The Croft Epoch - A Tale of developing a MoFo of a pre amp..........

[Wakefield Turntables]

So why the Croft preamp? Well I've lusted after one for some time after sampling the delights of the micro basic which to my ears easily ousted my old Radford preamp. The Croft mated extremely well with my Radford power amp and I now listen most nights to old jazz records, relaxing and passing the night away. The MM stage is probably one of the best I've heard, I would say that it easily beats the £600+ optional extra MM stage on my ATC SCA2 preamp. Your actually getting a bloody good MM PHONOSTAGE and a free preamp when you buy the micro basic! I did consider the £4k Cary 2 box preamp that came onto the market on this forum. I considered the new Radford preamp, I also considered one of Audio Research reference preamps, I decided against icon audio and couldn't be bothered with some of the older preamps available from Quad, Leak, Armstrong etc mainly because everyone is a GURU and has an individual idea on how these classics should be modified. I like the idea of croft because the designer is still alive and well and very open to modifying his designs, additionally he knows how to get the begs out of the amp. I look forward to going on a modification journey with this pre-amp. Initially it will sit in the system for me to assess the "sound" of the Croft and then modifications will start probably after new year.

[Wakefield Turntables]

Not to let the grass grow under my feet I've just got into contact with Glenn with regards getting some serious mods done to the Epoch, mainly

1. Upgraded PSU & Coupling caps.
2. Maybe dual PSU's like Joe's
3. New pots + relevant nice resistors (Charcroft maybe)
4. Valve to Mosfet regulation.

Looks like I might need a new set of KT77's/EL34's for this amp as one of the valves seems a little dodgy given intermittent left channel drop out :steam:. Why didn't the shit on eBay inform me of this. Anyway a good chance to do a little tube rolling. So, looks like I might be putting in an order with Watford valves for some cheapo EL34's to put me on. The MicroBasic is sitting in the system for the time being. I like what I'm hearing from the stock Epoch, but I got the upgrade itch!

[Andrei]

Scratch it Andy, scratch it!

[Marco]

Nice one, Andy... EL34s though, where are they (or it) - in the PSU section or used as a rectifier? Because the output valves should be 6SL7s.

Marco.

[Wakefield Turntables]

Nice one, Andy... EL34s though, where are they (or it) - in the PSU section or used as a rectifier? Because the output valves should be 6SL7s.

Marco.

I will explore I have some pics of the innards I took last night, I'll post them up later. Can you tell me the proper valve complement for the amp?

Thanks

[Tweedle-Dee]

I have an Epoch V line level that started off with a similar configuration to the one you have bought (minus the phono stage) before Glenn breathed on it for me (a significant upgrade). My understanding is that two of the 6SL7s are for the line level outputs and three are for the phono stage. Could you change the tubes around in your new Epoch?

[Wakefield Turntables]

Well this is frustrating I emailed Glenn Croft over a week ago and still no reply! Whilst I await the great mans response I can start to plan what to do next with the amp. I've spent a couple of days listening two its sonic signature and have come to the conclusion that Mosfet regulation is the way ahead. I've been researching valves and this remains an ongoing area of amusement. I have a Brimar and Mullard ECC83, the 6SL7's is still a matter of debate and I think I'm plumping for the Tesla 85A2 which has to be better than the sorry looking thing thats sitting in their at the moment! Ive decided to have the whole thing rewired with silver and the female RCA's sockets are another area of research. I quite like the looks of these http://www.hificollective.co.uk/phono_sockets/wbt-0210ag-topline-nextgen.html, these will probably be installed into the line 1, phono and line input sockets. I also think one of the IeGo pure silver IEC inlets could be of benefit. I'm doing a little tube rolling with my MicroBasic in that I've just plonked a couple of Mullard Ecc83 in and they sound bloody brilliant! Mmmmmmmm could mullard valves end up in my Epoch, only time will tell.

[Wakefield Turntables]

The great man has been in contact. Looks like the Epoch is getting booked in for what he calls the "full monty", :eek:. I have no idea what's involved but it looks like it will take several weeks. Glenn should be getting back to me with a list of mods, keep tuned.

[Jimbo]

Nice one Andrew. I think your going to end up with a fantastic preamp once Glenn has fettled it!

[The Black Adder]

There is simply no doubt :)

[Wakefield Turntables]

Well I'm enjoying this exercise more and more as I'm slowly learning How the amp works. I'm sure Glenn has some fantastic ideas as to how the amp could be improved and that's what I like. I love the idea that I can talk and discuss the mods and see how they work. Part of the whole hifi experience is knowing that I tailored my equipment to my needs it's very satisfying seeing how your ideas turn out especially at the end of a long winters night when your completely chilled out listening to your favourite tunes.:D

[brian2957]

Well I'm enjoying this exercise more and more as I'm slowly learning How the amp works. I'm sure Glenn has some fantastic ideas as to how the amp could be improved and that's what I like. I love the idea that I can talk and discuss the mods and see how they work. Part of the whole hifi experience is knowing that I tailored my equipment to my needs it's very satisfying seeing how your ideas turn out especially at the end of a long winters night when your completely chilled out listening to your favourite tunes.:D

With a favourite tipple of course Andrew :D I like this type of thread since it points the way to people who buy 2nd hand gear ( in this case Croft ) and want to upgrade it .

[Wakefield Turntables]

With a favourite tipple of course Andrew :D I like this type of thread since it points the way to people who buy 2nd hand gear ( in this case Croft ) and want to upgrade it .

Usually a big glug of single malt Brian! I hope you enjoy the thread and I'll be posting some pictures later.


The part in bold is it... couldn't agree more.

Thanks!

Well I got another email and the fully monty includes :-

Seiden selector switch.
Eichmann phono sockets.
Khozmo attenuator.
SCR Teflon output caps.
Rike PIO coupling caps.
Clarity Cap TC4 power supply caps.
Separate transformer box with separate 500VA transformers for each channel.
Separate hybrid ht supplies for each channel.

Precision wirewound resistors.

Individual heater regulators for each valve.


I'm not sure if Glenn can push things further but sounds pretty exhaustive. I still don't know how he's going to populate the Khozmo attenuator, I'd like to know his resistor selection. Additionally I have no idea what " Individual heater regulators for each valve" are and God only know's what "Separate hybrid ht supplies for each channel." can be :scratch:. I presume that they must have something to do with the SS regulation that some of these high end Crofts seem to have around here :lol:. I have some pictures for later so I'm off for an hour to get some work done.

[Jimbo]

Usually a big glug of single malt Brian! I hope you enjoy the thread and I'll be posting some pictures later.



Thanks!

Well I got another email and the fully monty includes :-

Seiden selector switch.
Eichmann phono sockets.
Khozmo attenuator.
SCR Teflon output caps.
Rike PIO coupling caps.
Clarity Cap TC4 power supply caps.
Separate transformer box with separate 500VA transformers for each channel.
Separate hybrid ht supplies for each channel.

Precision wirewound resistors.

Individual heater regulators for each valve.


I'm not sure if Glenn can push things further but sounds pretty exhaustive. I still don't know how he's going to populate the Khozmo attenuator, I'd like to know his resistor selection. Additionally I have no idea what " Individual heater regulators for each valve" are and God only know's what "Separate hybrid ht supplies for each channel." can be :scratch:. I presume that they must have something to do with the SS regulation that some of these high end Crofts seem to have around here :lol:. I have some pictures for later so I'm off for an hour to get some work done.

Err that sounds pretty comprehensive to me.

Might be up there with your spec Jo:)

[Wakefield Turntables]

Hmmmmm...... quite disappointing but also reassuring. I hope this is as far as Glenn can push things (the reassuring bit), but I hope Glenn's just not copying your amp - the disappointing bit. It would be interesting to see if Glenn's making any compromises with these parts or if's he's selected these with the knowledge that they are definitely the best bits for the job.

[Jimbo]

Hmmmmm...... quite disappointing but also reassuring. I hope this is as far as Glenn can push things (the reassuring bit), but I hope Glenn's just not copying your amp - the disappointing bit. It would be interesting to see if Glenn's making any compromises with these parts or if's he's selected these with the knowledge that they are definitely the best bits for the job.

I can tell you Andrew I have known many of the amplifiers Glenn has built over the years having had his original micro nearly 30 years ago and I have heard many of his pre and power amps although not all his specials.

If you really want to know how far he can go with your pre speak to Adrian Parsons at Audioflair and i can tell you some of the components can be eye watering in price and his amps can be mind boggling in complexity - take a look at his Absolute 1 pre amp with 8 transformers and an unbelievably complex circuit. It all depends how far you really want to go and how deep your pockets are. Some of the caps are £1000 a pop!

Ultimately however its all about how the amp performs and sounds and this is where fine tuning may come into play especially with its interaction with the rest of your system.

[Jimbo]

The Croft Absolut 1

http://www.6moons.com/audioreviews/croft/croft.html

Not sure if he would build one of these again! :)

[Marco]

I could say a few things about that, and about the 'Amar era', in general... :doh: :rolleyes:

Let's just say that Glenn's head was not in a very good place then (and for valid reasons)!

Marco.

[Jimbo]

I could say a few things about that, and about the 'Amar era', in general... :doh: :rolleyes:

Let's just say that Glenn's head was not in a very good place then (and for valid reasons)!

Marco.

Your right Marco - the past is probably best left alone but some of Glenns creations were absolutely amazing and shows what a genius he really is with valve amps. Don,t forget your amp and Jo,s in their orginal concept were created in that past.

[Wakefield Turntables]

I can tell you Andrew I have known many of the amplifiers Glenn has built over the years having had his original micro nearly 30 years ago and I have heard many of his pre and power amps although not all his specials.

If you really want to know how far he can go with your pre speak to Adrian Parsons at Audioflair and i can tell you some of the components can be eye watering in price and his amps can be mind boggling in complexity - take a look at his Absolute 1 pre amp with 8 transformers and an unbelievably complex circuit. It all depends how far you really want to go and how deep your pockets are. Some of the caps are £1000 a pop!

Ultimately however its all about how the amp performs and sounds and this is where fine tuning may come into play especially with its interaction with the rest of your system.

I have to be sensible and am I really going to see a massive difference if I plonk in a £1K cap when a £20 cap will do just the same job? I'll have a look at the Audioflair website.




The Croft Absolut 1

http://www.6moons.com/audioreviews/croft/croft.html

Not sure if he would build one of these again! :)

I've seen this page before but completely forgot about it. That is one series pre-amp, I dont think my pockets are that DEEP! ;)

[Wakefield Turntables]

15736157371573815739

Some pics of the innards of the Epoch. Pretty standard stuff. This example has x5 6H9C instead of x5 6SL7, x1 6GV8 instead of a ECC83 and x1 85A2. I'd be interested in finding out why I have the 6Gv8 instead of the ECC83 :scratch:

[Firebottle]

Usually a big glug of single malt Brian! I hope you enjoy the thread and I'll be posting some pictures later.



Thanks!

Well I got another email and the fully monty includes :-

Seiden selector switch.____________\
Eichmann phono sockets.__________\
Khozmo attenuator._______________\ All good quality stuff Andrew
SCR Teflon output caps.___________/
Rike PIO coupling caps.___________/
Clarity Cap TC4 power supply caps. /
Separate transformer box with separate 500VA transformers for each channel.
Separate hybrid ht supplies for each channel.

Individual heater regulators for each valve.

Additionally I have no idea what " Individual heater regulators for each valve" are and God only know's what "Separate hybrid ht supplies for each channel." can be :scratch:.

The separate transformers feeding separate ht supplies is the best approach for minimum crosstalk between channels. The 'Separate hybrid ht supplies' just means that valves and FETs are being used in the power supplies to give maximum performance.

Individual heater regulators are very easy to implement, just a 3 terminal regulator chip, also I imaging to ensure no crosstalk between different stages.

Very similar approaches that I incorporate in my designs. :)

[Wakefield Turntables]

The separate transformers feeding separate ht supplies is the best approach for minimum crosstalk between channels. The 'Separate hybrid ht supplies' just means that valves and FETs are being used in the power supplies to give maximum performance.

Individual heater regulators are very easy to implement, just a 3 terminal regulator chip, also I imaging to ensure no crosstalk between different stages.

Very similar approaches that I incorporate in my designs. :)

Alan, many thanks for the reply. I've bought a couple of simple electronics books so that I have some grasp of what I'm talking about. I need to re-read the passive amp thread of Marcos with regarded attenuators but I think the basic principles of these are quite simple to understand. I just need to get my head around FETs and how they work with a valve to regulate the power. I understand what "cross talk" so I can see why some of the components are being used. Looks like I need to do some reading around heater regulators, maybe tonight's homework?!

[YNWaN]

Now this is a lot of Croft pre-amp:

http://www.6moons.com/audioreviews/croft/hero2.jpg

[Firebottle]

Going the hybrid route and using FETs, particularly in the power supply circuitry, is a designers wet dream.

Put simply the characteristics of power FETs is like a valve on steroids, so you get whatever benefits accrue from using valves but with much better performance, there is also the simplification of no heater required.

The individual heater regulators are a bit OTT possibly, as I wouldn't expect any crosstalk between stages via the individual heaters. However it does make any fault protection or fault finding that much easier.

:)

[Wakefield Turntables]

Now this is a lot of Croft pre-amp:

http://www.6moons.com/audioreviews/croft/hero2.jpg

That indeed is one hell of a preamp, probably cost one hell of a lot of money as well.


Going the hybrid route and using FETs, particularly in the power supply circuitry, is a designers wet dream.

Put simply the characteristics of power FETs is like a valve on steroids, so you get whatever benefits accrue from using valves but with much better performance, there is also the simplification of no heater required.

The individual heater regulators are a bit OTT possibly, as I wouldn't expect any crosstalk between stages via the individual heaters. However it does make any fault protection or fault finding that much easier.

:)

Thanks that goes some way to explaining why Glenn selects the things he does.

[Wakefield Turntables]

So tonight has been spent looking at what I don't need inside the amp and looking at areas which can be left alone. For example, do I really need to spend time and money on the Tape Input/Output RCA, do I need regulation for these areas,why should I need to buy a valve when I've no intention of using this option on the amp? Litttle things like these have been running through my mind. So I'm thinking the Phono In/Out, Line 1, and Main in/out could do with some magic, the others can just sit there for all I care in fact it would be nice to have an option to bypass them, remove them and then simplfy the circuit. More questions for Glenn! The transformer sitting in the corner also looks useful, could this be used for further power regulation in some other area of the amp's design? I'm also thinking that if I'm going to be using Charcroft resistors in the attenuator why not through the whole amp?

[Wakefield Turntables]

I've flung even more questions at Glenn. Poor bloke. I also understand Glenn produces certain mods for people with Tannoy speakers?? This could be interesting and it's yet another area that I'll have to question him (when I feel brave)! I've no idea if the usage of certain brands has any influence over how he designs his amps but I suppose its something else I could ask. Bloody hell this is certainly engrossing to say the least...... :cool:

[Wakefield Turntables]

Well for the couple of extra quid cost if looks like I'm going with Audio Note silver plated valve bases. Should be getting some more info from Glenn with regards resistor types and a myriad of other questions I asked him. Keep tuned....

[Wakefield Turntables]

Right I think thats all the research done I have a very good idea of what I want, now its a matter of implementation. Should know more over the weekend and hopefully a date when all this starts. Just listening to the little MicroBasic with some NOS mullard ECC82/3's and it sounds very nice but not quite as muscular as the stock Epoch.

[Wakefield Turntables]

Its starting....... :fingers:

[Jimbo]

Yo dude -this is going to be interesting!

Good Luck Andy hope it all turns out great!

[Wakefield Turntables]

Quick update. Well on with parts selection. Some new interesting alternative bolt-ons, some cleaning up of the RIAA curve and a few other bits and pieces, some upgrade ideas rejected and possibly some new ones. The saga continues....:D

[Firebottle]

Detail, details? :D

[Wakefield Turntables]

All in good time Alan, still putting the finishing touches to things. I'll be detailing things in the next few weeks.

[Lawrence001]

I'm still enjoying your old micro basic, it's now sitting in front of my restek challenger (which is running as a power amp). Speaking of power supplies it actually has 2 transformers whereas the 25 basic seems to only have one. I asked Glenn about it and he said: "It is a custom made Basic with a low gain, low output impedance line stage and one pot. Most Basic's had two transformers and 2 pots. The line stage on this amp will only work with the ECC82. It has the same regulated power supply as the current 25." Which I think means it should work nicely with some one off KT88 monoblocs I have bought?

[Wakefield Turntables]

Lawerence,

Nice to hear from you, I'm glad the old beast is still working. This Epoch I own may have something rather different with regards to power regulation, it's still being designed. We're not quite sure if it will offer much over what the Epoch's all ready got.

The parts for the mods have been ordered. The full list of mods is still being choosen. The amp may have some custom built internal wiring (in silver). I'll hopefully know more over the next few weeks.

[Simon_Nottingham]

I've recently got hold of a Croft Vitale (I've no real knowledge of Croft history and don't know where this sits in time or range in comparison to the Epoch) and it's my first piece of valve equipment.

It really is nice, but there is a fair bit of hiss from it. It's not noticeable when music is playing, but it's certainly there between tracks - is this normal? If not, what needs to be done?

[Wakefield Turntables]

I've recently got hold of a Croft Vitale (I've no real knowledge of Croft history and don't know where this sits in time or range in comparison to the Epoch) and it's my first piece of valve equipment.

It really is nice, but there is a fair bit of hiss from it. It's not noticeable when music is playing, but it's certainly there between tracks - is this normal? If not, what needs to be done?

No its not normal. Mail one of the Valve blokes.

[Simon_Nottingham]

No its not normal. Mail one of the Valve blokes.

Who would they be?

So one or more valves need replacing?

[Sovereign]

REXON

Your PM box is full

[Wakefield Turntables]

Mods now approximately 50% finished. :doh:

[Wakefield Turntables]

now finished, just some more work to do on some other amps and the Croft is coming home. So, one or two of the mods.

1. WBT silver RCA's in critical areas
2. Rewired silver in critical areas.
3. RIAA flattened out
4. Some special Yannis Tome designed internal wiring

:drool:

[Wakefield Turntables]

Mods now all done. I'll post some notes up later with regards what's been done. Just need to pick this up and then listen to some jazz.

[Marco]

Cool... Close-up piccies inside and out will of course be required for our perusal! :eyebrows: ;)

Marco.

[Wakefield Turntables]

So this is what's been done.

Mods
----
The Eichman phono sockets were replaced with WBT silver RCA outputs.
The RIAA has been corrected to within 0.2db accuracy.
The output now via L+R channels is within 0.2db
Internally its been rewired with silver.
The Seiden selector switch has been fitted.
The Khozmo attenuator has been fitted.
The tape circuit has been dismantled due to several components interfering with the signal path.
Yannis Tome 420+ litz cabling has been fitted to match my 420+ litz tonearm cable.
Additional internal silver + PTFE has been used to & from phono, Input selector volume and preamp.
The suggested SCR + Rike PIO caps were replaced with OIMP & Mundorf alternatives due to the latter not being made anymore.
The suggested Precision wirewound resistors were changed with Charcrofts / Audionote / Takman as needed.
We did not go down the route of individual regulators for each valve as what was already in was consider more than adequate for the job.
We did not do down the route of a separate transformer box with separate 500VA transformers for each channel. As the PSU was consider AOK.


The valves may get further regulation but not how it's been suggested by Glenn Croft. This is another story and another update.
A pure silver IEC may get fitted at some point. Hard wiring the mains leads was decided against.

[Wakefield Turntables]

Well the Croft has finally arrived home. This should have been home weeks ago but buying a new business can take up a lot of time. We it's in and sounding fantastic (so far) altough the valve system has had a little change due to a bloody awful ground loop hum with the paradise and a reshuffle of my equipment. So, the Garrard is plugged into my Ortofon SUT and Sugden Phonostage which I usually use on the 1210 setup. First impressions are very positive. I've noticed lots of subtle details on several when known recordings. Too early for a full down report yet.

[Wakefield Turntables]

Just a few pictures of the innards and outards!

17505

Silver WBT RCA's to replace the original croft gold plated jobbies. I only decided to have 3 sets done as I only intend to use these inputs.

17506

A quick pic to show some of the resistors used.
17507

Why is that custom Yannis Tome Litz 420 intrinsic wiring, why yes it is. :D
17508

A fancy volume thingy.

[Wakefield Turntables]

Fancy selector thingy...

17509

More silver intrinsic wiring than you can shake a stick at

17510

more big fancy caps, some Audionote stuff, Yannis Tome wiring, and other fancy gubbins.

Very nice. :D

[Jimbo]

Fancy selector thingy...

17509

More silver intrinsic wiring than you can shake a stick at

17510

more big fancy caps, some Audionote stuff, Yannis Tome wiring, and other fancy gubbins.

Very nice. :D

Sure got some sexy caps in there Andy, pure Croft porn! I bet when its run in about 3 years time it will sound awesome.:)

[Wakefield Turntables]

It's been two hours and the difference is massive, honestly. Clarity, transients, note edge's, surface noise, sound stage construction, all improved. It's far too early to really see where the improvements have fully manifested. I'm having dreadful ground loop hum with the paradise at the moment which is quite sad as this is my reference phonostage on the valve setup so I'm using the Ortofon SPU via the SUT and Sugden setup. I'm still extremely pleased with the outcome.

[Jimbo]

Can you take a piccy showing the valves and one of the front please:D You have a truly world class pre amp there Andy. Beautiful workmanship and if you come to sell it it I am waiting.:lol:

[Wakefield Turntables]

Can you take a piccy showing the valves and one of the front please:D You have a truly world class pre amp there Andy. Beautiful workmanship and if you come to sell it it I am waiting.:lol:

Valves are nothing specials, Sovtek!!! I'll post some pics of the valves if you want and the front of the amp tomorrow. I've been given some recommendations for valve replacements by Marco and Joe. I want to get a feel for how the amp sounds before a start to Toob roll.

[Wakefield Turntables]

Time to replace the crappy Sovtek tubes. I should have some NOS Mullard ECC35's by the end of this week :eyebrows: And if my bid is accepted some NOS RCA 6SL7 red bases. The amp continues to improve, currently listening to my DECCA FFSS recordings and they sound excellent.

[Wakefield Turntables]

Right, we are on! NOS RCA red base purchased from USA and the GT version on the black base Mullard ECC35. Tube rolling here we come.

[Wakefield Turntables]

Here we are for all tube geeks.

https://ssli.ebayimg.com/00/s/MTMyNVgxMTY2/z/-1sAAOSwuzRXfvcG/$_57.JPG?set_id=8800005007

And some RCA jobbies.
http://i.ebayimg.com/images/g/DgAAAOSwZtJW-jNv/s-l1600.jpg

Lets see what these can do for the Epoch.

[Wakefield Turntables]

Ground loop hum sorted, now some proper listening to Jazz through the paradise.

[Wakefield Turntables]

MUllards have now arrived, let's have some fun listening to them in a room at 30oC with a valve amp:(

[Macca]

So, despite the heat, is it ticking the boxes?

[Wakefield Turntables]

So, despite the heat, is it ticking the boxes?

Martin, yes it is. I intend to produce a write-up in the next few days detailing my findings. Stay tuned.

[Wakefield Turntables]

Starting to make some enquiries :eyebrows:.

[Marco]

Good stuff, Andy! So how were the 'posh' valves, compared with what was in it before? Both the RCA Red Bases and ECC35s should be stonking.... :)

Marco.

[Wakefield Turntables]

They sound great. Just playing around with some Mullards at the moment I've not even touched the RCA's. I'm looking into Valve regulation.

[Wakefield Turntables]

Getting upgradeitis again. Might have to get this booked in somewhere for some more work.

[Wakefield Turntables]

I decided to update my 6GV8 and 85A2 valves today in the Croft. I have no idea how old or knackered my current "billy no-name" valves are. So, we now have a General Electric and Tesla military grade jobbies on order. I have no idea what to expect but it makes sense to replace as just about everything else has been on this pre-amp :ner:.

[Jimbo]

I decided to update my 6GV8 and 85A2 valves today in the Croft. I have no idea how old or knackered my current "billy no-name" valves are. So, we now have a General Electric and Tesla military grade jobbies on order. I have no idea what to expect but it makes sense to replace as just about everything else has been on this pre-amp :ner:.

I had a whole bunch of 85A2 voltage reg valves to evaluate from Glenn. All the usual suspects and they did actually make a difference to the sound. Think I have an RCA and a Siemens left but I had some really rare stuff including one with radioactive signs all over the box!:eek:

[Wakefield Turntables]

I had a whole bunch of 85A2 voltage reg valves to evaluate from Glenn. All the usual suspects and they did actually make a difference to the sound. Think I have an RCA and a Siemens left but I had some really rare stuff including one with radioactive signs all over the box!:eek:m

Any conclusions? I just order a couple from Watford valves. 10 minutes and job done.

[Wakefield Turntables]

Oh dear, more upgrades (potentially). So I'm looking into getting the Croft modded with the following

Modded to accept 5691 valve's only
Dual mono power supply to each channel
Individual valve regulation.

Now looking at getting a few quotes.

[Vinyl turner]

I have noted references to upgrades to Croft pre-amps and realise there are numerous members who have undertaken varying degrees of this type of work.
And purely latching on to this particular thread to raise the question since it is the most recent on the forum.
From a very simplistic point of view (and I hold my hand up as knowing little about this subject) I presume everyone is initially eager to achieve the best 'bang for their bucks' and thereafter some of the work may be quite intricate/costly but still worthy of considering ?

Understandably we all have differing tastes and I expect what suits some will not appeal to others, but is there a generally accepted view that by carrying out 'such and such' - a certain result is achieved ?

Everything I read sounds very interesting and it would be good to know how those type of mods benefit your system(s).

I appreciate this is a big ask - but I suspect there isn't just me in the dark and hopefully others would equally benefit from knowing a few recommended mods. Thanks in anticipation.

[Jimbo]

There a lot of Croft amp users on this site Mark and I would say a good majority of us have had at least some modification done. Croft amps are hard wired (No PCBs) so they are easy to work on but obviously best to consult Glenn Croft himself as to what mods you want doing. I think we all start with a standard, off the shelf amp and then the quest begins! So much can be done with them it would be a long post to note them all and it would be good if the individuals who have had modifications did a write up of their own experiences. One of the simplest mods is too simply upgrade the standard valves to NOS which can gain you a considerable improvement in sound quality however all other mods usually require surgery.

The list of improvements can be endless but just to give you an idea of ares that can be improved:

Power supply - dual mono, separate box, increase in size
Line stage - change of valve type , more sophisticated arrangement to lower impaedance.
Socket and input/output connector upgrade
Capacitor upgrades
Valve regulation
Voltage regulation

All of these upgrades have a bearing on the sound to a greater or lesser degree.

In my case I had a 25R preamp upgraded to include a better line stage built around a better valve type and replaced all valves with NOS. This gave the amp a very noticeable upgrade in sound quality, more detail, bigger sound stage and more refinement. Later on I intend to improve the PSU, probably with a separate unit.

To get an Idea of other modifications and improvements Marco, Black Adder and Rexton have all had a fair bit of work done and it would be best if they detailed what this was, but I think most has been mentioned in posts by them over the last few years.

[Vinyl turner]

Thanks Jim,

Your wise words are always much appreciated :thumbsup:

[Firebottle]

Hi Mark, there are a few common upgrades that can be applied to most valve based circuitry that can improve performance.

As indicated adding power supply regulation is a good move as it improves the 'loading' on a valve stage, providing a more stable environment for the valve to work under.
There are other mods that can remove some or all of the non-linearity of frequency response of capacitors, particularly electrolytic types.

By far the best approach to improve performance is to engineer the valve circuitry to operate in the best linear fashion possible. All active devices, solid state or valve, have non linearities in their operating characteristics. By adding additional circuitry the operating conditions of a valve stage can be manipulated to force the valve to operate in a much more linear fashion, reducing distortion and giving a cleaner and more open sound.

I apply this approach in the valve/hybrid circuits I use.

[Vinyl turner]

Hi Mark, there are a few common upgrades that can be applied to most valve based circuitry that can improve performance.

As indicated adding power supply regulation is a good move as it improves the 'loading' on a valve stage, providing a more stable environment for the valve to work under.
There are other mods that can remove some or all of the non-linearity of frequency response of capacitors, particularly electrolytic types.

By far the best approach to improve performance is to engineer the valve circuitry to operate in the best linear fashion possible. All active devices, solid state or valve, have non linearities in their operating characteristics. By adding additional circuitry the operating conditions of a valve stage can be manipulated to force the valve to operate in a much more linear fashion, reducing distortion and giving a cleaner and more open sound.

I apply this approach in the valve/hybrid circuits I use.

Thanks Alan, That is all sensible sounding advice ......... and before I get totally out of my depth, I suppose the points that have been mentioned throw up a simple question from me (and I am half anticipating the answer) : is it cost driven criteria that prevents such 'improvements' being built into the pre-amps in the first place ?
i.e. would a £600 unit double in price if it was built with such refinements ?

Another schoolboy question from me - if these elements are altered, is there a pay off elsewhere down the line - such that (say for instance) clarity is improved but bass is reduced or are we always improving the baseline unit ?

I don't always ask a stream of questions and these are probably the only over-riding queries that apply to the whole range of potential upgrades.

Thanks everyone.

[Wakefield Turntables]

Croft now going to be potentially Firebottled!

[Jimbo]

Croft now going to be potentially Firebottled!

FrankenBottleCroft!:lol:

[Firebottle]

:eek: :lol:

@ Mark. Generally the price will be more if the build is more complex, so simple answer is yes.

There isn't any payoff further down the line providing there isn't a bottleneck anywhere. Improvements to one stage need to be replicated in further stages as necessary.

[Bigman80]

Croft now going to be potentially Firebottled!What you having done?

[Firebottle]

Secret, I'll make it up as I go along :ner:

[Bigman80]

Lol, fair enough.

[Jimbo]

Can you elaborate? I know what voltage regulation is, but I'm not sure what you mean by valve regulation.

I was referring to the fact you can have preamp either valve regulated or non regulated. I believe fets can be used rather
Than valves?

[Jimbo]

Sorry your not sure what I meant but I was referring to voltage regulation which can be either via valve implementation or other methods as you have alluded too.

Is that clear enough or do you need a more detailed explanation ?

[Jimbo]

I understand what voltage regulation is and I understand that you listed it as a possible upgrade. I didn't understand why your list of upgrades said:

Power supply - dual mono, separate box, increase in size
Line stage - change of valve type , more sophisticated arrangement to lower impaedance.
Socket and input/output connector upgrade
Capacitor upgrades
Valve regulation
Voltage regulation

Are you not an audio engineer?

[Jimbo]

I listed it like that as sometimes valve regulation could be called voltage regulation.

[Wakefield Turntables]

What you having done?


See post #68

[Bigman80]

See post #68Ah, yes.

That's going to be a comprehensive unit when you've finished

[Firebottle]

Andy your inbox is full. 834 on its way back.

[Wakefield Turntables]

Finally the old girl is going for it's latest rounds of mods. No time scale, cost no object!

Stay tuned! :hotrod:

[Mikeandvan]

I find the bass too woolly/boomy on my Croft micro phonostage, so I've just carried on using the G Slee Era V into line 1.

[Wakefield Turntables]

Mike. I'm going to write a review about my experiences with the new Croft modifications. It might take a day or so but should make for good reading.

[Jimbo]

Looking forward to that Andy.:)

[Mikeandvan]

Mike. I'm going to write a review about my experiences with the new Croft modifications. It might take a day or so but should make for good reading.
Look forward to it, mine was also sent off to Alan and came back improved.

[Wakefield Turntables]

More mods are a comin.....

[Jimbo]

More mods are a comin.....

Croft mods?

[Wakefield Turntables]

Two boxes with bigger power supplies. Maybe full dual mono channel separation with fancy pots and then whatever else Glenn things might be worthwhile.

[Jimbo]

Two boxes with bigger power supplies. Maybe full dual mono channel separation with fancy pots and then whatever else Glenn things might be worthwhile.

Awesome!

[Wakefield Turntables]

Just realised, this never happened, nor ever will. :(

[Jimbo]

Very sad mate.