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MartinT
24-06-2009, 19:41
Ok, I've read so much about the two different methods of running a low output MC cartridge. Some advocate a SUT as being the best impedance match to a high level phono preamp, others prefer a preamp with MC capability.

I'm running an AT33PTG with Underwood modded PS Audio GCPH set to high gain. Although the GCPH is pretty quiet, I can just hear noise and hum when the volume is set to my normal listening level. Now I'm beginning to wonder what a SUT would do for my system, with the GCPH set to low gain.

What do the assembled think? Should I try a SUT or am I wasting my time? If so, which SUT?

Marco
24-06-2009, 20:37
Hi Martin,

It's a tricky one. The trouble with SUTs is that they tend only to work best when they've been designed in unison with a partnering cartridge, so this usually means that the cartridge and transformer will come from the same manufacturer.

It's different of course if you're into D.I.Y and have the facility to build your own phono stage and SUT to match your cartridge of choice, but commercially this isn't such an easy option.

To answer your question, the only SUT I'd use with your AT33PTG is this:

http://cgi.ebay.com/Audio-Technica-AT5000T-MC-Step-Up-Transformer-45th-ANV_W0QQitemZ390056558787QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item5ad12ec0c3&_trksid=p4634.c0.m14.l1262&_trkparms=%7C301%3A0%7C293%3A1%7C294%3A30

...and it's not exactly a cost-effective proposition!

So to answer your question, in your situation, I think you're largely wasting your time, and I'd stick with your current PS Audio phono stage. Also, SUTs will not necessarily make things any quieter, in fact often they can generate hum.

If you want to get more from your cartridge then you could at some point consider changing/upgrading your phono stage, perhaps by looking at an all-valve design. There are some cracking ones around at the moment :)

Marco.

The Grand Wazoo
24-06-2009, 20:54
Martin,

As Marco says, this is tricky. (I knew he'd beat me to answer this!)
I certainly wouldn't go chucking any money at this yet.

Have you checked that all your earth connections are good? - and I mean absolutely impeccable .....clean & tight, right through the system.

Your phono stage is not exactly a slouch.

If I were you, I'd try to borrow a half decent SUT to test your theory.

DSJR
24-06-2009, 20:54
Once again, I can't be so cut and dried about it. I'm curently using some Sony versions of the Ortofon T5's, regarded as give-aways at the time. Whatever a dearer tranny may do, I'm getting more music out of my LP's (with a Stilton OC9) than I've done in years. I'm keen to try the Sowter transformers one day with the OFC option (around £130 the pair) as silly bits of male jewellery intended for the status concious far eastern market (my SUT costs ten times yours so must be better) have no relevance these days...

In the meantime and bearing in mind my thread regarding occasional distortion due to bad LP's and possible arm-bearing chatter (now fixed I think), I'm being lent an AT630 transformer which gives lower gain and was well liked at the time.

As some SUT's are fairly cheap, why not try a pair and see for yourself. At least you have a decent active reference...

Marco
24-06-2009, 21:11
Guys, I think trying an SUT is perfectly good advice for Martin, just to see what it does.

However, I'm looking at the bigger picture (as I always do), and so therefore, if Martin decides to go down the SUT route, he has to have a viable choice to make which will genuinely improve the performance of his cartridge compared to what he's getting at the moment from his PS Audio unit.

I don't think any of the suggestions so far for him to try, SUT-wise, represent an upgrade on the gear he's using at the moment, so the question is what *real* choices does he actually have when it comes to an SUT that will ideally match his AT33PTG and offer him a genuine upgrade?

In my view, the AT-5000T SUT I linked to on Ebay, or a completely different phono stage, are the only options that fit the bill. Personally, unless Martin wants to splash some serious cash, I think he should leave well alone and continue enjoying the sounds he's getting at the moment, which by all accounts are pretty special :)

Tinkering for the sake of tinkering rarely pays dividends.

Marco.

The Grand Wazoo
24-06-2009, 21:20
Tinkering for the sake of tinkering rarely pays dividends.


I thought what I suggested wouldn't involve any outlay or risk.

Checking your earth connections is not exactly tinkering in the sense that you imply.
Borrowing a SUT will throw more light on the problem/solution.

As I said, I certainly wouldn't throw any cash at it just yet.

Marco
24-06-2009, 21:22
Yep, I wasn't referring to your post Chris :)

Marco.

The Grand Wazoo
24-06-2009, 21:35
Yep, I wasn't referring to your post Chris :)

Marco.

Hahaha,
Sorry the plural 'Guys' caught me out for a bit there!!!!

You will learn to use grammar correctly, Marco, my boy!

Marco
24-06-2009, 21:46
I do already, matey. "Guys" is simply a generic term I often use for addressing the forum as a whole. Observe how I sometimes use this nomenclature when making announcements on the noticeboard for the benefit of everyone. It's the same here. Sometimes I also use the word "People" in the same way :)

Marco.

The Grand Wazoo
24-06-2009, 22:07
I do already, matey. "Guys" is simply a generic term I often use for addressing the forum as a whole. Observe how I sometimes use this nomenclature when making announcements on the noticeboard for the benefit of everyone. It's the same here. Sometimes I also use the word "People" in the same way :)

Marco.

I don't care, you're still going to see the Headmaster.



Martin,
Have you tried setting your phono stage to MM level settings & turning it up? Is there too much noise then?

MartinT
24-06-2009, 22:34
Thanks all for your suggestions.

The GCPH phono amp incorporates two gainclone modules (with passive RIAA in between) and adjustable gain for each stage (rear switches for the first stage, front panel knob for the second stage). As you can imagine, there are enough variables to drive you mad!

I have tried lower gains while turning my main preamp up, but the overall gain keeps noise at listening volumes pretty much the same, as does relative adjustment of each gain stage. I have moved the GCPH around but the hum doesn't change. Removing the TT earth increases hum dramatically. I surmise that the remaining noise & hum are just caused by the high gain being asked of the GCPH. I should stress that this can only just be heard while not playing a disc - it is not audible at all whist listening to music.

I do agree with the suggestion that I should try a SUT and see. I am certainly not going to buy the delicious looking AT-5000 unit, but I am willing to experiment with something highly rated that stands a chance of allowing me to compare sound quality while remaining inexpensive.

Reviews and forum comments have drawn me to the CineMag transformers, with Bob's unit the best looking implementation:

http://www.bobsdevices.com/cinemag.htm

I've discussed the AT33PTG's compatibility with him and he reckons it'll be nigh-on perfect on the 16x gain setting. The price is reasonable and I could always eBay it if it doesn't work out. Should I take the plunge for the sake of experiment? I'm gravitating towards firing an order off.

Marco
24-06-2009, 22:47
Why not, Martin - what's the worst that could happen? :)

Marco.

Barry
24-06-2009, 23:06
Hi Guys :eyebrows:,

From what I have read on the web, it would seem that AT33PTG users are loading their cartridges with anything from 20 Ohm (!) to 150 Ohm, with 100 Ohm being preferred. All Audio Technica say is > 20 Ohms

The internal (coil) resistance is 17 Ohm and the cartridge has an output of 0.5mV (at 5cm/sec). So if you are going to use a SUT, then the rule of thumb is to choose a transformer that will present a load impedance 5 -10 x the cartridge's internal resistance. If you choose a transformer with a 20:1 turns ratio, then the 47KOhm impedance of the preamplifier will be transformed to 117.5Ohm or ~7 x the cartidge impedance. A 20:1 transformer will then produce a 10mV signal for the preamp.

Transformers are lower noise devices than pre-preamps, but to work at their best one should choose a design that is designed for a specific source impedance (in this case 17Ohm). Very few transformer manufacturers offer this information. In fact the German Haufe and the British Stevens and Billingham are the only companies I know that provide this information.

So in view of the above I would you suggest you keep to you step-up amp and carefully check, as Chris has suggested, the earthing arrangements.

Trust this is of help
Barry

The Grand Wazoo
24-06-2009, 23:06
Martin,
The Cinemags are good transformers - quite sweet sounding.

Bob's version has a couple of switches, & if you buy them, I'd ask for instructions as to how they can be bypassed once you've found the setting that suits best for your gear. It shouldn't be too tricky & you can't beat a straight signal with no switches when you're dealing with such a tiny & delicate signal. These things are usually easy to reverse.

Barry
24-06-2009, 23:14
Between reading your initial query and posting my reply, I see that you are thinking of using CineMag transformers with a 16:1 turns ratio. These will transform the 47KOhm preamp impedance to 183.6 Ohm (or 10.8 x the coil resistance), and will boost the output to 8mV.

I can't see any problems here, so if you are willing to give it a go - why not?

Barry

NRG
25-06-2009, 08:14
I highly recommend Sowter. Not cheap but then quality never is ;) and you would need to mount them yourself but their performance is outstanding and Sowter can wind them to your exact needs if required...

http://www.sowter.co.uk/phono-cartridge-transformers.php

Chris
25-06-2009, 10:14
I agree with Marco - cartridges and Suts should be matched pairs . My DIY haufe based SUT walked all over my Audio Technica AT650 when used with my 103Pro but now I have changed to an Escoed Troika the AT sounds better in spite of the fact that in theory the Haufe should be fine. I feel one thing is the electrical compatibility and another is the sound. If you can audition the alternatives or use other people“s experience with the same combination, great, but if not, as is my case, it“s difficult so I“m going to opt for the Hagerman Piccolo active head amp kit which offers all sorts of flexible settings and seems to be comparable to the Cinemags, sound-wise. In the days of the Troika, SUTs were frowned upon so no-one has much experience with the Troika- hence my decision. Fingers crossed.

MartinT
25-06-2009, 12:31
Thanks everyone. I've had further discussions with 'Bob' and his CineMag unit is ideally matched to the AT33PTG with gain and impedance loading all perfect for the PS Audio to receive a healthy 7mV into 47k and the AT loaded to 180 Ohms (thanks Barry for your confirmation). This on the 16x setting.

I have decided to go ahead and order it. I will conduct some comparisons and report back in Strokes of Genius if people are interested. I'm quite intrigued to hear the results myself.

DSJR
25-06-2009, 17:07
A very kind gent has loaned me his AT630 SUT for a while. I've yet to listen, but its lower gain should be a great help with the Croft.

I just wanted to express an opinion, not about good ss stages vs good sut's as such, but a comment on the ridiculously priced (to me) AT sut referred to earlier in this thread... I hope the likes of Marco would agree that much "top end" audio is aimed at people to whom a few grand isn't a huge problem. These products, in my opinion, don't offer a huge amount over more basic ones and in the case of solid state products, don't cost much these days to make. What DOES cost is the deluxe casework, the deluxe packaging (in the case of cartridges, the packaging often costs more than the item itself at factory costs [first hand experience here, this bit's not opinion]) and most priceless of all, the status given to the owner - very important I understand in the far east.

having thought about it for a good while, I will happily accept that huge special transformers used in power amps cost a bit, especially when the chrome end caps are fitted (;)) but a little sut for mc cartridges? The fact is I suspect, is that it has to sell for this amount to get a cachet in Hong Kong and other similar places. A phono stage I know of which sells for £2500 here could quite profitably sell for £900 or so in the UK, but is priced where it is because most are sold in the far east. This item is up against units costing £12,500 and out-performs them apparently, but I wouldn't be surprised that the people buying the dearer model wouldn't even look at the cheaper, superior product - a bit like LP12 owners being vitriolic about SL1200's despite never having heard them.

A bit muddled and posts have moved on now, but it's a good idea to try alternatives while keeping the unit you know and love, despite a query regarding one aspect...

P.S. With an output of .5mv @ 5cm/s, wouldn't a gain of 10:1 be better? SS preamps can have funny overload problems and surface ticks and spits can sometimes cause momentary ringing in phono circuits (apparently even in good ones). Just a thought...

MartinT
07-07-2009, 20:18
Bob's CineMag SUT arrives tomorrow. I'll report on my findings once I've had a good play with it.

Dave Cawley
07-07-2009, 20:28
The GCPH I tested did hum and had a shed load of additional problems. SUT's can be very microphonic too. I know I'm biased but the A.N.T. phono stage deserved the 5 star award it got. I can offer a sale or return if anyone is interested.

Dave

MartinT
07-07-2009, 20:35
Yes, there is very low level hum but I think the Underwood mods have lessened it compared with stock. I must say that sound quality is superb, better than my old EAR 834P and that was no slouch. What kind of problems did you measure in the stock item?

By the way, I thought long and hard about the A.N.T. but I couldn't easily hear one so went with my gut instinct that the GCPH would suit.

Mike
07-07-2009, 20:54
To answer your question, the only SUT I'd use with your AT33PTG is this:

http://cgi.ebay.com/Audio-Technica-AT5000T-MC-Step-Up-Transformer-45th-ANV_W0QQitemZ390056558787QQcmdZViewItemQQptZLH_Def aultDomain_0?hash=item5ad12ec0c3&_trksid=p4634.c0.m14.l1262&_trkparms=%7C301%3A0%7C293%3A1%7C294%3A30

...and it's not exactly a cost-effective proposition!

T'aint what I'm using! ;)

MartinT
07-07-2009, 21:13
What are you using, Mike?

DSJR
07-07-2009, 21:23
Well, I'm using a loaned AT630 SUT which can't be any good 'cos it doesn't have foo wiring and nor does it have an expensive box and it "only" sold for £45 at the time. It inverts the phase it seems and this is audible, but it doesn't hum at all and the audible bass range is very good indeed. Of course, it could be said that my system doesn't have the definition of a "proper" system, but it makes good music so I'm happy...

I think Linn did a very fair active MC stage on their LK1 and Kairn preamps, limited mainly by the line stage the signal passed through IMO. Minus 80db s/n is pretty darned good for a domestic ss MC stage IMO and around 15 - 20db better than the equivalent Naim ones at the time I think.

I wonder how good or bad the OCC versions of the Sowter transformers are?

Dave Cawley
07-07-2009, 21:46
In any system, there should be no hum at all. Not even a trace of hum should ever be heard under any circumstances!

The A.N.T. and Whest PSR.30 achieve this, as does my own AT630 that cost me under £30!!

Regards

Dave

DSJR
07-07-2009, 21:49
I missed on at the weekend which went for £37 IIRC. With the phasing right I think it's ok.

I dare not ask really, but does it compare at all with modern expensive SUT's (assuming that today the 630 would be around £150 and the 650 around £200 I suspect).

RobHolt
07-07-2009, 22:03
I missed on at the weekend which went for £37 IIRC. With the phasing right I think it's ok.

I dare not ask really, but does it compare at all with modern expensive SUT's (assuming that today the 630 would be around £150 and the 650 around £200 I suspect).

It does.

MC transformers needn't cost silly money. Look at what is actually required and what that costs to produce.

The Sowters go for about £100 each. You can put them in a bling box if you like and charge £2000 - I won't tell ;)

Mike
07-07-2009, 22:30
What are you using, Mike?

These: http://wduk.worldomain.net/acatalog/info_WDMCT.html :)

Will
08-07-2009, 00:36
Cinemag 1:10 1:20 1:38
I suppose the cheap price puts audio foools off.
About $100.00 a pair and with a valve phono stage they are amazing value.
103 to SPU

NRG
08-07-2009, 07:24
It does.

MC transformers needn't cost silly money. Look at what is actually required and what that costs to produce.

The Sowters go for about £100 each. You can put them in a bling box if you like and charge £2000 - I won't tell ;)


The Sowters are approx £115 a pair, depending on which type you go for.

http://www.sowter.co.uk/phono-cartridge-transformers.php

Chris
08-07-2009, 08:20
My Haufe transformers - a great match with my 103Pro - cost me around 40,00 euros each which with postage from Germany meant around say 100 euros. A nice aluminium box and some terminals = 120 euros or thereabouts.

Barry
08-07-2009, 22:09
My Haufe transformers - a great match with my 103Pro - cost me around 40,00 euros each which with postage from Germany meant around say 100 euros. A nice aluminium box and some terminals = 120 euros or thereabouts.

Chris,

Would you be willing to sell the Haufe transformers alone, separate from the cartridge? PM me if you are interested.

Thanks

MartinT
15-07-2009, 07:26
Well, the CineMag unit arrived last week and I've devoted a lot of time playing with it and all the various permutations of transformer gain, phono preamp gain and loading, with and without transformer. It's a beautifully built unit and a true object of desire. One thing that became quickly apparent is that the phono cable from trannie to phono preamp is critical in terms of shielding and length. Even a well shielded 1m QED Qunex picked up hum and I had to buy a 1ft length with careful routing before I got hum under control.

The best sound I obtained from the trannie combo was gain x10, phono amp gain 48dB and loading 47k. It sounds liquid in the midrange but somehow not as fast as I am used to. Tellingly, scratches are reproduced with a clack rather than a short click. I suspect that some time smearing is going on here, but I have been unable to find a better combination of settings. If I didn't know the sound of the phono pre used exclusively, I would be happy with the overall sound but concerned over slightly elevated surface noise and the handling of scratches. Hum levels were just acceptable.

The best sound I obtained using the GCPH exclusively is better than I had originally managed. I set it up for the AT33PTG with gain 54dB and loading 500. Front panel gain was set to 3/4 in both cases. Hum is now well suppressed. The sound is fast, open, highly detailed with a wide soundstage.

So the result is Trannie 0, without Trannie 1. I'm not at all bothered about the outlay and enjoyed conducting the experiment. I'm also pleased in that it led me to better settings for the GCPH, eliminating hum at normal volumes. I guess I'm a direct phono preamp sort of guy :)

NRG
15-07-2009, 07:40
With the o/p impedance of the PTG at 17 Ohm I think you need to lower your loading to 100~150R... 470/500 is too high IMHO and would lead to the symptoms you described.

Marco
15-07-2009, 08:16
Hi Martin,

Unfortunately, this is the result I predicted.

Hey at least you tried it, so if nothing else you're a little bit wiser now than you were before :)

Correct me if I'm wrong here, but are you saying that the Cinemag SUT has got variable gain and loading or your phono stage, or both?

If you're referring to the Cinemag then, in my experience when it comes to SUTs (as I've mentioned before) the only ones that work properly are ones with fixed gain and loading, where the transformers have been selected to specifically match a particular cartridge, like for example the A23 and the DL-103, or Denons own SUTs, and thus where they been developed together.

There is also the issue of matching the relative 'sonic signatures' of SUTs and cartridges, just as is done elsewhere in a system with other components. As usual, it's all about synergy.

Whenever I've tried variable SUTs the results have never been great, and I experienced pretty much what you're reported, probably because you can never *truly* get an optimised match. Often, the optimal settings are out with the range of the variable options.

Therefore, I wouldn't be tempted to 'close the book', so to speak, on SUTs, as at some point in the future if you obtain a cartridge and SUT that have been designed together from the ground up, you may get different results.

The bottom line is you're happy with the results you're getting in your system at the moment, and that's all that really matters :cool:

Marco.

P.S I agree with Neal regarding loading values.

MartinT
15-07-2009, 08:43
With the o/p impedance of the PTG at 17 Ohm I think you need to lower your loading to 100~150R... 470/500 is too high IMHO and would lead to the symptoms you described.

Thanks Neal, I will try the preamp set to 100R loading, but of course I have no way of adjusting the trannie's loading which remains at 470R. So this is an experiment for the GCPH on its own.

MartinT
15-07-2009, 08:48
Correct me if I'm wrong here, but are you saying that the Cinemag SUT has got variable gain and loading or your phono stage, or both?

The Cinemag has x10 and x16 gain. I found the x10 setting to sound superior. There is no variable loading, it's fixed at 470R.


Therefore, I wouldn't be tempted to 'close the book', so to speak, on SUTs, as at some point in the future if you obtain a cartridge and SUT that have been designed together from the ground up, you may get different results.

Absolutely not, Marco, I'm always of an open mind as I learned the lesson years ago that you can easily come around to a component you previously disliked, when it's placed in a more synergistic system*. I intend to keep the SUT for possible future use.

*There are exceptions - I'm never ever going to like Linn Kans for as long as I'm alive.

Dave Cawley
15-07-2009, 08:51
You need to understand transformers to get the impedances right! And you need to understand earthing to avoid the almost inevitable ground loop! :kiss:

Also Cinemag do two transformers, one far more appropriate than the other.

The A23 is designed properly; but Martin, why persist with high speed op-amps and shed loads of negative feedback when you could use a valve like FET with little feedback and passive equalisation?

Regards

:bag:

Dave

Marco
15-07-2009, 09:17
There is no variable loading, it's fixed at 470R.


Therein lays your problem, Martin. That's way too high for an AT33PTG. Like Neil says, you're looking for something in the region of 100-150R.

The other thing is; I suspect that as long as you own solid-state amps you're unlikely to get the full benefits of an SUT.

Some things just 'go together', like biscuits & cheese - and SUTs and valves are a case in point. Not necessarily, like RD says, because you're trying to solve a problem with another problem, but simply because the sum of the parts is more musically desirable and just better overall. In effect, their respective 'flavours' compliment each other - but in the right way.

The fact is, all components are coloured or 'flavoured' to some degree. Therefore, as well as it being a matter of choosing your compromises in hi-fi, it's also a matter of choosing your preferred coloration (or 'flavour'): which components to your ears has the least (or most preferable), and which is ultimately, in your opinion, more faithful to the music. That's why there are no absolutes when it comes to SUTs vs. active MC stages, or for that matter anything in hi-fi! :)

As you know, I've got both an SUT (A23) and an active MC head amp (Denon HA 500), both optimised for the DL-103, and after extensive listening and comparing, there is no doubt that the A23 produces the more musical results. The HA500 is very, very good, but is definitely more 'hi-fi-like' in its musical presentation, whereas the A23 simply gets to the 'heart & soul' of the music and boogies. However, if the HA500 were used with a solid-state MM phono stage, the results might be different. It's that synergy thing again.

Why not, for a laugh, dig out your old Croft preamp, connect it to your system, and try the Cinemag/AT33PTG in conjunction with the Croft's valve MM stage?

It still won't be 100% right because of the high loading value, but it would be interesting to see what results you get in comparison to what you're using now. I, for one, would be very interested to know what happens. If nothing else, it's just another learning experience :cool:

Marco.

MartinT
15-07-2009, 11:08
but Martin, why persist with high speed op-amps and shed loads of negative feedback when you could use a valve like FET with little feedback and passive equalisation?

Dave, it was really a question of circumstance that allowed me to hear the GCPH in action and subsequently order the Underwood modded version. I did look at the A.N.T. brochures you gave me and my interest was piqued but I never got around to talking to you further about it.

To answer your question, and knowing that you dislike it, the GCPH makes fine music with both my DL-160 and the AT33PTG currently in use. I have never heard better LP replay in my system, and that is what counts.

HOWEVER, I would like to give the appropriate A.N.T. model a try as it represents an unexplored avenue and I'm happy to move equipment on to fund new components. Would a loan be on the cards?

Dave Cawley
15-07-2009, 11:40
the GCPH makes fine music with both my DL-160 and the AT33PTG currently in use. I have never heard better LP replay in my system, and that is what counts.

OK, no problem, but why did you order the transformer? And which one?

Regards

Dave

Marco
15-07-2009, 11:44
Why not, for a laugh, dig out your old Croft preamp, connect it to your system, and try the Cinemag/AT33PTG in conjunction with the Croft's valve MM stage?


Any thoughts on this, Martin? I'd love to know what would happen :)

Out of curiosity, when was the last time you listened to the Croft?

Marco.

MartinT
15-07-2009, 11:54
OK, no problem, but why did you order the transformer? And which one?

The CineMags are type 3440-A.

I ordered the SUT so that I could experiment with it, to see if it would give me even better sound quality by reducing the GCPH's overall gain.

MartinT
15-07-2009, 11:57
Any thoughts on this, Martin? I'd love to know what would happen :)

Out of curiosity, when was the last time you listened to the Croft?

Marco.

I am thinking about it. I haven't listened to the Croft SIP in many years, not even sure if it will still fire up ok. I do remember it having a fine MM phono stage.

I did more recently fire up the Croft Series 4S power amp and that has a dead channel. Haven't got time for it really and should sell it as a project to a Croft enthusiast. Too much equipment!

Marco
15-07-2009, 12:16
I am thinking about it. I haven't listened to the Croft SIP in many years, not even sure if it will still fire up ok. I do remember it having a fine MM phono stage.


Please do it and report back. I think you'd find the results very interesting indeed ;)

Overall, it'll probably be worse than your current set-up (because of the loading), but it should give you an inkling of the potential of high quality valve MM stages used with SUTs, and perhaps whet your appetite enough to explore this avenue further in future...

As an aside, I reckon a Puresound P10 (with the right SUT) would work fab in your system!

Marco.

NRG
15-07-2009, 12:30
The CineMags are type 3440-A.

I ordered the SUT so that I could experiment with it, to see if it would give me even better sound quality by reducing the GCPH's overall gain.

The 3440A looks more suited to the DL103 with is higher o/p impedance of 40R.

http://cinemag.biz/mic_input/CMQEE-3440A-Moving-Coil.pdf

The reflected ratio your cart is seeing at 1:10 is 47000 / (10*10) = 470R

At 1:16 it will be 47000 / (16*16) = 184R (approx)

This is closer to what the cart needs but the gain maybe too high now for the phono input.

What you need to do IMHO is add a resistor in the R1 position as indicated in the pdf link above.

A 15K res in R1 position will be in parallel with the 47K of the phono preamp bringing the total R down to approx 11.4K...

At 1:10 the cart will see a load of 114R, just in the ball park....or for R1 you could use an 18K resistor bringing the combined R down to 13K meaning a reflected load of 130R....

Fun things SUT's.... ;)

jonners
15-07-2009, 12:37
I was about to post something very similar to the above but Neal beat me to it. You really can't write off these transformers until you have sorted the impedances - as shown in Neal's link.

MartinT
15-07-2009, 12:40
Many thanks, Neal. More experimentation required. I shall order some high quality resistors.

Marco
15-07-2009, 12:50
Excellent stuff, chaps - that's why we have 'techies' on this forum, too! :eyebrows:

Whatever you do though, when you think the SUT has been optimised, try it with the Croft. I'm determined for you to hear what the results are through a valve MM stage! ;)

Marco.

MartinT
15-07-2009, 13:59
I forgot to mention, there was another reason why I plumped for the GCPH: it has balanced outputs and I like my entire system to be balanced as I find it preferable to single-ended.

So what preamps out there are recommended and have balanced outputs?

Marco
15-07-2009, 14:16
Och, just glue some on to the Croft! What's the worst that could happen? :lol:


Marco.