Metropoulos Forum

I finished this amp a few weeks ago and I have to say that for me, this circuit is my all-time favorite!

The challenge to myself was to build it in a JTM45 chassis! I used 2 KT88's instead of stock quad of KT66's

The preamp is almost bone stock. I went through a few modifications as the build progressed and it culminated with using some mustards as the couplers.

I present you Cinaed! Born of fire......

Part 2!

Part 3!

Used Torotor type power switches:



Finished with Mallory 150's:





Now with mustards:

Part 4

Put it in a Mojo shorty headshell:









I am using a home made 16 Ohm resistive attenuator that I assembled from a gutted Power Soak and a Rockit "Chicago" Pine open back 2x12 loaded with a Scumback J75LD and Scumnico. It sounds righteous!



And a quick clip:

https://www.youtube.com/watch?v=TStx6upRb3g

Some technical specs:

PT: Heyboer Metro Spec. 505B+ on the plates under load.

KT88: Winged =C= (i have one pair left of these for the future)

Choke: Hammond 194G, 3hy, 250mA

OT: Classictone 40-18067, with 4, 8, 16, and 100v tap

Filtering: B1+ 32uf, B2+ (screens)16uf, Phase inverter 32uf, preamp and cathode follower 32uf. I used two F&T 32+32 in series/parallel for B1, used two TAD 32uf in series for B2, F&T 32+32 for PI and preamp.

Screen resistors: I ended up with 3k as my favorite value. Just the right amount of squish and not too much ghosting.

V1 cathode: 820r/100uf

Mixer: Stock values were kept, 270k-270K/560pf

Tone stack: I settled for 390pf treble, 51k slope, .022, .022 (i didn't get a fresh picture before I put it in the head shell)

Bright channel: 62pf bright cap on Volume pot

Step down resistor between screens and PI: 6.8k and 4.7k in series for a total of 11.3k. I played with this value a lot until I was happy with the feel and tone. I didn't get a final pic before I put it in the head shell.

On the power section, The double pole switches the AC high voltage before it goes to the rectifier. This is much easier on the switch. I didn't use a snubber.

Just beautiful work!