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Croft Phono Integrated - overly bassy phono stage?

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

  1. Mumdad

    Mumdad Member

    Hi all, first post!

    To attempt to cut a long story relatively short, I recently found myself in limbo amp-wise and took a chance on a used Croft Phono Integrated, if only to see what tubes can do in a hi-fi setting. It was over budget and I wasn't expecting to keep it really but the minute I turned it on and heard what it was doing for lowly MP3s I knew I'd struggle to part with it. Things sounded slightly scooped with my speakers (KEF R300) at first but swapping the JJ preamp tube for a Psvane brought the midrange forward just enough. Really happy with it for digital stuff.

    The niggle I have is with the phono stage. I was a bit concerned about this based on the notorious Stereophile tests but struggled to find any users who'd measured it or had much to say beyond 'Croft stages are usually flat'. I thought there was a chance something was amiss with the way they'd measured it or that a tube change might help since the response looked pretty similar to the way I remember JJs sounding in a guitar context.

    Sadly though it's definitely quite dark in comparison with the same digital material through the other inputs, even after swapping the phono tubes for Psvanes (though this did help a little). The bass can be overwhelming at times and it's a little lacking in top-end detail. It does still sound very nice, but I'm struggling to enjoy anything as I'm concerned about the neighbours hammering on the door at any minute due to the bass! Cartridge is a Denon DL-110 on a Rega P3-24 and the setup was never overly bassy through my old Audiolab.

    The actual quality is superb, it's just the tonal balance. It'd be a real shame to not use the stage so does anyone know if there's anything that I can do about it? After the tube change I'm a bit out of ideas. I suppose I could go for a cartridge that's tilted towards the treble but that seems a bit of a backwards approach to me and would really limit potential cartridge options.

    Thanks :)
     
  2. The Bish

    The Bish Member

    Hi there,

    I use a Croft 25r and found that using different nos tubes made a big difference to the character, with 5751 black plate Sylvanias from Watford valves really bringing the sound forward and removing the bit of darkness that I recognise from your post. It’s a bit of a fools game though as I went through a few different types before finding the ones I really like. I use an Ortofon 2m black.
     
  3. Mumdad

    Mumdad Member

    Yeah, the Psvanes made a really big difference to the EQ in the preamp (which I'm now very happy with) but not so much in the phono stage, which is about what I expected. I like them there more than the JJs, but the general overly bassy character remains. Since they're a pretty modern sounding tube and very detailed I'm doubtful whether I can tone the bass down enough with further (potentially expensive) experimentation. It's probably a good two or three db too loud for me.

    The phono EQ is passive, I gather, so might it be moddable by someone with the knowledge? I've read that Mr Croft is very good support-wise but I'd feel a bit weird emailing him to basically ask if he'd made a boo-boo and is it possible to fix it, especially since it might be a sore point after the Stereophile thing.
     
  4. The Bish

    The Bish Member

    He is really helpful, don’t think he would mind you asking as he does all sorts of mods to suit different scenarios. You could also contact Adrian at Audioflair who is a Croft dealer who knows these amps really well and can probably recommend a few of his thoughts.
     
  5. Vinny

    Vinny pfm Member

    Glenn Croft is more than helpful and his charges for any work are generally modest.

    I have a Croft pre, but am unfamiliar with any other Croft amp', but am curious about your comment "The phono EQ is passive". The phono input must inevitably have some phono stage amplification and RIAA equalisation. For instance, in my pre, the phono input goes through two ECC83's, and then through the ECC82 line-level/cathode follower.

    I have used several different ECC83's and they change how the music is presented, but do not really affect tonal balance very much. Using a MC into the MM stage, I can say that the two settings on the SUT that I use MASSIVELY affect tonal balance. Presumably you are using the H version of the Denon? Maybe that is part or most of the answer to your problem?
     
  6. TimF

    TimF pfm Member

    I believe on the Croft phono integrated, the phono stage uses two ECC83, the line stage is passive, The third ECC83 is the predriver to the MOSFET outputs. I could be wrong of course...And the Denon DL-110 is a high(er) output MC. Never used one with my Croft’s so no idea how they match up with the phono stage...
     
  7. Old Shatterhand

    Old Shatterhand Odeon Audio user

    Quote from a german hifi magazine audio about the Micro 25 R Pre:
    "Phono zeigt einen minimalen, bei 100Hz beginnenden Bassanstieg bis +2dB bei 10Hz."
    Phono is showing a minimal, at 100Hz starting bass frequency rise up to +2dB at 10Hz.
     
  8. Dowser

    Dowser Learning to bodge again..

    Um...forget a DL-110 feeding a Croft MM stage! When using my DL-110 into my Croft MM I always put it through my McKinnie RO III head amp, when I used Naim phono cards preferred the DL-110 into MC rather than MM cards, and while I love the the DL-110, only ever into MC stages. Many, of course, will disagree :)

    Richard

    Edit to add: running a DL-110 direct into the Croft MM makes it sound like a cardboard box has been put over the speakers :)
     
  9. Mumdad

    Mumdad Member

    I could very well have the wrong end of the stick but I gather the amplification is provided by the tubes and the RIAA EQ is done via passive parts.

    Thanks, that's interesting that someone else has mentioned a bump at least. Still hard to know definitively how they're testing these things though, if it's via the line out it seems like there's some degree of signal loss from the phono stage when the amp is stock? The previous owner of this amp actually had it modded with another tube to prevent that. It does sound like a more than 2db on mine, and way up into the higher regions of the bass.

    Thanks, this is encouraging! I always preferred the DL-110 into the MM of my Audiolab over the MC so figured it would probably be happy enough going into the Croft the same way. Probably showing my ignorance there, I'm more of a 'research an upgrade when something breaks then forget about hi-fi for a few years' guy so I'm not great on the technical side of things (cartridge loading etc.)

    I've actually just imported a DL-301 mkII and intended on getting something like the Rothwell Headspace to feed into the amp. It sounds like I should hold off blaming the issues on the Croft stage until I've at least had a mess around with the DL-110 through that.

    Thanks very much for the input everyone :)
     
  10. Old Shatterhand

    Old Shatterhand Odeon Audio user

    [​IMG]

    Another german hifi magazine LP about the Croft RIAA Phono RS:
    A small increase at the bass, a dip at the presence area and a recognize able increase above 20kHz.

    BTW: I like Croft very much.
     
    Last edited: Jan 6, 2019
  11. Zombie

    Zombie pfm Member

    Just tip the cartridge a bit forward
     
  12. Cyreg

    Cyreg pfm Member

    The Croft Integrated/MM has an inverted output on the connectors (black/red) in relation to the input
    (confirmed by Glenn himself)
    With Croft pre/power it's OK though, because of the inverting input of the poweramp!!

    That inverted output changes lightly the soundbalance (from own experience) of the Integrated

    And you should change the normal connection: from red > red and black > black
    into red > black and black > red , but remember on both channels of course! good luck ;-)
     
  13. Mumdad

    Mumdad Member

    Thanks, I should've mentioned that I have the connections inverted at one end already.
     
  14. mattykyuss

    mattykyuss pfm Member

    Telefunken ecc83 will bring it to life.Realy clear with sparkle in the trebble and highs.
     
  15. Hayche

    Hayche pfm Member

    Having a 82 in place of the 83 before the outputs can make it sound very agressive in the bass. I believe this is the left side as you look from the front. Stick a jj 83 in there to balance your output
     
  16. G T Audio

    G T Audio Trade: Distributor and Manufacturer

    The Croft has active EQ not passive! The Denon you are using is a high output MC (if you call 1.6mV high output). Ideally, the Croft RIAA input is an MM phono input, so should be used with MM type cartridge output, i.e around 5mV, not 1.6mV. Proper MC cartridges can be used but you will need to use an MC step-up transformer to get the output to 5mV. Don't use other types of valve in the Croft other than what's fitted in there. 5751's have 30% less gain and might have an impact on the response due to the active equalisation.

    Regarding that measurement curve. The response is only 1.5dB off at 20Hz. There is not a lot of music at this point (only organ and some synth stuff) plus most people won't be able to hear past 30Hz anyway. Don't expect a perfectly flat response with analogue because analogue isn't perfect...
     
    YNWOAN, TimF and slawekt like this.
  17. G T Audio

    G T Audio Trade: Distributor and Manufacturer

    I assume you are referring to reversing the loudspeaker cable connections?
     
  18. Mumdad

    Mumdad Member

    Heh, sounds like 'don't believe everything you read in Stereophile reviews' is the lesson I've needed to learn then!

    Thanks, that was the plan anyway as mentioned with the DL-301 mkii - currently trying to figure out which SUT/headamp to go for. As I said I'll have to put my concerns about the EQ on the backburner until it's more sympathetically set up, though I wouldn't have guessed low output to be the issue purely judging by what's coming out of the speakers. With both the JJ and Psvane tubes it's the first amp I've had where I actually have to reduce the volume when switching over to the MM stage using the Denon HOMCs.

    I'm certainly not demanding perfection but the bass as it stands is really something else!
     
  19. G T Audio

    G T Audio Trade: Distributor and Manufacturer

    So many reviewers today (and not just in HiFi) are not technically trained, therefore they simply don't know, or don't understand audio circuits, or their technicalities or implementation(s) in the design.

    You shouldn't need to touch the Croft as Glen Croft has been making great audio products commercially since the mid-1980s. The RIAA EQ circuit in your Croft will be in the feedback loop of the phono stage so is "active" by design. The advantage of having the EQ in the RIAA feedback loop is this will minimise the effect of component tolerance and variation in the EQ filter...

    People get too hung up on measurements without understanding the basics. RIAA EQ can never be 100% accurate in analogue, therefore if your phono stage is about 20Hz - 20kHz (+/- 0.5-1dB) then that will be OK. Remember, it is understood that a human can only perceive a 0.5dB to 1dB change in level, plus it is very unlikely you will hear below 30Hz and your speakers, even if full range, will be about -3dB down at 20Hz anyway! Typically, if stand mounted (depending on their size/volume) they will be about 3dB down at 40-50Hz, maybe even higher if you have a speaker like an LS3/5a. These figures are measured at a 1-metre distance from the speaker. The further away you sit from the speaker the level decreases even more, typically between 0.5dB and 1dB per additional metre...
     
  20. hifi_dave

    hifi_dave Hi-Fi Retailer

    I've been selling Croft for nearly 40 years and never noticed any "overwhelming bass" or anything like it. I've just answered a similar query on another forum and this "bassy Croft" thing is becoming another 'forum myth'.

    GT's explanation of the measurements and comments should be read and digested.
     

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