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Old 21st June 2018, 07:08 AM   #1181
sontero is offline sontero  Italy
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will you add the edcor trafo?
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Old 21st June 2018, 09:27 AM   #1182
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by Cinco View Post
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.
Papa Borbely's White Cathode follower is better than other (shown here) JFet followers when feeding heavier loads ; with benign loads , it's unnecessary complication and (to my ears) slightly worse (in other words - more ) sounding

on last iteration of Iron follower pcb I have provision for Borbely WCF (parts) and in that case (even if Iron Turtle AVC is known and benign load) , one can choose between two type of buffers and leave one which THD spectra suits better/more
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Old 21st June 2018, 12:46 PM   #1183
Cinco is offline Cinco  United States
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Quote:
Originally Posted by sontero View Post
will you add the edcor trafo?
I should have cut and pasted Papa M2 trafo and zobel as well. Yes, that's what I'm listening to now. Evolution went:

Source -> Slagle AVC -> MoFo (muffled sounding)
Source -> Slagle AVC -> B1 (U401 jfet) -> MoFo (no gusto)
Source -> Slagle AVC -> B1 (U401 jfet) -> Edcor PC600-10k AF -> MoFo
(better but still, where's the bass/beef?)

Oh, B1 output cap too small, was 2.2uF which worked on 50k+ loads, not so good on 1.4k edcor load. 10uF much better. (Bass there, still strained sounding)

Source -> Slagle AVC -> B1 (LSK170B jfet) -> Edcor PC600-10k AF -> MoFo
(getting there still too forward)

Source -> Slagle AVC -> passive baffle step corection -> B1 (LSK170B jfet) -> Edcor PC600-10k AF -> MoFo
(Tonal balance right, lacking dynamics)

Source -> AVC -> BSC -> BoFo -> Edcor AF -> MoFo (Ah, now now we're talking... I mean singing...)
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Old 21st June 2018, 01:04 PM   #1184
Zen Mod is offline Zen Mod  Serbia
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source > buffer > AVC fed on -12db tap > MoFo

that , if AVC is older one , with one rotary switch

later one , with combo of two switches is tricky to use that way ...... even if I have a feeling that I need to invest some more staring at schematic

Click the image to open in full size.
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Old 21st June 2018, 01:07 PM   #1185
Cinco is offline Cinco  United States
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Quote:
Originally Posted by Zen Mod View Post
Papa Borbely's White Cathode follower is better than other (shown here) JFet followers when feeding heavier loads ; with benign loads , it's unnecessary complication and (to my ears) slightly worse (in other words - more ) sounding

on last iteration of Iron follower pcb I have provision for Borbely WCF (parts) and in that case (even if Iron Turtle AVC is known and benign load) , one can choose between two type of buffers and leave one which THD spectra suits better/more
I'll have to take some time to read ALL of your Iron thread instead of reinventing already perfected wheel. Although lots learned through trial by fire.... "Ouch! that didn't work." Concepts locked in mind much better by hard lessons.

ZM, you (along with Papa) inspired me to give it a try and get more iron in my signal chain and to let transistors do what they do best, current amplification.

I'm glad I did.
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Old 21st June 2018, 01:09 PM   #1186
Zen Mod is offline Zen Mod  Serbia
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tell me which Slagle AVC you have and what size of cojones your source is having
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Old 21st June 2018, 01:14 PM   #1187
Cinco is offline Cinco  United States
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Yep, I have the old one. Too much cheap skate to buy more expensive model. Another combo to try.

Thanks for the suggestion..... I'll have to put old resistive attenuator back in for volume control.

Source is 2Vp pro-level audio card or 1.5Vp diy phonograph pre.

Last edited by Cinco; 21st June 2018 at 01:17 PM. Reason: Added info
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Old 21st June 2018, 01:29 PM   #1188
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by Cinco View Post
Yep, I have the old one. Too much cheap skate to buy more expensive model. Another combo to try.

Thanks for the suggestion..... I'll have to put old resistive attenuator back in for volume control.

Source is 2Vp pro-level audio card or 1.5Vp diy phonograph pre.
in that case , try as I suggested above

choose input tap on AVC to have enough oomph for MoFo

of course , include your BSC if you need it ..... maybe in between AVC and MoFo ......
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Old 21st June 2018, 10:41 PM   #1189
Cinco is offline Cinco  United States
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Originally Posted by Zen Mod View Post
in that case , try as I suggested above

choose input tap on AVC to have enough oomph for MoFo

of course , include your BSC if you need it ..... maybe in between AVC and MoFo ......
I've often wondered if it makes sense to have:

source -> AVC (-27dB to -15dB) -> Buffer -> AVC (+14dB) -> MoFo
or
source -> AVC (-27dB to -15dB) -> M2 (+14dB)

Why not mount the AVC in the middle of the amp for attenuation control? Of course can wire AVC for some gain. The only drawback I see would be power available to speakers is limited by music source voltage. That and the Slagle-former is WAY more $$$ than Edcor PC series little iron gems. Remember my being a penny pinching miser.

Works if full blown partying levels attainable at listening position with +6dB. The speakers are fairly sensitive at +92dB SPL@1W1m.... Let's see 2Vpk, +6dB gain makes 4Vpk. That's about a 1W amplifier. Listening position about 2m, double the distance, so +92dB - 6dB SPL = 86dB. Great for low level listening but not rocking out.

Maybe a switch on the MoFo to for 0dB or +14dB, bypassing or not the Edcor???
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Old 21st June 2018, 11:09 PM   #1190
Zen Mod is offline Zen Mod  Serbia
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well , it seems everyone here is having it's own strong weed ....... so it's hard to me to follow you , when we are on different stufffffff

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