|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
66.87.114.46
In Reply to: RE: My bad posted by Lew on August 27, 2013 at 07:50:43
Thanks Lew.
On this change no I didnt talk to Mr Rosenblitt.
The idea came partly because i wanted monoblocks and i hated wasting 1/2 of an ax7.
I wanted to keep the tube type for the front end a common type.
Talking to my bud Joe, we thought a diff amp
So Joe designed a circuit that would drop in basically.
All i needed was to tap into the bias to get the -300.
I had to lower the b+\b- to i think 115 to maximise output tube life.
10 years on this set.
Bob
Bob
Changed my moniker from my email address to my usual forum name. I usually hang out over at AK. The reason I changed my moniker is....Too many friends email accounts being hacked.
Thanks bob
Follow Ups:
If I had to guess, there seem to be other differences too. I'm pretty sure Bruce shuns the 6AS7G.
Hello
Yes there are a few differences, I built these amps 10-12 years ago.
I took Rozenblits article and added my own ideas.
I wanted mono blocks, separate the transformer load and shared tubes. and to make them as reliable (low heat) as possible. Each transformer is fused, inrush limiter for a soft start.
The first few attempts at getting them up and going I used 6080 tubes and lost a few, then changed to 6AS7's still loosing a few.
The tubes would arc easily, To solve the problem I lowered the B+/B-, I think to 115-120v after that no tube loss.
The tube line up stayed the same for quite a while, 6J5 is 1/2 a 6SN7 so that was the perfect candidate for the driver.
Then talking with my friend Joe, we thought what about a diff for the first stage, joe designed the circuit and that change was done later.
The only thing I can say is the amps are reliable, I dont have any problems, hell im still running the same tubes after 10 years.
They will run a 4 ohm speaker load but that is stressful, much better running 8 or 16.
I like the 6AS7, Atma Sphere uses this tube with killer results,
I don't think reliability is an issue.
Rozenblit uses the EL509, In his book,the comment about this choice is it dosen't arc. Im thinking because the b+b- is too high, that was my experience.
I like Atma Sphere's Circlotron, I actually heard the Electro Voice version years ago. neat amplifier.
Im wondering maybe build another OTL, choice.. build a circlotron I have a stash of old 6AS7's and have seen clones of the Atmasphere or Rozenblits design, but EL509's are pretty pricey,
My OTL is a neat amplifier, it has an ease to the sound and detail that is spooky, It plays music. Living with musicians in the house, they say the same thing.
bob
Bob
Changed my moniker from my email address to my usual forum name. I usually hang out over at AK. The reason I changed my moniker is....Too many friends email accounts being hacked.
Thanks bob
To be honest, Ill have to take the bottom plates off and have a good look.
I should update my photo album and schematics, There were changes made in the first year after building them, nothing since. Someone may want to build their own version. One thing I can say is RCA coke bottle 6AS7's seemed to be the best.
Maybe one day Ill find a pair of Atma-Sphere M-60 Mk II's I love the looks.
What can I say.
bob
Bob
Changed my moniker from my email address to my usual forum name. I usually hang out over at AK. The reason I changed my moniker is....Too many friends email accounts being hacked.
Thanks bob
From the photos you kept it nice and clean.
If I can offer a suggestion, you might want to consider installing cathode resistors for each tube section in the output. At least 2 ohms, no more than 5 ohms, with 5-watt dissipation would be a good idea. This will get you better current sharing between sections and will result in lower distortion, lower output impedance and longer tube life.
Ralph
Thanks for the tip, It makes sense to stand the cathodes on resistors.
I have a couple really good surplus houses close by, they usually have a ton of good wirewounds, many 1%.
Thanks
bob
Bob
Changed my moniker from my email address to my usual forum name. I usually hang out over at AK. The reason I changed my moniker is....Too many friends email accounts being hacked.
Thanks bob
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: