Using pre-outs...

[venkatcr]

1. i had set a ballpark figure of about 25k for the 2 channel amp. sand64 seems to be eyeing similar territory. given the avrs we have, would an amp in that price bracket produce DISCERNIBLE improvements for 2 channel music ? or do we have to move higher up the chain ? assuming that 25k is all that we are willing to spend, should we bother at all or simply go for bi-amp???? (i know its not the same thing as getting a 2 channel amp; just asking )

Given that your AVRs are Yamaha 863 and Denon 2310, it will be difficult to get a two channel amp at 25K to make any marked improvement in sound signature. As I had mentioned elsewhere, modern AVRs would very closely match the sound signature of 2 channel amps at around the same price range. So if you start looking for a jump in SQ, you have to start looking for amps in the 50K range.

What I would suggest is as follows:

1. Bi-amp your front speakers using the rear channels of your AVR. Use the system for a few days, and get acclimatised to the sound signature.

2. Using the same CDs, listen to a few popular amps at 25K to 50K. Skip the usual suspects such as NAD and CA, and try auditioning amps from companies such as Rotel, Arcam etc. If you find a significant difference is SQ, then you are on the right path. If you cannot make too much difference, stick to the AVR and enjoy what you have.

2. the other option is to go with a 2 channel power amp. somebody on the forum mentioned a sonodyne power amp quite a while back. any suggestions ?

With both the 863 and the 2310, you have ample power at your disposal, unless you have mismatched speakers. Why would you be looking for a power amplifier? Remember, a power amplifier is a dumb unit. The sound signature is defined by the pre-amp - in your case by the AVR. If you need to change the sound signature, you to change the pre-amplification.

Cheers

 

[ajinkya]

There are always specialised equipment available. But these have to be used with complete knowledge of what you are doing. BTW, I have found the volume control of the Oppo to be completely useless. I don't have any idea, but I think the audio amplitude of the Oppo is very low, and you have to keep the players volume full to hear anything.

Venkat,

I don't think the trim inputs are a specialised feature. All parasound models I've come across have them and most adcoms do. Many people use their functionality if they connect an old power amp to say their digital players, pc for their second bedroom setup sometimes.

I have heard the Oppo connected to a NAD (T742) and a Denon(1507) AVR. In both cases, I had to make the Oppo volume full (20 steps) and then adjusted the AVR volume for control. It is more than loud for us at around half of AVR volume for the Denon and 3/4th for the NAD. Which is the AVR model that you're using?

-Jinx.

 

[venkatcr]

I had to make the Oppo volume full (20 steps) and then adjusted the AVR volume for control. It is more than loud for us at around half of AVR volume for the Denon and 3/4th for the NAD. Which is the AVR model that you're using?

I used the amp with a large set of amplifiers... my own Onkyo 875, an Arcam FMJ amp, a Cayin tube amp, and TheVortex's Lyrita tube amp.

When you connect to any external amp, of course, what the player outputs is not that relevant. I was referring to the use of the player with a unit such as TV that has limited amplification capabilities of it's own.

Cheers

 

[suri]

Attenuators on a Power amp were considered by most audiophiles as NOT A PURIST APPROACH - hence they were dropped from most power amps as the attenuators were a source of channel imbalances in quite a few cases!

However, the models that did have them allow direct feed of healthy Line-Levels signal sources like a CDP direct into them. Most PA power amps will have this feature as its a norm in the Pro-Audio industry.

hi audio_engr

is that why most of the good (audiophile) power amps (like symphonic line:licklips have just a power-on switch on the front fascia?

 

[venkatcr]

Thanks Cranky. As always I treasure your knowledge and explanation.

On a humorous note, maybe I should send you one of the speakers switches I made for your test and evaluate?


Cheers

 

[spirovious]

I would avoid speaker switches like the plague. The contact resistance of a switch is high enough to degrade performance significantly. Good switches (and relays) cost a lot of money - some as much as a few hundred dollars. It's probably to avoid the hassle altogether and lump it with the AVR till you can actually afford a better setup.
.

Can a DIY manual switch work better?
Is it safe to use press type switch easily available in market?(6/9... pins)

 

[spirovious]

^^No.

10 characters

I was planning for this type,what may happen with this when used both amps off.(switching before turning on amps)

 

[ranojoy]

thanks to venkatcr (http://www.hifivision.com/amplifiers/8753-using-pre-outs-3.html#post117807) and cranky (http://www.hifivision.com/amplifiers/8753-using-pre-outs-4.html#post117820) for their (as usual) lucid replies.
but no thanks for doubling my budget to 50k .

just when i was seriously considering a membership in the non-spenders club ...........:sad:

 

[Asit]

Hi folks,

I have a simple query, not too far away from the main discussions here, so may I have your permissions .

For the last many years I know this: Good pre-amps have low output impedance and good power amps generally have high input impedance so that they can be mated well. Now my question is: Why is this? What would happen (technically) if a pre-amp with highish output impedance is connected to a power amp with lowish input impedance?

I know what is meant by impedance. But the trouble comes when one puts the qualifying words 'input' and 'output' in front. I think my question shows clearly I have not understood what these input and output impedances actually mean.

Gurus, please clarify.

Regards.

 

[spirovious]

spiro: That switch can take about 1 ampere before self-destructing. Do the math.

That kind of switch is not meant for switching audio. If you really need to use two amplifiers and one set of speakers (beats me why you would want to do that if they are all in the same room), use a couple of high-current relays (30 amp+) and this switch can be used to turn on the relays.

Thanks,
I will add stereo amp which will be paired with same spk.So will need switch OR I will have a board with banana plugs where I can switch manually.

 

[venkatcr]

I will add stereo amp which will be paired with same spk.So will need switch OR I will have a board with banana plugs where I can switch manually.

If you are going to do things manually, you might as well have two sets of speaker cables, and switch at the speaker end.

Cheers

 

[ajinkya]

I used the amp with a large set of amplifiers... my own Onkyo 875, an Arcam FMJ amp, a Cayin tube amp, and TheVortex's Lyrita tube amp.

When you connect to any external amp, of course, what the player outputs is not that relevant. I was referring to the use of the player with a unit such as TV that has limited amplification capabilities of it's own.

Cheers

Got it. Yes, acting as a standalone 'amplifier', the Oppo may have difficulty driving loads to a high enough volume level. I was assuming it's use as a source to an external amp, hence the query.

 

[ajinkya]

To illustrate what the effects are of a preamp's output impedance on the sound, I'll take some avg Belden cable (9223) which claims a cable capacitance 37pF/ft. Let's assume an interconnect is made of length 6ft of this Belden, which yields 222pF. If we had an amp with an input impedance of 47,000 ohms (quite a typical value) and a preamp with an output impedance of 4,700 ohms (using now 1/10th rule instead of the earlier 1/20th for easy illustration), this Belden cable will give a system result of being -0.06dB @ 20kHz, i.e. 0.06dB down at 20kHz freq.

Hi audio_engr,
Just to confirm my understanding: this effect is exactly the same as the reason for a good voltage source having negligible internal resistance, correct? Same rules apply - if the objective of the voltage source is to supply constant voltage across 'any' load (within the operating tolerance of the supply), it must be able to supply any current at that constant voltage. Which means that any load connected across it should have a higher resistance than its internal resistance. Same will be true of a constant current source, with its internal resistance being very high, to negate the effect of any load resistence being connected in series, to the current from source.

When you talk about distortion occurring because of impedance ratio mismatches, are you talking about the preamp circuit being driven to its saturation limits or something entirely different? Also, the - x dB you calculate is what system parameter exactly?

Thanks,
Ajinkya.

 

[Asit]

I think cranky was talking about distortion, not AE. I had a similar question to ask cranky, however, didn't find the time during the day.

Now, I was just trying to understand AE's calculation. as far as I understood, he is calculating the total impedance seen by the output stage of the pre-amp including the capacitive contribution of the cable. He is then taking a ratio of this impedance and the one without the cable and then relating this ratio to the inverse of the power ratios in the two cases and then naturally the ratio leads to the db.

I hope it is something like this.

About a year ago while considering pre-power amps I read in other forums about the dependence on the cable for pre-amps with not-so-low output impedance. Thanks for explaining it again, AE.

Regards.

 

[ajinkya]

Thanks Asit. That is what I surmised as well. In that case, it is exactly the same as my analogy for what goes on in a constant voltage source with varying load. We are trying to minimise changes to the ideal behaviour of the device by making its internal impedance small enough that outside disturbances have negligible effect on the steady-state voltage.

-Ajinkya.

 

[gobble]

The audible results of good impedance matching are increased frequency extension at both extremes. I got a taste of this last year when I auditioned
George's Grounded Grid preamp.

I was waiting to write to about this in my review of my new speakers and the preamp later this summer, but since this is a happening topic of discussion now, let me briefly describe the effect of the Chinese clone GG. Now both the CDP <>Pre and Pre<>Power sections have impedances matched by a ratio of 10X.

The puny budget NAD which some have called anemic ( now I see why) is suddenly transformed into a powerful Hulk. It performs now with a sense of authority. Deep impact at low volumes, tremors traveling through the thick mattress of my bed, tingles running through fingers even with vocals that go down low .... Its like an amp on steroids now. The high frequencies are also more solidly defined with improved extension.

With a budget CDP that is likely ot have relatively high output impedance, and a budget power integrated having a modest input impedance, a good preamp that fits in with the right amount of input and output impedance matching can breathe new life into ones setup. :licklips:

HTH
Regards

 

[spirovious]

If you are going to do things manually, you might as well have two sets of speaker cables, and switch at the speaker end.

Cheers

Thanks Venkat & Cranky,

2 spk cables can be costly as I recently upgraded to Supra classic4.0 for Rs.400/mr.

I will be switching manually close to the amps(both).
ie total 3 spk cables(per ch), 2 will be short(before switch) & long as output cable(to spk)
I hope this may not degrade SQ as there will be interruption @ switch level.

 

[ISO]

Hi folks,

I have a simple query, not too far away from the main discussions here, so may I have your permissions .

For the last many years I know this: Good pre-amps have low output impedance and good power amps generally have high input impedance so that they can be mated well. Now my question is: Why is this? What would happen (technically) if a pre-amp with highish output impedance is connected to a power amp with lowish input impedance?

I know what is meant by impedance. But the trouble comes when one puts the qualifying words 'input' and 'output' in front. I think my question shows clearly I have not understood what these input and output impedances actually mean.

Gurus, please clarify.

Regards.

Amplifier having low input impedance is unlikely but for the sake of debate if this happen then some of the power of preamp will get wasted across input of power amp. Hence you will not full power and intended frequency response.

Hi folks,
I know what is meant by impedance. But the trouble comes when one puts the qualifying words 'input' and 'output' in front. I think my question shows clearly I have not understood what these input and output impedances actually mean.

Gurus, please clarify.

Regards.

Let's not go in to too much technical. Output impedance is effective resistance that comes in the series with the output. so lower is better cause there will be less power wasted across it.

Input impedance is effective resistance come in parallel to the input of the amplifier. So higher is better.

 

[Naturelover]

Amplifier having low input impedance is unlikely but for the sake of debate if this happen then some of the power of preamp will get wasted across input of power amp. Hence you will not full power and intended frequency response.

Friend, this is a 7 year old thread :lol: