Sharing my experience on Ceriatone HRM...

[massygt6]

Hi,
happened that I had the chance to buy an HRM Ceriatone kit from a guy that can't complete it anymore, for a very low price...
I've now completed the amp and had the time to make some refinements.
The first HUGE improvement was to swap the OT with a different one, built by a very capable guy that has a little activity as a amp builder...no 16ohm tap, just 4 and 8 ohm, a well engineered design and excellent materials.
The choke is now a 105ohm 200mA 10H.
The PT is built to obtain a B+ settled on the "low side"...I'm currently running the amp at 405-410 volts on the power tubes, and on the preamp tubes anodes I've 180 volts + or -.
The first two 220uF caps are replaced with Fischer and Tausche, but I'd like to try some Mallory TC in it.
The slope resistor on the HRM board is now 47k, while the bass cap on the PRE OD tonestack has been reduced to 1/2 the original value.
NO LOCAL FEEDBACK on V1, as it should be...I've some doubts on the OD trimmer configuration...a 100k resistor into a 250k trimmer and a fine tuning 25k trimmer...the 250k trimmer seems to do nothing, while the 25k trimmer have the expected impact on the OD channel...any advice?
However, the amp is smooth and creamy, "brownish", the OD in PAB mode is very tight and aggressive with significatives amounts of gain and spaces from blues to hard rock.
The clean channel is decent, not so brilliant and emotional as the Special version, but very usable and a bit sterile.
The OD is the strong point of this amp, you can do almost everything with it.

[Structo]

Thanks for the review.

[briane]

The PT is built to obtain a B+ settled on the "low side"...I'm currently running the amp at 405-410

Have you settled on that through trial and error?

I ask, cause I found these amps IMO dont perform at full force if you running less than about 440 volts...And the general consensus at AP is hotter is better.

Not to say that suits your taste.

If your wondering about the HRM configuration, the schematic for ods-101 HRM has the details. it should be followed explicitly in my experience to obtain the best results.

[massygt6]

The PT is built to obtain a B+ settled on the "low side"...I'm currently running the amp at 405-410

Have you settled on that through trial and error?

I ask, cause I found these amps IMO dont perform at full force if you running less than about 440 volts...And the general consensus at AP is hotter is better.

Not to say that suits your taste.

If your wondering about the HRM configuration, the schematic for ods-101 HRM has the details. it should be followed explicitly in my experience to obtain the best results.

I had a Special before that one, and the B+ was about 480v(custom OT and PT not the stock one), it was clean to death, had a Twin vibe in it, but also a bit fuzzy in the OD channel and I struggled a lot to make it smoother...For this one I decided to try the "low side".
Maybe 20 volts more on the HRM would put me in the ballpark, but as it is now, the amp is very good, has plenty of volume on both channels and has a lot of clean headroom.

[briane]

Hey if it works for you thats all that matters.

Thats whats so cool about the customization aspect.

[massygt6]

Thats whats so cool about the customization aspect.

Damn right