Folks,
I've started my Pass Labs journey with the purchase of a X150.8 power amp earlier this month. The reason for this post is that I've had a BAT system comprised of a VK-55SE tube amp and a VK-80 tube preamp. It was a great system-open rich holographic. Fast forwarding I still have the tube preamp which is driving the X150.8 (driving Zu Def. 3 speakers). However, presentation seems veiled, loss of texture, detail of instruments and voice, and note decay. What it does bring over the old system is rock solid expanded space (wide and deep) and much better localization than previous set-up. Per a friend's advice who owns a X350.8 mated with a XP-22, I was advised to let it break-in a week or two. At this point not much of an improvement.
So the ultimate question is it a break-in issue, component mismatch, or some other issue that may be causing the issue? My earlier research based on impedances pushed me towards "no issues" since the X150.8 has 100k input impedance, while the preamp is at 300 ohms.
My ultimate objective is to have an entire Pass system to replace my original tube system (having equal or better SQ). However, I was hoping that would be later than sooner due to the investment just made. Anyway, just doing a sanity check.
Many thanks.
Neil
I've started my Pass Labs journey with the purchase of a X150.8 power amp earlier this month. The reason for this post is that I've had a BAT system comprised of a VK-55SE tube amp and a VK-80 tube preamp. It was a great system-open rich holographic. Fast forwarding I still have the tube preamp which is driving the X150.8 (driving Zu Def. 3 speakers). However, presentation seems veiled, loss of texture, detail of instruments and voice, and note decay. What it does bring over the old system is rock solid expanded space (wide and deep) and much better localization than previous set-up. Per a friend's advice who owns a X350.8 mated with a XP-22, I was advised to let it break-in a week or two. At this point not much of an improvement.
So the ultimate question is it a break-in issue, component mismatch, or some other issue that may be causing the issue? My earlier research based on impedances pushed me towards "no issues" since the X150.8 has 100k input impedance, while the preamp is at 300 ohms.
My ultimate objective is to have an entire Pass system to replace my original tube system (having equal or better SQ). However, I was hoping that would be later than sooner due to the investment just made. Anyway, just doing a sanity check.
Many thanks.
Neil
I would break it in for a month or two, depending on how much you use it, and reevaluate.
Likely there will be a slow, gradual improvement over a period of time, rather than sudden.
That said, equipment will sound different, regardless of some claims, so you have the final say.
If you still have the VK-55SE, you may want to keep it until after making a final decision.
The two amplifiers will interact with various speakers in rather different ways.
Likely there will be a slow, gradual improvement over a period of time, rather than sudden.
That said, equipment will sound different, regardless of some claims, so you have the final say.
If you still have the VK-55SE, you may want to keep it until after making a final decision.
The two amplifiers will interact with various speakers in rather different ways.
Rayma,
Many thanks for the input. The original intent was to get rid of the heat and tube maintenance, so the VK-55SE is gone (part of a trade-in). The dealer claimed that issue was most likely due to brand incompatibility (although doesn't technically answer the question). My wife who also noticed the sound issues which included veiling and loss of emotional impact of some of her favorite songs. What I did do was to take the preamp out and plug DAC with integrated volume control. This did improve the system greatly. Almost close to what I had before with clearer presentation, deep and clearer lower registers. More dynamic with the added bonus of enveloping presentations.
Many thanks for the input. The original intent was to get rid of the heat and tube maintenance, so the VK-55SE is gone (part of a trade-in). The dealer claimed that issue was most likely due to brand incompatibility (although doesn't technically answer the question). My wife who also noticed the sound issues which included veiling and loss of emotional impact of some of her favorite songs. What I did do was to take the preamp out and plug DAC with integrated volume control. This did improve the system greatly. Almost close to what I had before with clearer presentation, deep and clearer lower registers. More dynamic with the added bonus of enveloping presentations.
That's encouraging. What other sources do you use?
I would be very cautious about buying a new preamp.
They will vary in sound as much as, or even more than, power amps.
If you don't use LPs, you might prefer a passive volume control and input selector.
I would be very cautious about buying a new preamp.
They will vary in sound as much as, or even more than, power amps.
If you don't use LPs, you might prefer a passive volume control and input selector.
How do the distortion profiles of the two amps compare?
Also, tubes in front of tubes in many cases can be a distortion sandwich, so the jump to any ss amp or product is going to be quite a change.
Also, tubes in front of tubes in many cases can be a distortion sandwich, so the jump to any ss amp or product is going to be quite a change.
you had one set of THD Spectra with your previous system, and now have another, presumably much lower THD than with BAT amp
thought is that you prefer more Sugar - be it 2nd dominant or simply more THD, whatever dominant is
now, if preamp in case is having fixed 18db gain ( as written on site), you simply have too much signal conditioning now, combined with PL amp - severely attenuating after selector, then needlessly amplification after ......... whatever fancyshmanzy circuitry applied, too much fiddling with signal always results in signal energy loss
that's explanation why you're finding direct DAC connection better to your ears
as said many times before - if speaking about preamp as separate item, single pot ("passive pre") is enormously useful as reference - you have loss generally in highs and bass but almost unspoiled clarity of mids
comparatively, proper preamp will have some loss in mid quality but will gain in bass and highs, bringing overal sound quality increase
if you hear too much loss with preamp comparing to "passive pre", or even simpler - comparing to direct connection of source having own volume control - preamp is not good ( enough)
anyhow - if you have just DAC as source, do not bother with preamp at all
even if I'm sure that proper preamp is bringing benefits even for juice sources connected directly to amp
useful reading : https://www.diyaudio.com/community/threads/what-is-gain-structure.186018/
I currently use a Topping D90LE DAC with an IFi Zen streamer, and the CD player is an Oppo BDP-95. My plan was to have an entire solid state set up which included a Pass preamp (either XP-12 or XP-22) with the new Pass amp I purchased.
I agree with you that I need to hear what another preamp would sound in the current system. The dealer did say they would loan out either of the preamps I mentioned. With that being said, the Topping set up sounds extremely good, although my wife still isn't satisfied regarding her favorite songs🙂
Zen - Many thanks for your detailed input and link. So boiling down your explanation:
- I've been accustom to tube distortion (which other posters indicated as well) due to tube preamp (gain=18 dB) and push/pull amp (gain=25 dB) which included vocal texturing and holographic pleasing presentation.
- adding X150.8 (gain=26 dB) lowered distortion, masking less and now shifting focus to preamp.
- Even though preamp still has "pleasing" second order distortion, the audio chain consisting of preamp volume control, preamp(G=18) and amp(G=26) are increasing distortion (presumably more from tube preamp), dropping SNR.
- Having a DAC (volume control enabled as opposed to DAC only mode), with much lower THD of preamp, directly connected to X150.8 increases SNR, enhancing lower registers, presentation, etc.
So looking at a Pass XP-12 (gain = 9.3 dB) with much lower distortion would obviously be a better fit. Or the bigger question, to your point, do I need a preamp at this point. I was planning on completing the system with all Pass.
Even though presentation has improved with Pass/DAC combo, my wife feels the vocal emotional impact she experienced with some of her favorite tracks (i.e. Over the rainbow by Israel "IZ" K). I agree that even though all tubes are out of the system, there is a bit of that mid vocal instrument texturing missing. I'm sure once I get a chance to demo a Pass pre in the system, I should get absolute clarity. Although I did want to get to a point where my wife and I could share our listening experiences together again🙂
Neil
in short - with excessive gain sum (existing preamp), you're "killing" the signal (whichever resulting THD Spectra), that's the main reason why direct DAC connection is sounding superior
having opportunity to try PL preamp, that's no brainer - try and decide do you need more Sugar*** (usually dominant 2nd) but whichever preamp you end with, take care of choosing one with adequate (minimal) gain
*** with PL gear you'll end up with low level THD; do you prefer higher levels, only you can decide; not matter of quality of chosen gear per se, it's matter of personal taste
clever
Rich Pa, happy Pa, happy Greedy Boyz
having opportunity to try PL preamp, that's no brainer - try and decide do you need more Sugar*** (usually dominant 2nd) but whichever preamp you end with, take care of choosing one with adequate (minimal) gain
*** with PL gear you'll end up with low level THD; do you prefer higher levels, only you can decide; not matter of quality of chosen gear per se, it's matter of personal taste
clever
Rich Pa, happy Pa, happy Greedy Boyz
another example of bad manufacturer's choices, not exactly having client's best in mind; in which scenario - with nowadays sources ( most having 2Vrms output) these two are clever to combine?
practically - all you were doing in preamp is attenuating signal to hell, then amplifying it sky high ......... while all the time needing just buffer stage (gain 0db) with decent attenuator
18db preamp gain is (almost) exactly right to combine with power buffer ( amp without voltage gain; say FW F4)
edit: VK55SE is having 25db gain, for 55W output
meaning 20.98Vrms at output, divided with 17.88V/V (25db gain), calls for 1.18Vrms at input
that's full blast
1.18Vrms to 2Vrms ( nowadays sources) means -4.58db
say that - realistically - you need these 4.58db as margin/reserve specifically for recordings of lower max. level ........... when combined with 18db preamp - you simply have 18db of gain too much
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believe it or not - clever move ....... nice to have it for 3-5yrs of moderate use ..... after that, all possible horrors, due to routing/layout problems (currents/heat)
one 6C33C is taking 3A3@12V for heating; there are 4 of them, heaters fed through pcb traces ........... go figure!
edit: pic taken on my bench
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I don’t know how accurate the efficiency ratings of Zu speakers are ( overstating seems common, eg Klipsch ), but with that said they probably still don’t need a lot of wattage to reach ear splitting levels.
Said another way: I currently have 20db of gain in my setup, driving 90db speakers - and it’s more than enough to reach irresponsible levels in a fairly large space ( 1000ish sq ft ).
This setup was the result of listening to ZM on the topic of gain. It took a while to absorb that lesson however; I had to listen better for better listening.
😉
Said another way: I currently have 20db of gain in my setup, driving 90db speakers - and it’s more than enough to reach irresponsible levels in a fairly large space ( 1000ish sq ft ).
This setup was the result of listening to ZM on the topic of gain. It took a while to absorb that lesson however; I had to listen better for better listening.
😉
Try one of Pa's suggestions: Put a scope at speaker terminals to get a sense of actual voltage swing. Then translate that to watts assuming worst case impedance guess. You will likely not see as much as 5W, even with not-so-efficient speakers.
(EDIT: First make sure you can earth ground the - terminal, or use isolated (eg, battery powered) 'scope!)
(EDIT: First make sure you can earth ground the - terminal, or use isolated (eg, battery powered) 'scope!)
Maybe the XA 30.8 or maybe even the sit4 would be more to your liking.
The pass amps have a good amount of gain.
The pass amps have a good amount of gain.
If SS amps could do all that tube amps can, who would be using tubes? Masochists only?
Nearly everything in this hobby is a tradeoff. Depending on your taste and preferred musical genres different sets of compromises may work best.
Moving to a SS preamp may bring even more disappointment in the particular areas you mention while bringing improvement in others. What matters most to you?
With speakers like yours i would be more inclined to examine DHT SETs in conjunction with a DHT preamp.
Many thanks folks, for all your input. The Pass and DAC set up (without tube preamplifier) has cleared up most of the issues. A friend of mine has a XPass amp and a XP-22 setup which I've listened to for a few years. So I have an idea how good the Pass systems should sound. Once I get a preamp to replace the DAC's digital volume control, I'll report out my progress.
Thanks agin for all your time and consideration.
Thanks agin for all your time and consideration.
Rayma - Any particular passive volume controllers come to mind? Anything that has a balanced configuration?
passive is for sissies
Sissies are using not so passive - don't look further than Iron Pre, be it SE or Bal
Sissies are using not so passive - don't look further than Iron Pre, be it SE or Bal