[ginger]

Andy,
The Ns and NXs come with dissimilar lead lengths. Connect short lead of one to long lead of the other and vice-versa. Go to Parts Connexion and look at Blackgate Technical Report No 74.

I started trying Blackgates on the weekend on my 55N - Now running 100uF/50V Blackgate Standard for C10 and C12, Blackgate Standard 100uF/50V paralleled by 1uF PPS for C3 and a Blackgate FK 100uF/16V for C7.

I thought that C3 gave the amp "testicles" and "C7" gave the amp "refinement and good manners". C10 and C12 gave the amp power and improve noise performance.

Each change to a Blackgate also significantly improved background noise levels.

I had some 47uF/63V Hitano's across the main power supply filter caps - I ditched these, with Blackgates elsewhere I could hear the noise contribution from them.

I have ordered Balckgate N 100uF/50V to try for C3 and Blackgate NX 22uF/6.3V for C7 (have also ordered some 470uF/6.3V NX's to try at C7 since I think its value is a bit low).

This is results to date and the "Plan" for next round of tests/mods

Cheers,
Ginger

[andyr]

I have also removed two sets of RCA sockets, by soldering flying lead interconnects directly to the circuit board for "cd in" and "pre out". We can hear an improvement.

Malcolm, could U "pleeze explain" what exactly you mean by this?  Did you insert some other RCA sockets into the back of your case, with fly leads, in place of the Hugh-supplied, PCB-attached socket blocks?

Or do you mean you did away with RCAs for "cd-in" and "pre out" and hard-wired these ICs to the PCB?

Thanks,

Andy

[Malcolm Fear]

>>Or do you mean you did away with RCAs for "cd-in" and "pre out" and hard-wired these ICs to the PCB?

Yes, that is what I did.

I did get rid of the supplied RCA sockets. I couldn't drill the back panel accurately enough.

Regarding RIAA resistors. I bought some close tolerance caps from Welbourne. I thought that while I was buying from them, I would get their swihest resistors. I have not experimented in this area.

[andyr]

Ginger,

Could you please be a bit more explicit about a couple of posts you've made ... non EE people like me need reference to an explicit "Cx/Rx" on the circuit schematic, not just the description "330nF coupling cap".  Plus there are a couple of other things.  So:

1.  You said "Parallel a 4700pF Polypropylene cap across the 470nF input cap (which I believe is C1).
Q1a: What is so important about a polyprop cap here ... as elsewhere you've said "polystyrene"?  RS Components sell them in 10-packs, so it would be nice if one 10-pack could be used for all of the 4700pf bypasses.
Q1b: Where can I buy these?  RS Components has Arcotronics "High AC voltage" polyprop caps but these sound like they're the wrong cap type!

Alternatively, I could use RelCap RTs which are polystyrene.

2.  What no. cap is "the Electrolytic feeding the diff amp stage"?

3.  Under the heading "Other Parallels" you said "Polyprop 330nF Coupling cap with 1500pF polystyrene cap".  Trouble is, there are no 330nF caps in the parts list of my GK-1 ... so which cap did you mean here?

4.  Which no. cap is the "Output Valve Cathode Bypass"?  Is this C4?

5.  Finally, in an email to me you said you were going to "Tie the 0v (signal ground) on the Switch (or Relay) pcb to chassis locally, by means of a 100R res with a ceramic 10nF cap across it."

"The right point to attach this 'earth' is the place where the signal 0v sides attach on the leads across to the Analog pcb Solid State Buffer Inputs."

Sorry but could you explicitly identify - by means of a component number - just where the pcb end of the res & cap should attach to.

Thanks, Ian.

regards,

Andy

[ginger]

Andy,
Polypropylene caps are NOT quite as good as polystyrene. I used what I had in my component bins at home. Either are fine. We are talking the 5th or 6th decimal place in the distortion figures. Polystyrene are generally harder to find. The high voltage Polypropylenes are physically quite large and will NOT be suitable (I buy them for my valve amps). The low voltage polypropylene from manufacturers like WIMA are the go.

The critical caps to parallel are the caps in the signal chain. I don't have the schematic with me at the moment  - will edit this with component numbers on Monday after the Weekend.

Cheers,
Ginger

*** Edit 8th Dec
Caps in the signal chain to parallel are:
C1 (470nF) parallel with 4n7 polypropylene
C19 (10nF) parallel with 100pF polystyrene or polypropylene
C21 (470nF) parallel with 4n7 polystyrene or polypropylene rated at 250V or greater
Other mods from my GK-1
C7,C6,C4,C11,C12 all 68uF/20V OSCON
Additional 68uF/20V OSCON directly across LED L1 (for improved top end)
C10,C12 100uF/50V Blackgate Standards
C2 22uF/6.3V Blackgate NX

[andyr]

Ginger, Mal & other GK-1 addicts ... here's a couple of interesting tweaks I read about elsewhere - the second one, in one of the other Circles:

1.  Cryo-treat your tubes.  I am in the process of finding out where I can get this done and will post when I track it down.

2.  Put a "rope caulk" cap (like a yarmulke!) on the tubes!  (In the US you can buy stuff called "Mortite".)  An alternative would be modelling clay (here known variously as Play-doh, Plast-i-Clay, Roma Plastina or Plasticene) and can be found in some kids/toy stores and art supply houses.

You may find the sound to be more, or possibly less, than your current liking ... but they absolutely change things.  Everything gets tighter (bass, focus), but you lose some holographic 'air' in exchange.  It's so cheap it's worth it ... and it's fully reversible.

Whaddya reckon, guys??

Regards,

Andy

[PSP]

Has anyone tried a really good cap (I'm considering 0.022uf V-Caps at $35 each... RTX are $5.95 each at Michael Percy) for the C-19 coupling cap in the GK-1?

Many Thanks,
Peter

[jules]

Peter,

nice work reviving the Valhalla thread, there's a lot of great development info in it. For those who might be interested there's also a Valhallah thread [initiated by the late Malcom Fear] for the 55, though I can't remember it's exact title.

More recently this thread had some discussion about GK-1 components http://www.audiocircle.com/index.php?topic=22740&start=0&postdays=0&postorder=asc&highlight=
I think stvnharr has used a .01uF RTX at C19 ......

jules

[ctviggen]

I'd be interested in hearing about the V-caps.  I was thinking of using these my crossovers (only a few of them -- you'd go broke using more than that).

[stvnharr]

Peter,

I think stvnharr has used a .01uF RTX at C19 ......

jules

Yes, I used a .01uf RTX at C19 and it seems to work just fine.
I may also use one at C22 as I have a couple spares.
Also thinking of RTX for the Auricap.  Any of the teflon caps are all a bit pricey, even the cheapest of the lot.

[PSP]

I should have spent some more time reading before posting on C19.  Looking at page 5 of this thread, Hugh posted:  

C19 was different. Here there is about 45V across the cap, and thus the constraints are relaxed. However, this location calls for a very small capacitor, because the input impedance of the tube is very high, more than 1M. Knowing my dielectric theory, I opted for an industrial polystyrene, hard to source, but very, very good sonically. The cap need only be 10nF, with maximum size not exceeding 100nF, but polystyrene is probably the best dielectric shy of silver mica so it was our first choice, and remains so.

So, we want a small cap (I suppose to avoid noise pickup into the high impedance tube circuit) between 10 - 100nf.  A V-Cap is definitely not "small".  I suppose the C19 options are:

1.  leave it alone
2.  try bypassing with a 10-20pf silver mica
3.  10-22nf RTX.[/list:u]  I'll let you know what I find out.

Peter

[andyr]

I suppose the C19 options are:

3.  10-22nf RTX

I'll let you know what I find out. Peter

Peter, I used a 10nF/400v RTX here.

Regards,

Andy

[stvnharr]

 I used a 10nF/400v RTX here.

Regards,

Andy

Andy,
Did you use 1uf RTX at C21?

Steve

[andyr]

 I used a 10nF/400v RTX here.

Regards,

Andy

Andy,
Did you use 1uf RTX at C21?

Steve

Hi Steve,

Yez I certainly did!!     Only the /100v one, though, as this is pretty sizeable anyway!  

Regards,

Andy