VHT Special 12/20RT low preamp voltages

[audiopete]

I've had a few of these amps where the Mosfet has blown - they go short but the amp works fine with it shorted - just the power level is stuck full on.

I'm wondering if the trem circuit is pulling the voltage down. I'd lift R60 and re-check the voltages. Especially as the original owner reported the trem wasn't working properly.

Lifted R60 - no change. I didn't really get much time today to look further into it.

[J M Fahey]

Yes sorry that's what I meant - power supply.

The plates are on B+1 and the screens are on B+2 so I don't see what you are saying about padding down the screen voltage. The MOSFET is before both of those nodes.

You are right.
I saw Screens on B+2 and had earlier seen the label B+ (assumed it was what they referred to as B+1) which is not regulated and thought this was a screens-only regulator.
Just last week I read about such an amp and it was described as dirty and farty, MP3s confirmed it so I thought it was more of the same

FWIW I have listened to full padded amps , output plates *and* screens, and found them very natural, down to incredible 60V , one more reason to think this was not the case.

In the tests I listened to, sound was described by user as progressively thinner and weaker in a bad way, but recorded samples , keeping recorded and reproduced level the same, sounded exactly the same, so differences could be entirely attributed to Fletcher Munson ear curves.

It was a great eye opener for me.

Iīm not building tube amps at the moment, have my hands full with SS ones (which pay the bills ) but next orders I take will be 2 x 6L6 amps minimum , *with* power regulation.
Never liked small amps, bedroom playing concept scratches me the wrong way, but now Iīll offer a Jack of all trades: an amp perfectly capable of Club / loud rehearsal use, which *can* be turned down if necessary.

[audiopete]

Good luck with that. Hopefully the new found love for tube amps has spread to your part of the world and may you sell many.

[J M Fahey]

Ouch !!!
Kids *speak* about loving tube amps, tube this, tube that, but when they vote with their wallets SS wins by landslide.
Thatīs why I sell so many of the latter and so few of the first.
Oh well.

[audiopete]

Sorry I don't understand why you say ouch? Kidding? Anyway all the best no matter what you sell.

[J M Fahey]

Ouch! refers to what I put in the 2nd line: here everybody dreams, thinks, eats, walks tubes, but then buys SS .

No need to translate AR Pesos to US Dollars because thatīs not the true comparison, the real parameter is how long you have to work to get something.

A typical handmade 50W tube combo with 2 x 12AX7, 2 x 6L6 , 1 x 12" Celestion or Eminence speaker , what in USA would be a Boutique amp, costs 3 to 4 "Mc Donaldīs salaries" , the typical job quality and salary an 18 to 28 y.o. guy can get ..... which by the way is the typical demographics of somebody who hangs a guitar from his neck and plays some Rock.

Since he also has to live, travel, eat, etc. , the masses can dream all they want but canīt afford it.

So they read Ultimate Guitar, My Les Paul, SLO Forum all day and night long , want the latest Bogner, Engl, Diezel, etc. but itīs impossible.

Now I have been making very successful SS amps for ages, way over 10000 of them, for a very reasonable price (100W head + 2 x 12" closed back cabinet for 1 (one) Mc D Salary) so typically they get a paycheck and pay 50% of the head up front which is 1/4 a salary, they can live all month with whatīs left, next month complete the head payment and pick it up, practice at home with any old speaker they have (at bedroom levels of course).
Following month they do the same with the 2 x 12" cabinet.

So they *can* buy mine with no big sacrifice and relatively fast, no credit involved; good because many have "black" (unregistered) salaries.

The sound?
Hereīs a sample of an old very successful model, think "SS JCM800":

The guitar is plugged straight into it, no pedals involved.

[audiopete]

Very nice range of tone. I am impressed. Very good overdrive, as far as I can hear through youtube and a laptop. I also like that you provide amps to people who otherwise would probably never have one. An electric guitar needs an amp. Cheers.

[audiopete]

This amp is fixed and seems to be solid. Turns out it needed a new reverb pot and a new trem speed pot. The trem pot was the original cause of the dead trem and the reverb pot went out later down the road. I don't know what the deal was with the strange voltage readings, but this amp sound and acts as I would expect it to - which is very good, actually. Thanks again for the help.