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Old 27th December 2012, 12:48 AM   #671
bcmbob is offline bcmbob  United States
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I interpreted the sound as "smooth" which I also like a lot. I don't have any super efficient speakers, but with what I have, I wouldn't even attempt to get "room filling" super dynamic presentation from the ACA. I don't think that is what Mr. Pass had in mind when he designed it. I am very, very happy with mine as long as I keep my expectations realistic.
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Old 27th December 2012, 12:57 AM   #672
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My experience with the ACA was that one was easy to bias and the other was more difficult. I don't know if it was the potentiometer or something about how I built the amps. I do get room filling sound, but my speakers are very sensitive. My wife describes the sound of my DIY stereo as stark naked music. I built the preamp, speakers, and amps in quick succession. I have never heard any of the components with any other components, so I don't really have a way to tell what component is responsible for what sound characteristics. I do believe that the amps required no noticeable burn in time. However, I am using full range drivers and a tube pree, so the variables are many.
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Old 27th December 2012, 12:58 AM   #673
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Hi Bob,

The sound is smooth and I am realistic with my expectations, I only noticed this type of sound and I wondered if I did something wrong. I prefer a little more forward sound. I appreciate the effort made by Mr Pass as long as this is my first Pass amp because it is very affordable, easy to assemble and is delivered as a kit from the diyaudio store.

Best
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Old 27th December 2012, 01:39 AM   #674
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Quote:
Originally Posted by jcastellano View Post
I have built the ACA and I have found the sound a little "laid back". The type of sound that seems to come from the back of the speakers. I have tried with two different speakers, one Rega RS1 and one Monitor Audio Silver RX1. The sound was better with the Monitor Audio speakers (89dB) but the sound was similar to the Regas, as I said before, laid back. This sound is there from the very beginning, with no burning or run in.
The high output impedance may cause some speaker systems to sound different. Try something else.

Quote:
Originally Posted by jcastellano View Post
Also I found a little fuzzy to set the 10.00V bias. The pot did not allowed for an easy set, any kind of movement of the pot and the values went from one side to the other like a pendulous. I did my best to set the bias at 10.03 more or less each channel but it was really difficult.
Did you have a speaker connected? Bias can be hard to adjust without a good DC path to ground at the input and/or output. Check for 0VDC at the output or an electrolytic capacitor installed backwards.
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Old 27th December 2012, 02:02 AM   #675
billyk is offline billyk  United States
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I agree with the others that describe it a smooth. I have yet to finish building the speakers for the this system (mMar-Ken6p from Planet-10) but with my inefficient NHT Super Zeros I find the sound to be musical with nice pace and very detailed coming from a dead silent background. My setup is as an integrated with a B1 and use an ODAC as the source. When the sound gets a bit flat and thin, that's how I know I am pushing it to hard and have to back off the volume control knob!.
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Old 27th December 2012, 03:28 AM   #676
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Check on your cables and try replacing them. However, I don't want to start a cable debate and subjective perceptions.
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Old 27th December 2012, 03:36 AM   #677
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Hi, jcastellano

Have you ever compare your "laid back" to other 5W amplifier or a little watts SE ?
Maybe your laid back is more smooth than other punchy or airy amplifier, I meant a big amp that you've used before this unit :-)

Unique of sound is imporatant for DIY then you can select many many type of topology to your collection.
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Old 27th December 2012, 07:28 AM   #678
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Quote:
Originally Posted by jcastellano View Post
I have built the ACA and I have found the sound a little "laid back"........I have tried with two different speakers, one Rega RS1 and one Monitor Audio Silver RX1.
Both those speakers need a little more oomph than 5 watts is able to deliver. Have you listened to Class A in you system before? It sounds like nothing else (more like torque/grip than bhp) and at first it can be a little 'odd'.

I think what you may be experiencing is the full sound that Class A delivers and not realising that its probably more realistic, but the ACA is not powerful enough. Your speakers probably need one of the 'ACAstein' versions with a few more watts.

Better yet grab a pair of fostex 126 or similar and whip up a pair of Planet10's 'onken type boxes. Then you'll be in heaven g'teed
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Old 27th December 2012, 07:58 AM   #679
mc297 is offline mc297  Italy
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Originally Posted by Loudthud View Post
Did you have a speaker connected? Bias can be hard to adjust without a good DC path to ground at the input and/or output. Check for 0VDC at the output or an electrolytic capacitor installed backwards.
I had the same problem setting the bias: you have to do it with the speaker connected and also with the RCA cable connected to your source, keeping the source off during the operation.
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Old 27th December 2012, 09:07 AM   #680
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fostex or alpair .....

the JRKO suggestion will be perfect for you
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Last edited by nicoch58; 27th December 2012 at 09:10 AM.
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