Re: post #1101
I honestly can't keep up with the greedy boys. (I think Cinco stands for 5 months to 5 years behind.) While reading ZM's thread about SIT-3, I ran across some posts about his iron preamp and using the Curl complimentary follower to drive the autoformer. Then (thanks ZM) he said something about using one LSK170B up & one LSK170B down. This jogged my feeble memory to remember Erno Borberly's JFET articles and his Borberly Follower (like vacuum tube White Follower). Low Zout, drives hard loads and (YES!) single ended.
So here it is the BoFo-M-MoFo (well, the BoFo-M part). I'll integrate into power amp chassis, really happy with the front end now. Yay!
I honestly can't keep up with the greedy boys. (I think Cinco stands for 5 months to 5 years behind.) While reading ZM's thread about SIT-3, I ran across some posts about his iron preamp and using the Curl complimentary follower to drive the autoformer. Then (thanks ZM) he said something about using one LSK170B up & one LSK170B down. This jogged my feeble memory to remember Erno Borberly's JFET articles and his Borberly Follower (like vacuum tube White Follower). Low Zout, drives hard loads and (YES!) single ended.
So here it is the BoFo-M-MoFo (well, the BoFo-M part). I'll integrate into power amp chassis, really happy with the front end now. Yay!
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Has anyone tried to drive their MoFo with another amp.
Well in a moments Insanity I cobbled together a couple of rca jacks with 2 short pieces of wire to attach to the speaker outputs on my M2 clone.
I'm using a 10k alps pot in line between the cd and the M2 as a volume control.
I'm not sure if doing this would damage either the MoFo or the M2.
I've had the amps connected in this way for a couple of weeks now to no ill effect. All i can say is if you have these two amps give it a go.
Steve.
Well in a moments Insanity I cobbled together a couple of rca jacks with 2 short pieces of wire to attach to the speaker outputs on my M2 clone.
I'm using a 10k alps pot in line between the cd and the M2 as a volume control.
I'm not sure if doing this would damage either the MoFo or the M2.
I've had the amps connected in this way for a couple of weeks now to no ill effect. All i can say is if you have these two amps give it a go.
Steve.
Re: post #1101
I honestly can't keep up with the greedy boys. (I think Cinco stands for 5 months to 5 years behind.) While reading ZM's thread about SIT-3, I ran across some posts about his iron preamp and using the Curl complimentary follower to drive the autoformer. Then (thanks ZM) he said something about using one LSK170B up & one LSK170B down. This jogged my feeble memory to remember Erno Borberly's JFET articles and his Borberly Follower (like vacuum tube White Follower). Low Zout, drives hard loads and (YES!) single ended.
So here it is the BoFo-M-MoFo (well, the BoFo-M part). I'll integrate into power amp chassis, really happy with the front end now. Yay!
Very nice idea.
Since the MoFo already has C1,C2 in place is there a way to remove C100,C101 from the BoFo ? Would splitting the 19 or 24 Vdc into a bipolar supply do the trick ?
What else would we change ?
Thanks
Eric
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I also thought about this solution and I bought the Edcor PC600 / 15K trafo.Re: post #1101
I honestly can't keep up with the greedy boys. (I think Cinco stands for 5 months to 5 years behind.) While reading ZM's thread about SIT-3, I ran across some posts about his iron preamp and using the Curl complimentary follower to drive the autoformer. Then (thanks ZM) he said something about using one LSK170B up & one LSK170B down. This jogged my feeble memory to remember Erno Borberly's JFET articles and his Borberly Follower (like vacuum tube White Follower). Low Zout, drives hard loads and (YES!) single ended.
So here it is the BoFo-M-MoFo (well, the BoFo-M part). I'll integrate into power amp chassis, really happy with the front end now. Yay!
I will try but I am convinced that my tube-based KISS preamplifier can not be overtaken by this.
Meanwhile, I am going to experiment with the use of a large cap in polypropylene (ISKRA 500uF / 900V) at the exit of the SMPS. Previously I tested with two caps in PP (ISKRA 75uF / 900V) in parallel and the result was encouraging.
The "bottle" I had to fix it as I could .... acceptable I think.
the next step will be to fix Salas ultraBiB 1.3 after SMPS......
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Your "White" buffer cell won't work unless you set the gate of Q100 at half of the Vcc voltage (see attached B1 schematic: R2, R3, C2, D1, R103, R203).
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It 's true .... but I was thinking about this scheme in reality' ..... I am distracted
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In Borberly's write up, he shows a split supply but states that you still need to remove the DC offset. Output cap still has to be 10uF whether the offset is 100mV, or ~11V in my case, for low end response. Could split the supply and the transformer *might* tolerate 100mV of DC but I wanted to be able to power from single supply.
It does work as shown, I've been listening to it. I got curious if Papa's B1 works without the gate bias & quickly simulated. As long as AC coupled, doesn't need it. Added for stabiliy? Remove the input cap and no workie.
Maybe I'm missing something here?
If i am right the B1 Korg has a voltage gain of about 6x
and the Edcor 600/15k of 5x
which makes for a substantial total of about 30x...
Much of the requirements depend on how much your source delivers.
Case A
I have a weak source that can deliver 0.56Vpp
I would want 12Vpp maximum at the entry of MOFO
Hence i need a voltage gain of 21.4x or appr. 27db
Case B
I have a second source that can deliver 2.8Vpp
In this case i only need a voltage gain of 4.2x or 13 db
(The B1 Korg alone would have enough gain but it cannot swing the required voltage, or at least not with reasonable distortion)
Consequently
for Case A i would use the complete B1 Korg to feed the Edcor
for Case B i would only use the buffer of the B1 Korg preamp
Yeah, I was thinking about ordering the Edcor PC600-10k and WSM600-2.4K to try lower gain 12dB and 9dB versions. Not really needing the 14dB or so gain from the PC600-15K I already had in hand. They are so reasonably priced.... why not?
Still curious to hear about the B1 gate bias question from The One and Only. I used to be one of those, "Oh, all amplifiers sound alike, as long as the specs are good enough" guys. Until I started reading your Zen and other articles and building and trying things for myself... and most importantly listening.
Very interesting journey you got me started on Papa NP. Greatly appreciated.
This whole community is really an amazing learning experience.
Still curious to hear about the B1 gate bias question from The One and Only. I used to be one of those, "Oh, all amplifiers sound alike, as long as the specs are good enough" guys. Until I started reading your Zen and other articles and building and trying things for myself... and most importantly listening.
Very interesting journey you got me started on Papa NP. Greatly appreciated.
This whole community is really an amazing learning experience.
You are right. Similution is only as good as the models. When I used 2SK170 model distortion was a lot higher. The circuit makes sound without bias, just crappily. Its funny how much distortion our ears will tolerate.
Adding bias circuit for Rev 2, single supply version. Thanks juma for catching that.
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Cinco, no biggie there.
You can think of JFET as a variable resistor whose resistance (ie. current through Drain-Source channel) depends mainly on Gate-Source voltage. So if you don't have fixed DC reference on the gate your circuit conditions will be whimsical. Simulation won't help you there because simulated JFETs are always perfectly matched which is rarely the case in reality.
You can think of JFET as a variable resistor whose resistance (ie. current through Drain-Source channel) depends mainly on Gate-Source voltage. So if you don't have fixed DC reference on the gate your circuit conditions will be whimsical. Simulation won't help you there because simulated JFETs are always perfectly matched which is rarely the case in reality.
Hi,
I have two rather noob questions:
First, I have an Amp Camp Amp on order. Having just read the Pass F4 amp docs, it seems I should be able to bi-amp the ACA w/ a MoFo using the ACA to drive the MoFo? The ACA would drive the tweeter directly, and the MoFo, the woofers, using my speakers' XO in between. Do I have that right?
Second - this one a bit more out there. Pass' Beast with a Thousand JFETs. It's massively parallel to overcome the 20mA provided by each cell, but they run at ~25V each, no? He mentioned running two cells balanced in series, which would swing 50V? Wouldn't that be a suitable driver for the MoFo? That's a minimum of 4 JFETs, but when all the parts are the same, the actual count become less of a concern, especially when it's a few orders of magnitude lower than the Beast
Yes, they're hard to come by these days, and the diyaudio store is down to the D grades, but with little to no parallelization, even at 30mA Idss the dissipation will be negligible.
Am I mis-reading things, or should this work?
I have two rather noob questions:
First, I have an Amp Camp Amp on order. Having just read the Pass F4 amp docs, it seems I should be able to bi-amp the ACA w/ a MoFo using the ACA to drive the MoFo? The ACA would drive the tweeter directly, and the MoFo, the woofers, using my speakers' XO in between. Do I have that right?
Second - this one a bit more out there. Pass' Beast with a Thousand JFETs. It's massively parallel to overcome the 20mA provided by each cell, but they run at ~25V each, no? He mentioned running two cells balanced in series, which would swing 50V? Wouldn't that be a suitable driver for the MoFo? That's a minimum of 4 JFETs, but when all the parts are the same, the actual count become less of a concern, especially when it's a few orders of magnitude lower than the Beast
Yes, they're hard to come by these days, and the diyaudio store is down to the D grades, but with little to no parallelization, even at 30mA Idss the dissipation will be negligible.
Am I mis-reading things, or should this work?
Copy...snip....edit....paste.....snip...paste..... (Isn't this how ZenMod got his name?) 
Modify your B1 with modulated current sink turning it into a White cathode follower/Borberly source follower, i.e. BoFo. Lowers Zout, doubles current drive, a little higher distortion than unmodded B1.
Looking at the complexity makes me appreciate the elagance of the complimentary version. There are just so many more choices of N-channel JFETS though. Probably will use the LSK389 duals I just got. The P-channels are the tough ones to get.
I still need to listen to both to decide which to go with, still like the primarily 2nd ordered harmonic distortion of BoFo. That was the original goal M2-like amp SE.
Modify your B1 with modulated current sink turning it into a White cathode follower/Borberly source follower, i.e. BoFo. Lowers Zout, doubles current drive, a little higher distortion than unmodded B1.
Looking at the complexity makes me appreciate the elagance of the complimentary version. There are just so many more choices of N-channel JFETS though. Probably will use the LSK389 duals I just got. The P-channels are the tough ones to get.
I still need to listen to both to decide which to go with, still like the primarily 2nd ordered harmonic distortion of BoFo. That was the original goal M2-like amp SE.
Attachments
Cinco.....but...this....is a buffer....no gain whit thisCopy...snip....edit....paste.....snip...paste..... (Isn't this how ZenMod got his name?)
Modify your B1 with modulated current sink turning it into a White cathode follower/Borberly source follower, i.e. BoFo. Lowers Zout, doubles current drive, a little higher distortion than unmodded B1.
Looking at the complexity makes me appreciate the elagance of the complimentary version. There are just so many more choices of N-channel JFETS though. Probably will use the LSK389 duals I just got. The P-channels are the tough ones to get.
I still need to listen to both to decide which to go with, still like the primarily 2nd ordered harmonic distortion of BoFo. That was the original goal M2-like amp SE.