[roymail]

I really like the sound of quality passives in my single source system.  I know it's not for everyone, but it's a sound that I prefer.  No need to discuss all the pros and cons, it's all been said before.  And, I know that tube amps are probably a good choice with their 100K input impedance, but tubes are not for me.

That said, I'm considering several SS amps that would provide quality sound, synergy and not break the bank.  At the top of my list is a used McCormack DNA-125, 100K input impedance and great reviews and customer service.  Also, the potential to have it upgraded is a plus.  Any good SS amp rated at 47K input impedance or higher and normally low sensitivity will work pretty well.

Right now I'm still using the amp side of my Luxman 50 wpc receiver which sounds very nice with the Goldpoint stepped attenuator I used and Lightspeed LDR that I tried.  Any lesser passive (won't name names) doesn't sound good enough for me.  But I admit that I have not tried them all.

I'm not asking for a discussion or recommendations of different passives, only SS amps that would integrate well into a system using a passive volume control.  What have you used before with good results?

Thanks very much for your input. 

[33na3rd]

I don't know what speakers you are running, but the First Watt F6 looks interesting to me. 100K Zin.

I have not heard this amp, but like you, I've been looking at amps to run with a passive.

On the Tortuga Circle there's a brief review by TJHUB, whose running his Odyssey Stratos Monos with the Tortuga Audio passive with good results. The Stratos operate at 22K Zin, which is on the low side for a passive.

The Job 225 has a Zin of 51K & an input sensitivity of .75 volts. I have not heard this one either.

It will be interesting to see what others suggest.

[konut]

I've been happy with Wyred4 Sound SX500 monoblocks, 60.4k ohm input impedance, 2.1v sensitivity in conjunction with a Tortuga passive.

 https://wyred4sound.com/products/mono/sx-series

[roymail]

Thanks for your reply.  The First Watt F6 produces more heat than I like and costs more than I'm able to invest.  The input impedance of the Statos amps is too low for my liking.  On the other hand, the Job 225 appears to be a much better candidate for a passive.  Although I'm still leaning toward the McCormack DNA-125. 

Konut, I remember your post about the Tortuga and the Wyred amp being a good match.  I've never heard a Wyred amp, so I really can comment.  Thanks for jumping into the discussion.

Hope others will respond with more suggestions.

[OzarkTom]

You can usually find a Crown XLS 1500'amp used for $150-200. They sound pretty good for the bucks. The resale on these amps are very fast on EBay in case you do not like it. I sold a used XLS 2500 last week in less than 24 hours.

[RPM123]

I'm using a W4S STP/SE with the Job 225 and they work quite well together.

[WireNut]

I think with a passive preamp and good efficiency loudspeakers is a great way to go. My setup require's a preamp with additional gain.

[RDavidson]

I'm using a W4S STP/SE with the Job 225 and they work quite well together.

The STP SE isn't a pure passive. It has an output buffer.

[RDavidson]

I think McCormack is a solid recommendation. Check the input voltage sensitivity. It is pretty low (1V I believe), at least on the DNA .5 and DNA 1. Steve designed passive preamps during that timeframe (to be mated to these amps). I think the high input sensitivity carried over to the 125 and 225 series also, but I'd have to check. The DNA .5 Deluxe is an excellent amp. I'm sure its newer brother the 125 is also great.

[WireNut]

The STP SE isn't a pure passive. It has an output buffer.

Right. I don't completely understand a buffer preamp, Dodd audio made one, but if it controls impedance miss match I think that would be a great option if you don't need additional gain. Could make for a great sounding system.



   

[RDavidson]

Right. I don't completely understand a buffer preamp, Dodd audio made one, but if it controls impedance miss match I think that would be a great option if you don't need additional gain. Could make for a great sounding system.

It's actually quite simple. A pure passive is an adjustable attenuator with no means of impedance matching. A buffer preamp is a passive input/attenuator stage, but with the addition of an active output stage in the same box. The output stage doesn't provide gain. It just provides the amp with a low impedance signal and appropriate voltage (usually 2V), which is ideal for the majority of amps.

It's essentially the same as buying a passive preamp and a separate buffer (tube or SS), but without the IC's connecting them. The point of a buffer is impedance matching between source and amp, but in some cases, they have been marketed as "flavor" boxes....which just perpetuates the misunderstanding of their real purpose.

People running straight from source to amp may find a buffer useful, even if they don't know it.

[WireNut]

If I could do it all over again I think I would go for a Bent Audio Tap-X with some high efficiency loudspeakers and a good tube amp.

[RDavidson]

I'd love to get my hands on the VERY rare balanced Bent Tap X, fully featured with remote and multiple inputs and outputs also. I'm very pleased with my STP SE though, and feel I would have to upgrade to a Bent or something of its engineered caliber, to get an appreciable increase in precision and fidelity.
I saw a fully featured Bent come up for sale a year or two ago, but I hadn't had my STP SE very long and just wasn't in a comfortable position to spend again. Thank goodness it sold almost immediately, or maybe I would've (unwisely) let money leave my wallet.