Croft

[johanjongstra]

This week I did some tube rolling. To be sure what I did I asked Glenn and he gave some very good advice. What I did

• In my 7 mono (no R or RS), bought second hand, where loaded with ECC99. Glenn gave me the tip for NOS 12bh7a's. I found a matched pair in Germany from GE. They really sound fantastic.
• The line stage of my 25R preamp, was loaded with the standard JJ ECC83S. Glenn gave me the tip to also try the 12bh7a. So I found one Sylvania NOS. I noticed that the bass performance is a little thin. But after a considerable warm-up time, at least 45 minutes the sound is opening up and gives a very good result.
• For my RIAA (also the standard version) I try to find a pair of Tesla E83C, but ohoh... they are expensive!

If all this isn't enough I also changed my Metrum Octave MKII DAC for a Metrum Hex, which I found second hand. A very big difference aswell.
For now I am going to enjoy some music!

 

[Sotosound]

This week I did some tube rolling. To be sure what I did I asked Glenn and he gave some very good advice. What I did

• In my 7 mono (no R or RS), bought second hand, where loaded with ECC99. Glenn gave me the tip for NOS 12bh7a's. I found a matched pair in Germany from GE. They really sound fantastic.
• The line stage of my 25R preamp, was loaded with the standard JJ ECC83S. Glenn gave me the tip to also try the 12bh7a. So I found one Sylvania NOS. I noticed that the bass performance is a little thin. But after a considerable warm-up time, at least 45 minutes the sound is opening up and gives a very good result.
• For my RIAA (also the standard version) I try to find a pair of Tesla E83C, but ohoh... they are expensive!

If all this isn't enough I also changed my Metrum Octave MKII DAC for a Metrum Hex, which I found second hand. A very big difference aswell.
For now I am going to enjoy some music!

Are you able to provide some details about the differences that you heard?

For instance, did the overall character of the sound change significantly, or was the sound simply more of the same but better, or......?

 

[johanjongstra]

Are you able to provide some details about the differences that you heard?

For instance, did the overall character of the sound change significantly, or was the sound simply more of the same but better, or......?

Yes, I could say with the standard JJ the sound is actually instantly constant and balanced. A good sound, nothing wrong with it. The Sylvania sounds at first thin in the bass, a little grainy in the high's. The lower octave seems to be undefined, less detail in low notes on a double bass for instance. Surprisingly the Sylvania makes up big time when it gets warmer and warmer and after a while, let's say 30-45 minutes it is a joy to listen to. The bass is there in detail, definitly in good balance with mids and highs. It sounds more natural to me. It has the right 'warmth' for me.

 

[basa71]

My Croft 7R monoblock amps are now tube rolled with 1950s black plate RCA's the same as the RIAA R above.
Everything sounds fantastic. I'm very happy.
My tube rolling has started and finished within a week. Nice and easy. Just the way I like it.

Congrats UncleMeat, although I doubt it has finished

 

[Hummer]

I have noticed a few folk have used tube damping rings on their valves in Croft gear in order to stop vibration and the subsequent microphonic effects which can find their way into the audio chain. I used very similar tube damping rings throughout my Croft 25R phono stage and Croft 7 power amp but recently I removed them and used some Silent Coat damping material on the inside of the Case lid. I found this much more effective than using tube rings.

Any vibration from the toroids or the case that may get through to the valves will have a negative effect so preventing this happening is definitely worthwhile. In my instance the sound once the case is damped is more focussed and there is a bit more precision and detail in the recorded information.

You do not have to use too much of this material. Experimenting a little at a time is best. I found using 2 x 4cm squares on the side of the case lid and 2 x 4cm squares underneath the case lid did the trick.

 

[Hummer]

I have been using the Croft 25R for six years or so and have had the line stage upgraded to RS spec with non inductive capacitors and a move to the 12BH7a valve in the line stage, however I am thinking I may move up another level to either an RIAA or RIAA R with a separate dual mono line stage. I will ponder this for a while but in the meantime here are a few photos of the modified Croft 25R.

 

[Hummer]

Ok so my Tube rolling question is - The tubes in my Pre have already been upgraded by the previous owner and sound great.

Where do I go next? The 7R mono's or the RIAA R?

If its the mono's which I believe have 2 x valves in each do I change both?
The RIAA R has 5 x valves in. Which ones do I change. The 3 on the left or the 2 on the right. Or all of them?

Sorry for the newbie question but we all have to start somewhere

Hi Uncle meat are you also known as Thing Fish?

 

[Ian]

Hi Uncle meat are you also known as Thing Fish?

And probably Mr. Hot Rat

 

[UncleMeat]

Hi Uncle meat are you also known as Thing Fish?

Yes, on a couple of forums.

 

[Hummer]

A nice pair......Croft 7R monos.

These sounded very good indeed and were very refined but I actually prefer the Mono Croft 7 unregulated to the Croft 7R.

If anyone is interested you can actually run two Croft 7 stereo amps as Monos and you can also use a jumper lead to put the input into both channels and use one channel for the bass and one for the top end if your speakers are bi-ampable. Or you can use a jumper cable to put the input into both channels and link the two positive output together with a short piece of wire - this will combine both channels together to give a bit more power and a lower output impedance.

 

[johanjongstra]

Pure Audio Project, Duet 15 prelude speakers and Croft

As I wrote a little about my setup earlier as a relative new Croft owner, maybe you appreciate my newest find.
I changed my Totem Forest speakers for the PureAudioProject Duet 15’s. They are open baffle speakers loaded with an especially for this speaker designed 15” woofer and a broadband speaker, the Voxativ AC-1.6. They also have a specialy designed Cross-over with Mundorf components.
I saw these speakers a few years ago at an audioshow in Holland and was immediately impressed with them at that time. Because the Totems never felt right in my room acoustic, I thought an open baffle speaker could help solving the problem.
Pure Audio Project is an Israeli/American brand and sell their speakers online only. So I wasn’t able to review on forehand. I contacted the owner Ze’ev Schlick to ask advice how those speakers would behave with the Croft 7 mono’s. Luckily he had experience with Croft and was enthusiastic about the combination. So based on that and my earlier experience I decided to buy the Duet 15’s.
Now the speakers are burnt-in and opened up, I must confess…. These are amazing sounding speakers. The combination with Croft is incredible. To describe I could use a few words: totally transparent and disappearing in my room, deep but very detailed bass. The mid’s and high’s are of an unearthly quality. No sign of harshness in forte string or vocal pieces (a real problem with my Totem’s). The woofer and the Voxativ's give a total coherent image and wide sound stage.
If you want something different and are into new speakers for your Crofts I can highly recommend these speakers. The Duet’s are the smallest (well small… with a 15” woofer) but there are a few other models that are bigger. I would say: take a look at their website. The customer service is also very direct and of great quality.

 

[Hummer]

I have read very good reports about Open Baffle speakers, I can imagine this set up with the Croft amps sounds great.

 

[calorgas]

Been playing with a Croft Micro 25 Basic phono into a Quad QSP for a few days. It has the single vol pot option which is good (for me).

I like it, but possibly not enough to make this a permanent setup. What improvements would the regular Micro 25 bring? Smoother, more refined?

 

[The Bish]

Been playing with a Croft Micro 25 Basic phono into a Quad QSP for a few days. It has the single vol pot option which is good (for me).

I like it, but possibly not enough to make this a permanent setup. What improvements would the regular Micro 25 bring? Smoother, more refined?

Are you using the stock JJ valves? I'm using a modified 25R with a QSP and really like the sound, but I have had the gain / impedance on the Croft's linestage output reduced as the QSP is quite sensitive, and using some nice 12bh7a valves which do make a large difference. If it's the stock Ecc83 linestage with the JJ valves I reckon it's worth trying a 5751 before upgrading the pre.

 

[calorgas]

Are you using the stock JJ valves? I'm using a modified 25R with a QSP and really like the sound, but I have had the gain / impedance on the Croft's linestage output reduced as the QSP is quite sensitive, and using some nice 12bh7a valves which do make a large difference. If it's the stock Ecc83 linestage with the JJ valves I reckon it's worth trying a 5751 before upgrading the pre.

Yes I am currently using the stock JJ ecc83 in the linestage. I have some other ecc83 though don't currently have a 5751 I could try, but I'd actually inserted my diy-stepped-attenuator-single-input-pre between the Croft and the QSP to reduce the gain as I figured that was pretty much the same as using an inline attenuator, but with the advantage of being able to set the level of attenuation I wanted.

Any particular brand/manufacturer of 5751 that you'd recommend?

Gain issues aside, I guess what I'm pondering is what does the next step up the Micro ladder bring to the table?

 

[The Bish]

Yes I am currently using the stock JJ ecc83 in the linestage. I have some other ecc83 though don't currently have a 5751 I could try, but I'd actually inserted my diy-stepped-attenuator-single-input-pre between the Croft and the QSP to reduce the gain as I figured that was pretty much the same as using an inline attenuator, but with the advantage of being able to set the level of attenuation I wanted.

Any particular brand/manufacturer of 5751 that you'd recommend?

Gain issues aside, I guess what I'm pondering is what does the next step up the Micro ladder bring to the table?

Try a Raytheon windmill getter 5751 or RCA JRC, I can lend you one to try if you like. Not sure about the difference between the basic and the 25, but my experience of going from a basic to a 25r is more detail and smoother tone.

 

[calorgas]

I certainly trust your judgement but those Raytheon and RCA valves are a bit pricey for me, I'm just not ready to throw £100 at a single valve

Maybe I should try a new production valve first, and if I like the general effect then perhaps I could take up your kind offer of a loan of a really nice one, to see if I could justify spending the extra £££.

 

[basa71]

I received an update from Glenn that I thought I would share:

"Sorry that you’re still not happy with the sound of the pre – we’ll get it sorted.
Valve changes are a good starting point – I’ll sort some out from my collection and send them to you to try out – beyond that I would look to make some circuit mods to make it closer to the original. You could also try ECC82s in place of the 12BH7as if you have some"

As ever the helpful man he is, customer satisfaction above all. With which other audio company would you ever get service like this? I heard Teddy Pardo is doing good too, beyond that I wouldn't know of any..

Thank you also Nathan for your tubes, I will be testing them soon.

Bastiaan

Okay.. I thought I give you all a bit of an update on my quest for the missing lows in my system.

Glenn advised me to upgrade the 7 to R spec in his usual shorthand. I Then spoke with a Croft and Harbeth dealer in the Netherlands, who explained a bit more.. he told me that the Harbeth 30.1’s in particular are very hungry and can not function properly on the standard 7. The 30.2’s are actually working better in the 7 than on the 7r, following this Dutchman.
Not wanting to keep sending amps back and forth to Glenn, I asked him what else he could do to the 7.. He suggested lowering the gain by using the amplifier stage used in the mono’s; that certainly solved the high gain issue out, he also used various better capacitors and resistors, naming the baby 7R+.

I am nothing short of flabbergasted. The improvements are incredible. I have all my low back and with effortless control. The mids and highs are better controlled and the soundstage is improved.
Glenn is a real artist, it would be so sad to see him stop doing his magic, I really hope there is some consistency plan in place.

I am one happy man, with a big amount of music to plough through again, discovering all my favourite tunes yet again. Bring it on!

Now I’m just looking for tips on what tube to use in the 7R line stage. I have tried a grey plate Sylvania, a black plate RCA and the stock JJ. RCA sounds warmest, the JJ the brightest, Sylvania falls neatly in the middle. I am completely unsure what I prefer. Is there anything else I should try? All advise appreciated!

I guess there’s not much point in upgrading the regulated tube from stock JJ?

 

[basa71]

A nice pair......Croft 7R monos.

These sounded very good indeed and were very refined but I actually prefer the Mono Croft 7 unregulated to the Croft 7R.

If anyone is interested you can actually run two Croft 7 stereo amps as Monos and you can also use a jumper lead to put the input into both channels and use one channel for the bass and one for the top end if your speakers are bi-ampable. Or you can use a jumper cable to put the input into both channels and link the two positive output together with a short piece of wire - this will combine both channels together to give a bit more power and a lower output impedance.

Just out of interest, Hummer, what speakers are you driving? As I just learned that for instance the Harbeth 30.2 is better off with the 7, where the 30.1’s definitely need the 7R! I found this out the hard way as you can read in my posts

 

[Hummer]

I

Just out of interest, Hummer, what speakers are you driving? As I just learned that for instance the Harbeth 30.2 is better off with the 7, where the 30.1’s definitely need the 7R! I found this out the hard way as you can read in my posts I

Just out of interest, Hummer, what speakers are you driving? As I just learned that for instance the Harbeth 30.2 is better off with the 7, where the 30.1’s definitely need the 7R! I found this out the hard way as you can read in my posts

I am using some German Heco Celan GT702 large floorstanding speakers. They are very easy to drive as they are 92db efficient.