Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: adamG on January 24, 2018, 07:07:15 am

Title: Garnet Gnome with reverb
Post by: adamG on January 24, 2018, 07:07:15 am: Hi Guys,

I've been working on this amp. For me, it's time to play with SE amp with both vibrato and reverb.
I'll also apply boost/voicing DPDT switch on input tube cathode.

Attached schematic is mentioned/taken from this topic :
http://el34world.com/Forum/index.php?topic=20816.msg220070#msg220070

Could you advice me on several issues?
1.How to switch vibrato on/off,
2.Same issue to reverb. I assume a switch across 470K resistor to ground. Second tube, after rev.tank. Is it ok?
3.What value of plate resistor on 1/2 12AU7 in path to reverb output,
4.Global feedback resistor 10K. To which secondary tap connected,
5.I am not sure about of 4,7M ground resistor on input jack. May I provide "standard" 1M?

Thank you in advance.

Regards,

Adam
Title: Re: Vibro Champ with vibrato
Post by: VMS on January 24, 2018, 01:39:47 pm: answers to 1-3 you can probably copy from this bigger garnet amp:

http://el34world.com/charts/Schematics/files/garnet/garnet_g45tr_late_version.pdf (http://el34world.com/charts/Schematics/files/garnet/garnet_g45tr_late_version.pdf)

4. not sure but use what sounds best
5. 1M should work too
Title: Re: Vibro Champ with reverb
Post by: kagliostro on January 24, 2018, 03:20:57 pm: May be it will be better to correct the title of the thread

from Vibro Champ with vibrato

to Vibro Champ with reverb

Franco
Title: Re: Garnet Gnome with reverb
Post by: sluckey on January 24, 2018, 05:02:15 pm: That Garnet amp looks nothing like a Vibro Champ.
Title: Re: Vibro Champ with reverb
Post by: adamG on January 25, 2018, 12:06:54 am: Quote from: kagliostro on January 24, 2018, 03:20:57 pm
May be it will be better to correct the title of the thread

from Vibro Champ with vibrato

Upss...you're right :rolleyes:
Sorry.
It's changed.

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: adamG on January 25, 2018, 12:27:07 am: Quote from: sluckey on January 24, 2018, 05:02:15 pm
That Garnet amp looks nothing like a Vibro Champ.

You're right.
I've changed the topic.
Sorry.
Is it ok now?

Regards,

Adam
Title: Re: Vibro "Champ" with reverb
Post by: kagliostro on January 25, 2018, 03:09:28 am: That wasn't a big trouble

only I think it will be easyer to understand the argument simply reading the title

Franco
Title: Re: Vibro "Champ" with reverb
Post by: adamG on January 25, 2018, 04:36:24 am: Quote from: kagliostro on January 25, 2018, 03:09:28 am

only I think it will be easyer to understand the argument simply reading the title

Franco,

Is now ok?

Would you have any idea how to fix my issues above?

Thank you in advance.

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: sluckey on January 25, 2018, 07:18:05 am: Quote from: VMS
answers to 1-3 you can probably copy from this bigger garnet amp
I agree with VMS.

4. Connect to each tap. Use your ears to choose which one to leave it on. There's no right/wrong. If you can find out what impedance speaker was in the original amp, then use that.

5. Yes, you can use a 1M resistor. I doubt there will be any difference.
Title: Re: Garnet Gnome with reverb
Post by: adamG on January 25, 2018, 07:27:39 am: Quote from: sluckey on January 25, 2018, 07:18:05 am

4. Connect to each tap. Use your ears to choose which one to leave it on. There's no right/wrong. If you can find out what impedance speaker was in the original amp, then use that.

5. Yes, you can use a 1M resistor. I doubt there will be any difference.

Thank you Steve, very much.

Another, a bit forgotten issue. Is Hammond's reverb driver 22921 ok for 12AU7?
"Standard" application is for 12AX7, right?

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: sluckey on January 25, 2018, 07:43:34 am: 22921 will work with the 12AU7, but it also has to work with the reverb tank input impedance, usually about 8Ω. "Standard" application is the Fender parallel 12AT7 driver tube, but it will work with single triode 12AX7 or 12AU7 also.
Title: Re: Garnet Gnome with reverb
Post by: adamG on January 25, 2018, 08:01:42 am: Thank you Steve.

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: adamG on February 19, 2018, 12:53:21 am: Hi Guys,

Recently, I've built this amp...with full success :smiley:
Reverb is beautiful. I am really happy with it.
Tremolo is not as intensive as in Fendery amps, but for me enough.
TS is absolutely ok. I applied 3 pots of TMB.
I can recomend this circuit with full heart.

When I am ready with head shell, I'll put pics of it.

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: kagliostro on February 19, 2018, 04:13:07 am: At the end which was the schematic you followed ?

Thanks

Franco
Title: Re: Garnet Gnome with reverb
Post by: adamG on February 20, 2018, 12:29:23 am: Quote from: kagliostro on February 19, 2018, 04:13:07 am
At the end which was the schematic you followed ?

I followed those two attached schematics.
g_15tr as the basic one with FS solution taken from g45tr.
As I could see, reverb stage is not very common within SE amps. That's why I was interested in Garnet circuit, much.
Now, I can recomend the amp. If I am asked to build another one, I'll try it with full 12A_7 tube for tremolo stage.
This one is ok, but might be better a bit :smiley:
I also applied Weber's voicing/boost switch. Very good mod!
https://www.tedweber.com/media/kits/maggie_schem.jpg

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: kagliostro on February 20, 2018, 02:05:36 pm: Thanks

Franco
Title: Re: Garnet Gnome with reverb
Post by: adamG on March 20, 2018, 08:54:48 am: Hi Guys,

Recently, I've finished the amp.
So, I share few pics of it with you.
This baby enjoyed me very much.
There're empty holes after previous amp, but who cares?;)

Regards,

Adam
Title: Re: Garnet Gnome with reverb
Post by: shooter on March 20, 2018, 12:52:40 pm: :headbang:
nice build, dually achieved :laugh:
Title: Re: Garnet Gnome with reverb
Post by: adamG on March 21, 2018, 01:09:10 am: Thank you, very much.

Regards,

Adam