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Attentuators - Use With Fisher Tubes Amps?

ssouci

ssouci

Well-Known Member
I'm intrigued with the idea of using in-line attenuators on the input terminals of my Fisher integrated tube amp (model X-202)

it seems that modern input sources are too "hot" (too high voltage) for older equipment like a tube amp, for example a CD player, DAC box, etc... and that can overload the preamp circuitry

I'm hoping that by using attenuators, it will present the circuitry with a level more in keeping with what it was designed for, hopefully resulting in general sonic benefits, plus making the volume control sensitivity more usable (ie., increase the range of adjustment before the sound becomes too loud)

however, my research into attentuators shows a real mixed bag of results: some posters claiming great results and no degradation of sound with lots of benefits (better overall sound, less harshness with CDs, better volume control modulation), while others say it killed their high frequencies and sparkle, and to definitely avoid using them... very conflicting views EG: https://hifiwigwam.com/forum/topic/120698-rca-attenuators-influence-on-sound-quality/page/3/

I can buy a pair of in-line attenuators with RCA connections for approx. $30-60, which is not outrageous considering all the (potential) benefits... EG: http://www.hlabs.com/products/attenuators/

NOTE: I run an Oppo BDP-83SE disc player with output voltage of 2.2V(?), connected via the Aux input

QUESTIONS:
Q1. what level of attenuation should I use with an X-202?
Q2. will using an attenuator degrade the sound of my amp... how and by how much?
Q3. if it will degrade, would using the lowest worthwhile level of attenuation help?
Q4. what brand of attentuator can users recommended? eg. Goldenjack, Harrison, Rothwell

(I'm located in Canada, so looking for most cost-effective brand shipped there)

any advice hugely appreciated!
 
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No need for a fancy external attenuator and another box on the shelf. The major problem will typically be a CD player. Just add a pair of resistors in each channel to make a voltage divider. These can be added in either the receiver/amplifier directly on the input jack or in the source unit at the output jack.
 
A CD player will typically have a low impedance output, on the order of 10K. My Harman Kardon CD players have a 5K pot feeding the variable output. I don't know if this is linear or audio taper, but I typically have it set at about 50% of rotation. I'd start with 2 10K resistors in series and take the output at the point between them. Then experiment with different values.

If this proves to be too low for the tube amplifier input, then move up to a pair of 47K. The low impedance from the CD player will still drive it.
 
fred soop said:
A CD player will typically have a low impedance output, on the order of 10K. My Harman Kardon CD players have a 5K pot feeding the variable output. I don't know if this is linear or audio taper, but I typically have it set at about 50% of rotation. I'd start with 2 10K resistors in series and take the output at the point between them. Then experiment with different values.

If this proves to be too low for the tube amplifier input, then move up to a pair of 47K. The low impedance from the CD player will still drive it.
Click to expand...
 
I'm also interested in this topic due to the fact that I'm having the same problems with my Fisher 202T, 400, and TA-600. The 202T (the worst offender) has input adjustments for the phono, multiplexer, and tape. I wonder if the mpx or tape inputs could be used if I turned them down low enough (if it will even go low enough). Anyway, I'm interested in a fix for the 202T's AUX inputs also. Looking forward to seeing what I can do. Thanks.

Larry D.
 
fred soop said:
No need for a fancy external attenuator and another box on the shelf. The major problem will typically be a CD player. Just add a pair of resistors in each channel to make a voltage divider. These can be added in either the receiver/amplifier directly on the input jack or in the source unit at the output jack.
Click to expand...
Fred:

do you have a simple sketch for how the resistors would be wired (or a link to somewhere on the web)?

also, do you think that the type/brand of resistors used will have any effect on the SQ? (seems that some the RCA inline-style units sold use tiny SMD resistors due to size constraints, which some have suggested don't sound the best)
 
whoaru99 said:
@ssouci

If you want less output from the player just reduce it using the remote's volume adjustment.
Click to expand...

to me, it seems that yes, using the remote ("volume" setting) results in lower sound level, but I seem to lose a lot of richness & vibrancy in the sound quality... I think it's because that is a digital reduction method, not an analog (???)... I do use that to lower temporarily lower the sound level in an emergency though
 
I think that has 32-bit DAC with the integral volume control same number of bits. Personally, at 32 bits volume control, I question if the effect is more preconception than reality but that's for you to decide.
 
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ssouci said:
Fred:

do you have a simple sketch for how the resistors would be wired (or a link to somewhere on the web)?

also, do you think that the type/brand of resistors used will have any effect on the SQ? (seems that some the RCA inline-style units sold use tiny SMD resistors due to size constraints, which some have suggested don't sound the best)
Click to expand...

No simple sketches. My pictures get posted as links to Flickr and total number of photos is limited, so I don't want to use limited space for simple sketches. That said, the circuit is 2 resistors in series. The top of the first resistor is connected to the input from the high output source. The bottom of the second resistor is connected to ground (be careful of ground loops). The "new" output is connected to the joint between the resistors.

I would not use SMT parts (actually for anything I'm working on) but carbon film or metal film will be sufficient. The source with the high signal will be relatively unaffected by the slight additional noise from carbon film resistors, especially if the values can be kept low (10K or close).
 
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