TerrySmith wrote:I never was really satisfied with the PAS phono stage, even with the curcio mods, so I repopulated an old board as per the circuit in the RCA tube manual as it's almost the same. Tubes are 6N2P-EV, eqiv to 6AX7.
The sound is much fuller, NO HUM, and the output level is a lot closer to other line inputs so I don't have to crank the volume way up.
Hello Terry,
This sounds very interesting. Which RCA book? I have several tube manuals. Hmmm, I think I packed them up for my move. Is the schematic posted on line? Is it similar to the one EWBrown posted? I would like to examine it in relation to the original circuit.
To tell you the truth I have not heard a 'stock' PAS in a very long time. Perhaps in my teens was the last time. The two PAS pre-amps I have are the original circuit and out side of some basic tests, I have not done much listening to them. The PAS-2 I have that I want to modify doesn't have a working phono section and the line stage area was recapped and some minor mods were made, but not much.
I didn't want to stick with the 'stock' PAS because of all the complaints I heard about it. I just about heard all the issues with the tone control circuit and also the poor power supply.
In terms of the work involved, I don't mind redoing the entire chassis if I have to...if it keeps me from spending the money on a new custom chassis (which is something I can't afford right now).
Slartibartfast wrote:jukingeo wrote:
Speaking of music from the 50s, take Elvis recording at Sun Records for instance. They had at most a two channel board, so that meant two mics for him and the musicians. There is not much to work with, even with tone controls.
Sun Records used an Ampex 350 for mastering which was one of the best recording machines at that time. Most Elvis recordings are very good. However one of my favorite Elvis songs, "A Big Hunk Of Love" falls into the same category of Gimme Shelter. It is just a terrible mess. Mids and Highs are thin and the guitar and vocals are peaky. Now "Teddy Bear", which was done a year EARLIER, sounds good and more balanced.Now your Stones example, when I said I would not listen to it, I meant I would look for a different recording of that song. This is easier to do for music of the late 60s and beyond.
Gimme Shelter wasn't remastered as far as I know, so the only 'better' recordings are usually the live versions. As for my Elvis example, "A Big Hunk of Love" was remastered, but I don't like it. The original 'performance', was better.For critical listening in the late 50s I limit my selection to Jazz. Most of the music I like is 60s and beyond.
As I pointed out earlier, my wide range of music contains the inherit problem of having varied quality recordings.
So I have songs as poor quality as the aforementioned Elvis and Stones songs, all the way through the wonderful works of Pink Floyd and Rush (no one can argue the high quality recordings these bands produce), all the way through dance music of the early 80's and 90's.
But the time you get to club music of the 90's, the quality gets very inconsistent. You have many indy labels and there are many people producing good pieces of work, and yet really shouldn't be behind a mixing console. The end result is a good song that was recorded poorly.
So yeah, I sure can see if you limit yourself to only well made recordings, and have only certain genres that you do critical listening with, then once you get a setup you are happy with AND you have a good room for your sound system, then I would agree that you probably wouldn't need tone controls. But unfortunately I am very far from an 'ideal' situation. So tone controls will help me out a bit.TerrySmith wrote:Here are some pics of my modded PAS3. It has slight hum in the linestage, most likely because of my wiring. There are no tone, filter, loudness, etc circuits, just a barebone linestage. Tubes in the linestage are 7AU7's.
PS: I'm trying out my new camera, whaddayou think?
Very nice indeed! It looks like you greatly simplified both the line AND phono sections. Are you using NFB at all?
If I could do something THAT simple but WITH tone controls, I would be a happy camper. Camera looks good to me!nyazzip wrote:sorry for stirring up a hornets nest gentlemen. i can be a bit opinionated at times, and indeed i am not qualified to comment on virtually most of the things i do comment on.
I can be too, but I for one DO NOT like it when a post gets out of hand with 'bantering' and then you get the 'trolls' that come along and do nothing but start beating that 'hornets nest' further.
Anyway, I don't think it is out of hand by a long shot. I do know that there are many that prefer a very simple no tone control set up. Originally I did agree with that. Heck, I even did build a no tone control pre-amp. I got bored with it right away too and added that loudness circuit. I guess I am not a purist as I thought I would be. Sure I do still like to keep my circuits simple. But for now it is just the nature of the beast that I prefer something with tone controls...no matter how 'purist politically incorrect' it may be. I just think that I know because of my fixed room location and the varied quality of my recordings, I will be needing to do a bit of tweaking here and there.nevertheless, it is entertaining.
So is putting pure sodium in a vat of water and watching what happens.back to the thesis of: dynaco PAS mods which retain the tone control circuitry.
i too own a PAS 2, and one channel of the phono section is seemingly weak, and the balance pot is crap, thus i also dream about some mods some day.
for me step one is that selenium rectifier Yellow_Light_Colorz_PDT_09
cheers
I had a problem like that with a pre-amp I was working on for someone else. Recapped the darn thing and everything. But the guy insisted on keeping his NOS Mullard tubes. However, that therein was where the problem lied. One section in one tube was not fully amplifying, of which I found by swapping the tubes (seeming late in the game when it was something I should have done FIRST). The point is...just make sure you don't have a bad tube. If your PAS isn't rebuilt yet, you may have a leaking cap or way out of tolerance resistor floating around somewhere in the stage.
Geo