From Valve Jr. to Mini Z

[skibum1999]

hello, i'm a new member and have a quick question about amps. I have a Ver.3 Valve Junior and a Dr. Z Mini Z schematic, and was wondering if I could simply change the component values of my VJ and tranny (is a tranny change necessary for V3 combos?) and have a Mini Z sound. Also, the Mini has 1 fewer power supply capacitor, can i replace mine with a jumper?

[sliberty]

As I remember it, the two schematics are very similar, but without seeing them both, its hard to say what changes you would have to make to convert one to the other.

But defintely DO NOT replace a filter cap with a jumper. In fact (no offense meant), that question itself makes me wonder if you are up to the task.

It is possible that with the right changes, the VJ might sound similar to a Mini-Z, but unless you can get the trannies that the good Dr. uses, it may never sound the same. Besides, the VJ is an inexpensive amp - if you try to turn it into an expensive amp, it will cost you a fair amount of money. Is it really worth it?

[skibum1999]

haha yes you're probably right about the power supply cap...thats why i asked first after all. I have a picture of the Mini Z chassis, its a $40 Heyboer Champ OT, so $$ isn't really an issue. But I think if I replace the smaller resistors and caps, and the OT, I should certainly get closer, no?

[Structo]

But I think if I replace the smaller resistors and caps, and the OT, I should certainly get closer, no?

I think that sliberty is very astute with his observation of your abilities.
What do you mean by the "smaller resistors and caps"?

Not trying to be rude here at all.
A tube amp isn't something you just jump into and start poking around in.

Although I am not familiar with the Valve Jr., most tube amps have power supplies that provide very high voltages that can kill you.
Even when the plug is pulled from the wall, the filter caps can hold a charge that can be lethal.

So if you want to learn how to work on a tube amp, start reading up on electronic theory and familiarize yourself with how these circuits operate.
This is really a safety issue that will prevent you from making a terrible mistake that can cost you your life.

[skibum1999]

smaller is a bad word, true...i mean resistors affecting the bias of the tubes, tone circuit, input capacitors, etc.

[CaseyJones]

Follow the magic link:

http://www.sewatt.com/

Those guys make a sow's ear into a silk purse "all day and all night". Except it's more like servin' up hog's assholes and tellin' everyone it's calimari...

[Structo]

That site seems to be down.

[CaseyJones]

That site seems to be down.

Awww... darn it! That explains the strays wanderin' around, though.

Hey SkiBum, do some readin' and find out what you're gettin' into. It ain't rocket science but it ain't like makin' a peanut butter sandwich, either. A peanut butter sandwich won't give you a shock you'll never forget. There's over 600 volts inside a Valve Junior, want to meet every last one of 'em?

The peanut butter sandwich analogy doesn't work if you're allergic to peanuts.

[sliberty]

haha yes you're probably right about the power supply cap...thats why i asked first after all. I have a picture of the Mini Z chassis, its a $40 Heyboer Champ OT, so $$ isn't really an issue. But I think if I replace the smaller resistors and caps, and the OT, I should certainly get closer, no?

Most likely, it will get you closer. But I suspect that with the cheap chassis (yes the chassis makes a tonal difference too), and the miniature components that are on the VJ board (especially the caps) that the amp would need a complete overhaul to make it sound really good. Some have replaced the entire circuit board with a hand wired board, loaded with high quality parts, and replaced both trannies with appropriate replacements, and STILL not quite nailed the tone of a nice boutique amp.

My opinion is that the VJ sounds like dirt when it is stock. That's just my opinion, and hopefully it doesn't come off as offensive to anyone. I could build a better sounding amp from scratch for, say, $200-250. I realize that the VJ costs $129, so I am not saying it isn't a bargain, just that it's a bargain I don't want to play through. But, if you simply want to tinker with tube amp circuits, I suppose it is a cheap entry point for that purpose.

If you decide to do anything with it, please be careful. Study the safety tips on how to work inside a tube amp, and ask some questions about how to apply those saftey tips, and then study them some more before you take this on. We want you to be around long enough to tell us about your experience in modding the amp

[benoit]

But I suspect that with the cheap chassis (yes the chassis makes a tonal difference too)

How so? Other than maybe being a little more sensitive to vibration, which could be a problem for any microphonic parts, what difference does it make?

[sliberty]

Chassis material can have an impact on stray capacitances and grounding. It can also provide better or worse isolutation between the trannies (on top) and the circuit (underneath). In extreme cases, oscillations can be due to chassis vibrations (as you suggested) as well.

[brewdude]

I think the Valve Jr. is the perfect gateway drug. Who cares if my VJ nails any boutique amp's tone, or not? It's a great learning platform. I would not be adventurous enough, without the experience gained from rebuilding my VJ (many times), to embark in the more complicated (and more rewarding) builds such as the D'Lite, that I have been tweaking slowly.

Plus my VJ combo is a great little practice amp. Although, the only things that are original are the chassis, cabinet, PT, and power switch. The circuit barely resembles the original. Plus with the additions of a VVR and MV, I can get great low volume tone without waking the wife and kids.

Is it in the same league as some of the other amps? No way. But, Its not bad for fried hog's asshole, even if you call it calamari.