EL86 in triode mode, ~600R internal resistance.
But.. how much Idc your transofmer can withstand if you're intending SE operation?
How much gain do you need?
This transformer results in approximately, 2:1 ratio, I wouldn't expect more than a voltage gain of 4, depending of how you are loading your transformer.
How much primary inductance do you have?
But.. how much Idc your transofmer can withstand if you're intending SE operation?
How much gain do you need?
This transformer results in approximately, 2:1 ratio, I wouldn't expect more than a voltage gain of 4, depending of how you are loading your transformer.
How much primary inductance do you have?
It's low, is it a toroid?
Some years ago I develop 12B4a preamp with Noguchi 5k OPT (exspensive game!) for my friend.
This is the simulation.
The gain approx. 2, the real bandwith (-3dB) 10Hz-65kHz.
Attachments
Your step down ratio is 4:1.
If you want a gain of 4, you need with mu = ~16.. no DHT with low RP will get you there. If you see 12B4A loaded with 5k, ok.. and so you have parallel sections loaded with 2.5k = same plate load impedance.
What is it that you dont like about what you have?. You say that you want to build a tube pre amp using these transformers but you already have a tube pre amp using these transformers.
If you need a voltage gain of 4, you need a mu 20 something tube. I would try parallel 5687... that will give voltage gain of 4 in grounded cathode configuration and also Rp will be ~1k... which is well, marginal for 2.5k load.. but there you go, parallel the 2k Rp type again if you like but it seems the tube that you have already is better suited. Yes.
With 60mA gap, I would try using the primary of the transformer as a plate load, and capacitor couple to the next stage = try 2A3 as the voltage amp, this will give gain of about what you are looking for, an output impedance of, well.. low enough for most things, and would utilize the core properly with a full 60mA current. 250 across the tube, -45 bias... 2k5 load = standard RCA text book 2A3
LH/S
Last edited:
Hi Ludwig, I just want to try the sound of a preamp with OPT. Beside, I wish a little bit stronger amp than 12B4A PSE.
My plan is to use the preamp with my Audio Note EL34PP clone and/or my LM3886 power amp. So low gain is ok.
@Euro21: I guess apply parallel 12B4A into your schema is my best choice to me this time. Will try it when I back from my biz trip next 2 weeks.
Thank you.
My plan is to use the preamp with my Audio Note EL34PP clone and/or my LM3886 power amp. So low gain is ok.
@Euro21: I guess apply parallel 12B4A into your schema is my best choice to me this time. Will try it when I back from my biz trip next 2 weeks.
Thank you.
Hi Bitinhvi, my mistake, I was thinking the 12B4 PSE was actually your pre-amp.. now I see what you mean. I agree with Euro 21, just use the same tubes and transformer as pre amp with the 600R secondary connection output.
5687 or ECC99 with both sections in parallel will also work, more output voltage but less low frequency due to twice the drive impedance (1k vs 500R), and you already have the 12B4..
LH/S
yea I don't know where he gets it because two sections of ecc99 tied directly in parallel is almost Identical to a 12b4.
How about triode connected 6AG7 (= russian 6P9 ) ?
http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6P9.pdf
mu = 23
gm = 13,3 mA/V
Pa = 9 W max.
Prices at Ebay some 1.5...2 USD/pc.
http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6P9.pdf
mu = 23
gm = 13,3 mA/V
Pa = 9 W max.
Prices at Ebay some 1.5...2 USD/pc.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.