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Re: Steve Brown and I are working on this amp [message #31959 is a reply to message #31958] Wed, 13 September 2006 14:07 Go to previous messageGo to next message
Damir is currently offline  Damir
Messages: 1005
Registered: May 2009
Illuminati (2nd Degree)
Direct coupling has a large advantages - omiting of the coupling cap and grid choke, driver "sees" very high impedance of the output tube grid as a load, etc. Less safe and large B+ are "drawbacks"...
I considered similar circuit ("classic" SE, not parafeed), 2A3 (AD1, etc.) direct-coupled with CCS-ed 6SN7 as a driver. With convential OP (250V/-45V/60mA) input sensitivity is about 1,5Vrms...but, B+ is about 550V.
Probably, sonic "plus" gained with omitting cap/grid choke combo is a large enough to accept high voltage...just a few thoughts.

Anyway, keep us posted about your progress, seems like a interesting amp/circuit. Is the driver paralleled ECC81?


Re: Steve Brown and I are working on this amp [message #31960 is a reply to message #31958] Wed, 13 September 2006 17:51 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Hey-Hey!!!,
Nice looking project. Do watch out for Iron-Iron coupling with that many pieces. I have simplified some of my designs by putting all the power and filament in the same direction, and all the signal in the other. The para-feed makes things a bit mroe interesting, 'cause it is working in the same phase, yet still needs to be seperate.

Let us know how it works.
cheers,
Douglas

Re: Ohm Sweet Ohm [message #31961 is a reply to message #31949] Wed, 13 September 2006 22:44 Go to previous messageGo to next message
Forty2wo is currently offline  Forty2wo
Messages: 163
Registered: May 2009
Master
Finaly going on the 6a5 P-P project...John

Ah there we go [message #31962 is a reply to message #31961] Wed, 13 September 2006 22:47 Go to previous messageGo to next message
Forty2wo is currently offline  Forty2wo
Messages: 163
Registered: May 2009
Master

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Re: Ohm Sweet Ohm [message #31963 is a reply to message #31957] Thu, 14 September 2006 00:23 Go to previous messageGo to next message
Forty2wo is currently offline  Forty2wo
Messages: 163
Registered: May 2009
Master

Hi M,

I am listening mostly to the recent D3a, 300B amps.( note to Damir I tired 6688 and E180 and the d3a is the clear winner in my application . Will try the C3~ if I come across any )

Next up is a P-P amp 6a5’s (in the 2A3 family). I had almost decided to go with Douglas’s Galahad front end, and that is the fallback plan, if this doesn’t work out.

But I got to thinking, I like my Aikido line stage. So with a bit more gain… then I acquired a set of transformer phase spliters. Well we’ll see.

As to chassie, I love a good found object. Or if I have really settled on something, then it’s time to move it into a finished form but for me this rarely happens. I have a very nice set of wood boxes (found ) that the DRD45 will move into one day. In the mean time I use cakepans as a half way between naked breadboard and finish amp.

They cost $6, are very easy to cut/drill, keep the HT mostly under and if you use a little care, look somewhat respectable. When faced with $110 of nice chassie, you have to measure to the last mm. With a found object, lay it down and drill it, if you screw up, well it’s off to Hellmart with another $6.

I find that the separating the "let’s be real careful with the inlay" allows me to do a better design and layout.

It’s late I will get to your other questions later…John


Re: Ah there we go [message #31964 is a reply to message #31962] Thu, 14 September 2006 09:36 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Wow; that is some kind of fine. A cake pan; perfect. I saw that done in an old Sound Practices mag and it's a great solution to exorbitant priced enclosures; and... comes with handles!. Is there good room inside for making changes to the circuit and such?

Re: Ohm Sweet Ohm [message #31965 is a reply to message #31963] Thu, 14 September 2006 09:45 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Man; I love to see practicle use of ordinary stuff as chassis and enclosure duties. That way stuff gets built instead of dreamed. And I find that people get more involved with the sound of the unit and less worried about what it looks like.
I just picked up the three way pots from Broskie for the Akido LS. They are on sale for 29$.
Thanks for the cake pan remminder. How are you finding the prices of the big triodes lately? They seem to be rising.


Re: Ah there we go [message #31984 is a reply to message #31964] Sun, 17 September 2006 21:06 Go to previous message
Forty2wo is currently offline  Forty2wo
Messages: 163
Registered: May 2009
Master
This is actually a broiler pan. I needed the much heavier steel, to support the unusually large iron load, 18# for the PS trans alone.

The down side is they are harder to work. I am still using a hole saw to cut the tube sockets. A 1 1/8" will go through a cakepan like cheese. With the broiler pan, I needed cutting oil and time.

The upside, they are 3" deep and damn near bullet proof…John


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