• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

preamp kit?

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Not so fast, if you please! The power amp and source(s) that will be used impact GREATLY on the choice being made. If a power amp that requires less than 2 V. of drive to reach full power O/P is used in combination with a CDP, the very last thing needed is the gain both a Foreplay and an Aikido provide.

Mr. Carpenter, please tell us what sort of equipment you are going to use in combination with the line stage. Only then, can a good recommendation be made.

BTW, which section of Brooklyn is home? FWIW, I originate from East Flatbush.
 
Commercial CDPs, like those in your possession, can drive the IHF 10 KOhm "standard" load. That allows you to "breadboard" an inexpensive passive setup to test the drive voltage requirements. A pair of low cost 10 KOhm audio taper Carbon pots., from either Mouser or "Rat Shack", are what you need. The ends of the controls get connected to the source "hot" and ground. The wipers drive the power amp "hots". The grounds in each channel are common to CDP, control, and power amp. Keep the wiring between the controls and power amp short or you will get HF rolloff.

If you get satisfactory control over the listening level using the temporary passive setup, you don't need gain in the line stage you build. OTOH, if you find yourself fully advancing the pots. and still not satisfied, a design with gain, like those previously suggested, is in order.

Get the ducks lined up, before you spend hard earned cash.
 
Eli,

With all due respect I do differ in my opinion on gain. With the invention of the volume control was does have the option to adjust the level to suit ones needs. I always hear about too much gain out of a particular line stage but I don't agree because its never caused me a problem.

I have gone the volume control route from the CD player to the amplifier and found it to be ok. It works but I don't find it to be superior but then again its less costly. Depending on ones taste a set of decent pots usually sets me back about $50 and around $200 for stepped controls as I favor individual level controls.

You are correct as Mr. Carpenter could get buy with a Radio Shack dual pot and probably be happy. I felt that he was wanting something in the way of a project and that is what prompted me to suggest the Aikido.

Having built a number of Aikido's and other line stages of interest in the past 6 years or so I felt it was a superior piece demanding ample consideration. I will however acknowledge your considerable experience and knowledge in the field and bow out.
 
Don't want to get in the middle of a war here ;) , but I thought Eli was just asking Mr Carpenter to perform a simple experiment to work out how much gain is required before recommending an option/opinion on pre amp. I don't think he was suggesting he use a rat shack pot as a replacement for a pre-amp.
 
My Sony ES CDP has variable out and a 2v outputs, so I've been driving the Amplifier with Variable out and gotten away with it pretty good. Now I want to see if by replacing “el cheapo “ output stage of the CDP with a tube preamp would improve things. Plus, I just want to make one for the hell of it. As Fingers said, “ I want the project” and he's quite rite.
I like the warm glow of tubes on a cold winter night.
 
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If you are in it of the fun of building and owning, rather than trying to beat the world with your own technical design, then the Foreplay would be a good choice.

Nearly everything on the foreplay fits onto a single top panel, and with your woodworking skills you could knock-up a superb base for it.
 
Hi Carpenter.

Yes, as you can see there are many different opinions regarding a line stage with amplification or a line stage as a buffer.

With the Aikido you will have a lot of different tubes / set-ups to play with. Of course, the Aikido will give you some (unnecessary?) amplification as Eli D correctly wrote.

Some people prefer a 100 % passive line stage. However, the times I have heard a passive line stage it has been a bit "dull" and uninvolving (lack of dynamics???).

If you are looking for a (tube) buffer there are quite a few to choose from. Personally, I would go for SY´s "Heretical preamp" construction - even though I haven´t heard it yet.

This construction looks very promising, I think, and you have the possibility to use the input transformer to change the absolute polarity (phase) 180 degrees (if you think this matters?!). You can find a very detailed description of SY´s pre-amp at: www.SYclotron.com

Kind regards

Karsten
 
Karsten Sømand said:
Some people prefer a 100 % passive line stage. However, the times I have heard a passive line stage it has been a bit "dull" and uninvolving (lack of dynamics???).
In that type of passive line stage, the signal level is reduced proportionately. Correct me if I'm wrong but if an active line stage produces different sound characteristics, then it's altering the signal besides just increasing the output level, isn't it? For the purest (if there are any), that can't be a good thing since neutrality is diminished. Am I looking at it the right way?
 
R-Carpenter said:
My Sony ES CDP has variable out and a 2v outputs, so I've been driving the Amplifier with Variable out and gotten away with it pretty good. Now I want to see if by replacing “el cheapo “ output stage of the CDP with a tube preamp would improve things. Plus, I just want to make one for the hell of it. As Fingers said, “ I want the project” and he's quite rite.
I like the warm glow of tubes on a cold winter night.


Dude,

Chris hit the nail squarely. I suggested the cheapy passive only as a way to determine the proper gain structure for your system. You WILL build a tubed preamp. :D

Right now, the leading contenders are a "unity" gain buffered volume control and a line stage with a small amount of gain. Would you kindly check your CDP's documentation and determine what the voltage range on the variable O/P is. If it never goes above 2 VRMS, you need a buffered setup. OTOH, if the variable O/P does go above 2 V., a low gain line stage may be needed. Either way, the substantial gain associated with the Aikido and Foreplay designs is not a good idea. You will end up with the notorious "hair trigger" volume control. :(

IMO, "breadboarding" the cheapy passive remains a good idea, as the correct gain structure can be determined, with certainty.
 
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Evenharmonics said:

In that type of passive line stage, the signal level is reduced proportionately. Correct me if I'm wrong but if an active line stage produces different sound characteristics, then it's altering the signal besides just increasing the output level, isn't it? For the purest (if there are any), that can't be a good thing since neutrality is diminished. Am I looking at it the right way?

You are looking at it the right way. However, keep in mind that passives can also have issues... poor connectors, poor grounding, poor potentiometer left / right tracking, high and variable output impedance, etc., etc.. So they are often a viable way to do things, but not automatically blameless!

: )
 
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