Two Rock Classic

[keithrick]

Nice pics, Looks like Tant's on the bright and mid switches.

[brownnote]

Nice pics, Looks like Tant's on the bright and mid switches.

I was thinking they looked like dipped ceramic, Panasonic maybe.

[keithrick]

Ahh, your probably right. They look the same as the caps on V1 and V2.

[glasman]

The filter caps look like sprague atoms, according to mouser the atoms are not RoHS compliant...... maybe they are something else.....

[brownnote]

The filter caps look like sprague atoms, according to mouser the atoms are not RoHS compliant...... maybe they are something else.....

More proprietary components no doubt.

It's my understanding that BMI make the Atoms for Vishay/Sprague, the last time I spoke with them they said they could do a run of custom label caps, RoHs was optional (and more expensive).

[glasman]

The filter caps look like sprague atoms, according to mouser the atoms are not RoHS compliant...... maybe they are something else.....

More proprietary components no doubt.

It's my understanding that BMI make the Atoms for Vishay/Sprague, the last time I spoke with them they said they could do a run of custom label caps, RoHs was optional (and more expensive).

Good information. I am pretty sure that Mojo was dropping them in favor of TAD and Illinois.

[greiswig]

Is that a bypass cap on the PI tail resistor?

Yes it is! Means, that the actually presence internal is fixed at '10'.

The Contour control is similar to the VOX cut control operating between the PI's plates - the small 'Orange' below one of the 'Big Blue', what's presumably a 2200p going to a 250K log. pot as the Contour.

Larry

Larry,

There are at least a couple of us who would really appreciate a detailed explanation of this Contour circuit: is it a combination of a resonance and presence control, or what? Any and all detail you have, I for one would appreciate hearing more.

Best,

[novosibir]

There are at least a couple of us who would really appreciate a detailed explanation of this Contour circuit: is it a combination of a resonance and presence control, or what? Any and all detail you have, I for one would appreciate hearing more.

That's easy explained. The Contour is kinda Presence control (not Resonance) and is operating like the cut control in a VOX AC30, only reversed connected to the pot (wiper & output lug), so that when turning the pot CCW the highs are disappearing.

Since the 'new' Presence doesn't 'add' highs, but only is taking off highs, the previous Presence now may be dimed internal, what simply is done by bypassing the 390 ohms R below the 24K tail resistor with the usual 1µF presence cap.

This kind of a Presence control I'm also using in my DINO amps already over 10 years now, look here:

[img:800:533]http://www.larry-amplification.de/dino9 ... 001-01.jpg[/img]

From the two yellow .047 coupling caps next to you (where on its left side the orange & green wire are going off), the right leads are connected to the PI's plates, but additional from one connection a cable, from the other a .0022 cap is going to the 250K log. Presence pot. Quite simple!

But name it "Contour" instead of Presence, then already it seems, that you have something 'special' in your amp

Larry

[glasman]

The only picture I have seen of the contour circuit looked like a full on wired presence cuitar (1uf cap across the 390 resistor) and a VOX cut circuit that was copied from an AC30. I think the AC30 (or maybe AC15) were the first amplifiers to make use of the PI cut ccircuit.

A .001uf in series with a 250K pot betweeen the PI output couplers and voila you now reinvented the VOX cut circuit. FWIW, Ken Fisher and Komet also used this circuit..... so did matchless and a HOST of others.

Take a look at the AC30 schematics available. Pretty simple

Contour just sounds COOLER than cut....

Gary

[glasman]

novosibir... we were typing at the same time.

[novosibir]

Contour just sounds COOLER than cut....

That's one way, to dazzle your customers

But whether it sells some more amps, is another question

novosibir... we were typing at the same time.

Also easy explained: Telepathy

Larry

[ayan]

And of course, the mandatory disclaimer: no one will have the complete picture on TR amps, or any Dumble-related matter bar none, unless they read this:

http://thegearpage.net/board/showthread.php?t=331325

I have to admit, it is entertaining.

Gil

[Normster]

And of course, the mandatory disclaimer: no one will have the complete picture on TR amps, or any Dumble-related matter bar none, unless they read this:

http://thegearpage.net/board/showthread.php?t=331325

I have to admit, it is entertaining.

Gil

That thread has enough material for a full-season sitcom.

[ayan]

That thread has enough material for a full-season sitcom.

You got that one right, Norm. Screw the writer's strike, who needs them?

Gil

[v00d00blues79]

heh heh... I started getting nauseous around page 30...


Andy