Update after here and on Amazon people refering to a single ened tube pre amp for my SS
Ive decided on the Bravo Audio V1 http://www.amazon.com/Bravo-Audio-V1-Headphone-Amplifier/dp/B00A2QKTLW/ref=sr_1_2?ie=UTF8&qid=1460591998&sr=8-2&keywords=bravo+v1
This has the Russian EH 6922 Tube for amplification.
Ive decided on the Bravo Audio V1 http://www.amazon.com/Bravo-Audio-V1-Headphone-Amplifier/dp/B00A2QKTLW/ref=sr_1_2?ie=UTF8&qid=1460591998&sr=8-2&keywords=bravo+v1
This has the Russian EH 6922 Tube for amplification.
Last edited:
You might want to take a look at the Bottlehead Quickie, battery powered tube preamp. It is fun and easy to build.
Member
Joined 2009
Paid Member
That will probably be a decent introduction to tubes for you. I'd guess that this is a tube + MOSFET design, not unlike Pete Millett's starving student amp.
Might have more gain than you need, might be more linear if it were higher voltage, but it will probably sound OK and can always double as an extra headphone amp.
Thanks for your comment Sodacose but unless I'm wrong I think it will work fine ill just solder my speaker's to bottom of the board on that headphone jack but the power should be fine as I have a mixer, 32band dual channel EQ and rack mount crossover with adjustable gain that if needed can boost the tube pre up.
Mods to Bravo V1
Here are some mods to this amp that I found on Parts Express . Out of the box it sounds very good. Swapped out the output caps to 2200 mfd and swapped out the mosfets to IRL510 and WOW! What a difference. No way to beat the value and sound. This sounds very promising ....
Here are some mods to this amp that I found on Parts Express . Out of the box it sounds very good. Swapped out the output caps to 2200 mfd and swapped out the mosfets to IRL510 and WOW! What a difference. No way to beat the value and sound. This sounds very promising ....
Attachments
If anyone knows of a better pre built Tubepreamp for an SS please post it here. I need all the help i can get 😕
In general terms there are two basic types of tube circuits. Push pull which really generally have better specs and SE which many think sound better. This is a very general statement and actually a lot more can be said on the subject. I now have both kinds of tube pre, I finished my SRPP pre this week. I like my SE tube pre better with SS amps. I like lots of 2nd harmonic I guess. The SRPP sounds more like my excellent SS pre, nothing wrong with either just personal preference comes into play.
You can go to;
http://diyaudioprojects.com/Tubes/tubes.htm
and see schematics and descriptions of both types at one site.
You can go to;
http://diyaudioprojects.com/Tubes/tubes.htm
and see schematics and descriptions of both types at one site.
Last edited:
Member
Joined 2009
Paid Member
Looks suitable for sone fun.
Read this: http://www.valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf
You may want to substitute an ECC82 for low grid current ?
You could then replace the transistor (current source load) with a resistor for much lower gain (good idea if your power amp has plenty of gain) and get a bit more 'tube flavour' into the bargsin. The 24V supply needs to be clean if you do this as without the transistor more power supply noise gets to the output.
Read this: http://www.valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf
You may want to substitute an ECC82 for low grid current ?
You could then replace the transistor (current source load) with a resistor for much lower gain (good idea if your power amp has plenty of gain) and get a bit more 'tube flavour' into the bargsin. The 24V supply needs to be clean if you do this as without the transistor more power supply noise gets to the output.
Some tube fanatics have a problem using SS with tubes. I do not. If it works it works. Go for it and let us know what you think.
Hey there --
ECC82 is the Euro version of 12AU7. Unfortunately for this amp, 12AU7 needs 12V for its heaters, not the 6V used by 6922. If you dropped a 12AU7 in there, not only would it be working at super-low plate voltage, it would also be working with starved heater. The tube would work with very weak performance (lower gm, lower gain, higher internal resistance).
Referring to Merlin's article, it does look like this headphone amp circuit has some serious compromises. The one that sticks out for me is the low input impedance of the input triode run with such low plate voltage (16V). In this headphone amp, the wiper of a volume control goes straight to the input triode's grid. The output impedance from the pot is going to vary, and the input impedance of the tube is low, so the two will interact.
I was looking at the "Starving Student" amp, originally published by Pete Millett. It originally used two 19J6 tubes, but the supply of these little tubes dried up. A couple of people modified the design to work with 12AU7 tubes instead.
The Starving Student uses a 48V DC power supply instead of 24V, and parallels two sections of a 12AU7 for each channel, running them with about 26V on the plate and 1.3V on the cathode (650uA plate current). Maybe that's enough to keep the 12AU7 out of grid current territory.
The other big difference is how the Starving Student Amp's output IRF510's are biased. The 12AU7 plates are RC coupled to the IRF510 gates, the bias for the IRF510 is derived from a voltage divider (R2, R4 and R8, R10), and the sources of the IRF510's are fed from the +12V from the DC heater supply for the 12AU7's, with no LM317 or other CCS used.
But maybe all this is not important. It looks like Pete M and dsavitsk do the same with the volume control as is done in the Bravo V1.
Maybe the whole idea of running these tubes with such low plate voltages is to get lots of tubey distortions happening and use the amp as a sort of euphonic effects box. Nothing wrong with that. I was thinking of putting together something along those lines and using it at work for playing Pandora, etc. Would take the edge off the digital compression artifacts.
Did you all notice that the Bravo V2 uses the DC heater voltage to feed 6VDC to the LM317 CCS for the IRF510 source?
Also, the Bravo V3 uses a 12AU7 and 12VDC heater, to the LM317.
So it looks like they're all derived from the Starving Student, just re-jiggered to work for a 24VDC supply (and resulting 16V on the tube's plate, which will raise the distortion, etc.).
--
ECC82 is the Euro version of 12AU7. Unfortunately for this amp, 12AU7 needs 12V for its heaters, not the 6V used by 6922. If you dropped a 12AU7 in there, not only would it be working at super-low plate voltage, it would also be working with starved heater. The tube would work with very weak performance (lower gm, lower gain, higher internal resistance).
Referring to Merlin's article, it does look like this headphone amp circuit has some serious compromises. The one that sticks out for me is the low input impedance of the input triode run with such low plate voltage (16V). In this headphone amp, the wiper of a volume control goes straight to the input triode's grid. The output impedance from the pot is going to vary, and the input impedance of the tube is low, so the two will interact.
I was looking at the "Starving Student" amp, originally published by Pete Millett. It originally used two 19J6 tubes, but the supply of these little tubes dried up. A couple of people modified the design to work with 12AU7 tubes instead.
The Starving Student uses a 48V DC power supply instead of 24V, and parallels two sections of a 12AU7 for each channel, running them with about 26V on the plate and 1.3V on the cathode (650uA plate current). Maybe that's enough to keep the 12AU7 out of grid current territory.
The other big difference is how the Starving Student Amp's output IRF510's are biased. The 12AU7 plates are RC coupled to the IRF510 gates, the bias for the IRF510 is derived from a voltage divider (R2, R4 and R8, R10), and the sources of the IRF510's are fed from the +12V from the DC heater supply for the 12AU7's, with no LM317 or other CCS used.
But maybe all this is not important. It looks like Pete M and dsavitsk do the same with the volume control as is done in the Bravo V1.
Maybe the whole idea of running these tubes with such low plate voltages is to get lots of tubey distortions happening and use the amp as a sort of euphonic effects box. Nothing wrong with that. I was thinking of putting together something along those lines and using it at work for playing Pandora, etc. Would take the edge off the digital compression artifacts.
Did you all notice that the Bravo V2 uses the DC heater voltage to feed 6VDC to the LM317 CCS for the IRF510 source?
Also, the Bravo V3 uses a 12AU7 and 12VDC heater, to the LM317.
So it looks like they're all derived from the Starving Student, just re-jiggered to work for a 24VDC supply (and resulting 16V on the tube's plate, which will raise the distortion, etc.).
--
Im totaly new to tubes and some here say Id be better with a single ended tube common cathode type. So now im confused
Hey there --
ECC82 is the Euro version of 12AU7. Unfortunately for this amp, 12AU7 needs 12V for its heaters, not the 6V used by 6922. If you dropped a 12AU7 in there, not only would it be working at super-low plate voltage, it would also be working with starved heater. The tube would work with very weak performance (lower gm, lower gain, higher internal resistance).
Referring to Merlin's article, it does look like this headphone amp circuit has some serious compromises. The one that sticks out for me is the low input impedance of the input triode run with such low plate voltage (16V). In this headphone amp, the wiper of a volume control goes straight to the input triode's grid. The output impedance from the pot is going to vary, and the input impedance of the tube is low, so the two will interact.
I was looking at the "Starving Student" amp, originally published by Pete Millett. It originally used two 19J6 tubes, but the supply of these little tubes dried up. A couple of people modified the design to work with 12AU7 tubes instead.
The Starving Student uses a 48V DC power supply instead of 24V, and parallels two sections of a 12AU7 for each channel, running them with about 26V on the plate and 1.3V on the cathode (650uA plate current). Maybe that's enough to keep the 12AU7 out of grid current territory.
The other big difference is how the Starving Student Amp's output IRF510's are biased. The 12AU7 plates are RC coupled to the IRF510 gates, the bias for the IRF510 is derived from a voltage divider (R2, R4 and R8, R10), and the sources of the IRF510's are fed from the +12V from the DC heater supply for the 12AU7's, with no LM317 or other CCS used.
But maybe all this is not important. It looks like Pete M and dsavitsk do the same with the volume control as is done in the Bravo V1.
Maybe the whole idea of running these tubes with such low plate voltages is to get lots of tubey distortions happening and use the amp as a sort of euphonic effects box. Nothing wrong with that. I was thinking of putting together something along those lines and using it at work for playing Pandora, etc. Would take the edge off the digital compression artifacts.
Did you all notice that the Bravo V2 uses the DC heater voltage to feed 6VDC to the LM317 CCS for the IRF510 source?
Also, the Bravo V3 uses a 12AU7 and 12VDC heater, to the LM317.
So it looks like they're all derived from the Starving Student, just re-jiggered to work for a 24VDC supply (and resulting 16V on the tube's plate, which will raise the distortion, etc.).
--
Thank you so much for that info and ill gladly take this into consideration 😀
A 12AU7 has a tapped filament (like a 12AX7), which means you can run it on 6.3V or 12.6V. You just wire it differently.
You will not get much more simpler than this and believe me it sounds great with SS amps.
4S Universal Preamplifier for 12A*7 Tubes
Perfect 1st point to point build for a newbie. 5 components to hook up to the tube socket with a pot and input outputs. The PS is about as simple as you will see for a tube rectifier. I used a Triadmaganetics 6 hy choke to keep the cost down. Worked great, quite with horns.
4S Universal Preamplifier for 12A*7 Tubes
Perfect 1st point to point build for a newbie. 5 components to hook up to the tube socket with a pot and input outputs. The PS is about as simple as you will see for a tube rectifier. I used a Triadmaganetics 6 hy choke to keep the cost down. Worked great, quite with horns.
Yes, I was referring the OP about modding the Bravo V1 headphone amp (on a pcb). But yes, you're right of course, you can use 12AU7 if you can wire its heaters differently.
--
Does this preamp have to be able to drive headphones?
Simple yes, but not high performance at all. The volume control is in the wrong place, for one thing. If you put the volume control on the output, it will present a varying load to the preamp tube. Also, if you think about it, the tube will be running at full gain all the time, with highest distortion. Turning down the volume control (if placed at the output) will not change this. You'll just be burning off the excess gain you're getting from the tube (again, at its highest distortion). If the volume control is at the input, you reduce the level of the input to the tube's grid. Distortion in a triode is proportional to level, so the lower level at the input means lower distortion at the output.
And since that circuit is based on tubes with relatively high plate resistance (12AU7 rp will be about 10k), the preamp won't do well at all driving the low input resistance of a typical solid state amp (10k to 47k ohms). A 12AU7 driving a 10k load will sound rolled off and sleepy. But that might be the 'tube sound' you're after. It is kind of enjoyable.
A proper preamp could be done if you take that 12AU7 and use a cathode follower after it. Some will say the 12AU7 is a bad choice because it is a poor performer for audio, but I'll bet it would be good enough if done right. You could even use this old circuit from ye olde RCA Tube Manual:
I wouldn't implement it exactly that way. I'd increase the plate current and change component values to suit. But that's the general idea.
Incidentally, this RCA circuit is basically the same idea as used in the Bravo headphone amp, except the Bravo uses a MOSFET source follower instead of a tube cathode follower.
None of the above will drive headphones, by the way.
--
Simple yes, but not high performance at all. The volume control is in the wrong place, for one thing. If you put the volume control on the output, it will present a varying load to the preamp tube. Also, if you think about it, the tube will be running at full gain all the time, with highest distortion. Turning down the volume control (if placed at the output) will not change this. You'll just be burning off the excess gain you're getting from the tube (again, at its highest distortion). If the volume control is at the input, you reduce the level of the input to the tube's grid. Distortion in a triode is proportional to level, so the lower level at the input means lower distortion at the output.
And since that circuit is based on tubes with relatively high plate resistance (12AU7 rp will be about 10k), the preamp won't do well at all driving the low input resistance of a typical solid state amp (10k to 47k ohms). A 12AU7 driving a 10k load will sound rolled off and sleepy. But that might be the 'tube sound' you're after. It is kind of enjoyable.
A proper preamp could be done if you take that 12AU7 and use a cathode follower after it. Some will say the 12AU7 is a bad choice because it is a poor performer for audio, but I'll bet it would be good enough if done right. You could even use this old circuit from ye olde RCA Tube Manual:
I wouldn't implement it exactly that way. I'd increase the plate current and change component values to suit. But that's the general idea.
Incidentally, this RCA circuit is basically the same idea as used in the Bravo headphone amp, except the Bravo uses a MOSFET source follower instead of a tube cathode follower.
None of the above will drive headphones, by the way.
--
Last edited:
- Status
- Not open for further replies.