Croft specs - too much gain?

[Pharos]

The Croft phono stages are high gain, too high in my opinion.

That was the impression I got, and just a change in a couple of resistors in the cct would fix it.

[hifi_dave]

Or, if it's a problem to you, swap a valve but really, it doesn't affect the majority of owners.

[Wegamus]

Or, if it's a problem to you, swap a valve but really, it doesn't affect the majority of owners.

I’m surprised to hear that Dave, as it’s a fairly common issue to read about on forums. As I showed in the specs on my first post, the preamp gives the full 0.5V the power amp needs for it’s rated output at only 1mV input. Now, a standard 5mV MM cart won’t overload it, but this is the cause of the volume control cramping, which in my system is too loud at 3 o’ clock. It’s worse with a digital source where the preamp gives the 0.5V for a tiny 0.15V input, yet most sources are about 2V. I make that about 13 times too much. Why such high sensitivity? It just leads to numerous threads like this trying to sort it, or people moving the equipment on quickly which harms the value retention, it’s just puzzling and frustrating.

The hiss is apparent even with my Harbeth M30.1, if I had Tannoys or other reasonably sensitive speakers it would be a very serious problem. I just genuinely don’t understand why it’s been designed this way, I mean what’s the purpose in making a super high-gain amp that causes hiss and volume cramping even with low sensitivity speakers? What’s the benefit of doing things that way rather than designing for real world source scenarios? Not trying to attack Croft - long may they continue, they sound great and I’m keeping mine. Just needs a design tweak to make them more useable.

[Audio Al]

I can only think it must be the 7R as the 25R was totaly silent in my use with various amps

[Wegamus]

I can only think it must be the 7R as the 25R was totaly silent in my use with various amps

My previous 25R was nice and quiet with a Radford STA25/3, and also yesterday I used my new 25R line-outs into a NAD integrated and it was silent too. Didn’t get much range on the volume control with the Radford, although it was a bit better in that way than the 25R/7R combo.

I’ll get it sorted one way or another. If the new valve doesn’t sort it - and I’m assured it will - I’ll ask Glenn nicely to change the resistors to whatever.

[hifi_dave]

I’m surprised to hear that Dave, as it’s a fairly common issue to read about on forums. As I showed in the specs on my first post, the preamp gives the full 0.5V the power amp needs for it’s rated output at only 1mV input. Now, a standard 5mV MM cart won’t overload it, but this is the cause of the volume control cramping, which in my system is too loud at 3 o’ clock. It’s worse with a digital source where the preamp gives the 0.5V for a tiny 0.15V input, yet most sources are about 2V. I make that about 13 times too much. Why such high sensitivity? It just leads to numerous threads like this trying to sort it, or people moving the equipment on quickly which harms the value retention, it’s just puzzling and frustrating.

The hiss is apparent even with my Harbeth M30.1, if I had Tannoys or other reasonably sensitive speakers it would be a very serious problem. I just genuinely don’t understand why it’s been designed this way, I mean what’s the purpose in making a super high-gain amp that causes hiss and volume cramping even with low sensitivity speakers? What’s the benefit of doing things that way rather than designing for real world source scenarios? Not trying to attack Croft - long may they continue, they sound great and I’m keeping mine. Just needs a design tweak to make them more useable.

Forums are forums but in the real world, where I sell Croft every week and have done for way over 30 years, I rarely have anyone point this out as a problem. On the few occasions it has been an issue, the gain has been reduced without any fuss.

As to "hiss", Croft are about as quiet as they get and using a line input are deathly quiet.

[Wegamus]

Forums are forums but in the real world, where I sell Croft every week and have done for way over 30 years, I rarely have anyone point this out as a problem. On the few occasions it has been an issue, the gain has been reduced without any fuss.

As to "hiss", Croft are about as quiet as they get and using a line input are deathly quiet.

On my Croft Integrated Phono, I agree it’s nice and quiet, but the hiss I’m getting now with 25R/7R/M30.1 is the loudest I’ve ever heard by some margin - more than my 50+ year old Radford - and several others have reported the same. Maybe my particular amp is faulty? But then Glenn even knows what to do to stop it so it seems to be a known issue or deliberate characteristic. Perhaps your many customers don’t like to make a fuss? I generally don’t, but hiss at this level is abnormal.

So perhaps some are ‘deathly quiet’ and other units are ‘loudest in memory’? I can easily hear it on low level parts of the music (am currently playing a DAC with its digital volume reduced by 50% and am still only at 1:30 on the 25R volume control!) and when no music is playing the Croft hiss is the loudest sound in the room. It’s not normal at all. As I say, maybe my unit is faulty but I think it’s obvious from the specs that this is the result one would expect.

Anyway, I have a 12BH7A in the post so fingers crossed.

[Wegamus]

Here’s a photo showing the volume control position for normal listening level in my living room with my DAC as the source at full output (2V). As you can see it’s barely cracked open:

[Barry]

The output from a CD player will easity overload the 150mV sensitivity of the line input. You need a 14dB pad between the two items.

But as you are also experiencing the same problem on 'disc', the entire gain of the preamp needs to be reduced. I would contact Glenn for advice.

[Wegamus]

The output from a CD player will easity overload the 150mV sensitivity of the line input. You need a 14dB pad between the two items.

But as you are also experiencing the same problem on 'disc', the entire gain of the preamp needs to be reduced. I would contact Glenn for advice.

Makes you wonder why it’s designed like that in the first place! Does anyone have a line source that outputs 0.15v these days?

Also, at 5mV my cart is 5x higher output than is needed for the power amp to give it’s rated output. Sadly, I don’t happen to have an old 1.05mV EMT cart here though...

In your view does this explain the hiss I’m getting and are the hiss and volume control issue separate problems? I didn’t have this problem with the Radford power amp although I still did have a pretty cramped volume control on the 25R. It seems the 7R is more the culprit but the 25R is too to an extent.