reverb amplifier

[dhuebert]

I have had a few requests lately for a reverb and tremolo guitar amp, so with that in mind I have been developing this schematic. It is an amalgum of a few other designs. If anyone has any comments to make I would be grateful



Don

[Gingertube]

Don,
That should work quite well.
I assume that 0.002uF cap on the output is a typo and you meant 0.02uF.

You may be lacking a bit of reverb drive although the 12AU7 is a fair bit "gruntier" than the parallel sections of a 12AT7 usually used - so may well be OK.

I tend to use the London Power Push Pull Reverb Drive Transformer with 12AT7 rather than the 'traditional" single ended driver you show - its just sounds smoother and cleaner to me.

Also the 4 series reverb tanks are the short ones (I think) - much easier to find a place for them in the amp chassis but I have found that they just can't match the 9 series long spring units for sound.

If you go to the Accutronics webpages there are example (shudder) Solid State Reverb Driver circuits. The Current Drive example actually performs really well so thats a cheap but good performing alternative to a driver tube + driver transformer - if you have the low voltage power supplies available. If you have to add power supplies then their low cost is not quite as low cost any more.

If you keep the reverb driver as shown one option available to you is to use the other 12AU7 section to drive the Baxandall Tone Stack instead of the 12AX7 section shown. Baxandalls like a lower impedance drive than the "tranditional" FVM (Fender Vox Marshall) Tone Stack so a 12AU7 section with a 22K or 27K load resistor would be a more powerful driver for the tone stack. That will loose you a little gain but the circuit shown won't go to cranked Marshall territory anyway and there would still be more gain than say the "blackface" fender circuit which is the icon of "clean".

Just some random ravings for your consideration.

Cheers,
Ian

[dhuebert]

I'm just reading the above over and find some good advice, which of course I didn't follow any of it.

A couple of nights ago the amp was tested as is by a local pro and declared good.

The preamp is the only thing I'm not quite satisfied with. Two stages of 12AX7, Hmmm, this is supposed to be for a country band and dosen't really have a clean mode. I'm thinking of changing it to 12AT7 without cathode bypass, but we'll see what the customer thinks.

use the other 12AU7 section to drive the Baxandall Tone Stack

I can still do this but make the 12AU7 a direct coupled cathode follower. I was not happy with the unused section.

Also the 4 series reverb tanks are the short ones (I think)

No it's a 15 incher.

Anyways, I don't think I'll do another one of these, I think I spent ~30+ hours soldering it together, What a marathon!

Don

[4-CHANNEL]

Hi,
I think you take a try on the Baxandall NF type tone control instead of RC type, this type can give more " soft " and realistic sound. The harmonic distortion is much lower than RC type.

[erichayes]

Hi guys,

I don't want to pick nits, but that's a twin T, rather than a Baxandall tone control configuration. The two are very similar, but the Baxandall uses a tapped treble control (currently constructed with unobtainium) to lessen its effect on the upper midrange frequencies.

That being said, the twin T is a vast improvement over the FMV (or FVM, depending on who your favorite Brit amp maker is) totem pole, where every control interacts with the others . . . unless that's what you want.

[Geek]

Hi,

Here's a circuit capable of real low noise and good smokin' drive to a tank:
http://geek.scorpiorising.ca/GeeK_ZonE/ ... pic=3551.0

Uses a real inexpensive dual section tube, too - 6JT8.
(5751's not seeded to incorporate into your circuit)

Cheers!

[4-CHANNEL]

Could anyone tell me where to get reverb tanks, ( spring one ) not ICs.

Thanks.

[Geek]

www.tubesandmore.com

[4-CHANNEL]

Got it, Thank You.