Thanks for the info Greg. That's a big help.

On a side note, since you'd mentioned Newark, I have to voice my strong approval of that company. They have nearly everything you could ever need, their web site and catalog are great, and they have your stuff to you in 2 days. I really couldn't imagine a much better component supplier. I definitely recommend them to my fellow DIYers.

My experience with Digi-Key has been less satisfactory. They took a relatively long time to deliver my stuff and, when it did arrive, the packaging wasn't nearly as nice as Newark's. For instance, Digi-Key simply throws the components you ordered into clear plastic bags with few, if any, identifying labels. On the other hand, Newark lovingly places each different type of component in sturdy little boxes which are explicitly labeled. That goes for even the smallest number of components. Say you were to order one resister: You would get one individual box for it. Now that's what I call attention to detail, concern for product safety, and caring for the customer.

So, my recommendation is to buy all of your components from Newark and only use another company if Newark doesn't carry a certain item.

Good luck everybody...

I agree they are definitely pro with their business. They are a little more expensive than say Allied or Mouser but I think that care is what you are paying for. When they had a will call in the ghetto we would order from there more often. It was convenient to have a same day, in town supplier.

HEY!
There are corrections I need to post for the schematic. Eventually I'll draw a new schematic but these are the ones I've found.
R55- is 6.8k instead of 1.5k
R58- is a 20k instead of 15k
No tubes use the 12.6V AC for their filaments. They only use the 12.6 V DC.

Sorry for the problems this may have caused. I'll try to keep updating as I learn more.

Here are some photos of the inside of our modified Ampex 351s
http://www.electrical.com/~greg/351-photos/

greg wrote:Do any of you have an opinion? Pot or Switches?
Keep in mind the output attenuator being like a fader.
I'm thinking for the switch having 12 to 16 positions. The first being "Off" then having gain stages of 5dB.

I built some preamps recently with 12 way switches in. I like them a lot. I'd recommend it, definitely.

Just how 'coloured' are these pre's? The ones I built myself are super clean, so my next order of business is probably something with a bit more character.

Hey Everyone,

I've finished the 351 mod and am trying to get it to work. The problem is, the rectifier tube is glowing much brighter than it should and I'm getting highly elevated B+ voltage readings. For example, I'm getting about 370V going into R6. Does anybody know what could be wrong? I've checked the values of the resisters and they're all correct. Capacitors seem fine as well.

Thanks.

Dan

greg wrote:Here is a list of corrections to the schematic-
R55- is 6.8k instead of 1.5k
R58- is a 20k instead of 15k
R49- does exhist and it should be replaced with a 39k resistor (this resistor is in between pin 3 of V4 and Red/Yel connection on the middle board.
No tubes use the 12.6V AC for their filaments. They only use the 12.6 V DC.
The attenuator is not a Davin but a Daven.

Also: The "gentile rise" in frequency response mentioned in the penultimate paragraph of Greg's introductory note should probably be a "gentle rise."

Unless he's making some sort of joke about Christian erections.

Hey there,
How easily would it be to convert these to Australian 240v power?
Im considering modding 2 of these...
thanks

Sorry if this has been asked already but I am a bit confused.
In the list of equipment you said to have a bunch of Ampex 351 but when reading the description you said that you bought a bunch of 350.
What are they 350 or 351 ?
Thanks
Alex