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

chartz said:
Looking forward to the DIY version of your amp.
Or did I miss the said thread?
A modern 303 is a nice perspective indeed, I can’t wait to build one ;)
Will it suit the old ESL’s?
Click to expand...

Ah you're talking about the power amp... No DIY version I'm afraid. It was completed and has been giving great results in my system for a few months now. It is a pair of class A 16W monoblocks but can readily be reconfigured for higher power or class A/B use.
The only real similarities to the 303 are that it has a capacitor at the output and single ended/unbalanced gain stages.
It should work great with ESL57's.
It was designed very much with an eye on producing them for sale, in as much as a major part of the project was to create a user proof unit of great reliability (I've always been very wary of selling power amps as it is all too easy for users to abuse the unit, by short circuiting it or by wiring it to 4 sets of speakers for a party etc etc, and blow it up and then claim "it just stopped working" and demand a repair under guarantee). I wouldn't hold your breath waiting for it though!
 
Hi Jez
Is the GTi Turbo loaner still doing the rounds?
If it is I would like to try it.

I have an Aqvox 2ci (current input) phono stage at present, so a comparison with that might be useful, though I am interested in making a purchase.
My cartridge is a VDH ONE Special, 0.75mV output and 9 ohm impedance so plenty of current available, maybe to much for your unit??
That's mounted on an original Mission 774 arm, which I know you like, on my recently completed Lenco Idler drive TT as pictured.
Lenco_4_09.jpg


Van Den Hul "the Grail" is out of my reach, so I'm interested in what the GTi Turbo has to offer.
 
Qwin said:
Hi Jez
Is the GTi Turbo loaner still doing the rounds?
If it is I would like to try it.

I have an Aqvox 2ci (current input) phono stage at present, so a comparison with that might be useful, though I am interested in making a purchase.
My cartridge is a VDH ONE Special, 0.75mV output and 9 ohm impedance so plenty of current available, maybe to much for your unit??
That's mounted on an original Mission 774 arm, which I know you like, on my recently completed Lenco Idler drive TT as pictured.
Lenco_4_09.jpg


Van Den Hul "the Grail" is out of my reach, so I'm interested in what the GTi Turbo has to offer.
Click to expand...

I'm not currently (or voltagely:D) making any I'm afraid so whilst I could send the demo unit out again it seems pointless to me as if potential orders came in from hearing the demo unit I couldn't give any indication of when I could build them. I will be making more though.
I seem to vaguely recall that a past customer upgraded to my GTi Turbo from a Van Den Hull The Grail as it happens...
 
Ok, I'll keep an eye on this thread for future builds.
Meanwhile I will source a donor unit, would you believe that 5 months ago I sold a virtually unused 640p I purchased from new, that had sat in my cupboard for over 5 years. Doh!
 
Qwin said:
Hi Jez
Is the GTi Turbo loaner still doing the rounds?
If it is I would like to try it.

I have an Aqvox 2ci (current input) phono stage at present, so a comparison with that might be useful, though I am interested in making a purchase.
My cartridge is a VDH ONE Special, 0.75mV output and 9 ohm impedance so plenty of current available, maybe to much for your unit??
That's mounted on an original Mission 774 arm, which I know you like, on my recently completed Lenco Idler drive TT as pictured.
Lenco_4_09.jpg


Van Den Hul "the Grail" is out of my reach, so I'm interested in what the GTi Turbo has to offer.
Click to expand...
Just an FYI, with only the one anti-skating weight pushed all the way in on the Mission there will be insufficient bias compensation. The centre of the weight need be 12mm from the centre of the AS pulley pivot for 1g. 1.5g sees the weight at 28mm out centre to centre.
 
Qwin said:
Ok, I'll keep an eye on this thread for future builds.
Meanwhile I will source a donor unit, would you believe that 5 months ago I sold a virtually unused 640p I purchased from new, that had sat in my cupboard for over 5 years. Doh!
Click to expand...
I’ve got one you can have for postage and donation to pfm as someone tried to upgrade the opamps and is knackered the tracks on the board but psu is ok.
 
Craig B said:
Just an FYI, with only the one anti-skating weight pushed all the way in on the Mission there will be insufficient bias compensation. The centre of the weight need be 12mm from the centre of the AS pulley pivot for 1g. 1.5g sees the weight at 28mm out centre to centre.
Click to expand...

The anti skate bias required for the VDH ONE special is very low at 0.4 to 0.6 gram.
Even with the counter weight pushed all the way in, like I have it, it will be more than 0.6 grams, but that's as close as I can get without modifying the weight itself.
It seems to run very quite like I have it and no miss tracking.
 
Qwin said:
The anti skate bias required for the VDH ONE special is very low at 0.4 to 0.6 gram.
Even with the counter weight pushed all the way in, like I have it, it will be more than 0.6 grams, but that's as close as I can get without modifying the weight itself.
It seems to run very quite like I have it and no miss tracking.
Click to expand...
Interesting.

Even more interesting is your Mission (Original) 774 Tonearm project page. I installed ('assembled' might be a better word) a lot of these back in my retail days. Had both a 775S and an SM, the latter with the offset locking chuck arm mount, too. Wish I'd kept the tonearm.
 
Yes, when researching the arm, I was finding bits of information here and there, many conflicting bits of info and some that were just wrong.
So I decided to bring what ever information I could find and confirm, together in one place on my web pages.
This should be a good resource for other users, or prospective users, of the original 774.
 
It's heavy, made from three layers of Bamboo worktop, so 120mm thick in total.
The platter assembly weighs 5.5Kg.
The feet are heavy duty tilt and swivel adjustable feet, adjustable from above, down the holes that have stainless finishing rings.
The feet are rated at 100Kg.
I don't want to hi jack this thread, so anyone interested in my deck/arm builds can find the details here: https://www.jkwynn.co.uk//Lenco/Lenco_Thumbs.html
It's also on Lenco Heaven under PTP6 builds.
 
Qwin said:
Yes, when researching the arm, I was finding bits of information here and there, many conflicting bits of info and some that were just wrong.
So I decided to bring what ever information I could find and confirm, together in one place on my web pages.
This should be a good resource for other users, or prospective users, of the original 774.
Click to expand...
Very helpful, thanks.
 
Just a quick thread resurrection with some comments that might be of interest to fellow Arkless GTI users. I remember, back in the day, Jez commenting that the regular CA wall-wart would be fine and didn’t need upgrading. It’s only a 12v transformer.

Anyway, a friend who builds stonkingly good valve amps, and I were having a listening session, comparing the Arkless GTI to his, highly modified Cairn Boost. We decided that, good though the Arkless definitely was, the Cairn had more of the boogie factor. (He’s an LP12 user). He pointed the finger of suspicion at the ferrite ring on the power lead. As it happens, I also have an Arkless Turbo, but only the one wall-wart (which isn’t an issue as I only use one phono stage at a time); I decided to get a second wall wart, and chose one with a higher power rating (1250 mA, 15VA) just for a bit of headroom. About a tenner, from Amazon, so no biggie if nothing happened. Aside from the higher current capability, it also turned out not to have a ferrite ring on the output, though this wasn’t something I noticed when I ordered it. Driving the GTI, this was miles better - it now more than held its own against the Cairn on fun factor, and was well ahead on other aspects of performance.

Encouraged by this, my friend offered to make me up a dedicated transformer box, using a top quality 12v EI transformer from the suppliers who make his amps’ output transformers. This one is very stiff, with barely any measurable sag under load. He also used shielded cable on the output side. Suffice to say, this has further elevated performance to the next level. Tighter timing, bass is tauter and better defined, timbres are richer, and there’s more space around and between the instruments. It’s a jazz lover’s dream and I’m blown away.

Thought I’d share this in case any other GTI users fancy experimenting with higher spec transformers.
 
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