Glenn Studio Amplifiers

Is there a website? I'll be looking for a great tube amp next year.

 

Glenn doesn't have a website - No need to advertise as his sales are all via word of mouth, meets or forum impressions. Send him a PM ( user name: 2359Glenn) here to get more information or to order. Please let me know when you have done so and I will prompt him to check his messages (he has only started posting here).

 

Here are a few pictures of amps Glenn has built for others:

Standard 300B SET headphone amp



Glenn 300B running Elrogs. These require a regulated filament supply, which this amp has.



The underside of the 300B build immediately above, which includes a couple of upgrades (Duelund coupling caps & Goldpoint 47 step attenuator):




OTL allowing use of 6 x 6BL7 as output (6SN7 driver in this build)



Latest OTL with Lundahl mains transformer. Otherwise, very similar to @gibosi 's OTL

 

PMd him.

 

As the C3g is a tube of interest in this forum, I thought I would share what I have learned about this tube. First, all the white, silk-screened shiny-black C3gs were manufactured in the 1970's by Siemens, even those labeled Lorenz, Valvo and Telefunken. Several colleagues have removed the shiny black cans and discovered the internal construction is identical, regardless of branding, and as expected, they all sound the same.

Now, the claim is often made that this tube is so transparent that it doesn't have it's own sound. While this is part of the mythology, in my experience, it is not true. Tubes manufactured in different factories sound different. And further, tubes manufactured in the same factory, but at different times, often sound different. In the 1950's and '60's, the C3g was manufactured by Siemens, Lorenz and probably Telefunken.

These earlier tubes are easy to recognize as they have embossed flat-black cans. Colleagues have removed the flat-black cans from a pair of old Lorenz, and indeed, the construction is very different, and yes, they do sound different. Recently, I came into possession of a pair of old embossed flat-black Siemens and while I have no interest in removing the cans to compare construction, I can say that these sound different compared to the newer shiny-black C3g.

In my opinion, these three variants are each excellent, but again, they sound slightly different. I am hopeful that I will eventually come across a pair of embossed, flat-black Telefunkens at a price I am willing to pay. However, as I am not a big fan of the Telefunken sound, I am simply unwilling to pay top dollar.

I am hopeful this information will be useful to those of you who are using these tubes now, or plan to do so in the near future.

To the left, old embossed, flat-black Siemens, in the middle, shiny-black Siemens, and to the right, embossed flat-black Lorenz.

 

Moatsart

Are you Khragon at head-fi?

 

Tonynewman

 

Ah. Tsk tsk. I also thought you were next. I am interested in when your amp will be built because mine should be next! Or is it? I am getting more confused now...

 

Yep, I heard that from Bon Jovi many times.

 

You, too? I'm banned for life. My crime? Having an opinion.

 

I'm khragon over at hf. Excited to be next, the amp will be a 300b, my end game tube amp. Will pair it with audiogd master 11.

 

Will definitely share my impressions, although I suck at describing what I am hearing, still will try my best.

 

I reckon that would be a nice pairing Khragon.

 

TL;DR: Exceptional OTL tube amp for the price.


Amp notes:

I purchased one of Glenn’s OTL amps used about 3 months ago as of writing this for $700. From my reading, the design goal was to create a tube amp that sounded great at a low price point, and to ensure that the amp did not require the use of uber tubes to sound good (a WA problem IMO). Better tubes do indeed sound better, but the jump isn't massive in my experience.

As other’s have stated in the thread, the amp can be customized to some degree. My specific amp has an upgraded pot (still need to open it to see what it is), a 4 pin XLR out in addition to the standard ¼” TRS, a heater voltage selector (6v, 12v, 25v) for the driver tube socket, speaker outs and an over-sized transformer. My build does not have the newer Lundahl transformer or the c3g driver. There is a single set of SE inputs and no pre out or any other features in that regard. My build runs one 6SN7/12SN7/1633 driver, two 6080/6AS7/5998/6336 output tubes, and one 5ar4/GZ32/GZ34/GZ37/5u4 (etc) rectifier.

The tubes I run are:
WE 422 Rectifier
WE 421 Outputs (5998 equiv)
Tung Sol 6f8g RP Driver (a 6v tube, via an adapter)


Sound impressions:

As a point of reference, I will primarily be comparing the amp to my Ragnarok, as it’s well known within the community and it's what I have on hand. A Schiit Yggdrasil is simultaneously feeding both. While I’d love to compare the Glenn OTL to a relevant tube amp, such as the EC ZDS, EC Super 7, DNA Stratus, blah blah...I haven’t heard them and can’t comment. Sorry. I primarily use a lightly modded HD800 with the Glenn.

The delivery of the Glenn is liquid, dynamic, lively and slightly warm, though it can be tuned to some extent based on tube selection. I prefer to run it more on the neutral/forward side of things; it’s not at all jarring to move from listening via the Rag to the Glenn. I’m not a fan of heavy coloration and I’m quite satisfied with the result I was able to obtain - warm leaning but not syrupy or gooey. Definitely not limp dick. To provide another reference point, one of my local audio friends described the Glenn as a, “Crack on Steroids”. While I don’t think that’s entirely accurate, I do think it provides some context of what the Glenn sounds like - dynamic, warm leaning, full bodied - except that it’s technically in a completely different league than the Crack w/Speedball.

Compared to the Rag, the Glenn OTL is more resolving; not to the extent that it would be super easy to pick out at a noisy meet, but in a quiet environment it’s quite obvious. Tiny shifts in volume are more apparent and the resulting sonic picture is more cohesive and complete. Textures are more fully realized, which adds a sense of realism and immersion. Yggdrasil has proven to be a synergistic pairing, as it’s neutrality and (slightly) analytical nature match well with the tasteful warmth and liquidity of the Glenn. It has also brought me to appreciate Marv’s comments on how Yggdrasil has more to offer than the Rag can fully take advantage of - not that there was doubt, but hearing it for oneself has been a lot of fun.

Spatially the Rag is flatter; more 2D if you will - Less depth and dimensionallity, though the stage width is pretty close between the two. The Glenn is also slightly airier with better separation, despite being dynamic and full bodied. Conversely, I feel the Rag does have slightly better extension on both ends (not a huge surprise). I have to consciously try to listen for it though, it's very close.

If my specific build has a weakness, it’s that the background isn’t particularly “black”. There is very tiny bit of transformer “hum” that can be heard when no music is playing. I can’t hear it at all if I have any music playing, even at very low volumes, but it is there. From my understanding, this is part of why Glenn has moved to Lundahl transformers for more recent (and more expensive) builds. Regardless, it’s far from a deal breaker, but is worth mentioning.


Some specific notes on headphone pairings:

Senn HD800 (Liner/small piece of creatology foam): Really, really enjoyable with this amp. Bassier/fuller than on the Rag (output impedance related I assume) and is able to take advantage of the additional resolution, liquidity and spatial cues provided by the Glenn. No harshness at all with light mods, very satisfying, smooth and effortless. XLR out is slightly better than the SE out, despite the amp being single ended. Tons of volume headroom - 9 o’clock is typically about as loud as I want. Not even close to a face tweeter. Sublime.

Senn HD600 (dynamat on back side of driver): Similar to the HD800 notes. The amp especially improves the headstage vs. the Rag. Very resolving in the mids and treble. I could pretty much live with this combo and call it quits.

HiFiMan HE-6 (ohhgourami modded): When I first purchased the amp, I didn’t expect it to even run the HE-6, but I’ll be damned. Not only does it run it, but it runs it well. Bass level is similar to the Rag here. More liquid than the Rag though, which is of some benefit to the HE6’s treble, especially on tracks with sibilance problems. Very good grip and control. The Rag’s superior bass extension is noticeable here, which I find advantageous with the HE-6. At a local meet, some preferred the HE-6 out of the Glenn. Personally I still prefer the Rag. Loud listening for me with the HE-6 was at about 12 o’clock on the volume dial.YMMV.

Fostex TH-X00 (stock): I anticipated preferring these out of the Rag, but ended up liking them more out of the Glenn. The slightly rough treble of the TH-X00 was simply more pronounced out of the Rag and the Glenn was able to smooth that out a bit while providing a slightly more satisfying headstage. On the flip side, they are slightly bassier via the Glenn, which could be good or bad depending on tastes/preferences. All in all, a surprisingly good pairing.

 

I am surprised to learn that the Glenn with a pair of WE 421 drives the HE-6 as well as it does. As you have the beefier transformer, I assume you can run a pair of 6336? A pair of these draw 10 amps compared to only 5 amps for a pair of WE421. If you should decide to get a pair, it is my understanding that the 6336A and 6336B are preferable to the 6336. (I have a pair of 6336B.) From what I have read, some have had the older 6336 arc on them...

 

It came as a bit of a shock to me as well. I still prefer the HE-6 with solid state due to the bass extension and tautness, but I can see where some would prefer them with a tube amp. I don't know if the larger transformer has anything to do with the amps ability to run the headphone successfully or not. As for the 6336 tubes, yeah, it can apparently run them. I don't have any, as I don't expect to be running orthos off this amp, but it's cool to have the flexibility.

 

Thank you for the the nice review
It will drive the HE-6 better with a pair of 6336B the amp can take these tubes.
The Lundahl transformer is even more powerful then this transformer and allot quieter but 3X the price.

 

@2359Glenn

Thanks for making such nice custom amplifiers and selling them for very reasonable prices. It's clearly apparent that you don't build them with personal profit in mind, as I feel this amp would commercially sell for at least 2x the price (not sure what the initial build cost of my specific amp was, but I'd guess a bit over a grand). Obviously these aren't off the shelf, mass produced products, given that each one is a unique build, but they're well worth the wait if people are up for it.

The Lundahl transformer sounds like it would be very nice, but I don't think people should be afraid of the earlier builds if they happen to stumble across one for sale (a rarity, but it can obviously happen). I found it interesting that despite not having a pitch black background, microdetail, or "plankton" as is often said around these parts, is notably more apparent and clearly rendered on the OTL compared to my solid state amp (which is dead silent). To use the HF cliche, I've heard things in familiar music with the OTL that I hadn't heard before. In other words, it's not a huge issue in the grand scheme of things and doesn't get in the way of the music IMO.

I don't doubt that the 6336b tubes would be advantageous for the HE-6 or orthos in general. That said, the amp is so good with hi-z dynamics, that I don't anticipate tuning it in this direction. Having the option is a bonus though and will certainly appeal to some folks. I really just threw the HE-6 comments in initially as it caught me off guard how capable the amp was with this headphone.

 

Great, considered review @JoelT

Would you be able to expand at all on comparisons with the Crack? When you say it is technically better are we talking about a higher level of resolution and focus? Are there any circumstances at all when you would prefer the Crack with your 600s?

Would be great to hear one of these. Shipping to UK might be a killer though.

 

I compared the Crack w/SB directly to another Glenn OTL owners amp about a year ago (he was feeding it via a lackluster sabre DAC), so it's been awhile. But off of memory, superior clarity, resolution and overall "grip" on the transducer with the Glenn. The Crack was looser/sloppier/blurry with inferior technicalities all around. I primarily brought up the Crack as I feel it has a similar "flavor" to the Glenn OTL. I certainly feel if someone is a fan of the delivery of the Crack, they'd really love the Glenn. No, I honestly can't think of a situation where the Crack would be preferable with the HD600, unless there was some mastering problem you wanted to bury.

Tell you what, I still need to install the Speedball upgrade on my Crack (should have had it done already, but I got sidetracked with this amp), so I'll post a more meaningfully comment down the line. I should have some time in the near future to get that installed. I can say definitively that the stock Crack is a sloppy, mushy, poorly resolving mess comparatively (I actually like the Crack for the price, so I'm not knocking it per say - just being blunt); even with semi decent tubes in the Crack like a TS 5998 and a Mullard CV4003.