For further amplification: preamp advice and moving along from Croft

[camtwister]

I am very familiar with both a Croft Micro 25 and the 25R in my system.
I'm rather emotionally attached to these unassuming boxes and intend to keep them safe and sheltered.
At the same time, I have funds of £750 to spend on the used market for a preamp.
Who has upgraded from a Micro 25 and to what?

Is it feasible for me to upgrade on this budget in the second-hand market?

I welcome the opinion of those that have upgraded from the Micro 25 and would like to know:
- what appreciable sonic improvements have you gained?
- what have you lost?

Please would only those that have direct experience comment. Thank you.

Solid state or valve allowed but no passives. Ta.
Phono stage is a bonus but not essential because I have a CJ EV-1.
I'll be using a 200W power amp with an input sensitivity of 1.46V and an input impedance of 20k ohms.
Speakers are Colin Topp's Edingdales.
Music of all spectrums; weight, bass extension, grip and slam a priority but not at the exclusion of air, detail and beguiling timbre.

I'll put the kettle on.

[camtwister]

I'd like to listen to Tron and SJS but I'm aware that my budget is insufficient.

[hifinutt]

did you see the lovely tron seven pre at 1200 quid? its a bargain , real pain its above your 750 budget !!

[camtwister]

Yes, I did, thanks Phil.
I can't stretch that far.

[Opti-cal]

Had a Croft 25 for a while, then an older Micro. Nothing wrong with either but I always wanted 'more'. Texture I guess, in a word.

I've got the MK1 version of this (highly modified though).

https://www.musicalparadise.ca/store...product_id=103

This one is supposed to be better, I'd spec the Mundorf caps and upgrade the tubes myself. RCA/Sylvania work very well in mine. I use mine with a 200w Class D power amp but its happy driving anything really.

In my system its streets ahead of anything and has very flexible input/outputs and a remote as a bonus. Admittedly unlikely to best a Tron/Tektron/SJS (although it wouldn't surprise me if it did). But its a lot cheaper so represents exceptional bang for buck in my opinion.

I love Musical Paradise products, the designer knows what he is doing and builds quality examples. I've modded a couple of his DAC's too which will compete with most. If the mods were incorporated into his products initially they would cost considerably more so they make superb 'bases' for builds or taking things to another level. However their performance in standard form is already more than respectable.

He is also happy to answer questions via email should you have any.

Cheers

[camtwister]

This is very interesting. Thank you Chris.
For confirmation, the amp comes fully built?

I note that there are two options for rectifier filament voltage and two for the signal tubes.
Can you use any perm and comb of these?
I understand that the selection will determine gain, and voltage drop across the circuit - and so determine tonal qualities and dynamics.
How do you make that choice?

[Opti-cal]

This is very interesting. Thank you Chris.
For confirmation, the amp comes fully built?

I note that there are two options for rectifier filament voltage and two for the signal tubes.
Can you use any perm and comb of these?
I understand that the selection will determine gain, and voltage drop across the circuit - and so determine tonal qualities and dynamics.
How do you make that choice?

Indeed it can use different tubes and rectifiers :

'support both 6.3V and 5V rectifier, 6.3V and 12.6V signal tubes'

so:

'1. 6.3V filament rectifier tubes: 6Z5P, 6X5.

2. 5V filament rectifier tubes: 5R4, 5U4G, 5AR4, GZ33, GZ34, 274B, 5Y3, 5Z3P.

3. 6.3V signal tubes: 6N11, 6N1P, E88CC, E188CC, CCA, 6922, 6H23, 6H6, 6H30, (6SN7 with 6SN7 to 6922 adapter).

4. 12.6V signal tubes: 12AU7, 12BH7, E80CC, (12SN7 with 6SN7 to 6922 adapter).'


I run mine with a GZ34 rectifier (mullard) and 6SN7 tubes (with the adapters which you can get from tube stores in the USA, mine took a week to come).

Having said that I've had satisfactory results with many from the 12*** family of tubes also.

In mine you can mix and match tube types (as long as they operate on the same voltage 6.3 or 12). So in mine you can run 12au7 with 12bh7 but not with 6sn7 if that makes sense.

My MK1 version requires 4 pre-tubes this one uses 3 (so one less tube to buy) but it looks like it retains the 'dip switches' on the circuit board which (on mine) can be used to raise or lower the output gain as well as having adjustable feedback option. Hence a very flexible package.

Pre-amp comes fully built, I think a lot of people might be put off by the PCB's and less than dazzling appearance, but the sound is what matters and that is guaranteed.

I'll have a read through of the manual myself actually but I'm fairly sure I can confirm all of the above.

It took a lot of experimenting to find the 'sweet spot', as with all these things its totally system/speaker/room dependent, so I would advise doing the same. However if you don't have the time or energy for this (understandable!), it doesn't take long to get 90% of the way there with some trusted combinations. I'd go a Mullard rectifier (everytime) and NOS RCA 12bh7's in the pre section. Always sounds excellent to me.

Having said that people seem to think the stock tubes are fairly decent, again might be just a case of listening for yourself but I'd always be wondering 'can it be better?' . . . but thats me.

You would need adapters if you want to get into the 6SN7's but again the jump in performance is only slight (but its there).

Hope this helps,

Cheers.

[camtwister]

Fantastico Chris! Thank you.

I understand now that gain is adjustable via another set of dips regardless of valve choice.

I have several types of the 5V rectifiers in my collection.
Have you compared Brimar 12bh7 (50s vintage pre Thorn) to RCA?

How do you change caps without soldering?

[Opti-cal]

Fantastico Chris! Thank you.

I understand now that gain is adjustable via another set of dips regardless of valve choice.

I have several types of the 5V rectifiers in my collection.
Have you compared Brimar 12bh7 (50s vintage pre Thorn) to RCA?

How do you change caps without soldering?

Yes I really like the Brimar 12bh7 (although no experience with that model specifically, I think 'AnthonyTD', among others, of this forum, has a wealth of knowledge on them) they would be an excellent choice. Not particularly cheap these days though! But get some nice black plates and you'll be away . . . .

The caps have terminals with screw down tops to grip the wires from the caps, a bit like a speaker binding post. A really nice little design there.
If you do go ahead I'd be very interested in your findings as I've had my eye on one but couldn't really justify it over my little collection of pre's. You have some nice kit there and although this would sit low in the budget stakes in comparison, I'd propose it wouldn't be out of place sonic-wise, at all.

With mine the volume pot was upgraded to a ladder type fairly quickly which brought the performance up a notch or so, but it still sounded wonderful out the box. I only mention this as I see you have other 'modded' equipment and perhaps like me, you like to find out just how much can be squeezed out of (occasionally modest) equipment.

Cheers

[camtwister]

Your input is much appreciated Chris.
Pending comments from others and further research, the MP-701 is most certainly on the list at the moment.