How to Lossen-up a tif amp ?

[hebaton]

Thank you, I did get that and looked around a bit yet, I could not figure how to move the mid slope. Which component will do that ?

[Phil_S]

FWIW, my first reaction was also to suggest reducing the amount of filtering in the power supply. I admit waiting for someone else to suggest it for fear of embarrassing myself . Someone else says go from 80uf to 50uf and that's certainly a good start. Many common guitar amps have power supply filters between 20uf and 40uf. Of course, if it turns out that stiffness isn't really the issue, it isn't likely to help. The words we use in describing amp performance are often not precise and are sometimes misapplied.

Here is a good read that covers the slope resistor. https://robrobinette.com/How_The_TMB_To ... _Works.htm about 30% down the page. In the YBA-1, the slope resistor is R15, 47K.

[JD0x0]

Leave the filtering stock. Add a 'sag' resistor to increase voltage drop in the power supply. You could also replace the choke with a resistor of higher resistance for a similar effect. More sag and lower B+ will 'soften' the amp up.

[Reeltarded]

I am also curious of How to determine the Mid pot range. How would I move the center frequency of the mid pot towards bass just a tad ?

The slope resistor is the one at the top corner of the tone caps.. look at your pots.. follow the wires from the input lugs. There are two identical looking caps and a small treble cap that terminate at a resistor. That resistor is the slope.

Top means (previous to) and corner means (components all attach)

Slope will get you more apparent bass by raising the value. That will also seem to add some treble. Change will be apparent by dropping mid dip another couple dB. This will not move the corner frequencies. There are a couple things you can do otherwise:

Increase bass cap value
Increase a coupler on an early stage
Change the mid control to parallel from series

The first thing gets muddy pretty fast. The second thing might do that as well. The third thing divorces the mids from a Bass Treble stack and then you keep the same ranges but the mids do not interact with the BT tilt.

These things do not make your amp feel spongey.

You can lower the 1st stage filter to 16 or 20u. That will soften the beating. This may require adding a node to your power.

[hebaton]

THanks again everyone. I change all 80UF filter caps to 50UF and got "some " imrpovement. I am interested ine the "sag resistor" option but even after some reading, not sure what value to use. can you help determine that value ?
One other thing I am thinking about is changing fron SS rectification to Tube but, there is no 5V feed from the power tranny, only 6V available. CAN anyone suggest a tube that will work ?

[hebaton]

ONe more question, if someone is familiar qith the MArshall 50watt circuit, what is the use of the 33+33uf cap on the amp ?

Thanks !

[sluckey]

I can't think of any commonly available 6V rectifiers that will work. I would use a separate 5V/3A transformer such as the P-T166MS available from AES...

https://www.tubesandmore.com/products/t ... open-5-vct

Then you can choose from several commonly available rectifiers.

But, it's a lot cheaper to just add a sag resistor. Buy a handful of assorted value 10 watt resistors, maybe 100Ω up to 1KΩ, and experiment.

Converting to cathode bias is cheap and may get what you want.

Or, you could just accept this amp for the beast it is and look for an additional amp.

ONe more question, if someone is familiar qith the MArshall 50watt circuit, what is the use of the 33+33uf cap on the amp ?

I'm not aware of any 50 watt amps that use a 33+33 cap but there are numerous 50 watt Marshall amps. To which one are you referring?

[echuta13]

I'm with sluckey. I would think that a cathode biased output section may get you closer to what you are shooting for as well. You could always make it a switchable mod.

[hebaton]

I can't think of any commonly available 6V rectifiers that will work. I would use a separate 5V/3A transformer such as the P-T166MS available from AES...

https://www.tubesandmore.com/products/t ... open-5-vct

Then you can choose from several commonly available rectifiers.

But, it's a lot cheaper to just add a sag resistor. Buy a handful of assorted value 10 watt resistors, maybe 100Ω up to 1KΩ, and experiment.

Converting to cathode bias is cheap and may get what you want.

Or, you could just accept this amp for the beast it is and look for an additional amp.

ONe more question, if someone is familiar qith the MArshall 50watt circuit, what is the use of the 33+33uf cap on the amp ?

I'm not aware of any 50 watt amps that use a 33+33 cap but there are numerous 50 watt Marshall amps. To which one are you referring?

THe 1987X comes to mind

[hebaton]

I'm with sluckey. I would think that a cathode biased output section may get you closer to what you are shooting for as well. You could always make it a switchable mod.

Just so I get this right, When you refer to cathode biassed output section you are refering to the option of inserting a resistor between the diodes and the filering ?

[sluckey]

THe 1987X comes to mind

Here's a 1987X schematic. I don't see any 33+33µF caps.

https://el34world.com/charts/Schematics ... _1987x.pdf

Can you post a schematic that shows 33+33µF caps?

Just so I get this right, When you refer to cathode biassed output section you are refering to the option of inserting a resistor between the diodes and the filering ?

No. Here's an example of a cathode biased EL34 amp...

https://el34world.com/charts/Schematics ... lubman.pdf

[JD0x0]

. I am interested ine the "sag resistor" option but even after some reading, not sure what value to use. can you help determine that value ?

You can calculate the value if you know how much current you're drawing. Then you just have to decide how much voltage drop you'd want. Most people would probably want to emulate a similar level of drop you'd get from a common rectifier tube, so that's a good place to start.

This calc is for R/C ripple filtering, but it also gives you voltage drop. Since the sag resistor will be before the plate supply for the power tubes, you need the total current draw on the B+ line. You'll likely end up with something in the 100 ohm to 470 ohm range.

https://www.ampbooks.com/mobile/amplifi ... alculator/

[Reeltarded]

50w amps used to come with 33u mains and the preamp had 16u. These are the great sounding amps that ghost.. and it's almost Halloween.. so..

WooOoOoooo

[Reeltarded]

One other thing I am thinking about is changing fron SS rectification to Tube but, there is no 5V feed from the power tranny, only 6V available. CAN anyone suggest a tube that will work ?

This is an expensive and useless endeavor. Seriously. I can give you a billion reasons, but reliability is the 1st. The second is that a GZ goves you enough sag never to notice. You have to run the amp completely dimed and it sounds pretty terrible without a lot of circuit tweaking and very particular tubes, if you ask me.

What bands do you like? You might actually be equating this sag idea with the wrong thing. You might want more gain. The notes hang under your fingers in a completely different way. It takes the torture out of trying to play a Strat.. you already have a useless half a tube.

[hebaton]

One other thing I am thinking about is changing fron SS rectification to Tube but, there is no 5V feed from the power tranny, only 6V available. CAN anyone suggest a tube that will work ?

This is an expensive and useless endeavor. Seriously. I can give you a billion reasons, but reliability is the 1st. The second is that a GZ goves you enough sag never to notice. You have to run the amp completely dimed and it sounds pretty terrible without a lot of circuit tweaking and very particular tubes, if you ask me.

What bands do you like? You might actually be equating this sag idea with the wrong thing. You might want more gain. The notes hang under your fingers in a completely different way. It takes the torture out of trying to play a Strat.. you already have a useless half a tube.

I know exactly what I want and it ins NOT more gain. I want a looser feel with some compression...