[theveterans]

I usually turn on the tubes a few hours before listening. I find the hot tubes sound better.

It’s supposed to be like that. I have tried just turning on to warm up without anything playing back for an hour then I start to listen but still it takes between 30-45 minutes before it sounds best (total time of 1 hour 45 minutes from being turned on). I have also tried cold start and it also take the same amount of time (30-45 minutes) for it to sound best. It’s really baffling that the amp needs an actual AC analog signal to actually warm up and not just the tube itself

 

[Strayngs]

It’s supposed to be like that. I have tried just turning on to warm up without anything playing back for an hour then I start to listen but still it takes between 30-45 minutes before it sounds best (total time of 1 hour 45 minutes from being turned on). I have also tried cold start and it also take the same amount of time (30-45 minutes) for it to sound best. It’s really baffling that the amp needs an actual AC analog signal to actually warm up and not just the tube itself

Which amp do you have? I wonder if there is variance with the tubes or amp itself? Or am I just a sucker for placebo?

 

[theveterans]

I guarantee you it’s not a placebo since I can duplicate the experience every listening session that I had. I have the Forge aka Mogwai OG with SS rectification, TAD KT66 and 5691 tubes. It sounds restrained or 80% of its best sound and then everything becomes open, have that ridiculous slam and dynamics, bottomless sub-bass, microdetails pop up in an unrestrained manner after 30-45 minutes of nonstop playback from either cold or hot tubes

 

[theveterans]

Has anybody dared trying out a 6922 as substitute for 5751?

 

[ChocolateChipTrip]

I'm a noob to the forum and tube rolling, but wanted to share some recent experiences. The journey began when the right channel of my Nautilus suddenly went out. Naturally, I panicked and since I was unable to live without it for 5 seconds, I immediately drove out to Upscale Audio, i.e., the nearest place I knew of to get tubes the same day. Yup, that was my first mistake, not having a spare set of tubes on hand. Thankfully, I got ahold of Justin before making the mistake of blindly buying new production tubes. The guys at Upscale were nice enough, but of no help. They basically just told me to place an order online and they would bring my tubes out from the back. Refused to make a recommendation or guide me on my purchase, which I thought was lame.

Justin recommended that I first try replacing the fuse. Since I was keen to try out some new tubes anyway, he put together a little "care package" for me with a full set of NOS tubes he recommended based on my equipment at a very reasonable price: Sylvania 6L6GCs, JAN Philips 5U4GBs, a Raytheon 12AX7 Black Plate and a bonus Baldwin 12AX7 Japan short. For reference, my original stock tubes were new production Mullard KT88s, Tung-Sol 5AR4s and a Tung-Sol 5751.

Before swapping in Justin's tubes, I tried replacing the fuse. 15-20 seconds after flipping it on, the amp started to hum, low at first and got louder as my right channel 5AR4 rectifier started to glow increasingly brighter for about 2 seconds before the fuse popped and the right channel went dark. Tried it again and got the same result. Not wanting to damage the new tubes he just sent me, I emailed Justin about it.

I did not know that Justin was enjoying his vacation in Hawaii when he called me to troubleshoot my amp, and I would have been totally fine with waiting until he got back. This was a testament to Justin's industry-leading support and service. He truly stands behind the amazing products that he makes, and his passion for the craft comes across loud and clear every time you speak with him. Justin recommended that I swap in the new rectifiers and if that did not work, we would make arrangements to have the amp serviced when he got back.

Thankfully, swapping in the 5U4GBs did the trick. I spent some time with these new rectifiers and found that I really liked the "liquid" character that they imparted to the music. It still allowed the KT88s to deliver the punchy, controlled bass that I loved, and smoothed out some of the harshness of brighter recordings (e.g., some MoFi One-Steps). Swapping in the 6L6GCs brought in some bloom and with that seductive tone, some of the most eerily realistic vocals I have ever heard reproduced on any equipment, period. I found that the KT88s still came out ahead on PRAT, especially with up-tempo, dynamic recordings (e.g., classic and prog rock). Swapping the gain tube yielded more subtle changes, but I found that the Baldwin 12AX7 Japan short played best with others.

I was loving the ability to adjust tone and learn how the Nautilus responded to different tubes. I was hooked and ready to go deeper into the rabbit hole. After doing some research and seeing what other owners liked in their Nautilus, I went a little crazy and bought the following NOS tubes: Tung-Sol (US) 6550s, Raytheon (Japan) GZ34s, GEC TT21s, a JAN Philips 12AT7 and a Telefunken G73-R. Too many new toys for this noob, and I made yet another mistake: putting in the TT21s without a KT88 adapter. I was wondering why they were producing such a loud hum and thought maybe I got some bad tubes. Thankfully this did not damage any equipment and it was remedied by fitting them back in with the adapters I ordered on eBay from China.

I am still trying out different combos to see what works best with different types of headphones and music, but right now I am really enjoying the TT21s with the G73-R and Justin's 5U4GBs. I'm a detail junkie, so the Utopia has become my go-to headphone. I now have the Falcon LS3/5a as my monitors, which was yet another great recommendation by Justin; they have much better synergy than my old B&W 705 Signatures. With my equipment, I found that the Raytheon GZ34s feeding the TT21s were coming across as bright in many recordings, perhaps the result of overpowering sensitive speakers/HPs. However, the TT21s sure do sound great with Justin's 5U4GBs.

I found it interesting that my preferences (thus far) differ in some ways from others, who seemed to prefer the following combos in the Nautilus: (1) KT88s or 6550s with 5AR4s; and (2) 6L6s with 5U4s. One might call those "complimentary" combos. On my equipment I preferred the opposite: "contrasting" combos. For example, the 5AR4s can control and sharpen up the bloom of the 6L6GCs, whereas the 5U4GBs tamed the some of the brightness of the TT21s, KT88s and 6550s, while still allowing authoritative and punchy bass to come through.

I note that these are early and highly generalized observations but I thought I would share them with other ampsandsound enthusiasts to see if my observations and experiences might resonate with you. I hope this is helpful to some and I feel safe sharing my own stupid mistakes with the group since I never see abusive comments in these forums. This really is an awesome hobby and these recent experiments have reminded me of how much I love what we do.

 

[shwnwllms]

I'm a noob to the forum and tube rolling, but wanted to share some recent experiences. The journey began when the right channel of my Nautilus suddenly went out. Naturally, I panicked and since I was unable to live without it for 5 seconds, I immediately drove out to Upscale Audio, i.e., the nearest place I knew of to get tubes the same day. Yup, that was my first mistake, not having a spare set of tubes on hand. Thankfully, I got ahold of Justin before making the mistake of blindly buying new production tubes. The guys at Upscale were nice enough, but of no help. They basically just told me to place an order online and they would bring my tubes out from the back. Refused to make a recommendation or guide me on my purchase, which I thought was lame.

Justin recommended that I first try replacing the fuse. Since I was keen to try out some new tubes anyway, he put together a little "care package" for me with a full set of NOS tubes he recommended based on my equipment at a very reasonable price: Sylvania 6L6GCs, JAN Philips 5U4GBs, a Raytheon 12AX7 Black Plate and a bonus Baldwin 12AX7 Japan short. For reference, my original stock tubes were new production Mullard KT88s, Tung-Sol 5AR4s and a Tung-Sol 5751.

Before swapping in Justin's tubes, I tried replacing the fuse. 15-20 seconds after flipping it on, the amp started to hum, low at first and got louder as my right channel 5AR4 rectifier started to glow increasingly brighter for about 2 seconds before the fuse popped and the right channel went dark. Tried it again and got the same result. Not wanting to damage the new tubes he just sent me, I emailed Justin about it.

I did not know that Justin was enjoying his vacation in Hawaii when he called me to troubleshoot my amp, and I would have been totally fine with waiting until he got back. This was a testament to Justin's industry-leading support and service. He truly stands behind the amazing products that he makes, and his passion for the craft comes across loud and clear every time you speak with him. Justin recommended that I swap in the new rectifiers and if that did not work, we would make arrangements to have the amp serviced when he got back.

Thankfully, swapping in the 5U4GBs did the trick. I spent some time with these new rectifiers and found that I really liked the "liquid" character that they imparted to the music. It still allowed the KT88s to deliver the punchy, controlled bass that I loved, and smoothed out some of the harshness of brighter recordings (e.g., some MoFi One-Steps). Swapping in the 6L6GCs brought in some bloom and with that seductive tone, some of the most eerily realistic vocals I have ever heard reproduced on any equipment, period. I found that the KT88s still came out ahead on PRAT, especially with up-tempo, dynamic recordings (e.g., classic and prog rock). Swapping the gain tube yielded more subtle changes, but I found that the Baldwin 12AX7 Japan short played best with others.

I was loving the ability to adjust tone and learn how the Nautilus responded to different tubes. I was hooked and ready to go deeper into the rabbit hole. After doing some research and seeing what other owners liked in their Nautilus, I went a little crazy and bought the following NOS tubes: Tung-Sol (US) 6550s, Raytheon (Japan) GZ34s, GEC TT21s, a JAN Philips 12AT7 and a Telefunken G73-R. Too many new toys for this noob, and I made yet another mistake: putting in the TT21s without a KT88 adapter. I was wondering why they were producing such a loud hum and thought maybe I got some bad tubes. Thankfully this did not damage any equipment and it was remedied by fitting them back in with the adapters I ordered on eBay from China.

I am still trying out different combos to see what works best with different types of headphones and music, but right now I am really enjoying the TT21s with the G73-R and Justin's 5U4GBs. I'm a detail junkie, so the Utopia has become my go-to headphone. I now have the Falcon LS3/5a as my monitors, which was yet another great recommendation by Justin; they have much better synergy than my old B&W 705 Signatures. With my equipment, I found that the Raytheon GZ34s feeding the TT21s were coming across as bright in many recordings, perhaps the result of overpowering sensitive speakers/HPs. However, the TT21s sure do sound great with Justin's 6L6GCs.

I found it interesting that my preferences (thus far) differ in some ways from others, who seemed to prefer the following combos in the Nautilus: (1) KT88s or 6550s with 5AR4s; and (2) 6L6s with 5U4s. One might call those "complimentary" combos. On my equipment I preferred the opposite: "contrasting" combos. For example, the 5AR4s can control and sharpen up the bloom of the 6L6GCs, whereas the 5U4GBs tamed the some of the brightness of the TT21s, KT88s and 6550s, while still allowing authoritative and punchy bass to come through.

I note that these are early and highly generalized observations but I thought I would share them with other ampsandsound enthusiasts to see if my observations and experiences might resonate with you. I hope this is helpful to some and I feel safe sharing my own stupid mistakes with the group since I never see abusive comments in these forums. This really is an awesome hobby and these recent experiments have reminded me of how much I love what we do.

Welcome to the A&S thread. Great post. It never ceases to amaze me the level of exemplary service @ampsandsound delivers to his customers. Justin is a stand up guy, always willing to go that extra mile. He’s always willing to take a phone call and troubleshoot, vacation or not. I wish there were more like him in the industry.

 

[linshu1992]

Hi folks, I have listed my Nautilus for sale if anyone is interested. About to travel for a long period so I guess someone else can enjoy this beast more.

https://www.head-fi.org/classifieds/ampsandsound-nautilus.62359/

 

[ampsandsound]

Welcome to the A&S thread. Great post. It never ceases to amaze me the level of exemplary service @ampsandsound delivers to his customers. Justin is a stand up guy, always willing to go that extra mile. He’s always willing to take a phone call and troubleshoot, vacation or not. I wish there were more like him in the industry.

Just read this. Super kind guys. Thanks a bunch.

 

[shwnwllms]

Had a rectifier blow the other day (on startup) on my Agartha. Luckily I was watching it since it started to buzz right before the cathode flashed. Immediately shut it down and no issues with the fuse, caps or other tubes.

Popped in a Fivre 6AX5 from my stash of rectifiers and it’s been running like a champ ever since.

I’ve read that the 6AX5 is a reliable rectifier (esp when compared to 6X5 which was plagued with problems) but @ampsandsound amps are even more reliable. The fact that it didn’t take out anything with it is a testament to Justin’s craftsmanship.

 

[shwnwllms]

Had a good chat with @ampsandsound the other day. Thanks for calling me Justin.

It got me thinking about my use of a preamp with my Agartha 2021, specifically about my GS-X MK2 and whether it’s a good match or even needed in my current system. Justin says he shoots for a gain factor of 4X going into his amps (GS-X MK2 on medium is 12.5X, low is unity gain so that's out). So my Preamp may be a bit too hot on the input with the GS-X MK2,

For reference my Holo May outputs 1.45 Vrms over RCA when outputting DSD (upsampling via HQP)

Agartha Rev 2 input sensitivity is 1.2V or 1.4V P-P with a 12AX7, assuming the 2021 is somewhere close to that with a 6SL7 I should be covered with the RCA output of the Holo May alone (ie I’m not really lacking enough voltage swing for optimal dynamics or max volume)

I’m really enjoying the smooth, clean sound without a preamp in my chain. If anything I think I was probably overdriving the Agartha which was having some negative trade offs. If I decide to add a preamp in the future it will probably be one of Justin’s or a Booster Box which are a safer bet as they won’t color the sound of the Agartha and ER300Bs.

 

[theveterans]

With my Forge, I typically attenuate the DAC output to 1V or less using the Saga (pretty much acting as a step down transformer) to get that transparency in terms of having that relaxed/effortless sound while having that sound bolstering effect of a preamp. Then again, Forge doesn't have included step-down input transformer unlike the Agartha

 

[shwnwllms]

With my Forge, I typically attenuate the DAC output to 1V or less using the Saga (pretty much acting as a step down transformer) to get that transparency in terms of having that relaxed/effortless sound while having that sound bolstering effect of a preamp. Then again, Forge doesn't have included step-down input transformer unlike the Agartha

I was thinking of these two things as well, just wasn’t sure if optimal input was say 1V or 2V. I’m right in the middle and it definitely sounds better without the GS-X MK2 as a preamp (much more relaxed and effortless. I feel low end was also restricted when using the GS-X MK2 in front)

 

[sajesak]

http://ampsandsound.com/

Mogwai

Like many of our products, the Mogwai evolved from our earlier designs, borrowing from the Bigger Ben and Classic Wonder, while embracing the form factor of the Kenzie. The Mogwai offers more than an entry point for tube amps, but a hybrid product, meant for serious headphone and speaker use.

Our circuit offers the ability to roll a wide variety of tubes inexpensively and bring increased power to headphones without any sacrifice of design choices that conflict with our values.

The Mogwai combines the features of a full sized amp into a small amplifier package, weighing ~15lbs largely due to its over spec’d custom wound transformers. The Mogwai utilizes Single ended Class A operation with zero feedback to provide the essence of our Classic Wonder sound; strictly old school SET sound, while paired with a more accessible tube selection.

The performance of the Mogwai is made possible with custom wound ultra-high quality output transformers from Transcendar Transformers providing amazing frequency extension and flat response.

The Mogwai does not use a voltage divider network, but depends on transformers instead. We chose 32ohm tap for headphones to offer a dedicated selection for the widest range of headphones, and an 8ohm speaker tap to connect the Mogwai to moderately efficient speakers.

The Mogwai displays its transformers prominently on the chassis to frame in the tube selections, which can vary from a 6L6GC to a KT88.

Volume control is handled by the ALPS volume pot to allow attenuation and simplify the signal path… no preamp is needed. Zero feedback on the outputs negates the need for a pre, an iPhone can drive the Mogwai without issue.
The Mogwai differs from the Kenzie as it aims to provide powerful output while remaining true to 50s tube ideals, and single ended sweetness. As with all ampsandsound products, we strive for a neutral, non-fatiguing sound Junk Removal Lynnwood WA, and demand that all our products be ultra-quiet in operation. Quiet operation is not just a goal but a guiding principle that shapes all design and implementation choices… from pots to resistors we strive for tube amps to never distract from the music.

Input tube: 6SL7 or equivalent
Output tubes: 6L6GC, EL34s, KT66, KT77, KT88, 6550s and KT90s
Personal favorite is the TungSol 6L6GC STR. Warm, strong and tight bass.
Cathode Bias/automatic bias allows for easy tube changes without adjustment.

Compatible with 32ohm-300ohm headphones using the “32ohm” 1/4″ jack. (Beyerdynamic T1-600ohm were used successfully but not ideal.)

Headphones driven successfully or tested with the amp include, Mr. Speaker Ethers, Mr. Speaker Ether Cs, Audeze LCD-2.2F, Audeze LCD-XC, AKG240, AKG701, Sony MDRV6, Sennheiser HD650, Sennheiser HD800, Beyerdynamic T1-32ohm, HIFIMAN HE400i.

The Mogwai is made with pride in Southern California with US sourced parts, including our precision transformers.

Specs:
Input impedance is 250Kohm with alps pot, .5v for full power.
Noise with pot fully counterclockwise is 500 micro volts RMS
Measured with 6550 output tubes on 1/4″ 32ohm optimzied headphone jack. 500mW RMS output 20 Hz (-2db) to 17.7 kHz (-3db)
Measured with 6550 output tubes on 8 ohm tap. 3W RMS output 30 Hz (-1db) to 20 kHz (-2db)

Please look at our news section for feedback from owners of the Mogwai.
Mogwai Headphone amp – $1,700 with tube set.

Kenzie Headphone Amp

Like many of our products, the Kenzie Headphone Amp evolved from our earlier designs – in this case, rave reviews about the SE-84’s headphone section. The inevitable question followed; why didn’t we build a dedicated headphone amp?

Why indeed? After some research, we came to the conclusion that the Kenzie amp using the much loved darling circuit was the right choice for us. The outstanding performance of the Kenzie Headphone amp is made possible with custom wound ultra-high quality output transformers providing amazing frequency extension. The Kenzie does not use a voltage network, and has more than enough power to drive even the most difficult headphones. We chose 32ohm and 600ohm to allow use with the widest variety of headphones.

The Kenzie Headphone amp showcases the transformers on the chassis to frame in the amazing 1626 tubes in all their single-ended direct-heated bliss. We have included an ALPS volume pot to allow attenuation and simplify the signal path… no preamp is needed.

The 1626 AKA Kenzie is one of the sweetest-sounding amps you will ever hear. The 1626 is commonly referred to as the poor man’s 300b; all the same great imaging, texture, and single-ended sweetness without the cost to break the bank.

The 1626 is a WWII era tube used as a transmitter tube in radar installations. The design is shy on pure output, but is overflowing with texture and drive, and is paired with a massive choke and robust output transformers for ultra-quiet operation. As with all of our products, parts selection was crucial during this build and each chosen not for price, but for best quality and synergy.

Input tube: 12SL7 or equivalent
Output tubes: 1626 or VT-137 which is a WWII transmitter tube and characterized as sounding like a mini 300b.
Cathode Bias/automatic bias allows for easy tube changes without adjustment.
Compatible with 32ohm-300ohm headphones using the 32ohm 1/4″ jack.
Headphones above 300ohms will benefit from using the 600ohm 1/4″ jack.
Headphones driven successfully or tested with the amp include, Mr. Speaker Ethers, Mr. Speaker Ether Cs, Audeze LCD-2.2F, Audeze LCD-XC, AKG240, AKG701, Sony MDRV6, Sennheiser HD650, Sennheiser HD800 (though reduced volume), Beyerdynamic T1-600ohm, HIFIMAN HE400i.

The Kenzie is made with pride in Southern California with US sourced parts, including our precision transformers.

Specs:
Input impedance is 250Kohm with alps pot, .5v for full power.
Noise with pot fully counterclockwise is 5mV RMS (Average)
All measured at 32 ohm tap. All power measurements in RMS
100mW 20 Hz (-1db) to 17.7 kHz (-3db)
150mW 20 Hz (-1db) to 14.8 kHz (-3db)
200mW 20 Hz (-1.25db) to 16.7 kHz (-3db)

Please look at our news section for feedback from owners of the Kenzie Headphone amp.
Kenzie Headphone amp – $1,500 with NOS tube set.

Gizmo

I picked up the Mogwai that was at CanJam SoCal. Really loving it! These amps deserve their own thread. I'd post a pic of it, but it's the one on the website and the pictures are way better than what I can take.

Since I bought the prototype, I'm claiming the right of prima nocta... or something... and nicknaming my Mogwai "Gizmo."

Reviews

Kenzie Headphone Amp

Positive Feedback
Headphone.Guru
mithrandir38
joespride

Note that development continues over at ampsandsound, and additional amplifiers have come to be since the post was originally made.

The following headphones amps are now being made by ampsandsound:

• Kenzie: Based on the Darling circuit. Now has a coupling cap upgrade option.
• Kenzie Encore: Bigger than the original, headphone jacks now up front. Now has 2 inputs and 1 preamp out. Also comes in a Deluxe version with input transformers and upgraded coupling caps.
• Mogwai: Headphone / speaker amplifier in one, old school SET sound. Coupling cap upgrade now available.
• Mogwai Special Edition: Not yet widely available. Includes a tube rectifier and moves the the headphone jacks up front.
• Agartha: Uses 300b tubes, SET sound. Cap and input transformer upgrades available.
• Leeloo: Uses 12AX7 for input and a pair of EL-84s for output.
• NOTE: You can talk to Justin Weber and order different output impedance on the headphone jack than what's listed.

If using only digital sources like WAV or FLAC files and your DAC's volume/mute remote control is a truly lossless design (exaSound Audio Design > Products > e68 8-channel DAC ), then is there any need for a preamp another line stage between the DAC and the power amp? Isn't the sensitivity (the correct term?) of most power amps high enough to deliver at least 75% of full output with a 1 volt rms input? This DAC has a 2.1 v max output. Or will not using a separate preamp still compromise the system's dynamic range?

 

[ampsandsound]

It’s not just a question of voltage but of the drive func. More voltage lends to more better dynamic range but not whole story. Gain/drive is where dynamics live. Too much gain and you have noise. Not enough and there is not life.
Pre amps should give gain…. That all said every system is different. Barrow someone’s pre and try or build a simple pre to experiment with.

Your dacs true rms matters. Your amps input tube matters, is there a pre being used…. It’s not just getting to max vol but how the sig sounds it’s qualitatively different with a pre. Most headphone amps would have too much noise as a 2 stage amp and don’t need the power. But SE amps love a hot front end and pres extend dynamic swings.

Just my 2 cents.

 

[Solleks]

First time posting here, but I've been happily living with my Bigger Ben rev2 for quite some time. I've been rolling a decent amount of tubes but wanted to see if anyone had experience running EL37 power tubes? I wanted to try them in my BB but thought better of just dropping them in without trying to see if anyone else has done so before me. Should be equivalent to KT66 tubes in the limited research I've done, but anyone else have any insight or impressions?