new thread, 6BM8 PP build begins...

[Nanook]

so I've finally found the circuit (ASL AV-8 amp), and power supply (5AR4 tube rectified PS).

I just ordered the parts, less tubes, and iron--$110 USD or so. To my suprize, the capacitors and connectors were where the lion's share of the money went. I figure that with tubes, and a chassis and iron, perhaps $250 USD.

And I'm hoping to have it done for the Vancouver Island DIYfest (July 28). I'll post the build results, schematic and my parts selection for those that may be interested.

morayj will be providing the iron (thanks mr. james ), my friend John will be providing some expertise and some small parts, and pcx for the ordered parts.

Once I get the power amp section working, I want to create a preamp w/phono stage, and internal 3 inputs, so I can have me an intergrated. When functionally complete, I'll start looking at cosmetics.

If any want to chime in please do so. And please, I'm no tube geek, so if you are, please don't ask me a bunch of technical questions. I am sure the tube geeks know way more than I do.

[Nanook]

as no one has shown any interest.

[planet10]

Originally posted by Nanook
so I've finally found the circuit (ASL AV-8 amp),

Can you post the schematic.

dave

[Audio_idiot]

Nook,

If you go for high quality transformers, your total outlay will easily triple in a hurry... So do watch out for what you wish for.

Cheers

[svokke]

I'm also building something like this. I just made a prototype using some scrap transformers and four 6bm8 from the junk box. Output transformer is a hammond 125E.

My layout is voltage gain stage direct coupled to the cathodyne phase splitter. The output stage is class AB penthode with fixed bias.
The power supply is regulated with a string of zeners and a mosfet in "cathode follower" configuration. Unregulated voltage is 300V DC, regulated it is 250V.
I'm looking forward to see your schematic.

[Nanook]

I just figured that with no replies in a day or two, no one was interested.

Dave: I'll attach the schematic... the power supply portion isn't complete (it's a 5AR4 tube rectified one)

I have suitable iron,. original power transformer , original out put transformers, and Moray's old Wav-8 trannys (thanks to morayj--when the mail gets here ).

THe caps and connectors and sovkets cost a little bit of money, and I have looked at the costs of transformers. The goal is to create a tube intergrated with phono stage and one other input, a decent attenuator (Precision Electronics from Toronto), decent power switches. The changes that I have made are the 5AR4 tube rectifier and the inclusion of a couple of Black Gate capacitors (.47 uF) in the inputs to the pentodes.

Some like capacitors prior to the AC chokes, some after. The 5AR4's can tolerate 60uF in the filter. Please have a look. Any comments are welcome. As I have stated several times before, I am no amp guru, so if "too technical" questions, I will divert them to someone else.

Anyone else watch "Little Mosque on the Prairie" last night.?I forgot how lucky we are here in good old canuckland to have some seriously funny tv from the CBC, CTV, Global, and CITY.

[Tom Bavis]

If you're using the Wave 8 power transformer, you'll need a full-wave bridge rectifier. The two diodes in the 5AR4 can form half of that bridge, and two solid-state diodes form the other half. You'll also need a 5V transformer to light the 5AR4 - it needs be isolated from other heaters. The filter must be capacitor input with this transformer, to get enough voltage. The choke should be low-resistance as well, as there isn't a lot of voltage to work with.

[Nanook]

here's a copy of the stock schematic. (not my page)... HERE

[vinylkid58]

Originally posted by Nanook
here's a copy of the stock schematic. (not my page)... HERE

Hi Stew,

I just stumbled on this thread in my search for the ultimate 6BM8 PP amp project/design. Any progress on your build?

Jeff