Hey guys! Here's yet another project I wanted to share with you. Got some tubes a couple weeks ago (4x 12AQ5's, 2x 6AQ5's, and 8x 6J6's) because I wanted to put some ideas I had a while ago into practice. One of them is in the following schematic:

http://i.imgur.com/r0vhfWe.png

It's a simple circuit that I wanna try out soon. Haven't had time to try it out yet, but I will get to it when I can. I also had a couple ideas for the chassis this amp could have, but I'm probably gonna do something completely different from them (I don't know where I could get either of them made, so I'll just do something else instead).

http://i.imgur.com/JFljkGC.png
http://i.imgur.com/bjtoB8K.png

I'll update as go along.

[UPDATE]

Had an idea for a cabinet based around a 6" speaker. It's simple enough to adjust the dimensions of the box for any other speaker size tho, and could be used either for a cabinet or a combo.

http://i.imgur.com/i0TCZvY.png
http://i.imgur.com/ecz5X9W.png
http://i.imgur.com/Tw28fdt.png
http://i.imgur.com/smOnP55.png

Quote from: mhelin on September 03, 2013, 02:00:11 PM
I take it that you don't have to use negative supply if you are NOT trying to emulate some known amp. In fact in this JCM800 emulator only three first gain stages actually use additional negative biasing.

I believe the last two stages are just buffers (source followers), so they don't really affect the distortion sound, right?

Quote from: mhelin on September 03, 2013, 02:00:11 PM
How about using a lower supply voltage in range of 48-100V?

I tried this at 120v and seems to work OK with about -2v bias, but I don't have a scope to check curves:

Rg 1M+47k, Rp 100k, R2/D1 1k/I.R. LED, R3 330R (but I'll probably change to 220R later), D2-D4 1x 1N4007, LeftR 1k5, RightR/C2 1k/220nF.

Wonder if an I.R. LED for D2-D4 would work OK as well? I'm not really looking for an authentic replication of a certain amp's sound, I just want decent overdrive/good voltage swing. Most of the distortion I want will come from the power tubes anyways (6AS5, 8K P-P, fixed-bias -13v).

I also would like to point out that I used a "sourcedyne" (split-load) inverter in my prototype, with 47k for both upper and lower loads, 1k source resistor, 10k stopper and 470k Rg. B+ at 125v.

Maybe there's a way to get a more plesant distortion curve in that inverter as well?

If you want to hear a more proper demo of the amp, I suggest you watch this video:

http://www.youtube.com/watch?v=8XAIWrZaoBY

I liked the sound of it so much that I went ahead and made another layout with an included TDA7240 power amp:

https://24.media.tumblr.com/9ec40fccff201617e181e4b7119f6e6a/tumblr_n1lytqCkXy1r4gqjso1_1280.png

https://31.media.tumblr.com/0a481753a3a723fc41d1e71df5f8048f/tumblr_n1lytqCkXy1r4gqjso2_1280.png

I'll be making it on a perfboard and I'll let you guys know if it works (I never have luck with chip power amps... hopefully I don't fry this one).

[UPDATE]

Fried the first TDA. Cause of death: reversed power supply polarity. Oops.
Went out to buy a new one (and a couple of spares), soldered it in and BAM, it worked right away! Sounds amazing, and LOUD!

Quote from: HENK on February 24, 2014, 05:56:40 PM
Morning,
there´s something Different:
In the Schematic the Input is:22N-1M to Earth-12OK.
In the Layout it´s:                22N-120K-1M to Earth.
What´s Wrong-what´s Right???
Thanks for Correction! :tu:

                                                   

The layout is the correct one, since I made it before I went to draw the schematic.
However, both ways work just the same, so it doesn't really matter which one you choose to do.

Quote from: J M Fahey on February 23, 2014, 02:09:51 PM
Cool  :dbtu:

Sounds quite usable even dry, go figure, but the speaker simulation definitely smooths things up.

Thanks  :cheesy:

Thank you! I'm thinking of having it drive a TDA7240 and powering everything from a 12v 7Ah sealed battery I got here. I'm really loving the sound of this little preamp!

Hello there guys! I'm back with yet another strange idea: a CMOS-based preamp. Specifically, I'm using the CD4049UBE, and this is the circuit I ended up with after a good couple of days playing with values.

Here's the schematic:

https://24.media.tumblr.com/6c7488cbc33f0f0085410e599d359fcc/tumblr_n1gmusrwOY1r4gqjso2_1280.png

It's pretty much just a Runoffgroove "3 Legged Dog", but without the input JFET booster, and  the addition of a tone control.

I went ahead and recorded a few samples using Audacity, and just to have an idea of what it might sound through a guitar cab, I used Amplitube to simulate a 1x6 combo cab, and a 2x12 Vox-style cab. Both cabs were recorded with a Dynamic 57 right at the speaker, in the cone position. The tonality change is made via the "Mic" control on the circuit, going from brighter to darker (on the knob, in the order 0, 2.5, 5, 7.5 and 10).

First, the original dry sound: https://soundcloud.com/corvolino03/sets/voxer-49-dry
1x6 cabinet simulation: https://soundcloud.com/corvolino03/sets/voxer-49-preamp
2x12 cabinet simulation: https://soundcloud.com/corvolino03/sets/voxer-49-preamp-1

And last but not least, a PCB layout made in DIY Layout Creator:

https://31.media.tumblr.com/ef2b084f91651e705a178fea2fa87f97/tumblr_n1gmusrwOY1r4gqjso1_1280.png

Hello!

I wanted to share with you guys a small project I made some time ago. It's a 7-pin version of the Fender Princeton model 5C2. For this, I used a 6AQ5 power tube and a 6J6 as the preamp tube, and god some nice vintage-y sounds from it!

Here's the schematic:

http://imageshack.com/a/img855/6201/23xz.png

And here, a video demo of it:

http://youtu.be/qJVdgweHezY?t=1m

I used the alternative power supply for the final circuit, because I wasn't able to get a proper tube PT.

Try this:
http://www.aikenamps.com/ToneControlScaling.html

Quote from: J M Fahey on July 08, 2013, 10:34:54 PM
Regular woofers are useless for guitar, their typical thick cones kill all attack and definition.
Muddy sound.

You *will* hear "something" even at high frequencies, because human ear is very sensitive, but as soon as you play close to othermusicians or a drummer, you get swamped.

I see. Well, I can still keep it for a future project, maybe a 5.1 system (since I have a set of 2x 4" and 2x 6" speakers I got from my brother-in-law I could use for it), or I could get a friend to re-cone it for me with a real guitar speaker cone... Who knows.

For now, I'm quite happy with I've accomplished so far.

Very soon I might try it out with a 32v c.t. Transformer I have laying around.

[UPDATE]

I think I blew my TDA2050

I had about 46vDC from that transformer. It played as normal for some minutes but then, complete silence. I even tried touching the chip's input pin, but no signal of life. I suspected it was the output capacitor so I changed it, and again nothing. I then tried it with my 12v battery and still nothing. Then I suspected it had somehow blown my speaker, so I tried with another. Dead silent.

I guess I'll just buy a bunch of these chips next time I go downtown, so in case I blow another one I can just change it. Oh boy.

[UPDATE 2]

I went to get the chips yesterday, but they only had 2 in stock and I didn't have time to look around other component shops for more...
Kinda feels like when you're running out of lives in a videogame, and you can't find any nearby, and all that while the time for that level is running out.

Anyways, 2 of them should be enough for a month worth of playing around.
I tested the circuit with my V100GT (Goldtop copy with P90s), and this time everything worked OK at 46vDC, but... it doesn't sound that great. Too much mids.
This made me consider simply copying some combo schematic instead of fiddling with a circuit until it sounds good, since I won't have much free time for that once I start on my new job in a couple of weeks.

[UPDATE 3]
Nevermind that last part. I had the wrong speaker plugged in and took me some time to figure it out.  :duh AND I fried another TDA damn, these things are dying easier on my hands than MOSFETS!
I also changed the gain resistors on the TDA2050 (which are now the same values from the datasheet), and I added 2x 1N4148 clipping diodes on it's input.

That's really neat! I accidentally a Jensen :lmao:

This makes me consider buying that pair from the photos, and taking them to be re-coned the same way they did to mine. They're reasonably priced IMO: 60,00$ BRL for the pair, which is about 30,00$ USD.
There's even another pair of Alnico Philips speakers going for 50,00$ BRL... Hmm.

I even happen to have a 10" woofer here, but it sounds like crap with the guitar. It sounds really mid-range-y and dead. Maybe it's because I don't have a box for it, but still, it shouldn't sound like that for the size. I might do the sweep test with it tomorrow and post my results.

Quote from: Littlewyan on July 08, 2013, 12:33:58 PM
Well the TDA2050 datasheet states that the supply voltage is 25V? So does that not mean it would push out 32watts at 25volts?

It actually says +/- 25v, which means a symmetrical supply of +25 and -25v (50v).

Since you're looking for not-so-loud amplification, you could use a TDA2030 instead of a TDA2050. It's used in most 10W guitar combos out there, and it can handle 24v without any problems (max voltage for it is +/- 18v or 36v).

Quote from: Roly on July 07, 2013, 12:06:34 PM
There are a pile of freeware signal generators, but to test your loudspeaker an audio sweep generator is more useful than just a spot signal generator.  I've downloaded this one and a) it works, and b) didn't seem to virus or crash my system.  Your computer sound card may well have enough grunt to drive the speaker directly for this test.

I did the test but I'm not sure if my results are correct.

It seems that this speaker reproduces the frequencies of 130Hz and 3,5kHz a little louder than the rest, and it drops at about 17kHz (I can hear up to about 18kHz on my headphones, so I'm pretty sure it's not my ears).

---

Just for fun, I made this sample recording the same riff twice (even tho I kinda mess up in the rhythm because of soundcard delay), only changing the tone from Maximum to Minimum. I've used the Philips speaker for all the tracks I recorded so far.

https://soundcloud.com/corvolino03/stereo-test

It may not be a guitar speaker, but it's pretty damn good IMO.

Quote from: Roly on July 06, 2013, 01:32:42 PM
Method A - look at the specs, "fo".

Method B - take it out of the enclosure and sweep it from, say, 20Hz to 200Hz, and somewhere in there it will go crazy as it resonates - that's the free air resonance.

Method C - since what we actually want to know is the high cutoff, measure it directly by sweeping the speaker in the enclosure, say 1kHz - 10kHz, and note the frequency it drops the bucket, that will be the high cutoff (or your ears, whichever comes first).

I have no idea how to do that, and all I found about this speaker were these pictures of a pair of it being sold in MercadoLivre (our version of Ebay, but not as reliable), which are in bad shape but have the original cone in them:

http://img843.imageshack.us/img843/69/l0yb.jpg
http://img833.imageshack.us/img833/2289/mxml.jpg
http://img191.imageshack.us/img191/6752/tlm7.jpg

And here's mine on it's temporary "home":

http://img835.imageshack.us/img835/8003/nvep.png
http://img194.imageshack.us/img194/7173/8p7u.png
http://img834.imageshack.us/img834/164/aljr.png

Quote from: Roly on July 06, 2013, 01:32:42 PM
The ground for the preamp looks good, but that Zobel ... oh dear, you don't seem to be getting the point here.  The Zobel must go as directly as possible between the output pin and ground pin of the TA2050, not a grand tourissimo via Zagreb.  Where does the 0.022uF now "ground"?

So when I say "short and direct" I mean SHORT and DIRECT.  Capiche?

Wow, I didn't mean to piss you off man. I'm sorry 

Does this look better to you?

Quote from: Roly on July 06, 2013, 08:30:46 AM
Well start off with the free air resonance of the speaker you are using...

I have no idea how to find that. I know nothing about speaker enclosure design, I just put it in a box and if it makes sound, I'm happy with it.

Quote from: Roly on July 06, 2013, 08:30:46 AM
Looking at your layout a couple of points arise.
(...)
I've appended your layout with a modified ground and indicating where the Zobel could be moved.

I'll put the modified layout based on your suggestions (and with a couple other small tweaks) as an attachment.

Quote from: phatt on July 06, 2013, 09:20:02 AM
@*blackcorvo*,
If I can butt in for a mo/
What Program do you use to get those rather neat looking layouts?
Reminds me of old board designs from the 60's.

Carry on chaps,, Phil.

It's called DIY Layout Creator. It's a free software and can be found here:
https://code.google.com/p/diy-layout-creator/