Blackstar HT-5 Schematic?

[ehedwr]

Anyone know where I can get one?

[teemuk]

AFAIK, you can't. Blackstar doesn't give out schematics so your best bet is acquiring one from their certified service centers. Which might not want to share them either.

Under the hood has so far been the best option.

[Zozobra]

I see you've been busy over at fsb!

[guitarcapo]

I think they're keeping the schematic secret so that people won't figure out that it's actually a hybrid solid state/tube amp and not all tube. Not that there's anything wrong with that. The amp sounds great. It's just that you can charge more for an amp if people think it's "all-tube"

My guess is that it probably has a solid state phase inverter and most certainly uses solid state rectification. There's also probably some op amp chips along the signal path boosting and shaping things too.

I own this amp and love the high gain sounds. Makes way more sense to me compared to buying an expensive all-tube amp for the home and using an expensive attenuator with it to get the same sound (maybe worse) at home where the amp is getting use 90% of the time. Cheaper maintenance too. Just don't plan on modding one when you get it more than swapping out tubes. It's ain't that kind of amp.

[teemuk]

Judging by the gut shots, the phase inverter is indeed SS. If the design is anything like in HT series of pedals (like they claim it is) there's actually quite a lot of solid-state amplification and signal shaping in there. If you ever seen insides of this thing it's pretty evident. There is also a solid-state diode soft clipping gain stage on each channel preceding the tube gain stage(s). Cab sim is a bunch of solid-state active filtering circuits too. etc.

I think they didn't have to use switched mode power supply in this one like they did in the HT pedals. Looks like an ordinary linear supply.

I can make a schematic out of this thing if people can provide me high quality, detailed gut shots of both sides of the PC boards (something from which I can see component values and see the PCB traces) as well as some overall shots of the internal wiring to tube sockets and switches.

Also, if you are swift enough to work on PC-boarded amps you can mod this thing like any other solid-state amp. Modding has never been exclusive to all-tube amps. The mods may not be similar as in tube amps (e.g. change cathody bypass cap) but they are perfectly sensible for anyone familiar with basic OpAmp and analog circuits.

[guitarcapo]

Originally Posted by teemuk

Judging by the gut shots, the phase inverter is indeed SS. If the design is anything like in HT series of pedals (like they claim it is) there's actually quite a lot of solid-state amplification and signal shaping in there. If you ever seen insides of this thing it's pretty evident. There is also a solid-state diode soft clipping gain stage on each channel preceding the tube gain stage(s). Cab sim is a bunch of solid-state active filtering circuits too. etc.

I think they didn't have to use switched mode power supply in this one like they did in the HT pedals. Looks like an ordinary linear supply.

I can make a schematic out of this thing if people can provide me high quality, detailed gut shots of both sides of the PC boards (something from which I can see component values and see the PCB traces) as well as some overall shots of the internal wiring to tube sockets and switches.

Also, if you are swift enough to work on PC-boarded amps you can mod this thing like any other solid-state amp. Modding has never been exclusive to all-tube amps. The mods may not be similar as in tube amps (e.g. change cathody bypass cap) but they are perfectly sensible for anyone familiar with basic OpAmp and analog circuits.

Yea it's just out of my league. Not just the problem of dealing with traces and PC boards...but the whole theory as to how you would mod it without a schematic. I think it sounds fantastic as it is as far as the voicing goes and I really can't think of a way to improve on the sound for what it is anyway.

My experience in modding amps is basically dealing with simple Fender amp circuits. Modifying the tone stack caps, changing the cathode bypass caps and resistors, treble bypass cap modding the controls, altering the negative feedback loop, altering the input resistor values, swapping out tubes and speakers, maybe substituting the rectifier for solid state, maybe also just following mod suggestions people have posted online or buying "mod kits" and trying them in amps I own.

I have an awesome sounding tweed Champ clone that I modded heavily. It actually has fantastic clean sounds now. I achieved it by trial and error modifying the cathode bypass caps and resistors at every gain stage and at the power tube, using a bypass cap at the volume pot, changing the input resistor at input 1, disconnecting the negative feedback loop, swapping out the speaker for 10" Weber. It's a one-of-a-kind amp now. Instead of just being a one-trick-pony that only sounds good with the volume on 12, it has great tone everywhere and goes from wonderful cleans to great overdrive. Takes pedals great too.

[teemuk]

Since people don’t seem to have too much interest in this I call it quits now. So, here are unfinished schematics of the HT-5, which should still be helpful for people needing to do some repairs or some other stuff. What are missing are all the rear PC board circuits (jack switching, FX loop amp, loop breaker etc.) and a bunch of component values and designators I simply couldn’t interpret from the few photos I had of the internals. Don’t be too sure to trust that the ones in the schematic are 100% accurate either. These schematics are compiled from gut shot photos just a single person cared to send me and that’s all I could work with. I'm not going to ruin my eyes guessing small details or colour codes out from a pixelated mess.

I now know practically all I wanted to know about this amp and it seems – considering the minimal interest - that due to these diagrams, you will now know as well. Hopefully.

I can consider updating or finishing the schematics if I get pictures that help me do so.

[guitarcapo]

I'm really impressed that anyone could do that with an amp in front of them let alone from pictures.
I think all people really cared about was if there were a lot of diodes in the signal path...which there does seem to be.

[HKSblade1]

Stock up on those J175 fet's

[bdubbs]

Because i'm drinking how does it look like the power amp is done?

[musicdog400]

Wow good work. I don't get what those zener diodes are doing. I don't think they're for clipping. Think any of these are for clipping ?

[-Juggernaut-]

last pic isn't working..... "HT-5_preamp_pt_2.gif"


can I get it?

[fat-us]

WHAT THE !!! all that hype for a solid state amp?
They sell that thing as a tube amp !

[Chris.novak]

Originally Posted by fat-us

WHAT THE !!! all that hype for a solid state amp?
They sell that thing as a tube amp !

I knew as soon as I played one.

[teemuk]

Originally Posted by musicdog400

I don't get what those zener diodes are doing. I don't think they're for clipping. Think any of these are for clipping ?

The Zener diodes are indeed for clipping but only for the sake of protection, limiting the input signal below their zener voltager so that, for example, static voltage spikes can’t reverse bias the OpAmps and damage them. In normal operating conditions input signal's amplitude isn't high enough to exceed the zener voltage and cause clipping. D29 and D30 are a similar protection but instead of zener voltage, the signal voltage must exceed forward voltage of the diode + the corresponding supply rail voltage.

Diodes D26 and D27 are for ordinary signal clipping.