[DeweyCH]

Public Service Announcement: Just in case anyone woke up this morning feeling knob-deficient, I just got this Knob Alert from Antique Electronic Supply.
(sorry...not intending to advertise for them (although they are a good vendor) just when you get an email titled "Knob Alert" you can't help but crack up )

https://www.tubesandmore.com/produc...ail&utm_term=0_0cd0c8c92f-098e1d411d-38906177

Might have to forward this to my wife. She's all the time rejecting knob alerts.

 

[JKDJedi]

So this happened this morning:



And ach mein gott it's a lovely sound. After "Dear Prudence" I think I was convinced to come out and play.

I just finished with the resistors swap... that was an adrenaline rush because stuff was falling out that wasn't supposed too...
Anyways letting her settle in off the desk...just in case!

 

[L0rdGwyn]

Sorry if you follow my DIY thread, I will be posting this there too.

Had some time today so I took my measurements of the Darkvoice 336SE. I wanted to use the stock tubes and not something completely unobtainium, I also have a very limited collection of 6SN7 now, so what's in there is a NEC 6520 and Russian 6H8C. All measurements were done on the left channel into a 300ohm dummy load.



Here is the frequency response at 1mW into a 300ohm. As you can see, there is some low frequency rolloff, about -2dB at 20Hz. High frequency extension is good.



THD+N FFT plot at 1mW into 300ohm. Distortion is exclusively 2nd harmonic at 0.22%. Power supply noise at 60Hz at around -72dB, 120Hz at -78dB.



Same measurement at 10mW into 300ohm, 0.73% THD, now seeing a smidge of 3rd harmonic.



1kHz square wave 1mW into 300ohm.



10kHz square wave 1mW into 300ohm.



100Hz square wave 1mW into 300ohm.



The low frequency rolloff can be seen on the 1kHz square and very plain on the 100Hz square, the 10kHz square is pretty good with a hint of HF rolloff which can be seen on the FR plot.

I measured the output impedance as well at 1kHz, it is roughly 71.5ohm.

As I mess around inside the amp, I'll take repeat measurements for comparison.

 

[JKDJedi]

Sorry if you follow my DIY thread, I will be posting this there too.

Had some time today so I took my measurements of the Darkvoice 336SE. I wanted to use the stock tubes and not something completely unobtainium, I also have a very limited collection of 6SN7 now, so what's in there is a NEC 6520 and Russian 6H8C. All measurements were done on the left channel into a 300ohm dummy load.



Here is the frequency response at 1mW into a 300ohm. As you can see, there is some low frequency rolloff, about -2dB at 20Hz. High frequency extension is good.



THD+N FFT plot at 1mW into 300ohm. Distortion is exclusively 2nd harmonic at 0.22%. Power supply noise at 60Hz at around -72dB, 120Hz at -78dB.



Same measurement at 10mW into 300ohm, 0.73% THD, now seeing a smidge of 3rd harmonic.



1kHz square wave 1mW into 300ohm.



10kHz square wave 1mW into 300ohm.



100Hz square wave 1mW into 300ohm.



The low frequency rolloff can be seen on the 1kHz square and very plain on the 100Hz square, the 10kHz square is pretty good with a hint of HF rolloff which can be seen on the FR plot.

I measured the output impedance as well at 1kHz, it is roughly 71.5ohm.

As I mess around inside the amp, I'll take repeat measurements for comparison.

Just don't put in 1k resistors were 1m belong.. Not that I know of anybody thats done that.. (My Darkvoice is running excellent now....wow.. very nice, thanks @therremans ) Because of the inherited elevated gain by going with the Fitz Mod I decided to stay put with the LED Mod I already had in place. (I've installed the 1k resistors in place of the LEDs) WiIl not comment on sound till this unit burns in some more, took the whole morning and two cups of black coffee... now for that Tequila. Happy New Year

 

[bcowen]

Might have to forward this to my wife. She's all the time rejecting knob alerts.

ROFL!!

 

[bcowen]

@bcowen I am very much looking forward to more pressures from the GEC 4079, mainly with double tubes in the front. I bought two pairs of GEC 4079 that are already with me and Deyan's supporters are almost here. Then I can share my impressions.

Tonight's roll. GEC L63's and GEC CV4079's. I was getting a slight bit of background hum with the Pinnacle (Russian) 6J5's. With the L63's? Dead silent. Dead silent as well with Tung Sol round plate 6J5's. So the double-double tube adapters are not in and of themselves an issue in the DV (or at least my DV), but there could be some tube dependency at play.

This combo is sounding very, very nice.

 

[Slade01]

Tonight's roll. GEC L63's and GEC CV4079's. I was getting a slight bit of background hum with the Pinnacle (Russian) 6J5's. With the L63's? Dead silent. Dead silent as well with Tung Sol round plate 6J5's. So the double-double tube adapters are not in and of themselves an issue in the DV (or at least my DV), but there could be some tube dependency at play.

This combo is sounding very, very nice.

Awesome! Very good to hear!

 

[therremans]

Tonight's roll. GEC L63's and GEC CV4079's. I was getting a slight bit of background hum with the Pinnacle (Russian) 6J5's. With the L63's? Dead silent. Dead silent as well with Tung Sol round plate 6J5's. So the double-double tube adapters are not in and of themselves an issue in the DV (or at least my DV), but there could be some tube dependency at play.

This combo is sounding very, very nice.

Very nice, glad to hear its working out with multiple tubes. Looking forward to hearing these power tubes when my adapter arrives.

 

[hmscott]

I'm sure this has been mentioned before, if not here somewhere, at least I've seen it mentioned. IEM's are more sensitive than headphones to tube HISS.

I've learned that first hand with my Xduoo TA-20. I rolled-in a Gain Matched Pair of NOS RCA Clear Top "Baldwin" tubes and ran them for 24+ hours on a couple of pair of 600 ohm Beyerdynamics DT990 / DT880, SendyAudio Aiva's, DT770 16 ohm, and the tubes were great, really loved the Bass and Tone overall.

Then I plugged in a pair of KZ ZAX on 99.99% pure silver 4n cable balanced 4.4mm - using a 4.4mm to XLR adapter and my ears were hit by a Wall of HISS...higher in the left channel, HISS overpowering in the Right channel too.

I went back to headphones, sounds fine, back to IEM's, WALL of HISS.

Swapped a new pair of factory gain matched boxed PSVANE 12AU7-T MKII's which I'd previously verified worked - and no HISS at all, from 0-95 volume (maximum) on the TA-20, sweet sounds, and no hissy noises.

Too bad, I like the NOS RCA Clear Top Baldwins otherwise... but they have been given an RMA by the seller and I'll pick something else.

Happy New Year!!

 

[JKDJedi]

I'm sure this has been mentioned before, if not here somewhere, at least I've seen it mentioned. IEM's are more sensitive than headphones to tube HISS.

I've learned that first hand with my Xduoo TA-20. I rolled-in a Gain Matched Pair of NOS RCA Clear Top "Baldwin" tubes and ran them for 24+ hours on a couple of pair of 600 ohm Beyerdynamics DT990 / DT880, SendyAudio Aiva's, DT770 16 ohm, and the tubes were great, really loved the Bass and Tone overall.

Then I plugged in a pair of KZ ZAX on 99.99% pure silver 4n cable balanced 4.4mm - using a 4.4mm to XLR adapter and my ears were hit by a Wall of HISS...higher in the left channel, HISS overpowering in the Right channel too.

I went back to headphones, sounds fine, back to IEM's, WALL of HISS.

Swapped a new pair of factory gain matched boxed PSVANE 12AU7-T MKII's which I'd previously verified worked - and no HISS at all, from 0-95 volume (maximum) on the TA-20, sweet sounds, and no hissy noises.

Too bad, I like the NOS RCA Clear Top Baldwins otherwise... but they have been given an RMA by the seller and I'll pick something else.

Happy New Year!!

 

[hmscott]

funny gif

Ask / comment with words, please.

The moral of my story, don't accept tubes until you've listened to your sensitive IEMs on the "new" tubes.

 

[JKDJedi]

Ask / comment with words, please.

The moral of the story, don't accept tubes you haven't yet listened to with sensitive IEMs

we joke around here a lot. your a new guys so maybe i should've introduced myself first.. I'm the old guy here and the rest are ancient... No seriously, why iems on a tubed amplifier?

 

[hmscott]

we joke around here a lot. your a new guys so maybe i should've introduced myself first.. I'm the old guy here and the rest are ancient... No seriously, why iems on a tubed amplifier?

Because they sound amazing, just like headphones, maybe it's a new guy thing - I'm 62. Plugged in my first tubes - correction - unplugged my first tubes in 1968, while I was repairing the neighborhood TV's.

First time back into tubes in 50+ years, wanted more power for my 600 ohm headphones, IEM's are a bonus - besides I have 3x as many IEM's as headphones, so whatever I get needs to pull weight on both piles.

Like I said, the PSVANE 12AU7-T MKII's - new and themselves breaking in - I just got the Xduoo TA-20 on Dec 27th and the tubes just before that. So I'm in discovery mode.

No problem about the joking, I need to sync up first on the details I'm trying to ascertain with help from others... the Moose with Antlers didn't look like an Audiophile

I've alerted my NOS tube suppliers (yeah I've jumped in with both feet) of my need to use IEM's too, so low noise tubes are a priority moving forward - whatever they supply needs to be tested for noise with a sensitive IEM to make sure there is no Cloud of Electrons Hissing around inside.

The TA-20 stock tubes I think are also PSVANE, or JJ or EH tubes, just the lower end of the product line, but they don't HISS either.

I may be stuck with new tubes of our current generation, but a couple suppliers think they can find NOS tubes that will work, a third isn't talking to me anymore... or she's just thinking.

So suggestions for NOS or new tubes that have no HISS would be appreciated, besides the PSVANE, JJ, EH, and maybe NOS Telefunken, any ideas?

I've also got a Topping D90 MQA and Topping A90 paired up that play IEM's and headphones well, along with a FiiO M15 for portable use.

The TA-20 is to get a bit more power to the 600 ohm headphones and enjoy some "tubular" sound on all the headphones and IEM's.

 

[Slade01]

Very nice, glad to hear its working out with multiple tubes. Looking forward to hearing these power tubes when my adapter arrives.

Same here. I'm hoping that round 2 with a newly fixed adapter will be more promising. Otherwise, if its not in cards for my DV to run it like this -- I have a nice little Brimar 6SN7GT coming to pair with those CV4079s and will call it a day.

 

[bcowen]

Same here. I'm hoping that round 2 with a newly fixed adapter will be more promising. Otherwise, if its not in cards for my DV to run it like this -- I have a nice little Brimar 6SN7GT coming to pair with those CV4079s and will call it a day.

I wanted to test the dual-dual thing out in my DV first, but now that I have with good results I want to hear what these CV4079's will do in the Incubus. @therremans has me busy getting ready to tear the DV apart again anyway (I'm just trying to keep up ) so now's a good time.