Croft Micro Basic - Loud input

[RichB]

Anyone with any experience of these preamps find they are very loud with digital sources?

Connecting up my Rega DAC this afternoon and playing some times from the laptop I barely need to turn to dual pots before it gets way too loud with the croft feeding my NVA monos. I don't have this issue with any other sources.

I've had to switch the laptop to 'direct sound' output in JRiver so I can turn the volume down in the software just so I can get the slightest bit of attenuation using the Crofts dual volume pots. The resulting sound is very good though and my hissing has disappeared following some of the tips given in my gallery thread.

Are Crofts always this sensitive? Is this what we'd call an impedence mismatch between the Rega and the Croft or is the croft pushing the NVA monos too much? The NVA don't seem too fussy with other inputs. Would some rca attenuators take it down a bit and give me a better range of control from the Crofts pots?

[Haselsh1]

I owned a Croft Micro Basic back in 2009 and I used attenuators with it, Goldenjacks to be precise at -14db. I have only just bought another Micro Basic but these days find it OK and not too loud. I am using Rotel RB850 bridged mono's with it at the moment however the volume pots are still at the ten past position which is a tad too sensitive. I think that the Micro Basic is a better match with my Rotel's than it used to be with my Series Seven.

[struth]

http://www.amazon.co.uk/gp/product/B0057G44WM?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00 .......these are adjustable

[orbscure]

I used a pair of Rothwell 10dB in line attenuators when it was mine Rich..

[DSJR]

Glenn can reduce the gain of his preamps, probably to unity gain (output same level as input) but I do have to ask again -

WHY are you driving NVA's with a buffered line stage as there's one already doing the job in the amp circuit?

I know we've been here before and I'm sincerely sorry if I appear to lecture yet again, but the whole point of the NVA amp design is to have a high gain power amp and use it with a passive preamp not too far away. To this end, the 'line buffer' components that would normally be used in a powered preamp are actually on the input of the power amp board and the input impedance set accordingly.

The above scenario isn't quite the same IMO as say, the older transistor Quad power amps that utilised the 4 pin DIN connection, as the input gain for those amps added distortion and noise.

The Croft Micro basic is a fun thing, but isn't by any means as 'clean' sounding as the Micro 25. I honestly believe that you're injecting added distortion and some noise to the NVA which isn't there in the sources you use. I do agree that passive preamps aren't suitable for all occasions, but for YOUR power amps, I think they're ideal and necessary.

Sorry Richard (Bunsen Burner? :)), I know I'm not saying what you want to hear, but something like a Tisbury or Icon Audio passive (if you don't want or like an NVA) passive pre really is the way to go. I'd probably ask for one with a 47k log pot inside if that's possible, although 10k seems fine as well (my electronic ignorance prevents me from saying what if any differences there are - with the NVA amp circuit - ). Attenuating what you have is daft IMO and will add yet another potential veiling level to what you already have - in my opinion.

Hope the above is helpful and not just a me-too style of lecture. You should know by now how much I love Glenn Croft's products, but to get the proper levels of transparency in his preamps to a P50 - in your system - I do feel a 25R at least would be necessary. I use a 'home made & ghastly looking' stripped P90-clone in my office/workshop system, using just three inputs and two plastic film 47k log pots with one output set and I have no hum, added noise and bass power aplenty! My Croft 4PP does change the sound a little, although far less (and not annoyingly so) than it did when I bought it some years ago.

[RichB]

Glenn can reduce the gain of his preamps, probably to unity gain (output same level as input) but I do have to ask again -

WHY are you driving NVA's with a buffered line stage as there's one already doing the job in the amp circuit?

I know we've been here before and I'm sincerely sorry if I appear to lecture yet again, but the whole point of the NVA amp design is to have a high gain power amp and use it with a passive preamp not too far away. To this end, the 'line buffer' components that would normally be used in a powered preamp are actually on the input of the power amp board and the input impedance set accordingly.

The above scenario isn't quite the same IMO as say, the older transistor Quad power amps that utilised the 4 pin DIN connection, as the input gain for those amps added distortion and noise.

The Croft Micro basic is a fun thing, but isn't by any means as 'clean' sounding as the Micro 25. I honestly believe that you're injecting added distortion and some noise to the NVA which isn't there in the sources you use. I do agree that passive preamps aren't suitable for all occasions, but for YOUR power amps, I think they're ideal and necessary.

Sorry Richard (Bunsen Burner? :)), I know I'm not saying what you want to hear, but something like a Tisbury or Icon Audio passive (if you don't want or like an NVA) passive pre really is the way to go. I'd probably ask for one with a 47k log pot inside if that's possible, although 10k seems fine as well (my electronic ignorance prevents me from saying what if any differences there are - with the NVA amp circuit - ). Attenuating what you have is daft IMO and will add yet another potential veiling level to what you already have - in my opinion.

Hope the above is helpful and not just a me-too style of lecture. You should know by now how much I love Glenn Croft's products, but to get the proper levels of transparency in his preamps to a P50 - in your system - I do feel a 25R at least would be necessary. I use a 'home made & ghastly looking' stripped P90-clone in my office/workshop system, using just three inputs and two plastic film 47k log pots with one output set and I have no hum, added noise and bass power aplenty! My Croft 4PP does change the sound a little, although far less (and not annoyingly so) than it did when I bought it some years ago.

Hi Dave, I'm just trying stuff out. I normally use a passive pre but I'm just trying out the Croft for giggles really. At the price I picked it up it was just something I fancied trying and I can flog it if it don't work out.

It actually sounds really great with the NVA monos its just the input is quite hot. Sounds like others have had similar issues and used attenuators to get around it.

BTW I'm Britpop in the other place :-)

[jollyfix]

Hi Rich, i can send you some Rothwell attenuators for you to use. I also have a Kimber IC with built in -14 Attenuators, any good for you? you can give them a go if you want.

[RichB]

Hi Rich, i can send you some Rothwell attenuators for you to use. I also have a Kimber IC with built in -14 Attenuators, any good for you? you can give them a go if you want.

That's good of you Dave. I'll try them out for sure and if they do the job I'll invest in some.

[jollyfix]

Ok, i will post them to you start of next week.

[RichB]

Ok, i will post them to you start of next week.

Thanks Dave:) what were you using them with? I take it you don't need them now?

[simon e]

Rich I've owned a micro basic which was ordered from Glenn with reduced input sensitivity. I then upgraded to a used micro 25, I spoke to Glenn and he offerred to reduce the sensitivity or tell me the components in the feedback loop to change.

There are 2 resistors to change. If you can solder it's not difficult just fiddly.

[jollyfix]

Thanks Dave:) what were you using them with? I take it you don't need them now?

I bought them just for some experimenting as i tend to listen at lower volumes. I swap IC around now and again, they dont fit the Epiphany cable im using at the 'mo'. The Kimber cable also not in use, its in the snake nest cable draw along with the Nordost, VDH,Chord,Merlin etc.......

[DSJR]

Actually, the gain on early Micro 25's was a touch too high for Glenn's own power amps. If twelve o'clock is minimum, then the sound could be loud at two o'clock and deafening at anything over four o'clock on the pointers. Last time I was at hifi Dave's place, his Croft preamp was comfortable in volume at well past three o'clock, so I wonder if Glenn may have tweaked the gain in production?

[The Barbarian]

Forget about CDee they are more trouble than wot they are worth. There problem solved. :D