Bottlehead Forum

General Category => Technical topics => Topic started by: docbob52 on October 25, 2014, 05:03:56 AM

Title: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: docbob52 on October 25, 2014, 05:03:56 AM: Any recommendations for a tutorial that is EASY to understand on selecting and matching a step up transformer to a low output MC phono cartridge?
Math is not my strong point.
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Grainger49 on October 25, 2014, 05:29:00 AM: Do a search for SUT authored by Paul Joppa in the Phono folder. This was discussed on, I think, this forum a while back. Paul posted a number of formulas that are needed to match the source (cartridge) impedance to the transformer input impedance. You also need to work with the 47k standard phono input impedance and the turns ratio (step up ratio) of the transformer.

I'm still foggy on all of it but there is also a reflected impedance from the cartridge to the output of the SUT. Paul did a good job of presenting it.
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: fullheadofnothing on October 25, 2014, 07:46:21 AM: This is a really good introduction, with a nice qualitative/quantitative balance.

http://www.vinylengine.com/step-ups-and-mc-cartridges.shtml (http://www.vinylengine.com/step-ups-and-mc-cartridges.shtml)
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Tubejack on October 25, 2014, 05:33:52 PM: Also a good ref here, with useful links.

http://www.theanalogdept.com/sut.htm (http://www.theanalogdept.com/sut.htm)
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: roscoe primrose on October 27, 2014, 07:51:56 AM: more links ;)

http://www.intactaudio.com/forum/viewtopic.php?t=752

http://www.mennovanderveen.nl/mc10/mc-10-en.pdf

Roscoe
Title: step up transformer loading
Post by: keithp on October 27, 2014, 12:37:25 PM: I want to get a step up transformer to go with the new Eros I have on order. The transformer will replace a 30 year old solid state head amplifier and will be used with a Shelter 501 Mk II. The specs say the cartridge has an output of .4 to .5 mv and resistance of 12 ohms. How do I tell what winding ratio to get, 1:10, 1:20 or 1:40? If it is between two values,is it better to go up or down? Are there any preferred brands under $500 per pair or do I have to spend a $1,000 to get a good one?
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Paul Joppa on October 27, 2014, 05:28:24 PM: A 1:10 stepup ratio is plenty, that gives you a nominal 4-5mV. If you have plenty of gain in the rest of the system, you might try it without a stepup - the result will be have more immediacy, though it may have too much tube rush noise. Worth a try anyhow.

Josh "fullheadofnothing" and Dan "DocB" are more experienced, hopefully they will post.
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Tubejack on October 28, 2014, 05:18:21 AM: FWIW, I have a Shelter 501 MKII, with modified EROS, VPI SS TT w/JMW 10" Classic Sig arm, and I was never totally happy with any of the SUT's I tried or built - S&B TX103 (Bent Audio), Lundahl LL1931, Cinemag 1131, and Altec 4722. Maybe I couldn't load it properly, maybe it was the IC's I was using, maybe it was the VTA or some arm damping thing I couldn't get right, I just couldn't seem to find a "sounds right to me" combination for the 501. (Although I did find some satisfaction with the Bent's and a DL103R). I finally tried an active MC preamp ahead of the EROS, integrated easily, and have been happy ever since. Sold all the SUT's and the DL103R, and kept the 501. The journey through the above was about 4 years. (Built my EROS in 2009, and it has never been out of my vinyl front end. It replaced a modified C4S'd Seduction.)

My ears and my experience only. I can bet there was an implementation combination of SUT's I tried and loading that would have given great results with the 501, but once I had tried an active pre, I stopped looking ......
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Paul Joppa on October 28, 2014, 11:35:25 AM: Tubejack, did you ever try the Shelter direct into the Eros, with no stepup of any sort?
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Tubejack on October 30, 2014, 11:56:54 AM: Hi Paul -

Yes, but to be honest, I don't recall the sonic impression. I probably just "aSSumed" that a MC by, definition , well, just NEEDS some kind of voltage boost ... (Hate it when I do that ...)

I found that the 501 does work well into a higher Z than calculated, so I don't expect 47K would be an issue. I will give it a try. My current line stage is a unity gain device (to drive long IC's to 300B SETs), which may not give me enough oomph in the vinyl chain ....

rgds/jack
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Paul Joppa on October 30, 2014, 12:31:50 PM: Thanks, Tubejack. We have proven to our own satisfaction that a 0.1 or 0.2mV cartridge is too noisy without a stepup, but I think 0.5mV is on the edge - I'd like to get any impressions I can so we have a better idea when to recommend trying it.

We've done a lot of experimenting with tube stepups, without a real success yet. I haven't given up but the guys are burned out now so I'll study up the theory for a year or two before trying it again ...
Title: Re: Need tutorial for matching a SUT to a low output moving coil cartridge
Post by: Doc B. on October 30, 2014, 12:42:54 PM: Well, I wouldn't say without success. It sounds incredible. But the noise floor is a little too high.