Good SS amp for a Croft preamp: suggestions?

Hi mates,

I'd like trying my Croft Micro Series 3 preamp with a solid state amp. I had it hooked to a lovely Croft Series 5, a great classic and a long-time loaner, but it had to come back to its owner, as his own Leak Stereo 20 has gone pop.

I'm told that Croft's preams are rather peculiar regarding input sensitivity and other issues. Any experienced users out there or suggestions?

Thanks in advance!

Regards,

Vincula

 

Hi Vincula,

The issues are high output impedance on the pre, which IIRC is around 3K Ohms.

Applying the usual rule of thumb that the load impedance should be a minimum of 10X the source, that gives a 30k minimum.

You also want to use short, low capacitance interconnects.

Lots of power amps load the pre at between 10-20k which is too low for the Croft.

I'll have a think for some possible candidates later.

 

Thank you, Rob . I knew there was something. I like playing, but better with a chance to get it right from the beginning, especially regarding technical issues. I await your suggestions then.

Please guys do feel free to chim in!

Regards,

Vincula

 

Obvious but:

have you looked at the Croft series 7?

Very good SS amp (apart from the one valve that is)

 

Thanks, Coda II. I had already considered that one. Just wanted to open up the eventual choice of amps a bit...

Regards,

Vincula

 

I owned a Croft Series 7 power and a Croft Micro 25 preamp a couple of years ago and the build quality was awful. The on/off power switch on the power amp fell to pieces and had to be replaced within one year of ownership. Not what I would call quality when you consider what it all costs.

 

I've already changed two switches on my Micro Series 3. Very Morris-like charming retro-chic, but true, not very reliable. Sounds great though.

Regards,

Vincula

 

They do sound good.
I remember the old original Micro looking like school lab equipment

 

Any ideas as to what SS-amp(s) would be a good match, Rob, apart from Croft's own creations? I've been surfin', but I only seem to find valve amps with 'em, like Leaks and the like...


Regards,

Vincula

 

Another couple of options then.

You can often set the input impedance of amps by adjusting a resistor on the input section. You might also want to change a cap there so the filter that removes ultra-sonic crap is not too low.

The second less DIY option is to use a buffer in line with any amp you like. I know there are some that come as a full ready made solution but I can't think of the names. Some other things like this can be had though, not that I'm actually sure what the input impedance of wither of these is but I guess they can make them as you want:

http://www.6moons.com/audioreviews/burson/buffer.html
http://www.ska-audio.com/diy/VBuffer.html

 

I used a croft vitale with an exposure 18 super some years ago. Apart from a bit to much gain it was a great combo.
Croft together with exposure has been a popular combo in Copenhagen.

best, Lars

 

Now come on, with the greatest of respect I think you're exaggerating there. The switch is a standard part, and it's VERY rare for it to fail. The one in my preamp is twenty years old and fine... How is the build awful? No circuit boards so everything is hard wired and not laid out on neat rows? At the time, you said you were happy with the service you received... Fancy casework costs a fortune in the UK and the plain black oblong box with recessed mounting panel does look simple and elegant. It's not made for peanuts in China you know

Apologies folks, but credit where it's due. perhaps you should look inside most gear made before circuit boards came into use. I think Glenn's build is just fine and usually utterly reliable and easy to fix or update as necessary.. At least he gets his capacitors round the right way and specifies them to last for decades, rather than running them flat out so they die after ten years

Now, regarding the output impedance issue. I'd suggest an email to Glenn, as there's a few things he can do to his old products and re-working the line stage to reduce the output impedance may be one of them.

Apologies again, I don't wish to rock the boat, but I vivdly remember the horror when this faulty switch was mentioned and I do believe as much as possible was done to resolve the issue quickly.

 

Must admit I'm not generally a fan of valve amps but of those I do like, Croft sit right at the top of the list.

I loved my little Series V which gave a good 25wpc from eight EL84s on a valve rectified PSU. Barely larger than a single Quad II.

It was the amplifier that shattered my view that all valve amps sounded poor. Lovely into Impulse H2s at the time.

While the build looked very 'garden shed' it was well made and used good parts. Ditto the SMA valve pre amp.

 

I apologise for being a bit harsh about the power switch above, but even the over-hyped but gorgeous looking Audio Research had failures on their posh looking flick-switches back in the day.

I have to say that I don't hugely like the little RS switch Glenn uses, but since my preamp has six of the blessed things in one form or another


P.S. The good thing about the "garden shed" point-to-point wiring is that mods are easy to carry out. Glenn has taken the original "RS cased" Micro and breathed new fresh life into the power supplies and circuit and to very good effect as well. He can even race-tune the current models too - power supplies mostly, confusion only preventing him from bringing out more "official" versions in his range. It's this and Glenn's love of what he's doing that makes me such a staunch defender of his products, each one having something of "the man" in them.

 

If it makes things any better, the power amp under discussion found a very a happy home down here in Devon.

The power switch does still work itself loose and I've never quite worked out how to get it properly tight. A start would be a very thin spanner I guess - is there a particular name for them?
Improvising with a screw driver is almost good enough but it's also one of those areas where I can't quite see what is tightening against what.

 

The identical? switches on my Series 4PP preamp have never worked loose, but again, an email to Glenn would be most fruitful for a solution. he doesn't bite - honest

If the series 3 preamp has it's output impedance down to a very few hundred Ohns as mine is, then any reasonable power amp should be fine - just keep the interconnects around a metre and low in capacitance I think. My Crown D-60's are 25K, give or take and with 1m Van Damme mic cables as interconnects (screen/drain connected at the preamp end only), the soundfield is wonderful and 3-D in a way I never thought these power amps could give in a million years..

 

I've used my Micro II pre into a Mark Levinson No. 29 and it sounded good, just not as good as into my DIY valve hybrid mono-blocks (nor does any pre I have tried, valve or SS).

However, I did get the output stage updated to latest spec by Glenn when I bought it. He is an absolute gent to deal with - very up front, and very good value!

Richard

 

Both of the croft pre amps I have owned have been very happy to drive any and all solid state power amps to very high levels
I recognise the truth of the impedance issue but honestly I dont think you'll struggle much and the combination of simple, clear, sweet valve pre amp and muscular solid state power amp can be a very persuasive one. Such combinations have been a feature of the American high end scene for 30 years and more (ask DJSR)