The BA-3 as preamp build guide

Jump to Latest
A

aradan

Member
Joined 2015
Russellc said:
If you look at 6L6's build steps, you will see that is the one he used. I used it in both of my BA3 preamps. It off - on -on. It was meant for a tube pre so that you could switch on the filaments only, then hit it again for the B+. I suppose maybe both on - on positions could be combined to give a higher rating, I find mine works fine as is.

Russellc
Click to expand...

HI Russell,

Thank you.

I think it should work with a soft start board as the voltage of the switch would be lower if it is used

Sent from my ONE A2003 using Tapatalk
 
R

Russellc

Member
Joined 2003
Paid Member
Hikari1 said:
I think it's the output impedance. I believe the BA3 FE is around 300R output impedance. Most headphone amps designed for low-R headphones have an output impedance of sub 30R. Sometimes even less than 1 ohm.
Click to expand...

I thought that in the F6 thread, it was said the output of BA3 was over 1000R, they were concerned with mating it to F6 input impedance? I have to say, it mates fine to mine!

Russellc
 
H

Hikari1

Member
Joined 2012
Considering it's meant to drive an F4 sans buffers (Burning Amp output stage), it would certainly drive the F6 w/buffers.

I was more interested in the output impedance with regards to driving headphones. I've seen some comments that the BA-3 makes a great headphone amp...but I haven't had that experience. With 32 ohm, very sensitive Grados the BA-3 lacks drive and requires 3/4 of the volume knob to get a good volume level. A 20-30db gain headamp with 45mA of bias should blast a pair of Grados off my head. Problem is the output impedance is so high (for a headphone amp) that it can't drive my 32R Grados and somehow the signal is swamped. Might work better with higher ohm headphones but it still is not ideal, I think.

I am speculating here, but the output impedance is probably one of the tradeoffs that occurs with this no feedback design. One could make a preamp with a similar topology (F5-like) with feedback and bring the output impedance down. Not that the BA-3 output impedance is really that high...in fact, it's fine for a preamp. Just not good for a headphone amp.
 
brianco

brianco

Member
Joined 2005
Thanks for that ZM.

I found - after edit time closed - a few remarks by Juma to virtually the same question. The questioner found that the sound was not very good, thin and similar to a cheap commercial Preamp. Perhaps I will have to find the correct Toshiba devices.

[Any ideas on a line pre for these Hitachis? I once had an ASR pre which used them and which would drive my old Impulse horns without a power amp!!]
 
marc brown

marc brown

Member
Joined 2007
I was trying to get a handle on the gain as I'm trying to decide where to put my attenuator in the signal chain. It could go after source selection or after the gain stage, depending on the overall gain. It's an LDR-based attenuator called the Clone Note and could handle 10db but not 30.
 
You must log in or register to reply here.
Top Bottom