Yamaha RX-V620 Lack of preouts

Discussion in 'Archived Threads 2001-2004' started by Rob Bruce, Jan 20, 2002.

  1. Rob Bruce

    Rob Bruce Agent

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    For my first post, I would like to start off with a little question that has been bugging me for weeks.

    I've been a long time home theatre enthusiast, but it hasn't been until recent;y that I made the plunge, and really started gathering components for my Home Theatre. A couple weeks ago I picked up a Yamaha RX-V620 reciever that I am very happy with (Even though most of the reviews I read complain about its sound quality). I think it sounds great, especially since my front speakers are a pair of Dayton Wright XG-8 Mark I Electrostatic Loudspeakers. Now, these are incredible speakers, with sound quality, and power to spare, but the problem with them they are rated at atleast [email protected] Now, I'm not sure of the exact power handling of them, but it's atleast 250. Now that's a little bit more than your average set of speakers, and it's way more than my Yamaha outputs ([email protected], but i doubt this is anywhere near actual output values). I need to get a separate amplifier to run the speakers, but herein lies the problem, the reciever doesn't have any preouts. Now, I have 2 options here, somehow convert the line outs to preouts (Although I think this would be a wasteful solution, and would probably degrade the signal quite a bit), or to rip open the reciever, and run some leads from the preamp to the amp inside the reciever. Now I'm all for the latter solution there, but I'm a little stumped in how to do this. It's not impossible, as a matter of fact, im sure it would be quite simple. I opened up the reciever, and had a look. I found a ribbon cable with 12 leads going to the amplifier circuitry, I figure if I ever get around to it, I can find which of these leads carry the signals to the amps for the front channels.

    Anyone actually pulled off a modification like this? Or does anybody have any details about this reciever that may help.
     
  2. Jeffrey Noel

    Jeffrey Noel Screenwriter

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    Hi Rob and welcome to the HTF!!

    I too have the 620, and feel it is a great receiver. But like you said, it unfortunately doesn't have pre-outs. I really can't provide any help, but I have heard from some threads awhile ago that said that you can take your receiver to some sort of electronics place and have them put in pre-outs for you. I don't know how expensive it would be, but at least you would have some sort of warranty or guarantee. I've been actually considering doing this.

    I hope someone with more info and expertise chimes in hear to help you out!

    Best of luck though!
     
  3. jeff lam

    jeff lam Screenwriter

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    I too have the 620 and I love the thing. The sound quality is better than I expected. Also has more than enough power. How long have you had the receiver? Why don't you trade it in and get a higher model that has preouts. Or you could just sell it on ebay or the for sale board here.
     
  4. Rob Bruce

    Rob Bruce Agent

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    Ive had the reciever for probably a month now. I don't really want to trade it, i'm quite happy with it. I just can't play it really loud right now. Maybe i'l reconsider it at a later point, but I"m pretty sure I can install some preouts. If I do, I'l make sure to post it on a webpage so you people can see it.
     
  5. Rob Bruce

    Rob Bruce Agent

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    Just a little update, i just traced the wiring inside the reciever, i can easilly wire up some preouts (Thanks in part to Yamaha for their amazingly well laid out bords with lables and everything). I gotta go buy some parts then i'l wire up preouts for my fronts (No need for the rest right now). I'l take some pics for those of you interested.
     
  6. Jeffrey Noel

    Jeffrey Noel Screenwriter

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    Thanks Rob. I'll be looking forward to your pics!
     
  7. Danny Owens

    Danny Owens Agent

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    If you are interested, Yamaha will sell you a service manual for about 18 bucks. I just got one for my RX-V1 and it has component level schematics.

    Danny
     
  8. Mike_A

    Mike_A Stunt Coordinator

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    i have my denon avr-2700 service manual, and what i found interesting is that (at least on the generalized block diagram) the "preouts" are derived via a simple resistor off of the amplified signal. seems kinda odd to me. as soon as i get a chance, i'll trace the signal through the actual circuit and see what happens in more detail.

    the other somewhat odd thing about this unit is that the preouts are available for FL/FR/C/Sub, but not for the surrounds. Probably a marketing thing, but it seems a sorta silly thing to leave out.
     
  9. Wayne A. Pflughaupt

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    Rob,

    A couple of things to keep in mind:

    First, if you do this you will immediately void your warranty.

    Second, make sure you take a continuity reading across the existing RCA jacks and the chassis. If there is no continuity, you will have to make sure any jacks you install are also isolated from the chassis.

    If you don’t want to void the warranty, there is another way to do this. You can turn the amplifier (i.e., speaker-level) outputs into a pre-amp level signal. If you have the skills to retrofit pre-outs, you will find this even easier. It amounts to soldering an RCA connector to a small-gauge speaker wire, so you can connect a signal to an outboard amp, with a couple of “tweaks.”

    First, you need to wire an 8-ohm, 10-watt resister across the positive and negative speaker connections. This will make the amp happy, as it will see a load.

    Next you need to reduce the signal level from the speaker outputs. This requires an in-line resistor on the positive lead (i.e., the RCA’s “tip” connection). It will be a trial-and-error to find the right resistor value to pad the signal down to an acceptable level for the outboard amp’s inputs, but the value will ultimately be in the tens or hundreds of k-ohms.

    I’ve done this before with success. As long as the receiver’s internal amp sees a load, it’s happy. Reduce the signal level for the outboard amp, and it’s happy.

    There are a couple of caveats, one being that this will, of course, keep the receiver’s amplifier circuitry in the signal path. Whether or not this is worth the benefits of convenience (i.e., being easier than retrofitting pre-outjacks) and keeping the warranty intact is a decision you will have to make. Also, there maybe be a higher-than-usual turn-on thump if the amps and receiver are turned on at the same time. It might be best to turn on the amps after the receiver.

    Hope this helps,

    Wayne A. Pflughaupt
     
  10. Wayne A. Pflughaupt

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    A couple of other things occurred to me: You will probably need at least a 50 watt resistor to load the amp. And, the trial-and-error problem of finding the right value for the in-line pad can be made easier if you have an outboard amp with gain controls.

    Regards,

    Wayne A. Pflughaupt
     
  11. Rob Bruce

    Rob Bruce Agent

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    yes, I thought of doing it that way, but most of the people i talked to on this forum just said buy a new reciever instead of trying that. I still have that idea in the back of my mind, as the intrnal preouts may not work. I got to thinking the other day, the signals that i was going to take the preouts from, they may not be volume controlled. I'm not sure if i grabbed the signal far enough along for it to have gone through the folume control. Well, there's only one way to find out. If it doesn't work, I'l either try to find a point further up, or try your idea.
     
  12. Patrick Sun

    Patrick Sun Moderator
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    My only comment on this topic is:

    Only 1 good outcome can come from this mod attempt, and so many other bad things.
     
  13. JerryW

    JerryW Supporting Actor

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    Well, worst case scenario is you'd end up having to buy a new receiver, and you're already considering that anyway. So... [​IMG]
     
  14. Wayne A. Pflughaupt

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    Rob,
     

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