Amp for the 2B's - Keep or ditch the NAD 7400 power amp

rhythm · February 21

Hello,

I am looking at getting either a new integrated amp or preamp/amp separates, with the intention of running all my 2 channel sources to a 2 channel component instead of the HT receiver and using a bypass on the integrated/preamp when watching movies in surround.

Currently I am using the power amp in a 1989 NAD 7400 receiver to power my L/R mains (Polk SDA 2B's). I'd like to get opinions on whether or not I should stick with the 7400's power amp for these speakers, or if I should be looking at something different for amplification.

I could stop using the 7400 completely and go with a new integrated or preamp/amp separates. Or I could get a new preamp and continue using the 7400's power amp. I guess I'm just not quite sure how the amp in the 7400 compares to what is available today and whether or not the 7400's amp is a good fit for the 2B's.

Some integrated amps that I've looked at are Marantz (Model 50 or 30), Musical Fidelity (m5si), Vincent (SV-228), Rogue Sphinx V3, Primare (I15), Atoll (IN200)...

These models all seem to have nice 'companion' preamps too, so I could go that route too, rather than integrated.

So I welcome any advice on which direction you think would work out best for the 2B's.

Thank you,
Greg

rhythm · February 22

Well, even if you are not sure about the NAD 7400 being a good match for the 2B's, any comments on the integrated amps that I listed as possible replacements? Or other suggestions for these speakers?

Kex · February 22

The NAD 7400 is very old school. There probably aren’t any owners who frequent the forum regularly with that specific piece of gear, hence your lack of responses.

That said, NAD are known to outperform, especially the older stuff, so my somewhat educated guess would be that the 7400 will play well with the 2B’s, but you might want to consider having it refurbished at some point, to upgrade some components and check for oxydation on some of the controls.

Kex · February 22

P.S. Really fun read here, and some of the technology still applies to current NAD receivers:

Ken Rockwell Reviews the NAD 7400

Emlyn · February 22

My starting point would be to try a much newer separate two channel amp with the receiver. What is the model of receiver being used now?

rhythm · February 22

Kex, thank you for your input, and the link. I had read Ken Rockwell's review a while ago, but it was good to check it out again!

Emlyn, currently I have an NAD T758 AVR, with the Front L/R preamp outputs going to the power amp input of the NAD 7400 stereo receiver. I have to remove a jumper between the preamp out and power amp in on the 7400 to do this. So currently whether I'm listening to two-channel music or watching a movie in surround I'm using the preamp of the AVR and the power amp from the 7400 for the main front channels.

I would like to have my two channel music inputs going into a dedicated two channel preamp or integrated amp, which would have an HT bypass input so that the Front L/R preamp outs from the AVR could bypass the new preamp and go straight to whatever amp I'm using (separate or part of an integrated amp), when watching movies in surround.

I can't use the 7400's preamp for this because it doesn't have the HT bypass input. So the first thing I'm trying to determine is whether or not I want to continue using the amp in the 7400 as the amp for the SDA 2B's, or go with something different. Either way I'm going to end up with a new dedicated stereo preamp for 2 channel inputs, whether it's separate or part of an integrated amp.

Greg

Kex · February 22

If you like the NAD sound, you could consider two channel solutions such as the 275BEE (Class A/B) and the C298 (Class D), from $900 to $1,900 if you’re not averse to purchasing refurbished or open box from Safe and Sound HQ, a highly respected source.

Incidentally, the jumper removal solution you describe was still available on NAD receivers — including multi-channel home theater receivers — until quite recently.

rhythm · February 23

Kex, I do like the NAD sound, but open to other brands as well. Right now my first decision needs to be whether or not I stick with the 7400 for the power amp or not. They way they describe its power capability is a little confusing to me. I figured I'd want an amp that nearly doubles its continuous power rating from an 8 ohm to a 4 ohm load, but the NAD spec on the 7400 is a bit different. You get the 8 ohm continuous rating, and then a really high rating for 'clean burst power'. But I don't really know how to compare that against specs that I see for other amps. So I'm just trying to wrap my head around whether or not I'm getting the most out of my speakers with the 7400.

Thanks,
Greg

invalid · February 24

I went from an adcom gfa 555 amp to a krell ksa 300s to power my 2a's and it was a big upgrade. I think you are definitely leaving speaker performance on the table with the NAD.

odcics2 · February 24

I've been listening to my Monitor 7Bs with my Parasound HCA-1000A.
Very nice combination.

I bought the HCA in 1998ish, whenever it came out.
It's been a great, dependable amp whenever I call on it.

Extremely undervalued in today's market, IMO.

An amp you may want to consider.

rhythm · February 26

Thank you for your input. I'm currently looking around for an amp or integrated amp that seems like it would give these speakers the power that they want, but still need to not get too expensive. I was hoping I could stay at or under 2500 for an integrated, but if I get separates it will of course get much pricier than that for two high quality components.

odcics2 · February 27

I see Parasound HCA-1000A amps on ebay in the $250-300. range.

That’s super cheap for a John Curl designed amp that’s similar in topology to the Mark Levinson designs that John did for Mark decades ago.

On my Monitor 7B speakers, the HCA tightened up the bass and I can hear more mid and high details compared to a Carver TFM-35x I had them hooked up to.
Cymbal decay sounds more realistic.
You can get a P/HP 850 preamp to match the HCA. It’s Class A, no caps or inductors in the signal path.
Likewise, the amp can be run without caps or inductors in the signal path.

You don’t need to spend $2500ish for great sound, IMO.

invalid · February 27

It's a decent amp, but it's not even close to the amps he helped design for Mark Levinson.

odcics2 · February 27

For $250-300. bucks today, it’s a giant killer.

rhythm · February 28

The choices for a preamp are limited because for my setup I need both an HT bypass input as well as a fixed output. I've been looking at the Musical Fidelity m5si integrated - it has both of those features and at 150W into 8 ohms and 275W into 4 ohms it seems like it's got enough to work well with the SDA 2B's. But no final decisions made yet.

I hear you on the price benefits of going used. I've had a couple of not-so-great experiences going used before so I guess I'm a little shy about it, but you're right in that it can be a good opportunity for a great deal.

I thought perhaps I'd save a little money if I kept the 7400 for the amp, but if it's not a great idea to keep it for the 2B's then I'll gladly move on and get a new amp as well as a preamp (or integrated).

Sitka · March 6

My SDA 2B's are being driven by a Yamaha A-S2200 and the results are fantastic. Dreadnought highly recommended. The key is to feed those 2B's lots of current.

msg · March 7

Great plan on the M5si.

Not only does MF have the ****, but also a sweet sounding front end with the ability to present nuanced detail as well as image nicely.

I haven't heard the newer MF stuff, but the earlier gen integrateds I have are weighty and authoritative.

I have an A5 and A308. Two of the best splurges I ever made in this hobby. Each has beautifully run any speaker I've tried, albeit a limited selection of floorstanders and large bookshelfs. Neither is going anywhere.

Emlyn · March 7

The Parasound A23 is a good used option that'll drive smaller SDAs with no issues. Those still sell for close to their original price even though they might be more than a decade old. May be a good reason for that. I've had one in service for a long time in various systems. A used A52 could also be a good option to power mains plus other speakers. I still regret selling the one I had.

The A23+ is marginally better but much more $$. A Parasound integrated is another option that will have a similar power section to the A23 or A23+.

odcics2 · March 7

My old Carver TFM-35x has powered thirsty 4 ohm Ohm F speakers with no issues.

250 wpc 8 ohms
350 wpc 4 ohms

rhythm · March 8

Thank you all for your comments and input, I really appreciate the feedback. Still looking pretty stongly at the M5si, but right now I'm verifying whether or not the speaker outputs on it are common ground, as it does have a dual mono topography. Aesthetically, an integrated that I really like is the Vincent SV-228, but at 100/180 at 8 ohm/4 ohm, it's less powerful than the M5si, and I can't really find much information on whether or not it can deliver the high current. Still, the tube preamp section might provide some warmth to my bright room.

Thanks again,
Greg

JCL · March 8

rhythm wrote: »

Thank you all for your comments and input, I really appreciate the feedback. Still looking pretty stongly at the M5si, but right now I'm verifying whether or not the speaker outputs on it are common ground, as it does have a dual mono topography. Aesthetically, an integrated that I really like is the Vincent SV-228, but at 100/180 at 8 ohm/4 ohm, it's less powerful than the M5si, and I can't really find much information on whether or not it can deliver the high current. Still, the tube preamp section might provide some warmth to my bright room.

Thanks again,
Greg

I don’t know if the layouts for the amplifiers are the same, but I just bought the M6sPRX and it is common ground. I checked with the manufacturer prior to buying and below is a quote from the email that safe and sound got from them. I also asked a few other questions like if it might have an inverted channel like some of the carver amps.

Musical Fidelity says: According to our test results, at 4 Ohms the amp delivers 370W (continuous, at ≤1% THD/1kHz), both channels driven.

The amp is a common ground design, the speaker (-) output is connected to GND. Therefore no inverted channel

I would confirm it with the vendor you are buying it through. I used safe and sound for my purchase. I only live about 15 minutes from them so I was able to demo it and test the connections with a meter to make sure. I don’t recall if they have the M5si out for demo I know I’ve seen some of the integrated amps out, but I don’t recall which ones were out. If that’s who you are purchasing from Aaron could probably get the manufacturers answer pretty quickly.

John

Sitka · March 8

Hi Greg - check out Accessories4less.com - a reseller of factory refurb audio gear. They have the M6si for $2K, factory referb. They're a legit outfit, I got my Yamaha A-S2200 from them, no problem.

JCL · March 9

I went and checked continuity on the M5si. It looks to be the same as the amp I bought the other day. To be safe I would still check with the manufacturer.

John

msg · March 9

Curious, what is the second photo demonstrating? It looks like the same terminals are tested.

Is Fluke's continuity tester audible only, with no resistance measure displayed?

JCL · March 9

The first was the resistance but we did not zero the unit. The second was continuity.

msg · March 9

I found some stuff to read, but doesn't a non-zero resistance value across the negative binding posts also indicate continuity? I noticed you used your Fluke in both modes.

rhythm · March 10

Thank you for checking this out! Looks good, and I do have an email in to the manufacturer as well. And a local dealer is also checking too. I appreciate all of the feedback and help.

Greg

Schurkey · March 11

My Fluke 88 (not the newer 88V) shows that the meter leads have 0.2 ohms of resistance. If you're indicating 0.3 ohms without taking the meter leads into consideration--or "zeroing" the meter with the leads in-place--you have so little resistance between the negative terminals as to be of no concern at all.

"Continuity" could have substantial resistance between the measuring points; "continuity" is not the right test for compatibility with SDA speakers.

rhythm · March 20

I'm still waiting to hear back from Musical Fidelity and a local dealer on this. I did get on Safe and Sound's website and use the chat, and I was told there that the M5si is not common ground. But JCL's posts above seem to indicated that it is. Still need to hear back from MF. It sure is taking a while.

JCL · March 20

I would just wait til you hear from musical Fidelity. I’m pretty sure they will say it’s common ground.

rhythm · March 25

Ugh... Still haven't heard back from Musical Fidelity. I'm wondering now how it would be if I had any kind of technical issue with the amp and I needed to contact them. The response time isn't very encouraging.

On the plus side, JCL measured an M5si and it looked good, and someone at Hi Fi Heaven measured both an M3si and an M6s PRX in their store and said the negative speaker terminals were common.

But on the flip side, someone on the online chat at Safe and Sound told me it wasn't a common ground amp, as did someone at Upscale Audio (although I'm not sure if either of these statements were from doing a hands-on measurement).

Amp for the 2B's - Keep or ditch the NAD 7400 power amp

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