Do I need my step-up?

Bryon · 2918

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Offline Bryon

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on: February 07, 2010, 07:22:53 PM
My system, like many others, has too much gain.  For example, my cartridge is low output [.4mv] and I use a step-up [Peerless 4722's] into my Eros but only the first two settings on my FPIII [which feeds Paraglows - then DX4's] are usuable as it gets way too loud.  I'm wondering if it would possible to just take the cart directly into the Eros or if it needs the signal boosted beyond the .4mv?

Anybody have any experience with low ouput carts directly into the Eros?

thanks

Bryon  



Offline Paul Birkeland

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Reply #1 on: February 07, 2010, 07:57:19 PM
You could consider changing the amount of the primary on the 4722 you are using, as you may have it on the higher ratio right now.  Also, you could switch to 15095's to reduce the ratio further. 

Also, how much resistance do you have in the FP-III on the input used with the Eros?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Bryon

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Reply #2 on: February 07, 2010, 08:35:50 PM
Thanks for your input.  I actually have a pair of  the 15095's but I haven't got around to adapting my step-up as they need to be wired differently.

I'm not sure what the input resistance is - I'll have to check. 

What I was primarily interested in was finding out if the Eros required a higher signal than the Zyx would provide or if the end volume was all I have to worry about.

thanks

Bryon



Offline Paul Joppa

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Reply #3 on: February 07, 2010, 09:01:10 PM
Generally Eros wants 2mV, maybe 1.5mV minimum. Below that the tube noise becomes obtrusive. Personally I think it performs best at 3 to 5mV input, which would be a 10:1 stepup - not as much as the 4722; the 15095 at 150:15K would be closer. That will buy you one or two clicks on the FP-III control.

The high sensitivity of the DX4s, plus the relatively high gain of the FP-III, are probably the root of your problem. Without doing the detailed numbers, I'd reduce both Foreplay and Paraglow gain. Foreplay III is easy - check the manual for input sensitivity adjustment. Is the Foreplay Extended?

You can put shorting plugs into one input of the Foreplay and listen; if you hear too much tube rush, or more hum than the Paraglows alone (with shorting plugs in their inputs), then an attenuator at the Paraglow input will help further. Check my "signals and Noise" paper on the Community page if you have the time and patience.

Paul Joppa


Offline Bryon

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Reply #4 on: February 10, 2010, 05:26:00 AM
Hi Paul

Thanks for the suggestions - sorry I took so long to respond but life intervened.
The FPIII is extended.  I have read your signal and noise paper, which I found very informative and intend to put some attenuation on my Paraglows when I have time.  I had thought that eliminating the step-up might be a viable option in the short term but if the Eros wants 3-5mV, trying to feed it .48mV isn't going to be very satisfactory.

thanks again

Bryon