Super Simple Single Stage Tube PreAmp

[bibin3210]

Tube Buffer an attempt:

 

[Fantastic]

Your input impedance is very high. So it needs only something like 0.022uF at the input and 2.2uF at the output with a 20K load to get less than -0.2dB at 20 Hz. Gain as usual is about 1 dB below unity.

 

[bibin3210]

Your input impedance is very high. So it needs only something like 0.022uF at the input and 2.2uF at the output with a 20K load to get less than -0.2dB at 20 Hz. Gain as usual is about 1 dB below unity.

Here is the simulation with 0.022uF at input and 2.2uF at output:




Thanks,
Bibin

 

[Fantastic]

I don't understand that curve. Is that a rising response at LF ?
If so , some one is making a mistake. I just checked what I got and it appears to be like what I expected . And I haven't had a drop of hooch tonight !

Here the 20 K volume pot is set at about -10dB from max position with a 400pF load in parallel. ( cable + stray capacitance)

RL being 14K + 6K . Voltage measured across 6K with 400pF in parallel with it.

 

[bibin3210]

I don't understand that curve. Is that a rising response at LF ?
If so , some one is making a mistake. I just checked what I got and it appears to be like what I expected . And I haven't had a drop of hooch tonight !

Then it might be my mistake, let me check my Spice sim parameters.


Thanks,
Bibin

 

[bibin3210]

 

[Fantastic]

Great, you fixed it. Try it out. Lets see if you find it useful.
From experience....sometimes it does and sometimes not ! Depends on the other equipments parameters. Here both caps are small , so you can use decent film caps.

 

[Mohanv]

Bibin, you are a very clever guy. Which Spice did you use for the simulations? I am used to PSpice. Too old to change now!

Most power amps have input impedances of 50k to 100k, unless you are targeting to drive old Professional amps with 10K input impedance. As long as the output impedance of your Line Stage is less than 1/10th of the input impedance of your Power Amp, you should be OK. Also remember that the higher the output impedance of your preamp, the higher the risk of RF.

Perhaps you are aware of this already.

Just saying ....... You are doing some wonderful creative work
Mohan

 

[bibin3210]

Bibin, you are a very clever guy. Which Spice did you use for the simulations? I am used to PSpice. Too old to change now!

Most power amps have input impedances of 50k to 100k, unless you are targeting to drive old Professional amps with 10K input impedance. As long as the output impedance of your Line Stage is less than 1/10th of the input impedance of your Power Amp, you should be OK. Also remember that the higher the output impedance of your preamp, the higher the risk of RF.

Perhaps you are aware of this already.

Just saying ....... You are doing some wonderful creative work
Mohan

Mohan,I am using LTSpice.

Regards,
Bibin

 

[koushik]

Hi Bibin,

Any update on this build?
I was wondering if you can help me/us with the PCB and BOM for this build. I am interested in building a Line Stage Tube Buffer to put it before my Passive pre.

Regards,
Koushik

 

[bibin3210]

Hi Bibin,

Any update on this build?
I was wondering if you can help me/us with the PCB and BOM for this build. I am interested in building a Line Stage Tube Buffer to put it before my Passive pre.

Regards,
Koushik

Hi Koushik,

You need to add a buffer after this as the output impedance is very high. I have few PCBs left out from the initial batch which needs some minor corrections. I can send it to you if you are interested. All components are available locally. PM me your shipping address.

I am currently working on another tube based line stage and phono preamps. This single stage will be modified to buffer and planning to make the revised PCBs along with the new line stage and phono preamps.

Thanks,
Bibin

 

[gopib]

snip

I am currently working on another tube based line stage and phono preamps. This single stage will be modified to buffer and planning to make the revised PCBs along with the new line stage and phono preamps.

Thanks,
Bibin

That will be good as I am looking at building a tube based pre-amp with multiple sources including a phono. If the gain can be selected it would be a bonus. I found some designs, but do not have the skills/knowledge to determine the best one. Will look forward to your build.

 

[koushik]

Hi Koushik,

You need to add a buffer after this as the output impedance is very high. I have few PCBs left out from the initial batch which needs some minor corrections. I can send it to you if you are interested. All components are available locally. PM me your shipping address.

I am currently working on another tube based line stage and phono preamps. This single stage will be modified to buffer and planning to make the revised PCBs along with the new line stage and phono preamps.

Thanks,
Bibin

Hi Bibin,

I am intending to build a tube line stage buffer with unity gain just to introduce a tube sound in the chain. My amp is very sensitive (only 0.375v for rated output) and input impedance also quite low(20K) and any increase of gain will be difficult to handle.

I shall wait for your opinion after you complete your present build. What do you think? Please suggest.

Regards,
Koushik.

 

[greenhorn]

Koushik, if you want this badly, and you want it now, there are plenty of Little bear & generic 6n3 Tube versions available on ebay pretty cheap,
"Say Hello! to my new little friend" | Audiokarma Home Audio Stereo Discussion Forums

 

[koushik]

Koushik, if you want this badly, and you want it now, there are plenty of Little bear & generic 6n3 Tube versions available on ebay pretty cheap,
"Say Hello! to my new little friend" | Audiokarma Home Audio Stereo Discussion Forums

Thanks greenhorn. I will check the thread ..

 

[bibin3210]

Hi Bibin,

I am intending to build a tube line stage buffer with unity gain just to introduce a tube sound in the chain. My amp is very sensitive (only 0.375v for rated output) and input impedance also quite low(20K) and any increase of gain will be difficult to handle.

I shall wait for your opinion after you complete your present build. What do you think? Please suggest.

Regards,
Koushik.

I will try to get the PCBs for the buffer tube pre-amp soon.

Thanks,
Bibin

 

[koushik]

I will try to get the PCBs for the buffer tube pre-amp soon.

Thanks,
Bibin

Hi Bibib,

Any progress on this? Please let me know. Not in hurry but just curious.

Thanks,
Koushik.

 

[bibin3210]

Hi Bibib,

Any progress on this? Please let me know. Not in hurry but just curious.

Thanks,
Koushik.

Yes, Completed the PCB design. Hope I will get the PCBs in a week or so.

Thanks,
Bibin

 

[koushik]

Yes, Completed the PCB design. Hope I will get the PCBs in a week or so.

Thanks,
Bibin

Eagerly waiting for one. Thank you.

 

[bibin3210]

Eagerly waiting for one. Thank you.

Received the PCBs yesterday....Will test it this weekend...

Thanks,
Bibin