Better pot
As the use of an Alps Blue velvet was considered a few posts above - here is a far better alternative:
SMT Resistor Step Attenuator 100K Volume Control | eBay
In comparison to a Slage Autoformer both were head to head in clarity.
Blue Velvet pot muddies your signal.
As the use of an Alps Blue velvet was considered a few posts above - here is a far better alternative:
SMT Resistor Step Attenuator 100K Volume Control | eBay
In comparison to a Slage Autoformer both were head to head in clarity.
Blue Velvet pot muddies your signal.
Hi Andy,
I would like to follow your recent schematic (with 126C plate load) for building 26 preamp and I have CX380 on hand.
Would you mind to share the current PSU schematic with me.
Can I use 100H 10ma choke for alternative of 126C ?
Beside, how to get the value of 14.5R 30w resistor.
Thank you
I would like to follow your recent schematic (with 126C plate load) for building 26 preamp and I have CX380 on hand.
Would you mind to share the current PSU schematic with me.
Can I use 100H 10ma choke for alternative of 126C ?
Beside, how to get the value of 14.5R 30w resistor.
Thank you
I haven't quite finalised the 2 x 126C option, still experimenting. I'm a little down in the treble right now so need to try different wirings and topologies. 100H at 10mA is a good start, and 200H probably better as long as the DCR isn't silly. For cathode resistors go for wire wound vitreous enamel or Russian ex-military. I leave you to work out the PSU - plenty of choices, as long as the capacitors are polypropylene like motor run etc. I like choke input filament supplies - Hammond are fine, and you'll want a 1.5amp or more.
OK - I haven't tried those. In my experience polypropylenes beat cooking grade electrolytics every time, but who knows what exotic parts can do. Thanks for that.
Alright, I have an EE question. I hooked up the both primary coils of my Hammond 369JX to 120V in parallel, and on the secondaries I put a multimeter on the 250-0-250v coil and left the 5V coil open. When I added power, I blew the fuse in my IEC inlet. Why is this, did i make a wiring mistake?
Hi Andy,
Thank you for your recommendation.
I will try to order a Power transformer 290v-250v-0 and 100H 10ma choke from China. it may a good start for my project.
For cathode resistors, I still have no idea to get a better one for 30w.
Thank you for your recommendation.
I will try to order a Power transformer 290v-250v-0 and 100H 10ma choke from China. it may a good start for my project.
For cathode resistors, I still have no idea to get a better one for 30w.
Attachments
I've tried starved filaments (850mA) vs. (almost) non-starved (990mA) on my 26 preamp and to me it's quite obvious that non-starved sounds better. Fuller, rounder, more focused and 3-dimentional midrange. Is this something others have experienced or is it just related to a lower plate resistance and my use of transformers?
I have few dozens of #26 tubes, mostly globe ones.
None of them has -listenable- microphony (am I lucky?), but they are more or less sensitive of radiated noise (hum, radio stations, cellular phones etc.).
These tubes are in great-great-grandfather's age, so it's internal stucture - especially heater/cathode - is "open", therefore unprotected against electro smog.
None of them has -listenable- microphony (am I lucky?), but they are more or less sensitive of radiated noise (hum, radio stations, cellular phones etc.).
These tubes are in great-great-grandfather's age, so it's internal stucture - especially heater/cathode - is "open", therefore unprotected against electro smog.
ok...but still these tubes were used well into the 40's with plenty of RF in the air! something else is going on.....
