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Have you used tube preamps for recording acoustic and classical music ?
Old 5th November 2021 | Show parent
  #151
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🎧 5 years
Any thoughts on the two 12AX7 gain stages with feedback used in the Pultec MB1?
Old 5th November 2021 | Show parent
  #152
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kludgeaudio's Avatar
 
Quote:
Originally Posted by dseetoo ➡️
I was thinking about using twin triodes as two amplifying stages and use another active device to form current source. Need much higher B+ voltage if tubes are used to form current source. Solid-state devices work great as current source, a hint.
THAT IS CHEATING!
--scott
Old 5th November 2021 | Show parent
  #153
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kludgeaudio's Avatar
 
Quote:
Originally Posted by M50k ➡️
Any thoughts on the two 12AX7 gain stages with feedback used in the Pultec MB1?
That's another attempt to split the gain among two stages so you can run them with reasonable linearity but not run into noise problems. You could make things cleaner than that, but given the output stage and the input transformer colorations, you probably wouldn't affect the sound any if you did. The input stage is pretty much blameless given the environment that it's in.

Today we can get much cleaner input transformers, we can get frame grid tubes that are quieter and more linear than 12AX7s, and even when that design was made you could get a bigger tube with more current drive than the 12AU7 for that output follower. We could add a tertiary feedback winding to that output transformer, get the transformer inside a feedback loop, and reduce that distortion too. Given all these things, the input stage is the least thing that I'd put more engineering effort into.

The Pultec was an excellent design given what was available at the time and what the demands of the market were. It was designed to be as clean as possible, but today what people like about it is the coloration. Go figure. It's a weird world.
--scott
Old 5th November 2021
  #154
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Piedpiper's Avatar
 
1 Review written
🎧 10 years
I've often wanted a lower gain tube preamp since I'm often throwing away a lot of volume in the input attenuator of my Manley preamp since I prefer not to use too much negative feedback in the gain stage. Many sources into a condenser mic don't need more than 20 or 30 dB of gain to get them in the door.
Old 7th November 2021 | Show parent
  #155
Gear Head
 
I think I accidentally deleted my last couple of posts when I was just trying to delete the very last post.

Jim Moss


Quote:
Originally Posted by Piedpiper ➡️
I've often wanted a lower gain tube preamp since I'm often throwing away a lot of volume in the input attenuator of my Manley preamp since I prefer not to use too much negative feedback in the gain stage. Many sources into a condenser mic don't need more than 20 or 30 dB of gain to get them in the door.
Old 7th November 2021 | Show parent
  #156
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🎧 10 years
Quote:
Originally Posted by JMoss1 ➡️
I think I accidentally deleted my last couple of posts when I was just trying to delete the very last post.

Jim Moss
Swift and decisive moderation in response to forum rule violations can have the same appearance as deletions by self....
Old 7th November 2021 | Show parent
  #157
Gear Head
 
Doesn't the moderator tell you when that happened?
I did try to delete a comment, but I don't know that it works that well.
I thought my post was right on target in addressing the person's comment.



Quote:
Originally Posted by studer58 ➡️
Swift and decisive moderation in response to forum rule violations can have the same appearance as deletions by self....
Old 7th November 2021 | Show parent
  #158
Lives for gear
 
🎧 10 years
I've seen some deletions by moderators where they've added a short explanation of the reason ( eg political content, personal abuse, promotion of commercial interest, etc), and others where posts have simply disappeared. The moderator retains the right to shape the entire thread as it evolves, including retrospective deletion without obligatory justification or announcement.
Old 7th November 2021 | Show parent
  #159
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Piedpiper's Avatar
 
1 Review written
🎧 10 years
Quote:
Originally Posted by JMoss1 ➡️
I think I accidentally deleted my last couple of posts when I was just trying to delete the very last post.

Jim Moss
I saw and appreciated it before it was deleted. It's always interesting to me to hear a designer's insights.
Old 7th November 2021 | Show parent
  #160
Gear Head
 
Thanks. You are motivated by similar things as I was. I just could not find them on the open market. I mean, some of these preamps you could overdrive them and it made no difference. The problem is that they used too much Neg Feedback. This also has a sound. To me it sounds confined and constricted. That is why I made it an option. (Side note: VOX AC amps had no Neg Feedback) The so called "Tube Sound" is often a function of overdrive. That is where your second harmonics come in and the sound gets bigger and warmer. Just depends on what you are looking for. I needed to no over drive on guitars and overdrive on lead instruments like Violins and voices. I use one over the other so there is separation.

https://www.jensen-transformers.com/...rs-Chapter.pdf

Jim Moss


Quote:
Originally Posted by Piedpiper ➡️
I saw and appreciated it before it was deleted. It's always interesting to me to hear a designer's insights.
Old 2 weeks ago | Show parent
  #161
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Mr.big's Avatar
Quote:
Originally Posted by ISedlacek ➡️
So I have received the tube preamp Sonicfarm XCalibur (that has an identical tube preamp section as Creamer Plus that I was originally thinking about) https://sonicfarm.com/xcalibur-saturation-preamp/

They had it for review in S.O.S so it was easy and quick to get. Based on all the descriptions etc. I looked forward very much to it and was anticipating beautiful big and sweet sound for some acoustic instruments and vocals.

I was trying it the whole afternoon today and comparing to my Forssell SMP-2 (with Schoeps MK2 and Josephson C700S) and BAE 1073 (on vocals - with U47). It has quite complicated interface with many settings (I did not use saturation), but in the end the sound is quite similar ...

I tried it on melodic percussions, violin, classical guitar and flute (compared to Forssell) and then on vocals and spoken word (compared to BAE 1073).

Well, my enthusiasm decreased quite quickly and unexpectedly ... On all the instruments (comparing to Forssell) the sound was rather 2D, less airy and detailed and often with slightly "edgy" touch (on violin etc.) and it was quite consistent on anything and in any settings ...

On vocals with U47, BAE was bigger and sweeter ...

There was not much left to test ....

Since before I already tried Pendulum, LaChapell, DW Fearn and Thermionic Earlybird and always found Forssell SMP-2 unsurpassable on acoustic instruments, my hopefully final conclusion is that a tube preamp is not needed for my purpose (recording delicate solo acoustic instruments).

And since over the years it is my maybe 150th attempt to compare something to Schoeps (MK2) and Forssell and to find something yet better - with the same result (returning to what I already have), I promised the Universe and the Goddess of Music that I will stop testing and trying whatever else and will concentrate only on creatíng new music

Let us see how long this vow will last
But I can't buy SmP2 now. I'm sorry. If there is any channel, please let me know. Thank you.
Old 1 week ago
  #162
Old 1 week ago | Show parent
  #163
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Plush's Avatar
 
5 Reviews written
🎧 15 years
Huge report from these in house tube preamplifiers:
2 Analoguetube AT-3 (English)-KING of TONE
Gyraf IX (Danish)
4 Tube Tech PM1A in RM-2 racks (Danish)
Thermionic Culture Snow Petrel (English)-a high gain mic amp made to be used with Coles 4038 ribbon mics.
Old 1 week ago | Show parent
  #164
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🎧 10 years
Quote:
Originally Posted by snod_donkey ➡️



This is a quick test recording with an analogue Addicts valve mic pre and acoustic guitar
Thanks for this, I've often wondered.

They look like the front end of the Ferrograph tape recorders.
Old 1 week ago | Show parent
  #165
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🎧 15 years
Quote:
Originally Posted by Earcatcher ➡️
What do you exactly want from a tube preamp in this context? The normally very neutral Earlybird can be thick and colourful by "pushing" it: turn down the output gain and increase the amplification. If you want to go into further distortion you can even select the low input impedance. So I wonder how this cannot be enough for you.

There aren't many classical recordings of mine that do not include tube amplification. Spots in particular blend much better with a main array when recorded with a valve amp. This is caused by the slight compression effect that valves give. Spots will not cause dynamic spikes that will stick out in the mix, with that "decent" amplification. Another trick for this better blend is to use ribbons for spots.
Instead of a tube preamp, why not just use a compressor/limiter on a spot mic track to tame the peaks. If you’re doing it after the fact on the iso track you can adjust for transparency.
Old 1 week ago | Show parent
  #166
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Earcatcher's Avatar
 
🎧 10 years
Quote:
Originally Posted by Folkie ➡️
Instead of a tube preamp, why not just use a compressor/limiter on a spot mic track to tame the peaks. If you’re doing it after the fact on the iso track you can adjust for transparency.
Compressors are generally way too drastic in their effect and in their sonic imprint. Why not fix this aspect at the source? Good tube preamps are very transparent anyway, but will just not overemphasize very short transients, like most solid state amps do. Also: if you have something like ten (stereo) spot tracks, how are you going to compress them all individually during the mix? I have a few nice compressors, but not five available to use on spots only. (And software compressors don't come close to hardware.)
Old 1 week ago | Show parent
  #167
Quote:
Originally Posted by Earcatcher ➡️
Compressors are generally way too drastic in their effect and in their sonic imprint. Why not fix this aspect at the source? Good tube preamps are very transparent anyway, but will just not overemphasize very short transients, like most solid state amps do. Also: if you have something like ten (stereo) spot tracks, how are you going to compress them all individually during the mix? I have a few nice compressors, but not five available to use on spots only. (And software compressors don't come close to hardware.)
Input transformers in solid state microphone preamps also take away some of the transients in a similar way as tube-amps do, at least that is my experience. In the past I used Demeter and Tubetech tube-preamps. I don't use them amymore because of practical reasons. I always bring a few transformer balanced solid state microphone preamps to my sessions, as back-up for problem solving.
Old 1 week ago | Show parent
  #168
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Earcatcher's Avatar
 
🎧 10 years
Quote:
Originally Posted by Orgeltonmeister ➡️
Input transformers in solid state microphone preamps also take away some of the transients in a similar way as tube-amps do, at least that is my experience. In the past I used Demeter and Tubetech tube-preamps. I don't use them amymore because of practical reasons. I always bring a few transformer balanced solid state microphone preamps to my sessions, as back-up for problem solving.
Yes, I agree to a certain extent: I'm using transformer balanced preamps for that purpose as well, but there are some that are just as fast in their transient response as transformerless preamps, so you'll have to test this before you can be sure. Especially preamps with input transformers only (and none on the outputs) can be very fast. (ADT, Elberg.) The compression effect on very high short peaks is actually what is desired mostly, as it will sound more like our ears hear. Fortunately most transformers do that more or less. Tubes have a somewhat wider compression behaviour, into the sustain dynamics.
Old 1 week ago | Show parent
  #169
Quote:
Originally Posted by Earcatcher ➡️
Yes, I agree to a certain extent: I'm using transformer balanced preamps for that purpose as well, but there are some that are just as fast in their transient response as transformerless preamps, so you'll have to test this before you can be sure. Especially preamps with input transformers only (and none on the outputs) can be very fast. (ADT, Elberg.) The compression effect on very high short peaks is actually what is desired mostly, as it will sound more like our ears hear. Fortunately most transformers do that more or less. Tubes have a somewhat wider compression behaviour, into the sustain dynamics.
I think it all depends on the turn ratio of the used transformers. Tube amps often have transformers with higher turn ratios, 1:10 or higher, while solid state preamps with transformers most of the time happen to have something between 1:2 ( the famous Jensen design) and 1:7 But some can have transformer turn ratios as low as 1:1. My Soundcraft LM1 mixer has paired transistors on the input and a transformer that has 1:1 ratio. These transformers you hardly can notice. Other solid state designs let you change the input impedance, what happens is they change the input transformer its turn ratio. The sound differences can be huge.
Old 1 week ago
  #170
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Piedpiper's Avatar
 
1 Review written
🎧 10 years
Some tube circuits can handle transients particularly well, if you're not pushing into them too hard.
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