Playtime new idea on severe amp control


Junior Member
From Alan on Audiochews

10:00AM edited 10:01AM Flag
Hi Col, thanks for your comment!

We played a track by PanSonic from Katodivaihe (Cathodephase) called Virta 1. This EP is to all intents and purposes a hifi torture fest, and is interesting if you enjoy electronic music. The bass was literally propulsive, I don't think I experienced anything like this before. Vibration of the wall, sofa, the air between my hands. It's a good thing my neighbor was out! Yet Colin and I could still converse without raising our voices.

Using the amp without its feed forward wiring first, we watched in amazement as the twin aluminium bass drivers performed acrobatics and wondered how the sound wasn't distorting in any appreciable way (I had never seen then move until now). This sound very much the same as the M-100T I had here for a while. Colin smiled the satisfied smirk of a designer who knew he has knocked out out of the park - again.

Adding the feed forward was fascinating. The drivers appeared to barely move in comparison, the twisting at the end of their travel was utterly eliminated. So strange to see a visible manifestation of this feature!

As for the sound, it did that thing you might remember when you first heard a SECA amplifier. That wonderful infusion of subtle detail, superlative speed and convincing warmth, the sound now coupling with and driving the room like you'd not heard before after listening to transistor amps with dampng factors of around a hundred; now a SECA with a DF of thousands could intimately connect you with the music. A performance rather than simply music. Similarly this amplifier can do even better and above a SECA, but at any volume level. This in turn throws the sound image forward and spreads it wider.

We also played 'Love turns forty' by Vienna Teng, which is the other track I think Colin refers to. It's a lovely detailed recording with a double bass. And Lia Ices 'Daphne' for that matter, which also features a string section. Colin is right, the wood body of the cellos and bass was so vivid as to really be striking.

The aspect I'm appreciating most right now is the bass depth and power being present at low volume, the system coupling to my rooms acoustic. The extra control finally sates a desire for scale and presence at any volume, full musical body and texture at low volume with huge imaging. Yet at high volume it appears not to be loud at all (an illusion), but rather bigger. More powerful. More insistent. More - just more. Effortless. Arresting.

This amplifier seems to be so fast, so capable that it doesn't even have to try. The Revels appear to match it's abilities foot for foot, and are just as impressive a piece of engineering. I don't doubt which would ultimately win though, this amp being capable of 64A output into DC! However, I would be Deafened long before that. This is a fascinating exercise in building a system around superb engineering, and the music taking care of itself.

Thank you, Colin. 🤗"


Junior Member

ach channel (1 shown) 4 off 47,000uF 2 off 300VA at 15V transformer. 12 output devices, 4 temperature sensors.Ag wire in PTFE for input and output wires. Poly Carbonate input caps. BW 1Hz - 400KHz flat 70W/8R 140W/4R bias from 30W Class A to 5W Class A in A/B mode. SECA driver stage max 140MHz BW to control with ease silly loads. Very expensive to make lots of time and very costly bits.

All working.
75W/8R 140W/4R as it is a pair of Mono Amps
Low A Class setting 5W 8R
High A Class setting 30W/8R
BW 1Hz - 326KHz flat
Balance or Non Balance input 1V full power.
Input RCA 22KR
Input Balance XLR 600R nom (1KR)
Max short term current peak 62 Amps
Damping Factor (silly)

To select amp function there are switches to select Balance and High/Low A Class
THD Low A Class 0.001% into 8R at 20Hz - 50KHz
THD High A Class ( silly) 0.00001% 8R at 10Hz - 100KHz

More tests to be done on sense load input.

I will now convert the Gerber files for the circuit board and put them up.


Junior Member
OK at last got the PCBs and built them up, no smoke and all working.

Info here you can down load. Oops, there was an error! | SECA

BOM for control PCB
Control BOM.jpg
Bom for DC Blocker and SSR

DC blocker and SSR BOM.jpg

BOM for Power Amp ( you will need two set of parts)

Power Amp BOM .jpg

Blank PCBs.jpg
Ctl PCB.jpg

Power Amp PCBs.jpg

Single Powr PCB.jpg


A rough spec.

At last got the new PCB,s and all working lovely.
I have 4 sets left to sell there is 4 PCB,s on a single 2oZ PTH plater.
Two Power Amps
One SSR and DC Blocker with filters
One control pcb, allows you to turn ON/OFF Change bias setting from A to A/B. select Phono or balance inputs.
Chassis are you choice but I will recommend some when I decide I like them.

Max O/P 75W/Ch 8R, 140W/4R, 265W/2R
Max recommend A class setting max of 30W it will get warm so chassis and heatsink important.

BOM being done now. with ref to FEC,RS,Anglia,and CPC sorry no Maplin
Min Transformes 2 off 300VA max transformer 4 at 1KVA ach.
Max current at 20V RMS and no fuses just a bit shy of 98Amps cont( need 4 + 1KVA tranys)

The cost mmm PCB are not cheap still working it out,.
Parts that will be your costing and haggling talents.