The Amp Garage

Your updated schematic looks great ! The only error I see is that C23 should be 30uF. See you building A "old" JK, the new ones are similar but no diodes and have a boost funktion. Would that boost be the mid-boost from the schem on a push/pull Bass pot? Implementing the presence on the Gain pot is...

Your updated schematic looks great !
The only error I see is that C23 should be 30uF.
See you building A "old" JK, the new ones are similar but no diodes and have a boost funktion.

What you like to know ?

CoffeeTones wrote:Very similar to the Dr Z Therapy. [img760]http://medias.audiofanzine.com/images/n ... 872674.png[/img]

Yes that was more and less the same amp
Dr Z is using a ppimv instead of a pre-master.
Guess is Dr Z is more rock n roll

The main effect is cutting HF, very similar to a low-pass filter. I've never seen this before either, but it's an interesting trick for trimming highs, and the corner frequency is easily varied by adjusting the size of the cap. The trace below is with and without a 47p anode-to-anode for two cc gai...

It's hardly different from LNFB achieved by connecting the small cap from the second stage anode to the second stage grid. The reason is because there will be a wide-open path from the anode of the first stage through the coupling cap (which is much larger than 47p) to the grid of the second stage....

When I think of feed back I understand that to be from an output to an input. This clearly bridges two outputs. I don't see how that constitutes feedback. It seems like it would create something like mixing/balancing/co-mingling of the two AC components. Would these signals be out of phase? I think...

On the Fender Twin 6G8 amp, you will find a "snubbing cap" at the base of the LTPI plate resistors. It's there to help prevent parasitic oscillations. It is a 47pf cap and I am thinking the picture you are showing has a 47pf cap there also. http://el34world.com/charts/Schematics/files/fender/Fender...

Seems that amp. Well the PA is clearly a cathode bias. and PI is clear, 100k for each Rp, 1k2 and 47k below, going to 47nF to 220ks. Before seems like: 220k into 1k5//1uF 22n to Gain 100k into 820R//1uF TS à la fender with 100k slope and 2x22nF caps. Volume to 22nF to PI. The 47pF gives some negati...

dorrisant wrote:What model of amp?

I believe is A Morgan RCA35

Be aware that many Engl schematic have been of "generic " type and not a complete schematic.

I think he is referring to the silver mica between what appear to be the plate loads for the first two stages. just before the tone stack Yes! Between the first plate loads resistor (220K) and the second (100k) there are a silver mica between the gain stages. I have never seen this done before, so ...

I was looking at Morgan amps and of course I did a search to see if there was some pictures of the inside.
[img2448]https://ivanrichards.files.wordpress.co ... 35-005.jpg[/img]

Have never seen a cap between two gain stages like on this one.
Any ideas as what is going on ?

I can see where you're coming from. Didn't Ei buy Telefunken's equipment but make lower grade valves? EI made good tubes for a time, but their factory had an annoying habit of getting bombed and eventually closed. Also, the machinery got old and out of tolerance and was not properly maintained... Y...

Btw., I verified my build against the layout as kindly made available to me and the layout still seems to be missing the coupling capacitor after V1B. Niki Hi Niki ! That sound odd to me. I probably have all the schematic and layout that have been on the web, yes they have all errors or are not com...