Yep true, 5AR4 has heater 5V 2A, same as my transformer spec.
Good you noticed, now I see realize that my intended replacement EZ81 has 6.3V 1A, I read somewhere that heater voltage for rectifiers has wide range, so I wonder if it will still work well, or maybe give me higher voltage drop etc?
I wouldn't run the EZ81 from 5V in this application. It will be current limited and might even be damaged if the space charge is depleted in operation.
If you have a 5V winding, use a 5V tube. For a 6N6P amp you can even use a 5Y3 - or save money and power and use a pair of Si diodes 😀 You're already going to use CCS, right?
If you have a 5V winding, use a 5V tube. For a 6N6P amp you can even use a 5Y3 - or save money and power and use a pair of Si diodes 😀 You're already going to use CCS, right?
Ok then I will get myself more 5AR4, since I am somewhat voltage restricted with my transformers and want low drop, but like to use a tube for the slow start and glow..
Creative choice of chassis for your flea amp 🙂
I have built before an OTL 6N1P/6N6P combination long time ago for a friend, a basic low cost amp, but it sounded very good I remember, it was used for STAX electrostatic headphones.
Edit: I made it for ECC99 in the output first, but when the tubes wore out some years later I gave him 6N6p as substitution and those lasted much longer..
Attachments
Last edited:
Thanks.
Ya the cake pan idea came from trying to make the amp as cheap as possible. 4$ for a chassis is pretty good. The entire amp cost under 100$. I used toroidal power transformers as the outputs as a proof of concept - they were 10$ each. The most expensive single part was the 12V 10A brick that powers it. It was about 30$.
It now uses 6P15P (or 6P18P, I can't remember) strapped as triodes in a quest to lower the cost by another 10$.
Nice design BTW. I use the same tubes in OTL for dynamic headphones with a different topology.
Instead of a tube diode for that "glow", I use a VR tube as a negative shunt regulator for the bias voltage 🙂 The 0B3 I'm using now glows a nice purple colour.
Ya the cake pan idea came from trying to make the amp as cheap as possible. 4$ for a chassis is pretty good. The entire amp cost under 100$. I used toroidal power transformers as the outputs as a proof of concept - they were 10$ each. The most expensive single part was the 12V 10A brick that powers it. It was about 30$.
It now uses 6P15P (or 6P18P, I can't remember) strapped as triodes in a quest to lower the cost by another 10$.
Nice design BTW. I use the same tubes in OTL for dynamic headphones with a different topology.
Instead of a tube diode for that "glow", I use a VR tube as a negative shunt regulator for the bias voltage 🙂 The 0B3 I'm using now glows a nice purple colour.
Attachments
A 10w 70v matching transformer can do 30 watts or more at higher frequencies, start the rolloff at 300hz.
I use LL1676. 1:4 and 2:1+1 measure great but needs loading otherwise square wave rings very badly and you can hear it. 1:1+1 is all over the place as a phase splitter.
1:4 didn't sound very good to me but 2:1+1 sounded brilliant. Lynn Olson confirmed the measurements also good and bad.
Look at K&K Audio thread for the 2:1+1 connections described as 1:1.
1:4 didn't sound very good to me but 2:1+1 sounded brilliant. Lynn Olson confirmed the measurements also good and bad.
Look at K&K Audio thread for the 2:1+1 connections described as 1:1.