Amp/Preamp Asylum: REVIEW: Leak St20 Amplifier (Tube) by huubdas

Model:	St20
Category:	Amplifier (Tube)
Suggested Retail Price:	whatever you can agree to
Description:	small pp EL84 stereo 'power' amplifier ideal restoration /tweak target
Manufacturer URL:	Not Available

Review by huubdas on September 07, 2009 at 16:26:49
IP Address: 87.210.32.152 Add Your Review
for the St20

Leak stereo 20: replace all couple-caps with MKT or MKP. Check PSU electrolytics. Replace GZ34 with 2 1N4007 plus 100 Ohm in series to the first electrolytic condensor. Check all resistors, many will not have the spec values. Now it is a really high end amp.
With good loudspeakers, even Magnepan MG IC, no feedback is the best sounding. Just remove V-1, disconnect it-s anode resistors and then connect the input to the entrance condensor of the Schmitt phase splitter.
Sensitivity is the same as with feedback. This procedure is easy reversible if your loudspeakers are underdamped by bad design, Magnepans (IC) are 5 Ohm at all frequencies, so these have no problems at all.

The Varislope is bad, replace anode/screen/cathode resistors by standard 100 Kiloohm/390 Kiloohm/ 1 Kiloohm and give them 250 volt by a separate power unit. ( the outlet on the Leak stereo 20 will drop too much because the EF86 will draw 2mA now.

Product Weakness:	After 5 years all kinds of problems, hum, hot transformers because of leaking capacitors, bad minimal PSU capacitors and bad resistors, many loose their values especially in the phasesplitter, the EL84 cathoderesistors. Renewal makes it a completely new amp, because the transformers are good and the circuit also.
Product Strengths:	Very good new in 1967.<br>

Associated Equipment for this Review:

Amplifier: leak stereo20
Preamplifier (or None if Integrated): modded varislope pre
Sources (CDP/Turntable): cd phono
Speakers: Dali 606 Magnepan IC
Cables/Interconnects: 4 mm
Music Used (Genre/Selections): everything that swings
Room Comments/Treatments: rugs, curtains
Time Period/Length of Audition: 1967 -2009
Type of Audition/Review: Product Owner

Amplifier:	leak stereo20
Preamplifier (or None if Integrated):	modded varislope pre
Sources (CDP/Turntable):	cd phono
Speakers:	Dali 606 Magnepan IC
Cables/Interconnects:	4 mm
Music Used (Genre/Selections):	everything that swings
Room Comments/Treatments:	rugs, curtains
Time Period/Length of Audition:	1967 -2009
Type of Audition/Review:	Product Owner