Not a Guitar Amp

[p2pAmps]

This is something I have been meaning to build for awhile now, a cool hifi amp.  Sure glad I did as it sounds amazing.  Sporting 4 KT120s, 5AR4, and 3 12AU7s...  Nice change of pace

[jjasilli]

 

[tubenit]

That's remarkably cool!  What a fantastic project!  THANKS for sharing your success with it.   

With respect, Tubenit

[DummyLoad]

nice. but why is choke on the left side anchored with only one bolt/nut?


--pete

[shooter]

  

amazing workmanship, and the octals for speakers, killer!

using DC filaments?  I see a bridge under but a tube rec above

[p2pAmps]

 

amazing workmanship, and the octals for speakers, killer!

using DC filaments?  I see a bridge under but a tube rec above

Hey Shooter, yeah, DC filaments for sure.  The small circuit board is a TDR for a slow start should I decide to use a SS rectifier (no bridge). These amps are very cool and give a McIntosh a serious run for the money

[p2pAmps]

nice. but why is choke on the left side anchored with only one bolt/nut?


--pete

I know huh LOL.  Thats the way the chassis was drilled and I didn't want another hole in the top so I let it sit the way it sits.  It's not causing a problem but does kinda rub me the wrong way too :)

[p2pAmps]

BTW, those two switches in the middle are triode/pentode switched, kinda cool.  I'm using it on the triode ultra linear mode which is more powerful and sounds good for the stuff I'm listening to. 

[shooter]

so what's the amp using to drive the air

[p2pAmps]

so what's the amp using to drive the air

The rest is a McIntosh MX130 pre, Marantz 6300 turntable, and a set of JBL 120ti speakers.  Next I will build a tube pre and a DAC...

[Ed_Chambley]

Big time soup up of a Dyanco.  Tube pre.  I go back and fourth.  I have a very nice Marantz type tube pre I have built.  I have too much junk anyway.  This looks great.  Where did you source the chassis?

[DummyLoad]

don't know if his is from the same source, but you can get one here ed.


--pete

[Ritchie200]

That is too cool and affordable considering some of the extreem cork sniffer kits and finished products out there.


I hope this isn’t too much of a hijack...  I went on their website and noticed an auto-bias circuit. How does this work?


Jim

[jjasilli]

@Jim:  https://forum.audiogon.com/discussions/quot-fixed-quot-bias-versus-quot-auto-biasing-quot


Another dynaco-type kit source:  http://www.tubes4hifi.com/bob.htm

[mresistor]

That's a really nice amp..  did you get the driver cover for it too?

[Ritchie200]

@Jim:  https://forum.audiogon.com/discussions/quot-fixed-quot-bias-versus-quot-auto-biasing-quot


Another dynaco-type kit source:  http://www.tubes4hifi.com/bob.htm

JJ thanks for that. And that is the site for P2P’s amp. I was just wondering how the auto bias works. It sounds like automatic antenna matching for my Ham radio with servos. I was just wondering how the comparative circuit works?  As someone who does “atmospheric biasing”, I don’t know if I could trust that!!!


Jim

[p2pAmps]

http://www.tubes4hifi.com/bob.htm#ST120

[p2pAmps]

That's a really nice amp..  did you get the driver cover for it too?

Nah, I kinda like staring at those KT120s!   

[jjasilli]

Jim, I'm not sure the guy's right.  Some hi-fi purists opt for a voltage regulated bias supply.  That keeps the bias voltage constant regardless of B+ sag.  This would result in cold bias under strong signal conditions.  So they might also regulate the B+ supply.  This results in a lot of statistical performance claims, but I don't know if there's a real tonal difference.


Some hi-fi purists don't like B+ or bias voltage moving around on principal.  I think they claim it will modulate output power causing a tremolo affect which is not true to the original signal.  Maybe they're technically right???


FWIW I think McIntosh used a more passive feedback circuit to eliminate the need for bias adjustment.

[DummyLoad]

wondering if bob's amp melted down. the one monoblock on the right is not happy in the pic.


--pete