Preamp + Headphone Amp

[juan_felt]

Hi!

I'm trying to build a unit so I can use my pedalboard with headphones.

I'm using this "Laney Supergroup" preamp: https://drtube.com/schematics/laney/Super_Group_100_Mk1_preamp.pdf with the mods from Tagboard FX https://tagboardeffects.blogspot.com/2018/02/laney-supergroup-100-mki-preamp.html?showComment=1538141143076#c4220482539811236012 (only built one input).

And I'm putting it in front of different headphone amps I tried (MXR: http://www.generalguitargadgets.com/pdf/ggg_mxr_hpamp_sc.pdf, Ruby from Runoffgroove: http://www.runoffgroove.com/ruby.html), but I always encounter the same issue, it clips and at regular/low volumes. I tried the headphone output from a Hotone Nanolegacy and I get quite hi volumes without distortion.

What am I doing wrong? Do you have any suggestions?

Thanks, J!

[antonis]

<What am I doing wrong?>

Nothing..
(except, perhaps, you're placing a pre-amp in front of ready "plug 'n' play" headphone amps - too much gain...!!)

[PRR]

What headphones?

9V supply amp will get quite loud in 32 Ohm phones, but may not be WOW in 300 Ohm headphones.

[juan_felt]

First, thanks for all the replies:)

What headphones?

9V supply amp will get quite loud in 32 Ohm phones, but may not be WOW in 300 Ohm headphones.

I tried with 32 Ohm headphones, good and medium quality ones, and I always end up with the same result: normal/regular volume and nasty clipping.

Yesterday I made another amp based on the TDA2003 chip and I get great volume levels and very little to none clipping.
I used the following schematic:


This is intended to be used with speakers, what mods should I make for it to be suitable for headphones?

Thanks!!

[PRR]

> mods should I make for it to be suitable for headphones?

If it is working good, don't change anything.

[anotherjim]

Put your headphones on the head of a store dummy. Play your guitar through that preamp and the TDA2003 amp. Watch as the dummies head melts and then implodes. 

I wonder how many only followed the link to the Laney valve amp scheme and though that's what you made?

I can't work out if that tagboard amp simulator has a master volume on the output, it probably should.

The clipping you experience is probably solely due signal level mismatch, assuming the amp sim sounds ok in other amplification, you have been running it into headphone amps intended to get plenty loud enough off a clean direct guitar signal. All you should need to do is turn the output volume of the preamp down and/or the input of the headphone amp down. If it won't get clean without getting too quiet, then you need a higher supply voltage....but do think about your hearing.
The TDA2003 (I thought was long ago obsolete) is intended for 12v supply and doesn't need much signal gain as it was intended to run off the stronger signal from a radio receiver or tape head preamp, so probably not as easy to clip and that circuit is only x11 voltage gain I think, but that means it could still clip if the input signal goes much over 1v peak-peak. Also, it has a low input impedance which isn't well specified but about 100k. If the preamp you made is one of those with the tone stack at the very end and no output buffer, the TDA2003 input will drag the preamp output down since the preamp really expects to feed 1M, not 100k. It will also bend the tone stacks response out of whack. Either the preamp needs a buffered output or the TDA2003 needs a buffered input.

For headphones, it won't change much at all, despite the higher impedance of the cans. You don't need two for stereo, one TDA2003 can drive both sides of the cans together.

[printer2]

What voltage are you running the tubes off of?

[juan_felt]

Thanks for all the repiles!

> mods should I make for it to be suitable for headphones?

If it is working good, don't change anything.

Always good advice

Put your headphones on the head of a store dummy. Play your guitar through that preamp and the TDA2003 amp. Watch as the dummies head melts and then implodes. 

I wonder how many only followed the link to the Laney valve amp scheme and though that's what you made?

Ooopss... Sorry if I wasn't clear... I didn't do the actual tube preamp, I used the tagboard preamp with transistors.

I can't work out if that tagboard amp simulator has a master volume on the output, it probably should.

It does, it has a 100k vol pot.

The clipping you experience is probably solely due signal level mismatch, assuming the amp sim sounds ok in other amplification, you have been running it into headphone amps intended to get plenty loud enough off a clean direct guitar signal. All you should need to do is turn the output volume of the preamp down and/or the input of the headphone amp down. If it won't get clean without getting too quiet, then you need a higher supply voltage....but do think about your hearing.
The TDA2003 (I thought was long ago obsolete) is intended for 12v supply and doesn't need much signal gain as it was intended to run off the stronger signal from a radio receiver or tape head preamp, so probably not as easy to clip and that circuit is only x11 voltage gain I think, but that means it could still clip if the input signal goes much over 1v peak-peak. Also, it has a low input impedance which isn't well specified but about 100k. If the preamp you made is one of those with the tone stack at the very end and no output buffer, the TDA2003 input will drag the preamp output down since the preamp really expects to feed 1M, not 100k. It will also bend the tone stacks response out of whack. Either the preamp needs a buffered output or the TDA2003 needs a buffered input.

For headphones, it won't change much at all, despite the higher impedance of the cans. You don't need two for stereo, one TDA2003 can drive both sides of the cans together.

I will address this issues and let you know what happened!!

Thanks again!!

J