| supernet |
I was looking around for quite some time trying to find a simple buffer to drive my high gain power amplifier and now I am really interested about this B1 project, so Mr. Pass are there any news about it?
Will it contain also volume control and selector as complete preamp unit? |
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| Nelson Pass |
There is a full DIY article scheduled to appear on EnjoytheMusic.com
at the beginning of July.
Also, you will shortly be able to buy one.
It looks like this from the outside: |
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| Nelson Pass |
| and like this on the inside: |
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| Steve Eddy |
| quote: | Originally posted by Nelson Pass
and like this on the inside: |
Would those happen to be PEC carbon pots?
se |
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| Zen Mod |
besides fuglyness ..... interesting ...... input cap , output cap , comp. jfet buff as in Papa's Lightspeed , single voltage supply ?
less is more :D :Popworm: |
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| EUVL |
I didn't see a source selector knob at the front panel.
Am I missing something ?
Patrick |
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| mpmarino |
| quote: | Originally posted by EUVL
I didn't see a source selector knob at the front panel.
Am I missing something ?
Patrick |
toggle switch
;) |
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| Babowana |
It looks having two inputs:
(1) Passive pre with no buffer
(2) Passive pre with the buffer
and one output to the power... |
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| Vix |
| quote: | Originally posted by Zen Mod
besides fuglyness ..... interesting ...... input cap , output cap , comp. jfet buff as in Papa's Lightspeed , single voltage supply ?
less is more :D :Popworm: |
To me it looks like there 's no input cap, just an output one. Those small blue square things look like local decoupling PSU caps?
Maybe my eyes are deceiving me...:Popworm: |
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| Zen Mod |
| quote: | Originally posted by Vix
To me it looks like there 's no input cap, just an output one. Those small blue square things look like local decoupling PSU caps?
Maybe my eyes are deceiving me...:Popworm: |
ya remember that all roads goes/leads to Rome ......... or - that's milion and one way to skin the cat :clown:
so - there is just no need to guess exactexactexact topology ......
besides that - you know that Papa must make it foolproof , because he sells them ...... |
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| jacco vermeulen |
Gee-Zus Bruce almighty,
you can see a clear as crystal trace running from the big foil cap to the output hotline.
(and to think that some glare types have the nerve to call moi a blind mole bug-ger) |
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| supernet |
Thank you Mr. Pass. Photo explain it all :D
Could the 10 uF output caps be replaced if the power amplifier has input cap? |
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| Zen Mod |
| quote: | Originally posted by supernet
.........
Could the 10 uF output caps be replaced if the power amplifier has input cap? |
yup |
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| twitchie |
Looks far too complicated and messy for my liking ;)
Are all those components really necessary? :clown:
on a more serious note - the pcb looks like it was milled because of all those straight lines. Is this a prototype board? |
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| mrothacher |
Very cool.
P.S. I really dig the First Watt font. It's very Led Zeppelin / Rune-ish. |
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| dw8083 |
I just love this forum and the participants here.
Within an hour or two members started reverse engineering the B1 from Nelson's acute angled picture. The forum will have self-documented the DIY article before Nelson publishes it.
Prediction:
Choky will have a complete circuit and boards with customized improvements made shortly called the BBF (Best B1 First), or ABC Pre for "Another B1 from Choky" or something!
People here are simply great! Cannot wait for the upcoming BurningAmp in October again.
-David |
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| Zen Mod |
| quote: | Originally posted by dw8083
I just love this forum and the participants here.
Within an hour or two members started reverse engineering the B1 from Nelson's acute angled picture. The forum will have self-documented the DIY article before Nelson publishes it.
Prediction:
Choky will have a complete circuit and boards with customized improvements made shortly called the BBF (Best B1 First), or ABC Pre for "Another B1 from Choky" or something!
People here are simply great! Cannot wait for the upcoming BurningAmp in October again.
-David |
naah .......
I just dropped entirely messing with electronic .... Papa already made everything I can even imagine :clown: .........
waidaminid............. I still have my toobz .......... :rofl:
seriously - Papa already sez lately everything needed to make nice and not complicated buff stage
my comments here were/are just my another expression of wackoo :worship: |
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| dw8083 |
Sorry for off topic.... Choky, are you coming to Burning Amp this year? I hope so! You were missed last year.
-David |
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| Zen Mod |
| quote: | Originally posted by dw8083
Sorry for off topic.... Choky, are you coming to Burning Amp this year? I hope so! You were missed last year.
-David |
tnx for nice words , but I think that I'll be missed this year too , except in case that I find some unexpected funds :clown: .....
anyway - do not worry - I'll do everything I can on two fronts :
1 . I'll hate ya all in these days (same as first time )
2.I'll do everything I can to rise my overall financial situation in next period , so my presence on BAF No.3 should enormously rise overall importance of Festival .....
:rofl:
(ps . if nothing else - I'll try to send Brunhilde to AR2 , for presentation ;) ) |
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| dw8083 |
| Hi Choky, sent you a PM. -David |
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| jacco vermeulen |
We were thinking of shipping a body bag over to BA.
You guys are required to check the temperature and USPS the thing back to Serbia before he starts to melt.
(I was informed, off the record, that ZM will be releasing the Stinky, the companion of the already introduced Shiny. After that, the BarF-What is scheduled.) |
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| Zen Mod |
ya ppl nutz - seems that OT virus is spreading :rofl:
anyway -
@Jaccovitty - I feel jeopardy ......... slight possibility that some terrorists can grab bodybag , and force me for good to keep my finger in dutchie tide fence ........ :clown:
( I heard some sayings that in dutchland is harder and harder to find adequate wackoos for that job :cool: ) |
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| jacco vermeulen |
I suppose the B1 case is a new standard issue series, the Key Largo for all the B-number offspring ?
(we're all becoming too fat for hard hole labor overhere, but you'd still be a tight fit dike plug) |
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| Manu |
| quote: | Originally posted by dw8083
I just love this forum and the participants here.
Within an hour or two members started reverse engineering the B1 from Nelson's acute angled picture. The forum will have self-documented the DIY article before Nelson publishes it.
Prediction:
Choky will have a complete circuit and boards with customized improvements made shortly called the BBF (Best B1 First), or ABC Pre for "Another B1 from Choky" or something!
People here are simply great! Cannot wait for the upcoming BurningAmp in October again.
-David |
:D |
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| mlloyd1 |
what!?!?!?
no blue front panel LED?
:D
mlloyd1 |
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| vdi_nenna |
| Is there a price range for this little guy? |
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| mpmarino |
| quote: | Originally posted by Zen Mod
besides fuglyness ..... interesting ...... input cap , output cap , comp. jfet buff as in Papa's Lightspeed , single voltage supply ?
less is more :D :Popworm: |
You missed a couple of things. You can clearly see the 221r resistors, 9.1v zeners, 220uf caps, and 3r 3watt powder blue Pannys. After all, it wouldn't be Pass without it :devilr: |
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| Nelson Pass |
| quote: | Originally posted by mlloyd1
no blue front panel LED?
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I used the hole for the switch... |
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| Babowana |
Seems B1 is ever on.. so no need of the on-off indication..
Maybe, I'm too straight forward without applying joke or humor..
If so, my style must be grown by my serious job..
Anyhow, the holes should be filled in.. by the right ones.. |
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| Vix |
| quote: | Originally posted by Babowana
Anyhow, the holes should be filled in.. by the right ones.. |
| quote: | Originally posted by Nelson Pass
I used the hole for the switch... |
Yeah, the problem is when you want to put two things and have only one hole :D . So, the switch got a priority. No blue LED. Or, maybe, as the buffer is supossed to be the "invisible" piece in the signal chain, there should be no indication that it's there, no? :D |
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| jacco vermeulen |
Naah, it's a "no holes barred" approach. :clown:
But D.. boy, what an uggie switch. |
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| Vix |
| quote: | Originally posted by Babowana
It looks having two inputs:
(1) Passive pre with no buffer
(2) Passive pre with the buffer
and one output to the power... |
I'd say:
(1) Passive pre with the buffer-with the volume control
(2) Passive pre with the buffer-without volume control. i.e. just a plain buffer.
P.s.
Jacco, I like these switches! :devilr: |
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| jacco vermeulen |
| quote: | Originally posted by Vix
(1) Buffer with volume control (2) buffer without volume control. |
You don't need a switch for that, not at the front anyway. |
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| Nelson Pass |
Actually, it's just two switched inputs. They both go through the
volume control and buffer. |
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| jacco vermeulen |
Beeh, no fun with reply answers that fast.
Speaking of Buffy the Amp Slayer, you guys also have that back of your neck airflow notion-ness something that usually is, isn't lately ?
Only The Shadow knows. |
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| Zen Mod |
| quote: | Originally posted by jacco vermeulen
Beeh, no fun with reply answers that fast.
Speaking of Buffy the Amp Slayer, you guys also have that back of your neck airflow notion-ness something that usually is, isn't lately ?
Only The Shadow knows. |
ya crazy as rotten barrel , even I have major PITA to understand you this time ;
ya mean on GR ? |
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| jacco vermeulen |
| I definitely do not mean BL. |
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| Zen Mod |
| quote: | Originally posted by jacco vermeulen
I definitely do not mean BL. |
well - I definitely do not meant on Gray ......... or Violet ........ or Blue
;)
(Grey ........... is that ringing a bell ?) |
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| Vix |
| quote: | Originally posted by Nelson Pass
Actually, it's just two switched inputs. They both go through the
volume control and buffer. |
That was too easy!! :D :Rofl:
What next? "It's just a single-ended 2SK170 BL, with another 2SK170 BL as a current sink, with a single PSU, CRC" ? :rofl:
To Jacco and Zen Mod: Or is it GR? Whatever that means...:rofl: |
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| jupiterjune |
GR last posted here 5/25. Anyone heard from him?
JJ |
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| Zayan |
Someone guesses this suppose to be the input circuit from F4.
:smash:
Zayan |
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| juma |
| yes, it looks very similar to F4 input buffer :) |
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| Nelson Pass |
| It is not the same. This buffer is single-ended. |
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| stefanobilliani |
| current sourced ? |
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| Babowana |
Source follower,
a bit adding the 2nd harmonics? |
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| syncmaster |
| Common Gate :D |
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| juma |
| quote: | Originally posted by Nelson Pass
It is not the same. This buffer is single-ended. |
Like this ? |
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| Vix |
| Or, can it be something like "Buffer for Blues", but, instead of the resistor (R 19) it uses a Jfet current source? |
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| jupiterjune |
No Erno, not like that. |
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| Krzysztof |
Hi Nelson,
Did you used in B1 buffor pre following transistors : 2SK170 and 2SJ74 ? |
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| Nelson Pass |
| quote: | Originally posted by Krzysztof
Hi Nelson,
Did you used in B1 buffor pre following transistors : 2SK170 and 2SJ74 ? |
I refer you to posts 45, 46, and 47
The devices are either 2SK170 or 2SK370 |
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| mlloyd1 |
for folks that want to read about design of the jfet single ended buffer, i wanted to share again this article from dennis feucht.
i first saw this circuit in the early 70's (yes, i am an old phart :-) ) in some old (even back then) national semiconductor datasheets showing test circuits for some of their parts.
i don't have access to an audio precision (maybe mr. pass can share some data at some point), but you can get pretty good performance from this circuit using some cheaper, easier-to-get jfets like the 2N5484, etc. so, save your 2SKxxx for your phono preamps.
:D
enjoy!
mlloyd1 |
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| Nelson Pass |
| quote: | Originally posted by mlloyd1
for folks that want to read about design of the jfet single ended buffer, i wanted to share again this article from dennis feucht.
i first saw this circuit in the early 70's (yes, i am an old phart :-) ) in some old (even back then) national semiconductor datasheets showing test circuits for some of their parts.
i don't have access to an audio precision (maybe mr. pass can share some data at some point), but you can get pretty good performance from this circuit using some cheaper, easier-to-get jfets like the 2N5484, etc. so, save your 2SKxxx for your phono preamps. |
An oldie but a goodie. I dropped the Source resistors on mine.
I don't have 2N5484 distortion curves, but the 2SK170 is pretty
spectacular, and the LSK170 is available and cheap enough.
:cool: |
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| Vix |
| quote: | Originally posted by Nelson Pass
...but the 2SK170 is pretty spectacular...
:cool: |
:cool: :) :cheers: |
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| mlloyd1 |
agreed!
also, oddly enough, the 2SK369 is still around and relatively cheap as well.
| quote: | Originally posted by Nelson Pass
... but the 2SK170 is pretty spectacular :cool: |
mlloyd1
(who is hiding his 2SK146 and 2SJ73 stash from the wife for fear that she will sell them on ebay! :eek: :) ) |
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| arupg |
| Love the knobs on the Front panel - a reminder from the Theshold days..... |
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| mlloyd1 |
nelson:
anything you can share at this point on the differences in the distortion spectra for these buffers built with or without source resistors?
the answer "be patient and wait for my article" is a valid response.
:)
mlloyd1 |
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| bappe |
Hi,
I do not know Nelsons set-up other than that it is SE without source resistors but here is what I am using. I have tried a number of different variations on the theme but yhis is the one i like best so far. I need alot of swing and this one delivers.
Anders |
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| Nelson Pass |
| quote: | Originally posted by mlloyd1
anything you can share at this point on the differences in the distortion spectra for these buffers built with or without source resistors? |
Actually that's the most interesting part - not the source resistors
but the spectra.
The piece will be done shortly, however I have created it without
deciding on a destination for it.
:cool: |
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| mlloyd1 |
bappe;
thanks for sharing. i have done something somewhat similar myself.
i am curious to know if there was any reason you choose to cascode the current sink the way you did using the 2SA970 versus using another 2SC2240?
mlloyd1
| quote: | Originally posted by bappe
... |
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| bappe |
I'm on my cellphone so i'll keep it short. The idea is to lower the voltage swing over both jfet's in a simple and thermally stable way. I can elaborate a bit more around this when i get back to my pc.
Anders |
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| jam |
Nice idea Anders
It would be intresting to compare source resistor vs distortion plots for the above topology as well as compare it to the full comp version below.
Jam |
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| lumanauw |
| What's the bipolars for? It should work with drains straight to rails? |
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| MRupp |
| quote: | | What's the bipolars for? It should work with drains straight to rails? |
This might explain it - scroll down to the section Super Symmetrical Cathode Follower : http://www.tubecad.com/2007/04/blog0104.htm
At least for triode buffers it should be better to bootstrap the cathode follower so that it sees a constant plate to cathode voltage. But I'm not sure yet if this applies to the same degree to JFETs. |
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| jam |
| They allow for more swing with higher supply rails and should improve bandwidth by reducing non-linear capacitance of the j-fets. |
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| lumanauw |
| If that is the intention, will put capacitor//to inner 15k (for bootstrapping towards output node) perform better? |
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| mlloyd1 |
i understand why cascoding is done. i'm asking why it was done a certain way.
just in case my question wasn't clear ...
refer to the two buffer schematics in the attached schematic.
why cascode the current sink (j2) with a pnp (q4) instead of cascoding the current sink (j4) with npn (q3). |
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| jam |
Hi Michael,
I think the second method might be better (cascoding the current source).
Maybe Mr.Pass could shed some light on this............but then again, in the case of the B1, cascoding might not be an improvement besides you can run into stability issues when you cascode.
I can't wait for the article to come out............maybe if we found some way to prod Mr.Pass to get it out sooner.:D
Jam
P.S. Mr.Pass wrote a great article on cascode amplifier design. Here is the link
http://passlabs.com/pdf/articles/cascode.pdf
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| mlloyd1 |
oops, sorry, in the schematic i posted, i forgot the "bootstrap" connection that bappe was using (the vds of the jfets is not fixed)
please remember there is a connection between the output and junction of r1 and r11 for the left hand circuit and a connection between the output and the junction of r6 and r8 for the right hand circuit.
i'll fix the schematic when i get to my other computer.
of course, we could always argue about the virtues of fixed versus telescopic cascodes ...
:D
mlloyd1
| quote: | Originally posted by mlloyd1
i understand why cascoding is done. i'm asking why it was done a certain way.
just in case my question wasn't clear ...
refer to the two buffer schematics in the attached schematic.
why cascode the current sink (j2) with a pnp (q4) instead of cascoding the current sink (j4) with npn (q3). |
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| mlloyd1 |
corrected schematic attached
mlloyd1
| quote: | Originally posted by mlloyd1
oops, sorry, in the schematic i posted, i forgot the "bootstrap" connection that bappe was using (the vds of the jfets is not fixed)
please remember there is a connection between the output and junction of r1 and r11 for the left hand circuit and a connection between the output and the junction of r6 and r8 for the right hand circuit.
i'll fix the schematic when i get to my other computer.
of course, we could always argue about the virtues of fixed versus telescopic cascodes ...
:D
mlloyd1
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| stefanobilliani |
Fantastic . I am going to build in perforboard p2p this piece .
I have a question that raises now . My F3 is coupled to a buffer input stage like the Buffer for Blues or like the Zen V4 .
Is it the time to leave it for this loveable B1?
Will I have better satisfaction with B1 ?
Thanks |
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| thomasfw |
Is JFet BOZ + B1 = B3 ??
Thanks !! |
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| stefanobilliani |
Some time ago the Linear systems so kindly sent me 5 lsk389 as samples . I think I will use 2 of them.
:cool: |
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| fredlock |
| Mr. Pass, would this passive preamp be compatible to F5 amp? What I meant is, it might not drive the F5 to full swing or performance. Your thoughts? |
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| udailey |
| Do the 2sk170 need to be matched or not? |
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| vdi_nenna |
| quote: | | Do the 2sk170 need to be matched or not? |
It is recommended.
| quote: | | The best performance generally comes from matching the Idss of Q100 and Q101, and also Q200 and Q201. |
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| enjoythemusic1 |
Hi Everyone,
Wow you guys are on the ball! Yes, the review and Nelson's write up now appear on Enjoy the Music.com. i spread them between the two magazines as it will come built/assembled (Review Magazine) and as a kit (new DIY Magazine). Links were posted on this thread, though to keep it simple:
Review Of Assembled Unit:
http://www.enjoythemusic.com/magazi...reamplifier.htm
Nelson Pass' Write Up For DIY Magazine:
http://www.enjoythemusic.com/diy/07...reamplifier.htm
BTW: i am STILL HIRING writers for the DIY Magazine. And YES you WILL be paid for your efforts. If interested, e-mail me at Rochlin AT EnjoyTheMusic DOT com with the subject being all caps DIY WRITER INQUIRY.
Many thanks and my hopes are to spread the word of the joys in DIY, s my first 'day job' was working for Heathkit Electronics many years ago :)
Thanks again and as always, in the end what really matters is that you... |
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| Steve Eddy |
FYI, small typo in the seventh paragraph of "Side C." "JFET" got turned into "JGET." :D
se |
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| bappe |
| quote: | Originally posted by vdi_nenna
It is recommended.
|
Hi!
IMHO i am not so sure about that recommendation. I would chose a Idss for the current sink that is a few mAmps lower so that the upper one is running a bit under its Idss, this to avoid gate current. Since Nelson is using a coupling cap there is no need to worry about a few mV DC on the output.
BR,
Anders |
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| bappe |
| quote: | Originally posted by bappe
Since Nelson is using a coupling cap there is no need to worry about a few mV DC on the output.
|
Or half the supply voltage, did not see that it was single supply.......
/Anders |
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| Christer |
| quote: | Originally posted by bappe
Hi!
IMHO i am not so sure about that recommendation. I would chose a Idss for the current sink that is a few mAmps lower so that the upper one is running a bit under its Idss, this to avoid gate current. Since Nelson is using a coupling cap there is no need to worry about a few mV DC on the output.
BR,
Anders |
Or use source resistors on both devices, as is usually done with this topology. That way you can take quite a lot of input voltage before the PN junction becomes forward biased even with low impedance loads. Borbely recommends 22 Ohms, if I remember correctly. In my buffer I use 10 Ohms as John Curl recommended. Actually, I am curious why Nelson doesn't use any source resistors.
I also do not have any series output resistor, but perhaps a smallish one, like 50 or 100 Ohms, would be good considering the RFI discussions in the Blowtorch thread. I also use dual 18 V supplies so there is no need for an output cap if matching the JFETs. I think the DC offset was under 2 mV on both channels when I last measured.
Having enough series resistance between input and gate so one doesn't exceed the max gate current of 10 mA with highest possible/probable input voltage if the junction is forward biased by accidentily shorting the output might be a good idea.
BTW Nelson, I used the spare hole for a LED instead of a switch on my buffer. :) |
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| udailey |
Thanks for the response/explanation/conjecture guys. I ended up buying some matched from tech-diy. Then the mail came today. I got a notice that a package from China is sitting in the post office for me. I had given up on them, but as Murphy would have it.. this package has matched 2sk170's in it. Ordered the rest of my parts and a tiny regulated wall wart from DigiKey today. Will use the two 50k pots I have hooked into my ChipAmp for the B1 and should be in business to use this to drive my drive my ChipAmp and F5 soon :)
Loved the new chipamp I built so I am sure to fall over when I hear the F5 :) |
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| enjoythemusic1 |
Steve,
MANY, many thanks! Am uploading the fix now. ALL help is ALWAYS appreciated! |
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| mpmarino |
Congrats Nelson ;)
You are on a roll - a looong roll. Thanks for taking us along for the ride. |
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| Vix |
Hi,
I was wondering if it would be more convenient to use a dual power supply, +-9 v . This is because it seems easier to 'transform " this buffer into a first or a second order active crossover if it uses a dual PSU.
If so, R2, R3, R103, R203, D1, C2 and C3 would be removed. A resistor would be attached from the gate of Q100 (Q200) to ground, and, if you want to make a 1st order high pass filter, C100 (C200) could be scaled down for a specific frequency. For a second order high pass filter, I would add another resistor going from the source of Q100 (Q200), then to the front of C100 (C200), plus one more cap...(you know the topology of the second order high pass filter).
Please let me know if this idea doesn't work...
Regards,
Vix |
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| MRupp |
| quote: | | I would chose a Idss for the current sink that is a few mAmps lower so that the upper one is running a bit under its Idss, this to avoid gate current. |
Following previous discussions on diyaudio I think this is not strictly true. You can forward bias this particular JFET to between +0.2 and +0.3. Volts, depending on chip temperature, before you see any significant gate currents, and running the JFET at full IDSS appears to be about optimal. |
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| stefanobilliani |
Today I builded the Circuit . Values are ok , it works . But the LSK389 are pretty hot . Is that normal?
Also ... may I go for R105 and R205 to 100Kohm ?
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| udailey |
Stefano,
How does it sound!?
Uriah |
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| stefanobilliani |
I am listening to the F5 and going to test with the F3 too .
Very good for now .
:cool: |
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| Krzysztof |
Hi friends,
I just look into internal photos of B1 ( attached on enjoythemusic web site - review ) and I see third small ( blue colour ) capacitor laying between both channels in the middle of the PCB. His two traces coming directly into direction of both 2SK170 transistors on right channel. One leg of this small one connect probably GATE in first transistor and SOURCE in other one. I don`t see such small capacitor on attached circuit diagram ! |
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| jacco vermeulen |
Do not judge a book by it's cover.
The B1 schematic does contain 3 of the Beyschlag MKP416 caps.
Although the 1uF value only comes in 15mm lead spacing, it's safe to assume it has it's leads soldered to pads at the bottom and not at the top.
The one you see is a ground trace, the gate of the bottom JFET connects to it, as does bypass cap C3 of the voltage divider.
Which makes the second trace the one that supplies the 9Vdc to the gates of both input JFETs through the 1M resistors, and why the 2 traces run between both channels. |
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| massimo |
Jacco is right: most probably the loonely blue cap in the middle of the borad is C3. Good idea to place it closer to the Jfet: it lowers the impedance of the tracks.
It looks like Nelson uses (at least in pictured unit) some BC polyester (mylar) caps for C3, C100 and C200 even if in the article he suggested some BC polypropylene ones for C100 and C200 (according to the Digikey part number).
The latter are grey instead of blue and much bigger (15 mm leads spacing instead of 5 mm).
I don't think the polypro caps are soldered underneath. |
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| despotic931 |
| quote: | Originally posted by fredlock
Mr. Pass, would this passive preamp be compatible to F5 amp? What I meant is, it might not drive the F5 to full swing or performance. Your thoughts? |
I am also interested in the B1 with the F5, well actually I'm really interested in the B2 driving two F5s... Will i need a preamp with more gain to really drive the F5s, or will the B1/2 handle it? |
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