Using an Integrated As a Preamp?

[thebes]

I've got a Scott 299, a Fisher 500c and a Fisher x202 b. All
integrated's I was wondeirng if I could use any of them as a pre-amp to
drive my monoblocks for a different sound. Could I use the Tape
Out for this? None of them have anything that says "Use me for a
Pre" or "Send Signal to Another Amp".

If I can do this, do I need to have an extra set of speakers connected to the amplifier portion of the integrated?

Barring
that I do have a Ah'99 cd layer with a volume control. If I
use that and the volume pots on the monos to adjust balance what am I
losing by not having a pre in the chain?

Thought I'd ask before I burn up another piece of equipment through basic ignorance (my speciality!).

[Guest " "]

"Could I use the Tape Out for this?"

No, the tape out is line level at a constant 150mv. Meaning your volume controls will have no effect and your amp would run at about 10% of it's output.

"If I can do this, do I need to have an extra set of speakers connected to the amplifier portion of the integrated? "

If you had pre-out and power amp in, if your amp did not have speaker off switches, you would need a load of some type...speakers or a large 8 ohm resistor.

"Barring that I do have a Ah'99 cd layer with a volume control. If I use that and the volume pots on the monos to adjust balance what am I losing by not having a pre in the chain?"

This might work depending on the output level of your CD player. Check the documentation, if it can do 1volt output and it has a volume control, your in luck. I do this all the time with CD players that have volume and 1 volt output.

Other options....auto audio stores sell a black box designed to connect the output of a car stereo amp to the input of a power amp. This is used if the stereo amp has no pre-out. The black box is basiclly a 600 ohm resistor that seems to trick the stereo into thinking it has speakers whlie providing a 0 - 1 volt signal source into a power amp.

[thebes]

Thank you very much for the info.

But your not done yet.

I was just looking over a Fisher rig I puled from a
console. It consists of a pre/tuner and a seperate
amplifier. Now it apears that there is no power transformer on
the pre, with power for both units being supplied by the amp.
There are also a number of wires that run from the pre to the amp that
control things like the power on knobs, selectors, speakers etc.
However on the back of the pre there are rca's that say "To Power
Amplifier" as well as for phono and aux. On the front
panel however I see no knobs to switch to an external amp. The
speaker switch does allow switching from "Main to "Remote" to "Main +
Remote" but since there are two speaker hookups on the amp , one
unlabelled and one marked "External Speakers", I presume this is solely
for switching those connections.

Does this rig sound like it
willl fit the bill? Since i might not like the sound I'm not up to
removing the cords between these two and rewiring at this time. I'm
also not sure if two 100 watt monblocks I'd pair it with would provide
too much power to the pre. Should I just put a 8ohm resistor on the amp
speaker connections at the console amp so I don't have sound coming out
of four speakers at once.

Also you mentioned using a large resistor are you talking
something like a wirewound resistor or a a resistor of a certain
wattage value?

[Guest " "]

whats the complete model number...maybe I can find a schematic

The black box with the resistor.....the last ime I looked at one...it was a 600 ohm 20 wat wire wound resistor for each channel. But you can buy the black box off the shelf....you don't need to make one.

Here are some cheap versions...like 5 bucks.

http://www.partsexpress.com/webpage.cfm?webpage_id=3&CATID=35&ObjectGroup_ID=743

If you go to a car audio install place, you can get a nicer one that will handle more watts.

There are also autoformer versions of the balckbox which would be the way to go for long term use. But more bucks.

[thebes]

Ok here's the model numbers. The Amp is Chassis 480A and
Pre/Tuner is Chassis 490T. If you do have schematics I'd be very
interested in copies.

Here's a picture, the "To Power Amplifier" rca's are in the middle of the the back of the pre.

Sweet
sounding little bugger by the way. The amp uses 7189's. Gonna have to
refreshen this some day. Probably not a whole lot of wattage.

[Guest " "]

no schematic.

See the links about the high level to low level adapter reguarding your inital question.

What mono blocks are you driving?

[thebes]

Ok I can swing by an audio car store and get one of these but I'm not sure what it's doing and how I hook it up. I mean what do I use as an Output of say any of the Fisher integrateds to the monoblocks? Sorry I'm such a dolt but I just don't get it.

I need to use this setup as a temporary measure to my Bogen MO 100A monos. My Conrad Johnson PV3 has a problem and I wanted to use these amps while the pre goes to Craig for service.Obviously I've got other equipment I could use but I really do love the sound of these rebuilt Bogens on my downstairs system running them through some Heresy's. I'd also like to play my records which rules out the cd only option.

I listen to this setup while I compose my trenchant observations and pithy pearls of wisdom for the various inhabitants of this forum. Sure in your best self-interest you would make sure my downstairs system never works again in hopes I would go someplace else but if I did maybe you'd miss me just a little bit.[]

[Guest " "]

"Ok I can swing by an audio car store and get one of these but I'm not sure what it's doing and how I hook it up. I mean what do I use as an Output of say any of the Fisher integrateds to the monoblocks? Sorry I'm such a dolt but I just don't get it."

Yes. Tell them you want to connect what would normally be speaker connections to a power amp. They do this all the time with car stereos that do not have pre-amp output jacks. If you start talking about tube amps and mono-blocks, you will probally confuse them and wind up leaving empty handed.

When you get the black box, it will either have wires to connect to your intergrated amp's speaker termianls, or it will have normal speaker terminal screws that will allow you to run wires from your integreated amps speaker terminals. On the other end will be cables with RCA jacks that go to the input of your mono blocks.

You only need the auto version if your integreated amp can crank out more than 15 watts. If your integrated amp is 15 watts or less, you can order the parts express version.

[thebes]

Ah the light bulb in my head finally lights up! I get it. Yeah I'd probably use the Scott 299 (17 amps a side), or the Fisher 500c's which are mroe powerful so yeah I think I'll hit the local auto store and then have some fun trying out some different sounds.

I'll report back when I've got it up and running. Thanks are definetly in order!

[Guest " "]

Sounds like you will have an intresting weekend.

If you decide you pursue this furthur, I can send to a diagram on how to add a pair of autoformers to the mix which will lower your noise floor, improve dynamic range, and reduce distortion. It's not a free ride though, it will take more output on the part of your pre-amp, but if you are using an integreated amp as a pre-amp, power won't be an issue.

[hwatkins]

Marty - keep me in a PM loop on your results.

I am remodeling my downstairs listening area (as in all such projects the is a loose timeframe) as step 5 in a house redo - so I have a bit of time. A few weeks ago I started the napkin design and came up with a similar thought for my Fisher 400 - Fritz has just made it bunches clearer and I will be looking to do something in the vein of your experimentation. I had been considering selling the 400, but it is just too sweet for me to part with it.

Bring the twins by and we can discuss.

[thebes]

Eureka! It Works!

I went to a car audio store
yesterday and spent $25 for a "SNI-35 Adjustable Line Output Converter"
by Pacific Accessory Corp. (PAC) and hooked in up a couple of hours ago
to my Scott 299a. At first it was too loud and distorted but I
simply adjusted the two pots downward and it sweetened right up.
I've only tried it with a couple of cd's so far and I haven't tried it
with the phono section but it's quiet an detailed. No firm
conclusons yet on how it will handle the gamet of music I play and I
want to try this with some other integrateds for listening flavors.

I will definetly report back further on this.

Oh here's the specs as listed on the package:
designed to handle car radios with output of 2-40 watts (RMS); uses
audio transformers for noise isolation, is phase adjsuted, has 0.5dB
lionearity from 20-2000HZ and rolls off below 20HZ for subsonic
reduction.

Not sure if I will stick with it for a dedicated pre.
Talked to Craig yesterday about my ailing Conrad Johnson PV3, told him
what I was doing, and he said if you wanted do something like it
permantly there is a way to trace the wires back from the "Tape Out"
move them to (I think he said the balance pot but don't quote me) add a
couple of really small capacitors and you could use it as a
full-function pre-amp. Of course, he said you burn through some
power tubes over time since the amp part of the integrated will always
be on.

Henry it will probably take me a couple of weeks with this
to give a full report but if you do anything before then make sure what
you buy can handle the wattage of the Fisher 400. Methinks that
aspect of this is probably very important.

So Speakerfritz, thanks again and what's the idea behind these
"autoformers" ? I know nothing about them and are they usually
employed in pre-amps or just an add-on from the DIY community?

[thebes]

Nevermind about the autoformers I just saw your post over in 2 Channel. Very interesting.

[Guest " "]

"Eureka! It Works!"

Of course it works...I would not steer you wrong...

[Guest " "]

"Oh here's the specs as listed on the package: designed to handle car radios with output of 2-40 watts (RMS); uses audio transformers for noise isolation, is phase adjsuted, has 0.5dB lionearity from 20-2000HZ and rolls off below 20HZ for subsonic reduction"

Very respectable spec's.

[thebes]

"Eureka! It Works!"

Of course it works...I would not steer you wrong...

It;s

not you I was worried about! I have a propensity to wreck

perfectly good equipment through general stupidy and/or

clumsiness.