Tube amp conundrum

[lattiboy]

Hi all,

I’m looking to bi-amp (had bi-wire there at first!) my Vandersteen Treo CTs and need some help.

1) I have this tube amp, which I think is very good! I upgraded the 6n2 with some gold lion tubes and was quite happy with the performance. However, one of the stock 6P1 tubes gave out and I want to upgrade all of them. I don’t see hardly any recommendations online for the 6P1 tubes so I’d appreciate any specific recommendations for an upgrade (not looking to spend more than $25 a tube)

2) I also have a great little APPJ EL34 amp that the previous owner (an engineer and designer) went hog wild on and upgraded all the caps and tubes. Sounds absolutely incredible!

3) Because it’s working and the other amp is offline, I tried using the APPJ for the mids and tweets on the Vandys…. and it was incredible!…… at about normal talking volume. Absolutely fell apart above that and I tend to listen loud, so I require more power.

Having used both of these amps extensively, the Analog Acoustics amp is easily 2x louder even though it’s only rated at 2wpc more. So, I’m hoping I can use that and not invest another large sum of money for a 15-20wpc tube amp.

4) If it isn’t enough, what would you all recommended in that power range? I’m fine with vintage, but think the Chinese stuff sounds great and I know I can get it affordably. I had the Yaqin ML10 (?) many years ago and thought it was great, but they’ve gotten quite pricey now and it seems like overkill for this application.

PS I’ll likely be using a Schiit Saga+ as the dual-out preamp if that makes any difference.

PPS Anything I should be worrying about here besides matching levels between the bass and mid/tweet amps? Never bi-wired like this before….

PPPS Yes, I have looked at high-power tube amps, but the Vandys need a simply ludicrous amount of power, and the only amps that drive them correctly are 150wpc or more.

/rant

 

[Lavane]

For the low end you definitely need more juice.
The old 3 channel consoles would use a single EL84 or 6v6 per channel, and a 6V6 push pull amp for the low end. Basically double or more power going to the woofer than waht was going to the mids and tweeters.

 

[lattiboy]

For the low end you definitely need more juice.
The old 3 channel consoles would use a single EL84 or 6v6 per channel, and a 6V6 push pull amp for the low end. Basically double or more power going to the woofer than waht was going to the mids and tweeters.

To clarify, I have two huge power amps that do a fine job with the bass (and a very good job driving everything). Denon POA2400 and Onkyo M506RS

 

[spantou01]

Hi all,

I’m looking to bi-wire my Vandersteen Treo CTs and need some help.

1) I have this tube amp, which I think is very good! I upgraded the 6n2 with some gold lion tubes and was quite happy with the performance. However, one of the stock 6P1 tubes gave out and I want to upgrade all of them. I don’t see hardly any recommendations online for the 6P1 tubes so I’d appreciate any specific recommendations for an upgrade (not looking to spend more than $25 a tube)

Lattiboy, I believe 6P1 is a chinese tube, modeled after the Russian 6P1P tube. The military qualified version is 6P1P-EB and very good. The 6P1P-EB tubes are not scarce or expensive, just check the Bay. The Ukranian sellers seem to be selling them and I recently received some (other tube types) from that country. $25 should pay for a matched quad plus shipping. I have many and could sell you a quad, but I currently don’t have a tester able to test and match them.

Good luck.

 

[lattiboy]

Lattiboy, I believe 6P1 is a chinese tube, modeled after the Russian 6P1P tube. The military qualified version is 6P1P-EB and very good. The 6P1P-EB tubes are not scarce or expensive, just check the Bay. The Ukranian sellers seem to be selling them and I recently received some (other tube types) from that country. $25 should pay for a matched quad plus shipping. I have many and could sell you a quad, but I currently don’t have a tester able to test and match them.

Good luck.

thanks! Found an eBay seller in Ukraine with good feedback and got a matched set for $19! It’ll take 2 weeks, but considering they’re located in an active war zone, really quite impressive!

 

[opnly bafld]

@lattiboy

You are wanting to bi-amp, not bi-wire.
That probably caused some confusion.
I know it did for me, I wasn't sure what you were asking about, and since you didn't mention the ss amps in the first post....

 

[gadget73]

yeah I didn't know what he was asking about either. Bi-amp makes more sense in context

anyway, "loudness" is more about gain than power output. If one amp is louder than the other, it probably has a lower input sensitivity, meaning it needs less signal input to make full output. 2 watts won't make that much difference in overall level, even at the fairly low power levels we're talking about here. Normally with bi-amp setups there is a crossover between the amplifiers and the preamp, and better ones will have the ability to adjust levels for each amp to make it all run at the proper level. Adjusting that should balance things out.


if you are running the amps full range, but only connecting them to part of the speaker thats not really the right way to do this. The amp is amplifying everything, but at part of the spectrum its effectively unloaded and thats bad for tube amps.

 

[lattiboy]

yeah I didn't know what he was asking about either. Bi-amp makes more sense in context

anyway, "loudness" is more about gain than power output. If one amp is louder than the other, it probably has a lower input sensitivity, meaning it needs less signal input to make full output. 2 watts won't make that much difference in overall level, even at the fairly low power levels we're talking about here. Normally with bi-amp setups there is a crossover between the amplifiers and the preamp, and better ones will have the ability to adjust levels for each amp to make it all run at the proper level. Adjusting that should balance things out.


if you are running the amps full range, but only connecting them to part of the speaker thats not really the right way to do this. The amp is amplifying everything, but at part of the spectrum its effectively unloaded and thats bad for tube amps.

Ah, I understand now. Also, I just read the Treo manual and our boy Richard V is not a fan of what I’m attempting!

 

[gadget73]

if the crossover isn't bypassed you probably don't want to be doing this with a tube amp then. solid state amps don't really care about working into no load.

 

[Squidward]

If a mono tube amplifier is seeing a load that is only the LF or HF section of a "split" (for lack of a better word at the moment) passive crossover, does that imply that it's unloaded for the opposite frequencies?

If your source includes an electronic crossover that restricts the frequencies to the limit of what the LF or HF section spans, is that any different?

If a tube amplifier is partially unloaded, is that better than being completely unloaded? Is it better for the amp to be unloaded at high frequencies where there is less energy expended?

Sorry for the major thread derailment.

 

[Squidward]

Also I had often wondered about the advantages and perils of running an active xover in to passive crossovers, and while I thought there would be the possibility for slope mismatches, etc. it didn't occur to me that it'd be all screwed up from massive phase shifting. This would be problematic for all speakers in that configuration, not just the ones in question, no?

 

[FlaCharlie]

I’m looking to bi-amp (had bi-wire there at first!) my Vandersteen Treo CTs and need some help.

I'm unfamiliar with bi-wiring since I don't have any speakers that are set up for that.

When bi-wired, do you use one of your SS power amps to drive the woofer and your tube amp to drive the mids / tweeter? If so, I guess that the bi-wire just eliminates the connection between the woofer and the mid / tweeter of the internal passive crossovers? Correct?

I've had excellent results with bi-amping and tri-amping using active crossovers. An active crossover goes between your source and the amps you want to use. So each amp only amplifies a limited range of frequencies. The outputs of the amps are then connected directly to the different drivers.

I've never tried to use them to power the woofer / mid / tweeter contained in an existing speaker that has it's own crossover. While I've mostly used them with separate drivers, I've also used an active crossover to send bass frequencies only to a 3-way speaker. In that case the internal crossover is intact but not functioning since there are no mid or high frequencies going to the speaker.

When using active crossovers, my strategy is to use a very wide range driver to handle all the mids, with no crossover involved within that range. Then use a separate bass driver. For the tweeter, I've had good results with both a 3-way active crossover and a 3rd amp powering a separate tweeter and with a 2-way active crossover using a simple first order passive crossover (just a single film cap) between the mid driver (which is run full range) and the tweeter.

If you want to try using an active crossover without spending a lot of money, you might want to check out the little $99 Rolls SX45. It has a continuously adjustable crossover point which can be set anywhere between 50hz and 2.5k with a rolloff of 12db / octave. It has separate output controls for the low and high and a master input level control.

 

[tonyg88]

I never used it yet but my klh6 speakers have the bi-wire option. In the default config there is a piece of metal on the inputs on the speaker that connects the tweeter and bass sections of speaker. Removing the metal piece would separate it and allow this. It is on my things to try but pretty happy with the sound of my fisher 800c as is.

 

[DeadTrader]

I never used it yet but my klh6 speakers have the bi-wire option. In the default config there is a piece of metal on the inputs on the speaker that connects the tweeter and bass sections of speaker. Removing the metal piece would separate it and allow this. It is on my things to try but pretty happy with the sound of my fisher 800c as is.

I was quite happy for 20yr with the sound my Revel F30's had then I bought new bi-wire speaker cables, they gave the old speakers a new and beautiful voice. Well worth the investment.

 

[gadget73]

If a mono tube amplifier is seeing a load that is only the LF or HF section of a "split" (for lack of a better word at the moment) passive crossover, does that imply that it's unloaded for the opposite frequencies?

If your source includes an electronic crossover that restricts the frequencies to the limit of what the LF or HF section spans, is that any different?

If a tube amplifier is partially unloaded, is that better than being completely unloaded? Is it better for the amp to be unloaded at high frequencies where there is less energy expended?

Sorry for the major thread derailment.

maybe not completely unloaded, but certainly into a very high impedance that edges towards being unloaded. Connected to the mid/tweet input of the speaker, its got no load for the bass end of the spectrum.


With a crossover upstream its still unloaded, but if its not amplifying any signal that doesn't really matter. The problem is when voltage swings are happening in the transformer with nothing to load it down. The voltages can get much higher than they would normally be.


I suppose a partial load is better than no load, and it may be enough to make this not really a problem but I tend to worry a bit. If I'm listening to bass-heavy music and the amp is being fed all that bass with nowhere for it to go, I'd worry that the output transformer is being abnormally stressed.

When bi-wired, do you use one of your SS power amps to drive the woofer and your tube amp to drive the mids / tweeter? If so, I guess that the bi-wire just eliminates the connection between the woofer and the mid / tweeter of the internal passive crossovers? Correct?

thats technically bi-amping, using 2 different amps. Its just doing it passively, running the amps full range and letting the speaker handle the split.

Bi-wiring would have you lift the jumper at the speaker and run 2 pairs of cables back to the same amplifier. The thinking is that the back EMF from the woofer won't get into the mid/tweeter because it terminates at the amp directly without the resistance of the wire to limit the damping. Or something like that.

 

[gadget73]

thats a good question that I don't have a really solid answer for. The woofer isn't exactly in parallel at higher frequencies any more than the mid/highs are in parallel at lows because of how the crossover works but it might end up shifting the nominal impedance to some other value. Ideally the manufacturer can provide that info.

 

[TriodeLuvr]

Ah, I understand now. Also, I just read the Treo manual and our boy Richard V is not a fan of what I’m attempting!

I'm not either. IMO, a better solution would be to drive the Vandersteens with a moderate power tube amplifier, but add an electronic high pass ahead of the amp. If the filter is set for roughly 100 Hz, it won't overlay filters in the speakers. Once this is done, you only need to add a SS subwoofer for fill below 100 Hz.

Jack

 

[FlaCharlie]

I'm not either. IMO, a better solution would be to drive the Vandersteens with a moderate power tube amplifier, but add an electronic high pass ahead of the amp. If the filter is set for roughly 100 Hz, it won't overlay filters in the speakers. Once this is done, you only need to add a SS subwoofer for fill below 100 Hz.

The little Rolls SX45 I mentioned earlier could be used to do exactly that.

Just set the crossover to 100 Hz and send frequencies above that using the "high" output to the tube amp. The frequencies below that can either be sent to a separate stereo amp using the regular "low" output or it also has a low output that's mono but has two output RCAs. So it can feed either one or a pair of powered subs.

I don't know how much power it takes to drive the Vandersteens, but I like using this approach because it generally allows you to use a lower powered tube amp. The bass frequencies, which are more demanding in terms of power, can be handled by a SS or Class D amp or sub. SS and Class D also tend to have higher damping factors, which produces a more solid bass.

I see it as an advantageous "division of labor", so to speak. It lets each type of amp play to its strengths.

 

[lattiboy]

Thanks @FlaCharlie, I am going to grab one of those and test it out! Will report back once I get the chance.

Also, there was a Yaqin CD2 tube buffer with GE tubes on eBay for $110 last night, so I grabbed it. Pretty well reviewed and may accomplish some of what I’m looking for in a much simpler configuration.

 

[opnly bafld]

Thanks @FlaCharlie, I am going to grab one of those and test it out! Will report back once I get the chance.

Your 8" woofers (acoustic couplers) only play from 80 hz down, so why bother?
It seems to me you will give up a lot more than you gain.

The binding posts apparently divide the signal at 900 hz, if they were at 80 hz then your biamp plan would work better IMO/E.