VHT preamp design

[Valvehead]

I know VHT wont give out scems to most people but does any tech here have one for the CL 100 head? Enzo maybe?

Just curious about the layout of the preamp . 4 pre-tubes , wondering if they use half of the first one for the clean channel ?

[Enzo]

Not me. ANy work I have done on VHT was done without drawings

[defaced]

Have you checked the SLO Clone forum? There's some reverse engineered schems of rare high gain amps, ones you can't openly find schems for, on there.

[cminor9]

Have you checked the SLO Clone forum? There's some reverse engineered schems of rare high gain amps, ones you can't openly find schems for, on there.

I hate it when companies don't give out schems. First, many of them are so well built that it would be impossible for amateurs to clone them for less than it would take to just buy one. Schems would provide amateurs an opportunity to learn. Second, how many boutique builders are truly doing something new? We are talking about vacuum tubes here. What isn't derivative to some extent? Not that derivative is bad, mind you, but give credit where it's due. How many boutique builders aren't standing on the shoulders of giants like Fender, Marshall, and the like?

I remember reading once where Andy Marshall (of THD) mentioned that his noise reduction feature on the Univalve is really just a little something he culled from the RDH4. I think more of that transparency is needed, and kudos to him for giving credit where it's due. I don't know about you guys, but no way could I build a Univalve for what I can get one for (about $700-800). Those things are extremely well built.

Just my 2 cents.

[Enzo]

The OEMs are not concerned with amateurs, they don;t care if you clone their products. They do care if you start selling them, but that is a different matter.

ANy engineering depearment who wanted to copy something could simply acquire one of the items and sit a technician down with it to draw out the circuit.

But there are other reasons. One is for patent and trademark protection. Even though we know any circuit can be traced out, part of defending intellectual property is not having made it "generally available." I always wondered when Fender used to stamp "proprietary" on all their schematics but threw a copy in with each amp they sold.

SOme companies protect their franchisees. You want a part or drawing or whatever? See one of our dealers. Need service? We provide a service network to support our products. By handing out service documents they would be undercutting their own service dealers. Me personally, I like to help people, but every repair I tell someone how to do is one less repair I might have on my bench, one less repair ticket to generate income. Not everyone is so willing to give it away.

But one major reason not to distribute diagrams - and I guess this is aimed at amateurs - is that by providing you with the drawings, it can be considered tacit approval of you working in their product. That puts them square in the middle of the liability loop. Your widow then has an easier time sueing them once yuo electrocute yourself. COmpanies don;t build amps as educational systems, they are not trying to teach anyone electronics. They are putting out a product designed to amplify guitar signals.

As a repair pro it certainly inconveniences me when I can't get that Line 6 drawing, or a Nady schematic, or for many a Behringer schematic, but I can see their point

[drewl]

Most of the stuff I have to fix is because there's noone around here that can do it.....
but if I was in say Enzo's back yard I wouldn't feel comfortable asking for schems.

[Enzo]

Actually, I am happy to talk to anyone with a brain and the desire to learn.

[Guitarist]

They say design an amp from the speaker backwards. VHT rules partly because their power amp section is tops. I notice they insist on a 12at7 PI tube. I like lower than 100 mu driver tubes and on every occasion I get to A/B this, players they tend to agree. I've been curious for years what kind (not specific values) of PI circuit is used by these guys. The only thing I've heard is that Steve tips his hat to Hiwatt.

I recently used a 6au6; a pentode --->into a low Z inverting driver; same tube. WOW.

[defaced]

The Deliverance 120 is a 12AX7 cathodyne PI followed by a 12AT7 cathode follower. The D60 omits the 12AT7. Check the SLO Clone forum in the Other Noteworthy Amps sections for schems.

Here's my question: what does that look like? The information I've got on the cathode follower is as follows:

It's an AC coupled Cathode follower. 1K Rk' 22K rk. input cap .022uf Rl 470K output coupling to taste. output loading resistors depend on what tubes you will use.

I've only read about this kind of setup, but would like to try it in one of my builds. Would anyone have a starting place for this kind of phase inverter and driver? Maybe a schem of an amp that has used this setup.