Cool Old Kit You Never Heard Of

[Barry]

I think the inputs and outputs were XLR. I also think it was all valve, which appeals to me, and it's reputedly good sounding.

Marco.

Sadly not, the SP-11 used RCA connectors.

They were hybrid amplifiers, using a mixture of valve and solid state electronics, but were by all accounts good sounding.

[Marco]

Re the Thöress preamp:

All Thöress audio products are made in Germany, and all use valve technology and 'point to point' circuitry (that is no PCBs). To quote from the manufacturer:

Hand made in limited quantity by Reinhard Thöress in Germany. All NOS tube: Preamplifier and Phono amplifier, hard-wired triode amps with hand-wound transformers.


The construction looks impeccable, as can be seen from the following photos:





And they get a good review from TNT Audio: https://r.search.yahoo.com/_ylt=A2RS...bSTjpMkGy_lHI-

Although I like the look of the style of the rotary controls, they do look cheap, and certainly out of place on a piece of kit costing €8,200.

Could be very different 'in the flesh', certainly in terms of how they operate and are constructed.

An option then should I ever sell the Croft, as It's built on similar principles.

Marco.

[Marco]

Sadly not, the SP-11 used RCA connectors.

Noted... I don't need XLRs anyway.

Marco.

[Firebottle]

Re the Thöress preamp:

All Thöress audio products are made in Germany, and all use valve technology and 'point to point' circuitry (that is no PCBs). To quote from the manufacturer:

Hand made in limited quantity by Reinhard Thöress in Germany. All NOS tube: Preamplifier and Phono amplifier, hard-wired triode amps with hand-wound transformers.


The construction looks impeccable, as can be seen from the following photos:





And they get a good review from TNT Audio: https://r.search.yahoo.com/_ylt=A2RS...bSTjpMkGy_lHI-

Although I like the look of the style of the rotary controls, they do look cheap, and certainly out of place on a piece of kit costing €8,200.

I have repaired one of those, very nice to work on.

[Marco]

My only criticism is that, for the price, I'd have liked to have seen an external PSU with bigger transformers (as per my Croft), but with hand-wound transformers being used goodness knows what that would add to the price!

Marco.

[Beobloke]

Not old, and I have heard of it, my ultimate 'science lab' amp:



Marco.

It's always fun to play with a Rechter Kanal...

[Marco]

Marco.

[Barry]

My only criticism is that, for the price, I'd have liked to have seen an external PSU with bigger transformers (as per my Croft), but with hand-wound transformers being used goodness knows what that would add to the price!

Marco.

Bigger is not necessarily better, when it comes to power transformers. Being hand-wound, there are many aspects of the design that have to be considered: bi-limboid or superimposed windings?; E-I interleaved laminations, or two sets of E-shaped cores, butted together? etc. Then there is the consideration of the windings: are both the primary and secondary windings wound together at the same time or sequentially?

Transformers are most efficient when the core flux is close to saturation, but if the core does saturate say with a current surge, the transformer ceases to create current in the secondary winding. Thus the overall size of the transformer is important.

So you cannot just buy and use any old transformer.

[Marco]

For sure, but for the price asked, the designer could've fitted larger transformers of the right type [experience tells me that over-speccing things usually brings an audible improvement), and externalised them in a separate box, thus removing a magnetic field away from 'delicate' components, both of which I've done with my Croft with considerable success

Marco.

[Barry]

The mains transformer does not appear to be shielded or shrouded with a mu-metal shield, so depends on the transformer core laminations not having any flux leakage. The transformer is however located distant from the electronics, so the effect of any flux leakage is minimised; although an additional magnetic shield between the transformer and the nearby valves wouldn't do any harm.

Rectification is provided by a pair of solid state diodes, rather than a double-diode valve, so putting the power supply in a separate enclosure would not offer any real benefit; it would just cost more.