[ShortBtwnHdset]

Hey Gang!

In answer to all who may be wondering, no, I haven't burnt the house down!!! The project has been on standby, as I've been busy both in town and out.

Honestly, I was also a little bit intimidated. When I did the last mod, my soldering skills must have been better, or I don't know what changed, but I keep coming up with cold solder joints, indicating the solder is just not flowing well. The soldering iron is a nice Hakko digital station, along with a standalone Weller wand 60 watt (new), so I don't think it's those. I haven't changed the solder from what I used last time. But heat just doesn't seem to be flowing into the solder joints. I've had to redo nearly every connection, and had to use crap tons of flux (leaves a real mess). Fitting everything has been a bitch as well , these V-caps are a good deal larger than the film caps they replaced.

Anyway, finally installed the last of the caps, I'll need to get out the manifying glass and closely reinspect the entire board before I reassemble everything. Oh, and the case fit will be tight, may have to install a washer under each bottom plate screw to improve the clearance on a few connections. Still have to enlarge cutout's and add one on the bottom plate.

A couple of pics included for any curious. Y'all have a great night!!!

 

[gumisb]

If you want to improve tube filament heating circuit before final closure the chassis there is way to do that by increasing capacity of two 1000uF/25V capacitors near power switch. Voltage for heaters are controlled by two voltage regulators LF60A with fixed voltage of 6V and according to data sheet up to 0.5A with limit of 1A. Jason Stoddard is clever guy and decide to use high PSRR for low frequency of this regulator to control also maximum current by limiting capacity of input caps. With ripples ca. 1.8 V current limit is ca.400mA. With increased capacity on input we get smaller ripples more room for voltage regulator. As usual there is no free lunch. On power on when tubes are cold and resistance is quite low heater circuit will go with 1A so for 300mA tubes current will be over 3 times higher which could shorten tube life.

 

[ShortBtwnHdset]

Hey Gumisb! Thanks for the input, I've pretty much decided that's it for the scope of this mod. Whether I ever do a stage 3 is undetermined right now. Also, I've experienced tube 'flash' already on some RFT tubes, pretty sure that's shortening their life as well, don't want to make that happen any more than it already does. Might reconsider in future if I can figure a way to add a soft start to it.

 

[gumisb]

You have full picture, you decide. According to some research lowering tube heater voltage from specified 6.3 V to 6V as we have extends tubes life about 50% so I have no problem to short a little bit that period

 

[ShortBtwnHdset]

Hey All! Finally finished it up, got it put back together, and playing music! Now I've got a few hundred hours burn in needed for the V-caps, but it already sounds better than it did when it first powered up. My experience has been that the electrolytics are quick to burn in.

It will be a while before I'll be able to tell whether mod was worth it. About to take out the stock tubes and run the solid state tubes for burn in.

Pics included, look how far the V-caps stick out of the case!!! Will be getting bushings and another bottom to mount on bottom of the other for shock protection. For now, I'm happy it's working!

 

[ShortBtwnHdset]

So, burned in the motherboard overnight w/solid state tubes. I've got to say, the difference in heat between the solid state tubes and the actual 6DJ8's was suprising to me. Amp releatively cool to the touch with the solid state, run's VERY warm with the tubes even in a short time. Maybe even a little over what it was, which makes me wonder. I'll need to watch that closely, may even need to pipe an ammeter in to see if I'm drawing more juice than I should on the tube heaters. Plan on getting home after work and continuing burn in with generic tubes, but amp is off right now, just don't want to leave that running without some presence in case something were to go wrong. Most likely fuse would blow, but you never know, Drummer Boy posted here that his smoked and was routing power thru the volume control (volume knob was too hot to touch).

External PS mod for the heater rail might be a better idea than I originally thought. So, I will likely have to post this question elsewhwere, but if a transformer secondary ends up not being used, does that up voltages on the other secondaries??? Or does Shiit have some sort of compensation in the Mjolnir or solid state tube circuit for when SS tubes are run? Or, is the higher voltages on the other secondaries within tolerances for nominal operations? Hmmm....

Anyway, thought I would add this. Ya'll have a great day!

 

[gumisb]

There is no problem to run amp without heating connected. Regulators for tubes heating are marked in circles. If you remove them you have perfect spot to connect GND(big pad) and+ from external regulator by for example banana socket mounted on back of the chassis . It could be even simple universal bench power supply with regulated amperage and voltage. after this regulator originally is only 1000uF cap bypassed by small ceramic near each tube.

 

[ShortBtwnHdset]

Hey Gumisb! That's the heater regulator? I had assumed that had to do with the balanced pre outputs because of location on board. Dang, those v-caps are wasted, if that's the case.

Edit: Man, I wish Schiit would furnish a schematic on this. I'm all for the 'Right to repair' movement. I understand Jason's reluctance, given the hazards involved with amatuer Techs working on gear and proprietary nature of the design, but this is a model that was taken off market. It sure would help to have a roadmap.

 

[gumisb]

Those are components of tubes heating. Two caps close to regulators seems to be "dirty" symmetric power supply mentioned somewhere in this thread (not part of heating circuit)

 

[ShortBtwnHdset]

Wow, thanks for that, Gumisb!

So, the other 1000 uF caps surrounding tubes are not part of that heater circuit? Just goes to show, working 'blind' really ain't beneficial! So it looks like two of the v-caps ( the largest cut-outs, of course) were un-necessary. Those electrolytics could have easily been bypassed with cheap WIMA MKS-4 caps, at a much smaller size and hugely lower price. Sigh..... Those were hard to do, and expensive. Most of this also falls on me not confirming voltages before modding. Problem is, there is no easy way to do this, as the bottom plate is the heat-sink for mosfets. They'd burn up without it. There are insulators under each (and insulating collars), so I imagine the mosfets can't be grounded, or at least tied together. I guess I could have gotten small seperate HS's for each, just to allow run-up and confirmation of voltages at specific points. Now that mods are done, the voltages at these points should be easy to confirm, but not so before mod. Crap! Well, this was and is all an experiment. What I've done previously has improved the sound, and I think this mod will as well. Could it have been done cheaper, yes. Could it have been done less invasively, yes. But I didn't know that coming in to it, and as far as I've seen, no one has done a similar mod.

Well, anyway, that does make an external supply much more feasable. For any contemplating modding their Mjolnir, hopefully you can learn from my mistakes. I'm not a technician, definitely not an engineer, just a hack with the desire and some basic skills..

 

[ShortBtwnHdset]

So, a quick update. Mod has about 24 Hrs of burn in on it, the caps seem to be breaking in nicely. I don't think this mod will take nearly as many hours to normalize as the last. Many people scoff at the idea of cap burn in times, especially some of the Cap manufacturers recomendations for burn in hours. I myself fully believe it, especially with higher voltage caps and copper foil caps in particular. This collection of caps seems to need a lot less. That makes sense, as these were rated at much lower voltages than the last round. The Mundorf replacements (stage 1 mod) were 1000V. The V-caps on this mod are rated at 250V, the Wima's and electrolytics much lower.

Temps have come down as well, case temp is where it was before, very warm after 30 min or more of operation. Initially, the sound was pretty harsh, grainy, congested, and spiky/peaky. At this point, the sound is maybe a bit overly punchy with the Verite's, leading edges are overly snappy, but not by a lot. This is similar to what I experienced after the last mod, it's almost as if the caps over control directly after install, and burn in allows them to loosen up and let the music flow. Midrange was especially constricted at first power up, and that has already loosened by a large degree. Male vocals are already good, and female vocals are gaining, they seem to be at the same place I was before the mod.m There is also more inner detail, but not by a lot. As I've said before, my hearing loss from working on aircraft engines, as well as age, has rolled off my hearing pretty sharply past approx 11 KHz, but I do seem to be hearing a small bump in percieved treble. My Verite's sound good un-EQ'ed, a first for me. I'll revisit my impressions later when I have more hours on them, but I am likeing what I'm hearing. Oh, and all these impressions were gained using the stock, many many hours on them, original 6DJ8 tubes, so I'm hoping tube rolling will be even more beneficial.

On a seperate note, having problems with Amazon Music on my laptop. Laptop's hooked to a e-GPU, USB from there is going into Gungnir DAC. Whenever I run Amazon Music I get a small crackling sound when my mouse pointer crosses any graphics transition. If pointer left parked in a non transition space in window, no crackling. And it only happens with Amazon music, if I stream from Youtube/Crunchyroll/Netflix it doesnt crop up. Currently using laptop while I'm rebuilding my home desktop, so problem will likely be solved with a fresh format, but I've been searching for a solution onlineover the last several days with no success. Weird.

Hope Ya'll have a great day!!!

 

[ShortBtwnHdset]

Hi All!

Tubes are still burning in, somewhwere around the 60-75 hr mark, so that's good. Unfortunatley, had a few disaster's happen Friday, and may no longer be qualified to evaluate stage 2 mods. I'm kinda pissed about it, too.

I mentioned I was having problems with Amazon music. Well, after getting my desktop computer back together with a new SSD and a new installation of Windows, installed Amazon Music, but was having strange volume issues. Wasn't thinking about it, had my headphones on, volume was acting really wierd, looked on taskbar and two instances of Amazon were running, seemingly fighting each other. Suddenly one instance dropped, and volume went to half or more on the dial, peircing loud. Yup, just took out some highs from my hearing. Crap!!!!

To make matters worse, 11:30 that same night the fire alarm went off in our condos, and it's peircing loud as well. So, I've listened to headphones since, I'm definitely hearing less treble than I was, and what I was hearing was limited. Arrrg!!! Have since uninstalled and reinstalling Amazon, fixed that issue, for what it's worth.

Anyway's taking a break for a week or so, let my ears heal. Damage is done, but right now my ears are overly sensitive and need time. Will reevaluate later.

Ya'll have a good night!

 

[ShortBtwnHdset]

Hey, Everyone! Well, it's been a little more than a week, slowly working headphone listening back into my days. I started back mid last week listening at maybe a third the volume I used to (or lower), couldn't listen for over a song or two without sensitivity, at this point I'm around a little less than half where I used to listen at, decible wise. Still not listening for long, maybe a few songs and some gaming/vid streaming. I have lost some highs, cymbals have lost some shimmer and triangles are more recesssed, but not as bad as I had initially thought. Still going to take it very slowly, I'll try not to get to a listening fatigue point.

I had several tubes sets on order before all this happened, and they are beginning to trickle in, wish I had held off, but that's water under the bridge. Currently listening to a pair of GE 6201 5 stars, Train's 'Drops of Jupiter' sounds good! Strange, though, the heaters seem to glow a little brighter than all the others I've tried. Anyway, Ya'll have agreat night!

 

[ShortBtwnHdset]

Hi All! So, my volume tolerance is finally getting back to normal, and I'm sooo glad!!! Most of my upper treble is back, though some shimmer is missing.

The 2nd stage mod is settling in very nicely, detail retrieval is markedly better, so much so that I'm not even regretting the extra money and the set backs. It's just unreal the gains this 2nd mod has enabled, easily as much as the first. And it may be that some of what I'm hearing is further refinements openiing up the first mods strengths.

First, instruments leading and trailing edges are much better defined, making melody line very destinct. Santana's "Shaman" album is a prime example. Santana 's lead will often have quick little flurries of notes in a riff, often at the end of a lead phrase. They tended to blur together before the mod, but now are articulated clearly. Instrument body has solidified more, both with singers, acoustic instruments, and drum strikes, sometimes uncannily so! Stacy Kent's 'Raconte-Moi' album is incredible, the way her voice and the Piano/Bass/Guitar/and Highhat fill the space, erie!!! I could listen to her sing french to me all day. And the noise floor must have dropped some more, I was listening to some Robert Palmer hits, off of "Sneakin Sally thru the Alley/Riptide/Double Fun/& Heavy Nova, and hidden melody lines on low level/background instruments became clear. What was once musical fuzz gained definition.

I still think these caps are loosening up, or at least that's my hope. I would say I maybe have a hundred or so hours on them, lost 2 weeks where I maybe listened for 4 or so hours in total while my ears were healing. Tonight's the first night that I've seriously listened since. All this is still on the GE tubes, I'm about to power off and tube roll with something special.

As to the tubes on order, Christmas shipping must be causing delays. Both orders are from other countries, I've got 7 prs coming from DBtubes and 2 sets of Siemens from the Netherlands. I'm also liking these GE's enough I'll order a few pairs of them.

Hope Ya'll have a great night! Merry Christmas, and happy listening!

 

[bcowen]

I still think these caps are loosening up, or at least that's my hope. I would say I maybe have a hundred or so hours on them, lost 2 weeks where I maybe listened for 4 or so hours in total while my ears were healing. Tonight's the first night that I've seriously listened since. All this is still on the GE tubes, I'm about to power off and tube roll with something special.

As to the tubes on order, Christmas shipping must be causing delays. Both orders are from other countries, I've got 7 prs coming from DBtubes and 2 sets of Siemens from the Netherlands. I'm also liking these GE's enough I'll order a few pairs of them.

Which would be virtually any other tube.

(sorry, couldn't help myself)