Phono stage output into passive preamp?

[HighFidelityGuy]

Hi,

I'm currently working on getting my first turntable up and running and while looking into various things I need to purchase to make this happen, I noticed something that I thought I better get some advice on:

I noticed that the output voltage of most phono stages is rather low, in the <1V region. My preamp is passive and my power amps need 2.23V to make full power. So I'm rather worried that most phono stages won't work well for me as they don't seem to amplify the signal enough. What I don't know is whether the phono stage output voltages I've been reading are peak to peak or RMS or whatever. I know the poweramp input voltage of 2.23V is RMS, which makes sense as that's around the value most CD players etc output.

Can anyone help clear this up for me as I'm a little unsure if I'm going to have problems or need to make special considerations when choosing a phono stage?

Cheers. :)

[hifinutt]

i wondered the same with my cyrus tuner which outputs a very small 775mv . i don`t know how that equates to your output but the tuner sounds fabulous . my passive is a music first classic and i don`t use the gain switch

[John]

I used to have run a phono stage through a passive, you will need plenty of gain 65db at least if using a mc, it will also depend on your cart as well.

[HighFidelityGuy]

Thanks for the replies.
I'll be using an MM cart at first to keep things simple. Specifically it will be an Audio-Technica AT120E (http://www.soundhifi.com/AT120E.html).

Cheers.

[HighFidelityGuy]

If it helps to know which phono stage I'll be using, these are the two I like the look of the most so far but I am seriously thinking about building one from a diy kit:

Clearaudio Nano (http://www.clearaudio.de/eng/pv_nanophono.html)
Pro-Ject Phono Box SE II (http://www.project-audio.com/main.php?prod=phonoboxse&cat=boxes&lang=en)

They both have the features I'm looking for and seem to get high praise for being excellent value for money from what I've read online. They also fit into my sub £200 price bracket. I don't want to spend a fortune at the moment as this will be my first TT setup, so I just want a reasonable starting point to upgrade from.

My TT will be a Pioneer PL-71 once I've finished repairing it.

Cheers.

[Dave Cawley]

None of these will give you enough gain. Expecting a Phono stage to give over 6 volts peak to peak under normal conditions is a bit much.

The system you have is not really ideal, and I think this will just compound the underlying issues.

Dave

[John]

I would speak to Dave C about this as this is something he does for a living

[HighFidelityGuy]

Balls, that's p*ssed on my bonfire. :doh:
Thanks for the the info Dave.

To be honest, I guess there's no reason why I need my power amps to produce full power, they're stupidly powerful so I probably don't need the full 2.23V RMS input. So I'm not too worried about that but it sounds like I'll need more voltage than most standard phono stages produce.

As I really don't want to replace my brand new preamp, I guess I either need to find a phono stage that has an output as close to 2.23V as possible or I need some kind of extra preamp to go between a standard phono stage and my passive preamp to boost the signal.

So if anyone knows of a good phono stage for around £200 that has an output voltage over 1V RMS I'd be interested to know?

If that's not possible then this brings me back to a similar question I posted in another thread:

I have a valve based preamp that I bought off ebay a few months ago. It's from China and needs some repair work doing. I was planing on using this as my main preamp but I decided that the costs involved in giving it the features I needed and the uncertainty over whether it would work well were not worth the hassle. So it's still in it's box waiting to be used for something else.

I wondered whether it was possible to turn this into a phono stage by adding an RIAA EQ circuit but was advised this was folly. Looking at the problem I now have, I'm starting to wonder if I could use the valve preamp but in a slightly different way to what I first imagined.

I could remove the cheap and nasty volume control and input selector etc from the valve pre-amp and just make it a simple stereo fixed level preamp. This could then be installed between a standard phono stage and my passive preamp.

So do you think this could work well to allow me to continue using my passive preamp?

Cheers. :)

[Dave Cawley]

I could modify a NAD PP 2 to do it though? I still can't recommend this sort of system though.

Dave

[HighFidelityGuy]

Hi Dave, thanks for the offer, I'll certainly consider that.
Just so I understand what you mean when you say you "don't recommend this sort of system" is it just the fact that my preamp is passive or is there some other reason my system isn't suitable for use with a TT and standard phono stage?

Cheers.

[Themis]

A Croft preamp could be a solution, perhaps ? It has a fixed line out. ;)

[HighFidelityGuy]

A Croft preamp could be a solution, perhaps ? It has a fixed line out. ;)

Even though Glenn's cheapest preamp is a bargain price it's still £350 more than I'd like to spend if I don't have to. Besides I still don't know if this type of thing will work very well. I need to get more info off Dave C or someone about the problem. Cheers. :)

[HighFidelityGuy]

I've been looking into this a bit further to try and expand my understanding of the subject and it seems that I hadn't realised that two different products were available, a phono stage and a phono preamp. It seems that I will need the latter, or at least something that equates to this. The part I need to understand is exactly what is the difference between a phono stage and a phono preamp? Seen as a phono stage is designed to re-EQ the recording and boost the signal, I can only assume that a phono preamp does the same but boosts to signal a bit more?

Also, in a simple setup of TT>Phono stage>active preamp>power amp>speakers, the signal from the phono stage is boosted by the preamp before it's sent to the power amp. The volume control on the preamp then reduces the signal between the two to achieve the desired listening level. So as far as I understand it, the volume control is acting as a very simple passive preamp but there's a line level amplifier in front of it.

Is any of the above correct or have I got mixed up.

Cheers. :)

[therockst4r]

@HighFidelity, a phono preamp boosts the phono signal to line out, so it can be used in any standard rca line in.

[HighFidelityGuy]

Thanks Anthony.
So is there any difference between the amplifier circuit in a phono preamp and that in a standard active preamp? I'm guessing there may be some impedance or gain differences but I don't know.

[therockst4r]

Thanks Anthony.
So is there any difference between the amplifier circuit in a phono preamp and that in a standard active preamp? I'm guessing there may be some impedance or gain differences but I don't know.
Those are precisely the differences between the two. The gain and impedance on an active preamp and a phono preamp are completely different. What you need to buy is a phono preamp.

[HighFidelityGuy]

Those are precisely the differences between the two. The gain and impedance on an active preamp and a phono preamp are completely different. What you need to buy is a phono preamp.

Just to make sure I understand fully, when you say that the gain and impedance are different, are you comparing the whole phono preamp to a preamp or just the preamp stage of the phono preamp to a preamp? I hope that makes sense. :)

[therockst4r]

Just to make sure I understand fully, when you say that the gain and impedance are different, are you comparing the whole phono preamp to a preamp or just the preamp stage of the phono preamp to a preamp? I hope that makes sense. :)

I am not quite sure of what you are asking. What I meant was that the gain and impedance of a phono preamp are not like those found on an active preamp.

[HighFidelityGuy]

Sorry I'll try and explain better.

I understand that a phono preamp as a whole will have different gain and impedance than a normal preamp because the input of the phono preamp needs to have the correct loading for the cartridge.

The bit of the phono preamp I'm trying to understand is the extra amplifier circuit it must have that a simple phono stage doesn't have. So if we treat the phono preamp as being a phono stage with an extra preamp included, what is the difference between this preamp stage and a standard active preamp? Obviously a standard preamp has multiple inputs and a volume control but if you ignore those and concentrate on the basic line level preamp part.

Cheers. :)

[Primalsea]

Hopefully this wont sound as if its grating against anything advice already sent. A phono preamp and a phono stage are the same thing but not to be confused with a preamp with a phono stage built in so you dont need a separate preamp and a separate phono stage.

The issue with passive preamps (a misnomer as they only attenuate, not amplify) is that the preceding item (in this case a phono stage) must have a low output impedance that is capable of driving the passive preamp and cables so as not to suffer from HF roll off. Most good phono stages will be OK TBH.

Valve based preamps for the most part tend actually to be effectively a passive preamp followed by the amplifying stage. The crux of this is that if a phono stage works well with a valve based preamp its likely it will work on a passive preamp.

In real world situations the volume knob never goes past 12 o clock lest we be made deaf and only a tiny fraction of the maximum output from a preamp is needed to have loud music bless our ears. The attenuation of the passive preamp maybe a blessing as you will be using the volume knob in its middle to upper ranges. This gives bonus In the middle ranges potentiometers tend to have much better channel matching.

[HighFidelityGuy]

Thanks Paul, that's taught me a few things I didn't know! :)

So if I find a phono stage with a low output impedance I may (but maybe not) have a chance of getting this to work. I know my power amps have a high input impedance as I checked that out before buying my passive preamp. My preamp and power amps work well together and I don't think I've had to take the preamp beyond 12 o clock yet with digital sources.

The input impedance on my power amps is 50k Ohms, so what does the output impedance of my phono stage need to be?

Cheers. :)

[Dave Cawley]

The input impedance on my power amps is 50k Ohms, so what does the output impedance of my phono stage need to be?


This is mostly wrong and confused. I sugest you ask the advice of a good local dealer.

Dave

[Haselsh1]

The Croft Micro Basic 25 preamp with built in valve phono stage is truly stunning when compared to a flat and lifeless passive pre. I have just moved over to a Croft pre/power from a Creek OBH-22 passive and can't understand why I ever bothered with a passive in the first place. My personal opinion would be to sell your passive and buy a Croft. At least that way you have saved on a phono stage and you get a bit back from your pre. I feel an ebay moment arriving...

[HighFidelityGuy]

The input impedance on my power amps is 50k Ohms, so what does the output impedance of my phono stage need to be?


This is mostly wrong and confused. I sugest you ask the advice of a good local dealer.

Dave

Sorry Dave, what am I supposed to be asking them? What the input impedance of my amp is or what phono stage would suit my setup? Cheers.



The Croft Micro Basic 25 preamp with built in valve phono stage is truly stunning when compared to a flat and lifeless passive pre. I have just moved over to a Croft pre/power from a Creek OBH-22 passive and can't understand why I ever bothered with a passive in the first place. My personal opinion would be to sell your passive and buy a Croft. At least that way you have saved on a phono stage and you get a bit back from your pre. I feel an ebay moment arriving...


Does the Croft Micro Basic 25 (or any other Croft preamps) have remote volume and input control and a home theatre bypass input so I can pass the front channel output from my AV amp into it without the preamp affecting the signal level from the AV amp? These are the two most important non sound quality related features to me. The only sub £1000 preamp I could find that had all the features I need is the one I have. THIS ONE (http://www.ciaudio.com/plc1.html) I didn't buy it because it was passive, it was simply the only one I could find. I paid about £570 for it on special offer but it now costs £700.

Cheers.

[Haselsh1]

Unfortunately Croft is about pure Hi-Fi stereo and therefore would not be suitable but I still feel you need to rid yourself of a passive pre. I found out the expensive way as I suspect, you will.

[Dave Cawley]

You need to sit down with a local dealer, explain why you have the system you currently have and why you bought it. What you like and what you don't like. What you want to achieve and how to upgrade in the future.

This would take at least 30 minutes face to face.

You could do it on this forum, but I suspect that it could take 500+ posts to do that. I have lost the plot already as I'm not sure why you have bought what you have and what you actually want and why?

Regards

Dave

[HighFidelityGuy]

Ok, I didn't realise this was going to be so difficult. I'll get in touch with the guy that sold me the preamp, he runs all sorts of very high end setups, with and without turntables so he should be able to help.

It's tricky explaining why I bought the preamp as the home theatre bypass feature I need is not very common and so not many people are familiar with it. I bought my preamp because it was good quality, had all the features I needed and was in my price range. At the time I didn't care if I ended up with a passive or active design as all my current gear and cables were compatible with a passive design, so either would work. At the time I knew I would want to run a turntable in the future but I didn't realise phono stages had such low level outputs, I thought all source gear nowadays had outputs over 2V RMS.

I'm extremely happy with my current setup using digital sources, it sounds fantastic to my ears so I'd obviously rather not change any of the current gear but that's not to say that I would be against trying alternatives that had the features I need.

It seems that the only problem I have is that phono stages don't have a high enough output to work with my passive preamp, so I appear to have the following options:

1. Find a phono stage that has higher output
2. Boost the output of a standard phono stage somehow.
3. Try a standard phono stage and see what happens.
4. Change my preamp to something more suitable for use with a phono stage or one that has a built in phono stage.

It sounds like 1 won't be very easy within my budget, 2 is possible but may not yield good results but may be worth a try. 3 is certainly easy to try and it can't hurt. 4 is the most problematic for me as if I can't find another preamp that has all the features I need I would need to completely re-design my system and buy more gear.

I've purposely avoided mentioning all this extra stuff up until now as I knew it would be difficult to explain and to me it's not relevant, as at this stage I just need to know if there are other ways round the problem other than swapping my one month old preamp for a another one that probably doesn't exist.

I simply can't understand why if an active preamp boosts the output from a phono stage to make the level suitable for poweramps, why is it bad to boost the signal using a seperate preamp between a standard phono stage and my passive preamp? What's the differance other than the fact that the preamp will be in a separate box and maybe that the volume control will be after the preamp rather than before it?

If I had the answer to the above question it would greatly help me to understand how phono stages and preamps interact.

Thanks. :)

[Primalsea]

Hi Dave, TBH I dont agree with what Dave C has said. One of the points of this forum is for people to ask questions and others to answer based on their opinions and experiences. Its then up to you to think about all the variations and look into it a bit further yourself.

If it were me I would get a good grounding of the key technical issues, differing standpoints etc etc and then go to a dealer or a few. Its cynical just to think that all dealers are untrustworthy, many of them are good blokes but at the end of the day they are in business to sell you stuff and although they may solve your problem in one of the best ways possible you cant assume that it will be the best way for your pocket. Not all dealers are like this but you have to keep it in mind until you build a bit of trust with them.

The dealer you mentioned might be happy to loan you a phono amp with a similar output to the ones you are interested in. You can then suck it and see if you get enough volume from your system. Most dealers will lend you their demo gear if you pay a deposit.

[HighFidelityGuy]

I've been discussing diy phono stages with Mike Homar and his WAD clone apparently works well through his passive preamp, so I'm currently looking into the possibility of building one of those. Before I start work on that though I will try and borrow a phono stage in my price range from a local dealer to do some preliminary testing. Based on what I discover from all of the above I'll make a decision on what direction to take.

Thanks to everyone who contributed, I appreciate all your input and I'm going to take it all on board as I move forward with this. I'll make sure to post my findings.

I would still like to know the answer to my question at the end if post #27 though as it will help my understanding of the subject. I hate not knowing the reason why something isn't supposed to work. :)

Thanks. :)

[Mike]

I would still like to know the answer to my question at the end if post #27 though as it will help my understanding of the subject. I hate not knowing the reason why something isn't supposed to work.

This one?


I simply can't understand why if an active preamp boosts the output from a phono stage to make the level suitable for poweramps, why is it bad to boost the signal using a seperate preamp between a standard phono stage and my passive preamp? What's the differance other than the fact that the preamp will be in a separate box and maybe that the volume control will be after the preamp rather than before it?


It probably would work. But it's just adding yet another gain stage into the path that might not be necessary. I think. Much would depend on the phono stage and passive pre being used...

[HighFidelityGuy]

Ok thanks Mike, so basically it would work in some instances but maybe not others. That'll do for me. At least I know what's possible so I can do some testing for myself.

Cheers. :)

[sondale]

Hi - just wondering why no mention of the Music Angel pre-amp - there should not be a problem running a phono stage into that. I do not have any experience of this pre but it must have 'normal' line level inputs.

If you really want to have a 'passive' preamp look for LightSpeed Attenuator; probably one of the finest going - but you have to build it yourself - or buy one from Australia from the (small scale) manufacturer.

You will find quite a few people here who are using one.

Alan

[sondale]

I had been following your links - just noticed the thread on your pre-amp:doh:

[HighFidelityGuy]

Hi Alan,

The Music Angel is a possibility for the future but it will require quite extensive and expensive modification to install the features I need just to make it interchangeable with my passive. The Music Angel is now really just a play thing for me to tinker with and learn about valve equipment. I may use it for something later but for now I need a phono stage that will work with my passive.

Cheers.