I've been building 300B circuits for the last few years. My favorite are the Western Electric 91A (Sound Practices version) and Fi Primer 300B.
Currently on the breadboard is a WE91A that's closer to the original, using only the second 310A (or 6C6) stage and not incorporating the feedback, except for the 1uF bootstrap filter on the output stage. I like it best so far, I think.
One nice thing about the Fi Primer circuit is that it has enough gain (about 0.25V input sensitivity) that you don't need a line preamp. Just put a volume pot after the input jacks and plug in a source.
Currently on the breadboard is a WE91A that's closer to the original, using only the second 310A (or 6C6) stage and not incorporating the feedback, except for the 1uF bootstrap filter on the output stage. I like it best so far, I think.
One nice thing about the Fi Primer circuit is that it has enough gain (about 0.25V input sensitivity) that you don't need a line preamp. Just put a volume pot after the input jacks and plug in a source.
Attachments
andyjevans,
These speakers have been serving you well it seems - if you're interested, specs and a review for Alpair 10 gen 1 drivers can be found on this thread:
https://www.diyaudio.com/forums/ful...alpair-10-german-test-review.html#post1806982
I did not consider the static resistance at low frequency because if you want consider it then it is part of the load. So it's impact is really small.
The cut at high frequency depends on the leakage inductance and the resonant behaviour.
The resonance behaviour itself depends on source impedance + series resistance + capacitance + leakage inductance with a resistive load. Unless the resonance of the transformer is in the audio band I cannot see where is the problem. In that case one might want to change the transformer. which would be the weak link...the LL1682 has better high frequency response than the bigger brothers. Sad to say but that is.
With an inductive load it changes but again little consequence because if such inductive load is high it also means that the FR of the speaker is a rising one compensating for the decreasing power....unless you have a capacitive load which I have never seen with a fullrange or a normal tweeter it will be fine in 99% of cases, so to speak.
Last edited:
VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 1
The 6CB5a has even lower plate resistance than a 300B. With the LL1692, by memory, Thomas found out the frequency response started to fall around 70 KHz into 8R standard load. If you search in the site you should find that one...
The 6CB5a has even lower plate resistance than a 300B. With the LL1692, by memory, Thomas found out the frequency response started to fall around 70 KHz into 8R standard load. If you search in the site you should find that one...
Ideas...DG300B – Neurochrome
And there is a diyaudio thread as well...DeathTrap400™ : : A Pretty Damn Good 300B Amp
Best,
Anand.
Hello forum,
this is my first post and I´ve got the same question, like the starter.
I don`t want to highjack this thread and if necessary I´ll open a new one.
In past two decades I´ve been building a few amps and preamps. First one was the Hagtech Cornet, last one was an Aleph J.
The Aleph is actually running into W8-1772 Tang Band FR speakers with 95db.
The music I´m listenting to is mainly Jazz, 6ts, Indie and Pop.
I´m looking for a 300b SE schematic that will produce results that are on par with the Aleph J or perferably better with good bass response.
The Aleph should not be replaced but supplemented. Budget is around 2k max. Less would be better.
What would you recommend? Done some research and looked at some D3A schematics like the ones of Triode Dick. Would that be an an option?
And where would you buy the tranny set? Am located in Europe and would like to source from here.
Many thanks and all the best
Rene
this is my first post and I´ve got the same question, like the starter.
I don`t want to highjack this thread and if necessary I´ll open a new one.
In past two decades I´ve been building a few amps and preamps. First one was the Hagtech Cornet, last one was an Aleph J.
The Aleph is actually running into W8-1772 Tang Band FR speakers with 95db.
The music I´m listenting to is mainly Jazz, 6ts, Indie and Pop.
I´m looking for a 300b SE schematic that will produce results that are on par with the Aleph J or perferably better with good bass response.
The Aleph should not be replaced but supplemented. Budget is around 2k max. Less would be better.
What would you recommend? Done some research and looked at some D3A schematics like the ones of Triode Dick. Would that be an an option?
And where would you buy the tranny set? Am located in Europe and would like to source from here.
Many thanks and all the best
Rene
Thanks Dave.
How about the 300b schematics? What is actual state of the art and payable for Jazz, 6ts, Indie and Pop?
How about the 300b schematics? What is actual state of the art and payable for Jazz, 6ts, Indie and Pop?
Last edited:
For state of the art with a sub 2K price range, get yourself a Tubelab SE 2 board, perhaps Coleman filament regulator boards and the best iron your budget allows.
Pass DIY Addict
Joined 2000
Paid Member
I built a parafeed version of the WE 91 300B amp that Joe Roberts published in Sound Practices back in 1992. This version was created by Paul Joppa, who works at Bottlehead. The total cost fits what you asked for in your first post. You'll need a bit of leg work to track down the transformers (original iron was all MagneQuest stuff from Mike), but that's half of the fun!
Schematics for the design are about half way down this thread.
Schematics for the design are about half way down this thread.
Attachments
My new speakers are a two-way line source design that uses planar drivers. The midrange driver rolls off at around 180Hz, so a single pole filter is used in front of the amp at approximately the same frequency. The lower few octaves are handled by a separate powered servo subwoofer (one per channel).
Tom's Neurochrome DG300B amp likes great, but I didn't think these PCBs were available any longer. I've used a few of Tom's other designs.
Wow, many thanks for the answers.
And a really nice Amp Eric. How about its sonics?
What do you all think of this one?
http://www.triodedick.com/pdf_files_td/LittleCeasar.pdf
Made a mistake. Budget is about 2.5. Thought in Euros not in $.
And a really nice Amp Eric. How about its sonics?
What do you all think of this one?
http://www.triodedick.com/pdf_files_td/LittleCeasar.pdf
Made a mistake. Budget is about 2.5. Thought in Euros not in $.
