Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Seduction => Topic started by: Doc B. on September 25, 2012, 09:29:04 AM

Title: Seduction transformer mounting
Post by: Doc B. on September 25, 2012, 09:29:04 AM
I have mentioned before that the Seduction is the oldest of our current production kits. There have been quite a few minor changes over the years, most of which are documented in the current version of the assembly manual. Some capacitors and resistors you get with your kit will look different than those in the manual, but they are actually better quality. The biggest change that is not documented in the current manual is that the power transformer no longer mounts on the nylon standoffs. Instead of standoffs you now get some black fiber washers to fit over the mounting holes and a couple of extra screws. So you can mount that power tranny right to the underside of the chassis and be happy.
Title: Re: Seduction transformer mounting
Post by: Modmad on February 19, 2013, 05:56:12 PM
I received mine with the trans ready to fall off - and it did in my hands when I wiggled it - in a *factory*, not buyer, *built* non-kit w/C4S - that I traded a couple of my old demo cables for. The phono stage sounds very nice and nicer now with quickie upgrades I immediately made to it (more coming as the caps not in stock get here) but the trans mounting, stock, is mechanically bound for trouble leverage vs the tiny shoulder standoff isolators wise, and was deep in it as it arrived. The trans was klunking around, loose! I don't just repair stuff like this, I mod stuff - making things *better* is my way. I fixed the mechanical disadvantage problem - weight/leverage of the trans vs the tiny shoulder isolators by isolating the trans vibrationally at the same time. That top plate has a microphonicity problem anyway (understatement!). Did it with simple leftover Sorbo strips from my junk parts bins the width of the trans base, under, and the mounting ears size, over. And thread-locked the mounting screw/bolts w/removable lacquer (not in the pics - later step) - something that should have been done at the factory or by any kit builder in the first place! Those nuts will always work loose during any transit without this in stock form and with the certain-to-be mechanically troublesome arrangement I received it with. Have pictures of the mod, two of them attached to show the trans mounting upgrade.
Also vibe damped the underside of the top plate (not visible in attached pics). Not enough help, still too microphonic. Will be adding a constrained layer arrangement on top when I find a nice looking piece of black acrylic I want for that. Had to fix this up, quick. Traded for this because my phono stage just died, to add to the other two on my repair list and Harry Weisfeld (VPI) is coming here soon. Hate fixing, am into upgrading and trying new stuff. Didn't want to have to use my Krell phono section, modded or not, or others I have still working. Those are too sterile sounding.

Title: If you are using tube shields, remove the spring in side them.
Post by: VoltSecond on February 19, 2013, 06:22:24 PM
If you are using tube shields, remove the spring in side them.  You still get the shielding and it cuts the microphonics. (  How I mechanically isolated the transformer in the Foreplay.
Title: Re: Seduction transformer mounting
Post by: Doc B. on February 19, 2013, 08:02:14 PM
Gosh I feel so inadequate now.
Title: Re: Seduction transformer mounting
Post by: Paul Birkeland on February 19, 2013, 08:30:28 PM
\That top plate has a microphonicity problem anyway (understatement!).

I could have sworn that tubes are microphonic, not sheets of metal.

The twisted pair of black ground wires does not look factory built, by the way.
Title: Re: Seduction transformer mounting
Post by: caffeinator on February 19, 2013, 08:56:03 PM
Wasn't Microphonicity the fifth album released by The Police?
Title: Re: Seduction transformer mounting
Post by: Paul Birkeland on February 19, 2013, 09:18:21 PM (
Title: Re: Seduction transformer mounting
Post by: Grainger49 on February 20, 2013, 01:35:46 AM

I bought a Seduction the day they came out, kit of course.  Soon after the release on the old board there were posts about pulling the springs inside the tube shields.  That information didn't migrate here.  But I find it odd, I have had my Seduction longer than most people and never had a problem with microphonics.  Give the Russian military surplus 6Н23П (6N23P, Pin 9 is shield) tubes a try.  The 6Н23П-EV is a select version with tighter tolerances.  I have been using them for many years.  They are more rugged than others and therefore less susceptible to microphany.

As I said, I have an original Seduction and it hasn't been shipped but in all those years, about 12 I think, the transformer has never gotten loose. 
Title: Re: Seduction transformer mounting
Post by: matthewmckay on February 20, 2013, 05:13:58 AM
I cannot recommend the mapleshade tube crowns enough for use with the seduction... the difference they made in my setup was not subtle, and if I had had a chance to demo them before pulling the trigger, I probably would have shelled out more for it.   

Title: Re: Seduction transformer mounting
Post by: Modmad on February 20, 2013, 08:45:38 AM
Thanks, folks.

1. The springs came out the moment I saw them, before I even gave the Seduction its first listen. I'm an old pro, this was obvious for both microphonicity and why would you want an unnecessary piece of steel there, either?

2.  Of course the top plate isn't what's microphonic - it's a resonator - but the tubes are mounted onto it, aren't they? No, now don't tell me it's the socket that is, not the tube. You must have a lot of time on your hands, Blackplate, and a Jesuit education for getting into dithering the details. Tapping on the top plate with a pen is like banging a drum on mine, and indicative of lower level effects affecting the noise floor badly in a delayed, distorted feedback loop from the speakers, and other environmental noise (my seduction is sitting on an airtube isolator for the latter).

3. The trans has no reason to get loose if the unit isn't being transported/moved around much...I did mention's the movement that will shake the trans around and then the mentioned mechanical disadvantage will loosen the screws. However, even if you don't take the Seduction anywhere (careful not to let 'er feel neglected...), there's still the fact that all transformers cannot help but generate some amount of vibration - and it's mounted onto that same top plate. Vibration isolating it is still a good idea and my fix addresses both issues.

4. I tube rolled 5 sets of tubes immediately after burn-in and settled on a set of 6922 JAN/Sylvanias for the *sound quality*, the most important thing for me. Your goals may vary. I'll fix the microphonicity if I have to to get the sound I want rather than compromise on that by using a tube that is less susceptible. A Russian pair was among the testees, and there's a fabulous but expensive Red Tip pair of 6DJ8's coming to me on a trade soon that will be an alternate - it's smoother and more alluring (borrowed briefly for the listen), but a bit less quick and detailed than the fit mood.

5. I make my own "Tube Crowns" (not one of my products, I only make them for myself - not a profitable item handmade, see the attached pic of my completely rebuilt 60's Mac 240 mid amp in my triamped/active XO setup) from lead bars + ERS lining, foil outer cosmetic). Have compared them to the Mapleshade product (very nice, recommendable for those who cannot make something like this) and mine are rather noticeably superior. But I haven't made any yet for the Seduction, and would not use them alone, anyway, on a *phono stage*. I would have to add a shielding "veil" of some neat shielding material - I have a few types from a copper/nickel sputtered mesh to something that looks like your wife's "sheer" curtains, to a stainless/copper/unspecified proprietary something or other amalgam weave to work with in my stocks (sorry, proprietary sources - I do this for a living). This would make a nice see-through  (for the "glow") shielding veil but I have only so much time on my hands to build this so it will have to wait while I try to pay the rent.

6. No need to feel inadequate, Doc. It is much easier to snipe the fixes than to do the orginal design, and I see lots of clever turns of layout I admire in this design. Joppa (IIRC) did a nice job here. Besides, every product that is to be profitably self-sustaining has to be built to a price point. Leaving room for guys buying the design to have some fun making their own changes and improvements is part of the game. Gotta leave room for those in hobbies. My congratulations meant, not criticism!

Title: Re: Seduction transformer mounting
Post by: Modmad on February 20, 2013, 09:13:24 AM
P.S. - Took a look at your grommet fix, Voltsec. Yes, that will work for isolation, but not as good for securing the trans against the mechanical problem, or vibration isolation. I considered doing it that way for less work, but the way I settled on only took a few extra minutes and is more effective as the Sorbo is more effective an absorber than the harder rubber of the grommets, which cannot give the wider-stanced support of strips the width of the trans base, either. I always go for as many concurrent gains as possible out of each move.

No problem in my case with the trans grounding - I just moved the existing star-washered ground lug to the right place in contact with the trans mounting "ear". You could have added one like that yourself (+ washer to protect the grommet) - much easier than trying to solder to steel! The sharp teeth of the starring cut into the steel and make the contact for you.

Title: Re: Seduction transformer mounting
Post by: Doc B. on February 20, 2013, 09:43:19 AM
I guess I should explain that I was being sarcastic. Your initial post was pretty superior in its tone, and I thought that was rather obnoxious. But I try to be more diplomatic than to say so, in the hopes that the guy will get it. I do appreciate your clarification here, and I'm cool.
Title: Re: Seduction transformer mounting
Post by: saildoctor on February 20, 2013, 11:38:37 AM
I've got my seduction PT-1 mounted on the screw on nylon standoffs that came with the kit - zero microphonics the way my system is set up.