HTC HMS-100 tubes/mods

BlueMDPicker

Hello All!

I know several of us own, or have owned, this nifty little unit in the last several years. I got mine from Mr. Grand (tip of the hat to you, George) and have thoroughly enjoyed it as my "garage system" (I have two old street rods, so spend a good deal of time there).

I decided to utilize it as a desktop system/headphone amp recently and it does a great job. However, with headphones, I am more aware of noise. I never rolled any other tubes into it, just used the stock 6N1's that came with it. I did a bit of reading here, and on the Internet in general, and saw @heiney9's recommendations (which I will follow-up on). Scrounged through my box-o-tubes last night and did not have any ECC85 types, so decided to try a NOS pair of RCA 6DJ8/ECC88 (yes, I understand the peril of plate voltage mismatch). So far, after 6+ hours of duty, they have not produced any pyrotechnics and are definite improvement in bass articulation and, perhaps, overall SQ. Still, though, a bit too noisy for my tastes.

So, my three-fold question: of those here who have, or had, this unit, do you have similar background noise issues; did you find tubes (or other things like power conditioning) that helped with this; did you do any circuit improvements or mods to the unit?

Thanks!

Mike

heiney9

Hey Mike good to see you posting occasionally again. I wouldn't use those 6DJ8's, you will do damage eventually. They are not compatible despite what the Russian tube sellers say. The thing with ECC85/6AQ8's is no matter what the brand label says, it's all about the tube codes because there are only a handful of tube companies that made them for everyone. I have just about every iteration including some really old Valvo Hamburg tubes.

These are still popular because they were used for tuning duties in the old tube tuners, but they aren't near as pricey as something like a 12AX7, etc.

I need to go back through my stash to get my facts straight, so give me sometime and I can make some recommendations and I may even have a spare pair of something for you at a good price.

I just pulled this little workhorse out again the other day and man do I love it for what it is. Different tubes make it sing. As far as the noise issue, I don't use headphones, but through the speaker outputs it's dead quiet. If I had to guess it's the tubes that are causing the noise.

Stay tuned

H9

BlueMDPicker

Hi Brock!

Thanks for the info and effort. I pulled the 6DJ8's out and stuck the Chinese 6N1's back in. Man, they are terribly noisy! Can't help myself - I'm a noise ****.

I'm going to re-route all cables and stick it on a PS Audio conditioner for grins. But, I agree, the noise is most likely (crappy) tubes.

Mike

Nightfall

Tell me that doesn't look like it was made in the same place the Dared MC-7P was, down to the same power switch...

BlueMDPicker

Yeah, no question. The HTC was also marketed as a "FatMan" at 2x the price, IIRC.

heiney9

Dared licensed their MP-5 to a Korean company as well as those Fatman units you see. The "true" Dared MP-5's use 12AX7's and later versions have a USB input. IIRC the Fatman units uses 12AX7's too. The Fatman's were sold at Boutique type retailers for about twice the price.

For all intents and purposes they are the same units. From what I see you just have to change the heater current for the HCT's to use 12AX7's. But, the 6QA8's the HCT uses are cheaper and there are some really fine one's out there.

I even saw a guy that modified one of the inputs as an output and used it as a pre-amp. Not sure how it sounded, but he was convinced.

H9

BlueMDPicker

Results of cable relocation: no change in noise floor.

Results of powering from PS Audio Duet: sounds more like a ground loop now.

Results of lifting the ground: DEAD black quiet!! (even with the Crapese tubes)

Still interested in some tube rolling suggestions, Brock. This little guy is a keeper!

Mike

heiney9

Here is a Dared MP-5. You can see the USB input just right of the power switch. This left only one rca input on the back.

Nightfall

Hey it's got one of those neat-o tubes that dances to the music.

Crazy how many products are out there that are just rebranded under a different name.

Glad you got it sounding nice Blue Picker.

BlueMDPicker

heiney9 wrote: »

Here is a Dared MP-5. You can see the USB input just right of the power switch. This left only one rca input on the back.

So, the Dared has an onboard DAC and output from that goes through the tube preamp section, then on to a solid state output stage?

heiney9

That's how I understand it. Not sure how good the dac is implemented, but I bet it's not bad. Atleast for the standard of the day which was about 5-7 years ago?

pitdogg2

Brock get's around:)

http://www.audioasylum.com/cgi/vt.mpl?f=tubes&m=245140&VT=T

I always like googling tube substitutes just to see and walla up comes Brock with the same advice

heiney9

Right now I am running a pair of Sylvania (made in the USA) black plates w/round getter from the 60's.

Another favorite is the Telefunken ECC85 and the Siemens ECC85.

I have 3 RCA labeled pairs and each is from a different manufacturer. Siemens, Blackburn (Mullard) and Heerlen (Holland).

The Euro tube code for ECC85 is tUx (x= change code; p being the absolute earliest mid 50's and pretty rare. tU1 is late 50's and the most common are tU2-tU7)

2nd line of code is where it was manufactured and the date. B = Mullard Blackburn; equal sign with a line through is Siemens, Munich Germany, right triangle is Heerlen Holland and D = Valvo Hamburg Germany.

I know this is a hassle, but any brand can be on any of the above manufactured tubes. So if you really want to know what you are buying look at the code. The great thing is they all sound great.

I do have an extra pair of ANOS Siemens labeled Tungsram ECC85's if your interested Mike. I bought them back in 2009 and they don't have a lot of hours on them. PM me if you're interested.

H9

BlueMDPicker

Rocking some classic Bo Diddly courtesy of the Siemens tubes Brock hooked me up with. Astounding difference in SQ across the spectrum. Thanks again, @heiney9 !

The single driver Abbys can really make some great, articulate bass when properly driven. Love it!