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Vintage Preamps

P

PJ03029174

pfm Member
On multiple occasions I've seen people buy vintage power amps with their associated per amp. They are often told to ditch their pre amp for a modern alternative. This seems quite common for Leak, Quad and in my situation a Radford.

I was just wondering why they seemed to nail the power amps but struggle with Preamp design? I've not got a modern per amp to compare it with so am just wondering what I'm missing

Sorry for being vague, in my situation I have a Radford SC3 and a Varislope Leak per amp

Thanks
 
Blimey, how long have we got :)

You can divide The reasons for your observation into two parts.

Firstly we have the issue of compatibility.
Many early pre amps simply have too much gain and/or insuffient overload headroom for modern line level sources. This can result in the input stages being overdriven, plus making it difficult to control volume since everything useable gets condensed into the first fifth or so of the volume control range.
Channel tracking is often poorest at the bottom of the control range, especially with older controlls.

You might also have issues with connectors since many early pre amps used din connectors.

Lastly in this section, you have to consider the ability of an older unit to drive a modern power amp. Tube units in particular might struggle into a modern SS power amp for reasons of insufficient level and generally lower input impedance on power amps these days.

Assuming the above arent issues or can be overcome, we come to the second part of the answer, which is fashion and prevailing opinion.

Certainly in audiophile circles there has been a move away from complexity and the provision of all but the essential facilities - volume, input selection and if you are lucky, balance.
There is also the issue of circuit complexity which in recent decades has been deamed by many audiophiles to be proportional to bad performance - more complex = bad sound.
This is a real shame and completely wrong-headed thinking IME.
What looks complex to the eye is one thing, but all that matters is the impact on the signal and we can analyse that easily enough. Electrons, being rather dim, annoyingly don't follow rules established by human perception.

I never consider circuit or design complexity in connection with audio quality.
The only question should be 'does this work and is it doing what I want?'

So it's partly technical factors of compatibility and partly fashion driven.
 
Thanks for the detailed reply Robert, really appreciate it.
The previous owner of my Radford gear said he'd tried it with a high end modern preamp and preferred the SC3 valve preamp. I wasn't sure and based on Internet research I figured it was a sales pitch but it's been converted to RCA output and Im happy with the gain so I'll quit worrying for the time being and concentrate on other areas

Pete

Thanks

Pete
 
the two brands that I have experience of are quad and naim. The 32.5 44 and 33 are not what I want. They all have too much gain and aren't remote control.

If I use a 32.5 with 140 and reasonably sensitive speakers the hiss is annoying. The same goes for the quad pres. the 33 was unusable at low volumes due to channel differences.

All three are nice preamps, but don't do the job for me.
 
:cool:considering a Radford SC2 as preamp solution for both valves and SS power amps, could you please tell us more about your own experience of the SC3?
 
One further comment to make on Robert's very detailed explanation, and that's the RIAA stage. Vintage pre-amps to match the Quad II and Leak TL10/12 etc have, by today's standards, very noisy phono stages which also have quite high distortion. Many vintage designs used a single EF86 pentode to do the RIAA equalisation, performance that can be very easily bettered today.

S.
 
The nicest vintage valve pre I've used was Lowther's SCU1. But iirc it didn't use EF86s rather double triodes 83's, 82's etc. Quite rare though.
 
Fortunately in America we seem to have come up with reasonable preamps a lot earlier than our British cousins. By 1960 or so we had the Marantz 7, McIntosh C22, and Dynaco PAS-2, among others, stereo tube preamps that are still useable in modern systems with modern sources today.
 
Hi PJ03029174, I am not sure that all my messages are getting to you. There was a typo in my first message. It's the SC22P that is self powered. The SC22 needs HT and LT power from the power amp. Think the SC2 is similar in that respect.

But there is room in an SC22 for a power supply.

I like the SC22, prefer it to my Quad 44 which I bought new when they first came out.
 
Robert has covered the issues very thoroughly - I'd only add one thing - older pre-amps can be a sod to work on or repair. The Quad 22 is a veritable rat's nest. Contrast with the beautifully accessible and soldering-iron friendly insides of a Leak Stereo 20 : nice chunky components all laid out in a row.
 
Agree with most of what has been said above but will add my ha'porth :)

Compatibility with modern amps is not really an issue in most cases as the pre's were only designed to be used with their matching power amp and most often take their power from said amp anyway....

Inputs can easily have attenuators (2 resistors) added to them to keep levels from modern source equipment down to usable proportions.

When rebuilt with modern components the noise level can be significantly lower than it was originally, especially as the ancient components are often starting to "go noisy" anyway.... A component does not have to generate much excess noise when at the first stage of a pre amp for it to be objectionable when amplified by all later stages of both pre and power amps! "All original" old valve pre's will after all these years usually have all sorts of random rustling and crackling noises and sometimes the odd deafening crack/thump!

They are indeed often total sods to work on.... which means that when combined with the fact that they are usually more complicated than the matching power amp, the cost of refurbishment is far more than most people would be willing to pay.... Especially as the matching pre's for such luminaries as the Leak Stereo 20 or Quad II are considered to have a low monetary value whereas the power amps are another matter...

I have totally rebuilt my own Varislope Stereo and have actually been pleasantly surprised by it's performance with the matching Stereo 20 power amp.
 
sergeauckland said:
One further comment to make on Robert's very detailed explanation, and that's the RIAA stage. Vintage pre-amps to match the Quad II and Leak TL10/12 etc have, by today's standards, very noisy phono stages which also have quite high distortion. Many vintage designs used a single EF86 pentode to do the RIAA equalisation, performance that can be very easily bettered today. S.
Click to expand...

It could be bettered then surely, an ECC83 (double) stage gives about the same gain, less noise and more reliability. why was this not the norm back in the fifties / early sixties? Still just the one valve.
 
Barrymagrec said:
It could be bettered then surely, an ECC83 (double) stage gives about the same gain, less noise and more reliability. why was this not the norm back in the fifties / early sixties? Still just the one valve.
Click to expand...

I've asked myself the same question. However, both the Mullard stereo pre-amp and the Leak Point One pre-amp are of this type.

Possibly cost, an EF86 is cheaper than an ECC83? Also, only one cathod decoupling capacitor rather than two, a few fewer resistors. In those days, they seemed to go to extraordinary lengths to avoid using extra components, even at the expense of complicated construction and switching. I've always assumed that assembly labour in those days was cheaper than parts, but really don't know.

S.
 
sergeauckland said:
Possibly cost, an EF86 is cheaper than an ECC83? Also, only one cathod decoupling capacitor rather than two, a few fewer resistors. In those days, they seemed to go to extraordinary lengths to avoid using extra components, even at the expense of complicated construction and switching. I've always assumed that assembly labour in those days was cheaper than parts, but really don't know.

S.
Click to expand...

You are probably right about component count but when Leevers changed their replay amp from an EF86 design to ECC 83 in the early sixties it made a 6dB or so improvement in noise - seems well worth the cost of a few extra bits.
 
The EF86 was popular amongst designers as it was specifically designed for low noise low level input stages. Not for signal noise, but rather filament hum noise. The filament was specially wound in a spiral to minimise hum. If you use any of the popular double triodes, (ECC83 etc.), the hum levels become quite unacceptable, cured in modern times by using DC heaters. Typical American preamps of the time pushed the boat out with DC filament supplies but UK postwar austerity meant the most cost effective solution was required.
 
toprepairman said:
The EF86 was popular amongst designers as it was specifically designed for low noise low level input stages. Not for signal noise, but rather filament hum noise. The filament was specially wound in a spiral to minimise hum. If you use any of the popular double triodes, (ECC83 etc.), the hum levels become quite unacceptable, cured in modern times by using DC heaters. Typical American preamps of the time pushed the boat out with DC filament supplies but UK postwar austerity meant the most cost effective solution was required.
Click to expand...

Thank you for that. The last valve amplifier I designed back in the '80s had ECC double triodes and I didn't have any hum problems, but indeed, did use DC heaters, didn't try it with AC heaters. I wasn't looking especially for low noise, just thought DC heaters to be good engineering practice.

S.
 
sergeauckland said:
I've asked myself the same question. However, both the Mullard stereo pre-amp and the Leak Point One pre-amp are of this type.

Possibly cost, an EF86 is cheaper than an ECC83? Also, only one cathod decoupling capacitor rather than two, a few fewer resistors. In those days, they seemed to go to extraordinary lengths to avoid using extra components, even at the expense of complicated construction and switching. I've always assumed that assembly labour in those days was cheaper than parts, but really don't know.

S.
Click to expand...

In this assumption you are quite correct - at least in respect of one manufacturer.

My old friend Andre Dahmer admitted that it was cheaper to employ his "girls with soldering irons" than to use a more electronically elegant approach which might require additional componentry. This was in the depths of wildest Essex in the later 'fifties when he was producing the Avantic. The larger model (DLS37) had more knobs than any other pre-amp I can remember.

Regardless, the Avantic was a quality piece of kit.

Richard.

PS Just remembered the HMV 555/6 which had more controls at the front end than the Avantic, umpteen independent compensation circuits on two channels and a magic eye. Simple it wasn't but noise levels were commendably low. Often, spurious noise is a function of construction, layout and quality of assembly rather than a consequence of circuit design.
 
Another thing with the noise issue of the EF86.
Pentodes tend to be rather noisy (white noise hiss) compared to triodes, due partly to secondary emission fron the screen grid, so the grids are very carefully aligned to minimise this.
 
toprepairman said:
Another thing with the noise issue of the EF86.
Pentodes tend to be rather noisy (white noise hiss) compared to triodes, due partly to secondary emission fron the screen grid, so the grids are very carefully aligned to minimise this.
Click to expand...

Still a lot noisier than a triode though! ;)
 
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