Supercharging a V8

[Verne Andru]

While I went with a 3 knob tone-stack, there are various 1 and 2 knob versions here you can try:

http://amps.zugster.net/articles/tone-stacks

[Wayne2]

Originally Posted by Verne Andru

While I went with a 3 knob tone-stack, there are various 1 and 2 knob versions here you can try:

http://amps.zugster.net/articles/tone-stacks

I think that site has malware on it.

I'm thinking maybe to increase C9 to let more highs jump around the circuit, then when turning clockwise I'd be able to dump more mids to ground without turning the whole signal to mud. I can always scoop it more in the effects loop if needed but the way I have it now the mids are just so overpowering I have the eq pedal maxed out on mid scoop. I'd like it to be more natural if possible, so maybe I could eliminate the eq pedal or put it in front to tweak how I'm hitting the disortion.

C10 I plan to increase a little and C12 I'm not sure about. I still don't understand how C12 adds midrange honk. If anything, it would seem it takes high end out of the signal path, but I'm sure I'm missing something. I keep putting off ordering a book because I have another book to read first, but really I'm just becoming an illiterate bastard.

[jrcorp]

Originally Posted by Wayne2

I'm thinking maybe to increase C9 to let more highs jump around the circuit, then when turning clockwise I'd be able to dump more mids to ground without turning the whole signal to mud. I can always scoop it more in the effects loop if needed but the way I have it now the mids are just so overpowering I have the eq pedal maxed out on mid scoop. I'd like it to be more natural if possible, so maybe I could eliminate the eq pedal or put it in front to tweak how I'm hitting the disortion.

C10 I plan to increase a little and C12 I'm not sure about. I still don't understand how C12 adds midrange honk. If anything, it would seem it takes high end out of the signal path, but I'm sure I'm missing something. I keep putting off ordering a book because I have another book to read first, but really I'm just becoming an illiterate bastard.

I admire you for trying to understand and work with the existing circuit, but I can say that after doing Verne's mods on my V5 I've seen a lot of improvement. I don't remember what you've done so far or what state your amp is in now, but I started from stock and trusted Verne all the way so far, with good results. My understanding of circuits is limited, but to quote the mod schematic, "...C9 adds harshness and C12 adds midrange 'honk'..." If that's right, increasing C9's value isn't going to help the sound. In my opinion, my amp started out sounding very harsh and hissy in the highs, getting much worse with the volume up.

I'm not trying to discourage you or anything. Again, I think it's great that you're trying to figure out and improve the circuit yourself. Eventually I want to be able to work with circuits too, but for me I just wanted to improve the amp. If I made even educated guesses at what to change from the start, I probably would've messed something up.

Originally Posted by Verne Andru

While I went with a 3 knob tone-stack, there are various 1 and 2 knob versions here you can try:

http://amps.zugster.net/articles/tone-stacks

Cool site. For someone without experience in electronics or playing with a lot different amps, would you suggest the same tone stack you used or trying something else? I wouldn't mind trying different options but I mainly want a good end result.

[Verne Andru]

Originally Posted by jrcorp

Cool site. For someone without experience in electronics or playing with a lot different amps, would you suggest the same tone stack you used or trying something else? I wouldn't mind trying different options but I mainly want a good end result.

If you want to mod the tone stack and keep it as simple as possible, the 18 watt 1-knob would be worth a try. It's taken from a Marshall, which is also 12AX7/EL84 driven. You'll be stuck with whatever the midrange frequency is, but that goes for a 2-knob as well.

It's possible you could leave the existing tone pot as-is and create the circuit through a combination of cutting a trace and connecting others.

Worse case you would have to remove that pot and wire a floating one directly to the board. If you're going to do that you could then look at getting a stacked-concentric pot and try one of the 2-knob circuits.

All depends on how ambitious you are. I went over the top because I could.

[jrcorp]

Originally Posted by Verne Andru

If you want to mod the tone stack and keep it as simple as possible, the 18 watt 1-knob would be worth a try. It's taken from a Marshall, which is also 12AX7/EL84 driven. You'll be stuck with whatever the midrange frequency is, but that goes for a 2-knob as well.

It's possible you could leave the existing tone pot as-is and create the circuit through a combination of cutting a trace and connecting others.

Worse case you would have to remove that pot and wire a floating one directly to the board. If you're going to do that you could then look at getting a stacked-concentric pot and try one of the 2-knob circuits.

All depends on how ambitious you are. I went over the top because I could.

I'm not worried about the work. I was planning on copying what you did. I guarantee that my ears aren't as discerning. Being able to manipulate treble, bass, and mids would be awesome, though.

[jrcorp]

I skimmed the thread again to look for a good picture of the wiring for the tone stack, and found discussion of the volume control, as lacking in a V5. Just looking at the schematics, I notice that the volume on the V8 is between the tone stack area and the second section of the 12AX7. On the V5 schematic, there's a 10K resistor that's in about the same place. It's tough to tell, but could I theoretically replace that resistor with a volume pot and wire up the same kind of line out?

The only issue I see is that in the V5, there's a trace/connection before the resistor to the next part of the circuit. I think I would have to take a look at the board.

[Wayne2]

I tried something new tonight. As things stood I had taken out C2, C9, C12, and disabled C10 by clipping one side. What I just did today is I fixed C10, replaced C12 with a silver mica of the same value, and put a 250 pF silver mica in the place of C9 (originally 100 pF). It's not the most beautiful soldering job, mainly because the silver micas are so much bigger than I expected, but fortunately there's room to lay them in there.

Originally when the amp was new I remember liking the effect as I turned the knob clockwise, from 5 towards 10, but agreeing with Verne that the signal quickly became unacceptably muddy.

My hypothesis is that with a higher value of C9, the highs will pass right through unmolested, and only the mids and lows will have to deal with the other tone caps and potentiometer. I can always cut the highs elsewhere if needed, on the guitar itself or an eq pedal.

The funny thing about this amp (maybe it's just DIY in general) is that everything I do sounds awesome to me the first night and then I come back to it a few days later and I'm not so sure. For now I still don't like 0 through 4, and 5 is too bright and raw, still too harsh sounding. 10 is a calmer signal, with enough highs still intact that I think I'm going to be happy. The eq in the loop is no longer necessary. I even tried boosting and cutting the mids with it and it seems just about perfect with no changes.

With gain now not much happens until 5. I'm thinking the 12AX7 might be more sensitive to mids than to highs. Past 5 it starts to distort like it did before.

One other thing: I've decided the amp likes clean boost in front of it. My guitar has vintage-style pickups and it sounds squawky through the amp unless I put either the ModTone clean boost or the MXR eq with +6 gain in front. I resisted this for the longest time thinking one opamp ought to be enough but I give up. I'd be interested to try a high output pickup but I only have one guitar.

[Wayne2]

It looks like the V8 is being reincarnated as the Ampeg GVT5-110. Changes include Baxandall tone stack, two power modes, no effects loop, no master volume, 6V6 instead of EL84, various speaker out jacks, and uglier cosmetics. Similarities include 5 watts, 12AX7, and Celestion Tube 10 speaker. MF already has it listed as a Best Seller even though it doesn't come out until 1/2012, and it will be $399.

At any rate, it's good to see SLM Crate/Ampeg still in the game.

[dcindc]

trading on the ampeg look and name.

Missed the price mark by hundreds of dollars....

[Verne Andru]

It's like 2 steps forward and 1 back.

I like the void-free cabinet over the V8's MDF. Tone stack is also an improvement as is the 2.5 watt mode. Speaker is the same. While I love the tone of a 6V6, it isn't nearly as gnarly as an EL84. But I would seriously miss the V8's gain/vol combo and FX loop.

It's also kinda pricey considering you can get a dual 6V6, 2 channel Super Champ XD all day long for $299 or less.

[Wayne2]

Originally Posted by Verne Andru

It's like 2 steps forward and 1 back.

I like the void-free cabinet over the V8's MDF. Tone stack is also an improvement as is the 2.5 watt mode. Speaker is the same. While I love the tone of a 6V6, it isn't nearly as gnarly as an EL84. But I would seriously miss the V8's gain/vol combo and FX loop.

It's also kinda pricey considering you can get a dual 6V6, 2 channel Super Champ XD all day long for $299 or less.

SCXD is down to $199 on MF now, yet I can't find it on Fender's site. Does this mean it's going away? GAS attack. Craaaaap.

GP article says the Ampeg is made in S. Korea.

[Verne Andru]

Funny, the only Champ left on Fenders site is the Vibro. Perhaps they have discontinued it? Doesn't make sense since it was a really good seller for them. Maybe they're clearing the decks for something even better? We can hope.

If you're hankering for a SCXD, you can get it here for $189:

http://altomusic.com/shop/Fender-Sup...-_pid105792.am

And a M123 price match should bring it down to around $150.

Historically Ampeg tried to build uber clean amps. With a single preamp tube in the new one, they either have an opamp like the V8 or they are really clean. The V series they're reissuing tend to be at the bottom of the historic desirability scale, but I'll wait to check them out at NAMM next month before I draw any conclusions.

[Wayne2]

Update: Got bored so I changed the speaker to a Fender special design 10 inch 30 watts 1" voice coil and a 15oz ceramic magnet and ditched my pedals and the Jensen MOD10-70. Low watt speaker is the way to go. Loving the Crate again.

[jrcorp]

Originally Posted by Wayne2

Update: Got bored so I changed the speaker to a Fender special design 10 inch 30 watts 1" voice coil and a 15oz ceramic magnet and ditched my pedals and the Jensen MOD10-70. Low watt speaker is the way to go. Loving the Crate again.

I haven't been playing for awhile, but I will be making a parts order from Mouser soon so I'll definitely include some modding parts. I bought some old Alnico off TGP, assuming it's low wattage but not sure. I guess it depends on what you want, but some Fender speakers sound good to me.

Is that a Crate PCB in your avatar? I remember my V5 looking similar. I assumed you had a V5 as well, but your list of gear looks great.

I had planned on making a head cab for the amp, putting in the same tone stack Verne used, and possibly adding an effects loop. If I get the head cab built, I wouldn't be as afraid about space. We'll see!

[Wayne2]

Originally Posted by jrcorp

I haven't been playing for awhile, but I will be making a parts order from Mouser soon so I'll definitely include some modding parts. I bought some old Alnico off TGP, assuming it's low wattage but not sure. I guess it depends on what you want, but some Fender speakers sound good to me.

Is that a Crate PCB in your avatar? I remember my V5 looking similar. I assumed you had a V5 as well, but your list of gear looks great.

I had planned on making a head cab for the amp, putting in the same tone stack Verne used, and possibly adding an effects loop. If I get the head cab built, I wouldn't be as afraid about space. We'll see!

Yes it's the board from my V8. Kind of looks like a monster to me, with the tube sockets being the eyes. I had to pull it because I wasn't able to reach some of the components to solder them. The two tan lumps near the bottom are the silver mica caps I added. (closeup here)

Alnico should be nice; it's just a space issue in the V8. Verne got around it by front loading his, but it's a fair amount of work.

Thanks about my gear list. Grand strategy lately has been to buy mainly MIA analog stuff that can teach me something.

[jrcorp]

Originally Posted by Wayne2

Yes it's the board from my V8. Kind of looks like a monster to me, with the tube sockets being the eyes. I had to pull it because I wasn't able to reach some of the components to solder them. The two tan lumps near the bottom are the silver mica caps I added. (closeup here)

Alnico should be nice; it's just a space issue in the V8. Verne got around it by front loading his, but it's a fair amount of work.

Thanks about my gear list. Grand strategy lately has been to buy mainly MIA analog stuff that can teach me something.

The V8 board looks much different than my memory of the V5 board; I'm assuming the components are better. I'm almost inspired to go through everything and upgrade what I can, thinking about the pots and in/out jacks right now. I doubt I would ever go to the extent that Verne has in adding reverb and tremolo, though maybe someday if I dive into electronics I'll give it a shot. Part of me feels like I would be better off building an entirely different circuit and using the chassis of the V5.

The Alnico speaker I have doesn't have a bell, and I think the magnet is much smaller than that of the Weber speaker. It fits pretty well, with a small amount of clearance between the magnet and chassis. Maybe if I do make a head cab, I'll go about modifying the cab for front loading etc. Who knows.

Nice work soldering those components, by the way. My work looks sloppy by comparison.

[Wayne2]

 

Originally Posted by jrcorp

Nice work soldering those components, by the way. My work looks sloppy by comparison.

 

Thanks. I had just bought the Weller WES51. Light years better than my old soldering iron. Light and nimble and just the right temp to melt quickly but not scorch off all the flux. I wish I had bought that first before pickups, caps, etc.

[jrcorp]

 

Originally Posted by Wayne2

Thanks. I had just bought the Weller WES51. Light years better than my old soldering iron. Light and nimble and just the right temp to melt quickly but not scorch off all the flux. I wish I had bought that first before pickups, caps, etc.

 

I received a new iron as a Christmas gift, but as it wasn't what I had planned on it's still in the packaging. It doesn't have a stand, so I'll have to put together a station/workbench before I feel comfortable doing a lot of work with it. That's good to know, though.

[Muckaluck]

Thanks so much for the thread everyone. I'm chiming in for the first time here as I just bought a Palomino. Does anyone know of a tech in the Toronto area who is doing mods with these? Is anyone taking mail in orders for them?

Thanks,
Dale.

[Wayne2]

Welcome Dale and congratulations.

[superartbox.com]

Look very nice. Good job, good painting.

[jrcorp]

Random but I was at Walmart looking for hardware to mount my license plate and saw for sale a badge that I swear is the same "V8" on these amps in chrome. I'll have to take a picture next time I'm there.

[Wayne2]

Originally Posted by jrcorp

Random but I was at Walmart looking for hardware to mount my license plate and saw for sale a badge that I swear is the same "V8" on these amps in chrome. I'll have to take a picture next time I'm there.

This? http://www.walmart.com/ip/Pilot-Retr...mblem/17217875

cool!

[FinkBrau]

Hello guys, I'm new here and I need some advice!

Back in the days when I was looking for a small practice amp it seemed that the best choice was the V8 Palomino (it was the only one with a "Gain" pot). Problem: I live in France and it was only available in the US.
So I bought one off eBay, the earlier made in USA model.

I've been using an external power transformer since then but now I want to get rid of it. I opened it up, looked for some schematics, and now I'm confused.

It is supposed to be the same schematics as the V5 model. But the V5 model can switch between 110V and 230V. On the PCB there is a writing: 230/240V .25A SB, what does it mean?

On some schematics I read that 230V supply should be connected to pin J10 instead of J12 but J10 isn't connected to the power transformer.

In a bold moment I tried to just plug it on 230V, and of course the fuse blew. So I think I have to swap the power transformer.

Now my problem is that I can't seem to find info on the transformer. I should be able to replace it by the one that's on the V5 but I can't find the replacement part.

So my question is, does anyone know where I can, either find a replacement power supply for the V5 model, or find an equivalent power transformer but that can run on 230V?


Thanks,
Pierre.

[Verne Andru]

Welcome to the forum Pierre. You could try contacting Crate [now owned by LOUD] and asking them how to convert it to run on 230V. IIRC it was designed [or indications show it was designed] to be easily adapted to different power situations but Crate service - which are very good IME - are the people to ask.

Fuses are designed to blow before any significant damage happens to the electronics, so there is a very good chance you may not need much more than a new fuse. Transformers tend to spew smoke and show signs of burning when they go, as the windings will melt. Hammond makes all sorts of replacement transformers and are very well priced, so I'd check with them if you do need a replacement. Usually other components like resistors/capacitors will go long before you melt a transformer. If you didn't smell anything or see anything that appears burnt, you could be okay.

Good luck!