We'll assume you're triode wiring the D3A. There are ample 5K:5K interstage transformers that will work nicely with a D3A. The necessity of using one is a little questionable to me.
You need to SWING volts, and DRIVE that 300b grid to get a nice sound.
You might try the modest EC86 with a mosfet follower though and skip the IT. 😉
You might try the modest EC86 with a mosfet follower though and skip the IT. 😉
I like the D3A both with and without IT. (Hybrid mu follower)
5K:5K is ideal at around 15mA/180Vplate with D3A in triode connection.
Use a good transformer! If you need good bass response primary L => 40H @ 15mA - 20mA
5K:5K is ideal at around 15mA/180Vplate with D3A in triode connection.
Use a good transformer! If you need good bass response primary L => 40H @ 15mA - 20mA
The conection in the D3a is triode mode.
The Interestage Transformer is a Lundahl LL1671 , could be 1:1 or 1:2.
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Hi kevinkr, the IT is a Lundahl 1671 and OPT is a Lundahl 1664.
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Not enough gain/headroom in this application, you need the full swing at the D3A plate to drive the 300B properly. The 1671 is a good choice 1:1.
In some instances it is a great option and gets you lower driving impedance.
The 1:2 conection is not a good option ?
We miss Popilin. I could ask him everything, and he always had a good answer.
You should use 1:1, this gives you the lowest source impedance and plenty of drive voltage and headroom.
2:1 step down would push the D3A into grid current and it may clip. Half the swing at the plate is available at the 300B grid.
1:2 step up would result in about 5K reflected to the 300B grid which is workable, but not something I would normally consider.
2:1 step down would push the D3A into grid current and it may clip. Half the swing at the plate is available at the 300B grid.
1:2 step up would result in about 5K reflected to the 300B grid which is workable, but not something I would normally consider.
Right Kevin. D3a has a MU~33 (or so) in triode mode with anode and cathode resistors.
So I would either change this driver tube (with IT) or avoid IT.
So I would either change this driver tube (with IT) or avoid IT.
RajkoM, the D3a is enough , i had 2 amplifiers con D3a triode mode, RC coupling , and very good 7.5W.
Yeah, this is part of my question regarding why you would want the IT in the first place.
The other issue is the max operating anode voltage, which is 220V for a D3A. If we assume you have about 450V of B+, you'll need to drop about half of it to use the IT. This is voltage drop that would otherwise be quite useful with a resistive plate load.
Reading this topic for first time. I build a 300b, with d3a and anode chokes (1667).
Didn't read everything but attached how it is implemented.
Didn't read everything but attached how it is implemented.