[carlman14]

I think what I'd rather do is simply break the connection from the 45 grid to ground and make a connection to the input tube plate using the time delay switch. So, a 100K resistor to ground from the grid on warmup, then the switch fires, breaks the connection to the 100K resistor and makes the connection to the input tube plate.

Could you use a PSU B+ time delay like you do in your other direct-coupled builds like airmid, rather than this switch between the two tubes?

 

[L0rdGwyn]

Could you use a PSU B+ time delay like you do in your other direct-coupled builds like airmid, rather than this switch between the two tubes?

Maybe, I'll probably choose a sacrificial 45 (not a globe) to test out both ways, put a 1ohm current sense resistor in series with the B+ supply and see which way results in the lower transient current spike on startup. A delayed B+ would certainly be easier to implement, heck I could probably repurpose the Airmid power supply PCB. If necessary, could even do a time delay on both, say 30 seconds for the B+ and 1 min for the coupling switch. Definitely going to be one to play around with.

 

[UntilThen]

Many of the used ones were pretty used up from being in TV sets.

I sold all of mine, I liked the Tung Sols and the RCA's the best...I kept a few sets of RCA....just in case I wanted them down the road.

I'm glad I kept most of mine and they tested 101% Finally going to listen to them in a transformer coupled amp.

 

[jgwtriode]

Any thoughts on why tubes go microphonic after a few months of use. I noticed one of my National Union 6J5GT's started going microphonic a few months ago. Now it has become quite the little transducer. Even light tapping anywhere in the vicinity of it produces a not so lovely singing response in that channel. It still sounds fine and I have Herbie's tube Dampers on it, but you can hear the ever so slight occasional ring when nothing is playing. There is also a very subtly higher noise floor that does seem to vary a bit. It's very low level, but the other tube is quite dead and completely quiet comparatively. I have ordered another matched pair, since it does drive me mildly nuts. My GEC L63's are fine but just not tonally quite as pleasantly sweet!

Happy listening,

jgwtriode

 

[L0rdGwyn]

Any thoughts on why tubes go microphonic after a few months of use. I noticed one of my National Union 6J5GT's started going microphonic a few months ago. Now it has become quite the little transducer. Even light tapping anywhere in the vicinity of it produces a not so lovely singing response in that channel. It still sounds fine and I have Herbie's tube Dampers on it, but you can hear the ever so slight occasional ring when nothing is playing. There is also a very subtly higher noise floor that does seem to vary a bit. It's very low level, but the other tube is quite dead and completely quiet comparatively. I have ordered another matched pair, since it does drive me mildly nuts. My GEC L63's are fine but just not tonally quite as pleasantly sweet!

Happy listening,

jgwtriode

As far as what causes it, it's just the mechanical vibration of the internals of the tube. Nothing that you can really do to avoid it, just luck of the draw. Can be minimized by isolating the amplifier and using tube dampers.

 

[L0rdGwyn]

I'm going to a Head-Fi meet in Pittsburgh on June 10, gonna bring Aegis, my PCM63 DAC, and the Caldera. Should be fun, had my OTL, PCM56 DAC, and Atrium / VC there last time, gonna switch it up.

Might be building Zach another amp this year too, starting to think about what that might look like. 300B is on the table.

 

[bcowen]

Might be building Zach another amp this year too, starting to think about what that might look like. 300B is on the table.

I was sleepily having my first cup of coffee this morning until this. Now I'm fully awake.

 

[L0rdGwyn]

I was sleepily having my first cup of coffee this morning until this. Now I'm fully awake.

Lol well happy to have helped get your day underway. It's still under discussion but probably that is the move. Likely I would do something similar to his 45 amp, meaning a two stage transformer coupled fixed bias design, voltage regulated B+ and bias supplies. The transformer manufacturer situation is always changing nowadays, I am thinking Monolith Magnetics for everything since they are the only one stop shop around now. We need a pair of filament transformers, mains transformer with B+ and bias supply windings, and a pair of interstage transformers and custom 300B headphone output transformers.

 

[jgwtriode]

Monolith Magnetics Summit Nano X looks very interesting. Nano magnetic amorphous cores. And only one output xfrmr designed for WE300B. Priced accordingly as well.

The NanoX product range is envisaged for anyone seeking the ultimate degree of sonic purity. This range makes use of the same design philosophy by using mathematical modelling but it also uses even more refined winding schemes, substantial nanocrystalline metal cores, insulation materials like virginal PTFE (Teflon, Dupont ™) reducing distributed capacitance, special winding/insulation techniques (Varilay) which result in absolute sonic purity and unseen specifications. A typical 300B product is designed around a full power bandwidth of a stunning 20 Hz. The other frequency extreme is reached far above 100 kHz.

Nanocrystalline materials start their life as an amorphous ribbon and are heat treated to form crystals at the nanoscale (10 nm to be precise). These cores exhibit very high permeability, very low hysteresis levels up to high frequencies, resulting in a pristine sound experience.

These transformers represent the pinnacle in transformer design. For the moment, this product range features only one product: the S-9/NanoX is released as a tribute to the glorious WE300B tube. The range will be expanded in the future toward higher power tubes such as 211, 845 as well as GM-70.

Impressive,

jgwtriode

 

[L0rdGwyn]

Wow, Aegis is done! Obviously I can't stay idle for long, already thinking about the next thing...

Feels like a long time since I designed a SET for some reason...but really it hasn't. I'm going to start drafting Zach's 300B amp. He likes the 5687 I used in his 45 amp, so probably going that route again, I like them too. I'm basically going to use the same underlying circuit, but will be using different signal transformers and some different signal path circuitry. And of course, 300B outputs.

This will be a lot easier the second time around, I already know the circuit so I don't have to prototype it, I can just build it. Also, since I'm planning on Monolith Magnetics, I don't have to try and work with off the shelf components, I can just order exactly what I need, easy. Zach is going to send me some 300B tubes to play with.

Since the 300B is in vogue, I have to go all out and make this a special amp.

 

[L0rdGwyn]

I also emailed Dave Slagle to see if there is an updated timeline on my transformers for my HY69 amplifier. I'll probably work on both of these at once. LCR phono stage will have to wait. I'm looking forward to having that done, but NOT looking forward to building it lol I learned the hard way that phono stages are a real pain, especially when it comes to measuring them given that pesky RIAA curve.

 

[L0rdGwyn]

Oh Dave is winding my transformers now, perfect

 

[leftside]

I also emailed Dave Slagle to see if there is an updated timeline on my transformers for my HY69 amplifier. I'll probably work on both of these at once. LCR phono stage will have to wait. I'm looking forward to having that done, but NOT looking forward to building it lol I learned the hard way that phono stages are a real pain, especially when it comes to measuring them given that pesky RIAA curve.

Should be well worth the effort. My Grange/LCR phono from Mick at Supratek is glorious. I'm finding a new found love for vinyl again.

 

[L0rdGwyn]

Should be well worth the effort. My Grange/LCR phono from Mick at Supratek is glorious. I'm finding a new found love for vinyl again.

Yeah it will be, just going to be a lot of work. But it's the end game of phonos, it should be the last. I've been preparing for this one for a long time lol been collecting D3a and E55L. They are just tricky to measure accurately since you have to somehow work the RIAA curve into your measurement rig. I was dissatisfied with my measurements setup on the last go around, so will have to rework that for this build.

 

[jgwtriode]

Trying to get back to some reasonable routine! I have been out of it for a number of weeks. Just to cut to the chase I have been diagnosed with Papillary Renal Cell Carcinoma and am currently being treated for it I do have good doctors, including a wholistic MD. Doing targeted immuno therapy. An IV once a month and a crazy expensive Oral. I am managing and friends family and church are all very encouraging. Don't have much energy at nights to listen any more, but occassionaly. Obviously Audio has been put on hold and the copays accumulate. Have had to use up most of my PTO at work and am balancing hours and appointments as best I can. Not so bad that I have stopped working or am considering taking disability.

I was able to get another set of National Union 6J5GT's a couple weeks back. One of my other set got quite microphonic, still sound great but slightly higher noise and occasional resonance in one channel a hint more noticeable. Burned the new set in and this set is sounding better, bit more dynamic, with a hint more weight and drive in
the botton end and overall just a touch more detail and clarity. That was a pleasant surprise! Feeling a bit better tonight, doing some listening!

Hope to manage this and get it under control over the next few months. I do have a go fund me, that my nutritionist set up. Costs are exorbitant and I have switched to a much more expensive organic keto diet to help deal with things nutritionally. https://gofund.me/b7fbecfa

Anyway miss having the energy to more readily keep up with all the excitement. But it always a thrill to come back and see what LOrdGwyn is up to and to hear the latest news from everyone here.

Thanks for your support, prayer and wishes and the amazing vibe that come from this group,

James