5 Watt Amp mods

Tube or solid-state, this section goes to eleven!
User avatar
Turnerguitar
Breadboard Brother
Information
Posts: 110
Joined: 27 Oct 2010, 17:03
my favorite amplifier: Super Reverb/Twin
Completed builds: Super Duper 2-1, Box of Rock, King of Tone
Location: Nashville
Has thanked: 2 times
Been thanked: 2 times

Post by Turnerguitar »

Okay, I'm gonna try the NFB and depth mod. However, I'm having a great time just researching all this and trying different things. SO, would it be fun to try to work in a 6550 in place of the 6v6 if I can get all the transformer information? And what information will I need beside the max heater current?

I already know I'm gonna put a beefier OT in. I'm looking at this one:
OT WSE25.jpg
And I'm guessing I can only use SE OTs and not something like this in my amp?
Marshall OT.jpg

User avatar
Turnerguitar
Breadboard Brother
Information
Posts: 110
Joined: 27 Oct 2010, 17:03
my favorite amplifier: Super Reverb/Twin
Completed builds: Super Duper 2-1, Box of Rock, King of Tone
Location: Nashville
Has thanked: 2 times
Been thanked: 2 times

Post by Turnerguitar »

By the way, I have one of these lying around...
PT 022798int.jpg

User avatar
loudstroud
Information
Posts: 1
Joined: 20 Sep 2015, 23:21
Has thanked: 2 times

Post by loudstroud »

turnerguitar - Sharing the same sentiments about my GVT5-110 and stumbling upon your thread Googling for suggested mod's, I too followed sinner's suggestion of swapping out the C6 coupling cap. Dropped in a SOZO .022. Between that change and finding an excellent sounding old Phillips (USA) 12AX7A in my stash, it brought the amp to life. It's now fun to play through. Has made the difference in keeping it vs throwing it on eBay. Really like the size and tone of what's essentially a tweed Champ w a solid state rectifier and the Baxandall tone stack.

Did you try upgrading the OT? Did it make a noticeable difference?
Attachments
Ampeg GVT5 mod.jpg

User avatar
DZjam
Information
Posts: 1
Joined: 24 Jun 2015, 13:53

Post by DZjam »

Here are some great mods for the Ampeg GVT5...
1. Remove the C5 bright cap. It's responsible for the harsh upper presence.
2. Change the C4 from 1uF to 10uF or 22uF. This will add depth & big amp tone.
3. Change the C6 coupling cap from .1uF to .01uF to keep the lows from getting fizzy when you crank up the volume.

DO NOT SERVICE ANY ELECTRICAL EQUIPMENT UNLESS YOU ARE QUALIFIED TO DO SO.
COMPONENTS MAY STORE LETHAL ENERGY, EVEN AFTER THE AMP IS UNPLUGGED!
BE SURE TO USE CAPACITORS WITH EQUAL OR HIGHER VOLTAGE RATINGS.

User avatar
MoonWatcher
Diode Debunker
Information
Posts: 715
Joined: 28 Jul 2008, 12:27
Has thanked: 41 times
Been thanked: 43 times

Post by MoonWatcher »

loudstroud wrote:Did you try upgrading the OT? Did it make a noticeable difference?
I can only speak for my experiences. I put a Weber WSE15 in a Blackheart Little Giant, and the improvement was unbelievably good.

And whatever OT comes factory installed in the VHT Special Six (yes, installed from the factory :thumbsup) is as good or better than the WSE15. Granted, it's a slight apples to oranges comparison, because the Little Giant has a EL84 but the Special Six takes octals (specifically biased for 6V6 from factory, but can be altered for 6L6/etc.).

The WSE15 is 5K with 2/4/8/16 ohm taps. Not sure how close of an equivalent to the Special Six OT could be found, but it's 9K with 4/8/16 ohm taps. If filament windings from (probably upgraded) PT can handle 6L6 or more (EL34 and similar being much more), something like a 6L6 used with an 8 ohm speaker connected to the 16 ohm tap should give 4.5K.

User avatar
tictac
Breadboard Brother
Information
Posts: 145
Joined: 27 Nov 2008, 07:30
Been thanked: 10 times

Post by tictac »

I'd change that triode connected EL84 to a more conventional pentode connection. To my ears triode connected EL84's sound farty and wimpy, i.e. un-dynamic.....

I'd have the plate connected to the upstream side of that 250 ohm power resistor and the screen connected via a 100 ohm grid stopper resistor to the down-stream side of the 250 ohm.

TT

User avatar
tictac
Breadboard Brother
Information
Posts: 145
Joined: 27 Nov 2008, 07:30
Been thanked: 10 times

Post by tictac »

Oh right 6V6, same mods apply as previous post..... :oops:

User avatar
aharon colman
Information
Posts: 16
Joined: 26 Aug 2016, 22:35
Been thanked: 1 time

Post by aharon colman »

did you try plugging an extension cab?
Aharon

Post Reply