Prototype 125 watt monoblock tube amplifier KIT

Hi Bob:
What are the specs on that transformer? What voltages does it have output, bias etc.

Oh yes! Can we buy them soon?

Hi Bob

I assume to get that kind of power output, you'd be looking at running 4 X KT88 in a PP configuration (per monoblock)? I admit to being very curious and even more so VERY interested - that would be serious fun building it (assuming you'd have it available as a kit).

The power levels would right up there ("Oh-my-gawd-I'm-calling-the-police")...

-- JunkyJan

Bob,

Very interested in your 125-150 watt monoblock effort. My 4 ohm floorstanders go from 20-400 watts of power handling capability. Had been considering the ST120 but your new effort seems more suitable to my needs.

Bob, I think it might be interesting just to buy the parts off of you for the mono blocks and do your own chasis.I have had some ideas for a chasis for a while and I think this would be the proper platform to do them. Almost the same is Jim McShane and the pre-amps he will be offering up when he gets the r&d done on them.They will come with no chasis, kit form to keep the cost down.

always,thank you
pete

Bob,

Any update on the status of this project?

Nice can't wait to see this project come together

Hi,

I found some minor "glitches" in the translation of what I wanted as to spacing of certain parts on the chassis. The IEC connector is too close to one of the mount screws for the power transformer. On this prototype it's no real problem because I will just shorten the screw about 1/4 inch and it will go in there fine. The IEC connector will have to be moved 1/4 inch toward the fuse post and the fuse post will be moved 1/8 further towards the input jack.

Also, the four holes that mount the SCM, main grounding tabs, 3 lug and two lug terminal strip were too small. I told them that I wanted a hole for a 4-40 screw. What they gave me was 4 holes that could be TAPPED for a 4-40 screw. I just drilled the 4 holes out. They also got one dimension wrong by 3/8 of an inch. The triode/pentode switch is too close to the mount screw for the SCM module. It will be moved 3/8 of an inch towards the two lug terminal strip. On production models a heavier duty DPDT triode/pentode ultralinear switch will be used. On production models a 15 amp rated SPST ON/OFF switch will be used. I just used some smaller switches I had around the shop here on the prototypes.

Photo below of progress so far. I will be able to work more on the amp next week because the project that I was going to help someone with has been postponed.

Bob

Hi Bob:
The new project looks like it is coming along quickly. I noticed you are sticking with the quad cap on this one. Is there a particular reason you are doing so?
I would think that a board with the option of modifications and swapping out better caps would have been the call. Got any other specs for that thing yet?
I hope to see the completed project soon. Will it be a kit or a complete amp?
a very curious
Baddog1946

Hi Bob

I wonder will this amp be optimized for the kt-120's or will this be like the st-120 using the kt-120.
That's a lot of 120's in that sentience.

Hi Bob:
Good points, sounds like the can quad will do the trick and the rest is looking like I may have to start saving some dough for a pair of these.
What do you think the R&I period will be? Are you using a modified VTA board on this amp? Will there be a cage for it? Is it the same dimensions as the MK III?
Finally and I know I ask a lot of questions but got any idea of what a pair would be worth?
Baddog1946







7D

Hi Bob:
Well my ST-120 has been running fine since the Weber blew up I have checked it over internally and everything tests within normal tolerances. But I was wondering about something else. I live in a hot place (at the beach in Costa Rica) and I use my amp at least 4-8 hours a day here. It seems to be running fine but the main power trannie is always pretty hot.
I mean too hot to leave your hand on for more than a second or two. My question is are the trannies you had made for the mono block project for sale? Would they swap into my 120? At least the main. Do you think it would run a little cooler? Or at least not be running as hard? I play a lot of jazz, blues and a bit of the rock and roll but not at extreme volumes the thing is I use it a lot so it is on a long time every day.
Those trannies are a little more robust. The main thing might be they look a little bigger which might crowd the other two but if it can fit and it could give a little insurance then it might be worth it to me. Our average temp here in the rainy season is 80 degrees.
I am running some Decware NFX's I built with 99dB sensitivity which by the way are some of the best speakers I have ever heard in my 40 year audiophile career they have unbelievable detail and they actually have some decent bass although I have a small sub as well.
Which brings me to another question; what would I have to do to swap my VTA high gain board to a low gain board?
I have a stepped attenuator on the amp but often I have to turn it down to 2-3 or it has too much volume and one click makes a huge difference.
Thanks for listening
Baddog1946

Small suggestion:

Can the VTA board be mounted the other way around to allow the bias adjustment posts to be toward the front of the amp? I keep my amps in a rack, and reaching over hot tubes to reach the 'blind spot' pots would not be my first choice.

Just a minor suggestion.

Hi Bob:
quick question, is the main transformer the same as the 120 or is it a custom built as well?
Baddog1946