The B1 is great, what an amazing buffer but what about having it offer some gain of its own?
What mods can I do to get some gain out of it?
What mods can I do to get some gain out of it?
Any reason why you want to do this rather than build any one of the hundreds of gain stages published on this forum over the years?
It's a source follower / common drain topology - current gain only. You'd need something with a fundamentally different topology, a common source, to have both voltage and current gain. The H2 circuit and kit is common source.
A voltage buffer has no voltage gain. If buffer and gain are desired, then a gain stage needs to be added
@billshurv Do you have any suggestions out of the "hundreds" that could be found? I sold most of my tube preamps when I moved recently and have found my B1 can't drive my Aleph J properly.
The ACP+ used as a preamp has 9dB of gain, and a nice full "tubey" midrange.
How much more gain do you think you need? the B1 can be unnerving at first as a normal 10dB gain preamp means you listen with the volume around 9PM. Without that gain you are cranking the pot around to 3AM and in your mind you feel you are missing something, but that may not be the case. the aleph spec says 1.5V in for 25W out so if you are using a CD player or DAC as source you should be fine. If you are using a phono stage you might need 6dB more.
Iron Pre is a great solution from all I have heard. But I have not been able to get one!!
But I recently made a B1 version with an op-amp gain stage up front. The op amp and resistors are socketed so you can change the gain, change the input impedance, roll the op amp or bypass the whole gain front end if you want. I use a 100k input Z and w/10k pot, 12db Gain and LM4562.
I know many in the Pass group will not like using an op-amp. But.... it sounds great and the drive stage remains a B1.
Besides, how man 5532s do you think were in the production audio chain of pretty much every piece of music you listen too?
Anyway, if you want the KiCad schematics I'd be happy to share them with or without PS on the same board.
Please forgive this shameless plug of my own creation. I know it's not an Iron Pre but it is small, cheap, flexible and sounds great IMHO.
Cheers.
But I recently made a B1 version with an op-amp gain stage up front. The op amp and resistors are socketed so you can change the gain, change the input impedance, roll the op amp or bypass the whole gain front end if you want. I use a 100k input Z and w/10k pot, 12db Gain and LM4562.
I know many in the Pass group will not like using an op-amp. But.... it sounds great and the drive stage remains a B1.
Besides, how man 5532s do you think were in the production audio chain of pretty much every piece of music you listen too?
Anyway, if you want the KiCad schematics I'd be happy to share them with or without PS on the same board.
Please forgive this shameless plug of my own creation. I know it's not an Iron Pre but it is small, cheap, flexible and sounds great IMHO.
Cheers.
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Yup. Can can be useful is some cases. I built mine to use with an F4, that has no gain. Alas, the F4 build is still in the queue but this still does well with all the music on my server that I have normalized to a level 6 dB less than typical.
B1K and IP are allready there. But if you allready have a B1, adding an autoformer is the easiest way. And no more active parts needed. If your circuit has an output protection resistor, you can omit that if going into an autoformer with some R.
I just finished selecting more than 100 sets of Jfets to help this along.
I believe you will be able to get one before too long....
Have you solved this issue?
If so, what will you build?
If not I may have a solution.
One single JFET to set gain before a B1 buffer stage.
One single JFET with gain is also loosely called JFET BOZ.
I have a circuit in SPICE with three J113 JFETs.
Gain is like 6 to 7 something.
U310 sims extremely well in your setup.
It is available at Mouser.
THD 0.006% is fantastic. You should go for this.
https://www.mouser.se/ProductDetail/InterFET/U310?qs=OxRSArmBDfyjFu46UMJb4A==
My sim shows THD 0.145% using three J113 at Voltage 18V supply.
Can you post a link to the jbox thread? Thanks!
Can you post a link to the jayboz thread? Thanks!
