diytube.com

Some pictures

PCB and OPT in size

OPT clone of A470


Schematic ST70 mkII

Nice styling - the white and the black. That output transformer is the most unique design for an st-70 I have seen.

Impressive work. Did you wind the transformers yourself?

No tube rectifier? Not fair!

Looks like an add

battradio wrote:Looks like an add

Looking at his other thread, I think so:
http://www.diytube.com/phpBB2/viewtopic.php?p=30985

By the way, Ultraline, that A470 wind-up chart was from me. If you use the image for commercial purposes, you **must** credit Classic Valve Design, or remove it from all your servers promptly.

Cheers!

dcriner wrote:No tube rectifier? Not fair!

PCB can use KT88, 6550, KT90, ... so I do not use the tube rectifier.
Tube rectifier only provides 250mA max for all-not enough

Geek wrote:By the way, Ultraline, that A470 wind-up chart was from me. If you use the image for commercial purposes, you **must** credit Classic Valve Design, or remove it from all your servers promptly.

Cheers!

I am Diyer.
I am not advertise and business this product on the forum public.
My idea is design modern alternative the classic design for tube.

Ultraline wrote:I am Diyer.
I am not advertise and business this product on the forum public.
My idea is design modern alternative the classic design for tube.

Thank you for the confirmation.

We are somewhat protective of our little "DIY cubbyhole" of the net

Cheers!

Geek wrote:By the way, Ultraline, that A470 wind-up chart was from me.

Cheers!

What brand/model transformer is that output, anyway?

It was a Dynaco.

BUT.... there were several manufacturers of Dynaco OPT's over their run and their specs differ (DCR and inductance). I only parted a couple (one cloth leaded, the other vinyl leaded) and averaged the winding turns.

IMO, if you get a stock Dynaco OPT, go for the cloth leaded ones - helluvalot better made.

Cheers!

dcriner wrote:No tube rectifier? Not fair!

ST70 use tube rectifier GZ34
ST70 MKII(same my clone) use diode rectifier

ST70 vs ST70 MKII

Code: Select all

I compared the sonic characteristics of the two amps on my stereo system. The preamp was a Dynaco PAS3 (using Telefunken 12AX7 tubes). Source material was played on a Dual Dual CS 505-3 turntable (belt driven with an Ortofon OMB 20 cartridge and needle), and a Parasound C/DX - 88 CD player. Speakers were a pair of Paradigm 11se Mark II.

For source material I played vinyl records and compact discs (classical and rock'n roll). I tried to listen at the same volume level when comparing the two amps. I left the preamp bass and treble controls in their flat (neutral) positions.

I found the original ST-70 to be mellow, smooth, and very laid back in sound. The bass was not very strong. To get good bass, one had to adjust the bass control on the preamp. The ST-70 was especially good for classical music.
This amp uses vacuum tube rectification, so as to be expected, it developed sag (a volume drop due to rectifier voltage drop at high current demands) at loud and bass-like musical passages. This amp was very tube-like in sound, and it could be listened to for hours without any fatigue at any volume level!

I was very surprised and impressed with the sound of the Series II amp. It was dramatic and dynamic (the opposite of laid back). Bass was very strong. You could feel the bass! This was no doubt due to the increased capacitance of the power supply, the increased size of the power transformer, and the solid state rectification.
The sound was wonderful and addictive - one could listen for days! The amp sounded fast and responded quickly to musical passages (due to the diode rectification). The Series II had the characteristics of a tube amp, but at the same time had some characteristics of a solid state amp. I found this amp to be best for rock'n roll.
At higher volume levels my house really rocked! It is amazing that the living room bay window did not break. Who knows what the neighbors thought!

So, which amp do I like better? I have to admit that I like both, and use both alternately. It all depends on the type of music you play. Both are really great amplifiers - a treat for the ears!

source:

http://www.tnt-audio.com/ampli/dynaco2e.html

quote:


I am Diyer.
I am not advertise and business this product on the forum public.
My idea is design modern alternative the classic design for tube.

I think you are more than a diyer. This is a ad if I've ever seen one.