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Old 7th May 2002, 01:44 AM   #1
RMS is offline RMS  United States
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Question Input signals and my amp

I just got done building a small tube power amp and I want to buy a CD player for it, some say digitial output some say analog I'm thinking only a analog signal will be compatable with my tube amp, does the type of signal output matter?

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Old 7th May 2002, 02:23 AM   #2
PassFan is offline PassFan  United States
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RMS:
Not sure what you mean by digital output. Your tube amp, unless it has a printed circuit card inside with the tiniest devices you have ever seen on it, will only accept analog signal. I'm not sure about your input sensitivity though. Most of my tube amps have an input sensitivity of 1.5 to 1.7 volts. This is the required input voltage to drive the amp to it's rated output. Most analog outs on cd players will drive close to 1 volt of output by themselves. This is why some refer to them as a line level source. A preamp will allow you to make up the difference for rated output of the amp. If you want to play cd's why not get a mid grade dvd. The converter chips have a higher bit rate allowing them to outperform most consumer grade cd players. They sound a lot better. The one I use only cost me 175.00 . It will hold you over until you learn a little more about digital outputs and how much a setup like that will run you (if I understand it correctly, what is being referred to is a seperate converter and cd deck which can get expensive) Good luck and I hope you enjoy your tube amp. I am glad I made the switch
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Old 7th May 2002, 05:01 PM   #3
RMS is offline RMS  United States
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Default signal out or in....

Hey Skippy, thanks for the reply, I think I understand things better now. What I need is a CD player so like you said maybe a CD/DVD. Now, The Power amp I made has a one stage 12AX7, and a single ended EL84 (just one) using a 25 watt tranny plenty loud drives a 12 speaker good. What that has for a input sensitivity I don't know but it plays my old cheap tape deck fine.

What I mean about (digitial output) is this, when I was shoping for that CD player, in the back where the RCA output jacks are some said digitial others had both digitial or analog output RCA jacks. My tube power amp that I made is point to point. What type of CD deck will this be compatable with, I think you did answear that and if I understand you right it was Analog. Can I get this CD/DVD in Analog or does that converter chip you mention take care of that??

Thanks,
Rob
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Old 7th May 2002, 05:22 PM   #4
PassFan is offline PassFan  United States
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To answer your question. You want a player with rca outputs for analog. Any player with rca outs for analog will have the converter inside. You can't get from digital (binary 1s and 0s) to analog (voltage) without it.

There are a few protocols for digital, rca (spidif), optical (toslink) and xlr (aes/ebu). I'm a little rusty on these and I know if I made a mistake there I will surely be corrected, but you get my drift. The thing about digital is you have to convert to or from an analog signal. In the case of your amp, convert from digital. Any cd/dvd you buy from sears or best buy or circuit city will do this so you just plug it up and go. Some of the posts in the digital forumn have probably covered some of this stuff though I tend not to go there as my interests lie elswhere (most of it is over my head anyway and their stuff is too tiny for me to solder) Enjoy
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Old 7th May 2002, 06:19 PM   #5
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I take it your amp is stereo or you have mono blocks. There is enough voltage coming from a CD or CD/DVD player for a 12AX7 to amplify the signal enough to drive an EL84 fine enough to get 3 watts. Put a 1 meg taper pot in and you don't need a preamp. Use a 12AY7 and you can get more gain though I am sure your EL84 will still break up before your speaker does. If you get a CD/DVD player make sure before you leave the store that it is set for 2 channel analog audio since it has to be hooked up to a TV to verify the setting. Basically only high$$ CD transports don't have a DAC (digital-analog-converter) built in. I use a CD/DVD player and use anolog even for the movies as this allows me to use any kind of amps I want and not have to spend a chunk of change on a throw away reciever paying for options I will never use and that's only use if it breaks down would be for a door stop. Besides that I did get one and it sounded like crap so I took it back.
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Old 8th May 2002, 12:45 AM   #6
RMS is offline RMS  United States
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Thanks Skippy, and Dave for the info it is greatly appreciated.

Rob
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Old 19th July 2002, 08:42 PM   #7
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Default your amp?

Hi Rob!

Just wondering about your amp--I am researching amp designs and schematics to build my first. I have been advised to start with a EL 84, SET design and yours sounded like it fit the bill.

For myself and other readers, if you haven't already, will you provide a brief description of your amp and comment on its performance, please.

Thanks much,
Rick
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