Got a Chinese tube amp and now world is upside down

[bethslave]

First, you should not worry (nor express any emotion, one way or the other) about what 'non-tube' people think. Don't rely upon others to justify what you consider 'OK behavior' (or thoughts). At least within the realm of hobbies, which is pretty trivial in the scheme of things. I mean, it's not like we're talking morality, for crying out loud.

No, not worried at all. Sorry if I gave that impression and actually meant a bit of support to the OP. I'm just thankful for some peaceful enjoyment and discussion!

 

[svtcontour]

Question for the OP. Are you still enjoying the amp? I've had a similar experience and now long term relationship with a Gemtune PA1501 which I bought based on this review:

Reviewing the Gemtune APPJ PA1501A 6AD10 Stereo Tube Amplifier

I recently picked up an interesting little tube amp via a group buy on Massdrop, the Gemtune APPJ PA1501A stereo tube amplifier. Try saying that three times fast! It’s a cute little single-en…

retrovoltage.com

I purchased it just for fun in 2019 specifically for near-field desktop use and wound up liking it a lot. I wasn't too concerned about power or distortion, I just wanted general competence in electrical design, frequency response and noise floor. It's a surprisingly good match for my Advent Baby II speakers which are rated at 89 dB at 1W/1m. I dusted off an old Fisher 10 band graphic EQ to boost the bass and use my PC as my music source with Tidal or Radio Paradise. The system sounds much better than it logically should and passing time doesn't seem to change that. It gets as loud as is polite in an office setting. Tube life doesn't seem to be a concern. One that it shipped with was a little microphonic so I purchased a pair of cheap NIB Sylvania replacements that have now been in use since 2019. Subjectively I prefer my desktop system to my main system for several 1950's recordings such as 'Cast Your Fate To The Wind' by Vince Guaraldi, 'Take 5' by Dave Brubeck and several Miles Davis tracks. That's fairly consistent with what others have already posted here.

Reading through this thread I'm glad the non-tube people understand that it's okay to experiment and just have some fun sometimes!

Sorry for the late reply and I absolutely am still in love with it. It will have to be pried out of my dead cold hands

 

[egellings]

Possibly there is some frequency response coloration there and it is agreeable. On a different pair of speakers the sound from it would be different again but we don't know if it would be agreeable or not.

Agree. The output Zo of the amp and that of the speaker form a voltage divider. The Zo of the amp is very likely mostly resistive in most cases, while the speaker's is likely to be more complex. As a result, the output voltage across the speaker terminals of the tube amp will get modulated by the speaker's Zo as it changes over frequency. Different speaker, different modulation of the tube amp's output voltage, different sound. Hopefully, the sound is euphonic.

 

[mhardy6647]

Agree. The output Zo of the amp and that of the speaker form a voltage divider. The Zo of the amp is very likely mostly resistive in most cases, while the speaker's is likely to be more complex. As a result, the output voltage across the speaker terminals of the tube amp will get modulated by the speaker's Zo as it changes over frequency. Different speaker, different modulation of the tube amp's output voltage, different sound. Hopefully, the sound is euphonic.

Some call this: synergy.

 

[egellings]

Some call this: synergy.

That's true if the combination works out well. It can go sour, too.

 

[Chr1]

Enjoy. And just ignore the tube haters. If you need more power or want better bass, just add subs.
Fact is they sound better than SS when clipping anyway.

 

[antcollinet]

So out of curiosity, I picked up a cheap tube amp from Aliexpress - branded as OldChen. Its an EL34 single ended. I figured for the dirt low price of about $330 (canadian money) including shipping, I can mess around with it and see what I think. I was prepared to hate this thing because I've always had solid state and hate mushy bass, softness and lack of detail.

My speakers are open baffle DIY and fairly efficient. I am guessing at around 95db @ 1w or higher like even 97. I also dont listen very loudly. Typically low 80's on the peaks .. maybe mid 80's. Occasionally tapping 90db on peaks if I'm feeling very crazy LOL.

Anyway connected this, and let it warm up for 20 mins. Then sat down and started listening to music and I'm just shocked. Subjectively, I find it neutral with no apparent "tube sound", bass is nice and firm and its plenty clear and resolving and for whatever reason, I'm hearing more subtleties. When I go back to my solid state, they are there, but just ever so slightly more subdued.

Subjectively, its better on anything that has vocals and real instruments or anything recorded in a live open space. The solid state is still better for pure electronic or dance /EDM if very loud volumes are needed. So at this point, I am finding it hard to go back to the solid state. I invited a couple friends over who are solid state guys and now they are tempted to buy the same little amp because they agreed, it sounds better and more involving.

So ... is it the fact there is even order harmonics? Is there any benefit of pure class A of a single ended. Trying to understand why I'm listening to music for hours a night instead of sleeping since getting this thing. Make it stop LOL.

Quite possibly since you are listening differently (you are in evaluation mode) you are noticing stuff you don't normally. This is common.

Or it could be level mismatch (how are you level matching?

Or frequency response variation caused by the high output impedance from the transformers interacting with your speaker impedance.

Alternatively it could be common-or-garden cognitive bias.


EDIT - just noticed this is an aging post - probably all these possibilities plus more have already been discussed. Sorry.

 

[egellings]

Enjoy. And just ignore the tube haters. If you need more power or want better bass, just add subs.
Fact is they sound better than SS when clipping anyway.

If the amplifier is used for home music playback rather than as a musical instrument amplifier, then you would not want to play so loudly that either type of amplifier, tube or S.S., would be driven into clipping. If that happens, then a more powerful amplifier is needed. For MI applications, then I could see where the tube type might work better in an overloaded situation, since it would be considered a desired sound effect.

 

[mhardy6647]

That's true if the combination works out well. It can go sour, too.

Synergy is a vector quantity.

So is "burn in" -- but don't tell the cable acolytes.

 

[Chr1]

And a top tune by The Police.

If you are dyslexic.

Or is it Synchronised... Whatever, my favourite is "Voices Inside My Head" .

(And no, I ain't schizophrenic.
Much. Or so I tell myself.)

Ahem.

 

[mhardy6647]

(And no, I ain't schizophrenic.
Much. Or so I tell myself.)

... but we digress.

 

[welwynnick]

And a top tune by The Police.
If you are dyslexic.
Or is it Synchronised... Whatever, my favourite is "Voices Inside My Head" .
(And no, I ain't schizophrenic.
Much. Or so I tell myself.)
Ahem.

Synchronicity!
I'm afraid I remember when it was released. Happy days.

 

[Chr1]

Aye, me too... Remember buying all their early singles (in various colours of vinyl.)
Roxanne, Can't Stand Losing You etc...

The post-punk/new wave days were great for interesting gatefold sleeves and weird coloured singles.

 

[boxerfan88]

Ya I do have a Dayton USB mic and I should really do a measurement at 1 meter from the loudspeaker as well as listening position to see how it compares with the solid state. With my Solid state (Ramsa amp), this was the response of the speaker at 1 meter. Its not ruler flat but I think not too bad for DIY and being open baffle. Maybe this weekend I'll do it again with the tube amp. Good idea. View attachment 316491

Just wondering…did you manage to measure both tube & SS for comparison? I browsed through the thread and couldn’t find it…

 

[dasdoing]

check out this specific tube sound (timemarked)

saturation can indeed cause an illusion of "more detail"

 

[svtcontour]

Just wondering…did you manage to measure both tube & SS for comparison? I browsed through the thread and couldn’t find it…

Apologies for the delay. I did actually. There was some variance in the bass - a little more lean for the tube but subjectively while listening, it doesnt sound like its the 3db or so difference. The red is the tube and the blue a solid state (Behringer EP4000 - QSC RMX clone). Also the output voltage at the time of measuring was 0.2v lower so might explain why its just a tiny bit lower across much of the range.

 

[antcollinet]

Also the output voltage at the time of measuring was 0.2v lower so might explain why its just a tiny bit lower across much of the range.

IMO That is most likely caused by the higher output impedance of your tube amp compared with the solid state amp - especially where you see the increased deviation in the bass area. If there is a speaker impedance dip in a frequency region then the amp output will also dip due to the increased current through the amp output impedance.

The variation at the top end could well be a slight rolloff in FR at the higher frequencies of the tube amp.

 

[svtcontour]

IMO That is most likely caused by the higher output impedance of your tube amp compared with the solid state amp - especially where you see the increased deviation in the bass area. If there is a speaker impedance dip in a frequency region then the amp output will also dip due to the increased current through the amp output impedance.

The variation at the top end could well be a slight rolloff in FR at the higher frequencies of the tube amp.

Ah that does make sense now that you say it and I think about it. My open baffles are lower in impedance in the bass area so I guess current requirement would be highest there. Subjectively though it still sounds great in the bass. Maybe very slightly more light like one tick on a tone control lets say.

 

[kelesh]

This is the little amp. View attachment 316490

Is that a Panasonic 3700 DAT machine underneath?

 

[antcollinet]

Subjectively though it still sounds great in the bass. Maybe very slightly more light like one tick on a tone control lets say.

Or easily fixed with a little EQ.