Preamp Questions

Brusco

Do most use a preamp before their power amp? Is it something only preferred but not necessary on the front end of a power amp?

After a post on this forum I'm finding that a Power amp would be best for driving some recently acquired two 4 ohm SDA-1 speakers and I'm still trying to wrap my head around all this stuff. I have a Dynaco SCA-80Q amp that I would like to use but I think if I turn it up too loud it may have to work too hard to drive these speakers. I'm wondering if the Dynaco can be used as a preamp?

Ultimately I'd like to assemble a stereo system using my usual Tuner/receiver, CD Player, Turntable, etc. for my small music listening room (no surround sound or anything).

zingo

You need something to control the volume, and in front of a power amp, that is usually a preamp. Your Dynaco SCA-80Q has volume control, and these days would be considered an integrated amplifier. The Dynaco only has tape out, which is line level, so will not work as a preamp to feed a power amplifier. The unit doesn't have tons of power, but might still power the SDAs nicely depending on listening level.

If you want to step-up to a power amp, you will need to add a preamp, and there are many options that need to be considered if you're going that direction.

mhardy6647

Some power amplifiers benefit from added gain (i.e., an active preamp) between source and power amp input. I use a passive device (autoformer "volume control" with a source switch) to switch between sources and to attenuate signal feeding the preamp. I haven't - for my own application - yet found an active preamp (i.e., one with gain) that didn't sound just a little bit "worse" (i.e., more veiled, relative to my expectations) than no active gain stage between source and power amp.

This is NOT a universal truth! :-)

Brusco

zingo wrote: »

The Dynaco only has tape out, which is line level, so will not work as a preamp to feed a power amplifier.

What kind of connectors are used if it's not the usual line level? I'm guessing RCA are line level.

bthogan

Putting a pre-amp behind your amp is pretty standard these days. As zingo pointed out, your amplifier would be considered an integrated amp today, because it has volume controls and such. Some integrated amps can be used as pre-amps, but as zingo also pointed out, you won't be able to do that with your Dynaco (it looks like a nice piece of equipment, though).

As far as using it with those speakers goes, it is rated for 4 ohm use, which is good. It doesn't look like it has a tremendous amount of power, though. You may not be able to turn things up too loud.

I'll throw out some pretty common suggestions for "starter" separates, which would be able to run those speakers fairly well, without breaking the bank.

The Adcom GFP-565 has been many people's entry-level pre-amp. It's available used, for ~$250. They're getting a little long in the tooth (introduced in 1990), but they perform pretty well at the price point; they were considered a giant killer when they first came out. They show up on ebay fairly regularly.

I would also suggest an Adcom amplifier from their GFA line of around the same time: the Adcom GFA-535 will give you a fair amount of power, for $100 or less, used. The Adcom GFA-545 would probably drive those speakers pretty well, for around $125-150 used. The Adcom GFA-555 would certainly drive those speakers, and might even be overkill. They can go for $250-$300.

There are certainly other options out there, and as noted, that Dynaco should be able to drive your 4 ohm SDAs; it just might not give you a lot of volume (and it's also getting a bit old, which could affect performance). The Adcoms that I recommended are often thought of as entry-level equipment, but they should at least run those speakers without smoke or fire. They sound pretty good too, and you'll be able to turn the volume up a bit. Hope this helps.

mhardy6647

Neither the preamp nor power amp sections of the SCA-80Q are - how shall I put this? - very refined in their design nor their performance.

My suggestion to the OP - Buy yourself a nice high(er) power integrated amplifier (new or used) and be all set.

EDIT: Just in case the OP doesn't have a manual for his SCA-80Q, it's readily available online - here is one easy source: http://www.tubes4hifi.com/dynaSS.htm

Brusco

BTH, Thanks for all your suggestions.

I saw a used Adcom GFA-555 I thought about buying but I see they're getting up in age too. Some of them may need their caps replaced, and there's the issue with the fuses blowing..I wouldn't even know what to look for or how to inspect a used one. I'm no tech and can't be bothered with all the benchwork. It's just not my thing. I didn't know I would need a preamp to go with it. I guess I'd have to hunt down a GFP-565 separately.

The Dynaco sounds nice. I hooked it up to a couple of old Sansui S-47 Speakers. I had Sgt. Peppers on and it pretty much disintegrated the foam around the woofers. The bass sounded pretty good for a while there. Oh well. I wonder if they're even worth the refoam.

mhardy6647 wrote: »

My suggestion to the OP - Buy yourself a nice high(er) power integrated amplifier (new or used) and be all set.

MH: Can you throw out a couple of higher power integrated amp models that I could look for?
I would eventually like to be set like you say.. but good luck to that one.. like most around here, I'm concerned that once I get bit by the audio bug there will always be a better piece of equipment out there.

zingo

How much do you want to spend?

Look for something high current, so ideally it will double it's output power from 8 to 4 ohms.

bthogan

zingo wrote: »

How much do you want to spend?

Look for something high current, so ideally it will double it's output power from 8 to 4 ohms.

You know, now that you mention high current...

Parasound has a bit better sound quality than Adcom, I think...I'm just used to recommending Adcom as entry level, because they're cheap and plentiful, and good enough (though old)...but I love my Parasound HCA-1500 (the HCA stands for High Current Amplifier I believe). The HCA-1000 has 200 watts per channel, @ 4 ohms. Can't find any around at the moment, but they pop up on ebay, audiogon, etc. for around $200, maybe less. Not as old as the Adcoms, either. A little more expensive (the comparable Adcom GFA-545, as noted, can be had for close to $100), but I think you can hear the difference. And it drives power-hungry speakers better than the Adcom.

Brusco

I would rather not spend more than $500 total for a good sounding preamp & power amp. I will spend a little more if I was getting a good deal on used stuff. The thing is, I don't know what I'm missing by spending more at this point. I'm not too discriminating since I have never owned anything high end. Bang for the buck at this stage.. I have never even had a real audio system so I'm sure I'll notice huge advances just by having more power and having solid entry level separates.

bthogan

I'm pretty sure you can get an Adcom GFP-565 and a Parasound HCA-1000 for $500 ($300 + $200, respectively). You will be quite struck by the improvement in sound quality. Some other folks might have other suggestions, as well.

In fact...

Parasound HCA-1000

http://www.ebay.com/itm/PARASOUND-HCA-1000A-HIGH-CURRENT-DUAL-CHANNEL-POWER-AMPLIFIER-TESTED-V-TUBE-406-/300886432020?pt=US_Pro_Audio_Amplifiers&hash=item460e3a9914

Adcom GFP-565

http://www.ebay.com/itm/ADCOM-GFP-565-Preamplifier-GFP-565-Preamp-Processor-/130879841307?pt=US_Home_Audio_Amplifiers_Preamps&hash=item1e790be41b

There are some cheaper GFP-565s on there, and a cheaper HCA-1000 may show up. Just some examples.

Brusco

I have an Alesis RA100 power amp (100W @ 4ohms) made for driving nearfield studio monitors. Couldn't I go tape out of the Dynaco into the RA100 > into the SDA-CRS's?

Brusco

Dskip, That is a cool amp and not a bad price for something that looks handwired. Made in China! I would rather support USA made builders though. Any US builders in this bang for the buck price range? I love tubes. I'm not sure I want to be that committed to an amp that should be serviced every now and then.

Face

Brusco wrote: »

Dskip, That is a cool amp and not a bad price for something that looks handwired. Made in China! I would rather support USA made builders though. Any US builders in this bang for the buck price range? I love tubes. I'm not sure I want to be that committed to an amp that should be serviced every now and then.

Since we have minimum wage here, you're going to have to open your wallet for something made in the US.

Brusco

Couldn't I use the Dynaco's tape outs to go line level into the RA100 to drive the speakers?

zingo

The tape outs have no volume control, so no. Why not a passive or buffered preamp?

Sprags

Brusco wrote: »

I would rather not spend more than $500 total for a good sounding preamp & power amp. I will spend a little more if I was getting a good deal on used stuff. The thing is, I don't know what I'm missing by spending more at this point. I'm not too discriminating since I have never owned anything high end. Bang for the buck at this stage.. I have never even had a real audio system so I'm sure I'll notice huge advances just by having more power and having solid entry level separates.

There is a nice custom preamp at being sold my the CEO of http://www.tubes4hifi.com/home.html. I can tell you it's nice because I actually purchased it and used it with a custom Dynaco design based amp to drive the LSiM703's I purchased from suggestions here at this forum. The CEO offered a better preamp for more money but still a good price. He agreed to taking the preamp back towards the upgrade. The preamp is dead quiet and sounds fantastic. The thing is the more expensive preamp had a more dynamic soundstage. If you are interested email him at the the email on his web site and ask about the SP10 Woody.