My First 100W HRM (with clips)

[ik6gpy]

Hi,
this is my first post on this wonderful forum and i thank you all because i've learned a lot from this community and made this possible. After a simple Ax84 i've decided to build this monster.

Here are the specs of my amp: It's a very slightly modified Ods-101 HRM 100W skyline eq built on a ceriatone chassis with my own faceplates and head cab (which still need metal angles and a leather handle) with the following components:

Heyboer Mojotone Twin Reverb Irons
Holco H4 mil spec 0,25% metal film resistors (those are as rare as incredible sounding!)
Xicon MPP signal caps
Illinoise Caps (220uF range), Roederstein Caps (47uF range) and Sprague Atom Filter Caps (100uf range)
Mundorf Bipolar bypass caps

Bright switch on a push pull pot (clean vol), Deep, Jazz/Rock and Mid Boost on toggle switches.
I've got 170V on V1a plate (isn't it a bit low?), 188V on v1b, 200V on V2, 277 on the PI and 440V on the 6L6 Plates (biased @ 32mA).
The Fet circuit is temporarily unused as i'm still waiting for the proper switchcraft jack.

Bla bla bla bla...

It sounds incredible and it's dead quiet!
I play it through a Thiele 1x12 Cab that i made, with an EVM speaker.

Good night from Italy
Matteo

[odourboy]

Welcome to the forum. Nice first build!

Ceriatone chassis and board set?

[tubedogsmith]

Very nice work. I would think an amp full of those Xicon signal caps would be quite "bright".

[Bob-I]

Very nice work. I would think an amp full of those Xicon signal caps would be quite "bright".

I've tested these against a bunch of caps, they're no brighter and sound smooth and creamy.

Excellent build. The plate load resistors look great.

[CHIP]

That's nice work.

[Bob-I]

That's nice work. Alpha pots?

What was your first clue? the big ALPHA stamped into the back of the pots?



Yes, they all look like Alpha's

[CHIP]

[massygt6]

Hi Matteo,
bel lavoro, good work, how's the sound of this baby?
170V is a bit on the lowside, most of the amps here are in the 185-190v ballpark, but if it's good for you, no need to tweak it.
Massimiliano

[ik6gpy]

Thanks everybody!

Yes, Ceriatone chassis and board set.
It's not bright at all, it's very smooth, full of overtones and very very touch sensitive. I'm very happy with the sound. Cleans are also great.

I use a Madza Ecc83 from 1960 made in Blackburn in V1 (incredibly good sounding tube), Ei Jugo in V2 and PI (great tubes but there are a lot of microphonics issues with this ones). 6L6GC's are from Tube amp doctor.

170V on V1a is a bit strange, as all the other voltages are pretty much in spot, maybe could be the Mazda that drains some more current than the other ones... I have to try some other brands and see what append.
Fet resistor is a 150K, could i try 220K to push up the voltage a bit?

[sergio]

Hi , welcome to the forum , well done , nice build!.
Bravo Matteo , compliments.
Ciao Sergio

[Structo]

Nice clean build!

Can you explain the use of the small poly caps in parallel with the bypass caps on the preamp?

[ik6gpy]

Nice clean build!

Can you explain the use of the small poly caps in parallel with the bypass caps on the preamp?

Thanks!

The small 0,33uF Panasonic Ecq are there just to reach the 5uF on the schematic as the Mundorf are 4.7uF. I just wanted to experiment and ear how they sound. Obviously the difference is barely noticeable.

[M Fowler]

Very nicely done, going from an Ax84 right into a build like this, wow!

Mark

[David Root]

Nice work indeed!

Mazda made in Blackburn must be a Mullard rebranded Mazda? Or maybe Mazda tubes were made in England at one time as one company ended up owning most of the West European factories.

As to the 170V on V1a, that is quite believable. I have a Mazda (France) in V1 in my 50W '70s ODS and it dropped a good 10V compared with a Telefunken, but in both triodes.

You seem to have two dissimilar triodes as you are getting 188V in V1b. Unless you have a dropping resistor in the power supply between V1b and V1a?

[LPSGME]

170V on V1a is a bit strange, as all the other voltages are pretty much in spot, maybe could be the Mazda that drains some more current than the other ones... I have to try some other brands and see what append.

If not the tube itself, a mismatch between the plate and cathode resistor can easily alter the plate voltage. I had such a disparity and was absolutely sure I had the right cathode resistor value in place - but DUH!, I didn't.

So even if their labels show the correct value, you might want to go so far as to measure them to be sure.