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Old 23rd April 2007, 07:41 AM   #1
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Default 10k attenuator for AP1.7 output?

Hey all,

I am in the process of building my Aleph P1.7 clone. Currently I have a 10k step attenuator on hand (ladder type). I will be using a A30 as power amp, which has 47k input impedance. If I use the step attenuator at the output, as configured in the service manual, would a damping factor of 4.7 be enough?

Thank you,
Peter
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Old 24th April 2007, 12:17 AM   #2
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any suggestions?

Thanks,
Peter
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Old 24th April 2007, 11:04 PM   #3
flg is offline flg  United States
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Default Re: 10k attenuator for AP1.7 output?

Quote:
Originally posted by peterpan188
If I use the step attenuator at the output, as configured in the service manual, would a damping factor of 4.7 be enough?
Just What do you mean regarding "Damping factor" Typicaly, I'm used to that term being used as the ratio of output to souce impedance, or whatever, ussually, speaker Z/Output impeadance...

Lately, I have dicected my Aleph P1.7-BOSOZ-BZLS Variant. I too wanted a control for volume, but mostly an officially done Finished container with good interconnects and the best components and all because it is a very versatile unit of the Zen family. Balanced-Single Ended-Single Ended- Balancened, high gain low gain, Ect. I'm planing on developing the Lightspeed Attenuator (see thread elsewhere) into the input section. That would be some matched LDRs on each side of the diff amp, 2 pair per channel.
The output does seem to be the more popular choice however
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Old 25th April 2007, 01:00 AM   #4
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I built a finished "switchblade" version much like what flg is mentioning that allows switching of all possible configurations from front panel knobs. Very handy indeed.

To answer Peter's question, I have a 10K stepped attenuator on the outputs of my pre, and it works very nicely with my Aleph-X, which also has a round 47K input impedance. Nelson says a 10:1 ratio or greater is optimal, though.
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Old 25th April 2007, 01:41 AM   #5
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Quote:
I'm planing on developing the Lightspeed Attenuator (see thread elsewhere) into the input section. That would be some matched LDRs on each side of the diff amp, 2 pair per channel.
I did a lot of listening tests on my BOSOZ--and I found attenuating the input made things sound, I don't know--lifeless?

I do tend to listen at low levels. If you feed an amp with 20 dB of gain and look for only a couple of volts to feed your speakers, then you have to feed your amp a very small signal. If your preamp has much gain, then when you attenuate the input to the preamp, you have to attenuate it that much more -- I found the input signal level to be attenuated down relatively close to the noise level in the voltage supply rails.

On the other hand, when I had the BOSOZ set to roughly unity gain, fed the full app. 2V CD player output signal, the level stayed a long way away from the noise in the power supply rails.

I put a roughly 200 ohm stepped attenuator on the output, and it sounded great.

JJ
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Old 28th April 2007, 01:49 PM   #6
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Hello Peter

Im buliding unbalanced version, 2k trimpot set to 150 Ohm,
10K Alps Black Beauty at output, DIP set as image.

Regards
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Old 30th April 2007, 09:16 PM   #7
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Hi Peter!
I also put a 10Kon the output, on an aleph 5 and it works good. Grtz teake see posts (one more) aleph p1.7 from Veteran
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Old 1st May 2007, 01:05 AM   #8
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Thanks alot guys, I will go ahead and put the 10k at the output.

Peter
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