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

[Tarzan]

@Sue Pertwee-Tyr The Turbo version is extremely forgiving of worn/ rubbish sounding records , which l believe is down to the very full and a very smooth top end- The Turbo is an absolute fantastic phono stage which punches way above it's weight.

 

[Arkless Electronics]

OK, I have just completed a pretty comprehensive A/B test between Jez's demo unit, which is the standard GTi spec and the full GTi Turbo Spec one he has completed for me - which has, in addition to the demo unit, uprated caps (largely a reliability mod I am informed) and the full turbo mods including the uprated op amps which are run, IIRC, in active mode, rather than the passive mode the lower spec op amps are run in the standard version.

I asked him to send this to me as I was convinced there was a slight difference, but I did not know if it was for the better. It turns out it's a difference that makes even slightly worn discs a little worse and good discs a little better.

In the interests of full disclosure, the rest of the system is a Acoustic signature Challenger T/T with a Roksan Nima arm and AT 33 PTG II cart, a Sugden Headmaster Class A pre-amp (also recently refurbished to a very high standard by Jez), a Quad QSP power amplifier and a pair of fully refurbished Kef 104/2 speakers. I have also been doing a bit of casual testing over the last couple of days by switching between the two stages whilst working at home and listening through some Sennheiser HD600 cans and the the Headmaster.

Discs used for the speaker test were Pentangle's Reflections, Beach Boys Surf's Up and Deep Purple's Fireball.

My conclusions? Both stages are undeniably superb and whilst there is a Gnat's chuff between them, there is an audible difference. However, it is marginal and that's in the handling of the high frequencies covering sibilant sounds in the human voice and percussion. The Turbo has a little more headroom here and enunciates these with a little more clarity than the demo unit. This does mean that it exposes groove wear a little more mercilessly. It also takes breathy vocal recordings, for instance, 'Disney Girls' and 'Day in the life of a tree' from Surf's Up, to a slightly more transcendent level.

It should also be noted that this difference was more noticeable via the speakers than through the cans.

The price difference between the two was, IIRC, about £140, which isn't very much. Is it worth it? In our OCD world of extremely marginal gains, yes. I probably spent half that much on a turntable mat, which was, admittedly, stupid.

I should add, by way of testimony, that since first hearing Jez's demo unit I have bought a new cart and arm and about 20 new albums, so this little box has thoroughly reinvigorated my passion for vinyl.

If I could offer one piece of advice to Jez, it would be simplify your product offerings. Keeping it to the recapped GTi and the recapped GTi turbo as I have here would appear to be sensible.

Bom Shanka

Thanks for the comparative review we've all been waiting for there Simon

Fortunately the results are exactly what I'd expected and hoped for... phew..!

The technical bits are rather back to front I'm afraid though.

The one being compared above to the demo unit was a one off/experiment which Simon graciously agreed to be the guinea pig for. As it seems to have worked as intended I feel I can now offer it to anyone interested. The difference between the unit above and the others (standard or Turbo) is that this one has passive HF EQ for the >2KHz section of the RIAA curve whilst the others do it actively. Whilst the differences in the top end will be very slight I believe that the version Foxwelljsly has above is the more correct/natural/accurate of the two.

I shall make the version above available then and at the slightly increased price of £420 compared to £380 for the active Turbo version (the slightly better op amps are both more expensive and a complete PITA to fit and it takes about 1.5 hours just to fit these op amps for purely mechanical awkwardness and electrical fiddlyness reasons).
The standard version (demo unit) is £285 BTW.

 

[foxwelljsly]

Thanks for this, which as a prospective GTI Turbo buyer (Jez, any chance we could have a more descriptive nomenclature?) is of direct relevance to me. What you describe here are sonic differences, rather than musical ones, though. Would you say the increased headroom in the Turbo added to the enjoyment of the music - in other words, was the groove wear a distraction, or irrelevant to the enjoyment of the music and only really noticeable in 'analytical listening' mode? Which would you buy, having heard both, if they cost the same?

The dry lip pop of the vocals on Disney Girls by the Beach Boys was better enunciated on the Turbo, which definitely added to the listening thrill and excitement of this great track. If you have a nice copy of Zoot Allures by Frank Zappa on analogue vinyl and particularly like 'The Torture Never Stops', it's going to sound amazing (I don't but do and will be buying one).

Reflections by Pentangle is a very busy recording and my copy is a little worn. On that the sibilance of Jacqui McShee's s's and t's became a little more distracting when using the turbo.

In both cases the difference was marginal and it took some hard listening to work out what was going on.

By comparison a mint copy of a 60's DG album by Martha Argerich sounded identical on both stages because there was simply no information in that frequency range.

And every record I've tried sounds thrilling on either.

 

[foxwelljsly]

Mmmmm.... very interesting, but makes the decision somewhat harder. I think I'd sacrifice the 'pristine playback' for a more universally even-handed reproduction, as much of my vinyl is s/h or quite old. So probably just the GTI for me. Jez, I'm ready whenever you are

TBH, even my most knackered and worn albums sound better on either of these stages than they ever have - I have a first press of LZ1 which looks like its been emery papered which is properly listenable for the first time. Weirdly, it's only the very slightly worn ones which can sound slightly better on the standard GTi, but it's not universal.

 

[Arkless Electronics]

Thanks for this, which as a prospective GTI Turbo buyer (Jez, any chance we could have a more descriptive nomenclature?) is of direct relevance to me. What you describe here are sonic differences, rather than musical ones, though. Would you say the increased headroom in the Turbo added to the enjoyment of the music - in other words, was the groove wear a distraction, or irrelevant to the enjoyment of the music and only really noticeable in 'analytical listening' mode? Which would you buy, having heard both, if they cost the same?

@Sue Pertwee-Tyr The Turbo version is extremely forgiving of worn/ rubbish sounding records , which l believe is down to the very full and a very smooth top end- The Turbo is an absolute fantastic phono stage which punches way above it's weight.

If people would stick to my own nomenclature there shouldn't be an issue! Arkless 640P refers to the version I've been making for several years now and which uses "normal" technology and can cater for both MM and MC carts.

Arkless GTI refers to the version with transimpedance circuitry (current input) and which is MC only due to this technique.

"Turbo" added to either of the above means further enhancements, bigger/better capacitors, improved op amps where applicable and a few other tricks. Actual topology remains the same but it could be thought of as the "deluxe" or "S.E" version. "Arkless Turbo" is meaningless then without the 640P or GTI part and the unit "Tarzan" has is the 640P Turbo and quite different to the one being discussed above.

As headroom is being bandied about well actually the active version has considerably greater headroom but both have way more than necessary.

 

[foxwelljsly]

Oh, and I stand corrected on the active/passive op amps.

 

[foxwelljsly]

I've had a couple of messages asking if there was any difference in gain between the GTi and the full fat GTi Turbo. There is not.

 

[Arkless Electronics]

To reiterate... with a transimpedance unit such as this the gain is not fixed but is set by the cartridge itself. In effect the resistance of the cart itself IS one of the gain setting resistors. The lower the carts internal resistance (NOT the manufacturers suggested load resistance) the higher the gain. There is a tendency for lower output carts to have lower resistance due to fewer turns and for it to then, conveniently, increase its gain to compensate BUT it must be said there are so many "flyers" from the trend of lower output = lower internal resistance as to make the link verging on tenuous... More powerful magnets or smaller gap twixt magnet and coil etc can even reverse it in some cases!
The upshot of this is that the vol on your pre amp could be anywhere from say 2 - 6 for the same volume depending on the cart being used. It's the nature of current input phono stages.

 

[foxwelljsly]

To reiterate... with a transimpedance unit such as this the gain is not fixed but is set by the cartridge itself. In effect the resistance of the cart itself IS one of the gain setting resistors. The lower the carts internal resistance (NOT the manufacturers suggested load resistance) the higher the gain. There is a tendency for lower output carts to have lower resistance due to fewer turns and for it to then, conveniently, increase its gain to compensate BUT it must be said there are so many "flyers" from the trend of lower output = lower internal resistance as to make the link verging on tenuous... More powerful magnets or smaller gap twixt magnet and coil etc can even reverse it in some cases!
The upshot of this is that the vol on your pre amp could be anywhere from say 2 - 6 for the same volume depending on the cart being used. It's the nature of current input phono stages.

The output with a AT33 PTG II is almost identical to my Cyrus DAC X. Which is both convenient and pleasing.

 

[Arkless Electronics]

The output with a AT33 PTG II is almost identical to my Cyrus DAC X. Which is both convenient and pleasing.

0.3mV output and 10R internal resistance in this case according to the specs.

With my Technics EPC-300MC it's 0.1mV and IIRC 15R so output is maybe half of CD player but with my Ortofon MC15 Super it's 0.5mV and 5R IIRC and output is maybe half as much again as CD player.

 

[Markyb]

Had heaps of gain with my ESCO rebuilt Linn Troika

 

[Sue Pertwee-Tyr]

Received my eBay purchased 640P today. As described, well packed, prompt delivery by Royal Mail. The same seller has another on sale at the moment, it's a hospice down in the Home Counties. Buy with confidence

 

[Markyb]

I prefer the P651 with the on off at the front but already had a P640 in storage.

 

[Arkless Electronics]

Had heaps of gain with my ESCO rebuilt Linn Troika

Yep Troika's will give loads of output from it! Prob 2.5 - 3V or so.

 

[Arkless Electronics]

I prefer the P651 with the on off at the front but already had a P640 in storage.

IN a PM correspondence recently with a fishie we discussed the possibility that the comparative rarity and high prices recently for these could just be that they really are getting thin on the ground and the reason being that, especially with the 640P without its on/off switch, that they were nearly all killed by being left switched on and as they were cheap to buy back then (£68 IIRC) people just binned them! Such a pity if true as a recap would have brought them back to as new!

 

[Arkless Electronics]

As I am getting lots of PM's asking when I'll be taking more in for conversion I'll say here what I've been saying in the replies, which is that I will announce in this thread when I'm ready to take some more in.
It will then probably be in small batches, 2 or 3 at a time so I can control how much of my time these take up rather better... I'm obviously having to fit these in around repairs, vintage rebuilds etc and they've been taking over a bit much lately.

 

[djftw]

As I mentioned previously I ended up with an extra 640P, link to the auction I won. Anyone want to match the £92.60 with RMSD I paid I will happily send it on! Though I will require a contract stating you agree I get my conversion before you, I will not require you sign in blood

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=174342260581

 

[Vinny]

Other than picking up on the general enthusiasm for the GTI, I have avoided detailed investigations into posted opinions, so hopefully unbiased comments as follows, maybe to be tweaked as I am still listening.....

Maybe I approached this differently – I listened with the Arkless stage for several hours to get an appreciation of what it is, to get the sound embedded, and then back-tracked……

Some personal comments on the Arkless GTI itself.

The Arkless stage, in my system, is sublime at mids and highs – vocals, especially female, guitars, strings and piano are there, absolutely spot on. Which suits me better than fine as they are what really, really float my boat.

Bass? Well, bass is not in short supply, and it is very musical, but can I guess what was producing it for the recording? It has definition, it is no way muddy, but at the same time it is indistinct, imprecise, veiled. That includes drums.

Comparisons………………………………

I used a Mitchell Iso/Hera for almost countless years and first compared it against a P75. I really could not tell one from the other, especially after making the Iso loading resistor selectable, as in the P75.

So, against the Iso? Very, very similar although either the Iso has slightly better, clearer highs or muddier mid’s – I think the latter, but aural memory for small differences over even small time periods defeats me, mostly. I also did not faff with the loading in the Iso. Sound-stage may be slightly better/more convincing on the Iso. Better bass definition/clarity from the Iso. I prefer the GTI.

I have used just four SUT’s and all but one beat the Iso, by a (very) long way, in all respects. After trying a PureSound, I was not likely to go back to a stage (although I will skip anything but mention of the German silver SUT “matched” to Lyra cart’s). The one here at the moment is a Rothwell MC1.

Comparison – playing via the SUT, it has a contribution from a MM stage of course, but it is brighter, crisper, more defined, more detailed in the mids and highs, so not so laid back as the GTI. I prefer vocals on the GTI. Bass has more definition. Amazing sound-stage with the Rothwell.

I can see exactly why anyone might prefer the GTI over the MC1 as the GTI is most definitely a warmer, less clinical sound. You pays yer money………………….and if you have no MM stage already…..

Also compared to a John Curl-designed circuit, head amp’. Nothing comes close. ‘Nough said.

It is a fantastic stage compared to the couple of lauded stages that I have heard. Want to get more from your TT than the GTI stage offers – investigate SUTs and head amp’s, if you have a MM stage or would buy .

There you go, just my ten penneth.

System – Plinnked LP12, FXR, Delos, Croft push-pull Micro with MM stage, NCC300 mono’s, 15 inch Tannoy DC.

Like I said - still listening, so this post may be tweaked.

 

[Arkless Electronics]

Interesting review though I strongly disagree with Vinny over the whole headamps and SUT's into MM stages thing. There is nothing "special" about such a combination and although it can give superb results it is not intrinsically better than other methods.... and I make headamps and valve MM stages! I have a full function valve hybrid two box pre amp under construction ATM for a customer who already has one of my head amps in fact!
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!

 

[Vinny]

Interesting review though I strongly disagree with Vinny over the whole headamps and SUT's into MM stages thing

Apologies to all if it reads that way, unintended. Perhaps better put that £ for £, you MAY, perhaps should, find it easier to get a significant change in sound, perhaps to any one person's particular taste, by looking outside of phono stages, simply because of what is generally/widely available. There are LOTS of MC and MM stages, quite a few MC SUTs and almost no head amp's by comparison.

it should be borne in mind that the McKinie head amp and tweaked croft pre together are a prob £2K

Both the Croft and head amp' are as originally sold, so the Croft is old(ish - 20+ years??). S/h, together, they cost me a lot of beer/wine less than £700, but point taken. New, if they were available, Lord alone knows - probably quite a (hell of a) lot more than £2K.

That said - the Iso/Hera cost me??? £250????? (more???), 30 years ago and is worth about that now.