Balanced diy tube preamp

[globalplayer]

Hi.
I need a balanced diy tube preamp for my soundsystem. 2 channel stereo line XLR in/output. "Audiophile" grade. Whatever that is lol. It should sound just very good. No sloppy bass, etc.

It should produce deep clean precise bass and have a warm like sound in mids/highs.

I found out about the aikido pre amp but I think it won't sound exactly warm and then again the schematic I found has no balanced in and outputs.

Any recommendations? Hints?
Much appreciated.

Or just add balanced in and outputs to the aikido but I don`t know exactly how?

 

[rayma]

Or just add balanced in and outputs to the aikido but I don`t know exactly how?

Many balanced preamps just add an inverter stage at the output for the opposite polarity.

 

[globalplayer]

Many balanced preamps just add an inverter stage at the output for the opposite polarity.

I see.
That makes sense.
And at the input?

 

[rayma]

And at the input?

If you have balanced sources, you can use a balanced to single ended converter at the input.
BCF PCB and Kit

How much gain (if any) do you need?

 

[nerdorama]

How about something like this?
http://www.nutshellhifi.com/Raven-MarkII.gif

 

[globalplayer]

If you have balanced sources, you can use a balanced to single ended converter at the input.
BCF PCB and Kit

How much gain (if any) do you need?

That looks good but the schematic has no values.
Gain around 0-12dB max.
But then again headroom is always good.

 

[Bandersnatch]

I run a SEP linestage to drive the XLR input on my Rane AC23B. It is a LTP of EL84 triodes, with B+ near 500V and 15k Ohm loads. The only mod I am considering is dropping the loads to 10k, and bumping the idle current by 25-30%.

Depending on how much gain is needed, a 12B4 can be used, or EL86 triodes.

There is another option I have under consideration, and that is an amplifier triode, feeding a stout concertina....but since the current one works quite well, I am not feeling the need to change it just yet...

The EL84 LTP rig is running 7.5 uF X386, 330 VAC polypropylene motor runs for output coupling. It is a little hard on the input OP amp...
cheers,
Douglas

 

[globalplayer]

How about something like this?
http://www.nutshellhifi.com/Raven-MarkII.gif

This looks like it will sound very good.
But parts are very expensive.

 

[rayma]

That looks good but the schematic has no values.

Parts values (for various tube choices) are in the user guide.
http://glass-ware.com/User_Guides/BCF 9-Pin.pdf

Maybe a simple diff amp would work for you.
One version has buffers at the outputs, but you may not need them.
Balanced Aikido

 

[globalplayer]

I run a SEP linestage to drive the XLR input on my Rane AC23B. It is a LTP of EL84 triodes, with B+ near 500V and 15k Ohm loads. The only mod I am considering is dropping the loads to 10k, and bumping the idle current by 25-30%.

Depending on how much gain is needed, a 12B4 can be used, or EL86 triodes.

There is another option I have under consideration, and that is an amplifier triode, feeding a stout concertina....but since the current one works quite well, I am not feeling the need to change it just yet...

The EL84 LTP rig is running 7.5 uF X386, 330 VAC polypropylene motor runs for output coupling. It is a little hard on the input OP amp...
cheers,
Douglas

I like the simple approach.
Any schematic?

 

[globalplayer]

Parts values (for various tube choices) are in the user guide.
http://glass-ware.com/User_Guides/BCF 9-Pin.pdf

Maybe a simple diff amp would work for you.
One version has buffers at the outputs, but you may not need them.
Balanced Aikido

Ok.
Missed that.

Balanced aikido looks perfect.

An externally hosted image should be here but it was not working when we last tested it.

But no values.

 

[rayma]

Balanced aikido looks perfect. But no values.

Depends on the tubes, mainly the cathode resistors change with the tubes.
http://glass-ware.com/User_Guides/Aikido LV.pdf

 

[globalplayer]

Depends on the tubes, mainly the cathode resistors change with the tubes.
http://glass-ware.com/User_Guides/Aikido LV.pdf

I think this one will do.
Thank you very much.

Which tubes should I use?

 

[Bandersnatch]

The Akido uses 8 triodes per channel, and it needs a balanced signal to start with. Have you a balanced source, or is it SE?
cheers,
Douglas

 

[globalplayer]

I have a balanced source and I want balanced outputs also.
I might build a unbalanced input one also but later on.

 

[rayma]

Which tubes should I use?

I'd say the 6FQ7, for 20dB gain. Here's JB's info.

"A 12AX7 input tube will yield a gain close to 50 (mu/2);
a 6FQ7 (6CG7) input tube will yield a gain near 10, which would be excellent for a line stage amplifier;
the 6DJ8 or 6H30 in the output stage would deliver a low output impedance that could drive capacitance-laden cables.

In other words, the list of possible tubes is a long one: 6AQ8, 6BC8, 6BK7, 6BQ7, 6BS8, 6DJ8, 6FQ7, 6GC7, 6H30, 6KN8, 6N1P, 12AT7, 12AU7, 12AV7, 12AX7, 12BH7, 12DJ8, 12FQ7, 5751, 5963, 5965, 6072, 6922, E188CC, ECC88, ECC99... The only stipulations are that the two triodes within the envelope be similar and that the tube conforms to the 9A or 9AJ base pin-out. Sadly, the 12B4 and 5687 cannot be used with this PCB."

 

[globalplayer]

That`s quite a long list.
Thanks again.

 

[rayma]

You can use any standard-base twin triode, yielding a gain of mu/2, if you use a buffer.
Just choose the tube, the supply voltage, and cathode resistors.

 

[globalplayer]

Alright.
Are there some tricks to make it sound warmer in case it is too cold for my taste?
As in component values or supply voltages?

 

[rayma]

You can use coupling capacitors with that kind of coloration. The circuit topology
is intended to largely cancel the tube's distortion.