Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on June 16, 2024, 05:11:54 am

Title: MAR-CHAMP
Post by: TIMBO on June 16, 2024, 05:11:54 am

Hey guys, This https://www.aggh.net/discussion/index.php?topic=51724.msg581099#msg581099
Got gutted last week, due to the lack of interest on my part.
It's now marshall 2144 preamp, champ power amp kinda.
(https://i.imgur.com/c0inqUQ.jpg)
(https://i.imgur.com/XBHvhO2.jpg)
(https://i.imgur.com/SRDArX2.jpg)
All fired up well, haven't had a chance to chank it
(https://i.imgur.com/ciki2JA.jpg?1)

Title: Re: MAR-CHAMP
Post by: sluckey on June 16, 2024, 05:33:31 am

Neat and tidy as usual!   :thumbsup:

Title: Re: MAR-CHAMP
Post by: Latole on June 16, 2024, 09:54:34 am

Very nice job.

Title: Re: MAR-CHAMP
Post by: tubenit on June 16, 2024, 10:46:50 am

Man, you are always coming up with such cool stuff!   Thanks for sharing, Tubenit

Title: Re: MAR-CHAMP
Post by: TIMBO on June 16, 2024, 02:20:43 pm

Thanks guys.
I have a spare hole in the control panel...
Is there a way to add a presence control in an SE amp?

Title: Re: MAR-CHAMP
Post by: passaloutre on June 16, 2024, 02:37:31 pm

Yes, negative feedback can go to the cathode of that final triode stage.

I’m curious how you like the footswitchable boost on the first stage?

Title: Re: MAR-CHAMP
Post by: sluckey on June 16, 2024, 03:14:23 pm

Quote from: TIMBO on June 16, 2024, 02:20:43 pm

Is there a way to add a presence control in an SE amp?

Here's one way. Just play with the resistor values and I bet you will come up with something useful. I suggest to first add the NFB loop and get the phase sorted. Then convert to the presence circuit.

Title: Re: MAR-CHAMP
Post by: shooter on June 16, 2024, 05:03:32 pm

Quote

Is there a way to add a presence control in an SE amp?

for the alternative SE amp view;


plug into a Marshall full stack
move the guitar closer to the speakers, your presence will be soon known  :icon_biggrin:

Title: Re: MAR-CHAMP
Post by: TIMBO on June 17, 2024, 02:46:09 am

 :l2:

Title: Re: MAR-CHAMP
Post by: TIMBO on June 23, 2024, 02:53:21 am

Hi guys,
My stunt guitarist has had a bash and has given it a low rating.
The LOW input was given a 5/10 sounded good but when cranked didn't quite hit the mark with a smooth overdrive.
So the HI gain input was 1/10 with the sound "fracturing" at low volume and when the boost is engaged it would only sound OK at a very low volume.
Comparing the two circuits and voltages https://www.aggh.net/discussion/index.php?topic=54528.msg610886#msg610886 (https://www.aggh.net/discussion/index.php?topic=54528.msg610886#msg610886)
So my starting point was to drop nodes C and D to get a similar voltage to the preamp valves with an increase to the dropping resistor between nodes B and C to 20k
Even with this increase voltages and still a touch high.
I'll have a play with this with a thought to use an AT7 or AY7 in V1