Tube pre-amp with ss amp?

[StanleyMuso]

I have been intrigued by the tube sound for a while (I remember what they sound like from my childhood years), but I only upgraded to a Musical Fidelity amp driven by a Rotel pre-amp a couple of years ago. On the whole, I'm happy with this set up, but for some types of music, ie classical vocal, violin etc, I wonder if I would get a warmer sound if I introduced tubes? I don't have the money to change the whole set up, or to set up an alternative system, but thought I might experiment with a tubed pre-amp just for certain uses.

Has anybody else mated a ss amp with a tube pre-amp? Is this a successful comination?

Thanks.

[JoeE SP9]

Since 1981 or so I've been using a tube preamp with various SS and tube power amps. Using the tubes as early as possible in the chain is the way to go. It's the best way to get that "tube" sound. :cool:

[Mr Peabody]

Tube/SS combo is a commonly done configuration. In fact, it isn't hard to find integrated hybrids that do this. It is also pretty well accepted that preamps aren't Rotels strong suit.

As you look for a tube preamp check the output impedance, the lower the better for use with SS. I'd have to research again but if memory serves you want below 500 ohms. What price are you looking for? I have a Conrad-Johnson PV14ls2 which new is about $2,500.00 and I think it is incredible for the money. There are several good tube preamps in this price but C-J is the only one I found that offers remote and it's variety of input and outputs. You can find older C-J models on Audiogon for under $1k. Again, be sure to ask the seller or Google the model to check for features, you'd be surprised at how many tube preamps do not come with a remote. I like tubes but I'm not willing to get off the couch every time I want to adjust the volume.

A couple of other options would be to try the Musical Fidelity tube buffer or possibly adding a tube DAC. A very good one I see going cheap used is the EAD 7000 something, I don't remember the exact model but it's the only one with 7000. Also, you can raise your systems sound a level by using a quality interconnect between amp/preamp/sources if you don't already. From brands like Transparent, Audio Quest, MIT, Cardas etc. Notice I didn't say Monster.

[JoeE SP9]

Tube/SS combo is a commonly done configuration. In fact, it isn't hard to find integrated hybrids that do this. It is also pretty well accepted that preamps aren't Rotels strong suit.

As you look for a tube preamp check the output impedance, the lower the better for use with SS. I'd have to research again but if memory serves you want below 500 ohms. What price are you looking for? I have a Conrad-Johnson PV14ls2 which new is about $2,500.00 and I think it is incredible for the money. There are several good tube preamps in this price but C-J is the only one I found that offers remote and it's variety of input and outputs. You can find older C-J models on Audiogon for under $1k. Again, be sure to ask the seller or Google the model to check for features, you'd be surprised at how many tube preamps do not come with a remote. I like tubes but I'm not willing to get off the couch every time I want to adjust the volume.

A couple of other options would be to try the Musical Fidelity tube buffer or possibly adding a tube DAC. A very good one I see going cheap used is the EAD 7000 something, I don't remember the exact model but it's the only one with 7000. Also, you can raise your systems sound a level by using a quality interconnect between amp/preamp/sources if you don't already. From brands like Transparent, Audio Quest, MIT, Cardas etc. Notice I didn't say Monster.

Thanks Mr. Peabody. I'm currently looking around for a replacement preamp. I prefer tubes and want remote volume and theater bypass. My current ARC has only the tubes end covered. I'll now be checking out CJ's PV14. Although I was looking to spend ~$2500 on a used unit I have no particular objection to new.:cool:

[StanleyMuso]

I have not set a specific budget for this, and I'm not in a hurry because at the moment my funds are low, and need to save. Your point about the remote is a good one - my previous pre did not have it and it was a pain having to jump up each time the volume needed adjusting. The output impedence question I would not have even thought to consider if you had not metioned it - thanks for that also.

Both your replies have encouraged me to investigate this possibility further. I always suspected that the Rotel was a weak link. In addition, when funds are available, I intend to get a dedicated CD player as well - I now have two DVD sources, but I don't think they do CDs full justice.

[Bernd]

Hi, as the guys said it is done often. One tube pre that is very nice is the Manley Shrimp.
Heard it last week driving a pair of ss Mono amps. Fine sound.
Good Luck with your search.

Peace

Bernd:16:

[Resident Loser]

...hmmm...if you put the tubed gear in early in the game and pass it through a SS amp, you still get the "tube" sound?

It would seem that no specific sound, non-coloration, straight wire with gain, also known as High Fidelity, is the forte' of solid state?

jimHJJ(...is that about right?...)

[JoeE SP9]

...hmmm...if you put the tubed gear in early in the game and pass it through a SS amp, you still get the "tube" sound?

It would seem that no specific sound, non-coloration, straight wire with gain, also known as High Fidelity, is the forte' of solid state?

jimHJJ(...is that about right?...)

Try it. You might like it.:ihih:

[E-Stat]

...hmmm...if you put the tubed gear in early in the game and pass it through a SS amp, you still get the "tube" sound?
Audio systems are cumulative pipelines of multiple gain stages. You don't necessarily have to change all the gain stages in order to hear improvements. Especially for those who listen to vinyl (I think that includes you), using a high quality tube pre for the first 60 to 70 db of gain can do wonders. Like Joe SP-9, I've been using tube Audio Research preamps for twenty five years.

With my vintage system, I got better results when I replaced the SS op amp output from a Pioneer PD-54 CDP with a Manley DAC having a tube line stage that drives the SS Threshold amp directly.

On the other hand, I use the tube (actually hybrid) ARC pre in the main system only when playing vinyl. I see no need to use a 12 db gain stage just to attenuate the signal. With the CDP, I use precision attenuators instead directly to the tube amps.


It would seem that no specific sound, non-coloration, straight wire with gain, also known as High Fidelity, is the forte' of solid state?
With a few notable exceptions, that has certainly NOT been my experience. Most solid state lacks the harmonic richness of the real thing, IMHO.

rw

[Mr Peabody]

JoeE, the PV14ls2 has HT bypass as well as another loop for tape or whatever.

If your just using a DVD for CD playback, you might consider just adding a DAC. The EAD DAC I mentioned I believe was somewhere between $300 to $400.00. Some of the older C-J DAC's can be had for that price range and still sound much better than most players under $1k.

I tried bypassing a preamp one time with a Denon cdp that has a vaiable output going directly input an Adcom power amp, than I inserted the Adcom preamp. I preferred the sound with the preamp. I don't know what made the difference but with the preamp sounded less harsh and more full. Other than that I've just always used a preamp. It's interesting that most integrated amps choose to use a standard preamp section opposed to passive. Although PS Audio has come out with something called a Control Amp. Conrad Johnson has come with a Control amp as well but theirs is $6.5k.

I'm of the opinion that coloration is in the design, whether tube or solid state. I think tubes just give a different presence or feel than solid state, generally speaking.

[Feanor]

...hmmm...if you put the tubed gear in early in the game and pass it through a SS amp, you still get the "tube" sound?

It would seem that no specific sound, non-coloration, straight wire with gain, also known as High Fidelity, is the forte' of solid state?

jimHJJ(...is that about right?...)

My hypothesis is that the tube component produces low order harmonic distortion which (a) is pleasant in its own right and adds "harmonic richness", and (b) hides the high order harmonic distortion created by some s/s amps. For this reason a tube component anywhere in the circuit can produce the "tube sound".

My current monoblocks are a high-bias, low feedback MOSFET design that sound a lot more tube-like than my previous class 'D', Tripath-based amp. Dunno, but I'd take guess that the low-feedback design produces less high-order but possibly more low-order distortion, hence is more tube-like that bi-polar s/s. On the other hand my Tripath amp also had relatively low feedback so who know? :confused:

[E-Stat]

It's interesting that most integrated amps choose to use a standard preamp section opposed to passive.
Most, yes. There is one notable exception, the ASR Emitter II. Not only is the line stage passive, the driver stage is battery powered using 886,000 mf storage. I've heard a pair of them in a very nice system. Using high level sources, I think this is the way the industry is gradually moving. :)

http://www.asraudio.de/produkte/pics/emitter2_b.jpg

http://www.asraudio.de/produkte/pics/emitter2_sk_b.jpg

rw

[basite]

http://www.asraudio.de/produkte/pics/emitter2_sk_b.jpg

rw

that are alot of transistors

[Feanor]

that are alot of transistors

They comprise the 800,000+ uF that E-Stat mentions. :yikes:

[E-Stat]

They comprise the 800,000+ uF that E-Stat mentions. :yikes:
Or half of that. Each amp is a four box setup. One for audio circuitry, one for power supply, and two separate battery boxes connected using huge umbilicals. Here is a decidedly low resolution pic using my camera phone of the two amp flotilla I heard .

rw

[JoeE SP9]

JoeE, the PV14ls2 has HT bypass as well as another loop for tape or whatever.

If your just using a DVD for CD playback, you might consider just adding a DAC. The EAD DAC I mentioned I believe was somewhere between $300 to $400.00. Some of the older C-J DAC's can be had for that price range and still sound much better than most players under $1k.

I tried bypassing a preamp one time with a Denon cdp that has a vaiable output going directly input an Adcom power amp, than I inserted the Adcom preamp. I preferred the sound with the preamp. I don't know what made the difference but with the preamp sounded less harsh and more full. Other than that I've just always used a preamp. It's interesting that most integrated amps choose to use a standard preamp section opposed to passive. Although PS Audio has come out with something called a Control Amp. Conrad Johnson has come with a Control amp as well but theirs is $6.5k.

I'm of the opinion that coloration is in the design, whether tube or solid state. I think tubes just give a different presence or feel than solid state, generally speaking.

There is a synergistic relationship between Adcom preamps and power amps. I've owned several over the years and the preamps always sound better when coupled with an Adcom power amp.
If I can find a used PV14 then the rest of the money I've budgeted can be used for a phono stage. I'll probably build one. Scratch or kit I'm not sure yet. I am certain it will be tubed with enough gain for low output MC cartridges.
Ten years or so back I built "Aunt Corey's passive buffered preamp". My final version had dual transformers, dual power supplies, Shallco ladder attenuator and switching of signal and ground for sources. Although it sounded clean clear and pure it didn't have "tube" magic and I went back to my ARC.
I've already got a DAC. I've been very happy with my MSB. It has been worked a little and sounds fine.
A (tape) loop will not suffice for my purposes. I need a complete bypass of the preamp. The input for the bypass will be the front left /right channels from my surround processor. I don't use a center channel speaker. It's impossible to get a timbre matched center with my current speakers. I've found that phantom mode works adequately. All of my 2 channel sources will be connected to the preamp. CD/DAC, TT, tuner and tape. DVD, HDTV and other surround sources go to the processor.:cool:

[JoeE SP9]

They comprise the 800,000+ uF that E-Stat mentions. :yikes:

Sorry guys, those are electrolytic capacitors. That's were the 800,000+uF is stored.:ihih:

[Mr Peabody]

I see a couple pv14l2 on Audiogon. One is only $1,200.00 which tells me to proceed with much caution, plus they claim the condition is 10. The other one says it's been modded which I would rule out because I'm not a tinker.

[JoeE SP9]

I see a couple pv14l2 on Audiogon. One is only $1,200.00 which tells me to proceed with much caution, plus they claim the condition is 10. The other one says it's been modded which I would rule out because I'm not a tinker.


Thanks, I will investigate.:cool:

[StanleyMuso]

Since my system is used for both audio and visual purposes (ie CDs, tuner and vinyl, plus DVDs, VCR & TV), my thinking was that I would still use the old pre for film viewing and non critical listening, and use a tubed device for more critical listening to the old TT and CD. I'm not technically minded enough to know why, but I remember that vinyl especially sounded richer and somehow more involving when played through a tubed system. Ultimately I'd like to end up with a system which combines the benefits of both SS and tubes. Also, I'm hoping that it would add a little warmth to some classical CDs which seem cold and sterile, although technically good.

[JoeE SP9]

Since my system is used for both audio and visual purposes (ie CDs, tuner and vinyl, plus DVDs, VCR & TV), my thinking was that I would still use the old pre for film viewing and non critical listening, and use a tubed device for more critical listening to the old TT and CD. I'm not technically minded enough to know why, but I remember that vinyl especially sounded richer and somehow more involving when played through a tubed system. Ultimately I'd like to end up with a system which combines the benefits of both SS and tubes. Also, I'm hoping that it would add a little warmth to some classical CDs which seem cold and sterile, although technically good.

It would seem that you and I are looking for the same type of device. A tube preamp with remote control and theater bypass.:cool:

[JoeE SP9]

I should have mentioned I recently replaced my Lexicon CP1 with a Lexicon MC8. The old unit will be residing in my bedroom system. I've got to get some rear speakers before using it.:sad:

This was my first purchase in more than 3 years. It was an unexpected opportunity from a buddie. It's the main reason I'm looking for a new preamp.:cool:

[jrhymeammo]

I have been intrigued by the tube sound for a while (I remember what they sound like from my childhood years), but I only upgraded to a Musical Fidelity amp driven by a Rotel pre-amp a couple of years ago. On the whole, I'm happy with this set up, but for some types of music, ie classical vocal, violin etc, I wonder if I would get a warmer sound if I introduced tubes? I don't have the money to change the whole set up, or to set up an alternative system, but thought I might experiment with a tubed pre-amp just for certain uses.

Has anybody else mated a ss amp with a tube pre-amp? Is this a successful comination?

Thanks.

If you ever consider getting tube gears with 6N6 tubes DONT DO IT.
I say this because 6N6 tubes are extremly hard to find, and there are so many misleading infos on that particular tubes. If you visit such site as Music Direct, Acoustic Sounds, etc. Alot of tube gears are equiped with 6N6s, while none of web retailers sell replacement tubes.
I found this site while back, http://www.watfordvalves.com/product_detail.asp?id=1508

That info was wrong(well in my case anyways). E182CCs are much shorter. After reaplcing 6N6s with E182CCs, my new tubes didnt even lightup or warmed up. They are just not the same I guess. BTW, my NOS Mullards are fine( Iwent to my local tube store and had them checked out).
Just get tube gears that works with 6DJ8s, 12AX7s, 12AU7s, KT88s, 90s that are really easy to find.

PEACE.

[Mr Peabody]

That's something I like about Conrad Johnson, they stock all the tubes used in each piece of gear they sell.

I have to say that I was quite surprised at how much detail my tube equipment has. My power amp uses EL-34's, I've been told that KT88's or 6550's even have better bass control. I have no doubt that there's tube equipment out there that would satisfy all but the hardened solid state lover.

[JoeE SP9]

One of the reasons I've stuck with ARC preamps is they support every piece of equipment they've ever made. You can send one of their earliest pieces back to them and they will fix, repair, overhaul or simply upgrade it. With ARC there is no such thing as it's too old to fix.:)

[JoeE SP9]

If you ever consider getting tube gears with 6N6 tubes DONT DO IT.
I say this because 6N6 tubes are extremly hard to find, and there are so many misleading infos on that particular tubes. If you visit such site as Music Direct, Acoustic Sounds, etc. Alot of tube gears are equiped with 6N6s, while none of web retailers sell replacement tubes.
I found this site while back, http://www.watfordvalves.com/product_detail.asp?id=1508

That info was wrong(well in my case anyways). E182CCs are much shorter. After reaplcing 6N6s with E182CCs, my new tubes didnt even lightup or warmed up. They are just not the same I guess. BTW, my NOS Mullards are fine( Iwent to my local tube store and had them checked out).
Just get tube gears that works with 6DJ8s, 12AX7s, 12AU7s, KT88s, 90s that are really easy to find.

PEACE.

According to the diagrams in my RCA tube manual E182CC is a replacement for a 6199. 6N6's and E182CC's are not interchangable.

[Bernd]

If you ever consider getting tube gears with 6N6 tubes DONT DO IT.
I say this because 6N6 tubes are extremly hard to find, and there are so many misleading infos on that particular tubes. If you visit such site as Music Direct, Acoustic Sounds, etc. Alot of tube gears are equiped with 6N6s, while none of web retailers sell replacement tubes.
I found this site while back, http://www.watfordvalves.com/product_detail.asp?id=1508

That info was wrong(well in my case anyways). E182CCs are much shorter. After reaplcing 6N6s with E182CCs, my new tubes didnt even lightup or warmed up. They are just not the same I guess. BTW, my NOS Mullards are fine( Iwent to my local tube store and had them checked out).
Just get tube gears that works with 6DJ8s, 12AX7s, 12AU7s, KT88s, 90s that are really easy to find.

PEACE.

Good advice about the 6N6. It can be sourced from China, but it's a pain in the rear. Above all it's not that good of a tube anyway.
And yes there is some misleading info on that tube.

Peace

Bernd:16:

[JoeE SP9]

Good advice about the 6N6. It can be sourced from China, but it's a pain in the rear. Above all it's not that good of a tube anyway.
And yes there is some misleading info on that tube.

Peace

Bernd:16:


Whoever or whatever told him you could replace a 6N6 with a E182CC is someone or somewhere all of us need to stay away from.:ihih:

[Bernd]

Whoever or whatever told him you could replace a 6N6 with a E182CC is someone or somewhere all of us need to stay away from.:ihih:

That would be me.:( Talk about egg on face. I phoned the guy from Watford Valves and I wrote exactly what he said. Well will not be dealing with him again. Lesson learned, don't believe anything you hear and only half of what you see. Apologies all round.

Peace

Bernd:16:

[E-Stat]

One of the reasons I've stuck with ARC preamps is they support every piece of equipment they've ever made. You can send one of their earliest pieces back to them and they will fix, repair, overhaul or simply upgrade it. With ARC there is no such thing as it's too old to fix.:)
ARC is currently highlighting the "C" update to the early 70s icon, the SP-3.

SP-3 (http://www.audioresearch.com/SP3-update.html)

If you were so inclined, my guess is that you could still get the MKIII update or the remote gain control for your 9.

rw

[jrhymeammo]

http://thetubestore.com/ru-6h6p.html
I just ordered some. They should work, but who knows.. If they do, then here is what I think. Since availability of these tubes are so scarce, people are keeping their mouth shut. After all, we all gotta lookout for ourselves first.
I'll post an update one I get them going.

PEACE.

[JoeE SP9]

ARC is currently highlighting the "C" update to the early 70s icon, the SP-3.

SP-3 (http://www.audioresearch.com/SP3-update.html)

If you were so inclined, my guess is that you could still get the MKIII update or the remote gain control for your 9.

rw I've been thinking about the update for my SP-9. It will have to wait until I get my new preamp. I kick myself frequently for getting rid of my SP-3. It was the first piece of ARC gear I ever bought. Selling it was one of the dumber things I've done. That's why I'm not selling my SP-9.:cool:

[jrhymeammo]

Hey Bernd. how about these for you? http://www.audiotriodes.com/en/shop/flypage/product/253.html

[Bernd]

Thanks for the tip, but I don't use 6N6 tubes. I will keep this one in mind though in case the question comes up again.
And you're right we need to share info like this one.
Hope the new ones you've ordered work for you.

Peace

Bernd:16:

[jrhymeammo]

http://thetubestore.com/ru-6h6p.html
I just ordered some. They should work, but who knows.. If they do, then here is what I think. Since availability of these tubes are so scarce, people are keeping their mouth shut. After all, we all gotta lookout for ourselves first.
I'll post an update one I get them going.

PEACE.

Nope, they do not work. In last 2 weeks, I've invested over 100 bucks on tube. Man, hope they'll take them back. They better.

[WILLIAM C WALDECKER 3RD]

I have been intrigued by the tube sound for a while (I remember what they sound like from my childhood years), but I only upgraded to a Musical Fidelity amp driven by a Rotel pre-amp a couple of years ago. On the whole, I'm happy with this set up, but for some types of music, ie classical vocal, violin etc, I wonder if I would get a warmer sound if I introduced tubes? I don't have the money to change the whole set up, or to set up an alternative system, but thought I might experiment with a tubed pre-amp just for certain uses.

Has anybody else mated a ss amp with a tube pre-amp? Is this a successful comination?

Thanks.Hey Stanley, i am currently using a Balanced AudioTechnology VK 3i tube preamplifier with a pair of Odyssey mono extreme SE monoblock power amps that are solid state and in my opinion the combination offers the best of both Worlds. thanks....WCW III

[StanleyMuso]

This has certainly turned into a very interesting discussion, and certainly encourages me to try it out.

How complicated is it to keep things balanced? Someone told me it keeps constant fiddling to keep tubed amps running properly because tubes don't wear out at the same rate. Is this true?

And it certainly appears that it is hard to find replacement tubes at times.

Sorry to be such an ignorumus, but one more question. What sort of life expectancy can I expect from a set of tubes?

[Bernd]

This has certainly turned into a very interesting discussion, and certainly encourages me to try it out.

How complicated is it to keep things balanced? Someone told me it keeps constant fiddling to keep tubed amps running properly because tubes don't wear out at the same rate. Is this true?

And it certainly appears that it is hard to find replacement tubes at times.

Sorry to be such an ignorumus, but one more question. What sort of life expectancy can I expect from a set of tubes?

Good on you.
The signal tubes in a pre-amp (if not the obscure type) are plentyful and easy to source. As for fidling with tubes your someone most likely talked about power tubes. Different to the small signal tubes in a pre.
Life expectancy depends on many things. New stock I would say anything up to 2000 hours. Often much longer. NOS (new old stock) between 2000 and 10000 hours. Harder to find, but often sound nicer.
Good luck and welcome to the warm glow.

Peace

Bernd:9:

[Mr Peabody]

I haven't had my gear long enough to be sure about the balance question but it sounds like bunk to me. A light bulb stays lit until it goes out. I personally plan to replace all the output tubes if one goes out because they went in at the same time. This would seem to limited any imbalance problems as well. If you stick with a known manufacturer who stocks the tubes you shouldn't have any problem finding them. I'm not sure on single ended tubes but my manual estimated 5000 hours or so on tubes. If you buy ARC or BAT which uses the Russian 6922, they are said to last about 10,000 hours. If that tube is the reason the new ARC gear sounds like it does, I'd avoid it like the plague.

[E-Stat]

If you buy ARC or BAT which uses the Russian 6922, they are said to last about 10,000 hours. If that tube is the reason the new ARC gear sounds like it does, I'd avoid it like the plague.
I think you are referring to the 6H30 tube, not the venerable 6922.

rw

[Mr Peabody]

E-stat, you are correct sir, thanks for pointing that out. I double checked the BAT and ARC preamps use the 6H30. This is the one called the "super" tube. I haven't heard any BAT but the ARC preamp I auditioned I would not keep as a gift.

[JoeE SP9]

E-stat, you are correct sir, thanks for pointing that out. I double checked the BAT and ARC preamps use the 6H30. This is the one called the "super" tube. I haven't heard any BAT but the ARC preamp I auditioned I would not keep as a gift.

What was the model number of the ARC you didn't like? Just curious. If it was one of their SS models I can understand.:idea:

[Mr Peabody]

The ARC preamp I listened to was the LS17. I brought it home with their 150 wpc solid state amp, I forgot the model, it was the digital switching amp. The sales guy actual let me try his out. He uses it with a SP-9.

[E-Stat]

The ARC preamp I listened to was the LS17. I brought it home with their 150 wpc solid state amp, I forgot the model, it was the digital switching amp. The sales guy actual let me try his out. He uses it with a SP-9.
Did you happen to listen to the LS-17 with your C-J amps?

rw

[Mr Peabody]

No, I only listened with the ARC power amp. My disappointment with the ARC kept me searching for tube gear which eventually led me to C-J, and after that I stopped looking. I really find the C-J musically satisfying.

[E-Stat]

No, I only listened with the ARC power amp. My disappointment with the ARC kept me searching for tube gear which eventually led me to C-J, and after that I stopped looking. I really find the C-J musically satisfying.
Perhaps what you didn't like about the ARC stuff was the SS switching amp, not the tube line stage.

rw

[Mr Peabody]

Possible, but I have my doubts. I also listened to their integrated and a few other pieces, not at home, and some of the same characteristics existed. The sales guy uses the SP-9 and the solid state amp, I was going on his recs and what I could possibley afford. The ARC sound gives me the impression of gray and industrial. I've heard older ARC that didn't give me that impression. I know ARC has a good rep, it would be interesting to see what their fan base thought of the new sound. Have any of you had the chance to hear either of these pieces?

[E-Stat]

Possible, buI've heard older ARC that didn't give me that impression. I know ARC has a good rep, it would be interesting to see what their fan base thought of the new sound. Have any of you had the chance to hear either of these pieces?
Actually, the SP-6C preamp from 1981 was the first model to crossover to the "yang" side as HP would say. I bought one having heard his SP-6B originally. It was a tad on the lean and cool side. The later SP-6E, SP-8, and SP-10 models "fixed" that. The first SP-9 was likewise a cool character. I had an SP-9MKII and had the factory update it to the MKIII which added some apparent lower midrange output or warmth along with a bit more resolution.

FYI, all of C-J's new designs also use the 6H30 tube. Starting with the flagship ACT2 and including various models of the CT (composite triode) family.

rw

[Feanor]

Perhaps Geoffcin would back me up on this. Anyway, I'm getting on very well with my Adcom GFP-750 used in passive mode in combination with a pair of Monarchy SM-70 Pro's.

The viability of a passive preamp / power amp comb depends on the preamp output power amp input impedances -- or so I' given to believe. Short interconnects are desireable, though in my case I'm using 6 foot, balanced interconnects with no problems I can hear. (The Monarchys used as monoblocks prefer balanced inputs for optimal operation; there again I can't say I understand the techincal explaination).

How other than the impedance thing, my question is: how could a tube preamp be better than "no" preamp? My pet theory is that tubes added enough pleasant, low-order harmonic distortion to mask the unpleasant, high-order harmonic distortion that S/S cause, especially those that use a lot of feedback. This means that the tubes are actually adding distortion to produce their euphonic effect.

[E-Stat]

The viability of a passive preamp / power amp comb depends on the preamp output power amp input impedances
This is the first of three factors that determines compatibility. Low output impedance of the source is also desirable to provide a suitable input to output multiple. See attached link for calculator to determine potential HF rolloff.

DACT calculator (http://dact.com/html/ac_calculator.html)


Short interconnects are desireable, though in my case I'm using 6 foot, balanced interconnects with no problems I can hear.
Balanced or not, the second factor is cable capacitance. The lower the better.


How other than the impedance thing, my question is: how could a tube preamp be better than "no" preamp?
The final factor is gain. Some folks say they lose dynamic "punch" with passives. I think they simply don't have enough gain. My CDP has a 4 volt output driving 1.3 volt sensitivity amps. I can clip them at will.

rw

[Feanor]

This is the first of three factors that determines compatibility. Low output impedance of the source is also desirable to provide a suitable input to output multiple. See attached link for calculator to determine potential HF rolloff.

DACT calculator (http://dact.com/html/ac_calculator.html)

Balanced or not, the second factor is cable capacitance. The lower the better.

The final factor is gain. Some folks say they lose dynamic "punch" with passives. I think they simply don't have enough gain. My CDP has a 4 volt output driving 1.3 volt sensitivity amps. I can clip them at will.

rw

Perhaps I'll try some of the math sometime. I do know that the Monarchys' input impedance is supposed to be a good match for passive preamps but I can't quote the spec offhand.

I find the "punch" of the Monarchys at least as good as their predeceasor, a Bel Canto eVo. And I never use a volume knob setting higher than 3 o'clock, necessarily less than unity gain. As for HF roll-off, maybe I just don't hear it as I'm deaf much above 10kHz.

[E-Stat]

Perhaps I'll try some of the math sometime.
All the calculator needs to display response curves is:

1. Amp input impedance (kohm)
2. Cable capacitance (pf)
3. Attenuator resistance (kohm)

edit: Unless I'm playing a particularly low level recording like a Telarc, I usually get full output at around -12 db.

rw

[Feanor]

All the calculator needs to display response curves is:

1. Amp input impedance (kohm)
2. Cable capacitance (pf)
3. Attenuator resistance (kohm)

edit: Unless I'm playing a particularly low level recording like a Telarc, I usually get full output at around -12 db.

rw

So ...

Monarchy SM-70 Pro amp input impedance is 100kOhms;
Blue Jeans balanced cables are 13pF/foot, hence 78pF for 6 foot
Attenuator resistance is -- what? my Adcom GFP-750's output impedance, presumably at 0 dB attenuation, is 1.2kOhms, which is much lower than the calculatior allows.It would seem there is essentially zero attenuation any where in the audible range. Right?? :confused:

[E-Stat]

It would seem there is essentially zero attenuation any where in the audible range. Right?? :confused:
I would say so. What is the output impedance / gain of your source(s)?

rw

[Feanor]

I would say so. What is the output impedance / gain of your source(s)?

rw

My Sony SCD-CE775 says 2 Vrms and >10kOhms;
My M-Audio Audiophile USB say +2dbV, no o/p impedance specified.

I'm curious as the "Vrms" as opposed to "+dbV". (I don't understand these things :( )

[E-Stat]

My Sony SCD-CE775 says 2 Vrms and >10kOhms
The output is quite common, but the impedance is not. Perhaps what you are looking at is the intended input impedance of what is driven. The output of my Pioneer PD-54 is 600 ohms (another typical answer) while the GamuT CD-1 is 75 ohms.


My M-Audio Audiophile USB say +2dbV, no o/p impedance specified. I'm curious as the "Vrms" as opposed to "+dbV".
That works out to something like 1.25 volts. Here is a conversion tool (http://www.sengpielaudio.com/calculator-db-volt.htm)

rw

[Feanor]

The output is quite common, but the impedance is not. Perhaps what you are looking at is the intended input impedance of what is driven. The output of my Pioneer PD-54 is 600 ohms (another typical answer) while the GamuT CD-1 is 75 ohms.

That works out to something like 1.25 volts. Here is a conversion tool (http://www.sengpielaudio.com/calculator-db-volt.htm)

rw

Interesting. Perhaps your right about my CDP but the specs weren't any more specific.

Anyway, I have no beefs using my Adcom in passive mode. :cornut:

[StanleyMuso]

Ealier I asked a questiion about the need for constant fiddling that I was warned about by somebody to keep an amp at its optimum. I have been doing some research, and apparantly that "fiddling" my informant was refering to is called biasing. I was told I would need to get a voltmeter and some insulated screw drivers to carry out this "biasing". He says he does it about every three months, but that people who are really anal do it on a weekly basis. I was not able to get more info from him - another customer came in and he was being impatient with me in the first place, as if I was a moron asking obvious questions. Don't want to go back to him afer that, and I certainl won't be buying anything from him!!!

So, could I impose on your generosity once more? Could someone explain in layman terms what on earth is biasing, and is it a very onorous? I'm used to ss equipment which doesn't need constant tuning to keep it at its peak. Please bear in mind I am not a technical person, so would I be able to carry out biasing myself, or would I have the constant expense of getting somebody else do it for me?

Once again, thank you all for a very interesting discussion.

[Dusty Chalk]

Basically: tubes are complicated. Each one is individual, and you're setting one of the middle voltages (that setting will be different for every tube). So you need to know what your "bias voltage" is, set the voltmeter on the bias points, and then change the bias (usually entails turning an inset screw -- you'll need to know where that is, too) until the voltmeter reads what it should.

There's usually several per amp -- one per tube.

And it needs to be done while the amp is on, hence the need for insulated screwdrivers. And with no music playing.

Oh, and: he's high -- you don't need to set your bias every three months. You need to set it once when you get it. I'd check it again in a month, and if it needs changing, then check it again a month after that. When you check it and it doesn't need changing, then it's settled down, and then I'd only check it every 6 months to a year after that. Then you only need to check/change it again if (a) you move the amp (new voltage), or (b) you install new tubes.

And there are some amps that are auto-biasing. You never need to do those. I used to have one of those. I miss it.

[Mr Peabody]

First of all you are talking about buying a preamp, to my knowledge there is no preamp that needs biasing, that is a power amp adjustment only. And only the output tubes. Biasing is irrelevant to what you want to do.

If you ever think of buying a tube power amp, biasing is not a big deal if you buy the right equipment. Either entry level integrated or very expensive tube amps can be found with auto-bias where you have no worry. Conrad Johnson has a built in LED for each bias adjustment. No meter needed. You just turn the screw until the light comes on then slowly back it off until the light goes out and you are done. Actually, from my manual and every dealer I've spoken to biasing only has to be done when you initially set the power amp up and if you move it or do anything to effect the electric going into the amp and, of course, when you replace one of the tubes. My power amps are now at the factory being converted and I will double check how frequently they recommend checking the bias.

I am not a tinker either so when I was looking for a tube amp easy biasing was one of the criteria I kept in mind. I did not like the idea of using a voltmeter. Off the top of my head I can't remember who but other manufacturers offer easy bias adjustments as well. Don't sweat it.

[StanleyMuso]

I really appreciate it.

Obviously I got myself confused, and started seeing complications where they don't exist. I guess the salesman didn't realise I wanted to know about pre-amps and not amps, and I didn't realise that he was talking about power amps. That's the trouble when you first start investigating something new - you don't know what you don't know, and don't know what questions to ask. I have since found some on-line info and I'm beginning to gain some understanding. I'm going to see if I can find a decent book or two on the subject and do some reading up.

Once again, thank you for the input. It encourages me to explore further.

[Mr Peabody]

I talked with one of the guys from C-J today and asked about how frequent to bias a power amp tube, he said probably once a year is fine or every 3 months or so if you are OCD. The impression I get from talking to different people the more frequent check may be necessary, or recommended, as the tubes get older.

It also seems that tubes don't necessarily wear at the same speed. Not long ago I posted some where on here that I planned to switch all the output tubes when one goes bad but I've since changed that plan and will just change them as they go out.

Stan I think the type of info you are looking for will be difficult to find in a book. If you do find one, let me know too. You are fine doing what you are doing. Don't let one jerk sales person prevent you from asking questions. Have you any brands in mind to investigate yet?

[StanleyMuso]

Have you any brands in mind to investigate yet?

No, not yet. I'm right at the beginning of my exploration stage, and don't really know the pros and cons of various models out there. I notice that Chinese manufactured units seem reasonably priced, but I have no idea about their quality.

In addition, my thinking is evolving on the matter. I will start with a pre mated to my Musical Fidelity, and perhaps if I like it, eventually go the whole hog and get a power amp as well. In that case I would run the tubed equipment for vinyl and CD stereo only, and dedicate all the solid state stuff to home theatre and surround. However, all this is in the future, as I am low on funds at the moment, and my knowledge base is still not where I would be comfortable to make such a plunge. I am cautious by nature.

[Mr Peabody]

I understand you being cautious, you want to be sure you are making the right move for you. Going with a tube preamp will be a safe start.