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Layout / Schematic for Tube Mic Preamp with Transformer
Layout / Schematic for Tube Mic Preamp with Transformer
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Old 13th January 2021, 01:17 PM   #1
22uf is offline 22uf  United Kingdom
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Default Layout / Schematic for Tube Mic Preamp with Transformer

Hi,
Does anybody know of any good layouts/schematics for a simple 1 channel DIY tube mic pre with transformers? I do not need phantom power.

In the circuit I want to avoid any IC chips.

For components my budget target is £100 - £200.

Is this schematic any good?
Build a tube Mic Pre: Build Your Own Two Channel Vacuum Tube Mic Preamp! | Tape Op Magazine | Longform candid interviews with music producers and audio engineers covering mixing, mastering, recording and music production.

I canít really seem to find anything online. Ideally I want a vintage schematic, but most of all importance is that it is relatively easy to build.

Last edited by 22uf; 13th January 2021 at 01:29 PM.
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Old 15th January 2021, 02:39 AM   #2
22uf is offline 22uf  United Kingdom
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Any ideas?
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Old 15th January 2021, 03:28 AM   #3
rayma is online now rayma  United States
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That circuit looks pretty good, and here are a couple of older ones.
Vacuum Tube Stereo Microphone Preamp
Shure M65 Stereo Phono Pre-Amplifier Manual | Vinyl Engine

A solid state mic preamp would be much easier to build, and more quiet, though.

Last edited by rayma; 15th January 2021 at 03:31 AM.
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Old 18th January 2021, 09:55 AM   #4
22uf is offline 22uf  United Kingdom
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Quote:
Originally Posted by rayma View Post
That circuit looks pretty good, and here are a couple of older ones.
Vacuum Tube Stereo Microphone Preamp
Shure M65 Stereo Phono Pre-Amplifier Manual | Vinyl Engine

A solid state mic preamp would be much easier to build, and more quiet, though.

Yes, this looks simple enough. Are there any sound clips anywhere? Is it based on anything?
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Old 18th January 2021, 10:14 AM   #5
Schmitz77 is offline Schmitz77
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The quitness of tube phono amps is nearly irrelevant, as the most noise comes from the record surface. The noise floor of tubes is so low and their dynamic range is so high, that the LP is not the media to match with it.
Shure M65 is an all time classic.
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Old 18th January 2021, 11:21 AM   #6
baudouin0 is offline baudouin0
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22uF your schematic looks good and will drive balanced out. The step up is needed if you want balanced in and good noise figure from say a SM58.


OEP do a good range of suitable transformers:


https://uk.farnell.com/oep-oxford-el...150/dp/1172344

Last edited by baudouin0; 18th January 2021 at 11:28 AM.
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Old 18th January 2021, 11:42 AM   #7
Burnedfingers is offline Burnedfingers  United States
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Quote:
Originally Posted by rayma View Post
That circuit looks pretty good, and here are a couple of older ones.
Vacuum Tube Stereo Microphone Preamp
Shure M65 Stereo Phono Pre-Amplifier Manual | Vinyl Engine

A solid state mic preamp would be much easier to build, and more quiet, though.
I would look to find a Shure I have used them in the past and they sound fine are quiet and with a re-cap will last and perform well. If your wanting to build then I like the 6AU6 mic preamp rayma posted.

Last edited by Burnedfingers; 18th January 2021 at 11:45 AM.
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Old 18th January 2021, 11:46 AM   #8
martyh is offline martyh  United States
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If you want transformers the RCA MI-11241 from the BC-2B is a classic. The feedback
and low current draw make it easy on the transformer so you wont need anything as expensive as an LS27 shown in the schematic at this link. RCA BC-2B Recording Studio Console c. 1952 – Preservation Sound The schematic at the link is correct other than the cathode voltages and transformer numbers. 15K:600 is about right for the output transformer. The input transformer should be about 1:10 turns ratio to get the specified 40 dB of gain
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Old 18th January 2021, 01:34 PM   #9
Kay Pirinha is offline Kay Pirinha  Germany
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Quote:
Originally Posted by Schmitz77 View Post
The quitness of tube phono amps is nearly irrelevant, as the most noise comes from the record surface. The noise floor of tubes is so low and their dynamic range is so high, that the LP is not the media to match with it.
Shure M65 is an all time classic.
Do you seriously listen to records via a microphone?

Best regards!
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Old 19th January 2021, 12:15 AM   #10
HollowState is offline HollowState  United States
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Here's a vintage mike preamp to consider. You could build only one channel if needed and omit the phantom power. The expensive UTC transformers can be substituted as well as the tube choices.
Attached Images
File Type: jpg preamp1.jpg (732.4 KB, 44 views)
File Type: jpg preamp2.jpg (735.1 KB, 44 views)
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