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Arkless 640P "Dr T Mode"/current input version interest check

Back to the GTI from the Iso - much more joined-up, a generally more enjoyable listen. The GTI loses a bit in bass definition, but the clarity of the mid's……. By my reckoning that should mean the GTI beats a P75 by some margin, in the system here, of course.
 
Vinny said:
Back to the GTI from the Iso - much more joined-up, a generally more enjoyable listen. The GTI loses a bit in bass definition, but the clarity of the mid's……. By my reckoning that should mean the GTI beats a P75 by some margin, in the system here, of course.
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My experience was similar, I didn’t really find myself focussing on things like bass, midrange etc, because it just presented a broad, convincing and engaging musical event. I might hope that the Turbo mods might help with the bass grip, a bit, perhaps?
 
Vinny said:
I could lift the lid, but is the GTI all discretes, Jez?
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At that price? It's all op amps. Obvs I've designed a valve/transistor hybrid all discrete high end current input phono stage.... to be filed away with the hundreds of other designs that won't see the light of day!
Much of my higher end stuff uses valve/SS hybrid circuitry.
 
Sue Pertwee-Tyr said:
My experience was similar, I didn’t really find myself focussing on things like bass, midrange etc, because it just presented a broad, convincing and engaging musical event. I might hope that the Turbo mods might help with the bass grip, a bit, perhaps?
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I don't think it has any problems with bass grip really.... the Arkless 640P has very tight controlled bass but is obviously a different model. Turbo mods won't make any difference no. FWIW it measures flat within 0.1dB right down to 20Hz which is as low as I've tested it to but will actually be accurate to below 5Hz.
As I've said before carts are likely to respond differently to the effectively short circuit that they see with a current input MC stage and so different people using different carts may well be getting quite different results!
 
Arkless Electronics said:
I don't think it has any problems with bass grip really.... the Arkless 640P has very tight controlled bass but is obviously a different model. Turbo mods won't make any difference no. FWIW it measures flat within 0.1dB right down to 20Hz which is as low as I've tested it to but will actually be accurate to below 5Hz.
As I've said before carts are likely to respond differently to the effectively short circuit that they see with a current input MC stage and so different people using different carts may well be getting quite different results!
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I would tend to concur, indeed I thought the bass was exceptionally accurate in a very pleasing way; it was one of the most immediately obvious differences switching from my DIY 834p.

I did try four (actually five, but seeing if a HOMC would work with it was more an exercise in curiosity) cartridges with the GTI and cartridges do make a big difference, mostly to the gain! This can be a bit of a nuisance at the extremes, I had the thought actually while changing those jumpers in a p75; had you considered such an arrangement in the GTI to tweak the gain for low/med/high impedance coils Jez? The other differences I think are fundamental to the character of the cartridge, I'm not sure the stage 'imposes' its own character on things in the same way some phone stages do. I think this is something the Dr T approach is good at, the cartridge isn't affected or effected by the load it sees as it doesn't see one, just a virtual short. I have long had the same impression with P75s and there is a similarity to the 'sound' though the p75 and GTI with the same cartridge, but the latter resolves more detail, has a significantly lower noise floor and just does everything a little better!
 
djftw said:
I would tend to concur, indeed I thought the bass was exceptionally accurate in a very pleasing way; it was one of the most immediately obvious differences switching from my DIY 834p.

I did try four (actually five, but seeing if a HOMC would work with it was more an exercise in curiosity) cartridges with the GTI and cartridges do make a big difference, mostly to the gain! This can be a bit of a nuisance at the extremes, I had the thought actually while changing those jumpers in a p75; had you considered such an arrangement in the GTI to tweak the gain for low/med/high impedance coils Jez? The other differences I think are fundamental to the character of the cartridge, I'm not sure the stage 'imposes' its own character on things in the same way some phone stages do. I think this is something the Dr T approach is good at, the cartridge isn't affected or effected by the load it sees as it doesn't see one, just a virtual short. I have long had the same impression with P75s and there is a similarity to the 'sound' though the p75 and GTI with the same cartridge, but the latter resolves more detail, has a significantly lower noise floor and just does everything a little better!
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I'm not going to be making gain user adjustable no. The present gain seems to work with a good range of carts and with the version in the demo unit it is not easy to change gain. The version Foxwelljsly has makes it rather easier.
 
Is there anyone else who wishes to try the demo unit? If considering one of these in the future you need to try it now, whilst it is on it's rounds as it were, as anyone asking to hear it after it has come back to base will be turned down.
 
Arkless Electronics said:
Is there anyone else who wishes to try the demo unit? If considering one of these in the future you need to try it now, whilst it is on it's rounds as it were, as anyone asking to hear it after it has come back to base will be turned down.
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Am I allowed it back to see how successful my mission to improve the obvious deficiencies of my P75 in the wake of it's last departure were? It is now Teddy Reged, the "any old wall wart will do" narrative that used to prevail with them is clearly nonsense... and has better earthing and sounds completely different. I'm fairly sure your design will still be significantly superior, I'd be interested to see how much of an improvement I have made with the actual reference I was remembering :D !
 
Arkless Electronics said:
Is there anyone else who wishes to try the demo unit? If considering one of these in the future you need to try it now, whilst it is on it's rounds as it were, as anyone asking to hear it after it has come back to base will be turned down.
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I would like to Jez at some point that's convenient for you - I use a standard P75 mk2 here in 'Dr T' mode daily, I'm not bothered about the other modes as I'm settled on Dyn cartridges - would a slimmed down Dr T version be a good from your perspective?
 
djftw said:
Am I allowed it back to see how successful my mission to improve the obvious deficiencies of my P75 in the wake of it's last departure were? It is now Teddy Reged, the "any old wall wart will do" narrative that used to prevail with them is clearly nonsense... and has better earthing and sounds completely different. I'm fairly sure your design will still be significantly superior, I'd be interested to see how much of an improvement I have made with the actual reference I was remembering :D !
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I want it to go to people who have never heard it before really. Oh and any old wall wart WILL do! External PSU's are largely irrelevant to sound quality other than in the cases of equipment so crude it has no on board regulation.
 
gavreid said:
I would like to Jez at some point that's convenient for you - I use a standard P75 mk2 here in 'Dr T' mode daily, I'm not bothered about the other modes as I'm settled on Dyn cartridges - would a slimmed down Dr T version be a good from your perspective?
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Right now is good if you PM me your details. Although to get interest I used the "Dr T" bit in the title I really don't like to see it personally... the specific topology they name "Dr T" Is one the most bog standard and common bits of circuitry known to man and it should not be named after anyone! Transimpedance is the correct technical term for it in fact. Mine cannot be any further stripped down as it is already MC only and transimpedance only!
 
Arkless Electronics said:
Right now is good if you PM me your details. Although to get interest I used the "Dr T" bit in the title I really don't like to see it personally... the specific topology they name "Dr T" Is one the most bog standard and common bits of circuitry known to man and it should not be named after anyone! Transimpedance is the correct technical term for it in fact. Mine cannot be any further stripped down as it is already MC only and transimpedance only!
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I understand - marketing gets in the way of an awful lot ;) What I'm not getting I think is how the loading options differ in standard mode and whether that's a significant expense for you...
 
Arkless Electronics said:
I want it to go to people who have never heard it before really. Oh and any old wall wart WILL do! External PSU's are largely irrelevant to sound quality other than in the cases of equipment so crude it has no on board regulation.
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With your design I’m sure that’s true, these older Dynavector stages are very primitive though, their later designs have a much more sophisticated power supply on a separate board. I think my next bit of fiddling will be to take the on board SMPS power supply out of the equation on the board altogether and put Teddy reged supplies to where needed :D
 
gavreid said:
I understand - marketing gets in the way of an awful lot ;) What I'm not getting I think is how the loading options differ in standard mode and whether that's a significant expense for you...
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Erm... the Arkless GTI doesn't have a standard mode and there are no loading options as transimpedance units don't use loading at all...
The Arkless 640P has no transimpedance mode and is a "normal" mm/MC unit with loading set by loading plugs. A set of loading plugs comes with it and further ones can be ordered to any value for MM or MC carts or made by the user.
 
Arkless Electronics said:
....
it should be borne in mind that the McKinie head amp and tweaked croft pre together are a prob £2K + phono stage and are here being compared to the standard £285 GTI!
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I’m a cheap-ass Jez - my Croft Micro II (serviced by Glenn when bought) and any of my 3 McKinnie’s cost less than that :) Admittedly it was around 14 years ago I bought the Croft, And haven’t factored my time to mod it ( parts were cheap), cheap ones no longer seem available. Even the McKinnie’s have jumped in price now - people actually seem to research on the internet nowadays...sadly :)
 
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