It looks like you're new here. If you want to get involved, click one of these buttons!
Subscribe to our Patreon, and get image uploads with no ads on the site!
On going through some boxes, I found a 12AT7 / ECC81. It's branded Sylvania on the box, and marked as made in USA on the box and on the valve. Looks unused.
If I were to stick this in my Blues Deluxe RI, what effect would it have in which valve position? Would I need to change any of the circuit elements around the valve?
The amp's used at home only, low volume, no attenuator.
Nomad
Nobody loves me but my mother... and she could be jivin' too...
Base theme by DesignModo & ported to Powered by Vanilla by Chris Ireland, modified by the "theFB" team.
Comments
I myself have one in my FBD and I prefer it to the stock 12AX7 tube.
Nomad
Nobody loves me but my mother... and she could be jivin' too...
Which, unless I'm missing something, would mean that the output valves don't get driven as hard, which would amount to no real difference in a home-use amp that's nowhere near driving the output valves anyway. I guess that would mean the volume controls would have to go up a bit more to get to the same volume, which is potentially a plus.
So, no 'opening up of the tone'? No 'sounds like a Twin'? No snorting pixie dust off of corks?
Nomad
Nobody loves me but my mother... and she could be jivin' too...
V2 - not very useful in my opinion, but won't do any harm to try it. Lower gain, but a 'thinner' sound.
V3 (phase inverter) - clearer, more 'open' tone, slightly more bottom-end depth.
Personally, I prefer it in V3, a 12AY7 in V1, and a 12AX7 in V2.
There shouldn't be any issue with surrounding components, although it will load the plate resistors a little more heavily - it's not impossible that one could fail earlier than it would otherwise, but it's rare. Fender did have a batch problem with the PI plate resistors in these and early Hotrod amps, but I haven't seen a dead one for some time now.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
The Deville had more problems with this, and higher voltages (made worse by the 230 / 240 V wiring issue yawn..........).
Fender now use a higher rated resistor.
I've found 12AT7s to be prone to microphony in V1.
This is exactly how I've set up my Blues Jr. Sounds great.
Whatever it was, they've fixed it now anyway - something Fender have been pretty good at with this series, unlike many other companies who seem to just rip up a design and start again, rather than fixing it.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Sounds like V3 is the way to go (can't think of a reason to reduce the preamp gain, or make the sound thinner).
Regarding the anode resistors on the PI, the amp is from 2013, and my 2004 schematic shows them as 0.5W. Don't know if they have been upgraded since the schematic.
Am I right in thinking that they need to dissipate about 0.25W with a 12AX7, and more like 1W with a 12AT7? Do they dissipate this/whatever all the time (ie, not signal dependent)?
Nomad
Nobody loves me but my mother... and she could be jivin' too...
No, 0.025W (and 0.9W for the 12AT7). Does it really change that much?
Nomad
Nobody loves me but my mother... and she could be jivin' too...