono stage.
However, I moved to a LOMC instead - initially with SUTs, now with a head amp. I love the Croft phone stage...
Ditto (on all counts), Richard. In my case, the head amp in question is from Paul Hynes, powered by one of his large off-board PSUs, called the SR5. Point-to-point hardwired, all valve Croft MM phono stages sound absolutely gorgeous – and when used in conjunction with a high-quality LOMC cartridge/head amp, it is truly an enthralling listen :)
SUTs can also sound outstanding, but even when optimally matched, sonically and electrically to their partnering cartridge, in comparison with the best MC head amps, they can sometimes sound a little euphonic. However, a Croft valve MM phono stage/LOMC cartridge, through a top-notch MC head amp = musical heaven; and in a way I've not heard so far from any solid-state MC stage alone.
Marco.
Could I ask why you moved on from SUTs and what head amp you're using?
Although I'm currently living very happily with a 7 mV output Decca, it would be handy to know what mc options work well with the Croft phono stage.
Mine is a Swiss designed implementation of the John Curl Vendetta design (by a former technician of John's) - McKinnie RO III.
I made DIY SUTs initially, using BD xers - they were very good - but transient response from the head-amp is much better, and the Vendetta design is also super quiet.
I'm using it with a Linn Asaka currently - a sublime combo.
Marco - agreed, with knobs on :)
To OP - my experience is HOMCs (well, to me that means Denon DL110 - I have 2 as backups, love them!) do not give their best into all MM stages.
'nothing was in the positive feed to the drivers'
http://www.diyaudio.com/forums/multi-way/92628-q-heybrook-hb2-xo.html
Thanks for that - shows how not to believe a designer in salesman mode - back in the day, Peter and Stuart called on us personally!
camtwister
02-06-2014, 12:20
The link in post 52 is a discussion that neatly encapsulates the objective and subjective approaches to evaluation of design.
I think I’ll expand my thoughts on this in Geoff’s related thread, in which a general discussion of absolute polarity takes place. (http://tinyurl.com/mrp69eb)
Hopefully, it’s useful to summarise in one post, for those concerned with the maintenance of polarity within the amplifiers discussed, that:
i) all of Croft’s current range of standalone pre and power amplifiers in standard tune invert absolute polarity, as confirmed in writing to me by Glenn in May 2014. This does not apply to all of the superseded models.
ii) The processing of signal polarity by Conrad Johnson amplifiers is dependent upon the model, both in current and older designs. For example, the EV1 amp maintains absolute polarity (as confirmed in the original literature) and the ET3 is phase inverting (as stated on the manufacturer’s website).
The link in post 52 is a discussion that neatly encapsulates the objective and subjective approaches to evaluation of design.
I think I’ll expand my thoughts on this in Geoff’s related thread, in which a general discussion of absolute polarity takes place. (http://tinyurl.com/mrp69eb)
Hopefully, it’s useful to summarise in one post, for those concerned with the maintenance of polarity within the amplifiers discussed, that:
i) all of Croft’s current range of standalone pre and power amplifiers in standard tune invert absolute polarity, as confirmed in writing to me by Glenn in May 2014. This does not apply to all of the superseded models.
ii) The processing of signal polarity by Conrad Johnson amplifiers is dependent upon the model, both in current and older designs. For example, the EV1 amp maintains absolute polarity (as confirmed in the original literature) and the ET3 is phase inverting (as stated on the manufacturer’s website).
And also confirmed per email from Glenn in last may, the Integrated and Phono Integrated have reversed polarity :-)
Don't know about the Integrated R, but assume it's the same :scratch:
mikecole
13-06-2014, 19:19
Dowser, I have been thinking about the mediocre output of the 10x5 and have been researching MMs and MIs. Looks like the better ones are pretty expensive in comparison to the 10x5. I was thinking about maybe getting a tiny step up amp for the 10x5 just to see if going from 2.5mv to maybe 5mv would make a difference.
Elephantears
13-06-2014, 19:51
Ditto (on all counts), Richard. In my case, the head amp in question is from Paul Hynes, powered by one of his large off-board PSUs, called the SR5. Point-to-point hardwired, all valve Croft MM phono stages sound absolutely gorgeous – and when used in conjunction with a high-quality LOMC cartridge/head amp, it is truly an enthralling listen :)
SUTs can also sound outstanding, but even when optimally matched, sonically and electrically to their partnering cartridge, in comparison with the best MC head amps, they can sometimes sound a little euphonic. However, a Croft valve MM phono stage/LOMC cartridge, through a top-notch MC head amp = musical heaven; and in a way I've not heard so far from any solid-state MC stage alone.
Marco.
I'd be grateful if could share some of your experience of Head amps or SUTs with Croft, Marco. I started a thread which is now in the Analogue section, but I've not had many replies with anyone with direct experience of Croft with SUT.
hifi_dave
14-06-2014, 09:20
I've used/sold many x'mers with Croft amps over the years, from a couple of hundred quid to several thousand. One of the best is from RFC on this very forum. His MCT-1 is excellent and very reasonably priced.
kininigin
14-06-2014, 09:56
Hi Jeff,
I think to invert phase correctly with the Croft pre amp into another NON Croft power amp you need to invert the IC connection between the amps, not the speaker connections.
I Use a Croft Micro 25 with active speakers which have correct phase! How would one go about inverting phase with an IC?
hifi_dave
14-06-2014, 10:09
If you believe it makes a difference, you will need to swop + with - on both incons.
kininigin
14-06-2014, 10:16
I have no idea if it makes a difference! So i would need to un-solder my ic to see if i can here a difference! Think i will just leave it then.
Dowser, I have been thinking about the mediocre output of the 10x5 and have been researching MMs and MIs. Looks like the better ones are pretty expensive in comparison to the 10x5. I was thinking about maybe getting a tiny step up amp for the 10x5 just to see if going from 2.5mv to maybe 5mv would make a difference.
I would agree - but see if someone near to you has something you could borrow, its a pretty expensive experiment to do if you blind-buy the right SUTs or a head amp. As I said, I never actually confirmed my suspicions with the DL110 into the Croft MM stage - but when I had a Naim pre-amp (modified NAC 62) the difference between MM and MC phono cards was night and day for me...MC cards being much better...but not everyone agrees - it's a very subjective thing, depending on what you value sound wise.
Good luck :)
Richard
awkwardbydesign
15-06-2014, 10:15
For many, it's not an issue, but for others it is.
To Fiddlemaker, crossovers in speakers are not symmetrical across the + and - lines, having some components in the + line and with a clear path quite often in the return line. When Heybrook brought out the HB2 many years ago now, a point was made that nothing was in the positive feed to the drivers, as the designer Peter Comeau felt that it was better to do it this way. I have absolutely no idea if this was just sales-puff or bunkum, but the speakers worked well regardless and became endearing classics for those that remember them.
Knowing the sonics of the Croft integrated compared to the 25/7 combo, I really do wonder if absolute phase was the issue I had with the former. I look forward to trying it all out again soon.
Strangely enough, the only time I have heard an obvious absolute phase difference was with Heybrook HB3s! I have no idea if the crossover design was responsible, but if anyone has the HB3 schematic (original 80s version) I would appreciate it. I still have the bass units and wish to remake a pair.
Dowser, I have been thinking about the mediocre output of the 10x5 and have been researching MMs and MIs. Looks like the better ones are pretty expensive in comparison to the 10x5. I was thinking about maybe getting a tiny step up amp for the 10x5 just to see if going from 2.5mv to maybe 5mv would make a difference.
Not sure I'd call the output of a 10XV 'mediocre' myself, as some of the better fixed coil cartridges aren't so different I remember. The 10X IV started life around the same price as the Denon DL110 and the only difference in the V is the reshaped mounting I believe (and remember hearing).
I also remember the DL110 sometimes sounding 'better' into a tolerant MC stage (I'm sure there are genuine reasons for this and believe this was documented somewhere), so maybe the 10XV may do similar (I don't ever remember trying this).
At the end of the day and back to original discussion, the Croft RIAA will either work in one's system or it won't! The more complex Puresound phono stage sounded lovely to me as well, despite/because of the unconventional circuit I believe it uses. Not a fan I'm afraid of the EAR one at similar prices, as it just sounds too full-fat for my tastes.
Powered by vBulletin® Version 4.2.3 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.