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Croft Phono Integrated - overly bassy phono stage?

Discussion in 'audio' started by Mumdad, Jan 5, 2019.

  1. Mumdad

    Mumdad Member

    That was me too Dave, I've replied to you on there ;)
     
  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    It is extremely unlikely that there is any bass boost from the Croft. The RIAA EQ is set by the components in the RIAA feedback network and they are unlikely to fail (possible though... nothing is 100% reliable), especially both channels at the same time! I can confirm from a simulation that the Stereophile RIAA measurements are correct.
    There should be no issues with using a high output MC other than lower than normal output level as most of these carts are lower output than a typical MM cart.

    Do not use the wrong valves in these (or any) amps!! If you put an ECC82 in V2 position (RIAA stage) you will get a big loss of bass and boosted treble! Other valves are chosen to give the best results in the circuit characteristics chosen by the manufacturer.
     
  3. paulfromcamden

    paulfromcamden Baffled

    I'm curious about the suggestions to not use a DL-110 into a MM stage - I thought that was partly the point of a high output MC cartridge?
     
  4. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Not from me. I just confirmed that it isn't a problem in the post above...
     
  5. Mumdad

    Mumdad Member

    No, I'm not adventurous enough for that! As I said in the OP, I'm pretty sure swapping tubes wouldn't have much effect anyway. The JJ and Psvanes are very different but the bass thing remained in the phono stage with my setup. In contrast the Psvanes totally transformed the preamp, though both tubes sounded great there in their own way.

    I'll be sticking with the Psvanes so long as there aren't any longevity issues. Researching and sourcing good NOS tubes is a minefield that I don't think I want to navigate!
     
  6. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I'm against "tube rolling" personally anyway so I'm definitely not the man to speak to about that.... I explained in another thread recently that "tube rolling" (I hate the very phrase! They're valves for a start and what's wrong with "changing" or "substitution"?) cannot change frequency response (putting the wrong valve in can in this case) but that's another story....

    It's extremely unlikely that the fault you report is real I'm afraid.... pretty much the only fault that even could cause it would be for the 470K resistors in the RIAA network to go open circuit.... in both channels... We're talking lottery type odds here.

    Measurement against a reverse RIAA network would confirm or rule out any issues. If you happen to be in NE England I'll gladly check it out.
     
  7. Mumdad

    Mumdad Member

    Oh, I'm not saying for one minute there's an actual fault and I hope I haven't given that impression. Everything is clearly operating as intended and I gather his stages are generally designed to complement Decca cartridges which obviously offer a pretty different presentation to the one I'm discussing. If there's a fault it's probably mine for plugging my pervious turntable setup into it and expecting it to be well balanced. I was just trying to figure out where to go from there really.

    I can assure you that the big bass with vinyl is very real in my setup though! It only takes a few seconds of listening to pretty much anything to notice it and comparing something like the Analogue Productions Pet Sounds vinyl to the lossless version (both really well mastered by Kevin Gray) makes it particularly stark.

    Whether it will persist after changing to and properly loading the DL-301 II is the question at the moment but I'll have to wait until I've got the SUT/headamp to find that out. If I'm still having trouble it sounds like contacting the man himself would probably be the way to go.
     
  8. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Aha... I was under the impression that you were saying it was faulty yes....

    There's nothing about the circuitry that makes it more or less suitable for any specific cart I have to say.

    You could look at the siting of your TT with regard to acoustic feedback which could be spoiling the bass end ... A rigid wall shelf on a supporting wall is ideal.
     
  9. johncee

    johncee pfm Member

    I've been using Croft amps for almost as long (in fact I bought my first micro from Radlett Audio back in the early 80s) and I completely agree. I've used god knows how many cartridges with Croft pre amps. HO MC, LO MC with transformers and head amps, MM, MI, never any issues at all apart from HO MCs being a bit quiet due to the relatively low output. The "optimised for Decca" thing is a red herring. Deccas will sound great with a Croft because they are great sounding cartridges (with the usual caveats about arm matching), not because of any special or unique synergy.
    When the infamous Stereophile review is raised, people often fail to mention the fact that both listening reviewers thought the Croft integrated sounded exceptionally good. I can't comment on the validity of the measurements in that review, but I've heard plausible sounding objections about their validity or relevance.
     
    Fretbuzz likes this.
  10. davidsrsb

    davidsrsb pfm Member

    Sounding good does not always mean accuracy and modifying the RIAA curve is the most common tweak you find in amplifiers
     
  11. johncee

    johncee pfm Member

    See counter-arguments above from GT and Arkless.
     
  12. hifi_dave

    hifi_dave Hi-Fi Retailer

    Definitely.
     
  13. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    The power amp section I would expect to measure as badly as Stereophile reported and in exactly the ways they reported. It's intrinsic to the topology and the design decisions made. Stereophiles measurements are generally very good.

    I've read reports from some users of these amps of "edginess", "shoutiness" at higher volumes and/or with less efficient speakers and muddiness/confusion under similar conditions with dense and complicated material such as massed choral works and all are indicative of the high levels of distortion under such conditions.
     
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Neither GT nor myself are saying anything of the sort Johncee.... We are both saying that the Croft's RIAA is fairly accurate (not spectacularly so but accurate enough for inaccuracies to be fairly hard to hear).

    dacidsrsb is quite right of course that RIAA EQ has been known to be tweaked by some less scrupulous manufacturers from time to time to make an amp sound more "impressive". I would disagree as to how common this is though...

    RIAA could be seen as bass and treble controls which are precisely fixed at just the right positions to exactly compensate for the treble boost and bass cut built into the vinyl recording process by the RIAA standard. Obviously it is dead easy to "accidentally" boost the bass a touch too much and cut the treble not quite enough and end up with the classic pleasant sounding "smiley face" EQ!
     
  15. Old Shatterhand

    Old Shatterhand Odeon Audio user

    @hifi_dave: I wouldn't say forum myth because to independent German magazines #7 & #10 measured! the same. And for safety again, I still like Croft very much.:)
     
  16. johncee

    johncee pfm Member

    Davidsrb's implication (and I apologise if I have interpreted this incorrectly) was that the Croft might have sounded good to the stereophile listening reviewers because of the measured RIAA EQ discrepancies. But as you reconfirm above, both GT and yourself are saying that the Croft EQ is accurate enough for the small discrepancies to have little sonic significance. That's the counter-argument to which I refer.
     
  17. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    It is myth... as I explained in some detail above... A 1dB bass boost below 30Hz is not going to be audible.
     
    G T Audio likes this.
  18. hifi_dave

    hifi_dave Hi-Fi Retailer

    Exactly
     
    G T Audio likes this.
  19. johncee

    johncee pfm Member

    I've never heard the Croft integrated. But I hate edginess, shoutiness, and muddiness. These are complete deal breakers to me with any piece of equipment. Never had the slightest hint of this with my Croft 7R power amps. Quite the contrary. I get clarity, transparency, a beautifully natural presentation and the ability to make sense of the most complex recordings at neighbour alienating volumes. Speakers are Neat Elites, 85-87 dB/W/m sensitivity, I think.
     
    Last edited: Jan 11, 2019
  20. davidsrsb

    davidsrsb pfm Member

    But as shown in post #10, 1dB dip in the Presence region is audible and would reduce "sibilance/shoutiness/edginess", 1dB lift at 40 Hz might sound more "solid bass" against a competitor which is already rolling off down there with a warp filter.
    Don't get too wound up about it, loudspeakers are voiced with far more drastic equalisation tweaks.
     

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