• 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.

Vintage tube preamp design

purejaqzz

Member
2014-11-19 10:33 pm
I was on youtube looking around when I came across a preamp that was made by a guy in Brooklyn named Mr SO , it started me thinking that I would like to build a nice vintage preamp that's close to what he has there on youtube . Dose anyone here have a good schematic of a good preamp that would have good sonic qualities and low noise . If anyone can help or point me in the right direction I would like that thanks.
 
I completely agree with DF96 that preamps are usually completely unnecessary. They are however in my opinion a lower threshold entry into DIY than a power or integrated amp is.

purejaqzz you should have linked the video in question. If I got it right, it seems to be a 26 single ended with probably both input and output transformers.

The 26 is not at all for beginners. For similar aesthetics, I'd suggest the 27 (still affordable in globe envelope). The 26 is directly heated, and the 27 is inderectly heated. Directly heated tubes require much more in terms of added electronics complexity and mechanic build quality.
 
DF96 and IceFyre both have valid points.

If one were to just take practical solutions for something like "I want to ride a bicycle", then there are hundreds of pre-made brands and thousands of models to choose from. Done, ready to ride. Finite cost, even more finite 'work' investment.

Or… one could muse, “But I want to build a bike from scratch!”. Learn about the scores of tubing choices, about milling metals, joinery, tolerances. Maybe buy a MIG welder, and rent some space at a local DIY machine shop for a few months. When I was in my 20s, I did just this. And yes, while there were still dinosaurs cavorting about Berkeley's Telegraph Avenue, there were also dozens of manufacturers, and hundreds of models. I did not need to make a bike.

So… if you want to get your feet wet making a preamp, then make a preamp. If you want one that materially impacts (changes) the sound, then build a tube preamp. If you want to live to tell your grandchildren about it, then build a preamp having "low" high voltage. Save the really high-voltage preamp for version 3.0. AND… unless absolutely necessary, keep your test probes OUT of the amp during operation. Your grandkids will appreciate it.

GoatGuy
 
Did somebody say preamp? :D Read this thread.

The comments about few power amps needing a line stage with gain are, for the most part, correct. Modern digital sources, with their 2 VRMS signal level can drive many (most?) amps into clipping, without any additional gain.

A nice thing about the 12B4 is its low amplification factor (μ). If a so called "hair trigger" volume control occurs, correction is easy. BTW, the μ of the 12B4 is < than that of the #27, which is advantageous in this particular situation. The 12B4 will be quieter, too.
 

purejaqzz

Member
2014-11-19 10:33 pm
Well I thank all for their input , I should start by saying that I have some old RCA tube amps that I use with other vintage audio gear . I was using a Marantz 33 as the preamp with some success , however I wanted to get a cleaner sound so I figured I would go with a tube preamp . I looked around and saw some the were fine or that they state that they were good at producing great sound , this may or may not be true so I figured I would try my hand at trying to build something nice .
That said here I am asking and looking for a good set of plans for one as well as suggestions .
 

purejaqzz

Member
2014-11-19 10:33 pm
The video of the 26 preamp is the one I saw , my system is passive . With the Marantz 33 I was able to control the bass and treble which in my case was good , I just felt I could get a better sound that's why I opted to try a tube preamp , anyone know of a really good multi stage low noise preamp that could work for HIFI ???? :confused:
 
purejaqzz,

A look at the Marantz 33 front panel shows the presence of a critical feature, tone control defeat. Few recordings benefit from tone controls. Getting the signal shaping circuitry completely out of the signal path, when it's are not needed (most of the time), contributes to overall system performance.

I've uploaded a Max Robinson design for "unity" gain Baxandall style tone controls. "Unity" gain makes for easy circuitry defeat. A down side to the setup is the need of 2X 12AX7s, for each channel. The bottle count can be reduced to 1/channel by using ZVN0545A MOSFETs, in the voltage follower positions.

I strongly suggest that a beginning DIYer, such as yourself, start with a "simple" line stage and get some experience under your belt. Tackle "bells and whistles", after some experience has been acquired.
 

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purejaqzz

Member
2014-11-19 10:33 pm
while it is true that I have no experience with tube preamps , I have worked on all power amps , I am not a total strange to tube gear , but I think with some guidance I could do ok , that and I have a friend that's pretty savvy with most of this type of stuff. One of the biggest reason for building is that I have a few vintage transformers and some chokes that I am doing nothing with so if I can use them I would like to . Any other schematics would be welcomed , just want to get an idea of whats out there that people have used with good results .
 
I used a 6sn7 in srpp with a 6v6pp amp with good results. It's not fancy but then again it didn't have to be. I feed it with a 6n23p passive phono preamp that I built and it sounds great.

There are some drawbacks to using srpp but I wanted something that would use one octal socket for reasons of space as I was replacing another preamp design. It fit the bill quite well. You can build it on a socket so testing it out will be easy.
 

purejaqzz

Member
2014-11-19 10:33 pm
Well I have narrowed it down to two different 2 channel tube preamps that seem to be ok , A 27 preamp is my first pick . I would like to get a good working 27 preamp with the following items , oc3 , tube rectifier and choke in power supply section , hopefully this will be ok , in addition a schematic of the preamp section as well I have some NOS transformers that I would like to use up on either build . My second choice is a 6sn7 tube pre amp , as in my first choice I would like to use all the same items in the power section again because it is what I have , and also a good working schematic for preamp 6sn7. These preamps are going to be both line preamps but if the schematic has phono I will just take that as well also , hopefully someone will have something that I can use , thanks .