Bi-amp or upgrade amp?

[02audionoob]

Suppose I have a 60-watt amp, a preamp with separate sets of outputs and bi-wireable speakers. If you were going to upgrade your amp power, would you add another 60-watt amp and go with a bi-amp setup or would you replace the 60-watt amp with a 100-watt or maybe 125-watt amp?

The components involved with this decision would be my Adcom GFP-565, GFA-535, a possible additional GFA-535 and replacement options like an Adcom GFA-545II or two GFA-535II.

[bobsticks]

Suppose I have a 60-watt amp, a preamp with separate sets of outputs and bi-wireable speakers...

Define "preamp with separate sets of outputs". Does this mean you have an internal crossover?

I've had good luck with bi-amping but I use a Multi-Channel amp internally bridged so it's kinda easy.

[02audionoob]

No internal crossover...just multiple outputs with different items in the path. The owner's manual talks about using the outputs labeled "bypass" and the outputs labeled "main lab" to drive two amps, such as in bi-amp setups. "Bypass" bypasses the tone controls and "main lab" can be made to bypass the tone controls with the "tone in" button. Only "main normal" goes through the capacitors. The other two sets bypass the capacitors, according to the manual.

[Feanor]

No internal crossover...just multiple outputs with different items in the path. The owner's manual talks about using the outputs labeled "bypass" and the outputs labeled "main lab" to drive two amps, such as in bi-amp setups. "Bypass" bypasses the tone controls and "main lab" can be made to bypass the tone controls with the "tone in" button. Only "main normal" goes through the capacitors. The other two sets bypass the capacitors, according to the manual.

I'm not sure what the "capacitors" you mention do: does your manual give any clue?

Other than that, it seems you can do passive biamping from you preamp assuming that you power amps have equal gain or have attenuators. Without one of these condition you won't be able to match the output volumes.

[02audionoob]

The manual says,

"The MAIN OUTPUTS NORM is capacitively-coupled using the highest grade obtainable polycarbonate film capacitors to preclude any degradation of signal quality,"

and

"The MAIN OUTPUTS NORM is ideal for use with power amplifiers which require a bandwidth-limited signal not extending down to DC. Although this capacitively-coupled output does restrict somewhat the extremely low frequencies, around 1Hz or 2Hz, it does not in any way degrade the quality of the signal, or restrict the low-frequency performance, in the audible range."

When referring to the MAIN OUTPUTS LAB and BYPASS outputs it refers to an unadulterated signal ideally matched for Adcom amps. Another comment...

"Both the BYPASS OUTPUT and the set of MAIN OUTPUTS may be used simultaneously should you wish to biamp or triamp your speakers or drive more than one amplifier."

It strongly recommends matched amps with respect to brand and model. That idea is why one of my upgrade options under consideration is two GFA-535II amps.

[Feanor]

The manual says
...
"The MAIN OUTPUTS NORM is ideal for use with power amplifiers which require a bandwidth-limited signal not extending down to DC. Although this capacitively-coupled output does restrict somewhat the extremely low frequencies, around 1Hz or 2Hz, it does not in any way degrade the quality of the signal, or restrict the low-frequency performance, in the audible range."

...

OK, that makes sense as capacitors act as high-pass filters. But wouldn't be overly concerned that you need to go with Adcom amps; any good amp will do.

However remember the level-matching issue I mentioned: at least one and more likely both power amps will need their own attenuators to match volume levels. The exception would be two exactly identical amps.

[E-Stat]

Suppose I have a 60-watt amp, a preamp with separate sets of outputs and bi-wireable speakers. If you were going to upgrade your amp power, would you add another 60-watt amp and go with a bi-amp setup or would you replace the 60-watt amp with a 100-watt or maybe 125-watt amp?

The challenge with bi-wiring using two amps is matching the levels. The tweeters likely need far less power than the bass section. You could get another amp with a gain control, but you'd be doing lots of experimentation. Bi-amping really requires an active crossover to optimize the setup.

I'd opt for a higher quality, more powerful amp.

rw

[Mr Peabody]

Estat hit on a good point, bi-wiring and bi-amping are two different things. Keep in mind it takes much more power to reproduce bass frequencies than mid to high range. It sounds like you are talking about bi-amping, letting one amp do the bass and the other do the mids/highs, in this case you want the bass amp to be much more powerful. Depending on what you are trying to achieve, it may be easier to get a larger amp. Either scenario involves buying another amp and bi-amping includes more complexity and additional equipment/gadgets.

Either way, as a side note, I have a gfa-5400 for sale. Just email or PM if interested.

[02audionoob]

Thanks for all the good input. I've now purchased a GFA-545II online and will eventually put the GFA-535 up for sale. Of the GFA-545, 545II and the 5400 I've read the best reviews on the 545II, so that was my first choice until the preamp manual got me thinking about the biamping.

My main objective in this upgrade is more power. I find myself cranking up the 535 pretty high, so I figured I'd try a more-powerful setup. It's a low-risk experiment. This 500-series Adcom stuff is pretty cheap and can be sold for as much as you pay for it.

[Mr Peabody]

If that don't do it, keep your eye out for a good buy on a 5500 or 555. I've heard the 545 has bigger bass than the 5400 but I don't know if that's a good thing after hearing the 5400.

The closer you go back to the original Pass design should be best though. And, I agree that the Adcom are a great value, especially on the used market.

[02audionoob]

I've read the 5400 spec's and it's a little high on the THD numbers, as compared to the 545II or the 545. I don't know much about Adcom's history, but I assume there must have been a fundamental change when the 545II gets noticeably better than its predecessor and the 5400 gets worse. I don't know if or how much the 545II varies from the Pass original, but it seems to reap some solid praise that the 5400 doesn't. The difference between all three could be small for my purposes, though. I'm not trying to create the perfect system, just a really nice but thrifty one.

On another note...I just scored a Dual CS-731Q turntable and a Sony TC-K909ES tape deck on craigslist for $25 and $55, respectively. I'm not a tape buff, but this deck sounds terrific, to me. The turntable of course sounds even better...spinning my all-time favorite LP, right now.

I also picked up a Phase Linear 8000A turntable for another $25, but it's missing the counterweight so I can't try it out. Wondering now where I'll ever find a counterweight...or if I'll be putting the 8000A back up for sale.

[basite]

THD barely matters, especially in music playback (well, excessive numbers (like 5% or 10% or so should be avoided at all costs though), if you look at some exotic manufacturers, you'll sometimes see THD values from 0.3 or 0.4%, and you will see some with values like 0.005, or less %


Keep the PL tt btw, it was based on Pioneer's PL1100 (I think...), which was a great tt, finding the original counterweight can be slightly hard to do, but with a bit of creativity, you can 'build your own' by using other stuff...

if you can't find an original replacement, look for tt's with similar arms (especially weight, or just weights that look similar),

My luxman TT was missing it's counterweight too, first I used some metal bolts and a screw to act as a counterweight, which 'worked', after that I installed a Technics counterweight (which I found on an old Technics broken tt, and it fitted with the help of a drill & a bit of rubber...

Keep them spinning
Bert.

[02audionoob]

Continuing on the thought of the PL turntable with the missing counterweight...If I put a cartridge on it and start it up, it goes through the motions and prepares to lower the arm above the record. Without a counterweight, the cartridge would land flat on the record, so I intervene and lower it just enough to let the stylus touch the record, as close to the correct angle as I can. At that point, is there any reason why the turntable wouldn't produce audio? I can just barely hear the sound, like when the turntable is on but the amp is off. Nothing is actually going out to the preamp. I assume this absence of sound would have nothing to do with the missing counterweight...true?

[E-Stat]

I assume this absence of sound would have nothing to do with the missing counterweight...true?

Assuming that the Adcom has an RIAA phono stage to which you are connected, that does not make sense. Cartridges generate output independently of tracking force so long as the stylus is intact. You may just get noise, but it won't be faint.

There is another villain.

rw

[JohnMichael]

The challenge with bi-wiring using two amps is matching the levels. The tweeters likely need far less power than the bass section. You could get another amp with a gain control, but you'd be doing lots of experimentation. Bi-amping really requires an active crossover to optimize the setup.

I'd opt for a higher quality, more powerful amp.

rw

I have a question. 02an was using a 60 watt amp to power the speakers. The power from the amp going into the passive crossover of the speakers. The crossover balances the output of the woofer and tweeter. Granted tweeters need less power but since both 60 watt amps are going through the speakers passive crossover will the tweeter receive any more power than the crossover will allow then if powered by a single 60 watt amp?

[Mr Peabody]

I've never bi-amped before but I've played with speakers that have had that feature, when the coupler or strap is removed how much if any of the internal crossover can be used? It may vary from manufacturer to manufacturer.

[JohnMichael]

I've never bi-amped before but I've played with speakers that have had that feature, when the coupler or strap is removed how much if any of the internal crossover can be used? It may vary from manufacturer to manufacturer.

I biwire my speakers and so I removed the straps between high and low frequency drivers. If I removed the HF wires I would only hear the low frequency driver. The straps send the same signal to the LF and HF drivers. If the amp is putting out a few watts of power the same goes to the crossover for the LF and HF drivers. The crossover balances the output of the drivers. My thinking is if you have one amp driving both drivers or two amps of equal power driving both drivers seperately the crossover would still balance the drivers. If both amps output are a few watts with one amp feeding the low frequency and the other the high frequency the crossover will still do it's job.

[JohnMichael]

I remeber something else I read about years ago but do not know if it would work. The idea was that amps work harder driving low frequency drivers than high frequency drivers. The idea was to use two matched stereo amps as mono blocks. You would take the two left channel outputs from the preamp and feed the L and R channel for one power amp. Next take both R channel outputs from preamp to the L and R channels of the second amp. The left amps L output to the woofer and The R output to the tweeter of the left speaker and the same for the right speaker. The idea was that only one channel would be working hard and the other had an easier time. Then you could use the balance control for any slight differences. Now that I have muddied the issue and since the new amp has been purchased anyway I will go get another glass of wine.

[Feanor]

I remeber something else I read about years ago but do not know if it would work. The idea was that amps work harder driving low frequency drivers than high frequency drivers. The idea was to use two matched stereo amps as mono blocks. You would take the two left channel outputs from the preamp and feed the L and R channel for one power amp. Next take both R channel outputs from preamp to the L and R channels of the second amp. The left amps L output to the woofer and The R output to the tweeter of the left speaker and the same for the right speaker. The idea was that only one channel would be working hard and the other had an easier time. Then you could use the balance control for any slight differences. Now that I have muddied the issue and since the new amp has been purchased anyway I will go get another glass of wine.

... "Vertical" bi-amping.

[02audionoob]

And back to the idea of the two different amps, where the more-powerful amp would drive the low frequencies...I will still have the GFA-535 when the GFA-545II arrives. Perhaps the answers to my own questions about bi-amping will start with an experimental 535/545 setup before offering the 535 for sale.

[Mr Peabody]

JM, it's true that it takes more power to reproduce low frequencies, if the crossover is still in effect and some how balances the power between high and low frequency drivers then I don't see any advantage at all to bi-amping.

[Feanor]

JM, it's true that it takes more power to reproduce low frequencies, if the crossover is still in effect and some how balances the power between high and low frequency drivers then I don't see any advantage at all to bi-amping.

Passive biamping (i.e. using the speakers' built-in crossovers) works because the speakers' crossovers limit the power drawn from the amplifier. The amp sees an infinite (or almost so) impedance at the excluded (filtered out) frequencies so can't power those frequencies. The power not delivered at those frequencies is available to power the non-filtered frequencies.

There might be the misconception that the crossovers absorb (and disipates as heat) the power of the frequencies they exclude -- this is not the case, as I understand.