Hum, a few questions...

[paulw]

Completed my Smash last week and have a few questions,



the first being, should the 25w 1K wirewound resistor get very hot - hot enough not to want to keep your finger on it for more than a few seconds?
The other is the best strategy for reducing the inherent level of hum being produced, to me it sounds like 50hz mains borne hum and doesn't change with volume settings.  From reading through the other threads, I've place some 10db attenuators on the inputs of my Paramours (MkII's) and this has reduced it to acceptable levels (horn speakers with over 100db/w @1mtr sensitivity) but I am still aware that it's there with CD (between tracks and very quite sections) but it's covered by surface noise when playing LP's.  Never had hum issues to this level with any other pre's I've used and would prefer to reduce it without the need for attenuators if possible.

Just to add all resistance and voltage test readings were pretty much spot on.

Paul

 

[Doc B]

Yes, some parts in tube gear definitely get too hot to touch. I suggest not touching them as you might be burned by a hot tube or transistor. The Smashup upgrade will reduce the preamp's noise floor for best performance with super sensitive speakers and improve the dynamic headroom.

 

[paulw]

Thanks for the prompt response - only went looking under the hood (after switching off) as the Smash was smelling a bit hot, the only thing I found to be very hot (apart from the valves obviously) was this resistor, so just thought I'd ask!

Guess I'll have to put up with the inherent noise as I don't really want to upgrade this unit from it's base spec - well apart from new volume and balance pots.  Just ordered some switchable attenuators with 10/15/20db settings

Paul

 

[paulw]

So now a month has passed since I started using my Smash and to be honest I'm finding it a bit problematic, to reduce the level of inherent noise in my system I need to use -14db attenuators, but this means to get a meaningful SPLs for orchestral & rock I have to get the volume control up to 3/4's the way round.  Above half way, the upper mid-band has a relentless edginess to it, which I believe is basically the onset of distortion by the time I'm 3/4's it definitely sounds a bit distorted.  The build is stock (though I always use stainless steel hardware and my preferred on/off switch) except I've used Alps volume and Audionote balance pots, all voltage and resistance measurements were virtually spot on & well within tolerance.

Paul

 

[Doc B]

If you have not yet installed it the Smashup upgrade will increase the headroom noticeably.

 

[paulw]

If you have not yet installed it the Smashup upgrade will increase the headroom noticeably.

I was hoping not to go for the upgrade, but looks as though I might have to too make the Smash more viable - is there a 6SN7 supplied with the kit as this isn't a valve I have in my stash?

With past kits (Seduction & Quickie) I've added the available upgrades and in both instances, whilst they deliver what they are supposed to (certainly better detail) this was, I felt at the cost of the 'musicality' that I liked so much when originally built.  When I decided to rebuild my Quickie I left out the PJCCS and felt this was overall preferable, again in the context of my system.

Guess I'll be placing an order for the Smash-up shortly  :-\

Paul

 

[fullheadofnothing]

If a kit requires a tube, the tube is supplied.

 

[paulw]

If a kit requires a tube, the tube is supplied.

Thanks, order placed.

Paul

 

[paulw]

So the Smash-up is on order and I didn't think I had any 6SN7's & I always like to have spares, but in my miscellaneous Russian box I have some 6N8S's and on the boxes I've written 6SN7.  Anyone have any experience of these?

The invoice from the Russian shop shows the price as $1.25 each, but that was quite a few years ago.  Just checked with one of the people I usually deal with and they've shot up in price to $2.50, $6.00 or $60 now depending on being Novosibirsk, FOTON or MELZ (metal base) manufactured respectively.  ;D mine are a mix of Novosibirsk & FOTON.

Paul

 

[mcandmar]

I've used the metalbase Melz 6N8S, the cheap ones not the uber pricey ones, and found them very clean and detailed sounding vs a US made RCA or Sylvania 6SN7.  But as these are being used for shunt regulator duty in the Smash i doubt it will make any difference which you use, just pick a pretty one

 

[paulw]

Thanks M, more concerned about any reliability/performance issues than anything else, not really into the tube rolling thing anymore (lifes to short) just need to satisfy my OCD need to always have spare parts for consumables
Paul

 

[paulw]

Well today I had the chance to try out the Smash with a few other bits of kit and I have to say it performed admirably, indeed seemingly better than with my Bottlehead Paramours amps, into my 7Pi Corner Horns!  It was particularly nice with a Luxkit (Z504) 200w class AB amp driving a pair of 86db/w/mtr Harbeth HL5's where the combination provided both power and subtlety with a whole range of musical genres.  The Z504 has a variable sensitivity input so matching was a breeze and it also work very well with my old Quad 405-2 driving the Harbeths, but needed quite a bit of attenuation.





Smash-up(grade) is on order, so hopefully when fitted it'll provide some better results in the context of my own system, but certainly as it stands, I've gone back to using my Quickie 'clone' as at the moment it seems to provide a better overall match! 

Paul

 

[mcandmar]

Reliability will not be a problem with 6SN7's.  I would pickup a spare set of 4P1L as i have had a couple go noisy and had to replace them, but they are so cheap its not worth worrying about.

I am sure the smashup will make a considerable difference as the 4P1L is a really great tube.  I use a shunt regulated 4P1L preamp to drive a Firstwatt F4 clone for my main speaker setup and it sounds wonderful. I do have a dilemma as i am currently building a 6A3 based amp that is giving it a serious run for its money, it might end up being my main rig after all.

I am also a big fan of the quickie, my modified quickie headphone amp is my second favorite headphone rig, punches well above its weight.