New Build time- AO43

[dunner84]

New build time... I just did an inventory of all the spare parts I have been collecting, and I want to put my AO43 chassis to use. It is going to be a Dumble inspired build which translates to an ODS preamp (haven't decided which yet), and I really like the idea of a diode rec, tightly filtered, cathode biased, el84 power section. I have done some reading through previous ao43 builds, and it seems the transformer is a bit hot for el84s. Mine measures 315-0-315 unloaded. With a solidstate rectifier what kind of plate voltage would I expect?

I have a PT from an S6 organ that is 290-0-290 on paper, but measures 325-0-325 unloaded.. I have a wack of 350-0-350 PTs which are all probably too much, and one from a viking radio that measures 290-0-290. I have little experience with el84 amps, so I am not really sure what they will tolerate...
One other question for anyone with AO43 experience. Ch301 I believe is a 14H choke, but it seems a bit on the small side. I have a rather large choke that measures around 160Ohms, but I don't have any other info. It looks a lot like a Baldwin choke I have used in the past, and even has the B512 prefix, but the suffix doesn't turn up anything on the interweb.. I also don't have access to a sig gen or O-scope right now to determine the inductance. That being said, is the smaller Hammond choke usable for a build like this?

I am also not set on el84.. I will go with 6v6 if I have to, but I would really like the idea of el84s...

Concurrently, I will be building another Masco ME-18, but I will start another thread for it.

Any input would be greatly appreciated

[tubenit]

I would NOT recommend EL84's with a D-inspired preamp. I think you may end up with a harsh sounding amp,IMO.

Layout is super important in the D-inspired amps.

Most dumblish inspired amps get their OD from the preamp.  Most EL84 amps that I know of get much of their OD from the power amp & EL84 tubes themselves.  I heard a sound clip from a forum members years ago that combined those dynamics & I did not care for the tone.  It did not sound dumblish to me.  This was an experienced builder with lots of success in other amp designs.

I think you "should" build what you want, just offering food for thought. 


It sure would be easier to offer thoughts IF you had posted a schematic.

With respect, Tubenit

[dunner84]

I can totally appreciate that. Some of my favorite Kingsley amps are dumble inspired, el84 amps though, and I have the itch to try.
For me, this is a hobby, and each build is a new learning experience. If I have the right iron for el84, I will go that direction, and if it doesn't sound right, it's not a big deal for me to mod the circuit, and chassis to go 6v6.

[shooter]

here's an el84 based amp for study.

I like 84's, they drive easy, usually work well together, old ones you wanna keep plate reasonably close to 300vdc, modern ones I believe get abused to 400vdc a lot.

take your time, enjoy the challenge

[tubenit]

Some of my favorite Kingsley amps are dumble inspired, el84 amps though

I've been very impressed with the videos I've seen of the Kingsley amps.  However, I am not aware of a dumble inspired one that uses EL84's?   

Which one are you referring to?     http://kingsleyamplifiers.com/products/amps/61/

I see some that are EL84 amps but nothing referencing those as dumble inspired?

I noticed that the HiWatt has 47k resistors to ground after the phase invertor.  Perhaps that idea would work with a d-inspired EL84 amp?

With respect, Tubenit